This application is being filed on 07 February 2012, as a PCT International Patent application in the name of Tyco Electronics Raychem BVBA, a Belgian national corporation, and Tyco Electronics Corporation, a U.S. national corporation, applicants for the designation of all countries except the U.S., and, Danny Willy August Verheyden, a citizen of Belgium, David Donald Erdman, a citizen of the U.S., Michael Gurreri, a citizen of the U.S., Robert Charles Flaig, a citizen of the U.S., Walter Mattheus, a citizen of Belgium, Jan Vandenbroeck, a citizen of Belgium, Paul Vits, a citizen of Belgium, and Jan Watte, a citizen of Belgium, applicants for the designation of the U.S. only, and claims priority to U.S. Patent Application Serial No. 61/443,921 filed on 17 February 201 1 , and European Patent Application Serial No. 1 1 174678.0 filed on 20 July 201 1, the disclosures of which are incorporated herein by reference in their entirety.

The present invention relates to an optical fiber sealing element comprising means for receiving an optical fiber and comprising a self-healing member. The self- healing member may be opaque, or opaque to a large extent, to the light transmitted by the optical fiber, in which case the optical fiber sealing element also acts as a shutter.

Technical background

An optical fiber connector terminates the end of an optical fiber, and enables connection and disconnection. Optical fiber connections are highly susceptible to contamination by moisture, dust, dirt and other atmospheric borne contaminants. Contamination from particles of dust and dirt will disadvantageously decrease the effectiveness of the optical connection and thus of the entire optical circuit. Cleaning the end face of an optical fiber is usually done manually, by a skilled operator, who may use e.g. a cotton pad to clean the end face of the fiber when it protrudes from the connector.

When an optical fiber connector is disconnected from an adapter for instance, the light beam originally propagating from the connector will leave the connector and emit from the disconnected end. If the emitted light beam is high power and not obstructed, a lasting exposure to such light beam may be harmful to people, especially to the eyes. To avoid exposure to the high-power light beam, a cap may be used to close the unconnected end of the connector.

It is more convenient to use a conventional shutter member integrated in the connector to seal the optical fiber. When a shutter member is used, it will obstruct the light beam emitted from the optical fiber when the optical fiber is disconnected. As a result, exposure to the possibly harmful light beam is avoided. In addition, there is no need to detach the shutter member prior to inserting the connector into e.g. an adapter, as is the case with a cap.

Two such optical fiber connectors may be connected to each other via an adapter. Upon connecting and disconnecting the optical fiber connectors, contamination of the adapter by dust and dirt should be avoided. The adapter may comprise a system for aligning the optical fibers that should also be kept free from contamination. Further, when one of the optical fiber connectors is disconnected from the adapter, the light beam propagating from the other connector may be emitted from the adapter. If the emitted light beam is high power and not obstructed, a lasting exposure to such light beam may be harmful to people, especially to the eyes. To avoid exposure to the high-power light beam, a cap may be used to close the adapter.

Prior art connector assemblies which have shutter systems and sealing diaphragms extending across the connecting ends are disclosed in patent US4109989. Such a diaphragm covered connector provides relatively effective automatic contamination protection and is relatively simple to operate; however it is not suitable for use in all connector applications. For example, the dimensions of an optical fiber are too small and the operation of passing the optical fiber through such a diaphragm, or even through tightly closed slots in such a diaphragm, would damage the optical fiber, thereby rendering the connector assembly unserviceable. Even a thin diaphragm cannot be used for the passing of an optical fiber without resulting in detrimental effects upon the fibers.

Another shutter system and sealing means example is the connector assembly with elastomeric sealing membranes having slits disclosed in patent US441 1491. The slit is of a dimension adequate for receiving optical fiber connectors, but not optical fibers, which are positioned for connecting. When the connector enters the membrane the slit is stretched to permit the passage of the connector and the shutter is manually opened in order to release the optical fiber. When the connector is disengaged the elastomeric sealing membrane relaxes and the slits are closed.

A need still exists for an improved system for sealing an optical fiber that can be used e.g. in connectors or connector assembly systems and for an improved system for connecting, and for aligning, optical fibers.

Summary of the invention

It is an object of the present invention to provide a device and a method for sealing an optical fiber used e.g. in connectors or connector assembly systems.

This object is met by the method and means according to the independent claims of the present application. The dependent claims relate to preferred embodiments of the present invention.

The invention includes an optical fiber sealing element that may be used e.g. in a connector for an optical fiber or in an adapter for connecting two optical fiber connectors to each other. The invention also includes a connector comprising an optical fiber and an optical fiber sealing element in accordance with the invention. The invention further includes an adapter for connecting two optical fiber connectors, wherein the adapter comprises at least one optical fiber sealing element according to the invention. The invention further includes a method for sealing an end face of an optical fiber (from dust, dirt, etc.) using an optical fiber sealing element in accordance with the invention.

The term "fiber" as used herein relates to a single, optical transmission element having a core having a diameter of e.g. 8 μ ^η ι and a cladding having a diameter of e.g. 125 μιτι, wherein the core is the central, light-transmitting region of the fiber, and the cladding is the material surrounding the core to form a guiding structure for light propagation within the core. The core and cladding can be coated with a primary coating usually comprising one or more organic or polymer layers surrounding the cladding to provide mechanical and environmental protection to the light-transmitting region. The primary coating may have a diameter of e.g. between 200 and 300 μπι. The core, cladding and primary coating usually are coated with a secondary coating, a so-called "buffer", a protective polymer layer without optical properties applied over the primary coating. The buffer or secondary coating usually has a diameter between 300 and 1 100 μηι, depending on the cable manufacturer.

The term "light" as used herein relates to electromagnetic radiation comprising the part of the electromagnetic spectrum that is classified by wavelength into infrared, the visible region, and ultraviolet, or to a limited portion of that part of the electromagnetic spectrum, or to a wavelength, as emitted e.g. by a laser device, within that part of the electromagnetic spectrum.

The term "pressured" relates to an applied pressure. When a pressure is applied to a material of a certain volume it is not necessary so that the volume of the material will decrease. Any volume change after pressure is applied depends on the properties of the pressured material.

One preferred embodiment of the invention provides an optical fiber sealing element, that may be used e.g. in an optical fiber connector. The sealing element comprises means for receiving an optical fiber, the optical fiber having a bare end and the bare end having an end face, and the sealing element further comprises a self-healing member for being pierced by the bare end of the optical fiber. The optical fiber sealing element further comprises means for holding the self-healing member. The end of the fiber that is to pierce the member is bare, i.e. the coating layer or layers are removed at the end of the fiber over a certain length, so that the core and cladding remain bare.

A sealing element in accordance with the invention may have the following functions: a sealing function, a cleaning function, and a light-blocking or, in general, a light attenuation function for eye protection. Which functions a particular embodiment of a sealing element has, is determined by the characteristics of the embodiment, especially by the properties of the material that is used for the self- healing member of the sealing element.

When the sealing element is used in e.g. a connector, the sealing element and the parts of the connector may keep the optical fiber isolated from the outside world, so that the optical fiber is protected from contamination by e.g. dust and dirt, i.e. is sealed.

Further, in some embodiments of the invention, the end face of the optical fiber may be cleaned, and this reliably and automatically. When the bare end of the optical fiber pierces the self-healing member of the optical fiber sealing element (e.g. in a connector), the bare end pushes away the material of the self-healing member. This material encloses the bare end, since it is self-healing, i.e. after retracting the bare end, the space left by the retracted end is closed automatically. Dust, dirt or other contaminants possibly present on the end face of the bare end may then be caught in the self-healing member, thus cleaning the end face.

In this document, piercing the self-healing member by the bare end of the optical fiber means that the bare end is inserted in the self-healing member, either up to a position wherein the end face still remains in the self-healing member (a partial piercing), or further, up to a position where the end face is pushed completely through the self-healing member, so that it is completely pierced. Further, piercing means creating an opening in the member, that did not exist before the piercing, i.e. an existing opening such as a slit is not a piercing.

In an embodiment, the end face of the optical fiber in a connector in accordance with the invention is held in the self-healing member when the connector is not in use, i.e. when it is not connected, or, as this is also called in this document, when it is in a non-communication position. Holding the end face of the optical fiber contained in the self-healing member will even better prevent contamination of the end face by dust, dirt or other contaminants. In another embodiment, the end face of the optical fiber is outside of the self-healing member in the non-communication position.

In some embodiments, the optical fiber sealing element is opaque, or opaque to a large extent, to the light transmitted by the optical fiber, in which case the optical fiber sealing element acts as a shutter, and thus has a light-blocking or light attenuation function.

The light transmitted by the optical fiber light may be harmful, especially to the eye; this depends especially on the power and the wavelength of the light. The light transmitted by the optical fiber is usually emitted by a laser. International standard IEC 60825 prescribes what exposure to specific laser light is considered safe. Using IEC 60825 the required attenuation can be determined to decrease an initial power level of a laser source to a power level that is safe for eye protection. This level can then be attained by the use of a self-healing member with appropriate material properties and thickness, for the light transmitted by the optical fiber. 3

Embodiments of an optical fiber sealing element in accordance with the invention may thus have a sealing function, a cleaning function, a light-blocking or light attenuation function, or any combination of these functions.

In an embodiment, the means for holding the self-healing member, that has a first side and a second side opposite to the first side, may comprise a first element, for instance a shroud, and a second element, for instance a shroud lock, wherein the first element contacts the first side of the member and the second element contacts the second side of the member.

In some embodiments, the optical fiber sealing element comprises means for pressuring the self-healing member. The means for holding the self-healing member may include the means for pressuring it. The means for pressuring the self-healing member may enclose the self healing member. The means for pressuring may e.g. be provided with openings to receive the optical fiber. Whether the self-healing member is pressured or not largely depends on the properties of the material used for the self-healing member.

Embodiments of the present invention may be used to connect and/or to align an optical fiber to an optical device. The optical device may be another optical fiber. It may be a light source, such as a LED. It may be a sensor.

A preferred embodiment of the present invention includes an adapter for connecting an optical fiber to an optical device, wherein said optical fiber is part of an optical fiber connector, the optical fiber having a bare end, said adapter comprising an optical fiber sealing element for receiving the optical fiber, wherein said optical fiber sealing element includes a self-healing member for being pierced by the bare end of the optical fiber and at least one holding element for holding said self-healing member.

In one embodiment, the optical device is a second optical fiber connector, the second optical fiber connector including a second optical fiber having a second bare end, wherein the adapter further comprises a second optical fiber sealing element for receiving the second optical fiber, wherein the second optical fiber sealing element includes a second self-healing member for being pierced by the second bare end of the second optical fiber and at least one second holding element for holding said second self-healing member. 12 024183

In accordance with the invention, a preferred embodiment of a method for connecting an optical fiber to an optical device comprises inserting an optical fiber connector, of which the optical fiber is a part, into an adapter, thus piercing a self- healing member of a self-healing element of said adapter by a bare end of the optical fiber.

The invention also includes an adapter for connecting two optical fiber connectors. In some embodiments, the adapter comprises first and second optical fiber sealing elements. Each of the optical fiber sealing elements includes a self- healing member. The adapter may further comprise an index matching material, for instance an index matching gel, contained between the self-healing member of the first sealing element and the self-healing member of the second sealing element. The index matching gel has an index of refraction that closely approximates that of the cores of the optical fibers and is used to reduce Fresnel reflection at the end faces of the bare optical fiber ends. The bare ends of the optical fibers each pierce a self- healing member and make contact in the adapter (the first optical fiber pierces the first member and the second optical fiber pierces the second member). However, it is possible that the bare ends of the optical fibers contact each other over only a limited area of their end faces. The index matching gel then fills up the possible "gaps" between the end faces and thus reduces Fresnel reflections and increases the efficiency of the optical connection and thus of the entire optical circuit.

An adapter in accordance with the invention may be used to connect and/or to align an optical fiber to an optical device. The optical device may be another optical fiber; in case the two optical fibers are part of optical fiber connectors of a different type, the adapter is often called a converter, that then connects two optical fiber connectors of different types to each other. The optical device may be a light source, such as a LED. It may be a sensor. In the two last cases, the adapter is also called a transducer. In embodiments of all these cases, the optical device may be pre-installed (e.g. factory installed) in the adapter. Especially if the optical device is pre-installed, a sealing element that includes a self-healing member may not be required for the optical device, so that the adapter may then comprise a single sealing element with a self-healing member, for the non-preinstalled optical fiber. The adapter can then thus be protected from contamination. On the other hand, if the adapter is to receive two non-preinstalled optical fibers, it preferably comprises two sealing elements, each having a self-healing member, in order to be protected from contamination.

Preferably, the adapter comprises an alignment system, to align the optical fiber to the optical device. This alignment system is then also protected from contamination by the one or more self-healing members. It is preferred that the alignment system is self-aligning and passive, i.e. the optical fiber is just inserted, and the alignment is done automatically and without the need for an external power source.

Various embodiments of an optical fiber sealing element in accordance with the invention have different advantages. That the member is self-healing means that, after retracting the bare end of the optical fiber, the space in the self-healing member that is freed by the retraction is occupied again, and automatically, by the self- healing member. If an opening through the self-healing member is made by the bare end of the optical fiber, it is thus closed automatically. If the self-healing member is opaque or opaque to a large extent to the light transmitted by the optical fiber, the optical fiber sealing element automatically acts as a shutter, and, if the light transmitted by the optical fiber is harmful, the optical fiber sealing element may thus provide protection. As discussed already above, an optical fiber sealing element according to the invention may automatically clean the end face of the optical fiber. Inserting a bare end of an optical fiber in an optical fiber sealing element, and subsequently retracting it, can be repeated a plurality of times, e.g. tens of times, such as fifty times and more, so that, when used in an optical fiber connector, very many disconnections and connections can be done reliably, and this without damaging the optical fiber. When used in an adapter containing index matching gel as discussed above, the index matching gel is confined between the two self-healing elements. In preferred embodiments of the invention, when disconnecting a connector from the adapter, residual index matching gel possibly present on a bare end of the optical fiber is removed by the self-healing member and hence is not lost. Brief description of the drawings

Further features of the present invention will become apparent from the drawings, wherein: Fig. la shows an optical fiber sealing element according to an embodiment of the invention;

Fig. lb shows a self-healing member according to an embodiment of the invention; Fig. lc represents an embodiment of a shroud lock;

Figs. 2a and 2b are schematic representations of an embodiment of a connector in accordance with the invention;

Fig. 3 is a schematic representation of an adapter according to one embodiment of the invention;

Fig. 4 is a schematic representation of an embodiment of an adapter according to the invention, connecting two connectors.

Detailed description of preferred embodiments

The present invention will be described with respect to particular embodiments and with reference to certain drawings but the invention is not limited thereto but only by the claims. The drawings described are only schematic and are non-limiting. In the drawings, the size of some of the elements may be exaggerated and not drawn on scale for illustrative purposes. Where the term "comprising" is used in the present description and claims, it does not exclude other elements or steps. Where an indefinite or definite article is used when referring to a singular noun e.g. "a" or "an", "the", this includes a plural of that noun unless something else is specifically stated.

The term "comprising", used in the claims, should not be interpreted as being restricted to the means listed thereafter; it does not exclude other elements or steps. Thus, the scope of the expression "a device comprising means A and B" should not be limited to devices consisting only of components A and B. It means that with respect to the present invention, the only relevant components of the device are A and B.

Furthermore, the terms first, second, third and the like in the description and in the claims, are used for distinguishing between similar elements and not necessarily for describing a sequential or chronological order. It is to be understood that the terms so used are interchangeable under appropriate circumstances and that the embodiments of the invention described herein are capable of operation in other sequences than described or illustrated herein. Moreover, the terms top, bottom, over, under and the like in the description and the claims are used for descriptive purposes and not necessarily for describing relative positions. It is to be understood that the terms so used are interchangeable under appropriate circumstances and that the embodiments of the invention described herein are capable of operation in other orientations than described or illustrated herein.

In the drawings, like reference numerals indicate like features; and, a reference numeral appearing in more than one figure refers to the same element. The drawings and the following detailed descriptions show specific embodiments of an optical fiber sealing element.

Fig. la shows an optical fiber sealing element 5 comprising a self-healing member 1. The member 1 is held by a shroud 3 and a shroud lock 2. The sealing element 5 has means for receiving an optical fiber, i.e. opening 12 in shroud lock 2 and opening 13 in shroud 3. The bare end 14 of an optical fiber 4 may pass through opening 12, through the member 1, and then through opening 13, to make a connection, e.g. with another optical fiber.

In one embodiment, shown in Fig. la, the end face 15 of the bare end 14 of the optical fiber 4 is held inside the self-healing member 1 when the optical fiber is not in use, i.e. when it is not connected, or, put otherwise, when it is in the non- communication position. Holding the end face 15 of the optical fiber contained in the self-healing member 1 ensures that no dust, dirt or other particles contaminate the end face 15. In another embodiment, the end face of the optical fiber may be outside of the self-healing member 1 (as illustrated in Fig. 2a) in the noncommunication position.

When the optical fiber is retracted, the space in the self-healing member 1 that is freed by the retraction is closed automatically, thus sealing the optical fiber. The shroud 3 also protects the optical fiber. When the bare end of the optical fiber is inserted in the member, or when it is retracted, it may be cleaned automatically by the member, as explained already above.

In some embodiments in accordance with the invention, the self-healing member 1 is pressured by the shroud 3 and the shroud lock 2; e.g. after the member 1 is mounted in the shroud 3, the shroud lock 2 is locked in place, thus pressuring 2012/024183

the member. In general, more than two elements may be used to pressure the member 1.

Fig. lb shows a separate self-healing member 1 in its pressured state as used in the sealing element 5 shown in Fig. la. In the sealing element 5, shroud lock 2 contacts the first side 22 of the member 1 , while shroud 3 contacts the second side 23, opposite to the first side 22, of the member 1. Fig. l c shows shroud lock 2 with its opening 12.

The self-healing member may e.g. be a cold-applied, pre-cured silicone gel, e.g. Dow Corning GT-4201, which is a soft silicone-gel, can be used and which requires a minimum contact insertion force of 0.1 N. In other embodiments e.g. Dow Corning GT-6201 can also be used which is a harder, silicone-gel with better overall handling characteristics and advantageously suitable for automated assembly.

Preferably the gel is provided as a three-layer laminate: the middle layer is the thick, soft silicone gel with excellent sealing capabilities under compression; the thin top and bottom layers allow easier handling of the member during the manufacturing process and protect the gel from any contamination before use.

The self-healing member comprises self-healing characteristics which allow for multiple insertions and extractions of the connector contact while maintaining a seal with the contact. Mechanical, electrical, chemical and thermal testing, as well as use on production connectors, has shown that the self-healing member form a reenterable, tight environmental seal.

In the embodiment shown in Fig. l a and l b, the self-healing member 1 may have a diameter of 3 mm and a thickness of 1.5 mm. If GT-4201 is used, it may be pressured such that the thickness is e.g. 1 mm after pressuring.

Figs. 2a and 2b schematically show an embodiment of a connector 6 comprising an optical fiber sealing element 5, as described above. In Fig. 2a, the optical fiber 4 with its bare end 14 is in a retracted state (i.e. in the noncommunication position). Fig. 2b shows the connected state: the bare end of the optical fiber 4 has passed through the opening 12 of the shroud lock 2, has pierced member 1 completely, and has passed through the opening 13 of the shroud 3, so that the optical fiber may now contact another optical fiber and establish communication. As discussed above, in another embodiment, shown in Fig. l a, when the optical fiber is retracted, it is retracted only so far that the end face 15 of 2012/024183

the optical fiber 4 is still contained in the self-healing member 1. In this noncommunication position, the end face 15 is protected from contaminants.

Fig. 3 schematically illustrates an embodiment of an adapter 10 for connecting a first optical fiber connector 61 to an optical device 60. In Fig. 3, the optical device 60 is represented as another optical fiber connector, that is pre- installed in the adapter 10. The first optical fiber connector 61 is not pre-installed, which is indicated by the double arrow 30: the first optical fiber 61 can be connected to and disconnected from the adapter 10.

The adapter 10 includes a sealing element 51 that comprises a self-healing member 71. The self-healing member 71 is held by a first part 91 of the housing of the adapter, a second part 92 of the housing, and two alignment elements 80. Openings are left for receiving a bare end 14 of the optical fiber 41 of connector 61. A central opening in the adapter receives the bare end 14 and contains an index matching material 1 1 (for clarity, the size of this opening is exaggerated in Fig. 3).

The self-healing member may e.g. be a cold-applied, pre-cured silicone gel, e.g. Dow Corning GT-4201. The self-healing member 1 may have a thickness of 1.5 mm. If GT-4201 is used, it may be pressured such that the thickness is e.g. 1 mm after pressuring.

Making a connection by means of the embodiment of the adapter 10 illustrated in Fig. 3 may be done as follows. The first connector 61 is inserted in the adapter 10. The bare end 14 of the optical fiber 41 of the first connector 61 completely pierces the first self-healing member 71 of the first optical fiber sealing element 51 of the adapter (and may thus be cleaned) and is covered by index matching material 1 1 , and connected to optical device 60.

Fig. 4 schematically illustrates an embodiment of an adapter 100 for connecting two optical fiber connectors 61, 62. The adapter 100 includes a first 51 and a second 52 sealing element that comprise a first 71 respectively a second 72 self-healing member. The self-healing members 71 and 72 are held by a first part 91 of the housing of the adapter, a second part 92 of the housing, and two elements 8. Openings are left for receiving a bare end of an optical fiber at both sides of the adapter. A central opening in the adapter receives both bare ends 14 of the fibers and contains an index matching material 1 1 (for clarity, the size of this opening is P T/US2012/024183

exaggerated). The index matching material 1 1, e.g. an index matching gel, is contained between the self-healing members 71 and 72.

Making a connection by means of the embodiment of the adapter 10 illustrated in Fig. 4 may be done as follows. The first connector 61 is inserted in the adapter 10. The bare end 14 of the optical fiber of the first connector 61 completely pierces the self-healing member 1 of the optical fiber sealing element 5 of the first connector 61, and may thus be cleaned from possible contaminants. The bare end 14 then completely pierces the first self-healing member 71 of the first optical fiber sealing element 51 of the adapter (and may thus be cleaned) and is covered by index matching material 1 1. Then, the second connector 62 is inserted analogously at the other side of the adapter 10, and a connection is made. When e.g. the first connector 61 is disconnected, the bare end 14 of the first connector is retracted and the hole that was made in the first self-healing member 71 of the adapter 100 is closed automatically. The index matching material 1 1 may thus remain in the adapter.

In the embodiment shown in Fig. 4, the first 61 and the second 62 connector both comprise an optical fiber sealing element 5. This is however not required; an adapter in accordance with the invention may also connect optical fibers that do not have an optical fiber sealing element.

Further, an adapter in accordance with the invention may also comprise at least one, preferably at least two optical fiber sealing elements according to the present invention, but no index matching material. Such an adapter may have a sealing function (keeping dust, dirt and other contaminants out of the adapter), a cleaning function, a light-blocking or light attenuation function, or any combination of these functions.

It is to be understood that this invention is not limited to the particular features of the means and/or the process steps of the methods described as such means and methods may vary. It is also to be understood that the terminology used herein is for purposes of describing particular embodiments only, and is not intended to be limiting. It must be noted that, as used in the specification and the appended claims, the singular forms "a" "an" and "the" include singular and/or plural referents unless the context clearly dictates otherwise. It is also to be understood that plural forms include singular and/or plural referents unless the context clearly dictates otherwise. It is moreover to be understood that, in case parameter ranges are given which are delimited by numeric values, the ranges are deemed to include these limitation values.

The invention is defined by the appended claims.