WO2002041051A2

WO2002041051A2 - Optical circuit apparatus

Info

Publication number: WO2002041051A2
Application number: PCT/GB2001/005023
Authority: WO
Inventors: Mike Moody
Original assignee: Marconi Optical Components Limited
Priority date: 2000-11-15
Filing date: 2001-11-14
Publication date: 2002-05-23
Also published as: WO2002041051A3

Abstract

An optical circuit, such as an erbium doped fibre amplifier, incldes a housing (1) for optical fibre (8) and components (28, 29 and 30). Resiliently deformable material (9) contained within the housing (1) maintains the components (8, 28, 29 and 30).

Description

Optical Circuit Apparatus

This invention relates to an optical circuit apparatus and more particularly, but not exclusively, to an optical amplifier which incorporates erbium doped fibre.

A key component in current optical communication systems is an optical amplifier, which typically includes one or more lengths of erbium doped fibre (EDF), a pumping light source such as a laser and components such as multiplexers, demultiplexers, optical isolators and diodes for monitoring power levels in the amplifier. The components are generally housed together in a housing which has apertures through which optical fibres are extensive to carry optical signals between the components and the external circuit which includes the amplifier. One known fibre amplifier is disclosed in US 6 072 931. In this arrangement, an optical fibre is clamped in the housing and wound around an insert. Clamps and clips are used to hold components of the EDF A (Erbium Doped Fibre Amplifier) in position.

According to the present invention, there is provided an optical circuit apparatus comprising a housing containing resiliently deformable material which holds at least one optical component in position.

Although the invention is particularly applicable to optical amplifiers in which erbium doped fibre is used, it may also be of benefit for other optical or electro-optical circuits which perform functions other than amplification and/or use optical fibres of a different composition. The optical component is held in position by the resiliently deformable material, which may advantageously be of a foam but could be rubber for example. The material provides cushioning for the component against mechanical shock to which the apparatus may be subject during installation or shipping and handling of the apparatus. In addition, the deformable nature of the material permits components of slightly different sizes to be securely located in position whilst using the same layout of resiliently deformable material. For example, in one embodiment of the invention, the material includes a channel having facing walls in which an elongate optical component, such as a multiplexer, is located. The resilient nature of the material serves to hold the component in position as it exerts a bias against it. If some re-design of the optical circuitry is required subsequently, resulting in a different component being used to perform the multiplexing function, this may be implemented using the same configuration of deformable material with any small changes in its dimensions of the new and original components being accommodated by the resilient and deformable nature of the material. Thus, where the material is formed into the required configuration by for example machining or a moulding process, it is not necessary to re- programme or re-tool to produce a different layout to take into account such design changes.

The design flexibility afforded by using the deformable material may permit a single channel of nominally the same width between the walls for its entire depth to be used to position two components having different widths and located one on top of the other. Both components may be held firmly in position by the material even though one may be of a slightly larger diameter than another. Of course, the deformable material may be machined or otherwise shaped so as to present differently dimensioned regions to permit components having greater dimensional differences to be located. This may be done by having a step or steps in the surface of the wall or walls adjacent to the components.

A further advantage of using the invention is that the material may by itself be sufficient to hold the optical component, or components, in position without any additional fixing means. When it becomes necessary to replace a component, say, because of malfunction, to comply with service intervals or to replace it with an upgraded component, this may be done easily by a service engineer without having to also remove clamping arrangements or prise the component from an adhesive, say, to locate it in a position, as would tend to be the case with previous arrangements in which fixed rigid walls are used to define positions for components. Thus, the removed component is less likely to be damaged and there is a reduced risk of disturbing or damaging other components included in the apparatus or damaging the deformable material. Similarly, when installing or re-installing a component, this can be done easily as only a push-fit need be required. If the replacement component is not initially then located in the correct position, it may easily be re-adjusted or removed and re-inserted so as to ensure that it is finally correctly located. This ease of installation and re-adjustment is also of benefit, of course, for the initial assembly of the apparatus during manufacture.

In order to assist in removing components, in one preferred embodiment, a notch or notches are placed in an upper surface of a wall or walls of the material which define a channel within which is located a component. This enables an engineer to remove the component by levering it up with a tool placed in the notch and under the component. Additional notches may be used as visual guides for correct location of the component when it is inserted or replaced in a channel.

The resiliently deformable material is preferably a foam as such material may be easily machined into a complex shape, provides a good cushioning for the components and may also be obtained with anti-static or flame-resistant properties. A rubber material may be used as an alternative but may not be As suited to a machining or moulding process.

Advantageously, the resiliently deformable material is provided as an insert. The insert is manufactured separately to the housing and may be formed so as to provide locations surfaces for more than one optical component. In one preferred arrangement, the insert defines channels into which elongate optical components may be located and also includes circular, curved or other shaped surfaces around which relatively long lengths of optical fibre may be wound. The insert may be made to conform closely with the interior dimensions of the housing so that it is securely positioned therein, advantageously as a push-fit, and in turn securely locates the components. The positioning of the insert may be aided by rigid upstanding portions from a wall or walls of the housing. For example, an additional portion may be machined in or bolted to one of the major surfaces of the housing and the insert has a correspondingly shaped aperture which locates over the upstanding portion. In addition, such upstanding portions may also be used to support the resiliently deformable material to provide a fixed surface against which the material bears. In one advantageous embodiment a component is located between two or more surfaces of the material but in some embodiments it may be located immediately adjacent a solid wall, for example an interior surface of the housing, and also adjacent the resiliently deformable material.

Where an upstanding portion is used to give a surface for location of the optical component or to give support to the material holding the component in position, such upstanding portion may have a curved surface to against which fibres within the housing are located.

Preferably, means for heating the optical component is provided, in which case the deformable material also provides thermal insulation for the component. The heating means may take the form of a heating tape. The deformable material may be arranged to locate the heating means in a predetermined position with respect to the optical component, for example in intimate contact. This embodiment is especially suitable for heating spools of optical fibre. Previously, such spools had to be formed as a self- contained unit with a heater and then sealed to provide thermal insulation. A disadvantage of this arrangement was a limited flexibility of reworking of the fibre, because the whole unit had to be disassembled. This feature of the invention permits ease of access to both the component and the heater without compromising the quality of thermal insulation.

Advantageously, there may be an aperture through the resiliently deformable material via which heat may be conducted from components included within the housing to a surface of the housing, which may have external cooling fins. In a particularly advantageous embodiment, the deformable material is formed to present an oval wall around the outside of which optical fibre is wound. Normally, optical fibre is received from its manufacturer wound on a generally circular former. By using an oval wall within the housing, it tends to provide a tighter fit for the optical fibre at those parts where the oval has a larger diameter compared to its small diameter, thus aiding in secure positioning of the optical fibre.

According to a second aspect of the invention, an optical circuit apparatus comprises a housing including an oval wall around which is located optical fibre. The wall may preferably be of a deformable material, such as a foam or rubber but a fixed wall, such as one made of metal, will also give advantages in securing the optical fibre. The oval wall may be of a smoothly rounded shape having a larger diameter arranged normal to its shortest diameter. It may be elliptical, for example.

In previously known constructions, optical fibre fed into the housing via an aperture through a wall of the housing has required a complex connection taking the form of various clamping rings or alternatively a screw fitting to give a strong, secure fixture. According to a feature of this invention, a sleeve of rubber or some other deformable material is located over the portion of a fibre where it passes through an aperture into the interior of the housing. The rubber tends to grip the wall of the aperture and may be arranged to meet normal design requirements concerning tensile strength whilst being of simple construction and easy to assemble. For example, in one embodiment, where the housing is in two parts, a slot across the upper surface of a wall in one part which is to fit adjacent a surface of the other part. The rubber sleeve lies proud of the slot and when the matching top plate or another wall is fastened into position, the rubber is squeezed and put under compression to make a tight fit. Advantageously, the slot also has a part which is normal to the direction of the fibre. When the rubber sleeve is placed under compression when the two parts of the housing are joined, the rubber tends to move outwardly into the normal part of the groove, giving additional bite and thus further increasing the security of fixing.

According to a third aspect of the invention, an optical circuit apparatus comprises a housing having an aperture therethrough via which an optical fibre is extensive, with deformable material being located around the outside of the fibre where it passes through the aperture, being deformed in situ so as to give increased purchase and fixing the fibre in position.

In one advantageous embodiment, additional deformable material is used so as to further secure components, particularly fibres, within the housing. Such additional resilient means may take the form of a single component or may be a plurality of separate components.

Some ways in which the invention may be performed are now described by way of example with reference to the accompanying drawings in which:

Figure 1 is schematic plan view of the interior of the apparatus in accordance with the invention;

Figure 2 shows the deformable insert; and Figure 3 shows another apparatus in accordance with the invention.

With reference to Figures 1 and 2, an optical fibre amplifier includes a housing construction 1 which is in two parts, only the lower housing 2 being shown in Figure 1 to enable the interior to be viewed. The housing 2 is of generally rectangular shape having curved corners and a surrounding wall 3. The wall 3 has apertures 4 therein via which the upper part of the housing construction 1 is attached to the lower part 2 via screws (not shown). The housing 2 includes an upstanding portion 5 which in cross- section has a straight side 6 and a curved side 7, the lower part of the portion 5 being in intimate contact with the floor of the housing 2.

A foam insert 9 is located as a push-fit within the interior of the part 2 of the housing 1 and is shown in Figure 2. The foam is resiliently deformable and machined so as to give an aperture 10 therein which corresponds in cross-sectional area to the cross-sectional shape of the upstanding portion 5. This portion 5 thus partially locates, in conjunction with the interior surfaces of the housing 2, the insert 9. In addition to the aperture 10, the insert 9 includes two larger apertures 11 and 12 of oval shape which are aligned with circuit boards 13 and 14 mounted on the floor of the part 2 of the housing 1. Circuit boards 13 and 14 carry lasers 15 and 16, optical power monitors 17 and 18 and power supplies 19 and 20.

The parts of the insert 9 surrounding the apertures 11 and 12 are machined to give walls 21 and 22, as can be more clearly seen in Figure 3. Erbium doped optical fibre 8 is wound around the outer surfaces of the oval walls 21 and 22. In addition, the insert 9 includes two additional upstanding walls 23 and 24 which are substantially parallel to a long side of the housing 2 and spaced therefrom, giving channels 25, 26 and 27 between the adjacent interior wall of the housing, the foam walls of the insert 9 and the upstanding portion 5.

Heating means (not shown), such as heating tape, may be provided to elevate the temperature of the fibre 8. The foam not only locates the heating means in position, but also provides good thermal insulation.

Elongate optical components 28, 29 and 30 are located between the foam walls and the rigid surfaces of the housing. These components, for example multiplexers and demultiplexers, are securely held in position by the resiliently deformable nature of the foam and require no additional fixation means. The optical fibres 8 connected to the components are also connected to the components mounted on the circuit boards 13 and 14.

Some optical fibres 31, 32 are located in grooves 33, 34 through the wall 3 of the housing 2, thus connecting the EDFA with the surrounding circuitry in which it is included. These grooves also include a portion 35 transverse to them. Each optical fibre extensive through the apertures in the wall 3 is surrounded by sleeves 36, 37. The grooves 33, 34 in which the fibres 31, 32 rest are of slightly less depth than the dimensions of the rubber sleeves 36, 37 and thus, when the top part of the housing is screwed into place, the rubber deforms, extending also into the transverse part 35 of the grooves 33, 34, securely holding the fibres 31, 32 into position. In addition to the insert 9, some further blocks of resilient material are located over the tops of the optical fibre (and heating means) within the housing to hold it in position.

Notches 39, 40 are included in the parts of the walls of the deformable material parallel to the walls of the housing where the elongate optical components 28, 29 and 30 are held. The notches 39, 40 enable an engineer to place a lever under components located between the surfaces to enable components to be removed. In addition, shallow grooves 41, 42 are also included to visually show the limits between which the elongate optical components should be positioned.

Figure 3 shows another embodiment of the invention which includes four lasers 43, 44, 45, 46 in total but again a single insert 47 of resiliently deformable material is used. In this arrangement, a more complex configuration of upstanding walls are included for guiding the optical fibres between the various components.

Claims

1. An optical circuit apparatus comprising a housing containing resiliently deformable material which holds at least one optical component in position.

2. Apparatus as claimed in claim 1 wherein the resiliently deformable material is an insert.

3. Apparatus as claimed in claim 1 or 2 wherein the resiliently deformable material is a foam.

4. Apparatus as claimed in 1, 2 or 3 wherein the resiliently deformable material is configured by machining.

5. Apparatus as claimed in any preceding claim wherein the housing contains at least one of the following optical components: rare earth doped fibre amplifier, multiplexer, de-multiplexer, diode and laser.

6. Apparatus as claimed in any preceding claim wherein an aperture is extensive through the resilient deformable material to an inner surface of the housing to provide a heat sink.

7. Apparatus as claimed in claim 6 wherein the optical component is located adjacent to the aperture.

8. Apparatus as claimed in any preceding claim wherein the optical circuit is an optical amplifier.

9. Apparatus as claimed in any preceding claim and including a wall of rigid material within the housing, the wall providing a surface against which the resiliently deformable material is located.

10. Apparatus as claimed in claim 9 wherein the wall has at least one curved surface against which optical fibre is positioned.

11. Apparatus as claimed in any preceding claim and wherein the housing contains electrical or opto-electronic components.

12. Apparatus as claimed in any preceding claim wherein part of the resiliently deformable material is formed as an oval wall around which optical fibre is wound.

13. Apparatus as claimed in any preceding claim wherein the resiliently deformable material is formed as a channel having two opposing sides with an elongate optical

<- component being located between the sides.

14. Apparatus as claimed in claim 13 and comprising a plurality of channels.

15. Apparatus as claimed in claim 13 or 14 and including an interruption along at least one wall of a channel in which optical fibre is accommodated.

16. Apparatus as claimed in any one of claims 13 to 15 and wherein at least one wall of a channel or channels has a notch to facilitate removal of a component or components located in that channel.

17. Apparatus as claimed in any one of claims 13 to 16 and wherein the sides of the channel are deep enough to accommodate a plurality of stacked optical components.

18. Apparatus as claimed in any preceding claim wherein the optical component is held in position solely by the resiliently deformable material.

19. Apparatus as claimed in any, preceding claim wherein the housing includes an aperture through which an optical fibre passes.

20. Apparatus as claimed in claim 19 wherein the fibre has deformable material around its outer surface where it passes through the aperture.

21.*^■ Apparatus as claimed in claim 20 wherein the deformable material is a rubber sleeve fixed to the outer surface of the fibre.

22. Apparatus as claimed in claim 19, 20 or 21 and wherein the housing includes a groove at the aperture and some of the rubber is extensive into the groove.

23. Apparatus as claimed in any preceding claim and including a locking component to locate the resiliently deformable material in position.

24. Apparatus as claimed in claim 23 wherein the locking component is of the same material as the resiliently deformable material.

25. An optical circuit apparatus comprising a housing containing optical fibre, the housing containing an oval former on which the fibre is wound.

26. Apparatus as claimed in claim 25 wherein the oval former is of foam material.

27. Apparatus as claimed in any preceding claim, further comprising means for heating the optical component, wherein the resiliently deformable material provides thermal insulation for the component.

28. Apparatus as claimed in claim 27, in which the heating means comprises heating tape.

29.' Apparatus as claimed in claim 27 or 28, in which the resiliently deformable material is arranged to locate the heating means in a predetermined position with respect to the optical component.

30. An optical circuit apparatus comprising a housing containing at least one optical component and having an aperture therethrough via which optical fibre is extensive, the fibre having deformable material on its outer surface which grips the wall of the aperture to locate the fibre in position.

31. Apparatus as claimed in claim 30 and including a transverse notch at the aperture, which receives some of the deformed material from around the optical fibre.

32. An optical circuit apparatus substantially as illustrated in and described with reference to the accompanying drawings.