Patent Publication Number: US-2004042725-A1

Title: Temperature compensating waveguide package

Description:
FIELD OF THE INVENTION  
       [0001] The present invention relates broadly to an optical waveguide packaging device.  
       [0002] The present invention will be described herein with reference to an optical fibre, and particularly with reference to a grating structure incorporated within the optical fibre. However, it will be appreciated that the present invention does have broad applications, including e.g. to planar waveguides and to other optical structures including e.g. tapered waveguide structures or modulator structures.  
       BACKGROUND OF THE INVENTION  
       [0003] As a result of the increased utilisation of optical components in e.g. communications networks, there is a general need to provide suitable packaging devices for optical components, e.g. packaging devices for optical fibre devices. Preferably, such packaging devices also have temperature compensating characteristics to compensate for temperature induced changes in an optical property of the optical component.  
       [0004] In prior art packaging devices relative movement of different thermal expansion coefficient (TEC) materials is typically utilised to actuate a temperature compensating mechanism. One of the problems with proposed packaging designs of that type is that they involve forming a permanent link/bond between the different TEC materials through bonding processes such as welding. Apart from creating potential points of failure, such processes also make those designs less suitable for mass-production, in particular of multi-waveguide packages.  
       [0005] Also, there is a need for facilitating tuning of optical devices contained in a waveguide package to meet required specifications. In the tuning of optical components, operational tuning is initially conducted to set the operation point of the optical device, while functional tuning may then be performed to tune the optical device around the operational point.  
       [0006] Preferred embodiments of the present invention seek to address at least one of those general needs.  
       SUMMARY OF THE INVENTION  
       [0007] In accordance with a first aspect of the present invention there is provided a packaging device for an optical waveguide, the device comprising a first material member, a second material member, at least one lever arm connectable to the waveguide, and a mounting assembly for connecting the lever arm to at least one of the first and/or second material members, the lever arm being arranged, in use, to operate under temperature induced relative movement of the first and second material members in a manner such that strain in the waveguide is controlled to compensate for a temperature induced change in an optical property of the waveguide, and wherein the mounting assembly is arranged, in use, for rotatably mounting the lever arm to said one material member, with a rotational axis substantially perpendicular to said one material member.  
       [0008] The mounting assembly may comprise a cylindrical axis member, one or more bearing balls, or one or more protrusions or indentations formed on said one material member and/or the lever arm.  
       [0009] The lever arm may be integrally formed with the other one of the first and second material members. A flexure may be formed between the lever arm and said other material member, for facilitating pivotal movement of the lever arm around said other material member.  
       [0010] In one embodiment, the first and second material members are disposed in a substantially co-extending manner.  
       [0011] The lever arm may be disposed in a manner such that, in use, it extends towards the waveguide from the first and second material members. Alternatively, the lever arm may be disposed in a manner such that the arm extends between the first and second materials, and the packaging device is arranged, in use, in a manner such that the waveguide is located substantially between the first and second material members.  
       [0012] The packaging device may comprise a pair of lever arms disposed at opposing end portions of the first and/or second material members, each lever arm of the pair being connectable to the waveguide, and a further mounting assembly for connecting the second lever arm of the pair to said one material member.  
       [0013] The packaging device may comprise a plurality of first material members and a plurality of lever arms, each lever arm being connectable to a corresponding one of a plurality of waveguides, and a mounting assembly for mounting the lever arms to one of the first material members and/or to the second material member, each lever arm being arranged, in use, to operate under temperature induced relative movement of one of the first material members and the second material member in a manner such that strain is induced in the corresponding waveguide to compensate for temperature induced changes in an optical property of the corresponding waveguide. The packaging device may comprise a plurality of pairs of lever arms, each lever arm of one pair being connectable to the same waveguide, and a further mounting assembly for mounting the second lever arms of the pairs to said one material member.  
       [0014] In preferred embodiments, the lever arm or arms are loaded to a degree chosen such that, in use over a selected temperature range, no play exists in the mounting assembly or assemblies between the lever arm or arms and said one material member.  
       [0015] In one embodiment, the mounting assembly or assemblies comprise corresponding pairs of protrusions and indentations formed on the lever arm or arms and said one material member. Advantageously, said other material member is flexible and, in use, bent for effecting the loading of the lever arm or arms, and the lever arm or arms move pivotally around said one material member as a result of changes in the curvature of said other material member which in turn result from the temperature induced relative movement of the material members. A flexure may be formed along the length of said other material member, for facilitating the bending of said other material member.  
       [0016] Preferably, the device is initially tuned to a pre-selected state by adjustment of the strain exerted by the lever arm or arms on the waveguide or waveguides for tuning of an optical structure or structures incorporated in the waveguide or waveguides.  
       [0017] The strain in the waveguide or waveguides may be non-reversibly adjusted by applying a transverse compressive load above a non-elastic deformation threshold to the first or/and second material members.  
       [0018] The lever arm or arms may be arranged, in use, to operate under a tuning means of the packaging device. The tuning means may be of a latchable or non-latchable type, i.e. requiring operation either only for switching into a different device state, or continuous operation to maintain or alter a particular device state.  
       [0019] The tuning means may comprise an actuator e.g. a piezo-electric member or a mechanically or electrically driven pico-motor. The actuator may be arranged, in use, to act upon at least one of the first and second material members for effecting movement of the lever arm or arms.  
       [0020] The waveguide may be in the form of an optical fibre.  
       [0021] In accordance with a second aspect of the present invention there is provided a packaging device for a plurality of optical waveguides, the device comprising a plurality of first material members, a second material member, a plurality of lever arms, each lever arm being connectable to a corresponding one of the waveguides, and a mounting assembly for mounting the lever arms to at least one of the first material members and/or to the second material member, each lever arm being arranged, in use, to operate under temperature induced relative movement of one of the first material members or the second material member in a manner such that strain is induced in the corresponding waveguide to compensate for temperature induced changes in an optical property of the corresponding waveguide.  
       [0022] The device may comprise a plurality of pairs of lever arms, each lever arm of one pair being connectable to the same waveguide, and a second mounting assembly for mounting the second lever arms of the pairs to said one material member.  
       [0023] The mounting assembly or assemblies may each comprise a plurality of mounting elements associated with different ones of the lever arms.  
       [0024] In accordance with a third aspect of the present invention there is provided a packaging device for an optical waveguide, the device comprising a first material member, a second material member, at least one lever arm connectable to the waveguide and a mounting assembly for connecting the lever arm to at least one of the first and second material members, the lever arm being arranged, in use, to operate under temperature induced relative movement of the first and second material members in a manner such that strain in the waveguide is controlled to compensate for a temperature induced change in an optical property of the waveguide, wherein the other material member is flexible and, in use, bent for effecting loading of the lever arm to a degree chosen such that, in use over a select temperature range, no play exists in the mounting assembly between the lever arm and said one material member, and wherein the lever arm is arranged, in use, to move pivotally around said one material member as a result of changes in the curvature of said other material member, which in turn result from the temperature induced relative movement of the material members.  
       [0025] The device may comprise a plurality of lever arms and a plurality of said other material members, and wherein each lever arm is arranged, in use, to move pivotally around said one material member as a result of changes in the curvature of one of said other material members, which in turn result from the temperature induced relative movement of the material members.  
       [0026] The device may comprise a pair or pairs of lever arms disposed at opposing end portions of the first and/or second material members, each lever arm of each pair being connectable to the or one of the waveguides, and a second mounting assembly for connecting the second lever arm or arms of the pair or pairs to said one material member.  
       [0027] In accordance with a fourth aspect of the present invention there is provided a packaging device structure for a plurality of optical waveguides, the device structure comprising a plurality of packaging devices in accordance with any one of the first, second, and third aspect of the present invention. 
     
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
     [0028] Preferred forms of the present invention will now be described, by way of example only, with reference to the accompanying drawings.  
     [0029]FIG. 1 is a schematic diagram illustrating a fibre packaging device embodying the present invention.  
     [0030]FIG. 2 is a schematic diagram illustrating an exploded view of another fibre packaging device embodying the present invention.  
     [0031]FIG. 3 is a schematic diagram illustrating another fibre packaging device embodying the present invention.  
     [0032]FIG. 4 is a schematic diagram illustrating another fibre packaging device embodying the present invention.  
     [0033]FIG. 5 is a schematic diagram illustrating another fibre packaging device embodying the present invention.  
     [0034]FIG. 6 is a schematic diagram illustrating another fibre packaging device embodying the present invention.  
     [0035]FIG. 7 is a schematic diagram illustrating another fibre packaging device embodying the present invention.  
     [0036]FIG. 8 is a schematic diagram illustrating another fibre packaging device embodying the present invention.  
     [0037]FIG. 9 is a schematic diagram illustrating another fibre packaging device embodying the present invention.  
     [0038]FIG. 10 is a schematic diagram illustrating another fibre packaging device embodying the present invention.  
     [0039]FIG. 11 is a schematic diagram illustrating another fibre packaging device embodying the present invention.  
     [0040]FIG. 12 is a schematic diagram illustrating another fibre packaging device embodying the present invention. 
    
    
     DETAILED DESCRIPTION OF THE EMBODIMENTS  
     [0041] The preferred embodiments described provide temperature compensated waveguide packaging devices which do not require the formation of permanent links/bonds between different TEC material members by bonding processes such as welding.  
     [0042] The packaging device  10  comprises a first beam  12  formed from a high thermal expansion coefficient (TEC) material, and a second beam  14  formed from a lower TEC material. The first and second beams,  12 ,  14 , substantially coextend one above the other.  
     [0043] The packaging device  10  further comprises a pair of lever arms  16 . Each lever arm  16  is pivotally connected to the beam  12  (high TEC) at opposing ends thereof. The pivotal connection is effected through axis members  18 .  
     [0044] Furthermore, each lever arm  16  is connected to the upper beam  14 , (lower TEC) again at opposing ends thereof. The connection to the upper beam  14  is effected utilising axis members  20 .  
     [0045] The free ends  22  of the lever arms  16  are connected to an optical fibre  24  utilising a suitable adhesive material  26 . An initial tension is applied to the optical fibre  24  either prior to curing the adhesive material  26 , during the curing, or afterwards. In both cases, the operational tuning of the optical structure incorporated in the waveguide is further performed by applying a transverse compressive load to beam  12  and/or beam  14  to induce permanent longitudinal deformation of the beams. In the embodiment shown in FIG. 1, the arms  16  are each inclined inwardly with respect to the coextending beams,  12 ,  14 .  
     [0046] In the packaging device  10 , temperature induced refractive index changes in the optical fibre  24  can be compensated for by utilising a lever mechanism operating under temperature induced relative movement between the high TEC material beam  12  and the lower TEC material beam  14 .  
     [0047] More particularly, if a temperature increase is experienced in the ambient around the packaging device  10 , a reduction in tension (indicated by arrows  28 ) is induced in the optical fibre  24 , caused by a greater expansion of the high TEC material beam  12  (as indicated by arrows  30 ) compared with the lower TEC bar  14 . As will be readily appreciated by a person skilled in the art, the greater expansion of beam  12  effects movement of the respective ends  22  of the arms  16  towards each other, thereby inducing the compressive strain in the optical fibre  24 . Through the elasto-optic effect, the compressive strain is used to compensate for the temperature induced refractive index change in the optical fibre  24 .  
     [0048] It will also be appreciated by the person skilled in the art, that in the packaging device  10  through suitable selection of the relevant dimensions  32 ,  34  in the lever mechanism, the compensating strain caused by the thermally induced relative movement between beams  12  and  14  can be chosen to suite various compensating requirements. Accordingly, the present invention can provide a versatile packaging design, which can be constructed from the same components which can be mass produced.  
     [0049] It is noted that as a result of the initial tensioning of the optical fibre  68  (see above), it can be ensured that during operation of the waveguide packaging device to compensate for temperature induced changes, the compressive strain exerted onto the optical fibre by the lever mechanism in case of a temperature increase will not result in any bending of the optical fibre, which would be detrimental to the device. Thus, the initial tensioning parameters are preferably appropriately chosen to accommodate temperature compensation over a given temperature range.  
     [0050] In another packaging device  50  embodying the present invention and shown in FIG. 2, a high TEC material member  52  is disposed within a U-shaped lower TEC material member  54 . The high TEC material member  52  comprises two lever arm end portions  56 . Flexures  58  are formed between the respective end portions  56  and a main body  60  of the high TEC material member  52 . The flexing connecting portions  58  effect a pivotal connection between the lever arm end portions  56  and the main body  60  of the high TEC material member  52 .  
     [0051] The lever arm end portions  56  are connected to the U-shaped lower TEC material member  54  by way of a mounting assembly in the form of cylinders  62 ,  64 , received in openings  66 ,  67  formed in the lever arm end portions  56  and the U-shaped lower TEC material member  54  respectively.  
     [0052] An optical fibre  68  is mounted within grooves  70  formed in the lever arm end portions  56  by way of a suitable adhesive material.  
     [0053] An initial tension is applied to the optical fibre  68  either prior to curing the adhesive material, during curing, or afterwards. In both cases, the operational tuning of the optical structure incorporated in the waveguide is further performed by applying a transverse compressive load to the higher TEC member  52  to induce permanent longitudinal deformation of the beams.  
     [0054] In the packaging device  50 , temperature induced refractive index changes in the optical fibre  68  can be compensated for by utilising a lever mechanism operating under temperature induced relative movement between the high TEC material member  52  and the lower TEC material member  54 .  
     [0055] More particularly, if a temperature increase is experienced in the ambient around the packaging device  50 , a reduction in tension (indicated by arrows  78 ) is induced in the optical fibre  68 , caused by a greater expansion of the high TEC material member  52  (as indicated by arrows  74 ) compared with the lower TEC member  54 . As will be readily appreciated by the person skilled in the art, the greater expansion of member  52  effects movement of the respective ends of lever arm end portions  56  towards each other, thereby inducing compressive strain in the optical fibre  68 . Through the elasto-optic effect, the compressive strain is used to compensate for the temperature induced refractive index change in the optical fibre  68 .  
     [0056] It will also be appreciated by the person skilled in the art, that in the packaging device  50  through suitable selection of the relevant dimensions in the lever mechanism, the compensating strain caused by the thermally induced relative movement between members  52  and  54  can be chosen to suite various compensating requirements. Accordingly, the present invention can provide a versatile packaging design, which can be constructed from the same components which can be mass produced.  
     [0057] It is noted that as a result of the initial tensioning of the optical fibre  68  (see above), it can be ensured that during operation of the waveguide packaging device to compensate for temperature induced changes, the compressive strain exerted onto the optical fibre by the lever mechanism in case of a temperature increase will not result in any bending of the optical fibre, which would be detrimental to the device. Thus, the initial tensioning parameters are preferably appropriately chosen to accommodate temperature compensation over a given temperature range.  
     [0058] As can be seen from FIG. 2, the design of the connection between the lever arm end portions  56  and to the U-shaped lower TEC material member  54  facilitates a package device construction in which portions of the U-shaped lower TEC material member  54  can be utilised to cover the “lever mechanism”. In the preferred embodiment shown in FIG. 2, this enables manufacturing of a more securely stackable packing device, in as much as the U-shaped lower TEC material member  54  can function as a secondary package substantially enclosing the high TEC material member  52  comprising the main body  60  and the lever arm end portions  56 .  
     [0059] In an alternative embodiment shown in FIG. 3, axis members are provided in the form of bearing balls  100 . Each bearing ball  100  is received between one of the openings  67  formed in the U-shaped lower TEC material member  54  and one of the openings  66  formed in the lever arm end portions  56 .  
     [0060] In yet another embodiment, the lever arm end portions  56  can be rotatably mounted within the U-shaped lower TEC material member  54  by way of protrusions formed on internal walls thereof, which are received in corresponding openings formed in the lever arm end portions  56 .  
     [0061] In another embodiment shown in FIG. 4, a packaging device  110  comprises a tuning means in the form of pico-motor  112  connected to a centre portion  114  of a higher TEC material member  116 . The material member  116  comprises two arm portions  118 ,  120  pivotally connected to the main portion of the first material member  116  by way of flexures  122 ,  124  respectively. Two further flexures  126 ,  128  are formed on either side of the centre portion  114  of the material member  116 .  
     [0062] The respective arms  118 ,  120  are connected to a U-shaped lower TEC material member  130  by way of axis members in the form of cylinders  132 ,  134 .  
     [0063] An optical fibre  136  is mounted within grooves located at end portions of the respective arms  118 ,  120  by way of a suitable epoxy.  
     [0064] It will be appreciated by a person skilled in the art that through adjustment of the pico-motor  112 , upward and downward movement of the centre portion  114  of the material member  116  will induce strain in the optical fibre  136  byway of the arm portions  118  and  120 .  
     [0065] Turning now to FIG. 5, in another embodiment of the present invention a waveguide packaging device  200  comprises an widened U-shaped low TEC material member  202 , with a plurality of high TEC material members, e.g.  204 , mounted therein.  
     [0066] A plurality of optical fibres e.g.  206 , are mounted between respective arm portions, e.g.  208 ,  210  of the material members, e.g  204 . It will be appreciated by a person skilled in the art that each individual high TEC material member e.g.  204  operates in conjunction with the U-shaped low TEC material member  202  as described above with reference to the other embodiments in FIGS.  2  to  4 , to provide temperature compensated packaging of the individual optical fibres e.g.  206 . The packaging device  200  further comprises a dedicated secondary package structure in the form of a box  201  and corresponding lid  203 . Grooves e.g.  205  are provided on the inner surface of the lid, for feed-through of the optical fibres e.g.  206 . Appropriate support/feedthrough structures for the optical fibres extending from the box  201  may be provided.  
     [0067] Furthermore, it will be appreciated by the person skilled in the art that through variation of the configuration of the respective arm portions e.g.  208 ,  210 , different compensation characteristics can be realised for the individual optical fibres.  
     [0068] In another embodiment, one or more of the high TEC material members  204  can be provided with tuning means to facilitate operational or functional tuning (compare FIG. 4 for single-fibre tunable embodiment).  
     [0069] In yet another embodiment shown in FIG. 6, a packaging device  250 , comprises a substantially U-shaped low TEC material member  252  enveloping only some of a plurality of high TEC material members e.g.  254  and associated lever mechanisms e.g.  256 , while further high TEC material members e.g.  258  and associated lever mechanisms e.g.  260  are provided on either side outside of the U-shaped material member  252 .  
     [0070] In such an embodiment, the axis members in the form of cylinders  262 ,  264  are being supported at intermediate points along their length, thereby reducing the likelihood of bending of those cylinders  262 ,  264  which may deteriorate the overall packaging device performance. Such an embodiment may, therefore, be particularly useful where a large number of optical fibres are to be independently mounted within the one packaging device. It is noted that overall protection/covering of the first and second material members and associated lever mechanisms can, in such embodiments, still be provided by way of a secondary package (not shown).  
     [0071] In FIG. 7, a single lever mechanism embodiment of the present invention is shown. A packaging device  700  comprises a high TEC material beam  702  connected to a low TEC material plate  704  by way of a suitable axis-type connections  706 . A lever arm  708  is formed integrally with the beam  702  with a flexure  709  between the beam  702  and the lever arm  708 . An optical fibre  710  is mounted between a support cantilever  712  formed on the plate  704  and the top portion  714  of the lever arm  708 . A base portion  716  of the material plate  704  is utilised as a stand support for the packaging device  700 . Because of the design of the connection between the lever arm  708  and the low TEC material plate  704  the lever arm  708  does not have to be connected at an end portion of the end plate  704 . Therefore, the plate  704  can be extended to cover the overall lever mechanism from one side. It will be appreciated by the person skilled in the art that, in an alternative embodiment, a U-shaped “plate” can be utilised as the low TEC material member, thus enabling covering of the lever mechanism from both sides.  
     [0072] In another embodiment of the present invention shown in FIG. 8, a waveguide packaging device  300  comprises a low TEC material member  304  and a high TEC material member  302 . Two lever arms  306 ,  308  are formed integrally with the material member  302 . The mounting assembly in this embodiment comprises two wedge shaped end portions  310 ,  312  which engage corresponding wedge shaped indentations  314 ,  316  formed on the lever arms  306 ,  308  respectively.  
     [0073] The high TEC member  302  is made from an elastic material, whereby the member  302 , in use, is bendable as a result of thermal extension relative to the low TEC member  304 . During assembly of the waveguide packaging device  300 , loading of the lever arms  306 ,  308  is achieved by clipping the material member  302  and with it the lever arms  306 ,  308  onto the low TEC material member  304 , leaving a slight bend in the material member  302  effecting the loading.  
     [0074] The lever arms  306 ,  308  can turn in a bell crank-type arrangement around the low TEC member  304 . An optical fibre  332  is mounted on and between top portions  324 ,  326  of the lever arms  306 ,  308  respectively by way of a suitable epoxy (not shown).  
     [0075] In operation, when e.g. a temperature increase is experienced, the high TEC member  302  will expand longitudinally to a larger degree than extension in that direction experienced by the low TEC member  304 , as indicated by arrows  320 ,  322 . This results in a reduction of the curvature of the material member  302  as indicated by arrow  323 . As a result, the wedged lever arms  310 ,  312  of the member  304  will act as fulcra on which the lever arms  306 ,  308  turn.  
     [0076] Accordingly, the top portions  324 ,  326  of the end portions  306 ,  308  respectively will move towards each other, as indicated by arrows  328 ,  330 , which results in strain being induced in the optical fibre  332  mounted on and between the top portions  324 ,  326 . Thus, the optical properties of the optical fibre waveguide  332 , which e.g. incorporates a reflection grating (not shown), can be stabilised over a selected temperature range through strain induced changes in the optical fibre waveguide  332  (and thus the reflection grating) to compensate for the temperature induced changes.  
     [0077] The device  300  is arranged in a manner such that the high TEC member  302  is initially loaded during assembly to a degree chosen such that, in use, over a selected temperature range, no play exists between the end portions  310 ,  311  and the corresponding indentations  314 ,  316 .  
     [0078] Furthermore, operational tuning of the device  300  may be performed by applying a transverse compressive load above non-elastic deformation threshold to the lower TEC member  304  and/or the high TEC member  302 , whereby the strain in the optical fibre  332  is non-reversibly adjusted.  
     [0079] In FIG. 9, in another embodiment a waveguide packaging device  400  comprises a low TEC material member  404  and a high TEC material member  408 . Two lever arms  406 ,  407  are integrally formed with the material member  408 . The material member  404  comprises two wedge shaped end portions  410 ,  412  which engage corresponding wedge shaped indentations  414 ,  416  formed in the lever arms  406 , 407  respectively. A flexure  418  is formed in the middle of the material member  408 . The flexure  418  facilitates bending/curving of the material member  408  for effecting loading of the lever arms  406 ,  407  (compare embodiment described above with reference to FIG. 8). An optical fibre  432  is mounted on and between top portions  424 ,  426  of the lever arms  406 ,  407  respectively by way of a suitable epoxy  434 .  
     [0080] In operation, when e.g. a temperature increase is experienced, the material member  408 , will extend longitudinally to a larger degree than extension in that direction experienced by the low TEC member  404 , as indicated by arrows  420 ,  422 . This results in a reduction of the bending/curvature of the material member  408  (around the flexure  418 ), as indicated by arrow  423 . As a result, the lever arms  406 ,  407  turn around/on the wedge shaped end portions  410 ,  412  of the member  404  acting as fulcra.  
     [0081] Accordingly, the top portions  424 ,  426  of the lever arms  406 ,  407  respectively will move towards each other, as indicated by arrows  428 ,  430 , which results in strain being induced in the optical fibre  432  mounted on and between the top portions  424 ,  426 . Thus, the optical properties of the optical fibre waveguide  432 , which e.g. incorporates a reflection grating (not shown), can be stabilised over a selected temperature range through strain induced changes in the optical fibre waveguide  432  (and thus the reflection grating) to compensate for the temperature induced changes.  
     [0082] In the embodiment shown in FIG. 9, the device  400  is arranged in a manner such that the two lever arms  406 ,  407  are initially loaded during assembly to a degree chosen such that, in use over a selected temperature range, no play exists between the indentations  414 ,  416  and the end portions  410 ,  412  of the low TEC member  404 .  
     [0083] In an alternative embodiment shown in FIG. 10, a flexure  502  in/on the middle region of a high TEC material member  504  is formed by more gradually reducing the thickness of the material member  504  compared with the embodiment shown in FIG. 9.  
     [0084] The concept of the waveguide packaging devices shown in FIGS. 8, 9 and  10  can be readily extended to a multi-waveguide packaging device  600  as shown in FIG. 11. The multi-waveguide packaging device  600  comprises a plurality of higher TEC material bellcrank-type arrangements e.g.  602 , relative to a single lower TEC material member  604  extending between lever arms e.g.  606 ,  608  of the bellcrank-type arrangements e.g.  602 .  
     [0085] In the waveguide packaging device  600  shown in FIG. 11, the length of the individual lever arms e.g.  606 ,  608  may differ to effect different compensation characteristics. The length variation may be achieved by applying a transverse compressive load above non-elastic deformation threshold to the individual lever arms e.g.  606 ,  608 , above or below the indentations e.g.  609 ,  611 , which engage the lower TEC material member  604 . This can be effected e.g. through pinching. Alternatively, the bellcrank-type arrangements e.g.  602  may initially be manufactured with different length lever arms.  
     [0086] In an alternative embodiment, a multi-waveguide packaging device can comprise a plurality of lower TEC material members. In such an embodiment, each pair of lever arms cooperates with one lower TEC material member for controlling strains in a plurality of optical fibres mounted in the packaging device.  
     [0087] In a further embodiment shown in FIG. 12, a waveguide packaging device  900  comprises a lever arm in the form of an end portion  902  of a higher TEC material member  904 . The packaging device  900  further comprises a lower TEC material member  906 . Both material members  904 ,  906  are connected to a base portion  908  of the packaging device  900 .  
     [0088] A flexure region  912  is formed between the end portion  902  and the longitudinal main body  910  of the material member  904 , to facilitate movement (indicated by arrow  914 ) of the lever arm  902  under thermal expansion/contraction of the high TEC material member  904 . A waveguide in the form of an optical fibre  916  is mounted in the packaging device  900  on and between a top portion  918  of the lever arm  902  and a top portion  920  of the base member  908  respectively by way of a suitable epoxy (not shown). It will be appreciated by the person skilled in the art that the operation of the waveguide packaging device  900  is generally similar to the operation of the embodiments described above with reference to FIGS.  8 - 11 , but with a single-lever arrangement. Furthermore, it will be appreciated by the person skilled in the art that in an alternative embodiment of the present invention, a multi-waveguide packaging device comprising a plurality of single-lever arrangements can be provided.  
     [0089] It will be appreciated by the person skilled in the art that numerous variations and/or modifications may be made to the present invention as shown in these specific embodiments without departing from the spirit or scope of the invention as broadly described. The present embodiments are, therefore, to be considered in all respects to be illustrative and not restrictive.  
     [0090] E.g., where it is desired to amplify the temperature induced changes in optical properties of a waveguide mounted in a device embodying the present invention, the relative TEC properties of the different material member providing relative movement for moving the lever arms turn can be reversed compared to the embodiments described above.  
     [0091] In the embodiments described, the packaging devices are arranged in a manner such that the arms of the lever mechanisms are loaded to a degree chosen such that, in use over a selected temperature range, no play exists in the connection between the arm and said one material member.  
     [0092] One of the advantages of the present invention as embodied in the preferred embodiments described above is noted in the following. Because a mounting assembly is used to connect the lever arm to one of the material members, these typically different material components (because of the nature of the temperature compensating package design) can be rotatably/pivotally connected to each other without the need to form a direct material to material connection, such as e.g. through welding. It will be appreciated by a person skilled in the art that any direct link between the material components which at the same time provides a rotatable/pivotable connection is impractical as e.g. locating the welding line in a flexure region between the different materials would create a point of potentially high likelihood of failure.  
     [0093] In the claims that follow and in the summary of the invention, except where the context requires otherwise due to express language or necessary implication, the word “comprising” is used in the sense of “including”, i.e. the features specified may be associated with further features in various embodiments of the invention.