The present invention relates to an arrayed waveguide grating used as a wavelength division multiplexer/demultiplexer in optical communications, and method for correcting center wavelength.
In recent optical communications, wavelength division multiplexing communications are vigorously researched and developed and its practical use is advanced as a method for greatly increasing transmission capacity of the optical communications. In the wavelength division multiplexing communications, for example, a plurality of lights having wavelengths different from each other are multiplexed and transmitted. In such wavelength division multiplexing communications, a light transmitting device which transmits only the predetermined wavelengths is indispensable.
FIG. 11 shows one example of the light transmitting device. This light transmitting device is an arrayed waveguide grating (AWG) of a planar lightwave circuit (PLC). The arrayed waveguide grating includes a waveguide forming area having a waveguide construction formed on a silicon substrate 1 as shown in FIG. 11.
The waveguide construction of the arrayed waveguide grating comprises at least one optical input waveguide 2 and a first slab waveguide 3 connected to an emitting side of at least one optical input waveguide 2. An arrayed waveguide 4 constructed by a plurality of channel waveguides 4a arranged side by side is connected to an emitting side of the first slab waveguide 3. A second slab waveguide 5 is connected to an emitting side of the arrayed waveguide 4. A plurality of optical output waveguides 6 arranged side by side are connected to an emitting side of the second slab waveguide 5.
The above arrayed waveguide 4 propagates light transmitted from the first slab waveguide 3. Lengths of the adjacent channel waveguides 4a are different by xcex94L from each other. For example, the optical output waveguides 6 are arranged in accordance with the number of signal lights of wavelengths different from each other. A plurality of channel waveguides 4a such as 100 channel waveguides 4a are normally arranged. However, in FIG. 11, the number of optical output waveguides 6, the number of channel waveguides 4a and the number of optical input waveguides 2 are respectively schematically shown to simplify FIG. 11.
For example, an unillustrated optical fiber is connected to the optical input waveguide 2 so as to introduce the wavelength multiplexed light. The wavelength multiplexed light is transmitted to the first slab waveguide 3 through one of the optical input waveguides 2. The wavelength multiplexed light transmitted to the first slab waveguide 3 is widened by a diffraction effect, and is transmitted to the arrayed waveguide 4, and is propagated in the arrayed waveguide 4.
The light propagated in the arrayed waveguide 4 reaches the second slab waveguide 5, and the lights are condensed each other and outputted to each of optical output waveguide 6. However, since the lengths of the adjacent channel waveguides 4a of the arrayed waveguide 4 are different from each other, a phase shift is caused for the individual light after the light is propagated in the arrayed waveguide 4. A phasefront of the condensed light is inclined in accordance with this shift amount, and a condensing position is determined by an angle of this inclination.
Therefore, the condensing positions of the lights of different wavelengths are different from each other. The lights (demultiplexed lights) of different wavelengths can be outputted from the different optical output waveguides 6 every wavelength by forming the optical output waveguides 6 in the respective light condensing positions.
Namely, the arrayed waveguide grating has an optical demultiplexing function for demultiplexing from the multiplexed light, having wavelengths different from each other. A center wavelength of the demultiplexed light is proportional to the difference (xcex94L) between the lengths of the adjacent channel waveguides 4a of the arrayed waveguide 4 and an effective refractive index (equivalent refractive index) n of the arrayed waveguide 4.
The arrayed waveguide grating satisfies the relation of (formula 1).
nsxc2x7dxc2x7sin xcfx86+ncxc2x7xcex94L=mxc2x7xcexxe2x80x83xe2x80x83(formula 1)
Here, ns is an equivalent refractive index of each of the first slab waveguide and the second slab waveguide, and nc is an equivalent refractive index of the arrayed waveguide. Further, xcfx86 is a diffraction angle, m is a diffraction order, d is the distance between the adjacent channel waveguides 4a at the end of the arrayed waveguide 4, and xcex is a center wavelength of light outputted from each optical output waveguide.
Here, when the center wavelength at the diffraction angle xcfx86=0 is set to xcex0, xcex0 is represented by (formula 2). The wavelength xcex0 is generally called a center wavelength of the arrayed waveguide grating.                               λ          0                =                                                            n                c                            ·              Δ                        ⁢                          xe2x80x83                        ⁢            L                    m                                    (                  Formula          ⁢                      xe2x80x83                    ⁢          2                )            
Since the arrayed waveguide grating has the above characteristics, the arrayed waveguide grating can be used as a wavelength multiplexer/demultiplexer for the wavelength multiplexing transmission.
For example, as shown in FIG. 11, when a multiplexed light of wavelengths xcex1, xcex2, xcex3, - - - , xcexn (n is an integer not less than 2) is inputted from one of the optical input waveguides 2, the light having the different wavelengths is widened in the first slab waveguide 3 and reach the arrayed waveguide 4. Thereafter, the lights of the respective wavelengths are condensed to different positions in accordance with the wavelengths as mentioned above through the second slab waveguide 5. The lights of the respective wavelengths are transmitted to the optical output waveguides 6 different from each other, and are outputted from emitting ends of the optical output waveguides 6 through the respective optical output waveguides 6.
The above light of each wavelength is taken out through an unillustrated optical fiber for an optical output by connecting this optical fiber to the emitting end of each optical output waveguide 6. When the optical fiber is connected to each optical output waveguide 6 and the above optical input waveguide 2, for example, an optical fiber array fixedly arranging a connecting end face of the optical fiber in a one-dimensional array shape is prepared. The optical fiber arrays are fixed to connecting end face sides of the optical output waveguides 6 and the optical input waveguides 2, and then the optical fibers, the optical output waveguides 6 and the optical input waveguides 2 are connected.
In the above arrayed waveguide grating, transmittion characteristics of the light outputted from each optical output waveguide 6, i.e., the wavelength dependency of transmitted light intensity of the arrayed waveguide grating are provided as shown in FIG. 12A. As shown in FIG. 12A, in the light transmitting characteristics of the light outputted from each optical output waveguide 6, each center wavelength (for example, xcex1, xcex2, xcex3, - - - , xcexn) is set to a center and light transmittance is reduced as the wavelength is shifted from each corresponding center wavelength. FIG. 13 is a view overlapping and showing an example of an output spectrum from each optical output waveguide 6.
It is not necessarily limited that the above light transmitting characteristics have one local maximum value as shown in FIG. 12A. For example, as shown in FIG. 12B, there is also a case in which the light transmitting characteristics have not less than two local maximum values.
Further, since the arrayed waveguide grating utilizes the principle of reciprocity (reversibility) of light, the arrayed waveguide grating has the function of an optical demultiplexer, and also has the function of an optical multiplexer. For example, in contrast to FIG. 11, the optical multiplexing is performed by making lights of a plurality of wavelengths different from each other inputted from the respective optical output waveguides 6 of the arrayed waveguide grating every wavelength. The light transmitted from each optical output waveguide 6 passes through a propagating path reverse to the above propagating path and is multiplexed through the second slab waveguide 5, the arrayed waveguide 4 and the first slab waveguide 3, and is emitted from one of the optical input waveguides 2.
The waveguide forming area of the above arrayed waveguide grating is originally mainly formed by a silica-based glass material. Therefore, the above center wavelength of the arrayed waveguide grating is shifted dependently on temperature by temperature dependence of the silica-based glass material. When a temperature changing amount of the arrayed waveguide grating is set to T, this temperature dependence is represented by (formula 3) by differentiating the above (formula 2) by this temperature changing amount T.                                           ⅆ            λ                                ⅆ            T                          =                                            λ                              n                c                                      ·                                          ∂                                  n                  c                                                            ∂                T                                              +                                    λ              L                        ·                                          ∂                L                                            ∂                T                                                                        (                  Formula          ⁢                      xe2x80x83                    ⁢          3                )            
In the (formula 3), the first term on the right-hand side shows the temperature dependence of an effective refractive index of the arrayed waveguide 4, and the second term on the right-hand side shows a change in length of the arrayed waveguide 4 caused by expansion and contraction of the substrate.
FIG. 14 is a view typically showing the temperature dependence of this center wavelength by measuring results of the light transmitting characteristics outputted from some one of the optical output waveguides 6. As shown in FIG. 14, the center wavelength is shifted on a long wavelength side as the temperature of the arrayed waveguide grating rises. Conversely, the center wavelength is shifted on a short wavelength side as the temperature of the arrayed waveguide grating is reduced.
When the temperature rises, the refractive index of glass forming the waveguide is increased so that the first term on the right-hand side of (formula 3) is increased. Further, when the temperature rises, the length of the arrayed waveguide 4 is physically lengthened by thermal expansion of the substrate 1 and the waveguide material. Namely, the second term on the right-hand side of (formula 3) is increased. Accordingly, when the temperature rises, the length of a sensing optical path of the light passing through the arrayed waveguide 4 is lengthened so that the above center wavelength shift is caused.
FIG. 14 shows the temperature change in the transmitting characteristics of the light outputted from some one of the optical output waveguides 6, but the transmitting characteristics of the light outputted from all the optical output waveguides 6 show similar shift characteristics in the arrayed waveguide grating. Namely, in the light outputted from all the optical output waveguides 6, the center wavelength is shifted by the same shifting amount in the same shifting direction dependently on temperature.
In the conventional arrayed waveguide grating, dnc/dT=1xc3x9710xe2x88x925 (xc2x0 C.xe2x88x921) and nc=1.451 at a wavelength of 1.55 xcexcm are set. Further, there are many cases in which the arrayed waveguide grating is used at present to demultiplex and multiplex. Therefore, the temperature dependence of the above center wavelength of the conventional arrayed waveguide grating is calculated in the wavelength band with the wavelength 1550 nm as a center. Thus, a value of the temperature dependence of the center wavelength is set to about 0.01 nm/xc2x0 C.
Accordingly, for example, when the temperature of the arrayed waveguide grating is changed by 50xc2x0 C., the center wavelength outputted from each optical output waveguide 6 is shifted by 0.5 nm. When the temperature of the arrayed waveguide grating is changed by 70xc2x0 C., the shifting amount of the above center wavelength is 0.7 nm.
In recent years, a demultiplexing or multiplexing wavelength interval calculated in the arrayed waveguide grating ranges from 0.4 nm to 1.6 nm and is very narrowed. Accordingly, as mentioned above, it cannot be neglected that the center wavelength is changed by the above shifting amount by the temperature change.
Therefore, an arrayed waveguide grating having a temperature adjusting means for constantly holding the temperature of the arrayed waveguide grating so as not to change the center wavelength by the temperature is conventionally proposed. For example, this temperature adjusting means is constructed by arranging a Peltier device, a heater, etc. These temperature adjusting means perform control for holding the arrayed waveguide grating to a set temperature determined in advance.
FIG. 15 shows a construction in which a Peltier device 26 is arranged on a side of the substrate 1 of the arrayed waveguide grating. In the arrayed waveguide grating shown in FIG. 15, the temperature of the arrayed waveguide grating is adjusted so as to be constantly held on the basis of a detecting temperature of a thermistor 40. In FIG. 15, reference numerals 41 and 12 respectively designate a lead wire and a soaking plate.
In a construction in which a heater is arranged instead of the Peltier device, the temperature of the arrayed waveguide grating is held to a high temperature by the heater and is constantly held.
In the construction for arranging the above temperature adjusting means, it is possible to restrain expansion and contraction of the substrate 1, a change in equivalent refractive index of the above core, etc. caused by temperature by constantly holding the temperature of the arrayed waveguide grating. Therefore, the problem of the temperature dependence of the above center wavelength can be dissolved in the construction for arranging the temperature adjusting means.
However, a controller, a thermistor for control, a thermocouple, etc. are naturally required to constantly hold the temperature of the arrayed waveguide grating by using the temperature adjusting means such as a Peltier device and a heater. In the arrayed waveguide grating constructed by arranging the temperature adjusting means, there was a case in which no center wavelength shift could be accurately restrained by an assembly shift of parts of the temperature adjusting means, etc.
Further, in the arrayed waveguide grating, precision is very required at a manufacturing of the arrayed waveguide grating. Therefore, the conventional arrayed waveguide grating also has the problem that the center wavelength is shifted from a design wavelength by an error (manufacture dispersion, etc.). Accordingly, the development of a cheap arrayed waveguide grating able to correct both the shift of the center wavelength from the design wavelength and the temperature dependence had been required.
The arrayed waveguide grating of a first construction of the present invention comprises;
a waveguide construction has at least optical input waveguide, a first slab waveguide connected to an emitting side of at least one optical input waveguide, an arrayed waveguide connected to an emitting side of the first slab waveguide and constructed by a plurality of channel waveguides having lengths different from each other by set amounts and arranged side by side, a second slab waveguide connected to an emitting side of the arrayed waveguide, and a plurality of optical output waveguides arranged side by side and connected to an emitting side of the second slab waveguide;
the waveguide construction is formed on a substrate;
separating slab waveguides are formed by separating at least one of said first slab waveguide and the second slab waveguide on a crossing face crossing a path of light passing through the slab waveguide;
a slide moving member for reducing the temperature dependence of a center wavelength of the arrayed waveguide grating by sliding and moving at least one side of the separated separating slab waveguides along said separating face dependently on temperature is arranged;
and a length of the slide moving member is set to a length for correcting a shift of the center wavelength of the arrayed waveguide grating from a set wavelength by plastic deformation of said slide moving direction.
The arrayed waveguide grating of a second construction of the present invention comprises;
the above slide moving member is plastically deformed by applying compression stress to the slide moving member in addition to the above first construction.
The arrayed waveguide grating of a third construction of the present invention is comprises;
the above slide moving member is plastically deformed by applying tensile stress to the slide moving member in addition to the above first construction.
The arrayed waveguide grating of a fourth construction of the present invention comprises;
a waveguide construction is formed on a substrate such that a first slab waveguide is connected to an emitting side of at least one optical input waveguide, and an arrayed waveguide constructed by a plurality of channel waveguides for propagating light transmitted from the first slab waveguide and having lengths different from each other by set amounts and arranged side by side is connected to an emitting side of the first slab waveguide, and a second slab waveguide is connected to an emitting side of the arrayed waveguide, and a plurality of optical output waveguides arranged side by side are connected to an emitting side of the second slab waveguide;
separating slab waveguides are formed by separating at least one of said first slab waveguide and the second slab waveguide on a crossing face crossing a path of light passing through the slab waveguide;
a slide moving member for reducing the temperature dependence of a center wavelength of the arrayed waveguide grating by sliding and moving at least one side of the separated separating slab waveguides along said separating face dependently on temperature is arranged;
a hollow or a hole is formed in a displacing area of the slide moving member in its sliding direction;
and a length of said slide moving member is set to a length for correcting a shift of the center wavelength of the arrayed waveguide grating from a set wavelength by fitting a fitting member having a large diameter portion having a diameter larger than that of an opening of the hollow or the hole into said hollow or the hole.
The arrayed waveguide grating of a fifth construction of the present invention comprises;
the above fitting member is set to a taper screw reduced in diameter toward its tip side in addition to the above fourth construction.
The arrayed waveguide grating of a sixth construction of the present invention comprises;
the above slide moving member is formed by a metal in addition to one of the above first to fifth constructions.
A method for correcting center wavelength of the arrayed waveguide grating of a seventh construction of the present invention comprises;
a waveguide construction has at least one optical input waveguide, a first slab waveguide connected to an emitting side of at least one optical input waveguide, an arrayed waveguide connected to an emitting side of the first slab waveguide and constructed by a plurality of channel waveguides having lengths different from each other by set amounts and arranged side by side, a second slab waveguide connected to an emitting side of the arrayed waveguide, and a plurality of optical output waveguides arranged side by side and connected to an emitting side of the second slab waveguide;
the waveguide construction is formed on a substrate; a separating slab waveguide is formed by separating at least one of said first slab waveguide an d the second slab waveguide on a crossing face crossing a path of light passing through the slab waveguide;
a slide moving member for reducing the temperature dependence of a center wavelength of the arrayed waveguide grating by sliding and moving at least one side of said separated separating slab waveguide along said separating face dependently on temperature is arranged in the arrayed waveguide a grating;
and the center wavelength of the arrayed waveguide grating is set to a set wavelength by moving at least one side of said separating slab waveguide along said separating face by plastically deforming the slide moving member.
The method for correcting a center wavelength of the arrayed waveguide grating of an eighth construction of the present invention comprises;
the above slide moving member is plastically deformed by applying compression stress to the above slide moving member in addition to the above seventh construction.
The method for correcting a center wavelength of the arrayed waveguide grating of a ninth construction of the present invention comprises;
the above slide moving member is plastically deformed by applying tensile stress to the above slide moving member in addition to the above seventh construction.
The method for correcting a center wavelength of the arrayed waveguide grating of a tenth construction of the present invention comprises;
a waveguide construction has at least one optical input waveguide, a first slab waveguide connected to an emitting side of the optical input waveguide, an arrayed waveguide connected to an emitting side of the first slab waveguide and constructed by a plurality of channel waveguides having lengths different from each other by set amounts and arranged side by side, a second slab waveguide connected to an emitting side of the arrayed waveguide, and a plurality of optical output waveguides arranged side by side and connected to an emitting side of the second slab waveguide;
the waveguide construction is formed on a substrate;
a separating slab waveguide is formed by separating at least one of said first slab waveguide and the second slab waveguide on a crossing face crossing a path of light passing through the slab waveguide;
a slide moving member for reducing the temperature dependence of a center wavelength of the arrayed waveguide grating by sliding and moving at least one side of said separated separating slab waveguide along said separating face dependently on temperature is arranged in the arrayed waveguide grating;
a hollow or a hole is formed in a displacing area of the slide moving member in its sliding direction;
and a length of said slide moving member in said sliding direction is changed and at least one side of said separating slab waveguide is moved along said separating face by fitting a fitting member having a large diameter portion having a diameter larger than that of an opening of the hollow or the hole into said hollow or the hole so that the center wavelength of the arrayed waveguide grating is set to a set wavelength.
The method for correcting a center wavelength of the arrayed waveguide grating of an eleventh construction of the present invention comprises;
while the center wavelength of the above arrayed waveguide grating is monitored, a movement along the separating face of the separating slab waveguide is made by the slide moving member so as to set the monitored center wavelength to the set wavelength in addition to one of the above seventh to tenth constructions.
The present inventors noticed linear dispersion characteristics of the arrayed waveguide grating to restrain the temperature dependence of the arrayed waveguide grating.
As mentioned above, in the arrayed waveguide grating, the center wavelength xcex0 at a diffraction angle xcfx86=0 is represented by the formula (2). A condensed position of the arrayed waveguide grating providing this diffraction angle xcfx86=0 is set to a point O in FIG. 10. In this case, for example, the condensed position (a position at an output end of the second slab waveguide) of light providing a diffraction angle xcfx86=xcfx86p becomes the position of a point P shifted from the point O in the X-direction. Here, when the distance between the points O and P in the X-direction is set to x, the following (formula 4) is formed between the distance x and the wavelength xcex.                                           ⅆ            x                                ⅆ            λ                          =                                                                              L                  f                                ·                Δ                            ⁢                              xe2x80x83                            ⁢              L                                                      n                s                            ·              d              ·                              λ                0                                              ⁢                      n            g                                              (                  Formula          ⁢                      xe2x80x83                    ⁢          4                )            
In the (formula 4), Lf is a focal length of the second slab waveguide, and ng is a group refractive index of the arrayed waveguide. The group refractive index ng of the arrayed waveguide is provided by the following (formula 5) using an equivalent refractive index nc of the arrayed waveguide.                               n          g                =                              n            c                    -                                    λ              0                        ⁢                                          ⅆ                                  ·                                      n                    c                                                                              ⅆ                λ                                                                        (                  Formula          ⁢                      xe2x80x83                    ⁢          5                )            
The above (formula 4) means that light different by dxcex in wavelength can be taken out by arranging and forming an input end of the optical output waveguide is arranged and formed in a position separated by the distance dx in the X-direction from the focal point O of the second slab waveguide.
The relation of the (formula 4) is similarly formed with respect to the first slab waveguide 3. For example, a focal center of the first slab waveguide 3 is set to a point Oxe2x80x2, and a point located in a position shifted by a distance dxxe2x80x2 in the X-direction from this point Oxe2x80x2 is set to a point Pxe2x80x2. In this case, when light is transmitted to this point Pxe2x80x2, an output wavelength is shifted by dxcexxe2x80x2. This relation is represented by the following (formula 6).                                           ⅆ                          x              xe2x80x2                                            ⅆ                          λ              xe2x80x2                                      =                                                                              L                  f                  xe2x80x2                                ·                Δ                            ⁢                              xe2x80x83                            ⁢              L                                                      n                s                            ·              d              ·                              λ                0                                              ⁢                      n            g                                              (                  Formula          ⁢                      xe2x80x83                    ⁢          6                )            
In the (formula 6), Lfxe2x80x2 is a focal length of the first slab waveguide. This (formula 6) means that light different by dxcexxe2x80x2 in wavelength in the optical output waveguide formed at the above focal point O can be taken out by arranging and forming an output end of the optical input waveguide in a position separated by the distance dxxe2x80x2 in the X-direction from the focal point Oxe2x80x2 of the first slab waveguide.
Accordingly, when the center wavelength outputted from the optical output waveguide of the arrayed waveguide grating is shifted by xcex94xcex by the temperature change, the shift of the center wavelength is corrected by shifting the output end position of the optical input waveguide by the distance dxxe2x80x2 in the above X-direction so as to set dxcexxe2x80x2=xcex94xcex. For example, light having no wavelength shift can be taken out by this shifting operation in the optical output waveguide formed at the focal point O. Further, since the above action is similarly caused with respect to the other optical output waveguides, the above shift xcex94xcex of the center wavelength can be corrected (dissolved).
In the present invention of the above construction, at least one of the first slab waveguide and the second slab waveguide is separated on a face crossing the path of light passing through the slab waveguide. Here, an argument will be made by assuming that the first slab waveguide is separated. For example, a separating slab waveguide side (including the optical input waveguide) connected to the optical input waveguide among this separated first slab waveguide is slid and moved along the above separating face by the slide moving member. Thus, the above each center wavelength can be shifted by this sliding movement.
Further, the separating slab waveguide and the optical input waveguide are moved by the above slide moving member along the above separating face in a direction for reducing the temperature dependence change of the above each center wavelength such that the temperature dependence change (wavelength shift) xcex94xcex of the above each center wavelength is equal to dxcex. Thus, the above center wavelength shift depending on temperature can be dissolved.
strictly speaking, the focal length Lfxe2x80x2 of light propagated within the first slab waveguide is slightly changed from the output end of the optical input waveguide to an input end of the arrayed waveguide by changing the position of the output end of the optical input waveguide. However, the focal length of the first slab waveguide in the arrayed waveguide grating used at present is of the order of several mm. In contrast to this, a moving amount of the output end position of the optical input waveguide moved to correct the center wavelength of the arrayed waveguide grating is of the order from several xcexcm to several ten xcexcm. Namely, the moving amount of the output end position of the above optical input waveguide is very small in comparison with the focal length of the first slab waveguide.
Therefore, it is substantially considered that the change in the above focal length can be neglected. Thus, as mentioned above, the center wavelength shift depending on temperature can be dissolved if the separating slab waveguide and the optical input waveguide are moved along the above separating face in the direction for reducing the temperature dependence change of each center wavelength in the arrayed waveguide grating.
Here, the relation of a temperature changing amount and a position correcting amount of the optical input waveguide will be derived in advance. Since the temperature dependence (the shifting amount of the center wavelength due to temperature) of the above center wavelength is represented by the above (formula 3), the shifting amount xcex94xcex of the center wavelength can be represented by the following (formula 7) using the temperature changing amount T.                     Δλ        =                                            ⅆ              λ                                      ⅆ              T                                ⁢          T                                    (                  Formula          ⁢                      xe2x80x83                    ⁢          7                )            
When the temperature changing amount T and the position correcting amount dxxe2x80x2 of the optical input waveguide are calculated from (formula 6) and (formula 7), the following (formula 8) is derived.                               dx          xe2x80x2                =                                                                              L                  f                  xe2x80x2                                ·                Δ                            ⁢                              xe2x80x83                            ⁢              L                                                      n                s                            ·              d              ·                              λ                0                                              ⁢                      n            g                    ⁢                                    ⅆ              λ                                      ⅆ              T                                ⁢          T                                    (                  Formula          ⁢                      xe2x80x83                    ⁢          8                )            
In the present invention, the separating slab waveguide of the first slab waveguide and the optical input waveguide are slid and moved by the above slide moving member along the above separating face dependently on temperature by the position correcting amount dxxe2x80x2 shown by (formula 8). The above center wavelength shift depending on temperature can be dissolved by this sliding movement.
When the center wavelength of the arrayed waveguide grating is shifted from the set wavelength such as a grid wavelength, etc., it is also important to correct this shift. In the arrayed waveguide grating of the present invention, as mentioned above, if a separating slab waveguide side connected to the optical input waveguide is slid and moved along the above separating face, the above each center wavelength can be shifted. Therefore, in the present invention, the separating slab waveguide is slid and moved along the above separating face by changing the length of the slide moving member in the above slide moving direction by plastic deformation of the slide moving member, etc. Therefore, in the present invention, the center wavelength of the arrayed waveguide grating can be shifted to the set wavelength.
For example, the above slide moving member is plastically deformed by applying compression stress and tensile stress to the slide moving member. Further, the length of the slide moving member in the slide moving direction can be also changed by fitting a fitting member into a hollow or a hole formed in the slide moving member.
The center wavelength of the arrayed waveguide grating can be approximately set to the set wavelength by setting the length of the slide moving member to a length for correcting the shift of the center wavelength of the arrayed waveguide grating from the set wavelength.
In the present invention, as mentioned above, the slide moving member slides and moves the separating slab waveguide dependently on temperature. Accordingly, for example, if the temperature dependence of the center wavelength of the arrayed waveguide grating is reduced by this sliding movement, it is possible to construct an excellent arrayed waveguide grating in which the center wavelength approximately becomes the set wavelength at any temperature within a using temperature range.
As mentioned above, the arrayed waveguide grating is formed by utilizing reciprocity of light. Therefore, similar effects are also obtained when the slide moving member for separating a second slab waveguide side and sliding and moving at least one side of the separated separating slab waveguides in the direction for reducing the temperature dependence change of the above each center wavelength along the above separating face is arranged. In the arrayed waveguide grating of this construction, the center wavelength can be set to the set wavelength at any temperature within the using temperature range.