BACKGROUND

Today’s communication networks provide transport of voice, video and data to both residential and commercial customers, with more and more of those customers being connected by fiber optic cables. In these communication networks, information is transmitted from one location to another by sending pulses of light through the fiber optic cables. Fiber optic transmission provides several advantages over electrical transmission techniques, such as increased bandwidth and lower losses.

So-called fiber to the premises (FTTP) fiber optic network configurations are in demand and are becoming more prevalent. FTTP network configurations provide a complete fiber optic connection from the service provider’s network to the customer’s service location. This provides a very high bandwidth service connection. FTTP network configurations often utilize a network node to provide the final distribution point between the service provider network and the premises. One example of a FTTP network configuration is a so-called fiber to the home (FTTH) network configuration, which provides a fiber optic connection between the network node and a connection point at the outside of a residence, such as termination box that is mounted on the outside of a house. Another example of a FTTP network configuration is a so-called fiber to the building (FTTB) network configuration, which provides a fiber optic connection between the network node and a termination point within a multi-tenant building, such as an equipment room or rack within the basement of an office.

As FTTP network configurations are becoming more prevalent, one issue of focus within the industry relates to customer turnover. New FTTP installations occur regularly to provide FTTP fiber optic service to new customers. Meanwhile, other customers with existing FTTP services regularly cancel services. This turnover requires fiber optic service technicians to regularly access fiber optic nodes to reconfigure the hardware and connections within fiber optic network node. In some cases, a technician may intentionally or unintentionally disconnect a fiber optic connection to a dwelling or building that is not currently subscribing to fiber optic service. If service is to be reactivated at the disconnected premises, the subscriber does not know whether an active fiber optic connection exists. Valuable technician resources may be required to inspect the fiber node and the connection to the premises to determine whether an active fiber optic connection exists. SUMMARY

A fiber optic network device is disclosed. According to an embodiment, the fiber optic network device includes a fiber optic cable retention mechanism that is configured to securely retain an end of a fiber optic cable, and an active service indicator circuit. The active service indicator circuit includes a photodetection circuit having a light sensor that is positioned to receive light being transmitted from the end of the fiber optic cable when the fiber optic cable is secured by the fiber optic cable retention mechanism. The active service indicator circuit further includes a

communication circuit connected to the photodetection circuit. The photodetection circuit is configured to generate a binary active service indicator signal that has a first state when light is detected by the light sensor and has a second state when no light is detected by the light sensor. The communication circuit is configured to generate an electronic output signal that communicates the state of the binary active service indicator signal.

A method of detecting active fiber optic service in a fiber optic cable is disclosed. According to an embodiment, the method includes providing a fiber optic network device. The fiber optic network device includes a fiber optic cable retention mechanism, an active service indicator circuit, and an externally accessible communications element. The method further includes inserting a fiber optic cable into the fiber optic cable retention mechanism such that an endpoint of one or more optical fibers from the fiber optic cable is positioned to transmit light on the active service indicator circuit. The method further includes determining whether the fiber optic cable is active using the active service indicator circuit. Determining whether the fiber optic cable is active includes generating a binary active service indicator signal that occupies a first state if light is detected by the active service indicator circuit and occupies a second state if no light is detected by the active service indicator circuit and generating an electronic output signal that communicates the state of the binary active service indicator signal to the externally accessible communications element.

A fiber optic network assembly is disclosed. According to an embodiment, the fiber optic network assembly includes a fiber optic cable and a fiber optic testing device. The fiber optic testing device includes a fiber optic cable retention mechanism that securely retains an end of the fiber optic cable. The fiber optic testing device further includes active service indicator circuit that includes a photodetection circuit comprising a light sensor that is positioned to receive transmitted light from the end of the fiber optic cable and a communication circuit connected to the photodetection circuit. The fiber optic testing device further includes an externally accessible communications element connected to the communication circuit. The photodetection circuit is configured to generate a binary active service indicator signal that occupies a first state when light is detected by the light sensor and occupies a second state when no light is detected by the light sensor. The communication circuit is configured to generate an electronic output signal that communicates the state of the binary active service indicator signal to the externally accessible communications element.

BRIEF DESCRIPTION OF THE DRAWINGS

Fig. 1 depicts a fiber to the premises environment, according to an embodiment.

Fig. 2 depicts a fiber optic network device that is configured to detect active fiber optical service, according to an embodiment.

Fig. 3, which includes Figs. 3A, 3B, 3C and 3D, depicts an example implementation of a fiber optic network device as a mountable wall-plate, according to an embodiment. Fig. 3A depicts a front-facing view of the mountable wall-plate fully assembled. Fig. 3B depicts an isometric view of the mountable wall-plate with the front plate detached from the rear plate. Fig. 3C depicts an overhead view of the rear plate with a fiber optic cable inserted in the retention mechanism. Fig. 3D depicts a close-up view of the retention mechanism along the cross-sectional plane A-A identified in Fig. 3C.

Fig. 4 depicts a high-level schematic of an active service indicator circuit that is used to detect active fiber optic service, according to an embodiment.

Fig. 5 depicts a detailed schematic of an active service indicator circuit that is used to detect active fiber optic service and to generate an external output signal indicating active service as a blinking light, according to an embodiment.

Fig. 6 depicts a detailed schematic of an active service indicator circuit that is used to detect active fiber optic service, according to another embodiment.

Fig. 7 depicts a detailed schematic of an active service indicator circuit that is used to detect active fiber optic service and to generate an external output signal indicating active service as an electronic signal at a data port, according to an embodiment.

DET AIDED DESCRIPTION

Embodiments of a fiber optic network device are described herein. The fiber optic network device includes a receptacle that receives and securely retains an end of a fiber optic cable for testing. In embodiments, the receptacle accommodates standardized fiber optic connectors, e.g., SC connectors, FC connectors, etc. The fiber optic network device additionally includes an active service indicator circuit with a light sensor positioned near the receptacle. The active service indicator circuit uses the light sensor to detect the presence of light (or lack thereof) at the end of the fiber optic cable that is received by the receptacle.

The fiber optic network device provides a low-cost and effective solution for testing the status of fiber optic cables in FTTP network locations. This is partially attributable to the design of the active service indicator circuit, which can perform the following functions. First, the active service indicator circuit generates an active service signal based upon the detection of light from the light sensor. The active service signal is binary, meaning that it can only occupy one of two states, e.g.,“1” for active service and“0” for no active service. Second, the active service indicator circuit uses the active service signal to generate an electronic output signal that communicates the state of the binary active service indicator signal via a communications element. This communication can be achieved by a simple design, such as the illumination of a a lighting element by a steady state or oscillating current. Various aspects of the circuit topology of the active service indicator circuit, including a separate circuit branch for an indicator light emitting diode and a dedicated transistor feeding current into the gate of a programmable unijunction transistor, produce an oscillating current with sufficient frequency and magnitude to communicate the status of the fiber optic cable in a reliable way, e.g., via a clearly perceptible blinking LED. Accordingly, the fiber optic network device can have a substantially lower component count and complexity than expensive testing equipment that requires complex functionality, e.g., measurement of signal strength, frequency, etc.

Referring to Fig. 1, a fiber to the premises environment 100 is depicted. The fiber to the premises environment 100 includes a fiber optic network node 102 that is used for local distribution of fiber optic telecommunications services. Fiber optic service is delivered from a service provider access point (not shown) to the fiber optic network node 102 by a second-tier fiber optic connection 104. A first fiber- to-the-premises-connection 106 goes from the fiber optic network node 102 to a termination box 108 that is mounted outside of a residence 110. In addition, a plurality of additional fiber-to-the-premises-connections 112 goes from the fiber optic network node 102 to other service locations, e.g., commercial or residential buildings (not shown). The fiber optic network node 102 includes hardware that completes (or can complete) a service connection between the second-tier fiber optic connection 104 and the fiber to the premises locations that are within the service territory of the fiber optic network node 102. Examples of this hardware includes optical circuits, splitters, multiplexers, standardized connectors, etc.

The first fiber- to-the-premises-connection 106 ends at a termination box 108 that is mounted on an external wall of the residence 110. The termination box 108 provides a dedicated space that encloses and protects the cabling and hardware stored therein. Exemplary equipment that is commonly stored in these enclosures includes cabling (e.g., coaxial cable, twisted pair, fiber optic, etc.), standardized connectors (CAT 5, RJ45, SC, LC, etc.), mounting brackets, cassettes, etc.

The residence 110 includes an interior fiber optic cable 114 that is routed between the termination box 108 and an interior network connection point 116. The interior network connection point 116 provides active fiber optic service if: (1) the interior fiber optic cable 114 is properly connected to the first fiber-to-the-premises-connection 106 at the termination box 108; and (2) the first fiber-to-the-premises-connection 106 is properly connected to the second-tier fiber optic connection 104 at the fiber optic network node 102.

The fiber optic network device to be described herein enables testing for interruptions in service in either one of the above described connection points. That is, the fiber optic network device can be used to determine whether the interior fiber optic cable 114 is active at a location that is at or near the interior network connection point 116. Further, the fiber optic network device can be used to determine whether the first fiber-to-the-premises-connection 106 is active at a location that is at or near the termination box 108. As a result, the fiber optic network device enables a customer to determine whether there is a disruption in fiber optic service and, if so, whether the disruption exists at the termination box 108 or the fiber optic network node 102.

Referring to Fig. 2, a fiber optic network device 200 is depicted, according to an

embodiment. The fiber optic network device 200 is designed to detect active fiber optic service in a fiber optic cable 300. The fiber optic cable 300 has been terminated so the interior optical fibers (now shown) are able to transmit light at an endpoint 302 of the fiber optic cable 300. This termination can be provided by a standardized fiber optic connector, e.g., an FC connector (lucent connector), an SC connector (standard connector), FC connector (ferrule connector), or an ST connector (straight tip connector), to name a few.

The fiber optic network device 200 includes a retention mechanism 202 that is configured to securely retain the fiber optic cable 300 for reliable observation of light at the endpoint 302 of the fiber optic cable 300. In the case of a fiber optic cable 300 that includes a male standardized fiber optic connector (e.g., SC, FC, FC, ST, etc.), the retention mechanism 202 can be configured as a corresponding female standardized connector. Alternatively, for a fiber optic cable 300 that does not include a standardized fiber optic connector, the retention mechanism 202 can be implemented using any of a variety of structures that engage with the fiber optic cable 300 and retain the fiber optic cable 300 in place under modest tension, e.g., 5 lbs. Examples of these structures include clamps, brackets, snap in features, pinchers, etc.

The fiber optic network device 200 includes an active service indicator circuit 204 that is positioned sufficiently close to the fiber optic cable retention mechanism 202 such that the active service indicator circuit 204 receives transmitted light 304 from the end of the fiber optic cable 300 that is secured by the fiber optic cable retention mechanism 202. The active service indicator circuit 204 includes a photodetection circuit 206 and a communication circuit 207.

The photodetection circuit 206 includes a light sensor that is configured to detect the presence (or lack thereof) of light 304 from the end of the fiber optic cable 300. The photodetection circuit 206 uses the light sensor to generate a binary active service indicator signal 212. The binary active service indicator signal 212 can occupy one of two states. When light is detected by the light sensor, the binary active service indicator signal 212 occupies a first state. When light is not is detected by the light sensor, the binary active service indicator signal 212 occupies a second first state. Generally speaking, the first and second states of the binary active service indicator signal 212 can be any electrical or electromagnetic state, e.g., voltage, current, frequency, etc. For example, the first state of the binary active service indicator signal 212 can correspond to a fixed electrical current (e.g., 50 milliamps) at an electrical node of the photodetection circuit 206, and the second state of the binary active service indicator signal 212 can correspond to substantially no current (e.g., a current of less than about 5 percent of the current of the fixed electrical current) at the same electrical node of the photodetection circuit 206.

The communication circuit 207 transforms the binary active service indicator signal 212 into an electronic output signal 213 that can be used to convey the status of the fiber optic cable to the user of the fiber optic network device 200. The electronic output signal 213 is dependent upon the status of the binary active service indicator signal 212. That is, a transition from the first state of the binary active service indicator signal 212 to the second state (or vice-versa) will necessarily cause a change in state of the electronic output signal 213. The communication circuit 207 is connected to a communications element 215 and is configured to convey the electronic output signal 213 at the communications element 215. The communications element 215 can be any of a variety of devices capable of conveying information. For example, the communications element 215 can be a visual display on an exterior surface of the fiber optic network device 200. In a one example, the visual display can be implemented as a single light. In another example, the visual display can be a screen that displays characters (e.g., an FED display). Alternatively, the communications element 215 can be a telecommunications data port, such as an ethernet or USB (universal serial bus) interface. In yet another example, the communications element 215 can be a wireless transmission device, such as antenna. Generally speaking, the electronic output signal 213 can be any electrical signal that can convey the state of the binary active service indicator signal 212 via the communications element 215. For example, the electronic output signal 213 can be an electrical current that illuminates a light bulb in the case that the communications element 215 is configured as a light bulb. In another example, the electronic output signal 213 can be a modulated voltage that provides a digital bitstream or bit that is readable at a communications element 215 that is configured as a

telecommunications data port. In another example, the electronic output signal 213 can be an RF signal that can be transmitted across a communications element 215 that is configured as an antenna.

The fiber optic network device 200 may optionally include a switch 205 that is accessible at an exterior surface of the fiber optic network device 200. The switch 205 is configured to switch the fiber optic network device 200 between an active test mode and an inactive test mode. In the active test mode, the electronic output signal 213 is provided at the communications element 215. In the inactive mode, the electronic output signal 213 is not provided at the communications element 215. This can be done by configuring the switch 205 to connect or disconnect the power supply of the active service indicator circuit 204 so that the photodetection circuit 206 and the communication circuit 207 are inactive when the switch 205 is in the OFF position and only active when the switch 205 is in the ON position. In this way, the power consumption of the fiber optic network device 200 can be efficiently managed.

Referring to Fig. 3, an example implementation of the fiber optic network device 200 is depicted, according to an embodiment. In this example, the fiber optic network device 200 is configured as a wall-plate that is designed to be mounted on an interior wall 301 of a residence. The wall-plate can have a similar or identical geometry to that of a standard wall-plate. For example, the wall-plate can have a width (W) of about 2.75” and a height (H) of about 4.5,” which corresponds to the footprint of a standard- sized electrical outlet or light switch. More generally, the wall-plate can have any of a variety of shapes and sizes, and in particular can be implemented in any shape that can be mounted on an interior wall with a low-profile, e.g., protruding away from the wall by less than 0.5”.

The wall plate includes a rear plate 308 and a front plate 310. According to an embodiment, the rear plate 308 and the front plate 310 are configured to interface with one another. That is, the rear plate 308 and a front plate 310 are configured to physically mate with one another and form an interconnected structure. When interfaced, the rear plate 308 and front plate 310 enclose an interior volume, i.e., a three-dimensional space. In the depicted embodiment, this is achieved by a raised collar 312 on the rear plate having the same general shape as the outer perimeter of the front plate 310. The front plate 310 includes sidewalls 314 that fit around the raised collar 312. More generally, the front plate 310 can include a retention mechanism or mechanisms (e.g., hooks, ridges, etc.) that is configured to mate with corresponding features in the rear plate 308.

A fiber optic cable 300 can be inserted into the retention mechanism 202 as depicted for testing. The fiber optic cable 300 can be a cable that is routed from a termination box through the interior walls of a residence to an interior network connection point, e.g., as illustrated with reference to Fig. 2, for example. As shown in Fig. 3D, a light sensor 209 of the active service indicator circuit 204 is positioned within the retention mechanism 202 to receive transmitted light directly from the endpoint 302 of the fiber optic cable 300. The remaining portions of the active service indicator circuit 204 can be provided anywhere within the interior volume enclosed by the rear plate 308 the front plate 310. For example, the active service indicator circuit 204 can be provided in a circuit hosing 315 that is connected to the light sensor 209 by a wire 315. The front plate 310 is designed to convey the electronic output signal 213 at the communications element 215 when the rear and front plates 308, 310 are interfaced with one another. For example, the front plate 310 can include a window that exposes a lighting element from the active service indicator circuit 204, in the case that the communications element 215 is configured as a visible display.

The fiber optic network device 200 according to the embodiment of Fig. 3 may include a mechanism that moves the light sensor 209 out of the light path of the fiber optic cable 300 when the device is not in active test mode. This allows a second fiber optic cable (not shown) to be plugged into a second side 316 of the retention mechanism 202 and receive telecommunications service from the fiber optic cable 300. That is, the fiber optic network device 200 of Fig. 2 can be configured both as a test mechanism and as an outlet for delivering active fiber optic service.

Instead of a wall plate configuration as discussed above, the geometry of the fiber optic network device 200 and the location of the retention mechanism 202 can be adapted to enable testing of a fiber optic cable in a variety of different settings inside or outside of a residence or commercial building. For example, the fiber optic network device 200 can be configured to be mounted in a termination box, such as the termination box 108 described herein. In this case, the structural features of the fiber optic network device 200, e.g., size, geometry, sealing, etc., can be tailored to fit within the termination box and adequately protect the active service indicator circuit 204 from exterior environmental conditions.

Referring to Fig. 4, a high-level schematic of the active service indicator circuit 204 is depicted, according to an embodiment. In this embodiment, the active service indicator circuit 204 is configured to convey the electronic output signal 213 to a lighting element 214 that illuminates based upon a state of the electronic output signal 213. The active service indicator circuit 204 includes the photodetection circuit 206 and the communication circuit 207. The communication circuit 207 includes an oscillator circuit 208, and an illumination circuit 210.

The photodetection circuit 206 includes a light sensor 209. The light sensor 209 is configured to detect the presence of light 304, and more particularly a light signal that is used in fiber optic communications. The light signal can be coherent or incoherent light that is modulated at a very high frequency, e.g., in the range of 150-300 THz. The light sensor 209 is a device that can recognize these signals and generate a steady state signal (e.g., an electrical current) in response. Examples devices for the light sensor 209 include photodiodes, photoresistor, phototransistors, etc. The active service indicator circuit 204 is arranged in the fiber optic network device 200 sufficiently close to the retention mechanism 202 to provide an unobstructed path for light from a retained fiber optic cable to reach the light sensor 209.

The photodetection circuit 206 generates the active service signal 212 when light 304 is detected by the light sensor 209. The active service signal 212 can be generated directly by the light sensor 209. For example, in the case that the light sensor 209 is implemented as a phototransistor, the active service can be a drain current of the phototransistor that occurs when the gate receives light. Alternatively, the active service signal 212 can be generated indirectly by the light sensor 209. For example, the light sensor 209 can generate an electrical current in the presence of light, which in turn triggers another device, e.g., a transistor, diode, etc. to generate the active service signal 212.

The oscillator circuit 208 is configured to continuously oscillate between a first state and a second state. This oscillation occurs only when the active service signal 212 is generated by the photodetection circuit 206 and received by the oscillator circuit 208. The first and second states are measurable electrical states, e.g., current, voltage frequency, etc., at a node of the oscillator circuit 208. For example, the oscillator circuit 208 can be configured to set a node of the oscillator circuit 208 to a first electrical state (e.g., zero volts, zero amps, 10 Hz, etc.) and a second electrical state (e.g., 1 volt, 10 milliamps, 50 Hz, etc.) in a periodic fashion. The oscillation is continuous in the sense that periodic repetition between the first state and the second state occurs so long as the active service signal 212 is present. Thus, the continuous oscillation is dependent upon the active service signal 212 and, consequently, is dependent upon the presence of light being detected by the light sensor 209. When there is no active service signal 212, this continuous oscillation ceases. For instance, the oscillator circuit 208 can maintain the circuit node at a steady electrical state (e.g., zero volts, zero amps, 10 Hz, etc.) when the active service signal 212 does not exist.

Generally speaking, the oscillator circuit 208 can include a wide variety of circuit elements and circuit topologies that achieve oscillation between the first state and the second state in the above described manner. Exemplary circuit topologies that achieve oscillation include RC oscillators, LC oscillators, and negative resistance oscillators, to name a few. These circuits can include active devices such as transistors (e.g. MOSFETs, bipolar junction transistors (BJTs), etc.), thyristors, unijunction transistors as well as passive devices, such as inductors, capacitors, resistors, etc.

The illumination circuit 210 includes a lighting element 214. The lighting element 214 can be any device that generates visible light using electrical current. Exemplary devices for the lighting element 214 include incandescent lights, fluorescent lights, and light emitting diodes. The lighting element 214 is externally visible on the fiber optic network device 200 such that the user of the fiber optic network device 200 can observe the illumination of the lighting element 214.

The illumination circuit 210 is configured to illuminate based upon the oscillation state of the oscillator circuit 208 between the first and second states. For example, in the case that the oscillator circuit 208 includes a circuit node with a periodically varying zero and non-zero current, the oscillator circuit 208 can include a direct electrical connection between this oscillating circuit node and the lighting element 214 so that the oscillating current directly induces an oscillating current in the lighting element 214. Alternatively, an indirect electrical connection between the circuit node of the oscillator circuit 208 that oscillates and the lighting element 214 can be provided. This indirect connection can be provided using a network of switching devices, amplifiers, resistors, etc. so that the lighting element 214 receives a varying voltage or current that is dependent upon the oscillation state of the oscillator circuit 208. The blinking frequency of the lighting element 214 may be the same frequency of the oscillation between the first and second states. For example, the illumination circuit 210 can be configured to illuminate the lighting element 214 in the first state and to turn off the lighting element 214 in the second state. Alternatively, the blinking of the lighting element 214 can be different from the frequency of the oscillation between the first and second states. This can be done using a network of delay elements, LC circuits, etc. Referring to Fig. 5, a detailed electrical schematic of the active service indicator circuit 204 is depicted, according to an embodiment. In this embodiment, the photodetection circuit 206 includes a first resistor 216 and a first light emitting diode 218 that is configured as a light sensor and connected in series with the first resistor. The oscillator circuit 208 includes a first capacitor 220, a second resistor 222, a first programmable unijunction transistor 224, a first bipolar junction transistor 226, and a voltage divider 228, which is provided by a third resistor 230 and a fourth resistor 232. The illumination circuit 210 includes a second light emitting diode 234. A DC power supply 236 provides a DC voltage to the active service indicator circuit 204.

The working principle of the active service indicator circuit 204 is as follows. The light sensor 209 of the photodetection circuit 206 is provided by the first light emitting diode 218. The first light emitting diode 218 is arranged in reverse conducing light emitting diode configuration. This is achieved by selecting a diode with an emission wavelength of the first light emitting diode 218 that is close to, e.g., within about +/- 10%, of the wavelength of the light to be detected.

According to this configuration, the first light emitting diode 218 permits current to flow from the cathode to anode (i.e., in a reverse conduction direction) when the first light emitting diode 218 is exposed to light. In other words, the presence of light of the correct wavelength induces a leakage current in the first light emitting diode 218. When not exposed to light, the first light emitting diode 218 is in a blocking mode such that the voltage provided by the DC power supply 236 does not induce a current. The resistance of the first resistor 216 can be tailored to control the magnitude of this reverse conducting current.

The reverse current of the first light emitting diode 218 that is triggered by the detection of light provides the active service signal 212 that triggers oscillation in the oscillator circuit 208. In particular, the reverse current in the first light emitting diode 218 causes the first capacitor 220 to charge, which produces a voltage across the first capacitor 220. This voltage biases the anode and cathode terminals (i.e., the output terminals) of the first programmable unijunction transistor 224. Thus, the first capacitor 220 provides a charge storing element that is used to bias the first programmable unijunction transistor 224.

The first programmable unijunction transistor 224 has bimodal IV characteristics. More particularly, in a first operational region, a rise in current across the anode and cathode terminals of the first programmable unijunction transistor 224 corresponds with a steep rise in voltage across these terminals. This holds true until the voltage across the anode and cathode terminals reaches the peak voltage (also referred to as the“trigger voltage”) of the device. At this time, the first programmable unijunction transistor 224 transitions to a second operational region, which is known as the so-called“negative resistance region.” In this region, the resistance across the anode and cathode terminals decreases with increasing current flowing through the anode and cathode terminals.

Due to the bimodal IV characteristics of the first programmable unijunction transistor 224, the first capacitor 220 periodically charges and discharges. In particular, the first capacitor 220 charges in the first operational region of the first programmable unijunction transistor 224 and discharges in the second operational region of the first programmable unijunction transistor 224. The peak voltage of the first programmable unijunction transistor 224, which is set by the voltage applied to the gate, determines the transition point between the first and second operational regions (i.e., from charging to discharging). The minimum voltage of the first programmable unijunction transistor 224, which is an intrinsic property of the device, determines the transition point from discharge to charge. This cycle repeats itself so long as the reverse conducting current is generated by the first light emitting diode 218.

The first bipolar junction transistor 226 in conjunction with the voltage divider 228 set the peak voltage of the first programmable unijunction transistor 224. A middle node 238 of the voltage divider provides a voltage that is a fraction of the voltage provided by the DC power supply 236.

The magnitude of this voltage is determined by the ratio of resistance between the third and fourth resistors 230, 232. This voltage is used to select a bias point for the first bipolar junction transistor 226 in the forward active mode. In other words, the first bipolar junction transistor 226 is used as a voltage-controlled resistor. In this way, a voltage drop across the first bipolar junction transistor 226 is used to set the voltage at the gate of the first programmable unijunction transistor 224.

The oscillating current flowing through the oscillator circuit 208 is provided to the illumination circuit 210 to periodically illuminate the second light emitting diode 234. In this case, the second light emitting diode 234 is directly electrically connected to a first node 240 of the oscillator circuit 208, which is a cathode of the first programmable unijunction transistor 224. Thus, the second light emitting diode 234 does not illuminate when the oscillator circuit 208 is in the first state and illuminates when the oscillator circuit 208 is in the second state.

Referring to Fig. 6, an electrical schematic of the active service indicator circuit 204 is depicted, according to another embodiment. The active service indicator circuit 204 of Fig. 6 is identical to the active service indicator circuit 204 of Fig. 5 with the following exceptions. First, the photodetection circuit 206 has a different configuration that includes a first resistor 216, a first light emitting diode 218, and a second bipolar junction transistor 242. Second, the illumination circuit 210 has a different configuration that includes a second light emitting diode 234, a fifth resistor 244 and a third bipolar junction transistor 246.

The photodetection circuit 206 uses the first light emitting diode 218 to control the ON/OFF state of the second bipolar junction transistor 242. In this embodiment, an anode of the first light emitting diode 218 is connected to a control terminal (i.e., a base terminal) of the second bipolar junction transistor 242. Thus, when the first light emitting diode 218 senses the presence of light, the reverse conducting current flowing through the first light emitting diode 218 is fed to the control terminal of the second bipolar junction transistor 242. As a result, the second bipolar junction transistor 242 turns ON and enters a conductive state. The output current generated at an output of the second bipolar junction transistor 242 (e.g., the emitter current in the case of a bipolar NPN transistor) provides the active service signal 212.

The illumination circuit 210 is implemented with a first circuit branch 248 that is in parallel with the DC power supply 236. The first circuit branch 248 includes the second light emitting diode 234, the fifth resistor 244 and the third bipolar junction transistor 246 connected in series with one another. In this configuration, the oscillator circuit 208 controls the current flowing through the first circuit branch 248 by controlling the conductive state of the third bipolar junction transistor 246. More particularly, the first node 240 is directly connected to the control terminal of the third bipolar junction transistor 246. As a result, in the second state of the oscillator circuit 208, the third bipolar junction transistor 246 is turned ON. This causes current to flow through the first circuit branch 248. The resistance of the fifth resistor 244 can be tailored to control the magnitude of the current flowing through the first circuit branch 248 current and hence control the brightness of the second light emitting diode 234. In the first state of the oscillator circuit 208, the third bipolar junction transistor 246 is turned OFF and no current flows through the second light emitting diode 234.

The circuit topology of the of the active service indicator circuit 210 described herein provides several advantages for low-power and low-voltage source applications. For example, in embodiment of Figs. 5 and 6, the current that charges the first capacitor 220 is generated by a transistor, namely, the second bipolar junction transistor 242. This enables rapid charging of the first capacitor 220, which in turn enables high frequency oscillation of the oscillator circuit 208. In addition, the oscillator circuit 208 in both embodiments of Figs. 5 and 6 advantageously connects the gate of the first programmable unijunction transistor 224 to the output of a transistor, namely the first bipolar junction transistor 226. As the amount of current flowing at the output of the first programmable unijunction transistor 224 substantially depends upon the amount of current being injected to the gate, the first bipolar junction transistor 226 enhances the current at the first node of the oscillator circuit 208. In addition, in the embodiment of Fig. 6,

the second light emitting diode 234 is advantageously placed on a separate current branch that is not dependent upon the discharge current of the first capacitor 220 flowing through the first programmable unijunction transistor 224. The impact of these features either individually or in combination with one another provides a circuit that produces a relatively strong current flowing through the second light emitting diode 234, and hence a bright blink, at a sufficiently high frequency (e.g., on the order of 0.5 - 2 blinks per second) using a relatively low voltage, e.g., 3-12 V.

The circuit topologizes of Figs. 5 and 6 have been demonstrated by the inventors to provide clear detection of a fiber optic signal using a 6V commercially available DC battery as the DC power supply 236. By meeting this need, the fiber optic network device 200 can easily made portable and/or can be installed in the vicinity of the interior network connection point 116 or the termination box 108. Moreover, due to the relatively low cost of the components used in the active service indicator circuit 210, the fiber optic network device 200 provides a low-cost solution for testing fiber optic service. By meeting this need, one or more fiber optic network devices 200 can be provided by a service provider as part of a self-testing kit that allows the customer to determine to determine whether there is active service without requiring a technician and/or expensive testing equipment.

Referring to Fig. 7, a high-level schematic of the active service indicator circuit 204 is depicted, according to another embodiment. In this embodiment, the active service indicator circuit 204 is configured to convey the electronic output signal 213 to a communications terminal 250. The communications terminal 250 can be any of a variety of standard electricized data interface structures such as an ethemet net port, a USB ports, and an HDMI port, to name a few. In this example, the active service indicator circuit 204 includes the photodetection circuit 206 as previously described. The photodetection circuit 206 generates the binary active service signal 212 and feeds it to the communications circuit 207 in the manner previously described. In this example, the communications circuit 207 is configured to convert the binary active service signal 212 into a electronic output signal 213 that is perceptible by an article that is plugged into the communications terminal 250. For example, the electronic output signal 213 can be a modulating bitstream, a steady state electrical potential, or an analog frequency, to name a few. To this end, the communications circuit 207 includes an integrated circuit 252 that is adapted to generate the electronic output signal 213 in the appropriate communication protocol. The integrated circuit 252 can be any of a variety of analog or digital circuits, such as an application specific integrated circuit (ASIC) or a field- programmable gate array, to name a few. In the depicted embodiment, the oscillator circuit 208 as previously described is omitted from the communications circuit 207. However, in other

embodiments, an oscillator circuit substantially similar or identical to the oscillator circuit 208 may be provided if, for example, the electronic output signal 213 is provided to the communications terminal 250 as an oscillating signal.

Spatially relative terms such as“under,”“below,”“lower,”“over,”“upper” and the like, are used for ease of description to explain the positioning of one element relative to a second element. These terms are intended to encompass different orientations of the device in addition to different orientations than those depicted in the figures. Further, terms such as“first,”“second,” and the like, are also used to describe various elements, regions, sections, etc. and are also not intended to be limiting. Like terms refer to like elements throughout the description.

As used herein, the terms“having,”“containing,”“including,”“compri sing” and the like are open-ended terms that indicate the presence of stated elements or features, but do not preclude additional elements or features. The articles“a,”“an” and“the” are intended to include the plural as well as the singular, unless the context clearly indicates otherwise.

Notably, modifications and other embodiments of the disclosed invention(s) will come to mind to one skilled in the art having the benefit of the teachings presented in the foregoing descriptions and the associated drawings. Therefore, it is to be understood that the invention(s) is/are not to be limited to the specific embodiments disclosed and that modifications and other

embodiments are intended to be included within the scope of this disclosure. Although specific terms may be employed herein, they are used in a generic and descriptive sense only and not for purposes of limitation.