Apparatus for extracting light from the core of an optical fibre through the cladding and buffer coating thereof and its use in optical fibre splicing

• US 4,696,534 A
• Filed: 07/30/1985
• Issued: 09/29/1987
• Est. Priority Date: 08/08/1984
• Status: Expired due to Fees

• Current Assignee: BICC Public Limited Company
• Original Assignee: BICC Public Limited Company
• Inventors: Saha, Sanjiv
• Primary Examiner(s): Laroche, Eugene R.
• Assistant Examiner(s): Lee, James C.
• Application Number:
  US06/760,675
• Time in Patent Office: 791 Days
• Field of Search: 350/96.15, 350/96.21, 250/227, 356/73.1
• US Class Current: 385/32
• CPC Class Codes: G01M 11/35 in which light is transversely coupled into or out of the fibre or waveguide, e.g. using integrating spheres G01M11/31 takes precedence
• CPC Class Codes: G02B 6/2551 using thermal methods, e.g. fusion welding by arc discharge, laser beam, plasma torch
• CPC Class Codes: G02B 6/2555 Alignment or adjustment devices for aligning prior to splicing
• CPC Class Codes: Y10S 359/90 Methods

Abstract

Apparatus for locally abstracting light from the core of a buffer coated optical fibre, especially a buffer coated single mode optical fibre, suitable for use when monitoring the fusion splicing of optical fibres comprises a body of perspex having at least three faces, an arcuate contact face adapted to bear against a smoothly curved length of buffer coated optical fibre, an exit face through which light entering the body through the contact face can emerge and a reflecting face which will reflect light entering the body through the contact face in a direction towards the exit face. Light emerging from the smoothly curved length of buffer coated optical fibre and passing through the contact face into the body will be directed and reflected towards the exit face from where it can pass into a light detector.

Claims

1. Apparatus for extracting light from the core of an optical fibre through the cladding and buffer coating thereof, which apparatus comprises a body which is made of a substantially rigid transparent material and which has at least three faces, a contact face which is of substantially arcuate shape and which is adapted to bear against a smoothly curved length of buffer coated optical fibre, an exit face through which light emerging from the optical fibre and into the body can pass and a reflecting face which is of substantially arcuate shape and which will reflect light entering the body through said contact face in a direction towards said exit face, the shapes of said contact, reflecting and exit faces and the positions of the reflecting and exit faces relative to the contact face being such that at least a major proportion of light passing from the core of a smoothly curved length of buffer coated optical fibre against which said body bears, through the cladding and buffer coating of the optical fibre and through the smoothly curved contact face into the body will be directed and reflected towards said exit face from where it can pass into a light detector.

2. Apparatus as claimed in claim 1, wherein the smoothly curved contact face of the substantially rigid body has a radius of curvature in the range of 3 to 10 mm.

3. Apparatus as claimed in claim 1, wherein the smoothly curved contact face is of such an arcuate length that it subtends an angle at its centre of curvature lying within the range of 60°

to 120°

.

4. Apparatus as claimed in claim 1, wherein the smoothly curved contact face of the substantially rigid body has a radius of curvature of 4.5 mm.

5. Apparatus as claimed in claim 4, wherein the smoothly curved contact face subtends an angle at its centre of curvature in the range 80°

to 90°

.

6. Apparatus as claimed in claim 1, wherein the reflecting face has a radius of curvature in the range 5 to 10 mm and subtends an angle at its centre of curvature lying within the range 50°

to 60°

.

7. Apparatus as claimed in claim 1, wherein the smoothly curved contact and reflecting faces are contiguous one with the other.

8. Apparatus as claimed in claim 1, wherein the exit face is of substantially planar form.

9. Apparatus as claimed in claim 8, wherein the exit face is contiguous with the reflecting face.

10. Apparatus as claimed in claim 1, wherein the substantially rigid body is made of substantially rigid transparent plastics material.

11. Apparatus as claimed in claim 2, wherein the smoothly curved contact base is of such an arcuate length that it subtends an angle at its centre of curvature lying within the range of 60°

to 120°

.

12. A method of effecting local extraction of light from a buffer coated optical fibre, which method comprises effecting a smooth curve in a part of the length of the buffer coated optical fibre and placing into facial contact with the smoothly curved length of optical fibre a smoothly curved contact face of a body made of a substantially rigid transparent material so that the optical fibre and the smoothly curved contact face are in interfacial contact throughout the length of the smoothly curved contact face, which contact face is one of at least three faces of said body including said contact face, an exit face through which light emerging from the optical fibre and into the body can pass and a reflecting face which is of substantially arcuate shape and which will reflect light entering the body through said contact face in a direction towards said exit face, and directing light passing from the core of the optical fibre through the cladding and buffer coating of the optical fibre and through the smoothly curved contact face of the substantially rigid body into the body towards said exit face, and also towards said reflecting face from where it is reflected towards said exit face, and through said exit face to a light detecting device.

13. A method of effecting a permanent end-to-end splice between two buffer coated optical fibres which comprises arranging the two optical fibres in approximately axial alignment with their neighbouring end faces substantially abutting;

locally injecting light into a smoothly curved length of one of the buffer coated optical fibres adjacent to the proposed splice;

effecting a smooth curve in a part of the length of the other buffer coated optical fibre at a position adjacent the proposed splice by placing into facial contact with the smoothly curved length of optical fibre a smoothly curved contact face of a body made of a substantially rigid transparent material so that the optical fibre and the smoothly curved contact face are in interfacial contact throughout the length of the smoothly curved contact face, which contact face is one of at least three faces of the body including said contact face, an exit face through which light emerging from the optical fibre and into the body can pass and a reflecting face which is of substantially arcuate shape and which will reflect light entering the body through said contact face in a direction towards said exit face;

directing light passing from the core of the optical fibre through the cladding and buffer coating of the optical fibre and through the smoothly curved contact face of the substantially rigid body into the body towards said exit face, and also towards said reflecting face from where it is reflected towards said exit face, and through said exit face to a light detecting device which continuously monitors said light;

moving at least one of the optical fibres transversely with respect to the other until the light monitored by said light detecting device is a maximum; and

permanently securing the abutting ends of the optical fibres together.