Optical fibre locating apparatus

Abstract: Fibre locating apparatus to facilitate alignment of an optical fibre comprises accurately aligned silica blocks 1, 2 and 3 respectively providing a fibre guiding 'V' groove 4, a perpendicular facing surface 10 and a mounting 7 for a mirror or other planar signal receiving surface. The apparatus allows rapid re-alignment of fibre ends when optical systems (e.g. fibre lasers) require reconfiguration.

Description: The present invention relates to optical fibre locating apparatus and in particular to such apparatus for locating an optical fibre with respect to a planar surface. Techniques for cleaving optical fibres to ensure that the cleaved end is perpendicular are now well established. In setting up optical apparatus such as fibre lasers or fibre amplifiers it is often necessary to align the fibre with an article which may be in the form of a planar member such as a semi-transmitting mirror or a cover shield. Such alignment requires extreme accuracy and may involve minute adjustments using several micrometer screws such as when using a "New Waveguide Positioning System" manufactured by Photon Control Ltd, of Cambridge, UK. As may be appreciated this set-up procedure can take several hours. Accordingly if a system requires reconfiguration, for example, to use a different fibre or to change the transmission frequency of a mirror a large time overhead may be incurred. It is an object of the present invention to provide optical fibre locating apparatus which significantly reduces the difficulty of aligning a fibre end with a planar surface. According to the present invention there is provided optical fibre locating apparatus for adjusting an optical fibre perpendicular to a planar surface of an optical component, said optical fibre locating apparatus comprising first block means having a guide surface which includes a "V"-groove arranged to receive and to guide an optical fibre and having a first abutting surface, second block means having a second abutting surface which abuts said first abutting surface of said first block means, a third abutting surface perpendicular to said "V"-groove, and an aperture arranged such that an optical fibre guided along said "V"-groove can pass through said aperture, and mounting means having a fourth abutting surface which abuts said third abutting surface of said second block means, on which mounting means said optical component can be mounted such that said planar surface of said optical component abuts said third abutting surface and is located with respect to said aperture such that an optical fibre guided along said "V"-groove abuts said planar surface perpendicularly. Preferably each of the block means comprises a silica block. The mounting means may comprise a further block having a 'V' shaped channel adapted to receive an optical component in the form of a slide in block having a signal receiving planar surface. The 'V' shaped channel may be offset laterally with respect to the 'V' groove whereby an optical component having a circular cross section may be rotated such that the part on the planar surface at which light emitting from a fibre is received may be varied. Optical fibre locating apparatus in accordance with the invention will now be described by way of example only with reference to the accompanying drawing of which: Figure 1 is a perspective view of the component parts of the apparatus prior to final assembly; Figure 2 is a perspective view of one of the parts of Figure 1 showing a further detail; Figure 3 is a part cross sectional view on the line III - III of Figure 2; Figure 4 is a perspective view of another of the parts of Figure 1 showing a manufacturing detail; Figure 5 is a front elevation of the apparatus of Figure 1 after final assembly; and Figure 6 is a side elevation of the apparatus of Figure 1 after final assembly. Referring to the drawing the support comprises three accurately machined silica blocks 1, 2 and 3 which are glued together using ultra violet cured adhesive. The fibre support block 1 includes an accurate 'V' groove 4 which acts as a fibre guide. To ensure accuracy of the 'V' groove 4, particularly in regard to the angle at the base of the 'V' this block is in practice machined from two blocks which are subsequently glued together in the manner described in our European Patent Application No. 86302785.0 (Publication No. 200414). For use with currently available optical fibres the block 1 is approximately twenty millimetres wide, twenty millimetres long and ten millimetres deep, the 'V' groove running along the centre line of the block and having an upper width of 0.177 millimetres. The facing block 2, approximately twenty millimetres deep and two millimetres long has a four millimetre aperture 5 drilled through centred on the centrelines of the vertical face. A one millimetre wide channel 6 is provided to facilitate entry of a fibre end (not shown) through the aperture 5. The mounting block 3, approximately seven millimetres deep and four millimetres long includes a 'V' shaped channel 7 which is arranged to receive either circular or rectangular mirrors or cover slides commonly used in fibre laser or amplifier systems for laboratory use. The block 3 is machined to provide a 'V' groove centred on the centre line and having a width at the upper end of 12.06 millimetres and at an angle to the vertical of 45 degrees. The block is completed by using silica inserts 8 and 9 which are glued in position the block 9 being two millimetres thick and the block 8 one millimetre thick. By using differing thicknesses of insert the 'V' groove is offset laterally with respect to the groove 4 (i.e. their planes of symmetry are offset) so that if for example a circular mirror is used then rotating same in the channel 7 results in a different portion of the receiving surface being presented. The forward face 10 of the block 2 is lapped and polished to ensure that it is precisely perpendicular to the 'V' groove 4. Thus, in use, a mirror (or other planar receiving surface) is placed in the 'V' 7 and abutted to the surface 10. Since the surface 10 is precisely perpendicular to the V groove 4 a fibre edged forward along the groove in the direction of the mirror using a single advancing micrometer for example will abut the planar surface as accurately as the perpendicularity of the cleaving of the end of the fibre. Optical fibre has sufficient resilience to permit slight over advancement (i.e. causing the fibre to bend slightly on abutment) the fibre readily returning to alignment when withdrawn slightly. Index matching fluid may be used on the fibre end if necessary to cater for any slight deviation from the perpendicularity of the cleaver. Referring specifically now to figures 2 and 3, the block 1 may be provided with apertures 11 to enable screw mounting of the support assembly to another surface. It is here noted that the apertures 11 include a countersunk section so that if screws are used the head comes below the surface to avoid accidental breakage of fibres by snagging. A further pair of apertures 12, one on each side of the 'V' groove 4 are also provided. These apertures 12 each receive an insert of magnetic stainless steel. This enables retention of a fibre in position by use of a flexible magnetic strip which may be laid over the fibre and 'V' groove 4. Although as herein the apparatus is manufactured of silica other materials (e.g. aluminium) could be used. One advantage of silica is that thermal expansion effects on optical fibres are less likely to cause a system to move out of adjustment if the thermal co-efficients of the mounting and the fibre are compatible. A further advantage of silica block is noted particularly in laboratories in that in the event of stray laser light striking the block it will be scattered rather than reflected, thus reducing (as may occur with metallic blocks) the likelihood of accidental eye damage in persons working in such environments. For the avoidance of doubt although metric dimensions have been given throughout to facilitate construction of apparatus in accordance with the invention, it is here noted that such dimensions are exemplary and should not be construed as limiting the invention.

Claims: Optical fibre locating apparatus for adjusting an optical fibre perpendicular to a planar surface of an optical component, said optical fibre locating apparatus comprising first block means (1) having a guide surface which includes a "V"-groove (4) arranged to receive and to guide an optical fibre and having a first abutting surface, second block means (2) having a second abutting surface which abuts said first abutting surface of said first block means, a third abutting surface (10) perpendicular to said "V" -groove (4), and an aperture (5) arranged such that an optical fibre guided along said "V"-groove (4) can pass through said aperture (5), and mounting means (3) having a fourth abutting surface which abuts said third abutting surface (10) of said second block means, on which mounting means (3) said optical component can be mounted such that said planar surface of said optical component abuts said third abutting surface (10) and is located with respect to said aperture (5) such that an optical fibre guided along said "V"-groove (4) abuts said planar surface perpendicularly. Optical fibre locating apparatus as claimed in claim 1 wherein the mounting means (3,7) comprises third block means (3) including a 'V' shaped channel (7). Optical fibre locating apparatus as claimed in claim 2 wherein the 'V' shaped channel (7,8,9) is offset laterally with respect to the 'V' groove (4) whereby an optical component having a circular cross section may be rotated such that the part of the planar surface at which light emitting from a fibre is received may be varied. Optical fibre locating apparatus as claimed in claim 1, claim 2 or claim 3 wherein the first block means (1) includes holding means arranged to retain a fibre in the 'V' groove. Optical fibre locating apparatus as claimed in claim 4 wherein the holding means comprises magnetically responsive material disposed on each side of the 'V' groove and a flexible strip of magnetic material Optical fibre locating apparatus as claimed in claim 5 wherein the magnetically responsive material comprises magnetic stainless steel insets located in apertures (12) included in the first block means (1). Optical fibre locating apparatus as claimed in any preceding claim wherein each means (1,2,3) is a silica block.

Inventors: HUNT MICHAEL HAROLD, MILLER IAIN DAVID, HUNT, MICHAEL HAROLD, MILLER, IAIN DAVID
Applicants: BRITISH TELECOMM, BRITISH TELECOMMUNICATIONS PUBLIC LIMITED COMPANY
Application year: 1989
Main classification: G02B6
IPC codes: G02B6