JP2003240987A - Optical waveguide module - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an optical waveguide module in which the temperature of an optical waveguide chip is stably adjusted with small power consumption. <P>SOLUTION: The optical waveguide module is provided with the optical waveguide chip 9 having an optical waveguide circuit for which light transmission characteristics are changed at least by the temperature, such as an array waveguide diffraction grating, a temperature detecting element 30 which detects the temperature of the optical waveguide chip 9, and a temperature adjusting module 8 which adjusts the temperature of the optical waveguide chip 9 on the basis of the detection temperature of the temperature detecting element 30. The temperature adjusting module 8 and the optical waveguide chip 9 are piled up and directly joined. The temperature detecting element 30 is provided on a position to detect the temperature at the position away from the optical waveguide circuit center position C1 of the optical waveguide chip 9, and by the light transmission center wavelength deviation of the optical waveguide chip 9 based on a difference between the detection temperature and the temperature at the center position C1, the light transmission center wavelength deviation of the optical waveguide chip based on the warp of the temperature adjusting module 8 is reduced. <P>COPYRIGHT: (C)2003,JPO

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an optical waveguide module used for optical communication and the like.

[0002]

BACKGROUND ART In recent years, in optical communication, as a method of dramatically increasing the transmission capacity thereof, high-density wavelength-division multiplex transmission (D-WDM) has been actively researched and developed, and is being put into practical use. In this high-density wavelength-division multiplex transmission, for example, a plurality of lights having different wavelengths are wavelength-multiplexed and transmitted, and the transmission capacity of one optical fiber is efficiently increased by increasing the number of wavelength multiplexing. It is possible. Recently, wavelength division multiplexing communication systems using 100 or more wavelengths have been commercialized.

An optical wavelength multiplexer / demultiplexer is one of the optical components that play an important role in this wavelength division multiplexing communication. The optical wavelength multiplexer / demultiplexer is a generic term for the optical wavelength multiplexer / demultiplexer,
Many optical wavelength multiplexers and optical wavelength demultiplexers also have the other function.

Array waveguide diffraction gratings (AWGs) have been put to practical use as optical wavelength multiplexers / demultiplexers.
d Waveguide Grating). As shown in FIG. 4, the arrayed-waveguide diffraction grating is formed by forming a waveguide formation region 10 on a substrate 1 formed of quartz glass, silicon, or the like. An optical waveguide circuit is formed.

In this specification, a structure in which an optical waveguide circuit is formed on a substrate is called an optical waveguide chip,
Among the optical waveguide chips, the structure in which the optical waveguide circuit of the arrayed waveguide diffraction grating is formed on the substrate is called an arrayed waveguide diffraction grating chip.

The optical waveguide circuit of the arrayed waveguide diffraction grating is
At least one optical input waveguide 2 and the optical input waveguide 2
A first slab waveguide 3 connected to the output side of the
Array waveguide 4 connected to the output side of the slab waveguide 3 of
A second slab waveguide 5 connected to the output side of the arrayed waveguide 4 and a plurality of optical output waveguides 6 connected in parallel to the output side of the second slab waveguide 5 is doing.

The arrayed waveguide 4 propagates the light derived from the first slab waveguide 3, and is formed by arranging a plurality of channel waveguides 4a in parallel, and the adjacent channel waveguides 4a are formed. The lengths of 4a are set by each other (ΔL)
Is different. In the arrayed waveguide diffraction grating, the formation region of the arrayed waveguide 4 serves as the phase portion. The waveguide forming region 10 having the above optical waveguide circuit is formed of a silica glass material.

The optical output waveguides 6 are provided so as to correspond to the number of signal lights of different wavelengths which are demultiplexed or combined by the arrayed waveguide diffraction grating, and constitute the arrayed waveguide 4. Channel waveguide 4a
Are usually provided in a large number such as 100, but in the figure, for simplification of the figure, the number of each of the channel waveguides 4a, the optical output waveguides 6 and the optical input waveguides 2 is provided. Is simply shown.

An optical fiber (not shown) on the transmission side, for example, is connected to the optical input waveguide 2 so that wavelength-multiplexed light can be introduced. The light introduced into the first slab waveguide 3 is spread by the diffraction effect, enters the array waveguide 4, and propagates in the array waveguide 4.

The light propagated through the arrayed waveguide 4 is
Of the array waveguide 4 is reached by the optical output waveguide 6, and all the channel waveguides 4a of the array waveguide 4 have different lengths. After propagating, there is a phase shift of individual light,
The wavefront of the focused light is tilted according to the amount of deviation, and the tilt angle determines the position where light is focused.

In the arrayed waveguide diffraction grating, when the light is incident on the second slab waveguide from the arrayed waveguide, the angle at which the light is focused (diffraction angle) is φ, and this angle φ and There is a relationship as shown in the following equation (1) between the wavelength of the radiated light (light transmission center wavelength) λ.

N _s · d · sin φ + n _c · ΔL = m · λ (1)

N _s is the equivalent refractive index of the first and second slab waveguides, d is the distance between the channel waveguides on the first and second slab waveguide sides, φ is the diffraction angle, and n _c Is the equivalent refractive index of the arrayed waveguide, ΔL is the difference in length between adjacent channel waveguides, and m is the diffraction order.

Generally, since the refractive index of glass material such as quartz changes with temperature, the refractive indices n _s and n _{c of the} waveguide change with temperature, and the relationship between λ and φ in the equation (1). Changes. Therefore, when the temperature changes, the light transmission characteristic of the arrayed waveguide diffraction grating changes, and the light transmission center wavelength changes.

This amount of change is about 0.01 nm / ° C. in the case of a circuit using a quartz material, and in the temperature range of 0 ° C. to 70 ° C. which is an operating temperature range normally required for optical communication, Since the center wavelength of light transmission changes by 0.7 nm or more, it is a size that cannot be ignored practically.

Therefore, when using the arrayed waveguide diffraction grating, a temperature adjustment module is provided on the arrayed waveguide diffraction grating chip as an optical waveguide chip to adjust the temperature of the arrayed waveguide diffraction grating. .

FIG. 9 is a sectional view showing an example of an optical waveguide module having a temperature adjusting module. This optical waveguide module includes an optical waveguide chip 9 of an arrayed waveguide diffraction grating chip and a soaking plate 1 in a package 20.
2 and the temperature control module 8 are provided. The temperature adjustment module 8 and the optical waveguide chip 9 are superposed on each other, and a soaking plate 12 is provided between the joint surface of the optical waveguide chip 9 and the joint surface of the temperature adjustment module 8.

The soaking plate 12 is a plate made mainly of a material having high thermal conductivity such as copper or aluminum. The heat equalizing plate 12, the optical waveguide chip 9 and the temperature adjusting module 8 are usually joined by a silicone oil compound (silicone grease) or the like (not shown) having excellent thermal conductivity. As the silicone grease, for example, product name SC10 manufactured by Toray Dow Corning Co., Ltd.
2 etc. are applied.

FIG. 8 shows the essential structure of the optical waveguide module in an exploded state. As shown in the figure, on the upper surface of the optical waveguide chip 9, the chip upper plate 1 is provided on the end side thereof.
9 are joined and the end faces are polished. Optical waveguide chip 9
An optical fiber array 21 whose end face is polished is connected to the. The optical waveguides of the optical waveguide chip 9 (in this case, the optical input waveguide 2 and the optical output waveguide 6 of the arrayed waveguide diffraction grating circuit) are optically connected to the optical fibers 22 of the optical fiber array 21, respectively. .

The temperature adjusting module 8 has at least one of a heat generating function and a heat absorbing function. 8,
In the example shown in FIG. 9, the temperature adjustment module 8 is formed by a Peltier module having a plurality of Peltier elements 25, and this Peltier module has both a heat generating function and a heat absorbing function.

In the Peltier module, a plurality of Peltier elements 25 are arranged between the upper substrate 23 and the lower substrate 24. The upper substrate 23 and the lower substrate 24 are generally formed of ceramic substrates. The Peltier element 25 is made of P-type and N-type semiconductors, and these P-type semiconductors and N-type semiconductors are arranged so as to be electrically alternately connected.

By a temperature controller (not shown),
When the Peltier module is energized via the lead wire 26, a current flows through the P-type semiconductor and the N-type semiconductor, and endothermic and exothermic reactions are obtained.

The temperature adjusting module 8 is adjusted by the temperature controller so that the temperature detected by a temperature detecting element such as an RTD (Resistance Temperature Device) or a resistance temperature detecting element (not shown) becomes a predetermined set temperature. To do. Then, the temperature of the optical waveguide chip 9 is entirely uniform due to the heat diffusion by the soaking plate 12.
Moreover, it is configured to be constant.

[0024]

However, as described above, the structure in which the heat equalizing plate 12 is provided between the optical waveguide chip 9 and the temperature control module 8 is the temperature control module 8.
Therefore, both the temperature of the optical waveguide chip 9 and the temperature of the heat equalizing plate 12 are controlled, and there is a problem that the power consumption during the temperature control increases.

Further, in general, an optical waveguide module in which an optical waveguide chip 9 such as an arrayed waveguide diffraction grating is housed in a housing such as a package 20 is required to be small in size, and particularly, the size in the thickness direction. Is desired to be small, but there is a problem that the thickness of the optical waveguide module becomes large when the soaking plate 12 is used.

For example, an optical waveguide module incorporated in an optical communication system has a thickness (A shown in FIG. 9).
Is required to be 8.5 mm or less, but it is very difficult to satisfy this thickness in the above-mentioned configuration having the heat equalizing plate 12.

Further, since the soaking plate 12 is required to have high thermal conductivity, it is desirable to form the soaking plate 12 from copper, but the soaking plate 12 using copper is expensive. Further, since it is necessary to plate with nickel or the like in order to prevent copper from being oxidized, the price of the optical waveguide module formed using the heat equalizing plate 12 made of copper becomes high.

Therefore, the soaking plate 12 is omitted, and as shown in FIG. 6, the optical waveguide chip 9 and the temperature control module 8 are directly joined (without the soaking plate 12) by a silicone oil compound or the like. It is possible to do it.

However, the Peltier module forming the temperature control module 8 warps as follows during its operation. Therefore, if the optical waveguide chip 9 and the temperature adjustment module 8 are directly joined, there arises a problem that the optical waveguide chip 9 is affected by the warp of the temperature adjustment module 8.

That is, in the operation of the Peltier module, one of the upper substrate 23 and the lower substrate 24 serves as a heat absorbing surface, and the opposite substrate serves as a heat generating surface.
The temperature difference between the lower substrate 24 and the lower substrate 24 changes greatly, and the upper substrate 23 and the lower substrate 24 warp due to the thermal contraction thereof. Further, the amount of warp changes depending on the temperature difference between the upper substrate 23 and the lower substrate 24.

For example, FIG. 7 shows the temperature dependence of the warp of the Peltier module. This figure shows the results of measuring the warp of the Peltier module with a surface roughness meter when the Peltier module is placed on the heat radiation fins and the surface temperature of the upper substrate 23 is energized by the temperature controller so as to reach the set temperature. is there.

(A), (b) and (c) of FIG.
Under the atmosphere of about 0 ° C,
The measurement results are obtained at 20 ° C. and 70 ° C., and the measurement length is 14 mm in both cases.

As shown in FIG. 7A, when the surface temperature of the upper substrate 23 is 0 ° C., the concave shape is warped by about 2 μm, and as shown in FIG. 7C, the surface temperature of the upper substrate 23. Is 70
It can be seen that the convex shape warps by about 1 μm at a temperature of ℃.

This is because when the surface temperature of the upper substrate 23 is 0 ° C., the lower substrate 24 becomes high in temperature, so that the upper substrate 23 contracts and the lower substrate 24 expands due to thermal contraction, so that the concave substrate warps. When the surface temperature of the upper substrate 23 is 70 ° C., the lower substrate 24 becomes a low temperature.
Is expanded and the lower substrate 24 is contracted, so that it warps in a convex shape. Also, the difference in warp between 0 ° C and 70 ° C is about 3
μm.

Further, for example, when the surface temperature of the upper substrate 23 of the Peltier module is kept constant at 40 ° C. and the external temperature becomes 70 ° C., the upper substrate 23 of the Peltier module 23.
Since the surface of is a heat absorbing surface, the lower substrate 2 which is a heat generating surface.
The temperature becomes lower than 4 and the concave shape warps.

On the contrary, for example, when the surface temperature of the upper substrate 23 of the Peltier module is kept constant at 40 ° C. and the external temperature becomes 0 ° C., the upper substrate 2 of the Peltier module 2
Since the surface of 3 becomes a heat generating surface, the temperature of the lower substrate 24 becomes higher than that of the lower substrate 24, which becomes a heat absorbing surface, and the convex shape is warped.

When the optical waveguide chip 9 is directly joined to the Peltier module, if the Peltier module warps as described above, the warp is transmitted to the optical waveguide chip 9 and the optical waveguide chip 9 also warps. become.

Even when a temperature control module having a heater module having a heat generating function is applied as the temperature control module 8, a bimetal effect occurs due to the difference in thermal expansion coefficient between the temperature control module 8 and the optical waveguide chip 9. , Warpage occurs.

Since the refractive index of the optical waveguide changes depending on the stress applied to the optical waveguide, when the optical waveguide chip 9 is warped, the following equation (2) is used even if the temperature of the optical waveguide chip 9 is kept constant. The refractive index n shown in () changes, and the wavelength λ shown in the equation (1) changes. Then, in the optical waveguide circuit such as the arrayed waveguide diffraction grating in which the optical waveguide chip 9 is formed, the light transmission center wavelength of the light output from each optical output waveguide 6 changes.

N = C · σ (2)

In the equation (2), n is the refractive index of the optical waveguide forming the optical waveguide circuit, C is the photoelastic constant of the optical waveguide, and σ is the stress applied to the optical waveguide. here,
When the stress applied to the optical waveguide is a compressive stress, the value of σ becomes + (plus), and when the stress applied to the optical waveguide is a tensile stress, the value of σ becomes − (minus). In addition, the photoelastic constant C of the optical waveguide made of quartz glass material
The value of is a negative value.

Therefore, when the optical waveguide chip 9 warps in a convex shape and a compressive stress is applied to the optical waveguide, the refractive index of the optical waveguide becomes small from the relationship shown in the equation (2), and the light transmission center wavelength becomes From the relationship shown in 1), the wavelength shifts to the short wavelength side (-side). On the contrary, when the optical waveguide chip 9 warps in a concave shape and a tensile stress is applied to the optical waveguide, the refractive index of the optical waveguide increases from the relationship shown in the equation (2).
The center wavelength of light transmission shifts to the long wavelength side (+ side) from the relationship shown in Expression (1).

The above results are summarized in Table 1.

[0044]

[Table 1]

For example, an arrayed waveguide diffraction grating is generally required to have a wavelength accuracy of 0.05 nm or less. That is, the arrayed waveguide diffraction grating is required to have a shift amount of the center wavelength of light transmission of 0.05 nm or less. Therefore, as described above, the fact that the light transmission center wavelength of the arrayed waveguide diffraction grating chip changes due to the influence of the warp of the temperature adjustment module 8 becomes a problem in practical use.

Also in the optical waveguide module including the optical waveguide chip 9 having another optical waveguide circuit, the light transmission center wavelength (optical waveguide chip 9 of the optical waveguide chip 9 is affected by the warp of the temperature adjusting module 8. It is a problem that the light transmission center wavelength of the optical waveguide circuit of 9 changes.

The present invention has been made to solve the above problems, and an object thereof is to enable accurate temperature control of an optical waveguide chip with low power consumption, and to transmit light by warping of the optical waveguide chip. An object of the present invention is to provide an optical waveguide module capable of suppressing center wavelength shift.

[0048]

In order to achieve the above object, the present invention has the following constitution as means for solving the problem. That is, the first aspect of the invention is based on at least an optical waveguide chip having an optical waveguide circuit whose light transmission characteristic changes depending on temperature, a temperature detecting element for detecting the temperature of the optical waveguide chip, and a temperature detected by the temperature detecting element. A temperature adjusting module for adjusting the temperature of the optical waveguide chip, wherein the temperature adjusting module and the optical waveguide chip are overlapped and directly bonded to each other, and the temperature detecting element is an optical waveguide circuit of the optical waveguide chip. The structure provided at the position for detecting the temperature at the position away from the center position is a means for solving the problem.

In addition to the structure of the first invention, the second invention is such that when the ambient temperature is higher than the temperature in the optical waveguide module, the temperature detected by the temperature detecting element is at the center position of the optical waveguide circuit of the optical waveguide chip. It is a position that becomes higher than the temperature,
Further, when the ambient temperature is lower than the temperature inside the optical waveguide module, the temperature detecting element is provided at a position where the temperature detected by the temperature detecting element becomes lower than the temperature at the center position of the optical waveguide circuit of the optical waveguide chip. As a means to solve.

Further, in the third invention, in addition to the configuration of the first or second invention, the temperature detecting element is configured such that the light transmission center wavelength shift of the optical waveguide chip based on the warp of the temperature adjustment module and the temperature detection. A means for solving the problem is provided by a structure in which the light transmission center wavelength shift of the optical waveguide chip based on the difference between the detected temperature of the element and the temperature of the optical waveguide circuit center position of the optical waveguide chip cancels each other. .

Further, a fourth invention is the above-mentioned first to third inventions.
In addition to the configuration of any one of the inventions, the optical waveguide circuit includes at least one optical input waveguide, a first slab waveguide connected to an output side of the optical input waveguide, and the first optical waveguide. Array slab waveguide connected to the output side of the slab waveguide, the array waveguide including a plurality of side-by-side channel waveguides having different set amounts from each other, and a second slab waveguide connected to the output side of the array waveguide. And a structure having a circuit of an arrayed waveguide diffraction grating including a plurality of optical output waveguides connected to the output side of the second slab waveguide is a means for solving the problem.

[0052]

BEST MODE FOR CARRYING OUT THE INVENTION Embodiments of the present invention will be described below with reference to the drawings. In the description of the present embodiment, the same names as those in the conventional example will be denoted by the same reference numerals, and duplicate description thereof will be omitted or simplified.

FIG. 1 is a plan view showing the configuration of the main part of an embodiment of the optical waveguide module according to the present invention. The optical waveguide module of the present embodiment is also shown in FIG.
The optical fiber array 21, the optical fiber 22, and the package 20 are provided as in the example shown in FIG. 1, but these configurations are omitted in FIG.

As shown in FIG. 1, the optical waveguide module of this embodiment is an arrayed waveguide diffraction grating module. The optical waveguide chip 9 and the temperature adjustment module 8 are overlapped with each other with the center position C2 of the temperature adjustment module 8 and the optical waveguide circuit center position C1 of the optical waveguide chip 9 being offset from each other and directly joined.

The light transmission center wavelength of the optical waveguide circuit is
The center position of the phase portion of the optical waveguide circuit is defined as the center position of the optical waveguide circuit in the present specification because it changes due to the refractive index of the optical waveguide circuit, particularly, the refractive index of the phase portion.

In the case of the arrayed-waveguide diffraction grating, the phase portion is the formation region of the arrayed waveguide 4. Therefore, the optical waveguide chip 9 having the optical waveguide circuit of the arrayed waveguide diffraction grating
For example, the position of C1 shown in FIGS. 1 and 2 is the center position of the optical waveguide circuit.

That is, as shown in FIG. 2, the optical waveguide circuit center position C1 is an intersection A between the center line R of the arrayed waveguide formation region and the channel waveguides 4a arranged in the innermost side.
Is the midpoint of the line segment AB connecting the center line R and the intersection B of the channel waveguides 4a arranged on the outermost side.

The feature of this embodiment is that the temperature adjusting module 8 and the optical waveguide chip 9 are directly bonded to each other, and the temperature detecting element 3 is used.
0 is provided at a position where the temperature at a position apart from the temperature of the optical waveguide circuit center position C1 of the optical waveguide chip 9 is detected. In other words, the temperature detecting element 30 is arranged at a position where the detected temperature and the temperature of the optical waveguide circuit center position C1 of the optical waveguide chip 9 are different.

In the temperature detecting element 30, when the ambient temperature is higher than the temperature inside the optical waveguide module, the temperature detected by the temperature detecting element 30 is higher than the temperature at the optical waveguide circuit center position C1 of the optical waveguide chip 9. When the ambient temperature is lower than the temperature inside the optical waveguide module, the temperature detecting element 30 is provided at a position lower than the temperature of the optical waveguide circuit center position C1 of the optical waveguide chip 9.

Further, in the present embodiment, the temperature detecting element 30 has the optical transmission center wavelength shift of the optical waveguide chip 9 based on the warp of the temperature adjusting module 8 and the temperature detecting element 3.
The light transmission center wavelength shift of the optical waveguide chip 9 based on the difference between the detected temperature of 0 and the temperature of the optical waveguide circuit center position of the optical waveguide chip 9 is arranged at a position where they cancel each other out.

In the present embodiment, the temperature adjustment module 8 is a Peltier module, and the temperature adjustment function and the mode of warpage during temperature adjustment are the same as those described above.

The substrate 1 of the optical waveguide chip 9 is made of single crystal silicon (S) having a thermal conductivity of 125.6 W / (m · K).
The substrate 1 has a thickness of 1 mm. The value of the thermal conductivity of silicon is very high, 100 times or more compared with the value of the thermal conductivity of glass 1.2 W / (m · K), and the value of the thermal conductivity of iron 67.0 W / (m · K). K) and the thermal conductivity of solder 33.5 W / (m · K).

The value of the thermal conductivity of silicon is 335.9, which is the value of the thermal conductivity of copper used as the soaking element 12.
W / (mK) and thermal conductivity of aluminum 234.5W
Compared with / (m · K), it is about 1/2 to 1/3.
As described above, since the thermal conductivity of silicon is very good, using silicon as the substrate 1 is effective for keeping the temperature of the optical waveguide chip 9 substantially uniform.

Optical waveguide chip 9 and temperature control module 8
Are joined by, for example, silicone RTV (silicone room temperature vulcanized rubber). This silicone RTV
Has excellent heat resistance and thermal conductivity.

Optical waveguide chip 9 and temperature control module 8
As an example of a silicone RTV suitable for joining to, the SE series manufactured by Toray Dow Corning (SE4400, SE
4410, SE4420, SE4422, SE444
0, SE4450, SE4486, SE9184) and other heat conductive silicone RTVs.

These thermally conductive silicone RTVs have a resistance of 0.
It has a thermal conductivity of 75 to 1.05 W / (m · K), and that of a general silicone RTV (0.17 to
It has a thermal conductivity several times higher than 0.33 W / (m · K).

By the way, if the optical waveguide chip 9 and the temperature adjusting module 8 are directly joined without providing the soaking plate 12,
Heat generation (heat radiation) and heat absorption by the temperature adjustment module 8 are transmitted to the optical waveguide chip 9 with a certain temperature gradient. Therefore, depending on the arrangement position of the temperature detecting element 30,
A difference occurs between the temperature detected by the temperature detecting element 30 and the temperature at the center position of the optical waveguide circuit of the optical waveguide chip 9.

Here, the external environment temperature is higher than the temperature inside the optical waveguide module, and the detected temperature T1 of the temperature detecting element 30 is the optical waveguide circuit center position C of the optical waveguide chip 9.
When the temperature is higher than the temperature T2 of 1 (when T1> T2), the temperature adjustment module 8 performs temperature adjustment based on the temperature detected by the temperature detection element 30.
Will absorb too much heat.

As a result, as is clear from the above equations (1) and (2), the light transmission center wavelength of the optical waveguide chip 9 is shifted (shifted) to the short wavelength side (− side).

Further, the external environment temperature is higher than the temperature inside the optical waveguide module, and the detected temperature T1 of the temperature detecting element 30 is the optical waveguide circuit center position C1 of the optical waveguide chip 9.
When the temperature is adjusted by the temperature adjustment module 8 based on the temperature detected by the temperature detection element 30 when the temperature is lower than the temperature T2 (when T1 <T2), the heat absorption by the temperature adjustment module 8 is smaller than the required heat absorption. It will not be cooled enough.

As a result, as is clear from the equations (1) and (2), the light transmission center wavelength of the optical waveguide chip 9 shifts to the long wavelength side (+ side).

Further, the external environment temperature is lower than the temperature inside the optical waveguide module, and the detected temperature T1 of the temperature detecting element 30 is the optical waveguide circuit center position C of the optical waveguide chip 9.
When the temperature is higher than the temperature T2 of 1 (when T1> T2), if the temperature is adjusted by the temperature adjustment module 8 based on the temperature detected by the temperature detection element 30, the heat generated by the temperature adjustment module 8 is higher than the required heat generation. It becomes small and cannot be warmed sufficiently.

As a result, as is clear from the equations (1) and (2), the light transmission center wavelength of the optical waveguide chip 9 shifts to the − side.

The external environment temperature is lower than the temperature inside the optical waveguide module, and the detected temperature T1 of the temperature detecting element 30 is the optical waveguide circuit center position C1 of the optical waveguide chip 9.
When the temperature is lower than the temperature T2 (when T1 <T2), the temperature adjustment module 8 adjusts the temperature based on the temperature detected by the temperature detection element 30.
Excessive heat will be generated.

As a result, as is clear from the equations (1) and (2), the light transmission center wavelength of the optical waveguide chip 9 shifts to the + side.

The above is summarized in Table 2.

[0077]

[Table 2]

Here, the optical transmission center wavelength shift of the optical waveguide circuit of the optical waveguide chip 9 based on the warpage of the temperature control module 8 as shown in Table 1 is called the warpage-induced wavelength shift. The value of the wavelength shift caused by the warp is determined by the relationship between the environmental temperature and the set temperature of the temperature adjustment module 8.

The light transmission center of the optical waveguide circuit of the optical waveguide chip 9 based on the relationship between the detected temperature T1 of the temperature detecting element 30 and the temperature T2 of the optical waveguide circuit center position of the optical waveguide chip 9 shown in Table 2. The wavelength shift is called the wavelength shift due to the detected temperature shift. The value of the wavelength shift due to the detected temperature shift also changes depending on the relationship between the environmental temperature and the temperature inside the optical waveguide module.

Then, the present inventor determines the arrangement position of the temperature detecting elements so that the wavelength shift caused by the warp and the wavelength shift caused by the detected temperature shift cancel each other out, thereby avoiding the heat equalizing plate 12. It is considered that even if the optical waveguide chip 9 and the temperature adjusting module 8 are directly bonded, the shift of the light transmission center wavelength of the optical waveguide chip 9 due to the warp of the temperature adjusting module 8 can be suppressed.

That is, when the temperature adjustment module 8 is controlled to absorb heat (when the environmental temperature is high), the warp of the temperature adjustment module 8 shifts the light transmission center wavelength to the + side, so that T1> T2. Thus, the center wavelength of light transmission is shifted to the − side.

When the temperature control module 8 is controlled to generate heat (when the ambient temperature is low), the warp of the temperature control module 8 shifts the center wavelength of light transmission to the negative side, so that T1 <T2. Then, the center wavelength of light transmission is shifted to the + side.

The arrangement position of the temperature detecting element 30 satisfying the above conditions is determined as follows. First, as shown in FIG. 1, from the temperature detection position of the temperature detection element 30 (in this case, the arrangement position of the temperature detection element 30) to the center position of the temperature adjustment module 8 (center position of the upper substrate surface of the Peltier module) C2. Is L1. Further, the distance between the center position C2 of the temperature adjustment module and the center position C1 of the optical waveguide circuit of the optical waveguide chip 9 is L2.

Then, the temperature detecting element 30 is arranged so that the relationship between these distances L1 and L2 is L1 <L2.

Here, in order to satisfy L1 <L2, at least the center position of the temperature control module 8 and the center position C1 of the optical waveguide circuit of the optical waveguide chip 9 must be displaced.

Then, in the present embodiment, the optical transmission center wavelength shift of the optical waveguide chip 9 due to the warp of the temperature adjustment module 8 is calculated by detecting the temperature T1 of the temperature detecting element 30 and the optical waveguide circuit center position of the optical waveguide chip 9. The temperature detecting element 30 is arranged at a position where they are substantially canceled by the shift of the light transmission center wavelength of the optical waveguide chip 9 based on the difference from the temperature T2.

That is, the detected temperature T1 of the temperature detecting element 30
And the temperature T2 at the center position of the optical waveguide circuit of the optical waveguide chip 9.
And the difference ΔT between the temperature adjustment module 8 and the light transmission center wavelength shift amount Δλ of the optical waveguide chip 9 based on the warp of the temperature adjustment module 8 are in a position represented by the formula (3).
Was placed.

[0088] ΔT = (Δλ / 0.011) ° C. (3)

The arrangement position of the temperature detecting element 30 satisfying the expression (3) is the same as that of the optical waveguide chip 9, the temperature adjusting module 8 and the temperature detecting element 30 applied to the present embodiment. Using the optical waveguide chip 9, the temperature adjustment module 8 and the temperature detection element 30, it was obtained in advance by experiments or the like.

The example of the present embodiment is configured as described above. In the optical waveguide module of the example of the present embodiment, the optical transmission center wavelength shift of the optical waveguide chip 9 due to the warp of the temperature adjusting module 8 is detected by the temperature detecting element. The temperature detecting element 30 is disposed at a position where the temperature T1 of the optical waveguide chip 9 and the temperature T2 at the center position of the optical waveguide circuit of the optical waveguide chip 9 cancel each other due to the shift of the light transmission center wavelength of the optical waveguide chip 9. .

Therefore, in the optical waveguide module of the present embodiment, even if the optical waveguide chip 9 and the temperature adjusting module 8 are directly joined, the optical waveguide with small power consumption can suppress the deviation of the light transmission center wavelength of the optical waveguide chip 9. Modules can be realized.

Further, in the optical waveguide module of this embodiment, the center position of the temperature adjusting module 8 and the optical waveguide circuit center position C1 of the optical waveguide chip 9 are displaced from each other so that the temperature detecting module 30 moves from the temperature detecting position to the temperature adjusting module. The distance L1 to the center position C2 of 8 is the center position C2 of the temperature control module and the center position C of the optical waveguide circuit of the optical waveguide chip 9.
This is a simple configuration in which the temperature detection element 30 is provided at a position where the distance to 1 is smaller than L2, and the shift of the light transmission center wavelength due to the warp of the temperature adjustment module 8 is suppressed.

Therefore, the optical waveguide module of this embodiment can be a small-sized optical waveguide module that can be easily manufactured.

The present invention is not limited to the above-mentioned embodiments, but can take various modes. For example,
Although the temperature detecting element 30 is provided at the position shown in FIG. 1 in the above embodiment, the temperature detecting element 30 is provided at a position where the temperature is detected at a position apart from the optical waveguide circuit center position C1 of the optical waveguide chip 9. By arranging the optical waveguide chip 9
It suffices if the shift of the central wavelength of light transmission can be suppressed.

That is, the temperature detecting element 30 is, for example, as shown in FIG.
As shown in, the center line R in the arrangement region of the arrayed waveguide 4
You may provide in the position deviated from. Further, as shown in FIG. 3, the arrayed waveguide 4 may be provided at a position outside the frame F showing the entire installation region. In this case, the temperature detecting element 30 may be provided on the center line R as shown by E in the figure, or the temperature detecting element 30 may be placed at a position deviated from the center line R as shown by G in the figure. It may be provided.

Further, in the above embodiment, the temperature adjusting module 8 is provided at a position overlapping with a part of the area where the arrayed waveguide 4 is arranged. It may be provided at a deviated position.

Further, although the optical waveguide chip 9 is the arrayed waveguide diffraction grating chip in the above embodiment, the optical waveguide chip 9 is not limited to the arrayed waveguide diffraction grating chip and may be set appropriately. Therefore, the present invention can be formed by applying the optical waveguide chip 9 having an optical waveguide circuit whose light transmission characteristics change depending on temperature, such as an optical waveguide circuit using a well-known Mach-Zehnder circuit.

FIG. 5 is a plan view showing an example of the Mach-Zehnder circuit (Mach-Zehnder optical interferometer circuit). As shown in FIG. 5, the Mach-Zehnder circuit includes two optical waveguides 14, A plurality of directional coupling portions 16 in which the optical waveguides 14 and 15 are arranged close to each other,
17 are formed in the longitudinal direction of the optical waveguides 14 and 15 with a space therebetween.

When the optical waveguide circuit of the optical waveguide chip 9 is a Mach-Zehnder circuit as shown in FIG. 5, the two optical waveguides 14 and 15 sandwiched between the directional coupling portions 16 and 17 serve as phase portions. The midpoint of a line segment AB connecting the center line R of the phase portion and the intersections A and B of the two optical waveguides 14 and 15 is the optical waveguide circuit center position C1.

Further, in the above embodiment, the substrate 1 of the optical waveguide chip 9 is made of silicon.
The substrate 1 may be a substrate other than silicon. However, the substrate 1 is made of silicon or the like and has a thermal conductivity of 50 W / (m ·
K) When formed of the above materials, when the temperature adjustment module 8 is provided on the substrate 1 side as in the above embodiment,
The temperature adjustment of the optical waveguide chip 9 by the temperature adjustment module 8 can be performed even better.

Further, in the above embodiment, the temperature adjusting module 8 is provided on the substrate 1 side of the optical waveguide chip 9,
The temperature adjustment module 8 may be provided on the waveguide formation region 10 side.

Further, in the above embodiment, the temperature adjustment module 8 and the optical waveguide chip 9 are joined by silicone RTV (silicone RTV rubber) having excellent thermal conductivity. However, the temperature adjustment module is made by a bonding agent other than silicone RTV. 8 and the optical waveguide chip 9 may be joined.

Further, in the above embodiment, the temperature adjusting module 8 is a Peltier module, but the temperature adjusting module 8 may be a heater module having a heater circuit.

[0104]

According to the present invention, since the temperature detecting element for detecting the temperature of the optical waveguide chip is provided at the position for detecting the temperature at the position away from the center position of the optical waveguide circuit of the optical waveguide chip, The center wavelength of light transmission of the optical waveguide chip shifts based on the difference between the temperature detected by the temperature detecting element and the temperature at the center position of the optical waveguide circuit of the optical waveguide chip. Therefore, due to this wavelength shift, it is possible to reduce the wavelength shift of the light transmission center of the optical waveguide chip caused by the warp during the operation of the temperature adjustment module.

Therefore, according to the present invention, the optical waveguide chip and the temperature control module can be directly joined without using a soaking plate,
It is possible to realize a small-sized optical waveguide module in which the temperature of the optical waveguide chip can be stably adjusted with low power consumption and the light transmission center wavelength can be set to a stable value.

Further, in the present invention, when the ambient temperature is higher than the temperature inside the optical waveguide module, the temperature detected by the temperature detecting element is higher than the temperature at the center of the optical waveguide circuit of the optical waveguide chip, and the ambient temperature is higher. Is lower than the temperature inside the optical waveguide module, the temperature detecting element is provided at a position where the temperature detected by the temperature detecting element is lower than the temperature at the center position of the optical waveguide circuit of the optical waveguide chip. It can be demonstrated more efficiently.

That is, in this configuration, the optical transmission center wavelength shift of the optical waveguide chip caused by the difference between the detected temperature of the temperature detection element and the temperature of the optical waveguide circuit center position of the optical waveguide chip causes It is possible to efficiently reduce the shift of the light transmission center wavelength of the optical waveguide chip caused by the warp during operation.

Further, in the present invention, the temperature detecting element includes the light transmission center wavelength shift of the optical waveguide chip due to the warp of the temperature adjustment module, the temperature detected by the temperature detecting element and the temperature of the optical waveguide circuit center position of the optical waveguide chip. According to the configuration in which the optical transmission center wavelength shift of the optical waveguide chip due to the difference between the optical waveguide chip and the optical waveguide chip is arranged at a position where they cancel each other, the optical waveguide chip is affected by the warpage during operation of the temperature adjustment module, It is possible to reliably suppress the shift of the light transmission center wavelength of, and always control the light transmission center wavelength to the set wavelength.

Further, according to the present invention, the optical waveguide circuit has a configuration of an arrayed waveguide diffraction grating circuit.
An optical waveguide module that plays an important role in wavelength division multiplex transmission and that can precisely control the temperature of the arrayed waveguide grating circuit that requires strict temperature control, and that fulfills a good function for wavelength division multiplex transmission. .

[Brief description of drawings]

FIG. 1 is a main part configuration diagram of an embodiment of an optical waveguide module according to the present invention.

FIG. 2 is an explanatory view showing an arrangement example of temperature detection elements provided at a center position of an optical waveguide chip and a position deviated from this position.

FIG. 3 is an explanatory view showing another embodiment example of the optical waveguide module according to the present invention.

FIG. 4 is an explanatory diagram showing an example of an arrayed waveguide diffraction grating chip.

FIG. 5 is an explanatory diagram showing an example of a Mach-Zehnder circuit.

FIG. 6 is a cross-sectional explanatory view of an optical waveguide module formed by directly joining an optical waveguide chip and a temperature adjustment module without providing a soaking plate.

FIG. 7 is an explanatory diagram showing a warped state depending on the temperature of the Peltier module.

FIG. 8 is an explanatory diagram showing an example of a conventional optical waveguide module in an exploded state.

9 is a cross-sectional explanatory view of the optical waveguide module shown in FIG.

[Explanation of symbols]

1 substrate 2 Optical input waveguide 3 First slab waveguide 4 Array waveguide 5 Second slab waveguide 6 Optical output waveguide 8 Temperature control module 9 Optical waveguide chip 30 Temperature detection element

Continued front page    (72) Inventor Toshihiko Ota             2-6-1, Marunouchi, Chiyoda-ku, Tokyo             Kawa Electric Industry Co., Ltd. (72) Inventor Tsune Satoshi             2-6-1, Marunouchi, Chiyoda-ku, Tokyo             Kawa Electric Industry Co., Ltd. F term (reference) 2H047 KA03 KA12 LA03 LA19 MA05                       NA01 QA02 RA00                 2H079 AA06 BA03 CA04 DA22 EA02                       EA03 EA05 EB27 FA01

Claims (4)

[Claims] 1. An optical waveguide chip having an optical waveguide circuit whose light transmission characteristics change at least with temperature, a temperature detecting element for detecting the temperature of the optical waveguide chip, and the optical waveguide based on the temperature detected by the temperature detecting element. A temperature adjusting module for adjusting the temperature of the chip, the temperature adjusting module and the optical waveguide chip are directly bonded to each other in an overlapping manner, and the temperature detecting element is located from the optical waveguide circuit center position of the optical waveguide chip. An optical waveguide module, which is provided at a position for detecting a temperature at a remote position. 2. When the environmental temperature is higher than the temperature inside the optical waveguide module, the temperature detected by the temperature detecting element is higher than the temperature at the center position of the optical waveguide circuit of the optical waveguide chip, and the environmental temperature is at the optical waveguide module. 2. The optical detecting device according to claim 1, wherein the temperature detecting device is provided at a position where the temperature detected by the temperature detecting device is lower than the temperature at the center position of the optical waveguide circuit of the optical waveguide chip when the temperature is lower than the internal temperature. Waveguide module. 3. The temperature detecting element comprises a light transmission center wavelength shift of an optical waveguide chip based on a warp of a temperature adjustment module,
The light transmission center wavelength shift of the optical waveguide chip based on the difference between the detected temperature of the temperature detection element and the temperature of the optical waveguide circuit center position of the optical waveguide chip is arranged at a position where they cancel each other out. The optical waveguide module according to claim 1 or claim 2. 4. The optical waveguide circuit includes at least one optical input waveguide and a first optical waveguide connected to an output side of the optical input waveguide.
Of the slab waveguide and an array waveguide connected to the output side of the first slab waveguide, the array waveguide including a plurality of channel waveguides arranged in parallel with different lengths from each other, and an output side of the array waveguide. An arrayed waveguide diffraction grating circuit comprising a connected second slab waveguide and a plurality of optical output waveguides connected to the output side of the second slab waveguide. The optical waveguide module according to any one of claims 1 to 3.