Abstract:
An optical device module includes an optical device, a soaking unit fixed to one surface of the optical device, a heating/cooling unit fixed to one surface of the soaking unit, a heat-insulating unit fixed to one surface of the heating/cooling unit, and a package that houses the optical device, the soaking unit, the heating/cooling unit, and the heat-insulating unit and to which the heat-insulating unit is fixed. The heating/cooling unit heats the optical device using self-generated heat or cools the optical device via the soaking unit.

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS  
       [0001]     This application is based upon and claims the benefit of priority from the prior Japanese Patent Application No. 2003-362530, filed on Oct. 22, 2003, the entire contents of which are incorporated herein by reference.  
       BACKGROUND OF THE INVENTION  
       [0002]     1) Field of the Invention  
         [0003]     The present invention relates to an optical device module that homogenizes temperature distribution in optical devices, such as acousto-optic effect selection filters and arrayed waveguide grating filters, which are used in communication systems that employ wavelength-division multiplexing.  
         [0004]     2) Description of the Related Art  
         [0005]     If wavelength-division multiplexing (WDM) method is used in communication systems, the transmission capacity increases remarkably. Conventionally, in each node that carries out wavelength-division multiplexing, functions of adding and dropping optional wavelengths of light are essential. LiNbO3 waveguide type acousto-optic tunable filters (AOTF) that achieve these functions using acousto-optic effects are attracting attention. The advantage of the AOTF is that multiple wavelengths can be selected simultaneously or wide wavelength band exceeding 100 nanometer (nm) can be selected (see Optorics (1999) No. 5, P155 and The Institute of Electronics, Information and Communication Engineers, OPE 96-123, P79).  
         [0006]     In addition, as optical devices for adding and dropping various optical signals, an optical waveguide grating (AWG), which uses an optical add/drop module array, is also included in main devices under examination. The advantage of the optical add/drop module array is that signal wavelength grids having intervals of 0.8 nm to 0.2 nm can be supported in the device.  
         [0007]     (1)  FIG. 27  illustrates a technique applied in a conventional optical device module (see Japanese Patent Application Laid-Open Publication No. 2001-330811). The AOTF  202  mentioned above includes x-cut LiNbO3 (lithium niobate) substrate  204 , waveguide  206  formed by diffusing Ti (titanium) at high temperature by the Ti-diffusion method on LiNbO3 substrate  204 , splines  208  formed at the positions on the light incoming side and light outgoing side on LiNbO3 substrate  204 , interdigital transducer (IDT)  210  formed by patterning at the position in the light incoming side from the center, polarized beam splitter (PBS)  212  formed on LiNbO3 substrate  204  by the Ti-diffusion method, surface acoustic wave (SAW) guide  211  formed on waveguide  206 , and SAW absorber  213 .  
         [0008]     In the AOTF  202 , incoming light λ 1  through λn are polarized and separated by PBS  212  and at the same time, polarized and synthesized by PBS  212  again. One beam is outputted to a split light port (not illustrated) as split light λ 1  and the other is outputted to a transmitted light port (not illustrated) as transmitted light λ 2  through λn. Moreover, incoming light of wavelength equivalent to the frequency of waveguide  206 , that is, incoming light λ 1  only is polarized and converted by transmitting waveguide  206  and outputted to the split light port.  
         [0009]     (2) Japanese Patent Application Laid-Open Publication No. H8-146369 discloses a technique in which an acousto-optic filter includes a light waveguide for propagating single relative rectilinear polarized light, SAW generating means mounted on the optical waveguide for generating the SAW, and an interaction region which distributes a propagation loss of the SAW spatially and converts a specific wavelength component of the single relative rectilinear polarized light propagated in the light waveguide into rectilinear polarized light, which cross at right angles.  
         [0010]     (3) Japanese Patent Application Laid-Open Publication No. H11-326855 discloses a method for adjusting filter wavelength characteristics by changing the shape and location of a strain-providing section after manufacturing an element with the strain providing section, for correcting local double refraction index of an optical waveguide.  
         [0011]     (4) Japanese Patent Application Laid-Open Publication No. H9-49994 discloses a wavelength filter with an absorber for absorbing an SAW by each reflective electrode to the outside of the optical waveguide by forming the optical waveguide, and excitation electrodes for exciting the SAW on an acousto-optic crystal substrate and disposing reflective electrodes on propagation passage of the SAW.  
         [0012]     (5) Japanese Patent Application Laid-Open Publication No. 2002-90563 discloses a waveguide type optical module, in which a heating/cooling element for controlling the temperature of the waveguide type optical element using a soaking plate and heat buffer layer, is installed on the temperature dependent waveguide type optical element and at least part of the soaking plate is brought into contact with the waveguide type element.  
         [0013]     (6) On the other hand, Japanese Patent Application Laid-Open Publication No. 2000-249853 discloses an arrayed-waveguide grating that uses an optical add/drop module, as shown in  FIG. 28 , and that includes a waveguide chip (including, for example, optical substrate such as silicon, quartz, sapphire, etc.)  224  with arrayed waveguide (channel waveguide)  222  provided with optical add/drop functions on the surface, slab waveguide  226 , and soaking plate  228  which bonds to the rear surface of waveguide chip  224  and soaks waveguide chip  224 , wherein upper plate  230  for optical fiber connection is installed to the surface with arrayed waveguide  222  of waveguide chip  224  formed.  
         [0014]     The AOTF  202  of LiNbO 3  waveguide type according to ( 1 ) generally has heater  234  positioned with soaking plate  232 , for example, copper plate, etc. intervened on the rear surface of x-cut LiNbO 3  substrate  204  as shown in  FIG. 29 , and modularized in package (PKG)  236  together with this heater  234 .  
         [0015]     The heat conductivity in module construction of AOTF  202  can be assumed to be obtained by connecting heat resistance Rln of LiNbO3 substrate  204  as well as ambient (air) heat resistance Rair and heat resistance Rpkg of package  236  in parallel across current source I and external heat source (PKG incoming radiation) Ta as per thermal substrate  204  shown in  FIG. 30  when package  236  is formed by material having comparatively high thermal conductivity.  
         [0016]     This can be shown by the following mathematical expression:  
                     ⁢     Th   =       I   ·     (       (     Rpkg   ·   Rair     )     ⁢     /     ⁢     (       Rp   ⁢           ⁢   kg     +     R   ⁢           ⁢   ln     +   Rair     )       )       +   Ta               (   1   )                       ⁢       Δ   ⁢           ⁢   T     =     Th   -   Ta               (   2   )                 ∴   I     =       Δ   ⁢           ⁢     T   ·       (     1   +     Rpkg   ⁢     /     ⁢   Rair     +     R   ⁢           ⁢   ln   ⁢     /     ⁢   Rair       )     /   Rpkg         ≈     Δ   ⁢           ⁢     T   ·     (     1   ⁢     /     ⁢   Rpkg     )                   (   3   )             
        where Th is the temperature of LiNbO3 substrate  204 .        
 
         [0018]     Based on the above thermal conductivity, the temperature distribution of LiNbO3 waveguide type AOTF  202  is investigated. When the thermal conductivity is high, that is, Rpkg is small, soaking can take place, but (3) indicates that consumption power I of heater  234  increases as Rpkg decreases. That is, even if soaking is carried out, the consumption power of heater  234  increases and it becomes unserviceable.  
         [0019]     On the other hand, when package  236  is formed by material with low thermal conductivity (see  FIG. 31 ), as is the case of the thermal equivalent circuit shown in  FIG. 32A , across current source I and external heat source (PKG incoming radiation) Ta, heat resistance Rln 0  of LiNbO3 substrate  204 , and ambient heat resistance Rair 0  are connected in parallel with heat resistance Rpkg of package  236 . Heat resistance Rln 1  of LiNbO3 substrate  204  and ambient heat resistance Rair 1  in parallel with heat resistance Rpkg of package  236  are further connected in parallel after connecting center heat resistance Rspkg of package  236  across both parallel connections. At the same time, ambient heat resistance Rairout outside package  236  in communication with the ground is connected across heat resistance Rpkg of package  236  and ambient heat resistance Rair 1 .  
         [0020]     This thermal equivalent circuit can be simplified to a circuit as shown in  FIG. 32B  in which heat resistance Rln 0 , heat resistance RairO of ambient in PKG, heat resistance Rpkg of LiNbO3 substrate  204 , and heat resistance Rair 1  of ambient in PKG are connected to center heat resistance Rspkg of package  236  in parallel across external heat source (PKG incoming radiation) Ta and heat resistance Rairout of ambient outside package  236 .  
         [0021]     This can be given by the following mathematical expression: 
 
Δ Tpkg=Ta·Rc /( Rc+Rairout )  (4) 
 
Δ Ts=ΔTpkg·Rln /( Rln+Rair )  (5) 
 
where,  Rln   0 = Rln   1 = Rln· ½
 
 Rair   0 = Rair   1 = Rair· ½
 
∴Δ Ts =( Rc /( Rc+Rairout )·( Rln /( Rln+Rair ))· Ta   (6) 
 
Δ Ts=Ta   19  ( Rpkg/Rairout )·( Rln/Rair )/(( Rpkg/Rair+Rln/Rair+ 1)+(1+ Rln/Rair )· Rpkg/Rairout )  (7) 
 
         [0022]     Now if Rln&lt;&lt;Rair or Rpkg&lt;&lt;Rairout, 
 
ΔTs=0. 
 
         [0023]     Based on the above thermal conductivity, the temperature distribution of LiNbO3 waveguide type AOTF  202  is investigated. In general, since Rln is not extremely smaller than Rair, Rpkg must be extremely smaller than air resistance Rairout, but this is not practical. Consequently, if package  236  is made of material with low thermal conductivity, and the external wall of package  236  is exposed to non-homogeneous outdoor temperature due to heat from an external heat source, the package is susceptible to non-uniformity of the outdoor temperature. Therefore, device (LiNbO3 substrate  204 ) surface temperature is likely to be non-uniform (temperature gradient is generated).  
         [0024]     Analyzing from the heat equivalent circuit shown in  FIG. 32B  indicates that ΔTs, which is a temperature difference between both ends of a device, cannot be reduced unless heat resistance of package  236  is extremely smaller than air resistance outside the package. Consequently, when heat-insulating material is used for package  236 , problems would occur when the external temperature is non-uniform.  
         [0025]     Therefore, even if soaking plate  232  is used, temperature of the entire LiNbO3 substrate  204  cannot be homogenized. Moreover, temperature gradient is found on the surface of SAW guide  211  and stress is applied non-uniformly due to temperature gradient. Therefore, generation of crystal strain caused by acousto-optical effects cannot be prevented strictly, and filter characteristics degrade. In addition, this further causes a detrimental effect when multi-channeling is attempted, and subsequently, the total length and breadth of LiNbO3 substrate  204  and SAW guide  211  increase.  
         [0026]     In (2), it is possible to make the attenuation coefficient of SAW 1.3 dB/cm and suppress side lobes satisfactorily by carrying out annealing treatment for a specified time. However, this is an insufficient configuration from the viewpoint of achieving a uniform temperature distribution, and characteristic problems as described above remain unsolved.  
         [0027]     The conventional example according to (3) intends to adjust the filter wavelength characteristics by changing the shape and arrangement of a strain providing section after manufacturing an element with the strain providing section for correcting local double refraction index of an optical waveguide. However, from the viewpoint of providing uniform temperature and achieving strain correction, it requires extra cost and impairs simplicity from the viewpoint of manufacture. Furthermore, it is extremely difficult to correct the difference in refraction index appropriately, in order to obtain completely satisfactory filter characteristics.  
         [0028]     In the conventional examples described in (1) through (4), various techniques are described for improving characteristics as a device unit, but these methods do not consider any measures against heat when they are modularized. Particularly, these methods do not take into account generation of temperature gradient, and cannot solve the problem in the case of achieving multi-channeling in which a plurality of AOTF are positioned on one LiNbO3 substrate. As described in (4), it is well known that the filter characteristics of AOTF degrade when temperature distribution is present on the surface of the SAW guide. This is because when stress is applied non-uniformly due to temperature distributions, crystal strain due to acousto-optic effects becomes non-uniform and the filter characteristics degrade. Consequently, it becomes difficult to make the temperature in the SAW guide uniform. Furthermore, when multi-channeling is achieved, not only length but also width of the AOTF device increases, and it becomes still more difficult to achieve uniform temperature on the device surface.  
         [0029]     The conventional examples described in (5) and (6) describe a soaking structure in a waveguide device. In these examples, a soaking plate made of a metal with excellent thermal conductivity is inserted between AWG waveguide device and temperature control device (heater, Peltier device). In the case of an AOTF device different from AWG, since the device area is large, there is a temperature gradient of the heater itself and temperature gradient due to heat resistance difference of air on the AOTF device surface. Therefore, the desired temperature uniformity cannot be achieved by this kind of soaking plate alone. That is, with such construction, a heat soaking plate is placed only on the Peltier device and though the temperature is made homogeneous, outside effects are not considered. In addition, if the heat soaking plate that provides good thermal conductivity is provided, consumption power increases.  
         [0030]     In the optical add/drop modules that use an AWG device, described in (6), lengths of adjoining waveguides in the channel waveguides vary slightly and slab waveguide are formed on an optical substrate such as silicon, quartz, sapphire, etc. (see “ FIG. 1 ” of Japanese Patent Application Laid-Open Publication No. 2000-249853). In this kind of waveguide type device, temperature distribution deviates the light path from the designed value due to temperature dependency of refraction index. In addition, in this waveguide type device, as the number of channels increases, the device area expands; and a construction that does not generate temperature distribution becomes indispensable.  
         [0031]     Thus, the device area in AOTF devices is large. Therefore, problems such as temperature gradient of the heater and temperature gradient caused by difference in heat resistance on the device surface, etc. occur. Therefore, in AOTF devices, the use of the heat soaking plate alone cannot achieve the temperature uniformity in the device. On the other hand, in AWG devices, because the device area increases with the number of channels, temperature uniformity cannot be achieved in the device.  
       SUMMARY OF THE INVENTION  
       [0032]     It is an object of the invention to at least solve the problems in the conventional technology.  
         [0033]     An optical device module according to an aspect of the present invention includes an optical device; a soaking unit fixed to one surface of the optical device; a heating/cooling unit fixed to one surface of the soaking unit, wherein the heating/cooling unit performs a function selected from a group consisting of heating the optical device using self-generated heat and cooling the optical device by absorbing heat; a heat-insulating unit fixed to one surface of the heating/cooling unit; and a package that houses the optical device, the soaking unit, the heating/cooling unit, and the heat-insulating unit. The heat-insulating unit is fixed to one surface of the package.  
         [0034]     The other objects, features, and advantages of the present invention are specifically set forth in or will become apparent from the following detailed description of the invention when read in conjunction with the accompanying drawings. 
     
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0035]      FIG. 1  is a side view of an optical device module according to a first embodiment of the present invention;  
         [0036]      FIG. 2  illustrates results of computer simulation of temperature distribution in an optical device by the optical device module;  
         [0037]      FIG. 3  is a side view of an optical device module according to a second embodiment;  
         [0038]      FIG. 4  is a view of the optical device module as seen from the bottom surface;  
         [0039]      FIG. 5  is a side view of the optical device module, explaining how heating temperature is transmitted;  
         [0040]      FIG. 6  is a side view of an essential portion of an optical device module according to a third embodiment, and an example of temperature characteristics;  
         [0041]      FIG. 7  is a side view of an essential portion of an optical device module according to a third embodiment, and another example of temperature characteristics;  
         [0042]      FIG. 8  illustrates an essential part viewed from the bottom surface of an optical device module according to a fourth embodiment;  
         [0043]      FIG. 9  illustrates an essential portion viewed from the bottom surface of an optical device module according to a fifth embodiment;  
         [0044]      FIG. 10  illustrates an essential portion viewed from the bottom surface of an optical device module according to a sixth embodiment;  
         [0045]      FIG. 11  illustrates an essential portion viewed from the bottom surface of an optical device module according to a seventh embodiment;  
         [0046]      FIG. 12  is a side view of an optical device module according to an eighth embodiment, and an example of temperature characteristics;  
         [0047]      FIG. 13  illustrates an essential part viewed from the bottom surface of an optical device module according to an eighth embodiment;  
         [0048]      FIG. 14  illustrates a variation of the essential part viewed from the bottom surface of the optical device module;  
         [0049]      FIG. 15  illustrates results of computer simulation of temperature distribution in an optical device by the optical device module;  
         [0050]      FIG. 16  is a side view of an essential portion of an optical device module according to a ninth embodiment, and an example of temperature characteristics;  
         [0051]      FIG. 17  illustrates the essential part viewed from the bottom surface of an optical device module;  
         [0052]      FIG. 18  is a side view of an essential portion of an optical device module according to a tenth embodiment, and an example of temperature characteristics;  
         [0053]      FIG. 19  illustrates the essential part viewed from the bottom surface of the optical device module;  
         [0054]      FIG. 20  is a side view of an essential portion of an optical device module according to an eleventh embodiment, and an example of temperature characteristics;  
         [0055]      FIG. 21  illustrates an essential portion viewed from the bottom surface of the optical device module;  
         [0056]      FIG. 22  is a plan view of an essential portion of an optical device module according to a twelfth embodiment;  
         [0057]      FIG. 23  is a perspective view of a construction of a lamination in a package in the optical device module;  
         [0058]      FIG. 24  is a plan view of an essential section of an optical device module according to a thirteenth embodiment;  
         [0059]      FIG. 25A  illustrates an essential section of the optical device module according to a fourteenth embodiment;  
         [0060]      FIG. 25B  is a side view of the optical device module;  
         [0061]      FIG. 26  illustrates an essential section of an optical device module according to a fifteenth embodiment;  
         [0062]      FIG. 27  illustrates a first example of a conventional optical device module;  
         [0063]      FIG. 28  illustrates a second example of a conventional optical device module;  
         [0064]      FIG. 29  illustrates heat resistance of each section in the first conventional optical device module;  
         [0065]      FIG. 30  is a circuit diagram illustrating heat resistance of each section in the first conventional optical device module;  
         [0066]      FIG. 31  illustrates heat resistance of each section in the first conventional optical device module when the package has low thermal conductivity;  
         [0067]      FIG. 32A  is a thermal equivalent circuit diagram illustrating heat resistance of the module shown in  FIG. 31 ; and  
         [0068]      FIG. 32B  illustrates a simplified form of the thermal equivalent circuit. 
     
    
     DETAILED DESCRIPTION  
       [0069]     Exemplary embodiments of an optical device module according to the present invention will be explained in detail with reference to the accompanying drawings.  
         [0070]     Referring to drawings, an optical device module related to embodiments 1 through 15 of the present invention is described in detail. A case in which LiNbO3 waveguide type AOTF  202 , which is a waveguide type optical device shown in  FIG. 27 , is applied is described as an example of the optical device. Thereafter, the detailed description of the AOTF  202  is omitted.  
         [0071]      FIG. 1  is a side view of an optical device module according to a first embodiment of the present invention. A flat-plate form soaking plate (soaking member)  12  of uniform thickness made of material having good heat conductivity such as copper is joined to the bottom surface of AOTF  202  using an adhesive such as epoxy resin. A heater (temperature control section)  14  that has a cubic form, generates heat in accordance with the supply of electric current and is joined to the bottom surface of soaking plate  12  using an adhesive such as epoxy resin. A heat-insulator (heat-insulating means: heat-insulating element)  16  is made of polyphenylene sulfide (PPS), Duracon, or phenol resin, among others and is joined to the bottom surface of heater  14  using an adhesive such as epoxy resin. A top profile of the heat-insulator  16  coincides with the bottom profile of soaking plate  12 . Similarly, the bottom surface of heat-insulator  16  is joined to the inner bottom surface of a package (PKG)  18  using adhesive such as epoxy resin. The table below shows thermal conductivity of these components.  
                                                   Name   Heat conductivity (W/m-° C.)                           PPS   0.26           Duracon   0.30           Phenol resin   0.21                        
         [0072]     By joining the bottom surface of heat insulator  16  to the inside of package  18 , a successively laminating configuration to integrate AOTF  202 , soaking plate  12 , heater  14 , and heat insulator  16 , is housed in package  18 . The package  18  is made of material having good heat conductivity and is formed into an airtight cube (hollow cubic form) shut with lid  20 .  
         [0073]     In place of heater  14 , a Peltier element may be used, and in such case, the top surface of the Peltier element is used for heating and the bottom surface for absorbing heat. In addition, in  FIG. 1 , the area of the top surface and the bottom surface of soaking plate  12 , heater  14 , and heat insulator  16  are smaller than the area of the bottom surface of AOTF  202 , but these may be assumed to be identical.  
         [0074]     In the first embodiment, when heater  14  is heated, the soaking plate  12  and AOTF  202  are heated. The heat insulator  16  prevents transmission of the heat downwards and almost all of the heat is transmitted upwards to soaking plate  12 , thereby efficiently and uniformly heating the soaking plate  12 .  
         [0075]      FIG. 2  illustrates results of computer simulation of temperature distribution in an optical device by the optical device module. An overall temperature distribution of 0.3° C. or lower is obtained.  
         [0076]     An optical device module according to a second embodiment is described below with reference to  FIG. 3  through  FIG. 5 .  FIG. 3  is a side view of an optical device module according to a second embodiment. The configuration of the heat-insulating means is explained in detail. The other components of the optical device module are identical to those in the first embodiment, and the detailed description thereof is omitted.  
         [0077]      FIG. 4  is a view of the optical device module as seen from the bottom surface. As shown in  FIG. 3  and  FIG. 4 , the heat insulating means includes a plurality of heat-insulating elements in the form of square bars that are made of polyphenylene sulfide, Duracon, or phenol resin. The heat-insulating elements have varying heat-insulation ratio (thermal conductivity) and are spaced at predetermined intervals, perpendicular to the direction of propagation of incoming lights λ 1  through μn. One surface of the heat-insulating elements is attached to the bottom surface of heater  14  and the other surface to the inner bottom surface of package  18 . The length of each of the square-bars of the heat insulator  22  is slightly longer than the breadth of the AOTF  202 . Consequently, it becomes easy to position the heat insulator  22  on the heater  14  or the heater  14  on a plurality of heat insulators  22 . Spatial regions  24  are present between the squared bars of the heat insulator  22 . The air inside the package  18 , which fills the spatial regions  24  serves as an additional heat-insulating element. It is well known that the heat-insulation ratio of air is higher than that of the heat insulator  22 .  
         [0078]     With this configuration, when heater  14  is heated, the temperature of the portion of the heater  14  heat-insulated by air inside each spatial region  24  increases, making the temperature of the corresponding portions of soaking plate  12  relatively higher.  
         [0079]      FIG. 5  is a side view of the optical device module, explaining how heating temperature is transmitted. As shown with arrow marks in the figure, the portion of the soaking plate  12  corresponding to the portion where heat insulator  22  exists, reaches a temperature level “a”. The portion of the soaking plate  12  corresponding to the portion of spatial region  24  reaches the temperature of level “b”, which is higher than level “a”. On the surface of AOTF  202 , a plurality of arc-shaped regions of temperature level “c” is formed, each centered around the temperature level b. As time passes, the entire surface of the AOTF  202  is assumed to reach a uniform temperature level “d”. In other words, the same results as shown in  FIG. 2  can be obtained.  
         [0080]     According to the second embodiment, spatial regions  24  of air insulation are interleaved between heat insulators  22 . Therefore, the heating temperature of the whole of heater  14  can be transmitted efficiently to soaking plate  12 , thereby saving energy and at the same time, reducing the volume of the material used for the heat insulators. Consequently, keeping the surface temperature of the AOTF  202  uniform further reduces cost. Moreover, the AOTF  202  exhibits satisfactory filter characteristics, and it becomes easy to promote multi-channeling and increase the functionality.  
         [0081]     An optical device module according to a third embodiment 3 is described next, with reference to  FIG. 6  and  FIG. 7 .  FIG. 6  is a side view of essential portion of the optical device module according to the third embodiment, together with temperature characteristics.  FIG. 7  is a side view of the essential portion, and another example of temperature characteristics. In the case of embodiment 3, the configuration of the heat insulating means is explained in detail. The other components of the optical device module are identical to those in the first and second embodiments, and the detailed description thereof is omitted.  
         [0082]     In the third embodiment, the heat insulating means is formed by a plurality of square bars (heat insulating elements)  42  identical in shape, made of polyphenylene sulfide, Duracon, or phenol resin, etc., and attached to the bottom surface of heater  14 . A plurality of spatial regions  44  providing air heat insulation are formed between the square bars. The heat insulators  42  are placed in a direction perpendicular to the direction of propagation of the incoming light. However, unlike in the second embodiment, the space between the plurality of heat insulators  42  is not identical, the spatial regions  44  are coarse or densely spaced. Moreover, each of the heat insulators  42  is joined to the inner bottom surface of package  18  by adhesive such as epoxy resin, etc.  
         [0083]     Sometimes, the temperature of the center of heater  14  is likely to be lower than that of the other regions, as seen from temperature characteristics of heat-generating resistors in heater  14  (concave temperature distribution due to non-uniformity of the heater: see pattern A in  FIG. 6 ). The region where the intervals between the heat insulators  42  are coarse corresponds to the center region of heater  14 , and the region where the intervals between the heat insulators  42  are dense corresponds to the regions on both ends of the heater  14 . When the heater  14  is heated, the total heat insulation provided by the coarse regions of heat insulator  42  is large. Therefore, the temperature of the coarse regions is comparatively high (convex temperature distribution due to heat insulator: see pattern B in  FIG. 6 ) and mutually compensates for the concave temperature distribution of heater  14 , thereby homogenizing the temperature distribution of the AOTF  202  (see pattern C in  FIG. 6 ).  
         [0084]     On the other hand, sometimes, the temperature of the center of heater  14  is likely to be higher than that of the other regions, as seen from temperature characteristics of heat-generating resistors in heater  14  (convex temperature distribution due to non-uniformity of the heater: see pattern A in  FIG. 7 ). The region where the intervals between the heat insulators  42  are coarse corresponds to the region on both ends of heater  14 , and the region where the intervals between the heat insulators  42  are dense corresponds to the center region of heater  14 . When heater  14  is heated, the total heat insulation provided by the coarse region of heat insulator  42  is large. Therefore, the temperature of the coarse region is comparatively high (concave temperature distribution due to heat insulator: see pattern B in  FIG. 7 ) and mutually compensates for the convex temperature distribution of heater  14 , thereby homogenizing the temperature distribution of the AOTF  202  (see pattern C in  FIG. 7 ).  
         [0085]     Thus, according to the third embodiment, the coarse and dense regions between the heat insulators  42  are configured based on the temperature distribution characteristics of the heater  14 . Therefore, the temperature distribution of the soaking plate  12  can be homogenized appropriately, and the entire region of AOTF  202  can be uniformly heated. Moreover, merely by adjusting the intervals between the heat insulators  42  to be either coarse or dense, it is possible to keep the surface temperature of AOTF uniform. Consequently, cost is reduced, satisfactory filter characteristics of AOTF are exhibited and maintained, and at the same time, multi-channeling can be promoted and functionality increases. Furthermore, because the heat insulators  42  have spatial regions  44  for communication with the inside of package  18 , air inside each spatial region  44  can be evacuated. Consequently, air inside each of the spatial regions  44  does not expand and excellent heat insulating effects are achieved.  
         [0086]     The technique of adjusting the intervals of insulators  42  into coarse regions and dense regions can be applied to embodiment 1 and embodiment 2 described above.  
         [0087]     An optical device module according to a fourth embodiment is described next, with reference to  FIG. 8 .  FIG. 8  illustrates an essential portion viewed from the bottom surface of the optical device module according to a fourth embodiment. The configuration of the heat-insulating means is explained in detail. The other components of the optical device module are identical to those in the first embodiment, and the detailed description thereof is omitted.  
         [0088]     As shown in  FIG. 8 , the heat insulating means includes heat-insulating elements  52  with identical cross sections and made of polyphenylene sulfide, Duracon, or phenol resin, etc. The heat-insulating elements  52  are meandrous and form spatial regions  54  for air heat insulation. The spatial regions  54  are spaced at predetermined intervals perpendicular to the direction of propagation of incoming light. Thus, the heat insulators  52  cut across the bottom surface of heater  14 , are connected on alternate ends, and are integrated into one piece. The meandering heat insulators  52  are joined to the bottom surface of heater  14  and to the inner bottom surface of package  18  (see  FIG. 1 ) by adhesive such as epoxy resin.  
         [0089]     Thus, in the fourth embodiment, the use of meandering heat insulators  52  simplifies production and positioning of the heater  14  and heat insulators  52 . Consequently, fabrication is simplified. Moreover, the temperature distribution of soaking plate  12  can be homogenized appropriately, and the entire region of the AOTF  202  can be uniformly heated. Furthermore, satisfactory filter characteristics of AOTF are exhibited and maintained, and at the same time, multi-channeling can be promoted and functionality increases. Because heat insulators  52  have spatial regions  54  to communicate with the inside of package  18 , air inside each spatial region  54  can be evacuated. Consequently, the air inside each of spatial regions  54  does not expand and excellent heat insulating effects are achieved.  
         [0090]     The intervals between meandering heat insulators  52 , that is the spatial regions  54  for air heat insulation may be configured to have coarse regions and dense regions based on the heating characteristics of heater  14 .  
         [0091]     An optical device module according to a fifth embodiment is described next, with reference to  FIG. 9 .  FIG. 9  illustrates an essential portion viewed from the bottom surface of the optical device module according to the fifth embodiment. The configuration of the heat insulating means is explained in detail. The other components of the optical device module are identical to those in the first embodiment, and the detailed description thereof is omitted.  
         [0092]     As shown in  FIG. 9 , the heat insulating means includes a plurality of heat-insulating elements  62  with identical cross sections and made of polyphenylene sulfide, Duracon, or phenol resin, etc. The heat-insulating elements  62  are provided in a form of comb teeth while forming spatial regions  64  for air heat insulation. The spatial regions  64  are spaced at predetermined intervals perpendicular to the direction of propagation of incoming light. Consequently, the heat insulators  62  cut across the bottom surface of heater  14 , are connected to heat insulator  66  on one end, and are integrated into one piece. The comb-teeth shaped heat insulators  62  are joined to the bottom surface of heater  14  and to the inner bottom surface of package  18  (see  FIG. 1 ) by adhesive such as epoxy resin.  
         [0093]     Thus, in the fifth embodiment, the use of comb-teeth shaped heat insulators  62  simplifies production and positioning of the heater  14  and heat insulators  62 . Consequently, fabrication is simplified. Moreover, the temperature distribution of soaking plate  12  can be homogenized appropriately, and the entire region of the AOTF  202  can be heated uniformly. Furthermore, satisfactory filter characteristics of AOTF are exhibited and maintained, and at the same time, multi-channeling can be promoted and functionality increases. Because comb-teeth shaped heat insulators  62  have spatial regions  64  to communicate with the inside of package  18 , air inside the spatial region  64  can be evacuated, and consequently, air inside each of spatial regions  64  does not expand and excellent heat insulating effects are achieved.  
         [0094]     The intervals between comb-teeth shaped heat insulators  62 , that is the spatial regions  64  for air heat insulation may be configured to have coarse regions and dense regions based on the heating characteristics of heater  14 .  
         [0095]     An optical device module according to a sixth embodiment is described next, with reference to  FIG. 10 .  FIG. 10  illustrates an essential portion viewed from the bottom surface of the optical device module according to the sixth embodiment. The configuration of the heat insulating means is explained in detail. The other components of the optical device module are identical to those in the first embodiment, and the detailed description thereof is omitted.  
         [0096]     As shown in  FIG. 10 , the heat insulating means is formed by one pair of heat insulators, each including a plurality of heat-insulating elements  72 ,  74  with identical cross sections and made of polyphenylene sulfide, Duracon, or phenol resin, etc. The heat-insulating elements  72 ,  74  are provided in a form of comb teeth while forming spatial regions  76 ,  78  for air heat insulation. The spatial regions  76 ,  78  are spaced at predetermined intervals perpendicular to the direction of propagation of incoming light. The comb-teeth shaped insulators  72  are interleaved with the comb-teeth-form insulators  74  so that the plurality of elements of one insulator is placed in the spatial regions of the other insulator. The two comb-teeth-form insulators  72 ,  74  are joined to the bottom surface of heater  14  and to the inner bottom surface of package  18  (see  FIG. 1 ) by adhesive such as epoxy resin, etc.  
         [0097]     Thus, in the sixth embodiment, the use of comb-teeth shaped heat insulators  72 ,  74 , which are interleaved, simplifies production and positioning of the heater  14  and the two comb-teeth shaped heat insulators  72 ,  74 . Consequently, fabrication is simplified. Moreover, the temperature distribution of soaking plate  12  can be homogenized appropriately, and the entire region of the AOTF  202  can be heated uniformly. Furthermore, satisfactory filter characteristics of AOTF are exhibited and maintained, and at the same time, multi-channeling can be promoted and functionality increases. Furthermore, because comb-teeth shaped heat insulators  72 ,  74  have spatial regions  76 ,  78  for communication with the inside of package  18 , air inside the spatial regions  76 ,  78  can be evacuated. Consequently, the air inside each of spatial regions  76 ,  78  does not expand and excellent heat insulating effects are achieved.  
         [0098]     The intervals between comb-teeth shaped heat insulators 72 ,  74 , that is, the spatial regions  76 ,  78  for air heat insulation may be configured to have coarse regions and dense regions based on the heating characteristics of heater  14 .  
         [0099]     An optical device module according to a seventh embodiment is described next, with reference to  FIG. 11 .  FIG. 11  illustrates an essential portion viewed from the bottom surface of the optical device module according to the seventh embodiment. The configuration of the heat insulating means is explained in detail. The other components of the optical device module are identical to those in the first embodiment, and the detailed description thereof is omitted.  
         [0100]     As shown in  FIG. 11 , the heat insulating means is formed by a plurality of plate-form heat-insulating elements  84 , is made of polyphenylene sulfide, Duracon, or phenol resin, etc. and placed perpendicular to the direction of propagation of incoming light. A plurality of spatial regions  82  may be formed by injection and hollowing, (the forming method is optional) for air insulation. The spatial regions  82  are spaced at predetermined intervals perpendicular to the direction of propagation of incoming light. An air vent  86  that enables ventilation of each of spatial regions  82  is formed on one end of each heat insulating plate. Each of these heat insulators  84  is joined to the bottom surface of heater  14  and to the inner bottom surface of package  18  (see  FIG. 1 ) by adhesive such as epoxy resin, etc.  
         [0101]     Thus, in the seventh embodiment, the use of heat-insulator plate  84  simplifies production and positioning of the heater  14  and heat insulators  84 . Consequently, fabrication is simplified. Moreover, the temperature distribution of soaking plate  12  can be homogenized appropriately, and the entire region of the AOTF  202  can be heated uniformly. Furthermore, satisfactory filter characteristics of AOTF are exhibited and maintained, and at the same time, multi-channeling can be promoted and functionality increases. Furthermore, because heat insulator  84  has air vent  86  at one end of each of spatial regions  82  for communication with the inside of package  18 , air inside each of spatial regions  82  can be evacuated. Consequently, air inside spatial regions  82  does not expand and excellent heat insulating effects are achieved.  
         [0102]     The intervals between the spatial regions  82  may be configured to have coarse regions and dense regions based on the heating characteristics of heater  14 .  
         [0103]     An optical device module according to an eighth embodiment is described next, with reference to  FIG. 12  through  FIG. 15 .  FIG. 12  is a side view an essential portion of the optical device module of the eighth embodiment together with temperature characteristics.  FIG. 13  and FIG.  14  are views as seen from the bottom surface. The configuration of the heat insulating means is explained in detail. The other components of the optical device module are identical to those in the first embodiment, and the detailed description thereof is omitted.  
         [0104]     As shown in  FIG. 13 , the heat insulating means made of polyphenylene sulfide, Duracon, or phenol resin, etc., is in the form of letter X and is a flat-plate heat insulating element  94  having recessed sections  92 ,  92  for air heat insulation (heat insulating element). Both ends are depressed in the concave shape in order to deal with the case in which the center of heater  14  tends to acquire comparatively high temperature due to patterns of heat-generating resistors inside heater  14  (convex temperature distribution due to non-uniformity of the heater: see pattern A in  FIG. 12 ). The X-shaped heat insulator  94  is joined to the bottom surface of heater  14  and to the inner bottom surface of package  18  by adhesive such as epoxy resin, etc.  
         [0105]     When heater  14  is heated, the heat insulation ratio is comparatively low at the center of X-shaped heat insulator  94  and high in the region of recessed sections  92  on both ends because of air heat insulation (concave temperature distribution due to heat-insulating section: see pattern B in  FIG. 12 ). Consequently, the convex temperature distribution of heater  14  is mutually compensated for, and a uniform temperature distribution of AOTF  202  is achieved (see pattern C in  FIG. 12 ).  
         [0106]     Thus, according to the eighth embodiment, the use of previously prepared X-shaped flat-plate heat-insulator  94  simplifies production and positioning of the heater  14  and heat insulators  94 . Consequently, fabrication is simplified. Moreover, the X-shaped heat insulator  94  can adapt to the characteristics of heater  14  and homogenize the temperature distribution of soaking plate  12 , thereby making it possible to heat the entire area of AOTF  202  to a uniform temperature. Consequently, satisfactory filter characteristics of AOTF  202  are exhibited and maintained, and at the same time, multi-channeling can be promoted and functionality increases. Furthermore, because heat insulator  94  has the spatial regions surrounded by recessed sections  92  for communication with the inside of package  18 , air inside the spatial regions surrounded by recessed section  92  can be evacuated. Consequently, air inside the spatial regions surrounded by recessed section  92  does not expand and excellent heat insulating effects are achieved.  
         [0107]     Moreover, even if the size of recessed sections  92 ,  92  of the X-shaped heat insulator  94  is less than the breadth of soaking plate  12  (or heater  14 ) as shown in  FIG. 14 , it is possible to homogenize the temperature distribution of AOTF  202 .  
         [0108]      FIG. 15  illustrates results of computer simulation of temperature distribution in an optical device by the optical device module according to the eighth embodiment. The use of X-shaped heat insulator  94  achieves temperature uniformity within 0.1° C. throughout the full width.  
         [0109]     An optical device module according to a ninth embodiment is described next, referring to  FIG. 16  and  FIG. 17 .  FIG. 16  illustrates an essential portion of the optical device module of the ninth embodiment together with temperature characteristics.  FIG. 16  is a side view, and  FIG. 17  is a view as seen from the bottom surface. The configuration of the heat insulating means is explained in detail. The other components of the optical device module are identical to those in the first embodiment, and the detailed description thereof is omitted.  
         [0110]     The heat insulating means is made of polyphenylene sulfide, Duracon, or phenol resin, etc., and is in the form of a flat-plate heat insulating element  104 . An opening formed at the center serves as the spatial region  102  for air heat insulation. The spatial region  102  is shaped in order to deal with the case in which the center of heater  14  tends to acquire comparatively low temperature due to patterns of heat-generating resistors inside heater  14  (concave temperature distribution due to non-uniformity of the heater: see pattern A in  FIG. 16 ). Part of spatial region  102  is spatially connected to air vent  106  formed in part of flat-plate heat insulator  104 . The flat-plate heat insulator  104  is joined to the bottom surface of heater  14  and to the inner bottom surface of package  18  by adhesive such as epoxy resin, etc.  
         [0111]     When heater  14  is heated, the heat insulation ratio is high at the center of flat-plate heat insulator  104 , that is, in the spatial region  102  (convex temperature distribution due to heat-insulating section: see pattern B in  FIG. 16 ). Consequently, this mutually compensates for the concave temperature distribution of heater  14 , and a uniform temperature distribution of AOTF  202  is achieved (see pattern C in  FIG. 16 ).  
         [0112]     Thus, according to the ninth embodiment, using a flat-plate heat-insulator  104  having spatial region  102  in the center simplifies production and positioning of the heater  14  and heat insulators  104 . Consequently, fabrication is simplified. Moreover, the heat insulator  104  that has spatial region  102  in the center can adapt to the characteristics of heater  14  and homogenize the temperature distribution of soaking plate  12 , thereby making it possible to heat the entire area of AOTF  202  to a uniform temperature. Consequently, satisfactory filter characteristics of AOTF  202  are exhibited and maintained, and at the same time, multi-channeling can be promoted and functionality increases. Furthermore, because heat insulator  104  has an air vent  106  included in the spatial regions  102  for communication with the inside of package  18 , air inside spatial regions  102  can be evacuated. Consequently, air inside each of spatial regions  102  does not expand and excellent heat insulating effects are achieved.  
         [0113]     Moreover, in the flat-plate-form heat insulator  1 . 04 , an additional air vent  106  may be formed at a position opposite to air vent  106 , and the number of air vents formed may be set optionally.  
         [0114]     An optical device module according to a tenth embodiment is described next, referring to  FIG. 18  and  FIG. 19 .  FIG. 18  illustrates an essential portion of the optical device module of the tenth embodiment together with temperature characteristics.  FIG. 18  is a side view, and  FIG. 19  is a view as seen from the bottom surface. The configuration of the heat insulating means is explained in detail. The other components of the optical device module are identical to those in the first embodiment, and the detailed description thereof is omitted.  
         [0115]     The heat insulating means is made of polyphenylene sulfide, Duracon, or phenol resin, etc., and is in the form of a flat-plate heat insulator (heat insulating element)  118 . An opening formed at the center serves as the spatial region  112  for air heat insulation (heat-insulating element). Recessed spatial regions  114 ,  116  for air heat insulation (heat insulating element) in the form of concave shape are provided on the forward edge side and backward edge side to deal with the case in which the center of heater  14  tends to acquire comparatively high temperature due to patterns of heat-generating resistors inside heater  14  (convex temperature distribution due to non-uniformity of the heater: see pattern A in  FIG. 18 ). Part of spatial region  112  in the center opening is spatially connected to air vent  119  formed in part of flat-plate heat insulator  118 . The flat-plate heat insulator  118  is joined to the bottom surface of heater  14  and to the inner bottom surface of package  18  by adhesive such as epoxy resin, etc.  
         [0116]     When heater  14  is heated, the heat insulation ratio is low in the regions of flat-plate heat insulator  118  other than spatial regions  112 ,  114 ,  116  (concave temperature distribution due to heat insulation section: see pattern B in  FIG. 18 ). Consequently, this mutually compensates for the convex temperature distribution of heater  14 , and a uniform temperature distribution of AOTF  202  is achieved (see pattern C in  FIG. 18 ).  
         [0117]     Thus, according to the tenth embodiment, using a flat-plate heat-insulator  118  having spatial regions  112 ,  114 ,  116  on the center side and on both edges simplifies production and positioning of the heater  14  and heat insulators  118 . Consequently, fabrication is simplified. Moreover, the heat insulator  118  that has spatial regions  112 ,  114 ,  116  on the center side and on both edges can adapt to the characteristics of heater  14  and homogenize the temperature distribution of soaking plate  12 , thereby making it possible to heat the entire area of AOTF  202  to a uniform temperature. Consequently, satisfactory filter characteristics of AOTF  202  are exhibited and maintained, and at the same time, multi-channeling can be promoted and functionality increases. Furthermore, because heat insulator  118  has an air vent  119  included in the spatial region  112  for communication with the inside of package  18  while other spatial regions  114 ,  116  directly communicate with the inside of package  18 , air inside spatial regions  112 ,  114 ,  116  can be evacuated. Consequently, air inside spatial regions  112 ,  114 ,  116  does not expand and excellent heat insulating effects are achieved.  
         [0118]     Moreover, in the flat-plate-form heat insulator  118 , an additional air vent  119  may be formed at a position opposite to air vent  119 , and the number of air vents formed may be set optionally.  
         [0119]     An optical device module according to an eleventh embodiment is described next, referring to  FIG. 20  and  FIG. 21 .  FIG. 20  illustrates an essential portion of the optical device module of the eleventh embodiment, together with temperature characteristics.  FIG. 20  is a side view, and  FIG. 21  is a view as seen from the bottom surface. The configuration of the heat insulating means is explained in detail. The other components of the optical device module are identical to those in the first embodiment, and the detailed description thereof is omitted.  
         [0120]     The heat insulating means is made of polyphenylene sulfide, Duracon, or phenol resin, etc., and is configured as flat-plate heat insulator (heat insulating element)  128 . Openings formed on two sides of the center of the heat insulator  128 , serve as the spatial regions  122 ,  124  for air heat insulation (heat-insulating element). An air vent  126  spatially connected to both spatial regions  122 ,  124  on one end are provided to deal with the case in which the center side of heater  14  tends to acquire comparatively low temperature on both sides of the center of heater  14  due to patterns of heat-generating resistors inside heater  14  (concave temperature distribution due to non-uniformity of the heater: see pattern A in  FIG. 20 ). The flat-plate heat insulator  128  is joined to the bottom surface of heater  14  and to the inner bottom surface of package  18  by adhesive such as epoxy resin, etc.  
         [0121]     When heater  14  is heated, the heat insulation ratio is high in both spatial regions  122 ,  124  of flat-plate heat insulator  128  (convex temperature distribution due to heat insulation section: see pattern B in  FIG. 20 ). Consequently, this mutually compensates for the concave temperature distribution of heater  14  and a uniform temperature distribution of AOTF  202  is achieved (see pattern C in  FIG. 20 ).  
         [0122]     Thus, according to the eleventh embodiment, flat-plate heat-insulator  128  that has spatial regions  122 ,  124 , on both sides of the center simplifies production and positioning of the heater  14  and heat insulators  128 . Consequently, fabrication is simplified. Moreover, the heat insulator  128  that has spatial regions  122 ,  124  on both sides of the center can adapt to the characteristics of heater  14  and homogenize the temperature distribution of soaking plate  12 , thereby making it possible to heat the entire area of AOTF  202  to a uniform temperature. Consequently, satisfactory filter characteristics of AOTF  202  are exhibited and maintained, and at the same time, multi-channeling can be promoted and functionality increases. Furthermore, because spatial regions  122 ,  124  of heat insulator  128  communicate with the inside of package  18  via air vent  126 , air inside spatial regions  122 ,  124  can be evacuated. Consequently, air inside spatial regions  122 ,  124  does not expand and excellent heat insulating effects are achieved.  
         [0123]     An optical device module related to a twelfth embodiment is described next, referring to  FIG. 22  and  FIG. 23 .  FIG. 22  is a plan view of an essential section of the optical device module according to the twelfth embodiment. The AOTF  202  includes four channels corresponding to four waveguides (ch 1 , ch 2 , ch 3 , ch 4 ). The AOTF  202  is illustrated by a dashed line in the figure. The waveguide of each channel is formed by connecting two AOTF  202  in series. This embodiment 12 is similar to those above described with the exception that the configuration of heat insulating means differs, and consequently, detailed description of other configurations is omitted. The number of channels of AOTF  202  can be set optionally.  
         [0124]     The heat insulating means is made of polyphenylene sulfide, Duracon, or phenol resin, etc., and is configured as flat-plate heat insulator (heat-insulating element)  136  with H-shaped spatial regions  132 A,  132 B,  132 C,  132 D in the shape of lattices, formed at four places, for air heat insulation (heat insulating element). Air vents  132   a ,  132   b ,  132   c ,  132   d  spatially connected to each of spatial regions  132 A,  132 B,  132 C,  132 D to deal with the case in which four positions in the lattice form of heater  14  tend to acquire low temperature in the H-shaped regions due to patterns of heat-generating resistors in heater  14 . The flat-plate heat insulator  136  is joined to the bottom surface of heater  14  and to the inner bottom surface of package  18  by adhesive such as epoxy resin, etc.  
         [0125]      FIG. 23  is a perspective view of construction of a lamination in a package in an optical device module according to the twelfth embodiment. The heat insulator  136  is joined to the inner bottom surface of package  18  (see  FIG. 1 ), while heater  14  is joined to the heat insulator  136 . The soaking plate  12  is joined on the top surface of heater  14 , and on the top surface of soaking plate  12 , AOTF  202  having four channels, that is, four waveguides (ch 1 , ch 2 , ch 3 , ch 4 ), is joined with LiNbO3 substrate.  
         [0126]     Referring now to  FIG. 22  and  FIG. 23 , the arrangement of each spatial region  132 A,  132 B,  132 C,  132 D of heat insulator  136  and four waveguides (ch 1 , ch 2 , ch 3 , ch 4 ) of AOTF  202  is described below. Four regions  132 Aa,  132 Ab,  132 Ba,  132 Bb of H-shaped spatial regions  132 A,  132 B form an inverted concave shape, and are located below waveguide ch 1 . Four regions  132 Ac,  132 Ad,  132 Bc,  132 Bd of H-shaped spatial regions  132 A,  132 B form a concave shape, and are located below waveguide ch 2 . Four regions  132 Ca,  132 Cb,  132 Da,  132 Db of H-shaped spatial regions  132 C,  132 D form an inverted concave shape, and are located below waveguide ch 3 . Four regions  132 Cc,  132 Cd,  132 Dc,  132 Dd of H-shaped spatial regions  132 C,  132 D form a concave shape, and are located below waveguide ch 4 .  
         [0127]     When heater  14  is heated, the portions of H-shaped spatial regions  132 A,  132 B,  132 C,  132 C mutually compensate for non-uniform temperature distribution of heater  14  more finely because of air heat insulation, and can keep the temperature distribution of AOTF  202  uniform.  
         [0128]     Thus, according to the twelfth embodiment, flat-plate heat-insulator  136  having H-shaped spatial regions  132 A,  132 B,  132 C,  132 D formed at four places in the shape of lattices simplifies production and positioning of the heater  14  and heat insulators  136 . Consequently, fabrication is simplified. Moreover, the heat insulator  136  having H-shaped spatial regions  132 A,  132 B,  132 C,  132 D can adapt to more complicated temperature characteristics of heater  14  or positional relationship of 4-channel configuration including four waveguides (ch 1 , ch 2 , ch 3 , ch 4 ). Thus, it is possible to heat the entire area of AOTF  202  to a uniform temperature. Consequently, satisfactory filter characteristics of AOTF  202  are exhibited and maintained, and at the same time, multi-channeling can be promoted and functionality increases.  
         [0129]     Furthermore, because each of H-shaped spatial regions  132 A,  132 B,  132 C,  132 D communicate with the inside of package  18  via air vents  132   a ,  132   b ,  132   c ,  132   d , air inside each of spatial regions  132 A,  132 B,  132 C,  132 D can be evacuated. Consequently, air inside each of spatial regions  132 A,  132 B,  132 C, and  132 D does not expand and excellent heat insulating effects are achieved.  
         [0130]     Optionally, a plurality of air vents may be formed in flat-plate-shape heat insulator  136 , in addition to one air vent per spatial region, to communicate with each of the spatial regions.  
         [0131]     An optical device module according to a thirteenth embodiment is described next, referring to  FIG. 24 .  FIG. 24  is a plan view of an essential section of the optical device module according to the thirteenth embodiment. AOTF  202  includes four channels corresponding to four waveguides (ch 1 , ch 2 , ch 3 , ch 4 ). The construction of the lamination inside package  18  in this embodiment is similar to that described in the twelfth embodiment (see  FIG. 23 ) with the exception that the construction of heat insulating means differs. The number of channels of AOTF  202  can be set optionally.  
         [0132]     The heat insulating means is made of polyphenylene sulfide, Duracon, or phenol resin, etc., and is configured as flat-plate heat insulator (heat-insulating element)  148  with H-shaped spatial regions  142 A,  142 B,  142 C,  142 D in the shape of lattices, formed at four places, for air heat insulation (heat insulating element). Spatial regions  142 A,  142 B,  142 C,  142 D are spatially connected to each other, such that the spatial connections form another spatial region  144  at the center of heat insulator  148 . Thus, one spatial region  146  is formed as a whole (see  FIG. 24 ). An air vent  147  spatially connected to part of the spatial region  146  are provided, to deal with the case in which four positions in the lattice form of heater  14  tend to acquire low temperature in the H-shaped regions due to patterns of heat-generating resistors in heater  14 . The flat-plate heat insulator  148  is joined to the bottom surface of heater  14  and to the inner bottom surface of package  18  by adhesive such as epoxy resin, etc.  
         [0133]     Next, the arrangement of each spatial regions  142 A,  142 B,  142 C,  142 D of heat insulator  148  and four waveguides ch 1 , ch 2 , ch 3 , ch 4  of AOTF  202  is described. As shown in  FIG. 24 , four regions  142 Aa,  142 Ab,  142 Ba,  142 Bb of the spatial regions  142 A,  142 B and form an inverted concave shape, and are located below waveguide ch 1 . Four regions  142 Ac,  142 Ad,  142 Bc,  142 Bd of the spatial regions  142 A,  142 B form a concave shape, and are located below waveguide ch 2 . Four regions  142 Ca,  142 Cb,  142 Da,  142 Db of the spatial regions  142 C,  142 D form an inverted concave shape, and are located below waveguide ch 3 . Four regions  142 Cc,  142 Cd,  142 Dc,  142 Dd of the spatial regions  142 C,  142 D form an inverted concave shape, and are located below waveguide ch 4 .  
         [0134]     When heater  14  is heated, the entire spatial region  146  containing H-shaped spatial regions  142 A,  142 B,  142 C,  142 D formed in flat-plate-form heat insulator  148  mutually compensate for non-uniform temperature distribution of heater  14  more finely because of air heat insulation, and can keep the temperature distribution of AOTF  202  more uniform.  
         [0135]     Thus, according to the thirteenth embodiment, flat-plate heat-insulator  148  having one spatial region  146  containing H-shaped spatial regions  142 A,  142 B,  142 C,  142 D formed at four places in the shape of lattices simplifies production and positioning of the heater  14  and heat insulators  148 . Consequently, fabrication is simplified. Moreover, the heat insulator  148  can adapt to more complicated temperature characteristics of heater  14  and homogenize the temperature distribution of soaking plate  12 . Thus, it is possible to heat the entire area of AOTF  202  to a uniform temperature. Consequently, satisfactory filter characteristics of AOTF  202  are exhibited and maintained, and at the same time, multi-channeling can be promoted and functionality increases.  
         [0136]     Furthermore, because each of spatial regions  142 A,  142 B,  142 C,  142 D communicate with the inside of package  18  via air vent  147 , air inside each of spatial regions  142 A,  142 B,  142 C,  142 D can be evacuated. Consequently, air inside each of spatial regions  142 A,  142 B,  142 C, and  142 D does not expand and excellent heat insulating effects are achieved.  
         [0137]     Optionally, a plurality of air vents  147  may be formed in the spatial region  146  of flat-plate-shape heat insulator  148 .  
         [0138]     An optical device module according to a fourteenth embodiment is described next, referring to  FIG. 25A  and  FIG. 25B .  FIG. 25A  illustrates an essential section of the optical device module according to a fourteenth embodiment. An AOTF  202  includes four channels corresponding to four waveguides (ch 1 , ch 2 , ch 3 , ch 4 ). The construction of the lamination inside package  18  in this embodiment is similar to that described in the twelfth embodiment (see  FIG. 23 ) with the exception that the construction of heat insulating means differs. The number of channels of AOTF  202  can be set optionally.  
         [0139]     As shown in the plan view of  FIG. 25A , the heat insulating means is made of polyphenylene sulfide, Duracon, or phenol resin, etc., and is configured as flat-plate heat insulator (heat-insulating element)  156  with square-shaped spatial regions  152 A,  152 B, . . . ,  152   n  formed at a plurality of places in the shape of lattices, for air heat insulation (heat insulating element). Each of the longitudinal air-vents  154  are spatially connected to the spatial regions of one column. For example, spatial regions  152 A,  152 E,  1521 ,  152 M are connected by one longitudinal air-vent. The air-vents are provided in order to deal with the case in which a plurality of regions corresponding to the spatial regions tend to acquire low temperature due to patterns of heat-generating resistors in heater  14 , or the case in which it is desired to heat regions where a plurality of waveguides (ch 1 , ch 2 , ch 3 , ch 4 ) of AOTF  202  are located.  
         [0140]     Next, the arrangement of each column of spatial regions  152 A,  152 E,  1521 ,  152 M, etc. of heat insulator  156  and four waveguides ch 1 , ch 2 , ch 3 , ch 4  of AOTF  202  is described. As shown in  FIG. 25A , spatial regions  152 A, etc. aligned in a single horizontal line are located below waveguide ch 1 . Spatial regions  152 E, etc. aligned in the next horizontal line are located below waveguide ch 2 . Spatial regions  1521 , etc. aligned in the next horizontal line are located below waveguide ch 3 . Spatial regions  152 M, etc. aligned in the next horizontal line are located below waveguide ch 4 .  
         [0141]     As shown in the side view in  FIG. 25B , heat insulator  156  is joined to the inner bottom surface of package  18 , heater  14  to the top surface of heat insulator  156 , soaking plate (soaking member)  12  to the top surface of heater  14 , and AOTF  202  is joined to the top surface of soaking plate  12 . This arrangement is the same in the case of this embodiment 14 as well as in the embodiments 1 through 13.  
         [0142]     When heater  14  is heated, each of lattice-form spatial regions  152 A, etc. formed in flat-plate-form heat insulator  156  mutually compensate for non-uniform temperature distribution of heater  14  more finely because of air heat insulation, and can keep the temperature distribution of AOTF  202  uniform. Optical signals free of optical loss can be outputted from each waveguide (ch 1 , ch 2 , ch 3 , ch 4 ). Moreover, as shown in  FIG. 25B , since the size of soaking plate  12  and heater  14  (area of the top surface), both, is set greater than that of the AOTF  202 , it is possible to maintain the temperature distribution of AOTF  202  uniform.  
         [0143]     Thus, according to the fourteenth embodiment, flat-plate heat-insulator  156  containing a plurality of spatial regions  152 A, etc. configured in a lattice-form, simplifies production and positioning of the heater  14  and heat insulators  156 . Consequently, fabrication is simplified. Moreover, the heat insulator  128  containing spatial regions  152 A, etc. arranged in a lattice form at a plurality of places can adapt to more complicated temperature characteristics of heater  14  and can homogenize the temperature distribution of soaking plate  12 , thereby making it possible to heat the entire area of AOTF  202  to a uniform temperature. Consequently, satisfactory filter characteristics of AOTF  202  are exhibited and maintained, and at the same time, multi-channeling can be promoted and functionality increases.  
         [0144]     Furthermore, because each of spatial regions  152 A, etc. communicates with the inside of package  18  via air vent  154 , air inside each of spatial regions  152 A, etc. can be evacuated. Consequently, air inside each of spatial regions  152 A, etc. does not expanded and excellent heat insulating effects are achieved.  
         [0145]     Optionally, for each of spatial regions of flat-plate-shape heat insulator  156 , a plurality of longitudinal air vents  154  may be formed in addition to air vents  154 .  
         [0146]     An optical device module according to a fifteenth embodiment is described next, referring to  FIG. 26 .  FIG. 26  illustrates an essential section of the optical device module according to the fifteenth embodiment. An AOTF  202  includes four channels corresponding to four waveguides (ch 1 , ch 2 , ch 3 , ch 4 ). The construction of the lamination inside package  18  in this embodiment is similar to that described in the twelfth embodiment (see  FIG. 23 ) with the exception that the construction of heat insulating means differs. The number of channels of AOTF  202  can be set optionally.  
         [0147]     The heat insulating means is made of polyphenylene sulfide, Duracon, or phenol resin, etc., and is configured as flat-plate heat insulator (heat-insulating element)  166  with spatial regions  162 A,  162 B, . . . ,  162   n  formed at a plurality of places in the shape of lattices in a zigzag manner for air heat insulation (heat insulating element). Spatial regions  162 A,  162 E,  1621 ,  162 M, etc. are aligned in a longitudinal zigzag line respect to each of spatial region  162 A,  162 B,  162 C,  162 D, and air vent  164  spatially connecting each zigzag longitudinal line is provided, to deal with the case in which a plurality of regions in the lattice form of heater  14  tend to acquire low temperature due to patterns of heat-generating resistors in heater  14  or the case in which it is desired to heat regions where the waveguides of AOTF  202  are located.  
         [0148]     Next, the arrangement of each spatial region  162 A,  162 E,  1621 ,  162 M, etc. of heat insulator  166  and four waveguides ch 1 , ch 2 , ch 3 , ch 4 , of AOTF- 202  is described. As shown in the plan view in  FIG. 26 , spatial regions  162 A, etc. aligned in a single horizontal line are located below waveguide ch 1 . Spatial regions  162 E, etc. aligned in the next horizontal line are located below waveguide ch 2 . Spatial regions  1621 , etc. aligned in the next horizontal line are located below waveguide ch 3 . Spatial regions  162 M, etc. aligned in the next horizontal line are located below waveguide ch 4 .  
         [0149]     When heater  14  is heated, each of zigzag lattice-form spatial regions  162 A, etc., formed in flat-plate-form heat insulator  166  mutually compensate for non-uniform temperature distribution of heater  14  more finely because of air heat insulation, and can keep the temperature distribution of AOTF  202  uniform. Thus, optical signals free of optical loss can be outputted.  
         [0150]     Thus, according to the fifteenth embodiment, flat-plate heat-insulator  166  containing a plurality of spatial regions  162 A, etc. forming a zigzag lattice-form simplifies production and positioning of the heater  14  and heat insulators  166 . Consequently, fabrication is simplified. Moreover, the heat insulator  166  containing spatial regions  162 A, etc. arranged in a lattice form at a plurality of places can adapt to more complicated temperature characteristics of heater  14  and can homogenize the temperature distribution of soaking plate  12 , thereby making it possible to heat the whole area of AOTF  202  to a uniform temperature. Furthermore, it is possible to heat the whole area including waveguide (ch 1 , ch 2 , ch 3 , ch 4 ) portions of AOTF  202  to a uniform temperature. Consequently, satisfactory filter characteristics of AOTF are exhibited and maintained, and at the same time, multi-channeling can be promoted and functionality increases.  
         [0151]     Moreover, because each of spatial regions  162 A, etc. communicate with the inside of package  18  via air vent  164 , air inside each of spatial regions  162 A, etc. can be evacuated. Consequently, air inside each of spatial regions  162 A, etc. does not expand and excellent heat insulating effects are achieved.  
         [0152]     Optionally, for each of spatial regions  162 A of flat-plate-shape heat insulator  166 , a plurality of longitudinal air vents  164  may be formed in addition to air vents  164 .  
         [0153]     In each of embodiments described above, each of spatial region  24 , etc. is filled with air hermetically sealed in package  18  to achieve air heat insulation. However, heat insulation may be achieved by evacuating the package  18  (creating vacuum), or by filling nitrogen or dry nitrogen in each of spatial region  24 .  
         [0154]     In addition, it is needless to say that the present invention can be applied to an optical waveguide grating (AWG) which uses an optical add/drop module array.  
         [0155]     According to the optical device module of the present invention, it is possible to homogenize the overall device temperature without being susceptible to the temperature gradient of the outside, and to manufacture easily at low cost without increasing heater power consumption required for soaking, and promote multi-channeling requirements. Particularly, when the present invention is applied to waveguide type optical devices, the uniform temperature distribution can be maintained and the number of channels can be increased easily with an extremely simple configuration.  
         [0156]     Although the invention has been described with respect to a specific embodiment for a complete and clear disclosure, the appended claims are not to be thus limited but are to be construed as embodying all modifications and alternative constructions that may occur to one skilled in the art which fairly fall within the basic teaching herein set forth.