GB2365990A

GB2365990A - Optical device with strengthening member and guide formations

Info

Publication number: GB2365990A
Application number: GB0019238A
Authority: GB
Inventors: Andrew Kevin Wellings; Mark Volanthen
Original assignee: Kymata Ltd; Alcatel Optronics UK Ltd
Current assignee: Kaiam Europe Ltd; Kymata Ltd
Priority date: 2000-08-04
Filing date: 2000-08-04
Publication date: 2002-02-27
Also published as: GB0019238D0; AU2002229153A1; WO2002012940A1

Abstract

An optical device has outer walls 35,45 with which one ore more optic fibres 30,40 are routed. A flexible strengthening member 50 is attached to the optic fibre 40 adjacent an outer aspect of the wall 45 and guide formations 60 protrude from the wall 45, being positioned and shaped with respect to the strengthening member 50 to prevent the strengthening member 50 from bending in at least one direction at a predetermined bend radius. The guide formations 60 can be disposed on at least two opposing sides of the strengthening member 50, and can form a opening which narrows towards the wall. The guide formations 60 may also be curved where the curve radius is greater than or equal to the predetermined minimum radius to prevent optic fibre strain, the guide formations 60 may also be circular symmetric.

Description

1 2365990 OPTICAL DEVICE This invention relates to optical devices, for

example devices providing support for optical fibres, such as single optical fibres, optical fibre ribbon cables or other arrangements 5 or cables of optical fibres.

Optical fibres are considered to be mechanically flexible. Fibres, either singly or formed into ribbons or cables, can be bent or curved to achieve a desired routing layout or for other purposes. However, there are limits on the minimum radius by which an optical fibre can be bent. As the bend radius decreases (i.e. the bend becomes tighter), losses in the 10 optical fibre increase. Generally a commercially available optical fibre will have a specified minimum bend radius such as l0mm. This is a minimum radius below which losses or other undesirable effects such as bireffingence in the fibre increase above a level considered acceptable.

One situation in which undesirably tight bends can occur is where a fibre passes 15 through the packaging of a packaged optical device. For example, an integrated optical component such as an arrayed waveguide device, variable optical attenuator or the like will typically be formed on a substrate to which one or more optical fibres are connected. The substrate is mounted within a mechanically robust package to prevent access or damage to the integrated component. This means that input and output optical fibres must pass through 20 the packaging to provide a connection to the integrated component, If the fibre simply emerged through a planar surface of the package, there would be a significant danger that the fibre could kink at the package wall - in other words, that the fibre would suffer a sharp discontinuity or change of direction at the package wall.

To avoid this it has been proposed to fit a rubber "boot" around the fibre as it 25 emerges from the packaging. The rubber boot increases the radius and stiffness of the fibre in the vicinity of the package wall, so inhibiting sharp bending of the fibre.

This invention provides an optical device having an outer wall through which one or more optical fibres are routed, the device comprising:

a flexible strengthening member attached to the optical fibre adjacent to an outer 30 aspect of the wall; and guide formations protruding from the wall, the guide formations being positioned and shaped with respect to the strengthening member so as to prevent at least a part of the strengthening member adjacent to the wall from bending, in at least one direction, at a bend radius less than a predetermined minimum radius.

The invention recognises that the use of the rubber boot as described above does not in fact ensure that the fibre maintains at least a minimum bend radius. So, undesirably tight bends could still occur.

To alleviate this problem the invention makes use of guide formations protruding 5 from the wall which inhibit bending of the strengthening member.

Although the guide formations could act to inhibit bending in only one direction, or a pair of opposing directions, it is preferred that the guide formations are arranged so as to prevent at least a part of the strengthening member adjacent to the wall from bending, in any direction, at a bend radius less than a predetermined radius. This is advantageously achieved 10 by using guide formations which are circularly symmetric.

Although these techniques are useful in respect of single optical fibres, they are particularly useful for two or more optical fibres attached to a common strengthening member. The two or more optical fibres could be formed into a single cable such as an optical fibre ribbon cable.

15 The device is particularly useful as an optical fibre connector or as a package for an optical component, such as an integrated optical component, and indeed the invention extends to a packaged optical component comprising an optical component housed in such a device.

Embodiments of the invention will now be described with reference to the 2o accompanying drawings, throughout which like parts are referred to by like references, and in which:

Figure I is a schematic cross section of a packaged optical device; Figures 2 to 5 are schematic end elevations showing different configurations of the packaged device of Figure 1; and 25 Figure 6 is a schematic cross section of an optical fibre connector.

Figure I is a schematic cross section of a packaged optical device. An integrated optical component such as an arrayed waveguide grating, a variable optical attenuator, an optical switch, a combination of two or more of these functions or another device altogether is mounted within a plastics package 20. The package 20 is in the form of a rectangular 30 box, although of course other forms could be used. The component 10 is fastened to at least one sidewall of the package 20 by, for example, plastics lugs (not shown).

Optical fibre ribbon cables 30, 40 penetrate the walls 35, 45 of the package 20 and are connected ("pigtailed") to the optical component 10. Optical fibre ribbon cables are flat arrays of optical fibres fastened side-by-side to one another, generally in a I x n configuration although other configurations such as a 2 x n configuration could be used. In other embodiments single optical fibres or bundled optical fibre cables could be used. the fibres / cables could be sleeved or unsleeved.

At (and near to) the point at which the cables penetrate the walls of the package 20, a 5 strengthening member 50 is attached to the optical fibre cable. In this embodiment the strengthening member 50 is a flexible sleeve which surrounds the cable and protrudes a short distance (e.g. 20mm) from the outer wall of the package 20. However, in other embodiments a strengthening member could be fastened to one side of the cable. Preferably, the strengthening member 50 is elongate along the longitudinal axis of the fibre cable and 10 preferably sufficiently flexible so as to bend with the optical fibre cable - otherwise, a sharp bend or "kink" could occur at the distal end of the strengthening member 50. Examples of suitable materials for the strengthening member 50 are silicone and polyurethane. Although the strengthening member 50 bends with the fibre cable, it has another function which is to add bulk to the cable in order to inhibit sharp bends along the length of the strengthening 15 member 50. In this respect, the strengthening member acts in a similar manner to the "rubber boot" arrangement of the prior art discussed above.

Guide formations 60 also protrude from the outer walls 35, 45 of the package 20.

The guide formations have a surface adjacent to the strengthening member which curves with a radius rl, a radius which is greater than or equal to the minimum desired bend radius 20 of the optical fibre cable. The curve is arranged so that the guide formation is narrow towards the wall 35, 45 of the package 20.

It can therefore be seen that the guide formations inhibit bending of the strengthening member 50 to a sharper radius than that defined by the curved edge of the guide formations, namely radius rl. In fact, if the edge of the strengthening member 50 is abutted against the 25 guide formation 60, the longitudinal axis of the fibre cable 30 will bend at a radius slightly greater than rl. So, ri could be made smaller than the minimum bend radius of the fibre cable, or in another example r, could be set to equal the minimum bend radius of the fibre cable and the increased radius of the corresponding bend of the longitudinal axis of the cable simply used as a small safety margin.

30 Figures 2 to 5 are schematic end elevations showing different configurations of the package device of Figure 1. In Figure 2, circularly symmetric guide formations are used in the context of a fibre ribbon cable 30. In Figure 3, again circularly symmetric guide formations are used but this time with a circularly symmetric cable 30' with a circularly symmetric strengthening member 50'.

Figures 4 and 5 show similar arrangements but with the curved guide formations 60 inhibiting bending only in two opposing directions.

Finally, Figure 6 is a schematic cross section of an optical fibre connector in which an optical fibre, cable or ribbon cable 100 is inhibited from bending by guide formations 160 5 and a strengthening member 150. A threaded portion I 10 is provided to allow the connector to be screwed into a corresponding connector of the opposite gender.

Claims

1. An optical device having an outer wall through which one or more optical fibres are routed, the device comprising:

5 a flexible strengthening member attached to the optical fibre adjacent to an outer aspect of the wall; and guide formations protruding from the wall, the guide formations being positioned and shaped with respect to the strengthening member so as to prevent at least a part of the strengthening member adjacent to the wall from bending, in at least one direction, at a bend 10 radius less than a predetermined minimum radius.

2. A device according to claim 1, in which the guide formations are disposed on at least two opposing sides of the strengthening member.

15 3. A device according to claim 2, in which the guide formations form an opening which narrows towards the wall.

4. A device according to any one of the preceding claims in which the guide fon-nations are curved so that if the strengthening member abuts the guide formations in the at least one 20 direction, the optical fibre follows a curve having a radius greater than or equal to the predetermined minimum radius.

5. A device according to any one of the preceding claims, in which the guide formations are arranged so as to prevent at least a part of the strengthening member adjacent to the wall 25 from bending, in any direction, at a bend radius less than a predetermined radius.

6. A device according to claim 5, in which the guide formations are circularly symmetric.

3o 7. A device according to any one of the preceding claims, in which two or more optical fibres are attached to a common strengthening member.

8. A device according to claim 7, in which the two or more optical fibres are formed into a single cable.

9. A device according to claim 8, in which the cable is an optical fibre ribbon cable.

10. A device according to any one of the preceding claims, the device being a package 5 for an optical component.

11. A packaged optical component comprising an optical component housed in a device according to claim 10.

i o 12. A packaged optical component according to claim 11, the component being an integrated optical component.

13. A packaged optical component according to claim 12, the component being an arrayed waveguide grating and/or a variable optical attenuator and/or an optical switch.

14. A device according to any one of claims I to 9, the device being an optical connector.

15. An optical device substantially as hereinbefore described with reference to Figures I and 2, Figures I and 3, Figures I and 4 and/or Figures I and 5 of the accompanying drawings 16. An optical connector substantially as hereinbefore described with reference to Figure CD 6 of the accompanying drawings.