WO1992002800A1 - Coupleur et detecteur optiques - Google Patents

Coupleur et detecteur optiques Download PDF

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Publication number
WO1992002800A1
WO1992002800A1 PCT/GB1991/001342 GB9101342W WO9202800A1 WO 1992002800 A1 WO1992002800 A1 WO 1992002800A1 GB 9101342 W GB9101342 W GB 9101342W WO 9202800 A1 WO9202800 A1 WO 9202800A1
Authority
WO
WIPO (PCT)
Prior art keywords
fibre
light
optical
block
detector
Prior art date
Application number
PCT/GB1991/001342
Other languages
English (en)
Inventor
Colin Robert Paton
David Alexander Ferguson
Original Assignee
British Telecommunications Public Limited Company
Priority date (The priority date is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the date listed.)
Filing date
Publication date
Application filed by British Telecommunications Public Limited Company filed Critical British Telecommunications Public Limited Company
Publication of WO1992002800A1 publication Critical patent/WO1992002800A1/fr

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Classifications

    • G—PHYSICS
    • G01—MEASURING; TESTING
    • G01M—TESTING STATIC OR DYNAMIC BALANCE OF MACHINES OR STRUCTURES; TESTING OF STRUCTURES OR APPARATUS, NOT OTHERWISE PROVIDED FOR
    • G01M11/00—Testing of optical apparatus; Testing structures by optical methods not otherwise provided for
    • G01M11/08—Testing mechanical properties
    • G01M11/088—Testing mechanical properties of optical fibres; Mechanical features associated with the optical testing of optical fibres

Definitions

  • This invention relates to optical coupling and detecting equipment, and particularly to equipment for launching light into, and coupling light out of, optical fibres.
  • a clip-on power meter is generally used to check whether the fibre is live or not, as cutting into a live fibre can damage system components, such as lasers, may cause a system to crash and can be dangerous.
  • two pieces of apparatus were needed to test an optical fibre, one piece of apparatus to launch the test signal and a second piece of equipment to detect the reflected signal.
  • Each piece of equipment connected to a fibre causes a drop in the signal power in that fibre, such a drop being caused by the introduction of a sharp bend in the fibre, the exertion of pressure on the fibre, optical mismatching between pieces of equipment or misalignment.
  • Such losses have a cumulative effect, and the greater the number of pieces of equipment attached to a fibre the greater the overall loss on that fibre. If the losses on an optical fibre are too great, then data travelling down the fibre can be corrupted or even lost.
  • a common method of fault finding during maintenance on an optical fibre is by using an OTDR (Optical Time Domain Reflectometer). This works by sending light down an optical fibre and measuring the backscattered signal. The light is launched into the fibre from an end. In practice, its use is limited to use on a fibre at an exchange if communication on the fibre is not to be disrupted by breaking into the fibre. Up until now, it has not been possible to maintain a fibre without access to an end.
  • an engineer In many situations, it is desirable for an engineer to sample the signals that are being transmitted along an optical fibre and also to send signals down the fibre. This may be for maintenance or testing purposes, or so that the engineer can receive communications from the exchange or from another engineer further up or down the fibre. This would mean further equipment being connected to the ' optical fibre.
  • the object of the invention is to reduce the number of pieces of equipment that an engineer needs to couple onto a. fibre, and replace them with a single versatile unit.
  • the present invention provides apparatus for coupling light into, and detecting light emitted from, an optical fibre, the apparatus comprising means for bending and exerting a pressure on an optical fibre, and means for injecting light received from a light source into the bent portion of the optical fibre, wherein an optical detector is attached to the bending means, the optical detector being arranged to detect light emerging from the bent portion of the optical fibre.
  • the apparatus further comprises means for adjusting the amount of pressure exerted on the optical fibre.
  • the light source is mounted on an x-y positioner.
  • the detector is a photodiode fixed to the fibre bending means with an optical cement.
  • the light detector and the light source are coupled to the fibre by a pigtailed graded index lens attached to the x-y positioner.
  • the apparatus may further comprise a control unit for operating the x-y positioner, the control unit receiving information about the amount of light coupled into the fibre, and adjusting the x-y positioner to maximise the coupled-in light.
  • the bending means comprises a mandrel and a block formed with a complementary recess.
  • the block is made of a light-transmitting material such as perspex.
  • the recess is V-shaped and is defined by two surfaces of the block which are inclined to one another at an angle lying within the range of 150° to 179°.
  • the apex of the recess has a rounded cross section.
  • the radius of curvature of the rounded cross section lies within the range of from 2mm to 3mm.
  • the bending means, the injecting means and the optical detector from a launch-and-detect head, the block of which has an angled end face such that light is guided by total internal reflection.
  • the angled end face forms an angle of approximately 48° with the base of the block.
  • Figure 1 is schematic side view of the first form of transceiver
  • Figure 2 is cross-sectional view of the first form of transceiver;
  • Figures 3a and 3b are different side views of the fibre clamping portion of the transceiver shown in
  • Figure 4 is a cross-sectional view of the second form of transceiver.
  • Figure 5 is a diagrammatic side view of an alternative optical head for use with either form of transceiver.
  • Figure 1 shows a transceiver having a laser 1 mounted on an x-y positioner 2.
  • a graded index (GRIN) rod lens 3 is attached to the laser 1.
  • the laser 1 is aligned with an optical head 4 made of transparent acrylic plastics material.
  • the optical head 4 has attached to it a photodetector 10 to detect the light coming out of a fibre 7 positioned on the head 4.
  • the optical head 4 is mounted on a rotation stage 5 which is used to adjust the angle of head alignment.
  • the rotation stage 5 is mounted on a z axis positioner 6 for positioning the optical head 4.
  • the optical head 4 comprises upper and lower co ⁇ operating blocks 8 and 9, the upper block 8 of which is a mandrel.
  • the lower block 9 is formed with a shallow recess 30 defined by inwardly inclined surfaces 32. The surfaces meet at a V-shaped portion 34.
  • the V-shaped portion subjects the fibre to a tight bend of short arcuate length (a kink). This causes light carried by the fibre 7 to leak out, or allows light to be injected into the fibre. The leakage and/or injection are over a very small region of the fibre 7 in the vicinity of the rounded V-shaped portion.
  • Light is, therefore, tapped out of the fibre or launched into the fibre from practically a point source. Light which is tapped out then travels through the lower block 9 in a narrow but slightly diverging beam 40. This beam 40 is then directed to the photodetector 10 by total internal reflection from an angled side surface 42 of the block. Light launched into the fibre would follow a similar path.
  • the recess 30 has a groove 36 (shown in Figure 3b) to receive an optical fibre 7.
  • the fibre 7 is held in the groove 36 by the co-operative action of the upper block 8.
  • the groove 36 is approximately 250 ⁇ m wide and is bent at an angle of 30° round a radius of 3mm.
  • the force with which the fibre 7 is compressed between the blocks -8 and 9 may be adjusted by means of a screw 12 acting on the block 8. This adjustment also facilitates optimum coupling of light into, and out of, the fibre 7.
  • the insertion loss of the device is also controlled by this adjustment with a large force on the fibre 7 resulting in a high insertion loss.
  • the detector 10 is glued to the lower block 9, using an optical cement, in such a position that it can detect the light coupled out of the fibre 7, while not blocking the light to be coupled in from the laser 1.
  • Five adjustments need to be made to the transceiver namely adjustments to the pressure on the fibre, the angle of the optical head 4 and the x, y and z positions, these adjustments varying in the degree of accuracy ' required. Once these adjustments have been made then the device is ready for operation.
  • the power launched in to the fibre 7 is dependent upon the loss caused by the optical head 4.
  • the transceiver When the transceiver is set up for the first time, the setting of the screw 12 giving optimum power needs to be noted. Then, on subsequent occasions, the equipment can be set immediately to the setting which gives the optimum power. The rest of the set up procedure can then be carried out in the knowledge that the insertion loss is correct.
  • the angular adjustment of the optical head 4 is not critical, as launch power is within 3dB of the optimum value over a range of +. 11° Consequently, the angular adjustment of the optical head 4 may also be pre-set.
  • the x and y, adjustments are particularly critical, as the transceiver will tolerate a misalignment of only +. 15 ⁇ m in the x and y directions, while the tolerance in the z direction is ⁇ 1.25mm.
  • FIG. 4 shows the second form of transceiver, this transceiver being a modification of that shown in Figures 1 to 3, so like reference numerals will be used for like parts, and only the modifications will be described in detail.
  • the transceiver is capable of operating at different optical frequencies simply by plugging in different lasers and/or detectors onto a pigtail connector.
  • This version of the transceiver has a GRIN lens 15 instead of the laser 1 and the detector 10. This allows different frequency lasers (not shown) to be used as light sources, without having to recalibrate the equipment. Similarly, where necessary, different detectors (not shown) can also be used.
  • Figure 5 shows a modified block 9' which can be used with either of the embodiments shown in Figures 2 and 4.
  • the block 9' is made of transparent acrylic plastics material, and is formed with a shallow recess 30 defined by inwardly inclined surfaces. The surfaces meet at a rounded V-shaped portion 37, the surfaces defining an included angle ⁇ of 150°, and the radius of curvature of the rounded portion being 3mm.
  • a 3dB coupler 20 which connects an optical fibre 14 to the light source and the detector, allows light to be launched and detected via a pigtail.
  • the block 9 of either of the transceivers of Figures 2 and 4 could have a rounded V-shape as shown in Figure 5.
  • the radius of curvature used has an optimum value which is dependent on the. angle of the kink. A larger ' radius gives a lower insertion loss in the fibre 7, and may therefore be used to compensate for the effect of decreasing the kink angle. The combination of a radius of curvature of 3mm and an arc of 30° gives good results.
  • a further use of the type of transceiver described above would be as an alignment device for calibrating or aligning clip-on launch devices. As mentioned above, the x-y alignment of the transceiver of the invention is critical with a tolerance of only +. 15 ⁇ m.
  • the x-y alignment problem is exacerbated by the fact that the manufacturing specification for a single mode fibre allows considerable latitude in the geometrical position of the fibre core inside the cladding and the primary coating layers.
  • the outer surface coating may be located with some precision, the true position of the core is uncertain within limits which may considerably exceed the 15 ⁇ m tolerance.
  • a transceiver of the invention can be used to launch light into a fibre; and then, using another transceiver (or a power meter) connected to a black box to detect the light coupled into the fibre, the black box can then adjust the GRIN lens 3 in the x-y direction until the optimum power signal is achieved.

Abstract

Dispositif de contrôle de fibre optique, qu'on peut pincer sur une fibre optique (7), permettant de capter la lumière hors de la fibre et également d'introduire de la lumière dans ladite fibre. Ce dispositif permet de contrôler les fibres optiques, de localiser et de réparer leurs défauts sans interrompre le fonctionnement normal de la fibre.
PCT/GB1991/001342 1990-08-06 1991-08-06 Coupleur et detecteur optiques WO1992002800A1 (fr)

Applications Claiming Priority (2)

Application Number Priority Date Filing Date Title
GB909017223A GB9017223D0 (en) 1990-08-06 1990-08-06 Optical fibre test equipment
GB9017223.0 1990-08-06

Publications (1)

Publication Number Publication Date
WO1992002800A1 true WO1992002800A1 (fr) 1992-02-20

Family

ID=10680241

Family Applications (1)

Application Number Title Priority Date Filing Date
PCT/GB1991/001342 WO1992002800A1 (fr) 1990-08-06 1991-08-06 Coupleur et detecteur optiques

Country Status (3)

Country Link
AU (1) AU8324491A (fr)
GB (1) GB9017223D0 (fr)
WO (1) WO1992002800A1 (fr)

Cited By (2)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
JP2015206840A (ja) * 2014-04-17 2015-11-19 日本電信電話株式会社 光ファイバ切替装置および方法
JP2016114756A (ja) * 2014-12-15 2016-06-23 日本電信電話株式会社 光ファイバ側方入出力器の製造装置及び光ファイバ側方入出力装置の製造方法

Families Citing this family (1)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
GB9015992D0 (en) * 1990-07-20 1990-09-05 British Telecomm Optical tap

Citations (1)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US4775233A (en) * 1985-05-24 1988-10-04 Sumitomo Electric Industries, Ltd. Method of the measurement of light from an optical cable and arrangement therefor

Patent Citations (1)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US4775233A (en) * 1985-05-24 1988-10-04 Sumitomo Electric Industries, Ltd. Method of the measurement of light from an optical cable and arrangement therefor

Cited By (2)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
JP2015206840A (ja) * 2014-04-17 2015-11-19 日本電信電話株式会社 光ファイバ切替装置および方法
JP2016114756A (ja) * 2014-12-15 2016-06-23 日本電信電話株式会社 光ファイバ側方入出力器の製造装置及び光ファイバ側方入出力装置の製造方法

Also Published As

Publication number Publication date
GB9017223D0 (en) 1990-09-19
AU8324491A (en) 1992-03-02

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