JP3929807B2 - Optical waveguide module - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a waveguide type optical circuit having an interferometer sensitive to environmental temperature, and more particularly to an optical waveguide module provided with a temperature controller.
[0002]
[Prior art]
Waveguide-type optical circuits used for optical communication are sensitive to changes in environmental temperature. A typical example of the waveguide type optical circuit is a planar lightwave circuit (PLC) in which an optical waveguide having a core and cladding structure is formed on a substrate such as silicon or quartz. A type of PLC, such as an arrayed waveguide optical multiplexing / demultiplexing circuit (AWG) or a Mach-Zehnder interferometer (MZ), which has an interferometer, changes the optical path length depending on changes in environmental temperature. Since the refractive index fluctuates, the wavelength characteristic has temperature dependence.
[0003]
Waveguide-type optical circuits having interferometers as components are sensitive to ambient temperature and environmental temperature as described above, and the wavelength characteristics fluctuate when the temperature of these waveguide-type optical circuits differs from the set temperature by several degrees. Often to do. An interferometer of a waveguide type optical circuit is composed of a part that divides and joins light and an optical delay part that is between them and gives a difference in optical path length to each of the divided lights. The division and merging portion in the AWG is a slab waveguide, and the optical delay portion is an arrayed waveguide. The division and confluence portion in the MZ is a directional coupler, and the optical delay portion is an arm waveguide.
[0004]
As a temperature control method of the waveguide type optical circuit, there is a temperature controller represented by a heater or a Peltier element. A temperature controller using a heater is composed of a heater and a temperature sensor, and is heated by the heater so as to be kept constant at a temperature higher than room temperature, for example, 80 ° C., using the heater based on information from the temperature sensor. A temperature controller using a Peltier element is composed of a Peltier element and a temperature sensor, and is heated or cooled by the Peltier element and held at a constant temperature based on information from the temperature sensor. In either case, the temperature of the waveguide optical circuit is controlled by a temperature controller disposed on the back surface of the substrate on which the waveguide optical circuit is formed. The optical waveguide module is a waveguide type optical circuit provided with a temperature controller.
[0005]
When heated or cooled with a heater or Peltier element, a temperature distribution occurs depending on the location. When a large heater or Peltier element, or a plurality of heaters or Peltier elements are used, the temperature distribution difference can be reduced, but the temperature controller is increased in size and power consumption is increased. The temperature sensor does not measure the temperature of the entire waveguide optical circuit, but only measures the temperature around the temperature sensor, and controls between the heater and Peltier element and the temperature sensor. An error is generated.
[0006]
The temperature distribution on the substrate of the conventional optical waveguide module was observed with a thermoviewer (JTG-7200, manufactured by JEOL Datum Co., Ltd.), and the result displayed with an isotherm is shown in FIG. FIG. 1 shows an AWG that is a kind of PLC formed on a substrate. In FIG. 1, 11 is an isotherm, 12 is a PLC substrate, 13 is an arrayed waveguide, 14 is a slab waveguide, and 15 is an input / output waveguide. In FIG. 1, the isotherm interval is 1 ° C. As can be seen from FIG. 1, there are a plurality of isotherms in the AWG, and the entire AWG is not at a uniform temperature. The AWG is a waveguide type optical circuit having an interferometer, and its wavelength characteristic is very sensitive to temperature. Therefore, there is a disadvantage that the wavelength characteristic fluctuates especially when the temperature of the arrayed waveguide part 13 is not the designed temperature. there were. In FIG. 1, the arrayed waveguide 13 and the slab waveguide 14 are disposed within a temperature range of 6 ° C.
[0007]
The temperature distribution on a conventional MZ substrate is observed with a thermoviewer (JTG-7200, manufactured by JEOL Datum Co., Ltd.), and the result of the isotherm display is shown in FIG. FIG. 2 shows an MZ, which is a kind of PLC, formed on a substrate. In FIG. 2, 11 is an isotherm, 12 is a PLC substrate, 31 and 32 are arm waveguides, and 33 is a directional coupler. In FIG. 2, the isotherm interval is 1 ° C. As can be seen from FIG. 2, there are a plurality of isotherms in the MZ, and the entire MZ is not at a uniform temperature. MZ is a waveguide type optical circuit having an interferometer, like AWG, and its wavelength characteristics are very sensitive to temperature. Therefore, especially when the temperatures of arm waveguide 31 and arm waveguide 32 are not as designed. Has the disadvantage that the wavelength characteristics fluctuate. In FIG. 2, the arm waveguides 31 and 32 and the directional coupler 33 are disposed within a temperature range of 5 ° C.
[0008]
As explained in Fig. 1 or 2, AWG and MZ equipped with a temperature controller are not uniform in temperature as a whole, and are designed depending on the location due to the difference in distance from the heater and Peltier element placed on the back side. The temperature was different from the temperature. Therefore, an arrangement in which the interferometer of the waveguide type optical circuit crosses the isothermal line such as the arrayed waveguide 13 and the slab waveguide 14 in FIG. 1, the arm waveguides 31 and 32 and the directional coupler 33 in FIG. It was. As a result, there has been a problem that the wavelength characteristics of PLCs such as AWG and MZ fluctuate.
[0009]
[Problems to be solved by the invention]
In order to solve such a problem, an object of the present invention is to provide an arrangement in which an interferometer of a waveguide type optical circuit or a part of the interferometer does not cross an isotherm.
[0010]
[Means for Solving the Problems]
In order to achieve the above-described object, the present invention solves the problem by arranging an interferometer or a part of the interferometer of the waveguide type optical circuit along an isotherm formed by a temperature controller.
According to a first aspect of the present invention, there is provided an optical waveguide module comprising: a waveguide type optical circuit including an interferometer configured on a substrate; and a temperature controller for adjusting a temperature disposed on a back surface of the substrate. Is disposed in the vicinity of the back surface of a corresponding portion of the interferometer, and the interferometer is disposed along an isothermal line formed by the temperature controller.
[0011]
The second invention is a light guide having a waveguide-type optical circuit including an arrayed waveguide and two slab waveguides formed on a substrate, and a temperature controller for adjusting the temperature disposed on the back surface of the substrate. In the waveguide module, the temperature controller is disposed near a back surface of a corresponding portion of the array waveguide, and the array waveguide is disposed along an isotherm formed by the temperature controller. It is an optical waveguide module.
[0012]
A third invention is an optical waveguide having a waveguide-type optical circuit including an arrayed waveguide and two slab waveguides formed on a substrate, and a temperature controller for adjusting the temperature disposed on the back surface of the substrate. In the waveguide module, the temperature controller is disposed in the vicinity of the back surface of a corresponding portion of the waveguide optical circuit, and the arrayed waveguide and the two slab waveguides are isotherms formed by the temperature controller. It is an optical waveguide module characterized by being arranged along.
[0013]
According to a fourth aspect of the present invention, there is provided a waveguide type optical circuit including two directional couplers configured on a substrate and two arm waveguides connecting the two directional couplers, and a back surface of the substrate. An optical waveguide module having a temperature controller for adjusting a temperature, wherein the temperature controller is disposed in the vicinity of the back surface of the waveguide optical circuit, and the two directional couplers and the two directional characteristics are provided. In the optical waveguide module, the two arm waveguides connecting the coupler are arranged along an isotherm formed by the temperature controller.
[0014]
According to a fifth invention, in the optical waveguide module according to the first to fourth inventions, the waveguide type optical circuit disposed along the isothermal line is within 2.4 ° C., preferably within 2.1 ° C., more preferably Is an optical waveguide module characterized by being arranged in a temperature bandwidth within 1.5 ° C.
[0015]
DETAILED DESCRIPTION OF THE INVENTION
Hereinafter, embodiments of the present invention will be described with reference to the accompanying drawings.
(Embodiment 1)
FIG. 3 shows the arrangement of an AWG that is a waveguide type optical circuit of the present invention. In FIG. 3, 11 is an isotherm, 12 is a PLC substrate, 13 is an arrayed waveguide, 14 is a slab waveguide, and 15 is an input / output waveguide. In FIG. 3, the isotherm interval is 0.5 ° C. In the present embodiment, the heater is brought into direct contact with the back surface of the PLC substrate constituting the AWG. FIG. 4 shows a state where the heater is in direct contact with the PLC substrate. In FIG. 4, 12 is a PLC substrate, 20 is a soaking plate made of aluminum, and 21 is a temperature controller. The soaking plate 20 is provided in order to heat the entire PLC substrate uniformly to some extent with aluminum having good thermal conductivity. The temperature controller 21 has a structure in which the heater can directly contact the PLC substrate.
[0016]
In FIG. 3, an isotherm 11 is a temperature distribution actually measured by a thermo viewer (manufactured by JEOL Datum, JTG-7200). The central portion of the PLC substrate 12 is the hottest portion, and the central isotherm is 69.0 ° C. The temperature distribution is at intervals of 0.5 ° C. toward the outer periphery. As shown in FIG. 3, it is difficult to make the temperature of the entire PLC substrate 12 uniform even if a soaking plate is provided.
[0017]
In this embodiment, since the arrayed waveguide 13 is formed in a semicircular arc shape, the heating center of the heater is shifted from directly below the arrayed waveguide 13, so that as shown in FIG. 13 could be placed along two isotherms at 68.5 ° C. and 67.5 ° C. With such an arrangement, the ambient temperature of the arrayed waveguide 13 could be realized in a temperature range of 68.0 ± 0.5 ° C.
[0018]
Further, the slab waveguide 14 is formed in a substantially rectangular shape so that the array waveguide 13 is extended. As shown in FIG. 3, not only the array waveguide 13 but also the slab waveguide 14 is included. Thus, they could be arranged along two isotherms of 68.5 ° C. and 67.5 ° C. By adopting such an arrangement, the ambient temperature between the arrayed waveguide 13 and the slab waveguide 14 could be realized in a temperature range of 68.0 ± 0.5 ° C. which is the design temperature.
[0019]
Conventionally, only the part where the temperature sensor is installed is the design value temperature, and the temperature of the other part of the waveguide type optical circuit is different from the design value temperature. In the present embodiment, the waveguide type optical circuit can be kept within the design temperature range by arranging the waveguide type optical circuit along the isotherm, and the wavelength characteristic does not vary.
[0020]
Further, in the AWG, the deviation of the temperature distribution of the slab waveguide and the design value of the temperature set value mainly changes the effective refractive index of the slab waveguide from the design value. As a result, the demultiplexed wavelength becomes an error from the design value at the output port away from the center port. This tendency becomes stronger as the distance from the center port approaches the end port. Therefore, the configuration of FIG. 3 in which the AWG slab waveguide is also along the isotherm has an effect of improving the wavelength accuracy at the peripheral port far from the central port.
[0021]
In FIG. 3, the interval between the isotherms is displayed at 0.5 ° C. There are various allowable values of the design temperature of the waveguide type optical circuit depending on the specification, but most of them are ± 1.2 ° C. For this reason, when the interferometer of the waveguide type optical circuit is disposed beyond the width of the 2.4 ° C. isotherm, the allowable range of the design temperature is exceeded, resulting in fluctuations in wavelength characteristics. . Therefore, the interferometer of the waveguide type optical circuit needs to be arranged so that the interval between the isotherms is within 2.4 ° C.
[0022]
A temperature controller using a heater is heated by the heater so that the heat can be dissipated by the soaking plate. In a temperature controller using a Peltier element, heating or cooling is performed by the Peltier element so that heat can be radiated from the heat equalizing plate or absorbed by the heat equalizing plate. FIG. 5 shows the arrangement of the heat equalizing plate and the temperature controller described in FIG. The temperature controller uses a heater or a Peltier element as a heat source. Fig.5 (a) is a top view of a soaking | uniform-heating board and a temperature regulator, FIG.5 (b) is a front view. 5 (a) and 5 (b), 20 is a soaking plate, 21 is a temperature controller, and 22 is a temperature sensor. The soaking plate may have the shape shown in FIG. 6 as well as the shape shown in FIG. 6A is a plan view of the heat equalizing plate and the temperature controller, and FIG. 6B is a front view. 6 (a) and 6 (b), 20 is a soaking plate, 21 is a temperature regulator, and 22 is a temperature sensor.
[0023]
Moreover, the arrangement structure of the temperature controller is shown in FIG. 7A and 7B, 12 is a PLC substrate, 20 is a heat equalizing plate, and 21 is a temperature controller. In the structure of FIG. 7A, the temperature controller 21 is in direct contact with the PLC substrate. For this reason, in the structure of FIG. 7A, the time constant of the temperature control can be shortened, and the sudden change of the environmental temperature can be followed. In the structure of FIG. 7B, the temperature controller 21 is in contact via the soaking plate 20. For this reason, in the structure of FIG. 7B, the gradient of the temperature distribution becomes relatively gentle, and the temperature control of the large-sized PLC substrate is also possible.
[0024]
(Embodiment 2)
In the AWG, even if only the arrayed waveguide is disposed along the isotherm, it is effective in improving the wavelength characteristics of the optical waveguide circuit. FIG. 8 is a diagram in which only the arrayed waveguide is arranged along the isotherm. In FIG. 8, 11 is an isotherm, 12 is a PLC substrate, 13 is an arrayed waveguide, 14 is a slab waveguide, and 15 is an input / output waveguide. As shown in FIG. 8, depending on the type of AWG, there is a circuit in which the slab waveguide 14 is larger than the arrayed waveguide 13. In that case, it may be difficult to arrange all of the arrayed waveguide 13 and the two slab waveguides 14 along the isotherm. Therefore, even if the temperature controller and the waveguide type optical circuit are arranged so that only the arrayed waveguide 13 is along the isotherm as in the present embodiment, there is an effect of preventing fluctuations in wavelength characteristics.
[0025]
The AWG interferometer includes a slab waveguide that splits light and an arrayed waveguide that gives an optical path length difference to each of the divided lights. Among these, the arrayed waveguide is particularly sensitive to temperature, and the wavelength variation of the interference wavelength is caused by the temperature distribution difference of the optical path length between the adjacent waveguides (waveguide length × effective refractive index). Therefore, when the entire interferometer cannot be placed in the isotherm due to the shape of the interferometer, it is effective to place the arrayed waveguide portion in the isotherm.
[0026]
(Embodiment 3)
The AWG is designed so that a specific wavelength (design center wavelength) is output from the center output port when the PLC substrate is set to the design temperature. However, even if the temperature is set to the design temperature with the temperature controller, the wavelength of the output light from the center output port is different from the design center wavelength due to the temperature distribution of the arrayed waveguide part in the actual operation. ) Occurs.
[0027]
FIG. 9 shows the results of measuring the temperature distribution difference (Δ ° C.) and the center wavelength error (pm) of the arrayed waveguide. As in the first embodiment, the temperature distribution was measured by actually measuring the temperature with a thermoviewer (JTG-7200, manufactured by JEOL Datum Co., Ltd.) and measuring the wavelength error at that time. As can be seen from FIG. 9, in order for the allowable range of the substantial center wavelength error to be within ± 10 pm, that is, within 20 pm, the temperature distribution difference of the arrayed waveguide needs to be within 2.4 ° C. Preferably, the temperature distribution difference is within 2.1 ° C. so that the allowable range of the central wavelength error is within 15 pm, and more preferably, the temperature distribution difference is within 1.5 ° C. where the allowable range of the central wavelength error is within 10 pm. is there.
[0028]
(Embodiment 4)
In order to reduce the size of the apparatus, two AWGs may be formed on the same substrate. An example in which two AWGs are formed on the same substrate is shown in FIG. 11 is an isotherm, 12 is a PLC substrate, 13 is an arrayed waveguide, 15 is an input / output waveguide, and 16 is a slab waveguide. Such an arrangement is particularly effective in the case of configuring a transmission / reception integrated optical multiplexer / demultiplexer in which one of the AWGs is a multiplexer and the other is a duplexer. In this case, two AWGs are operated simultaneously. Since the two AWGs are operated simultaneously, they are designed to operate at the same temperature.
In the present embodiment, the arrayed waveguides 13 on the two opposing semicircular arcs are respectively arranged along the isotherm, and the central wavelength error of the AWG can be reduced.
[0029]
(Embodiment 5)
The present invention can also be applied to MZ. FIG. 11 shows an MZ interferometer to which the present invention is applied. In FIG. 11, 11 is an isotherm, 12 is a PLC substrate, 31 and 32 are arm waveguides, and 33 is a directional coupler. As in the first embodiment, a temperature controller is disposed on the back surface of the PLC substrate, and in this embodiment, the Peltier element is installed so as to be in direct contact with the PLC substrate 12. An isotherm formed by the temperature adjuster is grasped by a thermoviewer, and the two directional couplers 33 and the two arm waveguides 31 and 32 connecting the two directional couplers 33 are adjusted in temperature. It was arranged along the isotherm 11 formed by the vessel. As can be seen from FIG. 11, in the MZ, the lengths of the two arm waveguides 31 and 32 are asymmetrical, so that the Peltier element on the back surface is heated or cooled between the two arm waveguides 31 and 32. The center of was located.
[0030]
As a result, as described in FIG. 2, in the conventional MZ, the isotherm crosses the arm waveguide, and it is difficult to control the temperature as designed using the temperature sensor. By adopting an arrangement structure using lines, the arm waveguide and the directional coupler can be easily set within the design temperature, and the wavelength characteristic error is eliminated.
[0031]
In MZ, even if the two arm waveguides 31 and 32 are arranged along the isotherm 11, fluctuations in wavelength characteristics to some extent can be prevented. However, if the directional coupler 33 is arranged on an isotherm different from the two arm waveguides 31 and 32, the branching ratio is deviated from 50% due to the temperature distribution difference of the directional coupler 33 and the variation from the set temperature. The amplitude of the cross side output and the through side output of the directional coupler is unbalanced. Therefore, by arranging the MZ directional coupler along the isotherm, it is possible to obtain an MZ having excellent wavelength accuracy as well as wavelength accuracy.
[0032]
The present invention is not limited to the AWG or MZ described above, and can be widely applied to an optical waveguide module having an interferometer and controlling the absolute amount of the optical path length difference with temperature. Other examples of the waveguide type optical circuit include a waveguide grating that forms a refractive index change in the waveguide. In the above-mentioned AWG and MZ, the interferometer portion is formed in a wide region, so that it is easily affected by the temperature distribution. Therefore, the effect of the present invention in which the interferometer portion is within a certain temperature range is particularly great.
[0033]
【The invention's effect】
As described above, according to the present invention, the waveguide type optical circuit is kept within the design temperature by arranging the interferometer of the waveguide type optical circuit or a part of the interferometer along the isotherm. Can now. As a result, fluctuations in the wavelength characteristics of PLCs such as AWG and MZ can be suppressed.
[Brief description of the drawings]
FIG. 1 is a diagram illustrating a structure of an AWG according to a conventional arrangement.
FIG. 2 is a diagram illustrating the structure of an MZ according to a conventional arrangement.
FIG. 3 is a diagram for explaining an arrangement structure of AWGs arranged along an isotherm according to the present invention.
FIG. 4 is a diagram illustrating the structure of a temperature controller and a soaking plate applied to the present invention.
FIG. 5 is a diagram for explaining the arrangement of a soaking plate and a temperature controller applied to the present invention.
FIG. 6 is a view for explaining the arrangement of a soaking plate and a temperature controller applied to the present invention.
FIG. 7 is a diagram for explaining another arrangement of a heat equalizing plate and a temperature controller applied to the present invention.
FIG. 8 is a diagram illustrating an AWG arrangement structure in which an arrayed waveguide is arranged along an isotherm according to the present invention.
FIG. 9 is a diagram for explaining the results of measuring the temperature distribution difference (Δ ° C.) and the center wavelength variation (pm) of the arrayed waveguide;
FIG. 10 is a diagram for explaining an arrangement structure of AWGs arranged along an isotherm according to the present invention.
FIG. 11 is a diagram for explaining an arrangement structure of MZs arranged along an isotherm according to the present invention.
[Explanation of symbols]
11: isotherm 12: planar lightwave circuit (PLC) substrate 13: array waveguide 14: slab waveguide 15: input / output waveguide 16: slab waveguide 20: heat equalizing plate 21: temperature controller 22: Temperature sensor 31, 32: Arm waveguide 33: Directional coupler

Claims (10)

An optical waveguide module comprising: a waveguide type optical circuit including an interferometer configured on a substrate; and a temperature adjuster for adjusting a temperature disposed on a back surface of the substrate. An optical waveguide module, wherein the entire optical delay portion disposed near the back surface of a corresponding portion and providing an optical path length difference of the interferometer is disposed along an isothermal line formed by the temperature controller.   An optical waveguide module comprising: a waveguide-type optical circuit including an arrayed waveguide configured on a substrate and two slab waveguides; and a temperature controller that adjusts a temperature disposed on a back surface of the substrate. An optical waveguide module, wherein a temperature controller is disposed near a back surface of a corresponding portion of the arrayed waveguide, and the arrayed waveguide is disposed along an isothermal line formed by the temperature controller.   An optical waveguide module comprising: a waveguide-type optical circuit including an arrayed waveguide configured on a substrate and two slab waveguides; and a temperature controller that adjusts a temperature disposed on a back surface of the substrate. A temperature controller is disposed near the back surface of a corresponding portion of the waveguide type optical circuit, and the arrayed waveguide and the two slab waveguides are disposed along an isothermal line formed by the temperature controller. An optical waveguide module characterized by that. A waveguide-type optical circuit including two directional couplers formed on a substrate and two arm waveguides connecting the two directional couplers; and a temperature disposed on a back surface of the substrate. An optical waveguide module having a temperature controller to be adjusted, wherein the temperature controller is disposed near a back surface of the waveguide optical circuit, and connects the two directional couplers and the two directional couplers. The optical waveguide module, wherein the two arm waveguides are arranged on a substantially isotherm formed by the temperature controller. A waveguide-type optical circuit including two directional couplers formed on a substrate and two arm waveguides connecting the two directional couplers; and a temperature disposed on a back surface of the substrate. An optical waveguide module having a temperature controller to be adjusted, wherein the temperature controller is disposed near a back surface of the waveguide optical circuit, and the two arm waveguides connecting the two directional couplers are provided. An optical waveguide module arranged along an isotherm formed by the temperature controller. A waveguide-type optical circuit including an interferometer configured on a substrate;
In the optical waveguide module having one temperature controller for adjusting the temperature disposed on the back surface of the substrate,
The temperature controller is disposed near the back surface of a corresponding portion of the interferometer, and surrounds the highest temperature point or the lowest temperature point of the temperature distribution on the substrate surface formed by the temperature controller, and the temperature controller. An optical waveguide module in which an entire optical delay portion for providing a difference in optical path length of the interferometer is disposed along an isothermal line formed by the above. A waveguide-type optical circuit including an arrayed waveguide and two slab waveguides configured on a substrate;
In the optical waveguide module having one temperature controller for adjusting the temperature disposed on the back surface of the substrate,
The temperature adjuster is disposed near the back surface of a corresponding portion of the arrayed waveguide, and surrounds the highest temperature point or the lowest temperature point of the temperature distribution on the substrate surface formed by the temperature adjuster, and the temperature adjustment. An optical waveguide module, wherein the arrayed waveguide is disposed along an isotherm formed by a vessel. A waveguide-type optical circuit including an arrayed waveguide and two slab waveguides configured on a substrate;
In the optical waveguide module having one temperature controller for adjusting the temperature disposed on the back surface of the substrate,
The temperature controller is disposed near the back surface of a corresponding portion of the waveguide optical circuit, and surrounds the highest temperature point or the lowest temperature point of the temperature distribution on the substrate surface formed by the temperature controller, and An optical waveguide module, wherein the arrayed waveguide and the two slab waveguides are arranged along an isotherm formed by a temperature controller. A waveguide-type optical circuit including two directional couplers formed on a substrate and two arm waveguides connecting the two directional couplers;
In the optical waveguide module having one temperature controller for adjusting the temperature disposed on the back surface of the substrate,
The temperature controller is disposed near the back surface of the waveguide type optical circuit, and the maximum temperature point or the minimum temperature point of the temperature distribution on the substrate surface formed by the temperature controller is surrounded by the two arm waveguides. The two directional couplers and the two arm waveguides connecting the two directional couplers are arranged so as to be along the isotherm formed by the temperature controller. An optical waveguide module. In the optical waveguide module according to claim 1 to 9, a waveguide type optical circuit which is arranged along the isotherm, 2.4 ° C. within, preferably within 2.1 ° C., more preferably within 1.5 ° C. An optical waveguide module arranged in a temperature bandwidth of

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