Field of the invention

This invention relates to cables, interconnect systems and methods for the transmission of signals, e.g. such as data and/or power, between electronic components. The invention is useful, for example, in situations where it is required to transmit both data and power.

Background of the invention

In complex devices comprising a plurality of electronic components, e.g. processors, electronic control systems and peripheral electronic devices, the separate electronic components may of necessity be distributed around the overall device and thus separated in space. Interconnection of the electronic components for both power and data supply is thus required and is typically provided by an interconnect system comprising a plurality of wires. By way of example only, the interconnect system of a typical analytical instrument, such as a spectrometer, is described in more detail below to understand further some of the problems addressed by the invention. However, the invention is not limited to application in a device which is an analytical instrument and may have application in any complex device comprising a plurality of electronic components requiring an interconnect system.

A typical analytical instrument comprises an electronic control system, generally implemented on one or more printed circuit boards (PCBs), with electrical interconnections typically required between the electronic control system (e.g. the one or more PCBs) and one or more peripheral electronic devices such as, for example, sensors (e.g. temperature, pressure, voltage, chemical, radiation and/or light sensors etc.) and/or actuators (e.g. displays, pumps, and/or valves etc.). Even if the number of separate electronic components is kept to a minimum and as much of the electronics as possible is contained on a central PCB, there invariably remains an interconnect system comprising a complex wiring loom, also referred to as a cableform, inside the instrument in order to make the necessary interconnections between the various electronic components. The interconnections typically have to handle a number of different types of signal, for example selected from electrical, optical, power (e.g. at different voltages), data, analogue, digital, high frequency etc and therefore may comprise a diversity of connectors and wires.

During the life of an analytical instrument, it is typically necessary to replace one or more of the peripheral devices and often the replacement is not identical to the original device but a new one, e.g. due to component obsolescence, cost reduction, performance improvement etc. If the electrical interface between the replacement and the electronic control system is identical to the original then no change is required to the existing interconnect system (e.g. wiring) or electronic control system. However, if the electrical interface differs, as is often the case, then a change is required to the interconnect system and/or the electronic control system (i.e. the one or more PCBs thereof).

Common cable types within cableforms for transmitting signals include optical fibres and coaxial cables. In the prior art it has been known to integrate optical fibres and coaxial cables, which reduces the overall number of cables to be handled. Conventional coaxial cables comprise an inner conductor usually in the form of a wire, an insulating layer surrounding the inner conductor along the length of the inner conductor and an outer conductor or electrical shielding surrounding the insulating layer along the length of the cable, with a plastic sheath typically covering the outer conductor. Particular designs for integrated optical and coaxial cables have included supporting optical fibres within longitudinal grooves on the outer surface of a spacer surrounding the insulator part of the coaxial cable (JP 1 -144516A and JP 2008-003099A), positioning the optical fibre between the inner conductor and the outer conductor or shielding (CN 2563717 Y, US 4,695, 127), carrying the optical fibre within a hollow tubular inner conductor (CN 2401976 Y, US 4,896,939, US 5,557,698, US 5,539,851 , US 5,672,079, WO 94/22039, DE 4429022 A1 and DE 4436342 A1 ), locating the optical fibre within the insulating layer (CN 2409585 Y and GB 15891 15), placing the optical fibre onto the outer plastic sheath or outside the outer conductor (CN 2401975 Y and US 5,418,878). However, whilst the total number of cables to be handled may be reduced to a degree by these integrated cable designs, the designs are rather complex and/or costly. Moreover, the designs have not addressed other signal types, e.g. power.

In view of the above it is desirable to provide an improved interconnect system. It is desirable, for example, to reduce the complexity of the cableform inside the device and/or the diversity of cables and connectors. It is additionally desirable to provide an improved interconnect system for the transmission of both power and data. It is also desirable, for example, to facilitate a simple replacement of peripheral devices, especially where the replacement differs from the original peripheral device, e.g. to avoid changing the wiring and/or PCB of the electronic control system. It is further desirable, for example, to reduce the incidence of errors in the assembly of the interconnect system during manufacture and/or maintenance.

Summary of the invention

According to a first aspect of the present invention there is provided a cable for the transmission of power and/or data signals having a first conductor, a second conductor and an optically transparent insulating layer separating the first conductor and second conductor wherein the insulating layer is operable as an optical waveguide for the optical transmission of power and/or data signals along the cable.

According to another aspect of the present invention there is provided a method of transmitting power and/or data signals comprising:

providing a cable according to the first aspect of the invention;

electrically transmitting power and/or data signals along the length of the cable via the first conductor; and optically transmitting power and/or data signals along the length of the cable via the insulating layer.

The invention further provides an interconnect system for connecting two or more electronic components wherein each electronic component has a connection for transmitting and/or receiving power and/or data signals via a cable according to the present invention, the interconnect system comprising a cable according to the present invention for connecting to the connections of the electronic components.

It can be seen that the invention provides a single cable able to transmit both power (e.g. via the first conductor) and data (e.g. as an optical signal via the insulating layer), or just one of these, most preferably to transmit power and bidirectional data at the same time, using a simple cable construction.

The cable of the invention is suitable, for example, for connecting two or more electronic components, e.g. two or more electronic components of an electronic system. Herein the term electronic system is used to mean an electronic system or device having two or more interconnected electronic components. The term component herein refers to components or subsystems. The components are to be connected for the transmission of signals therebetween. For example, one end of the cable in use may be connected to one component and the other end of the cable to another component. One or more of the components of the electronic system to be connected may be an electronic control system. One or more of the components of the electronic system to be connected may be a peripheral electronic device. The electronic system may be an analytical instrument, such as a spectrometer for example, or may be another electronic device. The invention, therefore, is not limited to the example of an analytical instrument. One example of a spectrometer would be an iCAP ICP optical emission spectrometer from Thermo Fisher Scientific but clearly any spectrometer requiring communication of power and/or data signals between electronic components could benefit from the application of the present invention. An analytical instrument for example, typically comprises an electronic control system (also termed herein instrument control electronics), usually implemented on one or more printed circuit boards (PCBs), which may constitute one of the electronic components to be connected. The other or others of the electronic components to be connected e.g. to the electronic control system, may comprise one or more peripheral electronic devices such as, for example, sensors (e.g. temperature, pressure, voltage, chemical, radiation and/or light sensors etc.) and/or actuators (e.g. displays, pumps, and/or valves etc.). The one or more peripheral electronic devices may comprise one or more passive electronic devices (i.e. which do not contain their own control electronics) and/or one or more active electronic devices (i.e. which do not contain their own control electronics).

The invention advantageously reduces the complexity of a cableform inside an electronic system such as an instrument since at least two conduits (i.e. a first conductor and an optical channel) for power and/or data are provided within one cable. Moreover, the diversity of connectors used with the cableform may also be reduced. The cable uses a simple construction of at least two conductors and an insulating layer between them, e.g. it may be formed like a conventional coaxial cable but provides an additional channel for signal transmission by adapting the intermediate insulating layer to act as an optical waveguide. Thus, similar construction methods to, for example, conventional coaxial cables may be employed to make the cable. Simplified cable construction is thus also an advantage of the invention.

The present invention can facilitate the simple replacement of electronic components such as peripheral devices, especially if cables according to the present invention are used as standard for all power and/or data connections between components, e.g. between an electronic control system and its peripheral devices. Furthermore, the invention reduces the likelihood of accidental errors occurring in the assembly of the interconnections between components during manufacture and maintenance due to the simplified nature of the cabling including the reduced number of cables and connections required. Further advantages will be become apparent from the description below.

The cable comprises at least first and second conductors but in some embodiments may comprise more than two conductors. The first conductor preferably extends along the length of the cable, i.e. is elongate in the longitudinal direction of the cable. Preferably, the first conductor comprises a wire, preferably a solid wire. The first conductor is preferably metallic, e.g. copper.

Preferably, the first conductor is for conducting power and/or data signals but more preferably is for conducting power (i.e. electrical power in the form of current), more preferably DC power.

Preferably, the first conductor is surrounded by the insulating layer (e.g. annularly surrounded by it). More preferably, the first conductor is embedded within the insulating layer. Further preferably, the first conductor is co-axially arranged with the insulating layer, with the insulating layer annularly surrounding the first conductor.

The first conductor most preferably is positioned as an inner conductor, especially as an inner conductor of a co-axial cable. In such embodiments, the insulating layer preferably surrounds the inner conductor (i.e. annularly surrounds it). The inner conductor is most preferably in the form of a central wire in such cases. In such embodiments, the second conductor preferably surrounds the insulating layer (i.e. annularly surrounds the insulating layer). Further preferably, the first conductor is co-axially arranged with the insulating layer and the second conductor, with the insulating layer annularly surrounding the first conductor and the second conductor annularly surrounding the insulating layer. The first conductor is thus electrically shielded by the second conductor, the second conductor preferably being earthed in such cases. It will be appreciated that such a cable thereby resembles a conventional co-axial cable but has the insulating layer operable as an optical waveguide for optical signal transmission, i.e. the insulating layer is arranged to receive and transmit an optical signal.

The second conductor preferably extends along the length of the cable, i.e. is elongate in the longitudinal direction of the cable. The second conductor may be a solid wire or a tubular conductor. Preferably, the second conductor comprises a tubular conductor. The second conductor is preferably metallic, e.g. copper. The tubular conductor may comprise a braided metal, e.g. braided copper. The first and especially second conductors are preferably metallic for conduction properties but also for acting as reflective surfaces bounding the surfaces of the insulating layer located between them, which thereby contains the optical signals within the insulting layer and helps the guidance of optical signals through the insulating layer. The surface of the first and/or second conductor which faces the insulating layer may be additionally mirrored or silvered, e.g. with an enhanced reflective coating, e.g. such as silver, to enhance its reflective properties (reflectivity). Enhancing the reflective properties of the conductors may be more important the longer the cable length.

The second conductor may be earthed to act as shielding, e.g. shielding of the inner conductor as it transmits power and/or data. The second conductor may carry power or a data signal, preferably power, but is more preferably earthed in the power circuit. The second conductor may transmit the current return for the electrical power from the connected electronic device where the first conductor transmits electrical power to it. The power transmission is preferably DC power transmission and the power transmitted by the first conductor is thus preferably DC and the second conductor is the ground.

As mentioned, in other (non-coaxial) embodiments, the first conductor and the second conductor may each comprise a solid wire. The first conductor and the second conductor may be, e.g., positioned a distance apart (i.e. in a transverse direction to the longitudinal direction of the cable) in a side-by-side relationship within the cable, with the insulating layer at least filling the space between the first conductor and the second conductor thereby to separate them. The first conductor and the second conductor may each be embedded within the insulating layer, e.g. in the side-by-side relationship.

Preferably, however, the second conductor is an outer conductor which is a tubular shaped conductor annularly surrounding the first conductor which is thus an inner conductor, more preferably in a coaxial relationship. In this type of coaxial embodiment, the insulating layer is preferably an annular layer disposed between the first and second conductors, i.e. the insulating layer preferably occupies or fills the annular space between the first and second conductors.

In preferred embodiments, at least one conductor, most preferably the inner conductor in a coaxial embodiment, may be a carrier for power or data signals, more preferably power. In a coaxial embodiment an outer conductor of the cable may be connected to the ground of the power circuit, e.g. in the case of DC power supply. In some other embodiments, each conductor may be a carrier for power or data signals, preferably power.

As mentioned above, the cable is not limited to having two conductors, e.g. the cable may have a third conductor and so on, e.g. another conductor for carrying power and/or data and/or for shielding. For example, a third conductor and so on may be another inner conductor annularly surrounded by the tubular second conductor as mentioned (e.g. to provide two inner conductors surrounded by a tubular outer conductor). In another example, a third conductor and so on may be another tubular conductor annularly surrounding the first and second conductors, e.g. in a triaxial arrangement. In such embodiments with more than two conductors, for example two or more power signals, which may be the same or different, may be independently carried through the cable by different conductors. A pair of conductors is typically used to transmit/return each power voltage, wherein one of the pair may be at ground.

The cable is preferably for transmission of power and/or data, preferably both power and data. Preferably, at least the first conductor is for transmission of power, i.e. electrical transmission of power. Preferably, the optically transparent insulating layer is for optical transmission of data, preferably bidirectional optical transmission of data.

Most preferably, the cable is a coaxial cable, as described above, wherein the first conductor is an inner conductor, the insulating layer annularly surrounds the first conductor and the second conductor is a tubular conductor which annularly surrounds the insulating layer (i.e. the second conductor is an outer conductor). In such embodiments, the second or outer conductor is typically encased in a sheath, e.g. a plastic sheath, for external insulation and/or protection.

The insulating layer is preferably elongate and extends along the length of the cable (i.e. in the longitudinal direction).

The insulating layer preferably separates the first conductor and second conductor and substantially fills the space between the first conductor and second conductor. Preferably the insulating layer annularly surrounds at least the first conductor. In the most preferred embodiment wherein the cable is a coaxial cable, the insulating layer annularly surrounds the first conductor with the second conductor being a tubular conductor which annularly surrounds the insulating layer.

The insulating layer may fill the space between the first conductor and the second conductor. The insulating layer may additionally fill space around each of the first conductor and the second conductor to insulate the conductors with respect to surroundings, e.g. where the first conductor and the second conductor are embedded within the insulating layer. In such embodiments, the insulating layer preferably has a non-transparent sheath surrounding it which thereby provides an outer surface around the insulating layer to reflect light waves and contain them within the insulating layer. The preferred coaxial embodiment has the second conductor to act as the outer surface around the insulating layer to reflect light waves and contain them within the insulating layer. Therefore, the insulating layer is preferably surrounded by at least an outer layer (outer reflective surface) which reflects light to contain light within the insulting layer, which outer layer may be e.g. the tubular second conductor in a coaxial embodiment or an additional non- transparent outer sheath in other embodiments. The insulating layer is preferably further bounded at an inner surface of the insulating layer by at least an inner layer (inner reflective surface) which reflects light to contain light within the insulting layer, which inner layer may be e.g. the inner conductor in the coaxial embodiment.

The insulating layer preferably comprises a fibre optic material e.g. polymethylmethacrylate and/or other known materials. The outer reflective surface (e.g. second conductor where it is an outer conductor surrounding the insulating layer, or another non-transparent layer surrounding the insulating layer) preferably acts to reflect the light back into the insulating layer so that the refractive index of the insulator in such a case is not especially important provided it is optically transparent. This is one option for the cable, preferably where the insulating layer is homogeneous and surrounded by the outer conductor. If the outer conductor has a reflective surface, this helps to generate the necessary internal reflections so that light will travel along the cable. Another option for the cable is to have the insulating layer comprise at least two layers, in a stepped or graded index configuration (i.e. with different refractive indexes in each layer). Preferably a simple arrangement of the insulating layer may be used comprising two layers in a stepped index configuration. In this case the difference between the two (or more where more than two layers are used) refractive indexes keeps the light inside the insulator. The reflectivity of the outer conductor in that case is not important. In either option, the optical quality of the transparent insulator is less critical than that of conventional optical fibres. The reason is that cables according to the present invention are intended to be of relatively short length (e.g. 1 metre or less) whereas conventional optical fibres transmit data over kilometre distances. The material of the insulating layer also needs to meet the flexibility requirements of the environment in which it will be used. The cable length inside, e.g., an analytical instrument may be, for example, of the order of several metres or less, e.g. one metre or less. In such cases the requirements on parameters such as optical signal attenuation will be relaxed compared to conventional optical fibres which transmit data over long distances.

Conventional coaxial cable insulators which surround the inner conductor may be made from solid plastics or foam plastics material. The properties of the insulator control electrical properties of the cable, i.e. a key parameter is the characteristic impedance of the cable at the required operating frequency due to the conventional cables carrying high frequency signals. However, this is not important in the present invention because the conductors are not typically for transmitting high frequency electrical signals down the cable. In the present invention, the only important electrical property is that the insulating layer is an electrical insulator to separate the two or more conductors.

The cable length inside, e.g., an analytical instrument is comparatively much shorter in comparison to optical fibres used for telecommunications. The cable length inside an instrument may be, for example, of the order of several metres or less, e.g. one metre or less, such as 0.25 to 1 .00 metre.

The insulating layer is operable as a waveguide for light waves which carry signals, especially data signals.

Preferably, it is data which is optically transmitted via the insulating layer. Power may be optically transmitted but the capacity for power transmission in this way is low (e.g. on the scale of microwatts). Optical data signals are preferably transmitted bi-directionally through the insulating layer, e.g. to enable controlling data to be sent to a peripheral device from an electronic control system and data to be sent back to the electronic control system from the peripheral device.

The optical signal carrying data may be analogue or digital, preferably digital. Data could be transferred in an analogue fashion by modulating the amplitude of an LED output, e.g. the brightness of the LED output could be modulated such that it is proportional to the amplitude of the analogue signal that is to be transmitted. However, transmitting the data digitally (e.g. from the output of an A/D converter) is preferable. On/off keying may be used to transmit the data. The wavelength of the optical signal is preferably in the visible range (e.g. 400 to 600 nanometres (nm), or 400 to 700 nm) or infrared range (e.g. 600 nm or more, or 700 nm or more). Suitable cost effective LED light transmitters and photodiodes for example exist to emit and detect in these ranges. The speed of data transmission using the cable may be 1 or more megabits/second (Mbits/s) or tens of Mbit/s, i.e. a similar speed to communication systems such as USB.

The cable is preferably to be connected between electronic components using connectors or connections on the terminals (ends) of the cable and connectors or connections on the components, i.e. the cable connects to the components by connecting its connectors or connections to the connectors or connections on the components. The cable connections preferably comprise a power connection and an optical connection, i.e. they are preferably a power and data interface. The connectors or connections on the terminals of the cable are thus arranged for the transmission of an electrical power signal and an optical signal (preferably data signal) to and/or from the cable. The connection associated with each component of the interconnect system preferably comprises a power connection and an optical connection comprising one or more of an optical transmitter, an optical receiver and an optical transceiver (i.e. an optical transceiver comprising both an optical transmitter and an optical receiver). The component connection is thus a data and power supply interface. More preferably, the connection comprises a power connection and an optical transceiver, especially for bidirectional optical data transfer. The power connection is a connection for making electrical connection to the conductors of the cable, including the first conductor if that is the one to carry power to the components, e.g. the inner conductor in the coaxial embodiment. The optical transmitter, e.g. such as an LED or laser, is to provide an optical data signal into the insulating layer of the cable. The optical receiver, e.g. such as a photodiode, is to receive the optical data signal from the insulating layer of the cable. The transceiver is applicable in the embodiments utilising bidirectional optical data transmission. The optical transceiver preferably comprises a light transmitter, e.g. such as an LED or laser, to provide an optical data signal into the insulating layer and a light receiver, e.g. such as a photodiode, to receive the optical data signal from the insulating layer. The optical components (optical transmitter, optical receiver and/or optical transceiver) are preferably housed in the connector on the electronic component (e.g. socket or plug) which connects to the connector on the cable according to the invention (e.g. the complementary plug or socket). The optical components may, for example, be housed within a BNC connector socket or plug.

Preferably, in the interconnect system the first conductor is for connection to a power supply and the second conductor is for connection to ground and the insulating layer is for connection to one or more of an optical transmitter, an optical receiver and an optical transceiver. The interconnect system is preferably for connecting, e.g. in an analytical instrument, an electronic control system and a common voltage supply to one or more peripheral devices (e.g. such as sensors and/or actuators), each peripheral device incorporating its own local voltage regulator and/or local control electronics.

The ends of the cable are each preferably terminated by a connector, more preferably a connector making an electrical connection to the conductors and an optical connection to the insulating layer of the cable. The ends of the cable are more preferably terminated by a connector which makes electrical connections to first and second conductors and an optical connection to the insulating layer of the cable.

The cable connectors terminating the cable may be selected from a diversity of connector types, e.g. BNC, ferrule type, standard co-axial plug/socket, SMA or SMB connectors. Connectors preferably align the optical signal from an optical transmitter to the insulating layer of the cable and/or align the optical signal from the insulating layer of the cable to an optical receiver. The connectors on the components (to which the cable is to be connected) similarly comprise a complementary connector type to connect to the cable connectors terminating the cable, e.g. BNC where the cable connector is BNC etc.

In some embodiments, the electronic components may be connected directly by one coaxial cable according to the invention. In some other embodiments, the electronic components may be connected by two or more cables. The two or more cables may be connected in parallel or in series, e.g. in series via one or more optional intermediate joint or cable coupling devices. Such intermediate joints or couplings preferably maintain alignment of the optical signal from one cable to another. Detailed description of the invention

In order to more fully understand the invention it will now be described by way of non-limiting examples with reference to the accompanying Figures in which:

Figure 1 shows schematically a prior art architecture of an analytical instrument employing a complex cableform;

Figure 2 shows schematically an improved architecture of an analytical instrument;

Figures 3A and 3B show schematically the structure of a cable according to the present invention;

Figure 4 shows schematically a cross sectional view of the structure of a further embodiment of a cable according to the present invention;

Figure 5 shows schematically an interconnect system making use of a cable of the present invention; and

Figures 6 to 8 show embodiments of connectors suitable for connecting a cable according to the present invention to electronic components.

Referring to Figure 1 , there is shown schematically the architecture of an existing analytical instrument. A computer 2, which is a PC, controls the instrument overall and is connected to the instrument control electronics 6 via connection 4 which may comprise, e.g., a USB and/or Ethernet connection. The connection 4 may comprise one or more cables. The instrument control electronics 6 are typically implemented on one or more PCBs (not shown). The instrument control electronics 6 typically comprises a microprocessor or microcontroller for control of the instrument and interfacing to the PC. Typically, the control electronics 6 also comprise analogue interfacing circuits and power conversion circuits. An interconnect 8 comprising wiring sets 9 connects the instrument control electronics 6 to peripheral electronic devices 10, 12, 14 and 16. Each set of wiring 9 typically may comprise a plurality of individual wires, carrying different types of signals. The peripheral devices 10, 12, 14 and 16 typically comprise sensors or actuators. In the example, device 10 is a sensor (denoted as Sensor #1 ), device 12 is a sensor (denoted as Sensor #2), device 14 is an actuator (denoted as Actuator #1 ) and device 16 is an actuator (denoted as Actuator #2). The peripheral devices 10, 12, 14 and 16 may comprise complex components such as an RF generator or a camera module for example. Typically, one or more of the peripheral devices 10, 12, 14 and 16 are passive (i.e. do not contain their own control electronics). In the example shown in Figure 1 , device 10 (Sensor #1 ), device 14 (Actuator #1 ) and device 16 (Actuator #2) are passive devices. Other devices may be active and do contain their own control electronics, such as device 12 (Sensor #2) which has its own control electronics 13.

In the existing instrument architecture shown in Figure 1 , the electrical interfaces between the instrument control electronics 6 and the peripheral devices 10, 12, 14 and 16 are not standardized, so that each peripheral device needs to have its own set of power connections and lines and data signal connections and lines in order to function correctly. Accordingly, the interconnect 8 typically takes the form of a large and complex cableform carrying a variety of different signal types, including digital and analogue data and power. This complex cableform necessitates the use of numerous different connector types, e.g. such as BNC and multi-way connectors, to connect the wiring 9 to the various PCBs etc of the instrument control electronics 6 and to the peripheral devices 10, 12, 14 and 16. The cableform and its connections are thus bespoke for the particular instrument.

A problem with this design is that if one or more of the peripheral devices requires to be replaced with an alternative or newer device, e.g. due to an equipment upgrade or device obsolescence, then in many cases the cableform and/or one or PCBs of the instrument control electronics 6 has to be changed or replaced.

Another problem is that where the instrument has a plastic cover it provides no additional shielding of electrical emissions from the instrument so that, in addition to EMC measures that are required to be taken in each of the instrument components, care also has to be taken with the design of the cableform to prevent unwanted emissions from the cable runs. For example, EMC measures such as ferrites are often included in the cableform.

Referring to Figure 2 there is shown schematically an improved architecture of an analytical instrument which is particularly useful for implementing embodiments of the present invention though the present invention is not limited to use with such architectures. The basic layout is similar to the architecture shown in Figure 1 and, accordingly, like reference numerals refer to like components. In the Figure 2 embodiment, there are again shown four peripheral devices in this embodiment denoted as 20, 22, 24 and 26, wherein device 20 is a sensor (denoted as Sensor #1 ), device 22 is a sensor (denoted as Sensor #2), device 24 is an actuator (denoted as Actuator #1 ) and device 26 is an actuator (denoted as Actuator #2). The first significant difference from the Figure 1 architecture lies in the peripheral devices. In the improved architecture of Figure 2, peripheral devices 20, 22, 24 and 26 also each incorporate their own control electronics (local control electronics) 23 respectively. The peripheral devices 20, 22, 24 and 26 also each have their own voltage regulator (local voltage regulator), e.g. a switched mode supply, which is not shown in the Figure. Finally, the peripheral devices 20, 22, 24 and 26 also each have their own data and power supply interface 30 respectively. The data interface of each data and power supply interface 30 is preferably an optical serial digital interface (SDI) for the serial transfer of data. The peripheral devices may thus be regarded as "intelligent" peripheral devices in contrast to the peripheral devices illustrated in Figure 1 by virtue of having their own local control electronics and local voltage regulation The purpose of introducing these features into the peripheral devices 20, 22, 24 and 26 is to support a standardised interconnect 28 such as one which comprises cables 29, which are cables according to the present invention as described in more detail below. Preferably cables 29 are identical cables. The cables 29 connect to a plurality of identical connectors 21 , e.g. sockets, on the instrument control electronics 6.

The local control electronics 23 typically provide the local control and signal conditioning required for the normal operation of the peripheral devices. Typically, the sensors and actuators which constitute the peripheral devices 20, 22, 24 and 26, or at least a part of them, in use will be controlled by and/or will output analogue voltages or currents. In the embodiment shown in Figure 2, the local control electronics 23 will detect and/or generate such analogue voltages or currents and will perform any A/D and D/A conversions. Accordingly, the local control electronics 23 will typically comprise one or more A/D and/or D/A converters. This enables the data communications to and from the peripheral devices down the cables 29 to be digital. This system is therefore suitably designed for the optical transmission of digital data.

The local control electronics 23 also preferably interpret and/or execute commands that are sent from the instrument control electronics 6 to the peripheral devices. Typically, these commands from the instrument control electronics 6 are at a level such that the structure of the command is independent of the exact type of peripheral device, e.g. the exact type of sensor or actuator.

In the case of a temperature sensor as one of the peripheral devices, which will be used for illustration purposes, the sensor needs to be supplied with an accurately defined reference current for correct operation. The reference current is sensor-specific. In the prior art architecture of Figure 1 , the instrument control electronics 6 would generate the reference current and send this over the interconnect 8 to the sensor. The analogue data output signal from the sensor would likewise be transferred over the interconnect 8 back to the instrument control electronics where a A/D converter on a PCB would perform an A/D conversion on the signal. This means that both the interconnect and the instrument control electronics designs are dependent on the type of sensor connected. If an alternative type of temperature sensor has to be connected for some reason, which requires a different reference current then the generation of this current has to be changed on the instrument control electronics 6. If the new sensor, e.g., gives a differential output rather than a single ended output, then an extra connection has to be added to the interconnect and in addition the receiving amplifier on the instrument control electronics PCB would also have to be changed.

This problem is addressed by the improved architecture of Figure 2 since all the potential changes that would otherwise be required of the instrument control electronics 6 can be handled by changing only the local control electronics 23. Referring to the same example as above of a temperature sensor for comparison, in the Figure 2 architecture, the local control electronics 23 would be responsible for generating the reference current for the sensor. In this case, the instrument control electronics 6 does not need to supply the sensor specific reference voltage and does not need to be changed when upgrading the sensor. For the data output from the sensor, the analogue output signal can be processed, e.g. by scaling and converting it to digital, by the local control electronics 23 before sending it over the interconnect 28. The digitised data output signal from the local control electronics 23 can be converted to a serial format. The digitised data output signal can be pre-scaled, e.g. so that a value of "01 1 1 1 1 1 1 " represents a temperature of 100°C from the temperature sensor. Consequently, using the improved architecture of Figure 2, the peripheral device, such as the sensor, can be replaced without requiring either the interconnect 28 or the instrument control electronics 6 (either the PCB or embedded software) to be changed.

Within the improved instrument architecture of Figure 2, all of the data signals that are transferred between the instrument control electronics 6 and the peripheral devices 20, 22, 24 and 26 are digital. For example, any analogue data signals generated by the peripheral devices are digitised by an A/D converter in the local control electronics 23 of the peripheral device before transmission to the instrument control electronics 6. Within the peripheral device, preferably a serial data interface (SDI) converts the digital signals into a serial format using a defined protocol and transmits and/or receives the signals via the interconnect 28. Conversely, all command signals sent from the instrument control electronics 6 to the peripheral devices 20, 22, 24 and 26 are digital. The structure of the interconnect 28 is described in more detail below.

Another difference to the Figure 1 embodiment is that in the Figure 2 embodiment a common power supply 34, in this example a 24V supply, connected to the instrument control electronics 6 delivers a common voltage to each of the peripheral devices 20, 22, 24 and 26, i.e. as part of the output via each of the identical connectors 21 . Since each of the peripheral devices has its own local voltage regulator it can generate the voltage that it requires for its local control electronics from the common voltage. Of course, in some cases, if a particular peripheral device happens to use a voltage which is the same as the common supply voltage then it may not require a voltage regulator. In this way, the instrument control electronics 6 has only to generate a single power supply voltage that is common to all the peripheral devices. As with the local control electronics, this arrangement means that when an alternative peripheral device needs to be used (e.g. for cost, upgrade or obsolescence reasons) there is no need to change anything in the instrument control electronics relating to voltage supply since the new peripheral device can also have its own local voltage regulator. This is in contrast to the prior art instrument architecture of Figure 1 in which many of the precise supply voltages required by the peripheral devices are generated centrally by the instrument control electronics so that changing a peripheral device may also require change to the voltage supply within the instrument control electronics.

Since the improved instrument architecture of Figure 2 puts the various functions described above within the peripheral devices, the mechanism (i.e. protocol) for transferring data between the instrument control electronics and the peripheral devices can be the same for all peripheral devices.

The structure of the interconnect 28 is now described. The interconnect

28 lends itself for use with the above improved architecture of Figure 2, especially where the protocol for transferring data between the instrument control electronics and the peripheral devices is the same for all peripheral devices. However, it will be appreciated that the interconnect 28 and in particular the cables 29 according to the present invention are in no way limited to such uses and may be used with other instrument architectures and data transfer protocols.

As mentioned above, all of the data transferred between the instrument control electronics and the peripheral devices is digital, i.e. all of the data transferred by the interconnect 28 is digital. Typically, the interconnect 28 uses serial digital data transfer. The use of serial digital data transfer is sufficient for most analytical instruments and reduces the cable and connector costs. The same type of serial digital interface (SDI) is preferably used between the instrument control electronics and each of the peripheral devices. Thus, the same serial data protocol is used on each cable 29.

The interconnect 28 comprises a single supply voltage for each of its one or more power lines (e.g. power lines within cables 29 as described in more detail below), the single voltage coming from the common power supply 34 via identical connectors 21 . Since all the peripheral devices incorporate their own voltage regulators, power can be transferred to the peripheral devices at a single voltage level (such as 24V in this example). This has two main advantages: (i) it future-proofs the instrument control electronics 6 because any change in voltage requirement resulting from the use of a new and different peripheral device can be handled locally on the peripheral device; and (ii) by regulating the voltage locally on the peripheral device, the chance of interference being picked up on a power line of the interconnect (and possibly transferring noise to the peripheral device) is minimised.

Since both the data transfer and the power transfer are standardized for all of the peripheral devices, all of the connections of the interconnect 28 between the instrument control electronics 6 and the peripheral devices are interchangeable. A single type of cable 29 may therefore be used in the interconnect 28 for each of the connections. Referring to Figure 2, this means that the cable connection to, for example, Sensor #1 , could be plugged into any of the identical connectors 21 (e.g. sockets) on the instrument control electronics 6. Once the connection is made, microcontrollers in the instrument control electronics 6 and the local control electronics 23 on the peripheral devices can communicate over the optical serial data links, and the instrument control electronics can determine which peripheral device 20, 22, 24, 26 is connected into which connector 21 .

The interconnect 28 uses a combination of an optical interconnect for the data transfer and an electrical wired interconnect for the power transfer. These two connection types are advantageously combined in the cable according to the present invention as described in more detail below.

Figure 3A shows schematically the structure of one of the cables 29 which are embodiments of cables according to the present invention. The basic structure is like that of a conventional coaxial cable in that it has an inner conductor 40 and an outer conductor 42 in coaxial relationship, which are separated by an insulating material 44. The outer conductor 42 is covered by an outer protective insulating plastic sheath which is not shown in the Figure.

However, the cable of the present invention differs from a conventional coaxial cable is several ways. In a conventional coaxial cable, the inner conductor carries a high frequency signal and the outer conductor acts as shielding for the inner and is grounded. The choice and thickness of the insulating material is dependent on the required impedance of the cable.

In the cable of the present invention shown schematically in Figure 3A, the outer conductor 42 is again for connection to ground (GND) but the inner conductor 40 is not used for a high frequency signal but is used to carry power and is thus for connection to the power supply to carry the supply voltage, Vsuppiy (i.e. the standard 24V power supply 34 in this example) along the cable to power the peripheral devices 20, 22, 24, 26 in the example shown in Figure 2. To make this power connection the cable is connected at one end 41 a to one of the connectors 21 on the instrument control electronics 6. The other end 41 b of the cable is connected to one of the peripheral devices.

The materials and construction of the inner conductor 40 and outer conductor 42 are similar to those of a conventional coaxial cable, in this example, the inner conductor is a solid copper wire and the outer conductor is a braided copper tube for flexibility. In preferred embodiments, the solid copper wire is silver plated and/or the braided copper tube is silver plated to improve reflectance of their surface. The copper braid may optionally have a foil reflector on it inner surface for improvement of the internal reflectance. In addition, the dimensions of the inner conductor 40 and outer conductor 42 are similar to those of a conventional coaxial cable. Examples of cable dimensions are given below. In this example the length of the cable is between 0.25 and 1 .00 metres. Of course, in other embodiments, other cable lengths may be used. Where the cable is relatively long it may be useful to arrange that the outer surface of the inner conductor and the inner surface of the outer conductor have reflecting coatings on them, e.g. silvered or mirrored coatings, to increase internal reflection of the light waves inside the transparent insulating layer 44. In this way, advantageously, the amplitude of the optical signal transmitted to the end of the cable, even where the cable is bent, is increased.

Since the supply voltage is typically a DC signal as in this example, the characteristic impedance of the cable is not important and the so the choice and thickness of the insulating material 44 is not dependent on the required impedance of the cable as with conventional coaxial cables. AC power supplies to supply an AC voltage could also be used and even then the characteristic impedance of the insulator in the cable is not important at low frequencies encountered with AC power. So an AC power supply of 50/60Hz for example could be used without practical issues concerning the impedance of the insulator. The only electrical requirement of the insulating material 44 is that it is an electrical insulating layer. In this example the insulating material 44 is made of polymethylmethacrylate. The insulating material 44 is also flexible so that the cable is likewise flexible.

A main requirement and difference to conventional cables is that the insulating material 44 is transparent so that it is operable as an optical waveguide to allow the optical transmission of data along the cable in either direction. In this way, digitised data can be optically transmitted along the cable, in both directions, through the insulating material 44 using, for example, LEDs as optical transmitters and photodiodes as optical receivers. In this way, the cable provides a single low-cost cable that can carry both power and bidirectional data. The arrows 43 in Figure 3A schematically indicate the bi- directional optical transfer of data in and out of the cable insulator 44. The conductors 40 and 42 may be used to provide the internal reflectance of the optical signal. In addition, known techniques to improve the optical transmission properties of the cable such as stepped or graded refractive index of the insulating material could be used in the cable. These techniques are well known from conventional optical fibres.

Figure 3B shows schematically another view of one end of a preferred cable 29. The figure shows the inner conductor 40 of silver plated solid copper wire surrounded annularly by the polymethylmethacrylate transparent insulator 44, which in turn is surrounded annularly by the outer conductor 42 of silver plated copper braid. An outer plastic sheath 45, which may be made, for example, of PVC or PET, annularly surrounds the outer conductor 42 to protect and insulate the cable.

The cable dimensions may be similar to a conventional co-axial cable.

For example, the dimensions may be similar to either a RG316 co-axial cable or a RG6 co-axial cable. Examples of such dimensions are given in the table below.

The RG6 type dimensions would be more suitable, for example, for use with a higher power DC voltage supply.

An advantage of the present invention is that the data is transmitted optically, which allows for high data transfer rates, without the possibility of either generating or picking up electrical interference and without any ground bounce issues as with conventional coaxial cable. The data rate will be limited by the electronics attached to each end of the cable but typical data rates may be a few Mbit/s, up to a few 10's of Mbit/s. The EMC advantage of the cable is still significant even at relatively modest data rates of a few Mbits/sec (EMC problems are often related to the rise time of an electric data pulse, which can be fast and therefore generating EMC, even for low data rates). Furthermore, the cable can support bi-directional optical data transfer, for which may be used different wavelengths of light for different data directions.

Referring to Figure 4, there is shown a schematic cross sectional view (i.e. in a transverse cross section taken in a plane perpendicular to the longitudinal direction of the cable) of an alternative embodiment of a cable according to the present invention. In this embodiment, a first conductor 140 and a second conductor 142 each comprise a solid copper wire. The first conductor and the second conductor are positioned a distance apart (i.e. in a transverse direction to the longitudinal direction of the cable) in a side-by-side relationship within the cable, with the first conductor and the second conductor each being embedded within the insulating layer 144. In this embodiment, the insulating layer 144 has a non-transparent, preferably reflective sheath 150 surrounding it which thereby provides an outer surface around the insulating layer to reflect light internally within the insulating layer. In preferred embodiments, one of the wires 140, 142 is connected to the DC power voltage and the other to ground. It will be appreciated, however, that the shielding effect of having an outer conductor surrounding an inner conductor as in the coaxial embodiment is not present in this side-by-side embodiment, although it is possible to have the outer sheath 150 as shielding, e.g. if made of a metal, such as a metal braid.

Various protocols for the data transfer may be used, including for example protocols that are currently used for wired serial communication, which can be adapted for use with the cable of the present invention. Examples of such data transfer data transfer include: l ² C, SPI and 1 -wire.

Referring to Figure 5 there is shown schematically an interconnect system making use of a cable of the present invention, i.e. a cable as shown in Figures 3 or 4. The example shown in Figure 5 is again an example of an interconnect to connect instrument control electronics 60 and DC power supply 62 of an analytical instrument to a peripheral device 70, such as a sensor or actuator described above. The instrument control electronics 60 are typically connected to and controlled by a PC (not shown) which, in turn, receives data from the instrument control electronics 60. The power supply 62 comprises a 24V DC voltage generator to provide power to the peripheral device 70. The power supply 62 is connected by connection 64 to the inner conductor 40 of the cable which transmits the power to the peripheral device 70. The connection 64 may comprise, for example, a socket (not shown) into which plugs the inner conductor 40 of the cable, either directly or via an intermediate connector. The ground connection (GND) of the DC power circuit is made to the outer conductor 42 of the cable which is similarly connected at its other end to the ground connection of the peripheral device 70. A suitable connector type to connect the cable to the power supply is a BNC connector to make the two electrical connections to the two conductors of the coaxial cable. It will be appreciated that any socket and plug connections between components/cables described in these examples are merely examples and could be reversed, i.e. a component described as having the socket could instead have the plug and the component described as having the plug could instead have the socket.

The instrument control electronics 60 controls and also receives signals from an optical transceiver 66. The optical transceiver 66 comprises a light emitting diode (LED) 80 to optically transmit data 81 a according to instructions from the instrument control electronics 60. The optical transceiver 66 also comprises a photodiode 82 to receive optically transmitted data 81 b from the cable and transmit it to the instrument control electronics 60. In the example, the LED 80 and the photodiode 82 are both housed in the connector (e.g. BNC connector) which connects to the cable in such a way that the LED 80 is aligned to transmit data into the insulating material 44 of the cable and the photodiode 82 is aligned to receive data from the insulating material 44. In other embodiments, the optical transceiver 66, e.g. LED 80 and the photodiode 82, may be remote from the connector but transmit light to and receive light from the connector via, e.g., optical fibres. A BNC connector is preferred to both make the electrical connections and the optical connections. Thus, a simple connector may be used to connect the cable to the electronic components (e.g. a PCB of the instrument control electronics or peripheral device), such as e.g. a modified BNC-type connector. Such a connector requires only the wired power supply and ground electrical connections and an optical connection for the optical transfer of the data to the insulating layer. Details of examples of suitable connectors are described below with reference to Figures 6 to 8.

At the peripheral device 70 the power from power supply 62 is received via the inner conductor 40 of the cable which plugs into a socket on the peripheral device 70 which is part of a connection 74 to a local voltage regulator 72 on the peripheral device. The voltage regulator 72 generates the necessary power supplies for the local control electronics 78 of the peripheral device and other powered component(s) 79, such as a sensor or actuator for example as described above. The optically transmitted data 81 a from the instrument control electronics 60 is received at the peripheral device 70 via the insulating material 44 of the cable. The peripheral device 70 has an optical transceiver 76 to receive the optically transmitted data. In particular, the optical transceiver 76 comprises a photodiode 86 to receive optically transmitted data 81 a from the cable. The data received by the optical transceiver 76 is used to control the local control electronics and thereby the other powered components(s) 79 such as a sensor or actuator. Data is provided by the local control electronics 78, including data fed to it from the other powered components(s) 79 which are connected to the local control electronics 78. The data provided by the local control electronics 78 is fed to the optical transceiver 76 of the peripheral device. The optical transceiver 76 of the peripheral device also comprises an LED 88 to optically transmit the data 81 b from the local control electronics 78 to the cable and through the cable to the optical transceiver 66 connected to the instrument control electronics 60.

Referring to Figures 6 to 8, there are shown embodiments of connectors suitable for connecting a cable according to the present invention to electronic components. The connectors shown in Figures 6 to 8 are based on a standard BNC plug/socket arrangement, but with surface mounted optical components (an optical receiver and an optical transmitter, being in the example a photodiode and an LED respectively) added into the socket. Figure 6 shows a perspective view of a BNC socket or female connector 200, which is mounted on a first electronic component, e.g. on a PCB of the component. The BNC socket 200 comprises a conventional BNC outer socket housing 202 in the form of a metal barrel or sleeve for making an electrical connection to the outer conductor of a co-axial cable according to the present invention. The outer socket housing 202 has on its outer surface bayonet lugs 203 to enable the BNC plug described below to lock onto it in a standard BNC bayonet locking mechanism. The BNC socket 200 also comprises a conventional BNC inner socket or contact 206, in the form of a metal split sleeve co-axial with the outer socket housing 202, for making an electrical connection to the inner conductor of the co-axial cable. The BNC socket 200 further comprises a surface 204, which is of a round shape located within the outer socket housing 202, which surface in the example is a part of a flexible PCB (e.g. comprising Kapton (trade name)), and the PCB surface 204 supports a photodiode 208 and an LED 210. Another part of the flexible PCB is a ribbon cable 212. The ribbon cable 212 carries electrical connections to the photodiode 208 & LED 210. The ribbon cable in general in this context means a flat, flexible multi-way electrical connection, which may be, e.g., in the form of a 4-way ribbon cable. The PCB is a single piece of PCB, such that the surface 204 and the ribbon cable 212 are one component which has a round part (the surface 204) and a "tail" (the ribbon cable 212). In this way, the PCB surface 204 which supports the optical components needs no separate connection to the ribbon cable since they are one component.

Figure 7 shows a perspective view of a BNC plug or male connector 250, for connection to the BNC socket shown in Figure 6. Figure 8 shows a cross-sectional side view of the BNC socket 200 and the BNC plug 250 in alignment for connection together. The BNC plug 250 is connected on the end of a co-axial cable 251 according to the invention, e.g. a cable of the type shown in Figure 3A. The BNC plug 250 comprises a conventional BNC outer plug housing 252, in the form of a metal barrel or sleeve, which as shown in Figure 8 is in an electrical connection with the outer conductor 262 of the coaxial cable 251 (via contact with conducting collar 268 inserted under outer conductor 262 of the cable). The outer plug housing 252 has recesses 257 to receive therein the bayonet lugs 203 of the outer socket housing 202. The BNC plug 250 also comprises a conventional BNC inner contact pin 256, in the form of a metal pin, which makes an electrical connection to the inner conductor 260 of the co-axial cable 251 . The BNC plug 250 further comprises an optically transparent insert 254 (e.g. made of a fibre optic material such as a transparent plastic) to guide light into and out of the optically transparent insulating layer or waveguide 264 of the co-axial cable 251 . The optically transparent insert 254 comprises an annular member located around the inner contact pin 256. The co-axial cable has an outer protective sheath 266 of plastics material.

The connection of the BNC plug 250 to the socket 200 can be understood from Figure 8. For connection, the outer plug housing 252 is located over and in contact with the outer socket housing 202, the recesses 257 of the plug receiving the bayonet lugs 203 of the socket and the outer plug and socket housings 252 and 202 thereby being locked together by a conventional bayonet locking mechanism. In so locking together the outer housings of the plug and socket, the inner contact pin 256 of the plug is pushed into the inner contact 206 of the socket to make electrical connection therewith. When the plug and socket connectors 200 and 250 are connected the optical components 208 (photodiode) and 210 (LED) located in the socket 200 are aligned with the optical insert 254 in the plug 252 so that light carrying data signals can be transmitted from the LED 210 into the optical insert 254 and thereafter guided into the transparent insulating layer 264 of the cable 251 and light carrying data signals can be received at the photodiode 208 from insulating layer 264 via the optical insert 254.

The other end of the cable 251 may comprise a similar BNC plug connector to the one shown in Figure 7 which may connect to a similar BNC socket to the one shown in Figure 6 on a second electronic component, thereby to allow bi-directional power and/or data transmission between the first and second electronic components.

The examples above show a BNC socket connector on the electronic component and the BNC plug connector on the cable. However, it will be appreciated that with simple modification a BNC plug connector may be arranged on the electronic component to house the optical components and a BNC socket connector arranged on the cable.

It can be seen from the above embodiments, that the invention advantageously provides a single cable to carry both the power supply and bidirectional data to and from the peripheral device. Each peripheral device may be connected using a single such cable which reduces cable costs and the cable itself may be manufactured using known coaxial cable manufacturing methods. The resultant cableform inside the instrument is thereby significantly reduced and it enables a system architecture in which a fewer number of components are used thereby making assembly and servicing/repair simpler. With an appropriate system architecture, the same cable type (according to the present invention) can be universally used for all connections to peripheral devices of the system.

The use of optical transmission of the data provides the advantages of reduced EMC emissions and eliminated ground bounce when transferring data at high speed. The coaxial construction provides the further advantage that when the outer conductor is connected to ground it reduces pick-up of interference on the inner conductor which carries the power supply.

The examples above relate to one possible implementation of the invention in the situation of an analytical instrument. However, it will be understood that the invention is not limited to such implementations. For example the instrument control electronics described in the examples could be any electronic control system and the peripheral devices described in the examples may be any other electronic devices to be connected to the electronic control system.

As used herein, including in the claims, unless the context indicates otherwise, singular forms of the terms herein are to be construed as including the plural form and vice versa. For instance, unless the context indicates otherwise, a singular reference herein including in the claims, such as "a" or "an" means "one or more".

Throughout the description and claims of this specification, the words "comprise", "including", "having" and "contain" and variations of the words, for example "comprising" and "comprises" etc, mean "including but not limited to", and are not intended to (and do not) exclude other components.

It will be appreciated that variations to the foregoing embodiments of the invention can be made while still falling within the scope of the invention. Each feature disclosed in this specification, unless stated otherwise, may be replaced by alternative features serving the same, equivalent or similar purpose. Thus, unless stated otherwise, each feature disclosed is one example only of a generic series of equivalent or similar features.

The use of any and all examples, or exemplary language ("for instance", "such as", "for example" and like language) provided herein, is intended merely to better illustrate the invention and does not indicate a limitation on the scope of the invention unless otherwise claimed. No language in the specification should be construed as indicating any non- claimed element as essential to the practice of the invention.

Any steps described in this specification may be performed in any order or simultaneously unless stated or the context requires otherwise.

All of the features disclosed in this specification may be combined in any combination, except combinations where at least some of such features and/or steps are mutually exclusive. In particular, the preferred features of the invention are applicable to all aspects of the invention and may be used in any combination. Likewise, features described in non-essential combinations may be used separately (not in combination).