Optical fibre fusion splice

Abstract: When effecting a fusion splice between two optical fibres, end parts of the two fibres are introduced transversely into opposite ends of an open-ended channel 3 in a surface 2 of a rigid elongate support member 1 having at a position intermediate of its ends and in the surface a transversely extending open-ended slot 4 for temporarily accommodating the electrodes by which fusion splicing is to be effected. After fusion splicing of the fibres and withdrawal of the electrodes, any space in the channel 3 not occupied by the fusion spliced fibres and the transversely extending slot 4 are filled with a curable material which is permitted or caused to set. A preformed elongate lid 7 is secured to the surface 2 of the support member 1 and the support member and lid provide permanent protection for the fusion splice.

Description: This invention relates to end-to-end fusion splicing of optical fibres. Many techniques differing from one another have been proposed for effecting and end-to-end fusion splice between two optical fibres. An ideal fusion splicing technique should be capable of being readily used in the field by a semi-skilled operator and should reliably and repeatedly produce at any location satisfactory fusion splices. It is an object of the present invention to provide an improved method of effecting an end-to-end fusion splice between two optical fibres, which improved method can be readily and repeatedly effected and substantially reduces the risk that an unsatisfactory fusion splice will be made. One method of forming an end-to-end fusion splice between optical fibres is described in GB-A-2,222,467. In that method end parts of the two optical fibres are introduced into an open-ended channel formed in and extending throughout the length of a preformed substantially rigid elongate support member so that, at a position intermediate of the ends of the support member, the end faces of the optical fibres abut or are spaced a short distance apart, the support member being made of a material which is capable of withstanding the temperature to which it will be subjected during fusion splicing of the fibres and which will have no deleterious effect on the fibres and the support member having at said position intermediate of its ends a transversely extending open-ended slot provided in the surface of the support member and crossing said channel, or transversely opposed apertures opening into said channel, for temporarily accommodating the electrodes by which fusion splicing is to be effected; the electrodes are introduced into said transversely extending slot or transversely opposed apertures and fusion splicing of the adjacent ends of the optical fibres is effected; and, after fusion splicing of the optical fibres has been effected and the electrodes have been withdrawn, the transversely extending slot or transversely opposed apertures and any space in the channel not occupied by the fusion spliced optical fibres are substantially filled with a curable material in a liquid or semi-liquid state and the curable material is permitted or caused to set. The present invention is characterized in that the channel is formed in the surface of the support member and is open to the outside along its length, and the optical fibres are introduced into the channel in a direction transverse to the channel, and in that a preformed elongate lid is secured to that surface of the support member in which the channel lies after any space in the channel has been filled with the curable material. By virtue of the fact that the end part of each optical fibre is introduced transversely into the open-ended channel in a surface of the support member, there is negligible risk of any damage being effected to the end face of the fibre after the fibre has been cleaved and before fusion splicing of the optical fibres is effected. Furthermore, in addition to providing support for the aligned end parts of the optical fibres during the fusion splicing operation, the rigid elongate member also provides permanent protection for the fusion splice between the optical fibres. In addition to the formation of splices, JP-A-55157708 describes a connector for reconstituting (i.e. reinforcing) a spliced fibre, in which the fibre is placed in a connector having a groove lined with a hot-melt adhesive. A cover is positioned over the groove and the connector is heated to fusion bond the fibre to it. As mentioned above, after any space in the channel has been substantially filled with curable material in a liquid or semi-liquid state, a preformed elongate lid is secured to that surface of the support member in which the channel lies. The preformed elongate lid may be made of the same material as the elongate support member. If desired, the preformed lid may be temporarily applied to said surface of the support member after the optical fibres have been introduced into the channel and before fusion splicing is effected to assist in retaining the optical fibres in the channel during fusion splicing. Preferably, the preformed substantially rigid elongate support member is made of a ceramic, vitreous or sintered material. The open-ended channel in a surface of the elongate support member may be of any transverse cross-section suitable for accommodating aligned optical fibres. Preferred cross-sectional shapes include V-,U- and square cross-sectional shapes. Suitable curable materials that may be employed include an adhesive which is cured by ultra-violet radiation and a hot-melt adhesive which sets on cooling. The invention also includes, for use in the improved method as hereinbefore described, a two-part component comprising a preformed substantially rigid elongate support member and an associated preformed elongate lid as defined in claim 8 and as hereinbefore described. The invention is further illustrated by a description, by way of example, of four preferred forms of two-part component for use in effecting an end-to-end fusion splice between two optical fibres and of the improved method of effecting an end-to-end fusion splice between two optical fibres with reference to the accompanying drawing, in which:- Figures 1 and 2, respectively, are an exploded isometric view and an end view of a first preferred form of two-part component, and Figures 3 to 5 are end views of three alternative preferred forms of two-part component. Referring to Figures 1 and 2, the first preferred form of two-part component comprises a preformed rigid elongate support member 1 and, associated with the support member, a preformed elongate lid 7 separately formed with respect to the support member. The elongate support member 1 has in one major surface 2 an open-ended channel 3 of V-shaped cross-section extending throughout the length of the member. Centrally disposed between the ends of the support member 1 is a transversely extending open-ended slot 4 of rectangular cross-section for temporarily accommodating electrodes by which fusion splicing of two optical fibres which have been introduced transversely into a respective one of the two halves of the open-ended channel 3 with their end faces disposed in the transversely extending slot 4 and spaced a short distance apart. The associated preformed elongate lid 7 for closing the channel 3 in the major surface 2 of the support member 1 has on its inner major surface 8 a discontinuous elongate rib 9 which is adapted to engage in the upper part of the channel 3 (but not the slot 4) so as to locate the lid positively with respect to the support member. The support member 1 and preformed lid 7 are made of a ceramic material which is capable of withstanding the temperature to which they will be subjected during fusion splicing of the fibres and which will have no deleterious effect on the fibres. When using the two-part component shown in Figures 1 and 2 in effecting an end-to-end fusion splice between two optical fibres, end parts of the two optical fibres are introduced transversely into the opposite end parts of the open-ended channel 3 in the major surface 2 of the support member 1 so that, at the transversely extending slot 4, the end faces of the optical fibres are spaced a short distance apart. The preformed lid 7 is then temporarily applied to the major surface 2 of the support member 1 to assist in retaining the optical fibres in the channel 3 during fusion splicing. Electrodes are then introduced into opposite ends of the transversely extending open-ended slot 4 and fusion splicing of the adjacent ends of the optical fibres is effected. After fusion splicing of the optical fibres has been effected, the electrodes are withdrawn, the preformed lid 7 is removed and any space in the channel 3 not occupied by the fusion spliced optical fibres and the transversely extending slot 4 are filled with a hot melt adhesive. Before the adhesive has set, the preformed lid 7 is re-applied to the support member 1 so that, on setting of the hot melt adhesive, the lid will be bonded to the support member and the two-part component will provide permanent protection for the fusion splice between the optical fibres. The second preferred form of two-part component shown in Figure 3 comprises of a support member 11 having in one of its major surfaces 12 an open ended channel 13 which has a depth substantially greater than the V-shaped channel 3 of the support member 1 shown in Figures 1 and 2. Centrally disposed between the ends of and extending transversely with respect to the support member 11 and opening into the channel 13 are transversely opposed apertures 14 for temporarily accommodating electrodes by which fusion splicing is to be effected. A preformed lid 17 has on its inner major surface 18 a discontinuous elongate rib 19 which is of greater depth than the rib 9 on the lid 7 shown in Figures 1 and 2 and which engages in the upper part of the channel 13. In the third preferred form of two-part component shown in Figure 4, a support member 21 has in one major surface 22 an open-ended channel 23 with a square cross-section and has, centrally disposed between its ends in the major surface, a transversely extending open-ended slot (not shown) for temporarily accommodating electrodes by which fusion splicing is to be effected. A preformed lid 27 does not have an elongate rib for engaging in the channel 24 and will be bonded to the support member 21 by a film of hot melt adhesive. The fourth preferred form of two-part component shown in Figure 5 is substantially identical to the third preferred form of two-part component shown in Figure 4 with the exception that the open-ended channel 33 in the major surface 32 of the support member 31 is of U-shaped cross-section.

Claims: A method of effecting an end-to-end fusion splice between two optical fibres, wherein end parts of the two optical fibres are introduced into an open-ended channel (3,13,23,33) formed in and extending throughout the length of a preformed substantially rigid elongate support member (1,11,21,31) so that, at a position intermediate of the ends of the support member, the end faces of the optical fibres abut or are spaced a short distance apart, the support member being made of a material which is capable of withstanding the temperature to which it will be subjected during fusion splicing of the fibres and which will have no deleterious effect on the fibres and the support member having at said position intermediate of its ends a transversely extending open-ended slot (4) provided in the surface of the support member and crossing said channel, or transversely opposed apertures (14) opening into said channel, for temporarily accommodating the electrodes by which fusion splicing is to be effected; the electrodes are introduced into said transversely extending slot or transversely opposed apertures and fusion splicing of the adjacent ends of the optical fibres is effected; and, after fusion splicing of the optical fibres has been effected and the electrodes have been withdrawn, the transversely extending slot or transversely opposed apertures and any space in the channel not occupied by the fusion spliced optical fibres are substantially filled with a curable material in a liquid or semi-liquid state and the curable material is permitted or caused to set, characterized in that the channel (3,13,23,33) is formed in the surface of the support member (1,11,21,31) and is open to the outside along its length, and the optical fibres are introduced into the channel in a direction transverse to the channel, and in that a preformed elongate lid (7,17,27,37) is secured to that surface of the support member in which the channel lies after any space in the channel has been filled with the curable material. A method as claimed in Claim 1, wherein the preformed elongate lid is made of the same material as the elongate support member. A method as claimed in Claim 1 or 2, wherein the preformed lid is temporarily applied to said surface of the support member after the optical fibres have been introduced into the channel and before fusion splicing is effected to assist in retaining the optical fibres in the channel during fusion splicing. A method as claimed in any one of the preceding Claims, wherein the preformed substantially rigid elongate support member is made of a ceramic, vitreous or sintered material. A method as claimed in any one of the preceding Claims, wherein the open-ended channel (3,13) in a surface of the elongate support member (1,11) has a cross-section of substantially V-shape. A method as claimed in any one of the preceding Claims, wherein the curable material employed is an adhesive which is cured by ultra-violet radiation. A method as claimed in any one of Claims 1 to 5, wherein the curable material employed is a hot-melt adhesive which sets on cooling. A component for use in the method of effecting an end-to-end fusion splice between two optical fibres as claimed in any one of the preceding Claims, said component comprising a preformed substantially rigid elongate support member (1,11,21,31) having an open-ended channel (3,13,23,33) formed in and extending throughout the length of the member, the support member being made of a material which is capable of withstanding the temperature to which it will be subjected during fusion splicing of the fibres and which will have no deleterious effect on the fibres, and the support member having intermediate of its ends a transversely extending open-ended slot (4) provided in the surface of the support member and crossing said channel, or transversely opposed apertures (14) opening into said channel, for temporarily accommodating the electrodes by which fusion splicing is to be effected characterized in that the channel (3,13,23,33) is formed in the surface of the support member (1,11,21,31) and is open to the outside along its length to allow the fibres to be introduced into the channel in a direction transverse to the channel, and in that the component includes a preformed elongate lid (7,17,27,37) for securing to that surface of the support member in which the channel lies. A component as claimed in Claim 8, wherein the elongate lid has on its inner surface and extending between its ends a rib (9,19) for engaging in the upper part of the channel in the support member.

Inventors: GRIGSBY RICHARD, GRIGSBY, RICHARD
Applicants: BICC PLC, BICC PUBLIC LIMITED COMPANY
Application year: 1991
Main classification: G02B6
IPC codes: G02B6