JP5086208B2 - Tunable filter and optical signal monitor using the same - Google Patents

Description

  The present invention is a wavelength tunable filter mainly used for optical fiber communication and an optical signal monitor using the same. More specifically, the present invention relates to a wavelength tunable filter used in a WDM system that handles a plurality of optical wavelength signals and an optical signal monitor using the same.

  With an increase in communication capacity in recent years, an optical transmission system (WDM system) using wavelength division multiplexing (WDM) technology has been widely introduced from the backbone to the metro area. The WDM system includes optical components such as an optical wavelength multiplexer / demultiplexer and an optical switch in order to handle optical signals having a plurality of wavelengths. These optical components have been put into practical use based on various operating principles. Among them, optical components using a quartz-based planar lightwave circuit (PLC) have a high degree of freedom in optical circuit design and excellent reliability. Therefore, it is currently attracting attention as the most powerful optical component. An optical component such as an optical wavelength multiplexer / demultiplexer or an optical switch using such a PLC is an optical interference circuit composed of a plurality of waveguides composed of a core and a clad formed on a substrate.

  Here, as an example of an optical interference circuit using a PLC, an array waveguide diffraction grating type optical multiplexer / demultiplexer (AWG) functioning as an optical wavelength multiplexer / demultiplexer will be described as an example.

  FIG. 1 shows an arrayed waveguide grating optical multiplexer / demultiplexer (AWG) 10 which is an example of a conventional optical interference circuit. The AWG 10 includes a first slab waveguide 12, an arrayed waveguide 13 composed of a plurality of channel waveguides having different lengths by a predetermined length, and a second slab waveguide 14. . The first slab waveguide 12 has one or a plurality of input waveguides 11 (shown here as one), while the second slab waveguide 14 has a plurality of output waveguides 15. It is connected. As shown in FIG. 4, these waveguides are usually composed of a core 2 made of quartz and a clad 3 on a silicon substrate 1. In the AWG 10, when a WDM signal having a plurality of wavelengths combined is input to the input waveguide 11, the input optical signal can be demultiplexed and extracted from each port from the output waveguide 15 (Non-Patent Document 1). reference).

  The AWG described above is also used as a component of an optical signal monitor for monitoring the optical power of each wavelength signal in a WDM system. Specifically, as shown in FIG. 2, by directly mounting a photodiode (PD) 501 as a light receiving element on the end face of each output waveguide 15 of the AWG 10, it is possible to monitor the optical signal power of each wavelength. An optical channel monitor (OCM) has been put into practical use (see Non-Patent Document 2). The PD 501 shown here is an example using a chip scale package type PD array (CSP type PD array) 500 hermetically sealed in a housing 502 and a glass window 503 (see Non-Patent Document 3). ). The light receiving surface of each PD 501 built in the CSP type PD array 500 is optically coupled to each port of the output waveguide 15 of the AWG 10.

Japanese Patent No. 3436937 Japanese Patent No. 3498650 Takahashi et al., “Array waveguide diffraction grating for WDM”, NTT R & D, Vol. 46, no. 7, pp. 685-692, 1997 Oyama et al., “40-ch optical power channel monitor module using AWG and CSP type PD array”, 2006 IEICE Electronics Society Conference Proceedings 1, C-3-78, pp. 200 Doi et al., “Development of Chip Scale Package Type PD Array (CSP-PD)”, IEICE Technical Report EMD2007-36, CPM2007-57, OPE2007-74, LQE2007-3, (2007-08), pp. 39-44 S. Kamei et al., “Recent progress on athermal AWG wavelength multiplexer,” Proc. Of SPIE, Vol. 6014, 60140H, 2005

  One method for increasing the capacity of a WDM system is to narrow the frequency interval between adjacent channels. However, the narrower the frequency interval, the stricter the wavelength accuracy required in the system. Therefore, when an optical signal monitor used in a WDM system is taken as an example, it is required to implement a function for detecting not only optical power but also wavelength information.

  However, the optical signal monitor using the AWG according to the prior art described above has a problem that only the optical power of the demultiplexed optical signal can be detected. If the transmission wavelength characteristics of the AWG can be made variable, the wavelength information can be detected.

  Further, in the conventional AWG, the transmission characteristics greatly vary with respect to the environmental temperature. This is because there is a temperature change in the refractive index of the waveguide material constituting the AWG. Therefore, it is necessary to implement a mechanism that keeps the temperature of the AWG constant, or to make the AWG temperature independent from the environmental temperature. In particular, the latter temperature independence is indispensable for demanding power saving and space saving in recent WDM systems.

  In general, a temperature independence condition in which an optical interference circuit composed of i types of waveguide materials does not change its optical characteristics with respect to environmental temperature is expressed by the following equation (1).

Here, n _i is the effective refractive index of the i-th waveguide material, [Delta] L _i is the optical path length difference between adjacent optical interferometer, T is representative of the temperature, respectively. If the equation (1) is calculated and the term appearing in the linear expansion coefficient is negligibly small, the temperature-independent condition is

You may think.

  Here, a method for making AWG temperature independent will be described. The AWG shown in FIG. 3 shows a form in which the AWG of FIG. 1 is made temperature independent. FIG. 4 is a cross-sectional view taken along line A-A ′ of FIG. That is, in the configuration of FIG. 3, only the quartz is used as the waveguide material (first waveguide material), whereas the AWG of FIG. A waveguide material (second waveguide material) having a different optical path length temperature coefficient from that of quartz (first waveguide material). ) To achieve temperature independence of the optical properties of the AWG. Therefore, when formula (1) is specifically described,

However,

Should be satisfied. Here, α ₁ and α ₂ are the optical path length temperature coefficient of the first waveguide material and the optical path length temperature coefficient of the second waveguide material, respectively, and n ₁ and n ₂ are respectively based on the first waveguide material. The effective refractive index and the effective refractive index of the second waveguide material, and ΔL ₁ and ΔL ₂ are the path length difference in the adjacent optical interferometer formed of the first waveguide material and the second waveguide, respectively. It is the path length difference between adjacent optical interferometers (here, arrayed waveguides) due to the waveguide material.

Usually, the optical path length temperature coefficient α ₁ of quartz as the first waveguide material is + 1.1 × 10 ⁻⁵ [1 / ° C.]. As the optical resin 21, silicone resin, epoxy resin, polyimide, PMMA, or the like is used. Here, a silicone resin having an optical path length temperature coefficient α ₂ of −37 × 10 ⁻⁵ [1 / ° C.] is used as the second resin. (See Patent Document 1).

In the AWG, L ₁ ′ is set between adjacent waveguides among the arrayed waveguides constituting the optical interferometer, and the length of the second waveguide material formed in one waveguide between the adjacent waveguides. L ₂ ′ is the total length of the second waveguide material in the other waveguides among the adjacent waveguides, and L ₁ is L in this one waveguide. Let ₁ ′ be the length composed of the first waveguide material except for ₁ ′, and let L ₂ be the length composed of the first waveguide material except for L ₂ ′ in the other waveguides, From equation (11)

Thus, if designed so as to satisfy this, a temperature-independent AWG can be obtained.

  Moreover, in order to reduce the radiation loss by a groove | channel, the groove | channel is normally divided | segmented into several and formed (refer nonpatent literature 4). The groove 20 is usually formed by a fine processing technique using photolithography and RIE. Further, the place where the groove 20 is formed and filled with the optical resin 21 may be the first slab waveguide 12 as shown in FIG. 5 in addition to the arrayed waveguide described here. As shown, the second slab waveguide 14 may be used, and the position is not particularly limited as long as the entire optical interference circuit constituting the AWG satisfies Expression (1). When the groove for filling the optical resin 21 in the slab waveguide is formed, the light emitted from the input waveguide propagates near the center of the slab waveguide and passes through the groove filled with the optical resin. The refraction angle differs from the refraction angle when propagating through a portion away from the center of the slab waveguide and passing through the groove filled with the optical resin, resulting in aberration, and as a result, transmission of the AWG. Degrading properties. Therefore, the shape of the groove formed in the slab waveguide is such that the traveling direction of light propagating through the slab waveguide is curved so that the refraction angle of light is always uniform in the groove. Since it is possible to cancel the change in the equiphase plane of the light of each wavelength that occurs with the temperature change, it is possible to obtain optimized transmission characteristics of the AWG (see Patent Document 2).

  The above is the method for making AWG temperature independent. However, in these forms, it is only achieved that the optical characteristics are made temperature-independent with respect to the environmental temperature, and it is clear that the transmission wavelength characteristics of the AWG cannot be changed.

  The present invention has been made in view of the problems that have arisen in the prior art. The object of the present invention is to construct an optical interference circuit with variable transmission characteristics, for example, and to be temperature independent with respect to the environmental temperature. An object of the present invention is to provide a wavelength tunable filter that achieves

  Further, the present invention is not limited to the optical interference circuit constituting the AWG. For example, the transmission characteristics of various wavelength filters such as a Mach-Zehnder interferometer and a ring resonator can be changed and the ambient temperature can be changed. An object of the present invention is to provide a tunable filter that achieves temperature independence.

  Furthermore, by applying the wavelength tunable filter according to the present invention, in addition to detecting the optical power of the measurement light, it is compact and mounted with a function for detecting the wavelength and the optical signal intensity ratio (OSNR), and with respect to the ambient temperature An object of the present invention is to provide an optical signal monitor that achieves temperature independence.

In order to achieve such an object, the invention described in claim 1 is a wavelength tunable filter that demultiplexes input wavelength multiplexed light and outputs a plurality of lights having different wavelengths. a multiple channel waveguides having a of, arrayed wave composed of a plurality of channel waveguides for demultiplexing the multi-wavelength light by a change due to the wavelength of the phase difference occurring between said plurality of channel waveguides A waveguide diffraction grating, an input-side slab waveguide disposed between the arrayed waveguide diffraction grating and the input channel waveguide, and between the arrayed waveguide diffraction grating and the output channel waveguide. The slab waveguide on the output side is arranged so as to intersect the traveling direction of the light. Channel waveguide And materials to cancel the variation due to temperature of the phase difference occurring between the path leading to the slab waveguide of the output side Te, and a mechanism for heating or cooling the material, said one of the waveguides is also an upper cladding, the core And the slab waveguide on the input side or the output side is a plurality of grooves formed in a curved shape so as to intersect the traveling direction of light , and a plurality of slab waveguides filled with the material. The plurality of grooves are formed by removing the upper cladding and the core from the input side or output side slab waveguide, or the input side or output side slab waveguide. The upper clad, the core and the lower clad are removed from the material, and the material has an effective refractive index of the slab waveguide having the plurality of grooves. Materials der having a degree coefficient different refractive index temperature coefficient is, the plurality of grooves are grouped, the mechanism is characterized in that heating or cooling independently the material for each group.

The invention described in 請 Motomeko 2, in the wavelength tunable filter for outputting a plurality of light having different wavelengths wavelength division multiplexed light inputted to demultiplexing, multiple channels having different lengths by a predetermined length An arrayed waveguide diffraction grating comprising a plurality of channel waveguides for demultiplexing the wavelength-multiplexed light by a change in wavelength of a phase difference generated between the plurality of channel waveguides , and the arrayed waveguide An input-side slab waveguide disposed between the diffraction grating and the input channel waveguide, and an output-side slab waveguide disposed between the arrayed waveguide grating and the output channel waveguide Each of the waveguides is disposed so as to intersect the traveling direction of the light, cancels the change of the phase difference with respect to the light of each wavelength due to the temperature, and a mechanism for heating or cooling the material. , Top Rudd, core, and is composed of a lower cladding, the array waveguide diffraction grating is a plurality of grooves formed so as to intersect span before SL plurality of channel waveguides, a plurality filled by the material has a groove, the plurality of grooves, the upper cladding from said plurality of or is formed by a channel waveguide removing the upper cladding and the core, or the plurality of channel waveguides, said core and wherein is formed by removing the lower cladding, said material, Ri materials der having a temperature coefficient different from the refractive index temperature coefficient of the effective refractive index of said plurality of channel waveguides, the plurality of grooves are grouped, The mechanism is characterized in that the material is heated or cooled independently for each group .

According to a third aspect of the present invention, in the wavelength tunable filter that demultiplexes the input wavelength division multiplexed light and outputs a plurality of lights having different wavelengths, a plurality of channel guides having different lengths by a predetermined length are provided. An arrayed waveguide diffraction grating comprising a plurality of channel waveguides for demultiplexing the wavelength-multiplexed light by a change in wavelength of a phase difference generated between the plurality of channel waveguides, and the arrayed waveguide diffraction An input-side slab waveguide disposed between the grating and the input channel waveguide; and an output-side slab waveguide disposed between the arrayed waveguide diffraction grating and the output channel waveguide; The slab on the output side is arranged so as to cross the traveling direction of the light, and is input to each wavelength of light from the slab waveguide on the input side through the plurality of channel waveguides of the arrayed waveguide diffraction grating. Waveguide And a mechanism for heating or cooling the material, and each of the waveguides includes an upper clad, a core, and a lower clad. The slab waveguide on the input side or the output side has a plurality of grooves formed in a curved shape so as to intersect the traveling direction of light, and has a plurality of grooves filled with the material. Are formed by removing the upper cladding and the core from the input or output slab waveguide, or from the input or output slab waveguide to the upper cladding, the core, and the core. Formed by removing the lower cladding, the material has a refractive index temperature different from the temperature coefficient of the effective refractive index of the slab waveguide having the plurality of grooves. The plurality of grooves are grouped into a first groove group and a second groove group, and the first groove group does not change its optical characteristics with respect to the environmental temperature. The second groove group has a number of second grooves that do not satisfy the temperature-independence condition that is no longer satisfied by the first groove group. And the first groove is configured such that the width in the optical axis direction becomes narrower from the larger optical path length difference toward the smaller optical path length, and the second groove starts from the larger optical path length difference. The width of the optical axis direction increases toward the smaller side, and the mechanism heats or cools only the material filled in the first groove.
According to a fourth aspect of the present invention, in the wavelength tunable filter that demultiplexes the input wavelength division multiplexed light and outputs a plurality of lights having different wavelengths, a plurality of channel guides having different lengths by a predetermined length are provided. An arrayed waveguide diffraction grating comprising a plurality of channel waveguides for demultiplexing the wavelength-multiplexed light by a change in wavelength of a phase difference generated between the plurality of channel waveguides, and the arrayed waveguide diffraction An input-side slab waveguide disposed between the grating and the input channel waveguide; and an output-side slab waveguide disposed between the arrayed waveguide diffraction grating and the output channel waveguide; Each of the waveguides includes a material that is arranged so as to intersect the traveling direction of the light, cancels the change of the phase difference due to the temperature of the light of each wavelength, and a mechanism that heats or cools the material. The arrayed waveguide diffraction grating is composed of an upper clad, a core, and a lower clad, and the arrayed waveguide diffraction grating is a plurality of grooves formed so as to cross over the plurality of channel waveguides and filled with the material And the plurality of grooves are formed by removing the upper cladding and the core from the plurality of channel waveguides, or the upper cladding, the core, and the core from the plurality of channel waveguides. The lower cladding is formed by removing the material, and the material is a material having a refractive index temperature coefficient different from a temperature coefficient of an effective refractive index of the plurality of channel waveguides, and the plurality of grooves are first grooves. Group and a second groove group. The first groove group has a temperature independence condition that does not change its optical characteristics with respect to the environmental temperature. And the second groove group has as many second grooves as there are conditions satisfying the temperature independence that are no longer satisfied by the first groove group. The first groove is configured such that the width in the optical axis direction becomes narrower from the larger optical path length difference toward the smaller optical path length, and the second groove is smaller from the larger optical path length difference. The width of the optical axis direction increases toward the surface, and the mechanism heats or cools only the material filled in the first groove.

請 Motomeko invention described in 5, the wavelength tunable filter for outputting a plurality of light having different wavelengths wavelength division multiplexed light input demultiplexed plurality of channel waveguides having different lengths by a predetermined length A plurality of channel waveguides for demultiplexing the wavelength-multiplexed light due to a change in wavelength due to a phase difference generated between the plurality of channel waveguides, and arranged so as to intersect with the traveling direction of the light. A material that cancels a change in temperature of the phase difference with respect to light; and a mechanism that heats or cools the material. The plurality of channel waveguides include an upper clad, a core, and a lower clad, and N + 1 (N is an integer of 1 or more) N sets of arm waveguides sandwiched between adjacent optical couplers, and each of the N sets of arm waveguides has a first optical path length different from each other. Ah It consists of the waveguide and the second arm waveguide, wherein the first arm waveguide is first groove and the second groove portion is formed, the second arm waveguide, the second third groove is formed groove with the same optical path length of said first groove, the second groove portion and the third groove portion, said first arm waveguide and the second arm waveguide Or by removing the upper cladding, the core, and the lower cladding from the first arm waveguide and the second arm waveguide. is formed, said first groove, wherein the second groove portion and the third groove portion, the refractive index different from the first arm waveguide and the temperature coefficient of the effective refractive index of the second arm waveguide same said material having a temperature coefficient of charge Is, the first groove portion and a second of said material filled in the groove is characterized by being heated or cooled by a common said mechanism.

According to a sixth aspect of the present invention, there is provided an optical signal monitor comprising one or a plurality of photodiodes in the output part of the wavelength tunable filter according to any of the third to fifth aspects.

  According to the present invention, it is possible to realize a wavelength tunable filter while locally heating the temperature-independent optical interference circuit and maintaining the temperature-independent condition. Furthermore, OSNR and peak wavelength can be monitored by providing a PD in the output unit.

(First embodiment)
FIG. 7 shows a first embodiment. FIG. 8 is a cross-sectional view taken along the line BB ′ of FIG. In the present embodiment, as shown in FIG. 5, the AWG that is made temperature-independent with respect to the environmental temperature in the form in which the groove 20 is formed in the first slab waveguide 12 and the groove 20 is filled with the optical resin 21. Take up and explain.

The present embodiment is characterized in that a heater 30 for locally heating the optical resin 21 is mounted. The heater 30 shown in the drawing shows an approximate outer shape, and may actually be an external heater that can locally heat the optical resin. Further, an electrical wiring 40 for applying electric power is taken out from the heater 30.
At this time, in order to make the AWG temperature-independent, the groove 20 is formed in the first slab waveguide 12 and the optical resin 21 is filled, but the groove 20 and the optical resin 21 have the formulas described above. If the optical interference circuit constituting the AWG is designed so as to satisfy (1), the temperature can be made independent.

  Therefore, it is sufficient to satisfy Expression (2) that specifically describes Expression (1). That is, in this embodiment,

However,

Should be satisfied. Here, α ₁ and α ₂ are the optical path length temperature coefficient of the first waveguide material and the optical path length temperature coefficient of the second waveguide material, respectively, and n ₁ and n ₂ are respectively based on the first waveguide material. The effective refractive index and the effective refractive index of the second waveguide material, and ΔL ₁ and ΔL ₂ are the path length difference in the adjacent optical interferometer formed of the first waveguide material and the second waveguide, respectively. It is a path length difference between adjacent optical interferometers (here, the first slab waveguide 12) due to the waveguide material. Further, dn ₁ / dT and dn ₂ / dT are called refractive index temperature coefficients.

Usually, since the first waveguide material is quartz, the optical path length temperature coefficient α ₁ is + 1.1 × 10 ⁻⁵ [1 / ° C.]. Here, a silicone resin having an optical path length temperature coefficient α ₂ of −37 × 10 ⁻⁵ [1 / ° C.] was used as the second waveguide material.

Here, in the AWG, L ₁ ′ is set between the adjacent waveguides of the arrayed waveguides constituting the optical interferometer, the waveguide path formed by the input slab waveguide, and the output slab waveguide. In one waveguide path of the waveguide paths, the total length of the slab waveguide made of the second waveguide material is set, and L ₂ ′ is the other waveguide in the adjacent waveguide paths. In the path, the sum of the lengths made of the second waveguide material in the slab waveguide is set, and L ₁ is made of the first waveguide material except for L ₁ ′ in the _one waveguide path. If L ₂ is the length formed of the first waveguide material except for L ₂ ′ in the other waveguide,

Thus, if designed so as to satisfy this, a temperature-independent AWG can be obtained.

  In order to reduce the radiation loss due to the groove 20, the groove 20 is usually divided into a plurality of parts. Furthermore, in order to cancel the change of the equiphase surface of the light of each wavelength caused by the environmental temperature change, the shape of the groove formed in the slab waveguide is such that the traveling direction of the light propagating through the slab waveguide is The grooves are arranged in a curved shape so that the light refraction angle is always uniform.

  Actually, an AWG was produced as follows. A quartz optical waveguide composed of a core and a clad with a relative refractive index difference of 1.5% was formed on a silicon substrate by PLC technology. The size of the core is 4.5 μm × 4.5 μm. Then, the groove | channel filled with optical resin was processed by RIE. The width of the groove was formed to be curved while changing from 7 μm to 60 μm. The number of grooves is divided into six, and the interval between the grooves is constant at 40 μm. Here, the depth of the groove was etched to a position deeper than the core.

  Now, when electric power is applied to the heater 30, the optical resin 21 is locally heated and its refractive index changes. Since the absolute value of the optical path length temperature coefficient of the optical resin 21 is larger than that of the waveguide made of quartz, the optical path length in the optical resin 20 portion is changed by heating, and as a result, the second slab waveguide 14 of the AWG 10 changes. The condensing position for each wavelength changes on the condensing surface. This means that the transmission wavelength characteristic of the AWG can be made variable. As described above, according to the present embodiment, in the AWG 10 that is made temperature-independent with respect to the conventional environmental temperature, the heater 30 is simply attached to the region filled with the optical resin 21, and the temperature does not depend on the environmental temperature. In addition, an AWG having a variable transmission wavelength can be realized.

  FIG. 9 shows transmission wavelength characteristics with respect to applied power of an AWG 201 manufactured by mounting a ceramic heater as the heater 30 on the AWG 10 with a channel frequency interval of 100 GHz on the groove 20 filled with the optical resin 21. It can be seen that the transmission wavelength characteristic of the AWG 201 is variable without being deformed in proportion to the applied power. Since the applied power on the horizontal axis can be associated with the wavelength, that is, the transmission wavelength of the AWG can be easily made variable simply by providing the AWG 10 with means for locally heating the optical resin 21. In this example, the transmission wavelength variable efficiency with respect to the applied power was about 5 [GHz / W]. This can be further improved by optimizing the shape of the heater 30 and its mounting form.

  Thus, since the transmission wavelength characteristic corresponds to the applied power to the heater 30, the heater 30 of the AWG 201 is swept to the incident light, and the applied power that maximizes the optical power output at that time is obtained. The wavelength can be detected. In addition, the OSNR is detected by taking the optical signal light in a wider range than the wavelength component of the optical signal while making the heater of this AWG201 sweep drive, and taking the minimum and maximum ratio of the optical power output at that time. It becomes possible to do. This is also true for the embodiments described below.

  The operation that enables wavelength detection or OSNR detection in this way is temperature-independent with respect to the environmental temperature, and therefore has a feature that calibration with respect to the environmental temperature is not required unlike the prior art. This is also true for the embodiments described below.

  It should be noted that the transmission wavelength variable range may be a range that can be swept with an applied power that has a variable range equal to or less than the channel frequency interval of the WDM system. This is because the AWG can simultaneously output optical signals of respective channel frequencies (wavelengths) for each output waveguide. This is characterized in that the reading speed can be increased as compared with the method of sweeping the variable filter over the entire wavelength range on the system.

  In the present embodiment, an example in which a ceramic heater is used as the heater 30 is shown, but it goes without saying that the type is not selected as long as mounting is possible with a mechanism capable of locally heating. For example, a Peltier element, a sheet heater, a resistance heating element, or the like may be used. Conversely, a mechanism capable of locally cooling may be implemented. If possible, it is desirable to use a small heating mechanism or cooling mechanism that maximizes the variable filter characteristics with respect to the applied power.

  In order to further increase the efficiency of the variable characteristic of the transmission wavelength with respect to the applied power, a second waveguide material (this book) that is replaced in the first waveguide material (quartz in this embodiment) and locally heated or cooled. In the embodiment, the absolute value of the optical path length temperature coefficient of silicone resin) is preferably larger than that of the first waveguide material. Further, the place where the second waveguide material is heated or cooled may be a part of the second waveguide material or the entire second waveguide material. This is also true for the embodiments described below.

  In addition, as a material for canceling the change of the equiphase surface of the light of each wavelength caused by the temperature change, and as a constituent material for filling the groove, various optical resins such as silicone resin, epoxy resin, polymetal methacrylate resin, Alternatively, multi-component glass materials containing sodium, potassium, and calcium are used. On the other hand, many of the component materials of channel waveguides that constitute input / output slab waveguides, input / output channel waveguides, and arrayed waveguide diffraction gratings are used. In this case, a quartz material is used.

  In the present embodiment, the example in which the heater 30 for locally heating the optical resin 21 filled in the groove 20 formed in the first slab waveguide 12 is mounted has been described. As long as it is designed so as to satisfy the temperature independence condition shown in Expression (1), a groove 20 is formed in the second slab waveguide 14 as shown in FIG. A heater 31 for locally heating the resin 21 may be mounted, or, as shown in FIG. 11, the groove 20 is formed in the arrayed waveguide 13 and the filled optical resin 21 is locally disposed. A heater 30 for heating may be mounted, or, as shown in FIG. 12, grooves 20 are formed and filled in both the first slab waveguide 14 and the second slab waveguide. Heater for locally heating the optical resin 21 0 may be implemented, it is needless to say that can produce the same effect of the invention also in these cases. This is also true for the embodiments described below.

  Here, the shape of the groove will be described. In this example, the first waveguide material quartz has a positive optical path length temperature coefficient, while the second waveguide material silicone resin has a negative optical path length temperature coefficient, The absolute value of the optical path length temperature coefficient is larger in the second waveguide material. In this case, the groove width in the optical axis direction filled with the second waveguide material under the condition of temperature independence shown in Expression (1) is as follows, from the larger optical path length difference to the smaller one. It just means that the width becomes narrower. That is, the shape of the groove is not always the same as this, and the temperature independence condition shown in the equation (1) is satisfied depending on the first waveguide material and the second waveguide material used. It goes without saying that the shape of the groove derived in (1) changes. This is also true for the embodiments described below.

  Further, the depth of the groove may be etched beyond the lower surface of the core. This is also true for the embodiments described below.

  Also, here, the first waveguide material has a positive optical path length temperature coefficient, and the second waveguide material has a negative optical path length temperature coefficient. As described above in combination, the first waveguide material has a positive optical path length temperature coefficient, and the second waveguide material also has a positive optical path length temperature coefficient, if other materials are possible. Alternatively, a combination in which the first waveguide material has a negative optical path length temperature coefficient and the second waveguide material also has a negative optical path length temperature coefficient may be used. That is, it is only necessary to satisfy the temperature independence condition shown in Expression (1), and the sign of the optical path length temperature coefficient of each material is not selected if it can be realized. This is also true for the embodiments described below.

(Second embodiment)
FIG. 13 shows a second embodiment. FIG. 14 is a cross-sectional view taken along the line CC ′ of FIG. The difference from the first embodiment is that a thin film heater 32 is integrated as a heater 30 on the periphery of the groove 21 and on the clad 3 between the grooves 21 by a microfabrication process. By using the thin film heater 32, the mounting process of the external heater 30 performed in the first embodiment can be eliminated, and the increase in the thickness direction due to the heater mounting can be eliminated. Can be achieved. Examples of the material of the thin film heater 32 include chromium and titanium, but are not limited to these materials.

  The actually produced AWG is the same as in the first embodiment. Furthermore, the width of the heater integrated on the clad between the grooves was 20 μm.

  Also in the present embodiment, regarding the temperature independence with respect to the environmental temperature, the shape and refractive index of the groove 20 and the optical resin 21 are set using the above-described equation (1), and the optical interference circuit constituting the AWG 10 is changed. Just design.

  As described above, according to the present embodiment, in the conventional temperature-independent AWG, the heater can be integrated in the region filled with the optical resin by the microfabrication technique. The heater mounting process can be eliminated, and an AWG having a variable transmission wavelength can be easily manufactured.

  FIG. 15 shows a center transmission frequency characteristic with respect to applied power of an AWG produced by integrating the thin film heater 32 as the heater 30 on the AWG 10 designed with a channel frequency interval of 100 GHz. From this figure, it is understood that the variable efficiency of the transmission wavelength characteristic with respect to the applied power is about 10 [GHz / W]. Since the heater position can be integrated in the immediate vicinity of the groove 20 filled with the optical resin 21 by the fine processing technique, the transmission wavelength characteristic can be made variable with low power as compared with the first embodiment.

  FIG. 16 shows the result of actually measuring the center wavelength with respect to the environmental temperature using the applied power as a parameter. This figure shows the ambient temperature of 25 degrees as a reference by subtracting the fluctuation of the center wavelength due to power application. Thus, the center wavelength fluctuation within ± 0.025 nm is realized in the temperature range of −10 degrees to +70 degrees. This is sufficiently small for an AWG that is not temperature independent to cause a center wavelength variation of about 0.9 nm in the same temperature range. That is, it can be seen that temperature independence is realized.

  Further, as described in the first example, this embodiment may be realized in the second slab waveguide 14 or in the arrayed waveguide 13. This is also true for the embodiments described below.

  Furthermore, as a measure for improving the variable efficiency of the transmission wavelength characteristic with respect to the applied power while satisfying the temperature independence condition shown in Expression (1), the thin film heater 32 is integrated by increasing the number of divisions of the groove 20. By increasing the area that can be produced, further improvement can be achieved by densely localizing the heating area. This is also true for the embodiments described below.

  A connection pattern of the thin film heater 32 shown in FIG. 13 will be described. FIG. 17 shows the groove and thin film heater pattern extracted. Thus, a pattern in which the thin film heaters 32 are connected in parallel as shown in FIG. 17A may be used, or a pattern in which the thin film heaters 32 are connected in series as shown in FIG. Alternatively, as shown in FIG. 17C, a connection obtained by mixing parallel connection and series connection may be used, and the present invention is not limited to these. Further, the thin film heater does not always have to be arranged on the clad between the grooves, and may be arranged at intervals as needed. If possible, it is desirable to integrate the heaters in a pattern that maximizes the variable efficiency of the transmission wavelength characteristic with respect to the applied power. This is also true for the embodiments described below.

(Third embodiment)
FIG. 18 shows a third embodiment. FIG. 19 is a cross-sectional view taken along the line DD ′ of FIG. The difference from the second embodiment is that the thin film heater 32 is integrated on the bottom of the groove 20 by a microfabrication process. Heat generated from the thin film heater 32 in the second embodiment is conducted to the optical resin 21 filled in the groove 20 through the clad 3 once. On the other hand, according to the present embodiment, since the optical resin 21 is filled directly on the thin film heater 32, the heat generated from the thin film heater 32 is directly conducted to the optical resin 21. Therefore, the variable efficiency of the transmission wavelength characteristic with respect to the applied power can be increased as compared with the second embodiment. Furthermore, as a measure for improving the variable efficiency of the transmission wavelength characteristic with respect to the applied power while satisfying the temperature independence condition shown in Expression (1), the thin film heater 32 is integrated by increasing the number of divisions of the groove 20. By increasing the number of grooves 20 that can be made, further improvement can be achieved by densely localizing the heating region. If possible, a heater may also be integrated on the side wall of the groove 20.

(Fourth embodiment)
FIG. 20 shows a fourth embodiment. In the present embodiment, unlike the embodiments described above, the first slab waveguide 12 is characterized by the arrangement of the grooves 20 that fill the optical resin 21. That is, by enlarging the region of the groove 20 filled with the optical resin 21, the amount of change in the optical path length in the optical resin portion by heating can be made larger than that in the first embodiment, that is, the transmission wavelength characteristic with respect to the applied power. The variable efficiency can be increased. This region will be referred to as the first groove 121. In addition, the thin film heater 32 is integrated around the first groove 121 so as to perform local heating, and this is called a first heater 131. As a method for integrating the first heater 131, the heater 30 may be attached externally as described in the first embodiment, or the groove 20 as described in the second embodiment. The thin film heater 32 may be integrated on the periphery of the groove 20 and on the clad 3 between the groove 20 and the groove 20, or as described in the third embodiment, the thin film heater 32 is integrated on the bottom of the groove 20. There are no restrictions on its implementation. Here, it is until it demonstrates based on a 2nd Example as an example.

  Now, in order to make temperature independence with respect to the environmental temperature, if the groove region is simply enlarged, only the first groove 121 will deviate from the temperature-independent condition of Equation (1). Therefore, in order to realize temperature independence, it is only necessary to arrange a groove for filling the optical resin for satisfying the conditions for compensation. This compensation groove is referred to as a second groove portion 122.

  In this example, the first waveguide material quartz has a positive optical path length temperature coefficient, while the second waveguide material silicone resin has a negative optical path length temperature coefficient, The absolute value of the optical path length temperature coefficient is larger in the second waveguide material than in the first waveguide material. In this case, under the condition of temperature independence, the groove width in the optical axis direction filled with the second waveguide material is, in terms of shape, from the larger optical path length difference toward the smaller one. Although the width becomes narrower, it is assumed that the first groove 121 is formed with a groove width that is outside the temperature independence condition. Therefore, in terms of shape, a second groove portion having a shape opposite to that of the first groove portion 121 whose width in the optical axis direction becomes narrower from the larger optical path length difference toward the smaller one, that is, the path shape. The second groove portion 122 whose width in the optical axis direction becomes thicker from the larger length difference toward the smaller one may be arranged for the width to be compensated. Of course, the second groove 122 is also filled with the optical resin 21 filled in the first groove 121.

  In addition, the arrangement | positioning of the 1st groove part 121 and the 2nd groove part 122 can also be arrange | positioned variously. That is, as shown in FIG. 20, both the first groove part 121 and the second groove part 122 are arranged in the first slab waveguide 12, and the second groove part 122 is arranged on the input waveguide 11 side. Alternatively, both the first groove portion 121 and the second groove portion 122 may be disposed in the first slab waveguide 12 and the first groove portion may be disposed on the input waveguide 11 side. Further, both the first groove 121 and the second groove 122 may be disposed in the second slab waveguide 14 and the second groove 122 may be disposed on the output waveguide 15 side. Both the groove 121 and the second groove 122 may be disposed in the second slab waveguide 12 and the first groove may be disposed on the output waveguide 15 side. Further, the first groove 121 may be disposed in the first slab waveguide 12 and the second groove 122 may be disposed in the second slab waveguide 14. Conversely, the first groove 121 may be disposed. The second slab waveguide 14 may be disposed in the second slab waveguide 14, and the second groove 122 may be disposed in the first slab waveguide 12. Further, the first groove 121 and the second groove 122 may be arranged in the portion of the arrayed waveguide 13. Further, if possible in layout, the grooves 20 constituting the first groove 121 and the grooves 20 constituting the second groove 122 may be interwoven and arranged.

(Fifth embodiment)
FIG. 21 shows a fifth embodiment. The difference from the fourth embodiment is that the heater 32 is integrated not only in the vicinity of the first groove 121 but also in the vicinity of the second groove 122 so as to be locally heated. The heater disposed around the first groove 121 is referred to as a first heater 131, and the heater disposed around the second groove 122 is referred to as a second heater 132. However, the first heater 131 and the second heater 132 are provided with electrical wirings 40 and 41 that can apply power independently of each other. By arranging the second heater 132, the optical resin 21 filled in the second groove 122 also changes the optical path length in order to change the refractive index by heating. As a result, the second slab waveguide 14 of the AWG 10 is changed. The condensing position of each wavelength changes on the condensing surface. However, as described in the fifth embodiment, the second groove 122 is obtained by heating the optical resin 21 filled in the first groove 121 in a direction to compensate for the first groove 121. The second slab waveguide 14 acts in the direction opposite to the condensing direction of the condensing surface of the second slab waveguide 14. By applying this point, the first heater 131 is usually driven to make the transmission wavelength characteristic variable, and the second heater 132 is separately driven to increase the transmission wavelength characteristic variable speed. It becomes possible to control. That is, by driving the first heater 131 and the second heater 132 in relation to each other, the sweep speed of the wavelength tunable filter can be made variable, or high-speed tuning can be performed to an arbitrary transmission wavelength characteristic point. .

  Here, although the structural example which divided | segmented the groove | channel 20 was shown, it is not necessarily required to divide | segment. However, it is possible to reduce the radiation loss by dividing the groove, and the variable efficiency of the transmission wavelength characteristic can be increased by densely integrating the heaters locally. Moreover, if each groove | channel 20 which comprises a 1st groove part and each groove | channel 20 which comprises a 2nd groove part mount the mechanism which drives the 1st heater 131 and the 2nd heater 132 independently, Each groove pattern may be arranged alternately or in a plurality.

  The first heater 131 and the second heater 132 are arranged corresponding to the arrangement positions of the first groove 121 and the second groove 122 as described in the fourth embodiment. Needless to say. However, since the first heater 131 and the second heater 132 are driven independently, the first groove 121 and the second groove 122 are arranged separately from each other in order to reduce thermal interference between them. It is desirable that the first heater 131 is disposed in the first slab waveguide 12 and the second heater 132 is disposed in the second slab waveguide 14 so as to be able to do so. Alternatively, the second heater 132 may be disposed in the first slab waveguide 12 and the first heater 131 may be disposed in the second slab waveguide 14.

  Further, a plurality of grooves can be provided in the arrayed waveguide 13 to form a group, and a heater can be arranged for each group.

(Sixth embodiment)
FIG. 22 shows a sixth embodiment. This is a Mach-Zehnder optical interference circuit composed of a first optical coupler 60, a second optical coupler 61, and a first arm waveguide 62 and a second arm waveguide 63 that connect the two optical couplers. It is. In the present embodiment, an example in which the first and second optical couplers are configured by directional couplers is shown. Further, the length of the first arm waveguide is different from the length of the second arm waveguide, and the length of the first arm waveguide is longer than the length of the second arm waveguide. In the Mach-Zehnder optical interference circuit formed of the first waveguide material, a groove 20 is formed in a part of the first arm waveguide, and a second waveguide material different from the first waveguide material is formed. Fill there. For example, quartz having a temperature refractive index coefficient α ₁ of + 1.1 × 10 ⁻⁵ [1 / ° C.] is used as the first waveguide material, and an optical path length temperature coefficient α ₂ is used as the second waveguide material. , −37 × 10 ⁻⁵ [1 / ° C.] silicone resin is used. At this time, in order to make the Mach-Zehnder optical interference circuit temperature independent, it is possible to make the temperature independent if the optical interference circuit is designed so as to satisfy the above-described equation (1).

  Therefore, in Formula (2) that specifically describes Formula (1),

However,

It is sufficient to make it satisfying the above. Here, α ₁ and α ₂ are the optical path length temperature coefficient of the first waveguide material and the optical path length temperature coefficient of the second waveguide material, respectively, and n ₁ and n ₂ are respectively based on the first waveguide material. The effective refractive index and the effective refractive index of the second waveguide material, ΔL ₁ and ΔL ₂ are respectively the first arm waveguide and the second arm waveguide made of the first waveguide material. The optical path length difference and the optical path length difference between the first arm waveguide and the second arm waveguide constituted by the second waveguide material. Further, dn ₁ / dT and dn ₂ / dT are called refractive index temperature coefficients.

Between the first arm waveguide and the second arm waveguide constituting the optical interferometer, L ₁ ′ is the sum of the lengths of the grooves filled with the first waveguide material, and L ₁ is L _1. The length of the first arm waveguide in which the groove except 'is formed, and L ₂ is the length of the second arm waveguide in which the groove is not formed.

Thus, if it is designed to satisfy this, it can be made temperature independent. By doing so, it is possible to realize a Mach-Zehnder optical interference circuit having a constant transmission wavelength characteristic independent of the environmental temperature. FIG. 23 shows an example in which the transmission wavelength characteristics in the range of the environmental temperature −10 to +70 degrees are calculated. It can be seen that the transmission wavelength characteristic is constant without depending on the environmental temperature.

  In the above configuration, the thin film heater 32 is integrated around the groove in order to locally heat the optical resin 21 filled in the groove 20. When electric power is applied to this heater, a Mach-Zehnder optical interference circuit with variable transmission wavelength characteristics can be realized. An example of calculating the transmission characteristics is shown in FIG. That is, according to the present embodiment, it is possible to provide a Mach-Zehnder optical interference circuit that is temperature-independent with respect to the environmental temperature and has variable transmission wavelength characteristics.

  In the present embodiment, the case where the first arm waveguide is long and the second arm waveguide is long has been described. At this time, when the second optical waveguide material having a negative optical path length temperature coefficient is used as in this embodiment, the second optical waveguide material is filled on the first arm waveguide side, while the positive optical waveguide material is positive. When the second optical waveguide material having the optical path length temperature coefficient is used, the second optical waveguide material is filled on the second arm waveguide side.

  As a heater integration method, the heater 31 may be attached externally as described in the first embodiment, or between the grooves 20 and 20 as described in the second embodiment. The thin film heater 32 may be integrated on the clad 3 of the metal, or, as described in the third embodiment, the thin film heater 32 may be integrated at the bottom of the groove 20, and there is no restriction on its realization form. . Needless to say, a cooling mechanism may be used instead of a heating mechanism such as a heater.

  The design method for realizing the present embodiment will be specifically described below. As shown in FIG. 25, if the Mach-Zehnder optical interference circuit is composed of i types of optical waveguide materials, the temperature independence condition may satisfy the following expression. (FIG. 25 shows an example composed of three types of optical waveguide materials.)

Here, n _i is the refractive index of the optical waveguide material of the i, L _ia is the optical path length of the optical waveguide material of the i in the first arm waveguide, L _ib the optical of the i in the second arm waveguide The optical path length of the waveguide material, X _i, is the excess loss of the i-th optical waveguide material.

  For example, in the configuration shown in FIG. 22, as shown in FIG. 26, the first waveguide material is quartz, and the second waveguide material filled in a part of the first arm waveguide is an optical resin. It can be considered that the second arm waveguide is made of quartz as it is. Here, assuming that the refractive index of the optical resin is 1.39, the difference between the lengths of the first arm waveguide and the second arm waveguide formed of quartz is 1981 μm, and the second The length of the groove filled with the waveguide material is 46 μm. This groove does not necessarily need to be divided, but is usually divided in order to reduce radiation loss. The number of divisions depends on the etching conditions in the groove processing process. For example, if the number of divisions is five, the length per groove may be 9.2 μm.

  Further, as shown in FIG. 27, if the groove filled with the optical resin formed in the first arm waveguide is the first groove, a second groove is further formed on the second arm waveguide side. Thus, the loss between both arm waveguides may be made uniform. In this case, since the second groove is air, and its refractive index is 1.0003, the difference in length between the first arm waveguide and the second arm waveguide formed by quartz is The length of the first groove is 46.2 μm, and the length of the second groove is 11.7 μm. These grooves are not necessarily divided, but are usually divided in order to reduce radiation loss. For example, if the first groove is divided into five, the length per groove constituting the first groove is 9.24 μm, whereas if the second groove is divided into two, the length per groove constituting the first groove is divided into two. The length is 5.85 μm.

  Further, matching oil or the like may be filled so that dust or the like does not enter the second groove. For example, if the refractive index of the matching oil is 1.47, the difference between the lengths of the first arm waveguide and the second arm waveguide formed of quartz is 1990 μm, and the length of the first groove is 78 μm, and the length of the second groove is 39.3 μm. The second groove is not necessarily divided, but is usually divided and formed in order to reduce radiation loss. These grooves are not necessarily divided, but are usually divided in order to reduce radiation loss. For example, if the first groove is divided into 13, the length per groove constituting the first groove is 6 μm, whereas if the second groove is divided into 3, the length per groove constituting the first groove is 6 μm. Is 13.1 μm.

  As shown in FIG. 28, a third groove is formed in the first arm waveguide in addition to the first groove that satisfies the temperature independence condition. The third groove portion may be inserted for compensation with the same optical path length as the third groove portion formed in the arm waveguide. At this time, all the first and third grooves are filled with the same optical resin. Further, a common heating / cooling mechanism is mounted around the first groove portion and the third groove portion (here, an example in which thin film heaters are integrated is shown). Thus, by increasing the second optical waveguide material portion having a larger temperature refractive index coefficient than in FIG. 26, it becomes possible to further improve the variable efficiency of the transmission wavelength characteristic.

(Seventh embodiment)
FIG. 29A shows a seventh embodiment. This is an M-stage lattice optical interference circuit in which arm waveguides of a Mach-Zehnder optical interference circuit are connected in an M-stage column. The M-stage lattice optical interference circuit includes M + 1 optical couplers and M delay units arranged between adjacent ones of the optical couplers, and the delay units include the first arm waveguide and the first optical waveguide. The length difference between the first arm waveguide and the second arm waveguide is set to ΔL.

In this lattice optical interference circuit formed of the first waveguide material, a groove is formed in a part of the first arm waveguide, and a second waveguide material different from the first waveguide material is formed therein. Filled. Here, quartz having a temperature refractive index coefficient α ₁ of + 1.1 × 10 ⁻⁵ [1 / ° C.] is used as the first waveguide material, and the optical path length temperature coefficient α _{2 is} used as the second waveguide material. However, a silicone resin of −37 × 10 ⁻⁵ [1 / ° C.] was used.

  The transmission spectrum of the M-stage lattice optical interference circuit is expressed by the following equation.

Here, M is the number of stages, xq is the amplitude coefficient, ΔL is the optical path length difference between the arm waveguides, f is the optical frequency, and c is the speed of light. (M = 1 corresponds to the one-stage Mach-Zehnder optical interference circuit described in the sixth embodiment.)
At this time, in order to make the lattice optical interference circuit temperature independent, it is possible to make the temperature independent if the optical interference circuit is designed so as to satisfy the above-described equation (1).

  In the above configuration, a thin film heater is integrated around the groove formed in the first arm waveguide in order to locally heat the optical resin filled in the groove. By applying electric power to this heater, a lattice type optical circuit with variable transmission wavelength characteristics was realized. The transmission wavelength characteristics are shown in FIG. That is, according to the present embodiment, it is possible to provide a lattice optical interference circuit that is temperature-independent with respect to the environmental temperature and has variable transmission wavelength characteristics.

  In this embodiment, the optical path length differences of the first to Mth delay units are all set to ΔL, but the optical path length difference may be changed for each of the multistage delay units. In that case, a groove may be formed and filled with a resin so as to satisfy the above-described equation (1) according to the delay amount.

  Further, a loss is generated by forming a groove in the first arm waveguide. Therefore, as shown in FIG. 29 (b), both arms are formed by forming a groove for the same optical path length as the first arm waveguide filled with the optical resin and filling the optical resin to form the groove. The loss between the waveguides may be made uniform. Furthermore, the groove may be filled with a third waveguide material such as matching oil. This concept is the same as the description of FIGS. 26, 27, and 28 in the sixth embodiment.

(Eighth embodiment)
FIG. 31A shows an eighth embodiment. This is an M-stage transversal optical interference circuit in which arm waveguides of a Mach-Zehnder optical interference circuit are connected in parallel in M stages. The M-stage transversal optical interference circuit multiplexes an optical coupler that demultiplexes an input into M waveguides, an M arm waveguide connected to the optical coupler, and the M arm waveguides. It consists of an optical coupler. The optical path length difference between the second to Mth arm waveguides with respect to the first arm waveguide is set to ΔL + φ ₂ , 2ΔL + φ ₃ ,... (M−1) ΔL + φ _M , respectively. Here, φ _M is the phase of the Mth arm waveguide.

In the transversal optical interference circuit formed of the first waveguide material, a groove is formed in a part of the first to M-1 arm waveguides, and the second is different from the first waveguide material. The waveguide material was filled there. Here, quartz having a temperature refractive index coefficient α ₁ of + 1.1 × 10 ⁻⁵ [1 / ° C.] is used as the first waveguide material, and the optical path length temperature coefficient α _{2 is} used as the second waveguide material. However, a silicone resin of −37 × 10 ⁻⁵ [1 / ° C.] was used.

  The transmission spectrum of the M-stage transversal optical interference circuit is expressed by the following equation.

Here, M is the number of stages, xq is the amplitude coefficient, ΔL is the optical path length difference between the arm waveguides, f is the optical frequency, and c is the speed of light.

At this time, in order to make the transversal optical interference circuit temperature independent, it is possible to make the temperature independent if the optical interference circuit is designed so as to satisfy Equation (1) described above. .
In the above configuration, in order to locally heat the optical resin filled in the groove, the thin film heater is integrated around the groove formed in the first to M-1th arm waveguides. By applying electric power to this heater, a transversal optical interference circuit that is temperature-independent of the ambient temperature and variable in transmission wavelength characteristics was realized. Further, as shown in FIG. 31 (b), the loss between the arm waveguides may be made uniform by forming grooves for the same optical path length in all the arm waveguides and filling them with optical resin. This concept is the same as the description of FIGS. 26, 27, and 28 in the sixth embodiment.

(Ninth embodiment)
FIG. 32A shows a ninth embodiment. This is a 1 × 2 ^M filter in which Mach-Zehnder optical interference circuits having 1 input and 2 outputs are connected in M stages and multiple stages. The optical path length difference of the m-th Mach-Zehnder optical interference circuit is set to 2 ^M−m · ΔL + φm, k. Where φm, k is the phase of the kth element among the mth elements. For example, in the configuration of FIG.
The optical path length difference between the first and first elements is 4ΔL + φ1,1
The optical path length difference between the second and first elements is 2ΔL + φ2,1
The optical path length difference between the second and second elements is 2ΔL + φ2,2
The optical path length difference between the third stage and the first element is ΔL + φ3,1
The optical path length difference between the third and second elements is ΔL + φ3,2
The optical path length difference between the third and third elements is ΔL + φ3,3
The optical path length difference between the third and fourth elements is ΔL + φ3,4
Here, φ1,1 = 0, φ2,1 = π / 2, φ2,2 = 0, φ3,1 = π / 4, φ3,2 = 3π / 4, φ3,3 = π / 2, φ3,4 FIG. 33A shows the transmission wavelength characteristic when = 0 is set.

In the present 1 × 2 ^M filter formed of the first waveguide material, a groove is formed in a part of the arm waveguide, and a second waveguide material different from the first waveguide material is filled therein. . Here, quartz having a temperature refractive index coefficient α ₁ of + 1.1 × 10 ⁻⁵ [1 / ° C.] is used as the first waveguide material, and the optical path length temperature coefficient α _{2 is} used as the second waveguide material. However, a silicone resin of −37 × 10 ⁻⁵ [1 / ° C.] was used. At this time, in order to make the 1 × 2 ^M filter temperature independent, it is possible to make the temperature independent if the optical interference circuit is designed so as to satisfy the above-described equation (1). .

  In the above configuration, the thin film heater is integrated around the groove in order to locally heat the optical resin filled in the groove.

As described above, the transmission wavelength characteristics of the input port 1 and the output port 1 when the optical resin filled in the groove is locally heated by making the temperature independence are shown in FIG. By applying electric power to this heater, a Mach-Zehnder optical interference circuit type 1 × 2 ^M filter that is temperature-independent with respect to the environmental temperature and has variable transmission wavelength characteristics can be realized.

In the above configuration, the Mach-Zehnder optical interference circuit is used as an element constituting the 1 × 2 ^M filter. However, the lattice optical interference circuit or the transversal optical interference circuit described above may be used. Other optical interference circuits such as a ring optical interference circuit described later may be used, or a plurality of different optical interference circuits may be used. Further, as shown in FIG. 32 (b), the loss between the arm waveguides may be made uniform by forming a groove for the same optical path length for each pair of arm waveguides and filling with optical resin. . This concept is the same as the description of FIGS. 26, 27, and 28 in the sixth embodiment.

(Tenth embodiment)
FIG. 34 shows a tenth embodiment. This is a ring resonator 80 that includes a single waveguide 70 and a ring waveguide 71, and a directional coupler 72 is configured between the waveguide 70 and the ring waveguide 71. The ring resonator 80 has a transmission wavelength characteristic having a steep cutoff characteristic in the output characteristic from the output port R2 depending on the length of the ring waveguide 71 with respect to the input from the input port R1. Show.

  A groove 20 is formed in a part of the ring waveguide 71 and filled with an optical resin 21 having an optical path length temperature coefficient different from that of the ring waveguide 71. Here, by designing the conditions for forming the groove 20 and filling the optical resin 21 so as to satisfy Expression (1), a ring resonator that is temperature-independent with respect to the environmental temperature can be configured. . Therefore, the formula (2) that specifically describes the formula (1) may be satisfied in the ring waveguide. That is,

However,

Should be satisfied. Here, α ₁ and α ₂ are the optical path length temperature coefficient of the first waveguide material in the ring waveguide and the optical path length temperature coefficient of the second waveguide material in the ring waveguide, n ₁ and n ₂ , respectively. Are the effective refractive index of the first waveguide material in the ring waveguide and the effective refractive index of the second waveguide medium in the ring waveguide, respectively, and ΔL ₁ and ΔL ₂ are respectively in the ring waveguide. It is the optical path length difference by the waveguide comprised by the 1st waveguide material, and the optical path length difference by the waveguide comprised by the 2nd waveguide material in a ring waveguide. Further, dn ₁ / dT and dn ₂ / dT are called refractive index temperature coefficients.

In the ring waveguide constituting an optical interferometer, L 1 _', and the total length of the groove filled with the first waveguide material, the L _1, L _1' ring guide said grooves are formed with the exception of If the length of the waveguide,

Thus, if it is designed to satisfy this, it can be made temperature independent.

  Furthermore, a mechanism for locally heating or cooling the optical resin 21 is mounted. Here, an example in which the thin film heater 32 is integrated around the groove 20 filled with the optical resin 21 will be described. That is, by heating the optical resin 21, the refractive index of the portion changes, and as a result, the effective optical path length changes. Then, the resonance frequency (wavelength) of the ring resonator 70 changes, and the transmission wavelength characteristic can be made variable. That is, according to the present embodiment, it is possible to provide an optical waveguide circuit that has variable transmission wavelength characteristics and is temperature-independent with respect to the environmental temperature.

(Eleventh embodiment)
FIG. 35 shows an eleventh embodiment. Unlike the optical waveguide circuit described in the tenth embodiment, this is a ring resonator 80 having directional couplers 72 between the waveguide 70 and the ring waveguide 71 at two locations. The ring resonator 80 exhibits a steep transmission wavelength characteristic with respect to the input from the input port S1, depending on the length of the ring waveguide, in the output characteristic from the output port S2.

  Similarly, in this circuit, the groove 20 is formed in a part of the ring waveguide 71 and filled with the optical resin 21 having an optical path length temperature coefficient different from that of the ring waveguide 71. Also here, by designing the conditions for forming the groove 20 and filling the optical resin 21 so as to satisfy the expression (1), the optical waveguide has a variable transmission wavelength characteristic that is temperature-independent with respect to the environmental temperature. It becomes possible to provide a circuit.

(Twelfth embodiment)
FIG. 36 shows a twelfth embodiment. Here, an optical signal monitor 200 that can be configured by integrating the PD 501 in the AWG 201 with variable transmission wavelength characteristics described in the first to fifth embodiments will be described. That is, the basic configuration of this optical signal monitor is the one in which a CSP type PD array 500 in which a plurality of PDs 501 are integrated is attached to the end face of the output waveguide 15 of the AWG 10 as in the conventional technique shown in FIG. There is a difference, however, in that a heater 30 is arranged to locally heat the optical resin 21 filled with grooves formed for temperature independence. As described in the first to fifth embodiments, the heater may be integrated by mounting an external heater or by integrating a thin film heater, regardless of the form. It goes without saying that there is nothing. In FIG. 36, it shows only based on FIG. 7 of 1st Example. Also here, the conditions for forming the grooves and filling the optical resin are designed so as to satisfy the conditional expression (1) that is temperature-independent with respect to the environmental temperature as in the previous embodiment.

The operation of the optical signal monitor 200 according to this configuration will be described below. When a WDM signal obtained by combining a plurality of wavelength signals is input from the input waveguide 11 of the AWG 10, each wavelength signal is output for each output waveguide 15 according to the operation principle of the AWG. The light is received by the PD 501 and converted into an electrical signal and output. At this time, when electric power is applied to the heater 30, the optical resin 21 filled in the groove 20 is heated, and the transmission wavelength characteristics of the AWG 10 move as described above. At this time, the power applied to the heater 30 may be such that the movable range of the transmission characteristics of the AWG 10 can be swept within a range narrower than the transmission band of each channel. FIG. 37A shows how the optical signal 700 transmitted through each channel is monitored while the heater 30 is driven. When electric power is applied to the heater 30, the transmission characteristic 701 of the AWG 10 is moved in proportion to it (arrow in the figure), and the corresponding photocurrent from the PD 501, that is, the monitor signal 702 is output (FIG. 37 (b)). Since the power applied to the heater 30 can be associated with wavelength (λ) information, the applied power at which the monitor signal 702 reaches a peak, that is, the wavelength position (λ ₁ ), is the wavelength of the optical signal transmitted through the channel. It can be detected. In addition, the peak value (P ₁ ) of the vertical axis power (P) can be detected as the optical power of the optical signal 700. Furthermore, the ratio between the peak value (P ₁ ) of the monitor signal 702 and the noise level (P _N ) value of the monitor signal can be detected as OSNR. As described above, the optical signal monitor that can only detect the optical power in the conventional technique is configured by changing the AWG into a variable filter in the present embodiment to constitute the optical signal monitor. Can also monitor OSNR.

  As described above, the sweep variable range of the transmission wavelength characteristic may be a range that can be driven with an applied power that has a variable range equal to or smaller than the channel frequency interval of the AWG. This is because the AWG can simultaneously output optical signals of respective channel frequencies (that is, wavelengths) for each output waveguide. Therefore, the optical signal monitor according to the present embodiment has a feature that all the optical signals of the wavelength channels can be collectively monitored by driving the sweep wavelength variable range narrower than the transmission band of each channel. This is characterized in that the wavelength information can be extracted in parallel as compared with the optical signal monitor that sweeps the tunable filter over the entire wavelength range on the system, so that the reading speed is increased.

  Note that by designing the transmission bandwidth of the AWG 10 to be narrower, the waveform of the optical signal can be monitored with higher accuracy. Therefore, it is possible to monitor the waveform due to the difference in the bit rate of the modulated optical signal and the difference in the modulation format.

  As described above, the present invention is characterized in that, by mounting the CSP type PD array 500, it is possible to construct a temperature-independent OPM that is unprecedented in compactness and does not vary in monitor characteristics with respect to the environmental temperature. .

(Thirteenth embodiment)
FIG. 38 shows a thirteenth embodiment. This embodiment is different from the previous twelfth embodiment in that the CSP-PD array is attached to the end surface of the second slab 14. By doing so, the output waveguide portion can be eliminated, so that it is possible to further reduce the size of the optical signal monitor.

(Fourteenth embodiment)
FIG. 39 shows a fourteenth embodiment. In the present embodiment, the PD 501 is attached to the end face of the output waveguide of the Mach-Zehnder optical interference circuit type 1 × 2 ^M filter in the ninth embodiment (see FIG. 32B, which may be in the form of FIG. 32A). ing. The PD 501 may be mounted with a single-channel CSP type PD array 500, but the form is not particularly limited. The output port to which the PD is attached depends on the design of the Mach-Zehnder optical interference circuit type 1 × 2 ^M filter. By locally heating the optical resin 21 filled in the groove 20 formed in a part of each arm waveguide, the transmission wavelength characteristic can be made variable. Also here, the conditions for forming the groove 20 and filling the optical resin 21 are designed so as to satisfy the conditional expression (1) for making the temperature independent of the environmental temperature. When the transmission wavelength characteristic is swept by heating the heater, a photocurrent from the PD 501, that is, a monitor signal is output accordingly. By sweeping the transmission wavelength characteristic, not only the optical power but also the wavelength and OSNR can be detected. Here, as the elements constituting the 1 × 2 ^M filter, the lattice optical interference circuit or the transversal optical interference circuit described above may be used, or other optical interference circuits such as a ring optical interference circuit described later are used. Alternatively, a plurality of different optical interference circuits may be used. By doing so, an OPM independent of the environmental temperature can be configured.

(15th Example)
FIG. 40 shows a fifteenth embodiment. The present embodiment shows an example in which the PD 501 is integrated in the output port S2 of the ring resonator 80 according to the eleventh embodiment. The PD 501 may be mounted with a single-channel CSP type PD array 500, but the form is not particularly limited. By locally heating the optical resin 21 filled in the groove 20 formed in a part of the ring waveguide 71, the resonance frequency (wavelength) can be made variable. Also here, the conditions for forming the groove 20 and filling the optical resin 21 are designed so as to satisfy the conditional expression (1) for making the temperature independent of the environmental temperature. When the transmission wavelength characteristic is swept by heating the heater, a photocurrent from the PD 501, that is, a monitor signal 702 is output accordingly. By sweeping the transmission wavelength characteristic, not only the optical power but also the peak wavelength and OSNR can be detected.

  As described above, the present invention is also characterized in that it is possible to construct an OPM that is unprecedented and compact and does not vary in monitor characteristics with respect to the environmental temperature and does not depend on the environmental temperature.

It is a figure which shows the array waveguide diffraction grating type | mold optical multiplexer / demultiplexer (AWG) which is an example of the conventional optical interference circuit. It is a figure which shows the example which mounted the photodiode (PD) directly as a light receiving element in the end surface of each output waveguide of AWG of FIG. It is a figure which shows the form which made temperature independent the AWG of FIG. FIG. 4 is a cross-sectional view taken along line A-A ′ of FIG. 3. It is a figure which shows the deformation | transformation form of AWG of FIG. It is a figure which shows the deformation | transformation form of AWG of FIG. It is a figure which shows AWG which concerns on 1st Embodiment. FIG. 8 is a sectional view taken along line B-B ′ of FIG. 7. It is a figure which shows the transmission wavelength characteristic with respect to the applied electric power of AWG which concerns on 1st Embodiment. It is a figure which shows the deformation | transformation form of AWG which concerns on 1st Embodiment. It is a figure which shows the deformation | transformation form of AWG which concerns on 1st Embodiment. It is a figure which shows the deformation | transformation form of AWG which concerns on 1st Embodiment. It is a figure which shows AWG which concerns on 2nd Embodiment. FIG. 14 is a cross-sectional view taken along line C-C ′ of FIG. 13. It is a figure which shows the center transmission frequency characteristic with respect to the applied electric power of AWG which concerns on 2nd Embodiment. It is a figure which shows the result of having measured the center wavelength with respect to environmental temperature by making applied electric power into a parameter with respect to AWG which concerns on 2nd Embodiment. It is a figure which extracts and shows the pattern of a groove | channel and a thin film heater. It is a figure which shows AWG which concerns on 3rd Embodiment. It is sectional drawing along the D-D 'line of FIG. It is a figure which shows AWG which concerns on 4th Embodiment. It is a figure which shows AWG which concerns on 5th Embodiment. It is a figure which shows the optical interference circuit which concerns on 6th Embodiment. It is a figure which shows an example which calculated the transmission wavelength characteristic in the range of -10 to +70 degree | times of environmental temperature about the optical interference circuit which concerns on 6th Embodiment. It is a figure which shows an example which calculated the transmission characteristic about the optical interference circuit which concerns on 6th Embodiment. It is a figure for demonstrating the design method of the optical interference circuit which concerns on 6th Embodiment. It is a figure which shows the specific example of a structure of FIG. It is a figure which shows the modification of a structure of FIG. It is a figure which shows the modification of a structure of FIG. (A) is a figure which shows the M stage lattice optical interference circuit which concerns on 7th Embodiment, (b) is a figure which shows the modification of (a). It is a figure which shows the transmission wavelength characteristic of the lattice optical interference circuit which concerns on 7th Embodiment. (A) is a figure which shows the M stage transversal optical interference circuit which concerns on 8th Embodiment, (b) is a figure which shows the modification of (a). (A) is a figure which shows the 1 * 2 ^M filter which concerns on 9th Embodiment, (b) is a figure which shows the modification of (a). It is a figure which shows the transmission characteristic of the 1 * 2 ^M filter which concerns on 9th Embodiment. It is a figure which shows the ring resonator which concerns on 10th Embodiment. It is a figure which shows the ring resonator which concerns on 11th Embodiment. It is a figure which shows the optical signal monitor which concerns on 12th Embodiment. It is a figure which shows a mode that the optical signal which permeate | transmits each channel is monitored, driving a heater in the optical signal monitor which concerns on 12th Embodiment. It is a figure which shows the optical signal monitor which concerns on 13th Embodiment. It is a figure which shows the optical signal monitor which concerns on 14th Embodiment. It is a figure which shows the optical signal monitor which concerns on 15th Embodiment.

Explanation of symbols

1 substrate 2 core 3 clad (corresponding to upper clad and lower clad)
10 AWG (compatible with wavelength tunable filter)
11 Input waveguide (corresponding to input channel waveguide)
12 First slab waveguide (corresponding to slab waveguide on the input side)
13 Arrayed waveguide 14 Second slab waveguide (corresponding to slab waveguide on output side)
15 Output waveguide (corresponding to output channel waveguide)
20 groove 21 optical resin (corresponds to material)
30 Heater (corresponding to the mechanism for heating or cooling the material)
31 (External) heater 32 Thin film heater 40 Electrical wiring 60 First optical coupler (corresponding to directional coupler)
61 Second optical coupler (corresponding to directional coupler)
62 first arm waveguide 63 second arm waveguide 70 input / output waveguide 71 ring waveguide 72 directional coupler 80 ring resonator 121 first groove 122 second groove 131 first heater 132 second Heater 200 Optical signal monitor 201 AWG (corresponding to wavelength tunable filter)
500 CSP type PD array 501 PD (corresponding to photodiode)
502 Housing 503 Glass window 700 Optical signal 701 Transmission characteristics of AWG 702 Monitor signal

Claims (6)

In a wavelength tunable filter that demultiplexes input wavelength multiplexed light and outputs a plurality of lights having different wavelengths.
A predetermined multiple channel waveguides having a different length by length, a plurality of channel guide for demultiplexing the multi-wavelength light by a change due to the wavelength of the phase difference occurring between said plurality of channel waveguides An arrayed waveguide diffraction grating composed of waveguides;
A slab waveguide on the input side disposed between the arrayed waveguide grating and the input channel waveguide;
An output-side slab waveguide disposed between the arrayed waveguide grating and the output channel waveguide;
The slab waveguide on the output side is arranged so as to intersect the traveling direction of the light, and for each wavelength of input light, the slab waveguide on the output side passes through the plurality of channel waveguides of the arrayed waveguide diffraction grating from the slab waveguide on the input side. A material that cancels a change in temperature of the phase difference that occurs between paths to the waveguide;
A mechanism for heating or cooling the material ,
Each of the waveguides is composed of an upper clad, a core, and a lower clad,
The slab waveguide on the input side or the output side is a plurality of grooves formed in a curved shape so as to intersect the traveling direction of light , and has a plurality of grooves filled with the material,
The plurality of grooves are formed by removing the upper cladding and the core from the input or output slab waveguide, or from the input or output slab waveguide to the upper cladding, Formed by removing the core and the lower cladding,
The material, Ri materials der having a temperature coefficient different from the refractive index temperature coefficient of the effective refractive index of the slab waveguide having a plurality of grooves,
The plurality of grooves are grouped;
The mechanism, wavelength variable filter you characterized in that heating or cooling independently the material for each group. In a wavelength tunable filter that demultiplexes input wavelength multiplexed light and outputs a plurality of lights having different wavelengths.
A predetermined multiple channel waveguides having a different length by length, a plurality of channel guide for demultiplexing the multi-wavelength light by a change due to the wavelength of the phase difference occurring between said plurality of channel waveguides An arrayed waveguide diffraction grating composed of waveguides;
A slab waveguide on the input side disposed between the arrayed waveguide grating and the input channel waveguide;
An output-side slab waveguide disposed between the arrayed waveguide grating and the output channel waveguide ;
A material that is arranged so as to intersect the traveling direction of light and cancels a change due to temperature of the phase difference with respect to light of each wavelength;
A mechanism for heating or cooling the material ,
Each of the waveguides is composed of an upper clad, a core, and a lower clad,
The array waveguide diffraction grating is a plurality of grooves formed so as to intersect span before SL plurality of channel waveguides, a plurality of grooves which are filled by the material,
The plurality of grooves are formed by removing the upper cladding and the core from the plurality of channel waveguides, or remove the upper cladding, the core and the lower cladding from the plurality of channel waveguides. Formed by
The material, Ri materials der having a temperature coefficient different from the refractive index temperature coefficient of the effective refractive index of said plurality of channel waveguides,
The plurality of grooves are grouped;
The mechanism, wavelength variable filter you characterized in that heating or cooling independently the material for each group. In a wavelength tunable filter that demultiplexes input wavelength multiplexed light and outputs a plurality of lights having different wavelengths.
A predetermined multiple channel waveguides having a different length by length, a plurality of channel guide for demultiplexing the multi-wavelength light by a change due to the wavelength of the phase difference occurring between said plurality of channel waveguides An arrayed waveguide diffraction grating composed of waveguides;
A slab waveguide on the input side disposed between the arrayed waveguide grating and the input channel waveguide;
An output-side slab waveguide disposed between the arrayed waveguide grating and the output channel waveguide;
The slab waveguide on the output side is arranged so as to intersect the traveling direction of the light, and for each wavelength of input light, the slab waveguide on the output side passes through the plurality of channel waveguides of the arrayed waveguide diffraction grating from the slab waveguide on the input side. A material that cancels a change in temperature of the phase difference that occurs between paths to the waveguide;
A mechanism for heating or cooling the material ,
Each of the waveguides is composed of an upper clad, a core, and a lower clad,
The slab waveguide on the input side or the output side is a plurality of grooves formed in a curved shape so as to intersect the traveling direction of light , and has a plurality of grooves filled with the material,
The plurality of grooves are formed by removing the upper cladding and the core from the input or output slab waveguide, or from the input or output slab waveguide to the upper cladding, Formed by removing the core and the lower cladding,
The material, Ri materials der having a temperature coefficient different from the refractive index temperature coefficient of the effective refractive index of the slab waveguide having a plurality of grooves,
The plurality of grooves are grouped into a first groove group and a second groove group,
The first groove group has a number of first grooves that do not satisfy the temperature independence condition that does not change its optical characteristics with respect to the environmental temperature,
The second groove group has the number of second grooves as many as the temperature independence condition that is no longer satisfied by the first groove group,
The first groove is configured such that the width in the optical axis direction becomes narrower from the larger optical path length difference toward the smaller one,
The second groove is configured such that the width in the optical axis direction increases from the larger optical path length difference toward the smaller optical path length,
The mechanism, wavelength variable filter you characterized in that heating or cooling only the material filled in the first trench. In a wavelength tunable filter that demultiplexes input wavelength multiplexed light and outputs a plurality of lights having different wavelengths.
A predetermined multiple channel waveguides having a different length by length, a plurality of channel guide for demultiplexing the multi-wavelength light by a change due to the wavelength of the phase difference occurring between said plurality of channel waveguides An arrayed waveguide diffraction grating composed of waveguides;
A slab waveguide on the input side disposed between the arrayed waveguide grating and the input channel waveguide;
An output-side slab waveguide disposed between the arrayed waveguide grating and the output channel waveguide ;
A material that is arranged so as to intersect the traveling direction of light and cancels a change due to temperature of the phase difference with respect to light of each wavelength;
A mechanism for heating or cooling the material ,
Each of the waveguides is composed of an upper clad, a core, and a lower clad,
The array waveguide diffraction grating is a plurality of grooves formed so as to intersect span before SL plurality of channel waveguides, a plurality of grooves which are filled by the material,
The plurality of grooves are formed by removing the upper cladding and the core from the plurality of channel waveguides, or remove the upper cladding, the core and the lower cladding from the plurality of channel waveguides. Formed by
The material, Ri materials der having a temperature coefficient different from the refractive index temperature coefficient of the effective refractive index of said plurality of channel waveguides,
The plurality of grooves are grouped into a first groove group and a second groove group,
The first groove group has a number of first grooves that do not satisfy the temperature independence condition that does not change its optical characteristics with respect to the environmental temperature,
The second groove group has the number of second grooves as many as the temperature independence condition that is no longer satisfied by the first groove group,
The first groove is configured such that the width in the optical axis direction becomes narrower from the larger optical path length difference toward the smaller one,
The second groove is configured such that the width in the optical axis direction increases from the larger optical path length difference toward the smaller optical path length,
The mechanism, wavelength variable filter you characterized in that heating or cooling only the material filled in the first trench. In a wavelength tunable filter that demultiplexes input wavelength multiplexed light and outputs a plurality of lights having different wavelengths.
A plurality of channel waveguides having different lengths by a predetermined length, wherein the plurality of channel waveguides demultiplex the wavelength-multiplexed light by a change in wavelength caused by a phase difference generated between the plurality of channel waveguides; ,
A material that is arranged so as to intersect the traveling direction of light and cancels a change due to temperature of the phase difference with respect to light of each wavelength;
A mechanism for heating or cooling the material;
With
The plurality of channel waveguides are:
It consists of an upper cladding, a core, and a lower cladding,
N sets of arm waveguides sandwiched between N + 1 (N is an integer of 1 or more) optical couplers and an adjacent optical coupler,
Each of the N sets of arm waveguides includes a first arm waveguide and a second arm waveguide having different optical path lengths,
Wherein the first arm waveguide, the first groove portion and the second groove portion is formed,
In the second arm waveguide, a third groove portion having the same optical path length as the second groove portion is formed,
Said first groove, the second groove portion and the third groove portion is formed by removing the upper clad and said core from said first arm waveguide and the second arm waveguide Or by removing the upper cladding, the core, and the lower cladding from the first arm waveguide and the second arm waveguide ,
Said first groove, said the second groove portion and the third groove portion, the refractive index temperature coefficient different from the first arm waveguide and the temperature coefficient of the effective refractive index of the second arm waveguide same of the material with the filled,
Said first groove and a second of said material filled in the groove, the wavelength variable filter you characterized in that it is heated or cooled by a common said mechanism. The output of the wavelength tunable filter according to any of claims 3 to 5, one or optical signal monitoring, characterized in that it comprises a plurality of photodiodes.