FR2497966A1 - Pin and socket terminals for fibre optic cables - with pin contg. spring wire for aligning fibres and socket contg. helical spring supporting free end of fibre - Google Patents

Abstract

A pin terminal (12) and a socket terminal (62) for coupling the free ends of a pair of optical fibre are adapted for mounting in respective connector members (10,18) of the multiple terminal type. The pin terminal (12) has an optical fibre cable (14) secured at the rearward end with the fibre (50) extending partially through a channel (32). The socket terminal (62) has a cable (16) secured at its rearward end with the free end of the fibre (52) extending partially through the socket terminal. The socket terminal has a coil spring for aligning the free end of the fibre with the central axis of the socket. When the pin terminal is telescopically inserted into the socket terminal, the fibre (52) enters the channel (32) which includes self-aligning devices for the fibres.

Description

 The present invention relates to connectors for optical fiber cables and, more particularly, to a connector arrangement with cooperating male and female sockets for optical fiber cables.

 In optical systems using optical fibers to transmit signals by means of light energy, it is often necessary to couple two fibers end to end to achieve continuity of the signal transmission path. Optical fibers are very small in diameter and fragile in nature. Conventionally, an optical fiber cable comprises an optical fiber covered with a plastic sheath intended to protect the fiber during handling during installation and to remove it from its environment. A typical single-filament cable consists of a glass fiber a few hundredths of a millimeter in diameter and a protective sheath with a diameter of a few tenths of a millimeter. To facilitate repeated connections and disconnections of one or more pairs of fibers , it is desirable to use separable connectors having one or more pairs of cooperating sockets, as in the case of connectors used in the electronics industry.

 A connector for fiber optic cables must allow precise alignment of the pairs of fibers to be connected and provide support for the cable sheath in order to relieve the fiber from stresses. I.e connector must be provided with sockets for the pairs of fibers to be connected capable of withstanding repeated connections and disconnections and of construction nevertheless simple and inexpensive.

 According to the prior art, connectors for optical fiber cables are known which use plugs of the male and female type. Such an arrangement is described in US Patent No. 4,410,366. In the connector of this patent, each fiber or bundle of fibers is provided with a special termination which has one end coming flush with the end of the fiber or the bundle of fibers.

The termination intended for a fiber or a bundle of fibers is placed in a female socket of a connector member and the termination intended for the other fiber or the other bundle of fibers is arranged in a tubular male socket intended for s plug into the socket in order to juxtapose these end-to-end terminations.

 According to the prior art, single optical fiber cables are also known, coupled end to end by attaching a ferrule to the end of the fiber and by aligning and mechanically connecting the ferrules together. In particular, the fiber is enclosed in the ferrule so that the end of the fiber comes flush with the end of the ferrule.

Two fibers are coupled by placing the respective ferrules end to end. This type of connector is described in American patents NO 4,087,158 and 4,090,778.

 According to the prior art, there is also known a connector for optical fiber cables in which the fibers are aligned by adapter terminations which each supports a respective cable with the free end of the protruding fiber. In a connector of this type, the free ends of the corresponding pairs of optical fibers are arranged in a V-groove on one of the terminations while a support means on the other termination bears against the fibers to keep them in alignment in the V-groove. This type of arrangement is described in US Pat. Nos. 3,885,859 and 4,088,386.

 An object of the present invention is to provide a connector arrangement for optical fiber cables of the male and female plug type which overcomes certain drawbacks of the previously known arrangements.

 According to the present invention there is provided a connector arrangement with cooperating sockets intended for optically coupling a pair of fiber optic cables, comprising a male socket having a cylindrical body and a female socket having a cylindrical sleeve having a front end portion intended for slidingly receiving the cylindrical body of the plug in telescopic relation; the cylindrical body has an axial channel extending from its rear end to its front end; and there is provided a coaxial means for fixing a first fiber optic cable to the rear end of the cylindrical body of the plug so that a free end portion of the fiber partially extends into the channel, means coaxial to secure a second fiber optic cable to the rear end of the cylindrical sleeve of the socket so that a free end portion of the second fiber partially extends into the cylindrical sleeve, and means for aligning the free end part of the second fiber with the central axis of the cylindrical sleeve, this alignment means being retractable due to its engagement with the cylindrical body of the plug, so that the free end part of the second fiber enters the front end of the channel when the male connector comes into engagement with the female connector and the free ends of the first and second optical fibers come into coupling relationship.

 This object and these characteristics and others of the present invention will appear more clearly from the detailed description which follows as well as from the appended drawings, it being understood that these are given only by way of non-limiting examples.

In the drawings:
Fig. 1 shows a plug according to the invention for a connector for optical fiber cables;
Fig. 2 is a partial perspective view of the male plug;
Fig. 3 is a sectional view of the male plug;
Fig. 4 is a sectional view taken along line 4-4 of FIG. 3;
Fig. 5 shows a socket according to the invention for a connector for optical fiber cables;
Fig. 6 shows a male plug and a female plug in engagement relationship;
Fig. 7 shows a multiple socket connector;
Fig. 8 shows another form of socket construction; and
Fig. 9 shows a male plug and a female plug opposite.

 Referring now to the drawings, there is shown an embodiment of the invention intended for a connector for optical fiber cables of the separable type with multiple pairs of sockets.

 Fig. 1 is a partial view of a separable connector intended for the connection of multiple pairs of fiber optic cables. This connector, except for the male and female sockets, is of the same type as the connectors used for electronic circuits.

A connector member or casing 10 of cylindrical shape supports multiple male sockets 12 in order to couple a fiber optic cable 14 to a corresponding cable 16 provided in a cooperating connector member or casing 18 (Fig. 5). As it appears in FIG. 1, the male plug 12 is supported in the casing 1G by an assembly having an interfacial seal 20 and a pair of linings 22 and 24 having between them a plug retaining member 26. The support of the male plug 12 and the cable 14 will be described more fully below.

The male plug 12 is shown in detail in
Fig. 2, 3 and 4. This socket is intended to receive the free ends of a pair of optical fibers 50 and 52 which are inserted into the socket end to end according to a precise alignment. The male connector 12 comprises an elongated body 30 of circular section preferably made of molded plastic. This socket defines an axial channel 32 extending from one end to the other of the body 30. The channel 32 has at its lower part a V-shaped notch 34 which is substantially coaxial with the body 30. The channel 32 has two walls spaced parallel 36 and 38 which extend from the V-shaped notch 34 to an upper wall 40. An orifice 42 is provided in the upper wall 40 at the rear end of the body 30 and a housing 44 is provided in the front end of this body for a purpose that will appear later. The body 30 is provided with a chamfered orifice 46 at the rear end and with a chamfered orifice 48 at the front end, these orifices forming the inlets of the channel 32 in order to facilitate the insertion of an optical fiber at each end. The body 30 is also provided with an annular flange or shoulder 53 intended for mounting, as will appear later.

The channel 32 is intended to receive the pair of optical fibers 50 and 52 end to end. The fibers are adapted to be placed in axial alignment in the notch in
V 34. In order to guide and maintain the fibers in alignment and in engagement with the notch in V 34, a retaining means formed by an elastic thread 54 is placed in the channel 32. The elastic thread 54 is provided with a central part 56 which, as shown in FIG. 2, is substantially straight and extends axially with the fibers 50 and 52 in place. The central part 56, in its free state, as shown in FIG. 3, is slightly curved and occupies part of the channel in which the fibers 50 and 52 have been inserted. The elastic thread 54 is also provided with an obliquely extending end part 58 and with another end part. extending obliquely 60, these two end parts being in the same plane. The elastic thread 54 is preferably installed in the body 30 by inserting the end portion 58 into the front end of the body 30 and allowing it to flex so as to assume the position shown in FIG. 3.

 When the optical fiber 50 of the cable 14 is inserted into the rear end of the body 30, as it appears in FIG. 3, the end of the fiber is guided by the chamfered orifice 46 in the channel 32. When the fiber enters the channel, it comes into engagement with the curved part of the elastic thread 54 near the junction of the part end 58 and central part 56. This engagement imposes a slight force resistant to the insertion of the fiber and the elastic thread deviates elastically from the path of the fiber while exerting a lateral force on it which the seat in the V-shaped notch 34. The fiber 50 is partially inserted into the body 30 substantially up to the midpoint and the fiber is fixed to the male plug 12 in a manner which will appear subsequently. adapted to receive the other optical fiber 52 by insertion of an end at the front end of the body 30. The fiber 52 is inserted in the same way as the fiber 50 up to the point for which it abuts against the end of fiber 50. Fibers 50 and 52 are thus positively seated in the notch e in V 34 under the influence of the elastic thread 54 and are thus maintained in a precise axial alignment. Any excessive movement of the fiber 52 during its insertion into the channel 32 will be taken into account by the slight flaming of this fiber 52 or of the fiber 50 at a point outside the body 30.

 As shown in FIG. 9, the male connector 12 is intended to cooperate with a female connector 62.

Before describing the latter, the mounting of the male plug on the fiber optic cable 14 will be described. The cable 14 comprises the optical fiber 50 and a protective sheath 64 made of plastic. To install the male plug 12, the sheath 64 is stripped from a free end of the fiber 50. A fitting 66 is intended to connect the male plug 12 to the cable 14 and to fix the fiber 50 in a fixed position relative to this plug and fixing the sheath 64 in order to reduce the force acting on the fiber. The lining 66 comprises an internal sleeve 68 of metal which is mounted on the body 30 by a rolled rim 70 which is in engagement with the annular shoulder 53 of this body. The lining 66 also comprises an external sleeve 72 of metal is arranged coaxially with the internal sleeve 68 but spaced therefrom so that this space receives the end of the sheath 64. An elastomer body or ring 74 is placed in the internal sleeve 68 to prevent the displacement of the fiber 50 by relative to the male plug 12. As it appears in FIG. 9, the ring 74 has a passage intended to receive the fiber 50. With the lining 66 in place, the external sleeve 72 is pinched radially against the internal sleeve 68 which, in turn, is pinched against the ring 74, so that the fiber 50 and the sheath 64 are firmly held by the lining 66. The latter is shown before pinching in FIG. 9 and after pinching in FIG. 1 under reference number 66 '.

 Referring again to FIG. 9, it can be seen there that the female socket 62 is arranged in alignment cooperating with the male socket 12. The female socket 62 comprises a metal sleeve 80 intended to receive in its passage the male socket 12 telescopically with an adjustment clearance .

The sleeve 80 is provided at its front end with a chamfered orifice 82 intended to facilitate penetration of the male plug 12. The female plug 62 is intended to be mounted on the end of the fiber optic cable 16 by means of a gasket 84. The latter comprises an internal sleeve 86 having an external annular rim or shoulder 88. The sleeve 80 is mounted on the internal sleeve 86 by means of a rolled up rim 90 which comes into engagement with the shoulder 88. The lining 84 also has an external sleeve 92 which is arranged coaxially with the internal sleeve 86 but spaced therefrom so that this space receives the end of the sheath 94 of the cable 16. An elastomer body or ring 96 is placed in the sleeve internal 86 to prevent movement of the fiber 52 relative to the socket 62 in the same manner as for the ring 74. The external sleeve 92 is pinched radially against the internal sleeve 86 which, in turn, is pinched against the ring 96, from s ort that the fiber 52 and the sheath 94 are firmly held by the lining 84.

 The free end of the fiber 52 partially extends into the sleeve 80 of the socket 62. Due to its flexibility, the optical fiber tends to fall at its free end. In order to provide support for this end, a helical spring 100 is disposed in the sleeve 80 so as to surround the fiber. When the spring 100 is in its free state, as shown in FIG. 9, the free end of the fiber 52 is held by the spring in the vicinity of the central axis of the socket 62.

 When the male connector 12 is inserted into the female connector 62, the free end of the fiber 52 penetrates into the channel 32 of the male connector. The spring 100 is compressed by the male plug towards the rear of the female plug and the end of the fiber 50 abuts against the end of the fiber 52. The length of the optical fibers is such that their ends come into engagement before the male plug comes to the bottom of the female plug. In the case where the stop of the fibers occurs before the male plug is completely inserted, the fibers take into account the excess displacement by a safe buckling of the part of the fibers not supported. With the male plug and the female plug in engagement relationship, the fibers 50 and 52 are kept in alignment by the alignment means described in connection with FIGS. 2, 3 and 4.

Another embodiment is shown in FIG. 8. In this embodiment, the female socket comprises a cylindrical sleeve 80 'having an annular mounting shoulder 81. The female socket 62' of this embodiment is mounted on the fiber optic cable 16 by means of a fitting. 84 'similar to the trim 84 of the
Fig. 9. The lining 84 'comprises an internal sleeve 86' forming an integral part of the sleeve 80 '. An outer sleeve 92 'is arranged coaxially with the inner sleeve 86' but spaced therefrom so that this space receives the sheath 94 of the cable 16. The fiber 52 s1 extends in the inner sleeve 86 'and an elastomer body 102 is fixed inside the sleeve 80 ′. A metal sleeve 104 which surrounds the body 102 is pinched against the latter so that the body 102 is firmly fixed. A helical spring 100 'is arranged in the sleeve 80' so as to surround the fiber 52 with two groups of turns on either side of the body 102. In this embodiment, the insertion of the male plug 12 in the socket 62 'compresses the spring 10O' and the ends of the fibers come into engagement. Any excessive movement of the plug causes the fibers to buckle, as described above. The buckling of the fiber 52 is assisted by the force of the male grip exerted against the elastic body 102. This condition is desirable especially with regard to relatively rigid optical fibers, such as those of large dimension.

 Fig. 5 shows a female socket 62 "mounted in a connector member 18. The female socket 62" is substantially the same as the socket 62 'in FIG. 8, except that the elastomer body 102 is not used. On the contrary, the fiber 52 is held securely on the socket by means of an elastomer body 74 'provided in the sleeve 68', as described in connection with FIG. 9. The other parts of the socket 62 "are substantially the same as the corresponding parts of the socket 62 'in FIG. 8 and the same reference numbers are used. The socket 62" is mounted in the sleeve 18 of connector by means of a fitting 110 The socket 62 "is fitted in an axial hole 112 made in the fitting 110 and the front end of the socket 62" sits against a shoulder 114 provided at the front end of the filling. The socket 62 "is retained in the hole 112 by a retaining member 116 contained in the sleeve 18 against the rear end of the lining 110. The retaining member 116 is provided with an orifice 118 in which extends the 62 "socket. The orifice 118 is surrounded by a plurality of retaining fingers 120 which are disposed behind the mounting shoulder 81 of the socket 62 "and which hold it in place in the lining 110.

 The male plug 12 is mounted in the connector sleeve 10 in a manner similar to that just described. Referring again to FIG. 1, it can be seen that the male plug 12 is mounted in the linings 22, 24 and in the retaining member 26. It should be noted that the male plug 12 is substantially of the same construction as that described in connection with FIGS. 2, 3, 4, 5 and 9 and the parts are designated by the same reference numbers. The male connector 12 extends into a hole in the lining 22 and the mounting shoulder 70 of the male connector sits against a shoulder 120 of the lining 22. The front end of the male connector 12 extends in the interfacial joint 20 for engagement with a corresponding socket. The socket 12 is held in place by the retaining member 26 which has an orifice 122 surrounded by retaining fingers 124. These are arranged behind the mounting shoulder 70 and hold the male plug 12 in position in the lining 22. The cable 14 extends from the rear end of the male plug 12 in the lining 24.

 As shown in the partial view of FIG. 7, the connector member or sleeve 10 comprises multiple male sockets 12. Likewise, the connector member 18 comprises multiple female sockets 62 "each of which corresponds to a male socket 12. Consequently, when the connector members 10 and 18 are in engagement relationship, each male connector 12 enters a corresponding female connector 62 ". This relationship is shown in Fig. 6.

It should be noted that the pair of optical fibers 50 and 52 are brought into precise axial alignment by the means for aligning the male plug when the latter enters the female plug. The connector members 10 and 18 can be repeatedly connected and disconnected and the corresponding male and female sockets will be reconnected each time with a self-alignment of the optical fibers.

Claims (11)

 1. Connector arrangement with cooperating plugs for optically coupling a pair of fiber optic cables, comprising a male plug (12) having a cylindrical body (30) and a female plug (62) having a cylindrical sleeve (80) having a part front end for slidingly receiving the cylindrical body (30) of the plug (12) in telescopic relation, characterized in that the cylindrical body (30) has an axial channel (32) extending from its end rear at its front end, and in that there is provided a coaxial means (66) for fixing a first fiber optic cable (14) (50) to the rear end of the cylindrical body (30) of the male plug ( 12) so that a free end portion of the fiber (50) partially extends into the channel (32), coaxial means (84) for fixing a second fiber optic cable (16) to the rear end of the cylindrical sleeve (80) of the socket (62) so that an end portion l ibre of the second fiber (52) extends partially into the cylindrical sleeve (80), and means (100; 100 ', 102, 104) for aligning the free end portion of the second fiber (52) with the 'central axis of the cylindrical sleeve (80, 80'), this alignment means (100 ;; 100 ') being retractable due to its engagement with the cylindrical body (30) of the male plug (12), so that the free end part of the second fiber (52) enters the front end of the channel (32) when the male plug (12) engages with the female plug (62) and when the free ends of the first ( 50) and the second optical fiber (52) come in coupling relationship.  2. Connector arrangement according to claim 1, characterized in that the means (100; 100 ', 102.104) for aligning the free end part of the second optical fiber (52) comprises a helical spring (100; 100') arranged coa xially in the cylindrical sleeve (80) of the socket (62).  3. Connector arrangement according to claim 1, characterized in that each coaxial means (66; 84) for fixing a respective fiber optic cable (14; 16) comprises internal (68; 86) and external (72; 92) coaxial sleeves. ) intended to receive between them a sheath (64; 94) of a respective fiber optic cable (14; 16) and an elastomer ring (74; 96) 96) placed in the internal sleeve (68; 86), the internal (68; 86) and external (72; 92) sleeves being pinched against the ring (74; 96) to retain the fiber (50; 52) and the sheath (64; 94) of this respective cable (14; 16) .  4. Connector arrangement according to claim 3, characterized in that the cylindrical body (30) of the male connector (12) has an external annular shoulder (53) in the vicinity of its rear end, the internal sleeve (68) being fixed to this shoulder (53) by a rolled up rim (70).  5. Connector arrangement according to claim 3, characterized in that the cylindrical sleeve (80) of the socket (62) has a rolled up rim (90) at its rear end, the internal sleeve (86) being fixed to this rolled up rim (90) by an external annular shoulder (883.  6. Connector arrangement according to claim 1, characterized in that the front end of the cylindrical body (30) of the male connector (12) defines a chamfered orifice (48) in alignment with the channel (32).  7. connector arrangement according to claim 1, characterized in that there is provided a means (54) for maintaining a significant length of the end portions of the two fibers (50,52) inserted in the channel (32) so that those -there are end to end in alignment, this means (54) occupying a part of the channel (32) opposite this significant length and a wall (34) of the channel and being displaced laterally in an elastic manner by the insertion fibers (50,52) in the channel, so that this means (54) laterally biases the substantial length of the end portions of the two fibers (50, 52) so that they come to align as well as sit against this wall (34) of the channel (32).  8. Connector arrangement according to claim 7, characterized in that said wall (34) of the channel is its bottom (34), which has a V-section.  9. Connector arrangement according to claim 8, characterized in that said holding means (54) comprises an elastic wire (54) extending axially in the channel (32).  10. A connector arrangement according to claim 9, characterized in that the channel (32) has two parallel side walls (36, 38) extending from its V-shaped bottom (34) and an upper wall (40) intended to support the ends of the elastic thread (54).  11. A connector arrangement according to claim 10, characterized in that the elastic wire (54) has a central part (56) extending axially and end parts (58,60) obliquely extending the central part (56) in moving away from the V-shaped bottom (34) of the channel (32), the junctions of the oblique parts (58,60) with the central part (56) being curved, so that the wire (54) is moved elastically by a cam effect when inserting one or more fibers (50,52).