GB2114769A - Single mode fibre adjustable attenuator - Google Patents
Single mode fibre adjustable attenuator Download PDFInfo
- Publication number
- GB2114769A GB2114769A GB8203647A GB8203647A GB2114769A GB 2114769 A GB2114769 A GB 2114769A GB 8203647 A GB8203647 A GB 8203647A GB 8203647 A GB8203647 A GB 8203647A GB 2114769 A GB2114769 A GB 2114769A
- Authority
- GB
- United Kingdom
- Prior art keywords
- fibre
- single mode
- attenuator
- fibres
- optical
- Prior art date
- Legal status (The legal status 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 status listed.)
- Granted
Links
- 239000000835 fiber Substances 0.000 title claims abstract description 36
- 230000003287 optical effect Effects 0.000 claims abstract description 11
- 239000007788 liquid Substances 0.000 claims abstract description 5
- 238000005253 cladding Methods 0.000 claims description 4
- 239000013307 optical fiber Substances 0.000 claims description 2
- 239000000463 material Substances 0.000 claims 1
- 238000000576 coating method Methods 0.000 description 8
- XEEYBQQBJWHFJM-UHFFFAOYSA-N Iron Chemical compound [Fe] XEEYBQQBJWHFJM-UHFFFAOYSA-N 0.000 description 4
- VYPSYNLAJGMNEJ-UHFFFAOYSA-N Silicium dioxide Chemical compound O=[Si]=O VYPSYNLAJGMNEJ-UHFFFAOYSA-N 0.000 description 4
- 239000011248 coating agent Substances 0.000 description 4
- 210000004907 gland Anatomy 0.000 description 4
- 238000007765 extrusion coating Methods 0.000 description 3
- 239000004677 Nylon Substances 0.000 description 2
- 150000001875 compounds Chemical class 0.000 description 2
- 229910052742 iron Inorganic materials 0.000 description 2
- 229920001778 nylon Polymers 0.000 description 2
- 239000004033 plastic Substances 0.000 description 2
- 229920003023 plastic Polymers 0.000 description 2
- 238000004382 potting Methods 0.000 description 2
- 239000000377 silicon dioxide Substances 0.000 description 2
- 238000005476 soldering Methods 0.000 description 2
- 229910000831 Steel Inorganic materials 0.000 description 1
- 230000008878 coupling Effects 0.000 description 1
- 238000010168 coupling process Methods 0.000 description 1
- 238000005859 coupling reaction Methods 0.000 description 1
- 230000000694 effects Effects 0.000 description 1
- 239000003822 epoxy resin Substances 0.000 description 1
- 239000012530 fluid Substances 0.000 description 1
- 230000007935 neutral effect Effects 0.000 description 1
- 239000012188 paraffin wax Substances 0.000 description 1
- 229920000647 polyepoxide Polymers 0.000 description 1
- 229920001296 polysiloxane Polymers 0.000 description 1
- 230000001902 propagating effect Effects 0.000 description 1
- 238000000926 separation method Methods 0.000 description 1
- 229920002050 silicone resin Polymers 0.000 description 1
- 229920002379 silicone rubber Polymers 0.000 description 1
- 239000004945 silicone rubber Substances 0.000 description 1
- 239000010959 steel Substances 0.000 description 1
- 239000000126 substance Substances 0.000 description 1
Classifications
-
- H—ELECTRICITY
- H04—ELECTRIC COMMUNICATION TECHNIQUE
- H04B—TRANSMISSION
- H04B10/00—Transmission systems employing electromagnetic waves other than radio-waves, e.g. infrared, visible or ultraviolet light, or employing corpuscular radiation, e.g. quantum communication
- H04B10/25—Arrangements specific to fibre transmission
- H04B10/2507—Arrangements specific to fibre transmission for the reduction or elimination of distortion or dispersion
-
- G—PHYSICS
- G02—OPTICS
- G02B—OPTICAL ELEMENTS, SYSTEMS OR APPARATUS
- G02B6/00—Light guides; Structural details of arrangements comprising light guides and other optical elements, e.g. couplings
- G02B6/24—Coupling light guides
- G02B6/26—Optical coupling means
- G02B6/264—Optical coupling means with optical elements between opposed fibre ends which perform a function other than beam splitting
Landscapes
- Physics & Mathematics (AREA)
- General Physics & Mathematics (AREA)
- Optics & Photonics (AREA)
- Electromagnetism (AREA)
- Engineering & Computer Science (AREA)
- Computer Networks & Wireless Communication (AREA)
- Signal Processing (AREA)
- Optical Couplings Of Light Guides (AREA)
- Mechanical Coupling Of Light Guides (AREA)
Abstract
An adjustable attenuator for single mode fibre in which the attenuation is adjusted by varying the spacing between the opposed ends of two single mode optical fibres (10, 11) held in alignment by a Vee-groove in an alignment block (12) positioned in a vessel optionally containing an index matching liquid. <IMAGE>
Description
SPECIFICATION
Single mode fibre adjustable attenuator
This invention relates to attenuating the light propagating in a single mode fibre. Variable attenuators have been constructed for multimode fibre which rely upon placing a graduated density neutral filter between the two halves of an expanded beam type connector, or rely upon adjusting the angular misalignment of the two halves of a detector. The disadvantage of using either of these types of approach for a single mode attenuator is that they are liable to be too polarisation state sensitive for a number of applications. A design is required which provides an attenuation that is substantially independent of polarisation orientation.
According to the present invention there is provided a single mode fibre adjustable optical attenuator in which two single mode fibres are held by clamps near their opposed ends so that these ends are deflected by the walls of a Vee groove formed in an alignment member so as to constrain the ends to lie on a common axis, wherein the alignment member is contained in or forms part of a vessel for containing an index matching liquid in which to immerse the fibre ends, and wherein the two clamps are mounted on a slide mechanism by means of which one clamp may be moved in a controlled manner relative to the other in a direction that is substantially in alignment with the groove direction so as to adjust the distance separating the fibre ends.
There follows a description of a single mode fibre adjustable optical attenuator embodying the invention in a preferred form. The description refers to the accompanying drawings in which: Figure 1 is a perspective view of the attenuator alignment block
Figure 2 is a plan view of the attenuator
Figure 3 is a section view of the attenuator on the line A-A and
Figure 4 is a sectional view of one of the diaphragm glands preventing egress of index matching fluid from the vessel containing the alignment block in the regions where the optical fibres enter the vessel.
The principle of operation of the attenuator is that two single mode fibres 10, 11 are constrained by their natural flexural resilience to lie in alignment in a Vee-groove formed in an alignment block 12. One fibre, 10, remains stationary in the groove while the other, 11 is advanced along the groove towards the first, or is retracted from it, so as to increase, or decrease, the optical coupling between the fibre ends. The
Vee-groove holds the fibres in axial alignment at all times and thus avoids the needs for complicated micro-positioning means to retain lateral positioning of the fibres during this translational movement in the axial direction.
Lateral movement is undesirable because it is liable to be inconsistent and excessively sensitive to polarision orientation. The alignment block 12 is located in a vessel 20 (not shown in Figure 1) which can be filled with an index matching liquid in order to suppress Fresnel reflections at the fibre ends. For silica fibre this liquid may be for instance a paraffin or a suitable silicone.
Referring now to Figure 2 and 3, the vessel 20 containing the alignment block 12 is mounted on a slide mechanism constituted by a commercially available translation stage 21. The fibres 10, 11 are secured respectively by clamps 22 and 23.
Clamp 22 is rigidly secured to the vessel 20, while clamp 23 is rigidly secured to the slide of the translation stage so as to be moveable relative to clamp 22 under the control of a knob 25 mechanically linked with the translation stage lead screw. (The housing is completed by a lid that is not shown in any of the drawings). The fibres enter the vessel through apertures 26 closed off by diaphragm moulded glands whose shape is shown in cross section in Figure 4. These glands are required to be highly compliant so as to minimise the mechanical effect upon the fibres, and may be made for instance of a silicone rubber. In its relaxed state the central stub of each giand is inclined at an angle roughly corresponding to the angle at which the two clamps are secured so as to cause the fibre ends to bed satisfactorily in the Vee-groove of the alignment block.Typically the angle between the two clamps is about 1400 so that each fibre is bent through an arc of about 200. The vessel 20 is completed by a lid 27.
Optionally a screw 28 is provided to act as a stop to limit the slide movement to prevent one fibre end from being urged into actual physical contact with the other.
Each fibre enters the attenuator housing by way of a feed-through 29 from where it is led via a cladding mode stripper 30 to one of the clamps 22, 23. Initially the fibres are protected by plastics coatings typically constituted by a thin primary coating covered by a thicker extrusion coating.
Each cladding mode stripper 30 consists essentially of a plate provided with circular channel 31, which, for 125 micron single mode fibre, is typically about 60 mm in diameter. One turn of the fibre is accommodated within this channel 31, and over this length the plastics coatings are removed to expose the bare fibre, and the channel is filled with a higher refractive index potting compound, such as an epoxy resin, so that any optical energy guided by the optical cladding of fibre is stripped from the fibre to be absorbed in the potting compound.In the case of a fibre with a typical silicone resin primary coating and a nylon extrusion coating, the extrusion coating can conveniently be removed over the required length with the aid of a hot air blower or a soldering iron, and then the primary coating by knotting a nylon fibre around the optical fibre and using the knot to strip the coating from the fibre.
The knot itself is then conveniently removed with the soldering iron. The coatings are also stripped from the region of each fibre protruding inwardly from the gland inside the vessel 20 so that the
Vee-groove aligns the fibres by the fibres themselves rather than by their coatings.
If the maximum attenuation required is relatively small the alignment block 12 may conveniently be made of hardened ground steel, but this can give rise to reflection problems at large fibre separations with a significant proportion of the light coupled from one fibre to the other being coupled by way of reflection in the surface of the Vee-groove. Typically this begins to become a problem for attenuations in excess of 15 dB. The problem can be alleviated by providing a hole (not shown) in the block intersecting the
Vee-groove between the fibre ends. For 125 micron diameter fibre a 0.5 mm diameter hole (not shown) positioned approximately one fibre diameter in front of the end of the transmitting fibre has proved satisfactory. An alternative approach to the problem is to suppress the reflections by constructing the block of an index matching substance, such as silica.
Claims (5)
1. A single mode fibre adjustable optical attentuator in which two single mode fibres are held by clamps near their opposed ends so that these ends are deflected by the walls of a Vee groove formed in an alignment member so as to constrain the ends to lie on a common axis, wherein the alignment member is contained in or forms part of a vessel for containing an index matching liquid in which to immerse the fibre ends, and wherein the two clamps are mounted on a slide mechanism by means of which one clamp may be moved in a controlled manner relative to the other in a direction that is substantially in alignment with the groove direction so as to adjust the distance separating the fibre ends.
2. An attenuator as claimed in claim 1, wherein each optical fibre passes through a cladding mode stripper.
3. An attenuator as claimed in claim 1 or 2, wherein the alignment member includes an aperture intersecting the Vee-groove between the opposed ends of the two optical fibres.
4. An attenuator as claimed in claim 1 or 2, wherein the alignment member is constructed of a material whose refractive index matches that of the cores of the two optical fibres.
5. A single mode fibre adjustable optical attenuator substantially as hereinbefore described with reference to the accompanying drawings.
Priority Applications (3)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| GB8203647A GB2114769B (en) | 1982-02-09 | 1982-02-09 | Single mode fibre adjustable attenuator |
| NZ20307983A NZ203079A (en) | 1982-02-09 | 1983-01-25 | Opposed fibre ends in optical attenuator aligned in v-shaped groove and moveable axially therein |
| AU10977/83A AU1097783A (en) | 1982-02-09 | 1983-02-03 | Single mode fibre adjustable attenuator |
Applications Claiming Priority (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| GB8203647A GB2114769B (en) | 1982-02-09 | 1982-02-09 | Single mode fibre adjustable attenuator |
Publications (2)
| Publication Number | Publication Date |
|---|---|
| GB2114769A true GB2114769A (en) | 1983-08-24 |
| GB2114769B GB2114769B (en) | 1985-08-29 |
Family
ID=10528189
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| GB8203647A Expired GB2114769B (en) | 1982-02-09 | 1982-02-09 | Single mode fibre adjustable attenuator |
Country Status (3)
| Country | Link |
|---|---|
| AU (1) | AU1097783A (en) |
| GB (1) | GB2114769B (en) |
| NZ (1) | NZ203079A (en) |
Cited By (6)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| GB2166885A (en) * | 1984-11-09 | 1986-05-14 | Stc Plc | Single mode fibre adjustable attenuator |
| GB2173319A (en) * | 1985-04-02 | 1986-10-08 | Kinaut Instr Ltd | Attenuators for optical fibres |
| GB2189902A (en) * | 1986-04-30 | 1987-11-04 | Stc Plc | Single mode fibre adjustable attenuator |
| US4787700A (en) * | 1986-05-15 | 1988-11-29 | Radiall Industrie | Attenuator for single-mode optical fibers and process for its fabrication |
| US5066094A (en) * | 1990-09-07 | 1991-11-19 | Seikoh Giken Co., Ltd. | Variable optical fiber light attenuator |
| EP0593836A1 (en) * | 1992-10-22 | 1994-04-27 | International Business Machines Corporation | Near-field photon tunnelling devices |
-
1982
- 1982-02-09 GB GB8203647A patent/GB2114769B/en not_active Expired
-
1983
- 1983-01-25 NZ NZ20307983A patent/NZ203079A/en unknown
- 1983-02-03 AU AU10977/83A patent/AU1097783A/en not_active Abandoned
Cited By (6)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| GB2166885A (en) * | 1984-11-09 | 1986-05-14 | Stc Plc | Single mode fibre adjustable attenuator |
| GB2173319A (en) * | 1985-04-02 | 1986-10-08 | Kinaut Instr Ltd | Attenuators for optical fibres |
| GB2189902A (en) * | 1986-04-30 | 1987-11-04 | Stc Plc | Single mode fibre adjustable attenuator |
| US4787700A (en) * | 1986-05-15 | 1988-11-29 | Radiall Industrie | Attenuator for single-mode optical fibers and process for its fabrication |
| US5066094A (en) * | 1990-09-07 | 1991-11-19 | Seikoh Giken Co., Ltd. | Variable optical fiber light attenuator |
| EP0593836A1 (en) * | 1992-10-22 | 1994-04-27 | International Business Machines Corporation | Near-field photon tunnelling devices |
Also Published As
| Publication number | Publication date |
|---|---|
| NZ203079A (en) | 1985-12-13 |
| AU1097783A (en) | 1983-08-18 |
| GB2114769B (en) | 1985-08-29 |
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Legal Events
| Date | Code | Title | Description |
|---|---|---|---|
| PCNP | Patent ceased through non-payment of renewal fee |