JP2009036901A - Optical signal processor - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To solve problems associated with performance degradation in an optical signal processor according to temperature owing to temperature dependence of spectral characteristics of a beam splitting device in the conventional optical signal processor, wherein occurrence of excessive loss is inevitable when a method of forming a plurality of grooves to partition cores on an array waveguide of an AWG is adopted for the purpose of dissolving the temperature dependence of the spectral characteristics of the AWG, and the manufacturing cost is increased because a complicated additional process is necessary for manufacturing of the AWG when a groove structure is to be formed. <P>SOLUTION: The temperature compensation of the AWG in itself is made unnecessary by compensating the temperature dependence of spectral characteristics of the AWG using a simple temperature compensating means in a spatial optical system. A tilt angle of an optical path converting means can be controlled or a thermooptic effect, or an electro-optic effect can be used. The optical characteristics of the optical signal processor is made independent of temperature by using a construction simpler than a conventional technique on the basis of a temperature compensating action in the spatial optical system. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention relates to an optical signal processing device. More specifically, the present invention relates to temperature compensation of an optical signal processing device including a spectroscopic element.

  As the speed and capacity of optical communication networks have increased, there has been an increasing need for optical signal processing apparatuses such as those represented by processing of wavelength division multiplexing (WDM) transmission signals. For example, there is a demand for a function of switching the path of multiplexed optical signals between nodes. Transparency of an optical signal processing device is being promoted by performing path conversion without changing optical-electrical conversion without changing the optical signal.

  On the other hand, from the viewpoint of miniaturization and integration of an optical signal processing device, research and development of a waveguide type optical circuit (PLC: Planar Lightwave Circuit) is in progress. In a PLC, for example, a core made of quartz glass is formed on a silicon substrate, and various functions are integrated on one chip, thereby realizing an optical functional device with low loss and high reliability. Furthermore, a complex optical signal processing component (apparatus) that combines a plurality of PLC chips and other optical functional components has also appeared.

  For example, Patent Document 1 discloses an optical signal processing device in which a waveguide type optical circuit (PLC) including AWG or the like and a spatial modulation element such as a liquid crystal element are combined. More specifically, a wavelength blocker including a PLC and a collimating lens arranged symmetrically with respect to the liquid crystal element, a wavelength equalizer, a dispersion compensator, and the like are being studied. In these optical signal processing devices, optical signal processing is performed independently for each wavelength for a plurality of optical signals having different wavelengths.

  FIG. 16 is a conceptual diagram illustrating an example of an optical signal processing device. In this optical signal processing apparatus, an optical signal is input / output via the spectroscopic element 51. The spectroscopic element 51 demultiplexes the wavelength-multiplexed WDM optical signal at an emission angle θ corresponding to the wavelength. The demultiplexed optical signal is emitted toward the condenser lens 52. The optical signal collected by the condensing lens 52 is condensed at each condensing point at a predetermined position of the signal processing element 53 having a function of intensity modulation, phase modulation or deflection corresponding to the emission angle θ. . That is, it should be noted that the optical signal is collected at different positions of the signal processing element depending on the wavelength of the input optical signal. The signal processing element 53 is, for example, a liquid crystal element composed of a plurality of element elements (pixels). By controlling the transmittance of each element, the optical signal of each wavelength is subjected to intensity modulation and the like, and a predetermined signal processing function is realized. The optical signal subjected to the signal processing is reflected by the mirror 54 to reverse the traveling direction. The optical signal further passes through the condenser lens 52 and is multiplexed again in the spectroscopic element 51. As is generally well known, the spectroscopic element 51 can also multiplex optical signals according to the traveling direction. The combined optical signal of each wavelength is output again as output light to the outside of the optical signal processing device.

  In FIG. 16, the spectroscopic element 51 is conceptually shown as long as it can perform demultiplexing and multiplexing according to the wavelength of the optical signal. For example, the spectroscopic elements include a grating, a prism, and an arrayed waveguide grating (AWG). The signal processing element only needs to be capable of modulating the intensity or phase of the optical signal, or the intensity and phase, or capable of deflecting the traveling direction of the optical signal. For example, the signal processing element includes a liquid crystal element, a MEMS (Micro Electro Mechanical Systems) mirror, and an optical crystal.

  The optical signal processing apparatus shown in FIG. 16 has a configuration in which both optical signal demultiplexing and multiplexing are performed by one spectroscopic element by folding the optical signal using a mirror. This configuration is generally called a reflection type. An apparatus that performs optical signal processing such as a wavelength block is not limited to this configuration. For example, without using the mirror of FIG. 16, the signal processing element is positioned at the symmetry axis, and an output system composed of another lens and a spectroscopic element is provided on the opposite side of the incident system on the extended line of the incident optical path axis. Arranged configurations are also possible. This configuration is a configuration that performs demultiplexing and multiplexing of optical signals via independent incident and outgoing systems, respectively, and is called a transmission type. Further, in the apparatus configuration shown in FIG. 16, it is possible to combine the optical signals by changing the direction of the mirror and using an emission system including another lens and a spectroscopic element arranged at an arbitrary position. For example, the reflecting surface of the mirror can be inclined by 45 degrees with respect to the incident optical path of the optical signal, and the exit system can be configured by a lens and a spectroscopic element arranged in a direction perpendicular to the incident optical path. When the signal processing element has a deflection function, a plurality of emission systems can be provided.

  In FIG. 16, the spectroscopic element 51 and the condensing lens 52 are arranged apart from each other by the front focal length FFL, and the signal processing element 53 and the condensing lens 52 are arranged apart from each other by the rear focal length BFL. The focal point of the light collected by the condenser lens 52 must be on the surface of the mirror 54 at all wavelengths used. When deviating from the mirror surface, there arises a problem of causing a coupling loss between input and output light. At the same time, since the beam spot diameter of the collected optical signal is increased, there arises a problem that the wavelength resolution is lowered.

  In addition, the signal processing element 53 needs to have a spatially periodic structure in order to selectively modulate each wavelength of the optical signal. For example, when the signal processing element 53 is a liquid crystal element, the structure of the element element of the liquid crystal element must be designed according to the optical characteristics of the spectroscopic element and the condenser lens.

  More specifically, it is known that the wavelength dependence of the condensing position on the signal processing element follows that obtained by multiplying the angular dispersion value of the spectroscopic element by the focal length of the condensing lens. The wavelength dependence of the light collection position is also called a linear dispersion value of the spectroscopic optical system. The linear dispersion value of the optical system determined by the spectroscopic element and the condensing lens needs to be sufficiently coincident with the linear dispersion value used for designing the structure of the signal processing element. If there is a deviation in these linear dispersion values, the position of the condensing point of the actual optical signal does not coincide with the position of each element element (for example, a pixel of the liquid crystal shutter element) of the signal processing element. This mismatch results in a wavelength error in the processed optical signal.

Japanese Patent Laid-Open No. 2002-250828 (pages 16, 19, 20, 20, 27, 29D, etc.) Japanese Patent Application Laid-Open No. 2004-239991 JP 2001-255242 A

  However, the conventional optical signal processing apparatus has a problem that the performance of the optical signal processing apparatus deteriorates due to the temperature because the spectral characteristic of the spectral element has temperature dependency. In the optical signal processing apparatus having the configuration shown in FIG. 16, the case where the spectroscopic element is an AWG is considered. Even if the optical signals have the same wavelength, the position of the condensing point on the signal processing element varies when the emission angle changes depending on the temperature. For this reason, temperature dependence occurs in the optical coupling loss.

  Conventionally, in order to eliminate the temperature dependence of the spectral characteristics of the AWG, it has been studied to reduce the temperature dependence of the AWG itself. For example, Patent Document 3 discloses a technique for temperature compensation by a configuration in which a plurality of characteristic grooves for dividing a core are formed on an array waveguide of an AWG. According to this technique, an excessive loss of about 1 dB cannot be avoided by forming the groove itself. Further, even when the shape of the groove is optimized, the excess radiation loss due to the optical signal radiation in the vertical direction of the AWG substrate cannot be sufficiently suppressed. Further, in order to form the groove structure, a complicated additional process is required for manufacturing the AWG, and there is a problem that the manufacturing cost is high.

  The problem caused by the temperature dependence of the spectral characteristics of the AWG can be similarly a problem even in an optical signal processing apparatus that does not include a condenser lens. As described above, it is required to solve the problem of temperature fluctuation in the performance of the optical signal processing apparatus due to the temperature dependence of the spectral characteristics of the AWG more easily and at a low cost.

  In order to achieve such an object, the present invention according to claim 1 divides an optical signal into a plurality of optical signals having different wavelengths and separates the optical signals of the respective wavelengths. In an optical signal processing apparatus for processing, a spectroscopic unit that splits a plurality of optical signals having different wavelengths at an emission angle corresponding to the wavelength of the optical signal, and a signal processing unit that modulates the optical signal output from the spectroscopic unit And an optical path conversion unit disposed in the optical path between the spectroscopic unit and the signal processing unit, and refracts the optical path of the optical signal, and cancels the temperature dependence of the emission angle from the spectroscopic unit Thus, there is provided an optical signal processing device comprising means for refracting the optical path of the optical signal.

  According to a second aspect of the present invention, there is provided the signal processing apparatus according to the first aspect, wherein the optical signal is offset so as to cancel out the temperature dependence of the emission angle of the spectroscopic means by the refractive index temperature dependence characteristic of the optical path changing means. The emission angle from the optical path changing means is changed.

  According to a third aspect of the present invention, there is provided the signal processing device according to the second aspect, wherein the optical signal is converted from the optical path conversion unit of the optical signal by using a thermo-optic effect or an electro-optical effect of the optical path conversion unit as the refractive index temperature dependent characteristic. It is characterized in that the emission angle of is changed.

  According to a fourth aspect of the present invention, in an optical signal processing apparatus that splits an optical signal into a plurality of optical signals of different wavelengths and performs signal processing on the optical signals of the respective wavelengths, the optical signal processing apparatus is adapted to the wavelength of the optical signal Spectroscopic means for splitting a plurality of optical signals having different wavelengths at an emission angle, condensing means for condensing the optical signal emitted from the spectroscopic means, and the optical signal collected by the condensing means A signal processing unit to be modulated is arranged in one of the optical paths between the spectroscopic unit and the condensing unit or between the condensing unit and the signal processing unit, and refracts the optical path of the optical signal. An optical signal processing apparatus comprising: an optical path conversion unit, and a unit that refracts the optical path of the optical signal so as to cancel out the temperature dependence of the emission angle from the spectroscopic unit.

  According to a fifth aspect of the present invention, there is provided the signal processing device according to the fourth aspect, wherein a main optical path of the light collecting means of the light path converting means arranged in the light path between the light collecting means and the signal processing means. A driving unit that changes an inclination angle with respect to an axis; and a temperature detection unit that detects a temperature of the spectroscopic unit, and the driving unit changes the inclination angle based on the temperature detected by the temperature detection unit. Thus, the condensing point position of the optical signal in the signal processing means is changed.

  According to a sixth aspect of the present invention, in the signal processing device according to the fourth aspect, the thermo-optic effect of the optical path conversion means disposed in the optical path between the condensing means and the signal processing means is utilized. The condensing point position of the optical signal in the signal processing means is changed.

  According to a seventh aspect of the present invention, in the signal processing device according to the fifth or sixth aspect, the optical path changing means disposed in an optical path between the light collecting means and the signal processing means is a glass parallel plate. It is characterized by that.

  According to an eighth aspect of the present invention, in the signal processing device according to the fourth aspect, the thermo-optic effect or the electro-optic effect of the optical path conversion means arranged in the optical path between the spectroscopic means and the condensing means. Utilizing this, the emission angle of the optical signal from the optical path changing means is changed.

  The invention according to claim 9 is an optical signal processing apparatus for performing optical signal processing on each optical signal having a different wavelength by separating the optical signal into a plurality of optical signals having different wavelengths, and according to the wavelength of the optical signal. A spectroscopic unit that splits light signals having different wavelengths at an emission angle, a signal processing unit that modulates the optical signal emitted from the spectroscopic unit, and one of the spectroscopic unit and the signal processing unit. A movable means for changing a relative position of the spectroscopic means and the signal processing means with respect to the direction of the axis of intersection between the demultiplexing surface of the spectroscopic means and the signal processing means, One of the positions is changed so as to cancel out the temperature dependence of the emission angle.

  As described above, according to the present invention, the temperature variation of the performance of the optical signal processing device due to the temperature dependence of the spectral characteristics of the AWG is compensated for temperature in the spatial optical system, thereby making it easier and less expensive. The temperature can be made independent by the method. The optical coupling loss in the spatial optical system of the optical signal processing device can be greatly reduced.

  Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings. The optical signal processing apparatus of the present invention eliminates the temperature compensation of the AWG itself by compensating the temperature dependence of the spectral characteristics of the AWG using simple temperature compensation means in the spatial optical system. Due to the temperature compensation action in the spatial optical system, sufficient temperature independence of the optical characteristics can be realized with a simpler configuration than the prior art. Temperature compensation in the AWG element itself becomes unnecessary, and the manufacturing process of the AWG is simplified to realize cost reduction.

“First Example”:
FIG. 1 is a diagram showing a configuration of an optical signal processing apparatus according to a first embodiment of the present invention. This optical signal processing apparatus has a reflection type configuration that includes a mirror and inputs / outputs an optical signal by one spectroscopic element. A plurality of optical signals having different wavelengths are demultiplexed by the spectroscopic element 1 such as an AWG, and are emitted from the end face of the AWG 1 at an emission angle corresponding to the wavelength. The emitted optical signal passes through the cylindrical lens 2 and becomes parallel light. The optical signal is further condensed by the condenser lens 3 and modulated by the signal processing element 5. The modulated optical signal is reflected by the mirror 6, travels in the opposite direction in the above path, and is multiplexed by the AWG1. The above-described operation is the same as that of a conventional optical signal processing device. In the present invention, the spatial optical system between the condensing lens 3 and the signal processing element 5 is provided with the optical path changing means 4. Different from conventional technology. Furthermore, the present invention is characterized in that the optical path changing means 4 acts as a temperature compensating means or as a part of the temperature compensating means.

  Specifically, the optical path changing means 4 can be a glass parallel plate, for example. When the glass parallel plate does not have a thermo-optic action, it operates with the temperature sensor 7 arranged on the AWG 1 to compensate for the temperature dependence of the spectral characteristics of the AWG 1. In this case, temperature compensation can be performed by controlling the inclination angle of the glass parallel plate with respect to the optical axis. Further, when the thermo-optic action of the glass parallel plate is used, temperature compensation is possible only with the glass parallel plate set at a predetermined inclination angle. Hereinafter, the temperature compensation operation of the present invention will be described in detail.

  FIG. 2 is a diagram showing the configuration of the temperature compensation system of the optical signal processing device when the optical path changing means does not have a thermo-optic action. The optical signal processing apparatus shown in FIG. 1 is configured as an optical function module 18. An AD converter 8 that receives a signal from the temperature sensor 7, a CPU 9, and a motor driver 10 are connected to the outside of the optical function module 18. Has been. The optical functional module 18 further includes an angle variable mechanism 11 including a motor for adjusting the orientation of the glass parallel plate 4 with respect to the optical path (z axis).

  The temperature detection signal from the temperature sensor 7 is converted into a digital signal by the AD converter 8. The CPU 9 gives a driver control signal to the motor driver 10 in order to set the direction of the glass parallel plate 4 to a predetermined angle based on the temperature detection digital signal. The operation amount of the rotation mechanism 11 is determined by the driver control signal, and the glass parallel plate 4 is set to a predetermined inclination angle.

  The AD converter 8 and the CPU 9 show an exemplary configuration for performing temperature compensation control with a digital signal, and are not limited to this. The CPU need not be included as long as it is a control mechanism that can control the angle of the glass parallel plate 4 based on the detection signal and detection information from the AWG1 temperature detection means. Needless to say, control using an analog signal may be used.

  FIG. 3 is a diagram exemplarily showing the configuration and operation of an angle variable mechanism including a motor. FIG. 3A shows a simplified configuration, in which the upper diagram is a top view of the AWG demultiplexing surface as viewed vertically, and the lower diagram is a side view of the AWG substrate as viewed from the thickness direction. . The rotational motion of the motor 12 is transmitted to the screw 13 and converted into a linear motion of the split nut 14 mechanically interlocking with the screw 13. The split nut 14 is connected to the glass parallel plate 4 and the movable shaft 19. The glass parallel plate 4 can be rotated around the rotation axis 15, and the direction thereof can be set at a predetermined inclination angle with respect to the optical axis (z axis in FIG. 1). FIG. 3b shows an operation of rotating the glass parallel plate 4 counterclockwise by displacing the split nut 14 to the right at a high temperature. FIG. 3c shows the operation of rotating the glass parallel plate 4 clockwise by displacing the split nut 14 leftward at a low temperature. This configuration shows an exemplary configuration for rotating the glass parallel plate 4. Therefore, various forms of rotation mechanisms are possible and are not limited to this configuration. Note that the motor 12 is not necessarily required and other actuators can be utilized.

  FIG. 4 is a diagram exemplarily showing the configuration and operation of another angle variable mechanism. FIG. 4A shows a simplified configuration, in which the upper diagram is a top view of the AWG demultiplexing surface as viewed vertically, as in FIG. 1, and the lower diagram is a side view of the AWG substrate as viewed from the thickness direction. . The bimetal 16 fixed to the base 17 is mechanically connected to the glass parallel plate 4 at the movable shaft 19. The glass parallel plate 4 can be rotated around the rotation axis 15, and the direction thereof can be set at a predetermined inclination angle with respect to the optical axis (z axis in FIG. 1). FIG. 4 b shows an operation in which the bimetal 16 is displaced rightward at a high temperature and the glass parallel plate 4 is rotated counterclockwise. FIG. 4c shows an operation of conversely displacing the bimetal 16 leftward at a low temperature and rotating the glass parallel plate 4 clockwise.

  In the variable angle mechanism using the bimetal shown in FIG. 4, the temperature detection function and the feedback control function are realized by the operation of the bimetal itself. Therefore, the temperature sensor 7 shown in FIG. 1 is unnecessary. Furthermore, it should be noted that the AD converter 8, the CPU 9, and the motor driver 10 shown in FIG. 2 are unnecessary. Next, the most important mechanism in the optical signal processing apparatus of the present invention will be described in more detail about the mechanism for temperature compensation of the temperature dependence of the spectral characteristics of the AWG by the optical path changing means (glass parallel plate) 4.

  FIG. 5 is a diagram showing the optical axis moving action of the glass parallel plate and the relationship between the temperature and the required inclination angle. FIG. 5 a is a diagram for explaining parameter definitions of the glass parallel plate. The z-axis direction in FIG. 5a corresponds to the z-axis direction in FIG. The optical signal that has passed through the condenser lens travels rightward along the z-axis along the optical paths 20a, 20b, and 20c toward the signal processing element. The optical path can be moved in the x-axis direction by the glass parallel plate 4. Element elements of signal processing elements are arranged in the x-axis direction. By moving the glass parallel plate 4 in the x-axis direction while keeping the optical axis parallel to the z-axis together with the temperature, the focal point misalignment caused by the temperature dependence of the spectral characteristics of the spectroscopic element such as AWG is reduced. Can be compensated.

  As shown in FIG. 5a, when the inclination angle formed between the incident plane of the glass parallel plate and the normal direction of the z axis of the optical signal is θ, the movement amount Δxp of the optical axis by the glass parallel plate is expressed by the following equation. Is done.

Here, n1 is the refractive index outside the glass parallel plate, n2 is the refractive index of the glass parallel plate, and t is the thickness of the glass parallel plate. Usually, in the case of a spatially coupled optical signal processing apparatus, n1 = 1. As can be seen from Equation 1, an arbitrary optical axis movement amount Δxp can be obtained by determining the material (refractive index) and thickness t of the glass parallel plate and changing the tilt angle θ. By controlling the inclination angle θ together with the temperature in accordance with the temperature dependence of the spectral characteristics of the AWG, it is possible to compensate for the deviation of the focal point position on the signal processing element.

For example, consider the case of an AWG with the following configuration parameters. The center wavelength is 1587.04 nm, the optical path length L of the arrayed waveguide is 30.54 μm, the distance d of the arrayed waveguide is 12 μm, the focal length f of the condenser lens is 50 mm, the group refractive index ng is 1.48, and the waveguide equivalent refractive index nc Is 1.45, and the thermo-optic constant (dn / dT) of the quartz glass is 1.1 × 10 ⁻⁵ . At this time, the shift amount of the condensing position on the signal processing element accompanying the temperature variation of the AWG is expressed by the following equation.

In the case of the above parameter values, Δx _A = 1.43 (μm / ° C.). By making the shift amount Δx _{A of the} condensing position obtained from Equation 2 coincide with the movement amount Δxp of the optical axis obtained from Equation 1, the deviation between the actual condensing position and the position of the element element of the signal processing element can be reduced. Can be offset.

FIG. 5b is a diagram showing the relationship between temperature and required tilt angle. The relationship between the temperature and the required inclination angle θ when the thickness t of the glass parallel plate is 3.2 mm, n2 = 2.4 (titanium dioxide TiO ₂ ), n1 = 1, and the temperature T = 45 ° C. is the reference temperature. Is shown. The inclination angle θ can be set by rotating the glass parallel plate by the angle control mechanism of the glass parallel plate shown in FIGS.

  Further, according to the analysis, the insertion loss of the parallel plate is 0.1 dB or less, which is a significant improvement effect of the loss as compared with the loss of 1 dB in the conventional temperature dependence compensation method of forming grooves in the arrayed waveguide. was gotten.

“Second Example”:
In the optical signal processing apparatus described so far, the case where the optical path changing means arranged in the spatial optical system, for example, a glass parallel plate, has no thermo-optic action has been described. That is, the configuration is such that the inclination angle with respect to the optical axis of the optical path changing means itself is changed by using mechanical means so as to compensate for the temperature dependence of the spectral characteristics of the AWG. However, when the optical path changing means itself has thermo-optical characteristics, temperature compensation can also be performed using the refractive index temperature dependent characteristic of the optical path changing means itself.

  FIG. 6 is a diagram for explaining the effect of compensation by the thermo-optic effect of the parallel plates. As can be understood from Equation 1, when the refractive index n2 of the parallel plate material changes with temperature due to the thermo-optic effect, the temperature change of the refractive index n2 can be used for temperature compensation. It is possible to compensate for the deviation of the focal point position caused by the temperature dependence of the spectral characteristics of a spectral element such as AWG.

The configuration of the AWG is the same as in the first embodiment, the center wavelength is 15870.43 nm, the arrayed waveguide optical path length L is 30.54 μm, the arrayed waveguide interval d is 12 μm, the condenser lens focal length f is 50 mm, the group The refractive index ng is 1.48, the waveguide equivalent refractive index nc is 1.45, and the thermo-optic constant (dn / dT) of quartz glass is 1.1 × 10 ⁻⁵ .

For example, the inclination angle θ of the parallel plate is 30 °, and the thickness t of the parallel plate is 36.5 mm. Here, the parallel plate material is an optical polymer, and the thermo-optic constant is dn2 / dT = −1.6 × 10 ⁻⁴ . FIG. 6 shows the temperature characteristics of the residual wavelength shift amount with and without a parallel plate when the temperature T = 45 ° C. is used as the reference temperature. In the case of the present embodiment, the allowable amount of center wavelength shift allowed in WDM communication with a 100 GHz channel interval is 5 GHz. When there is no parallel plate, the maximum wavelength shift amount accompanying the temperature change reaches 60 GHz. However, by inserting the parallel plate, the wavelength shift amount can be significantly reduced to 3 GHz.

  Similar to the first embodiment, according to the analysis, the insertion loss of the parallel plate is 0.1 dB or less, and compared with the loss of 1 dB in the conventional temperature dependence compensation method of forming grooves in the arrayed waveguide, A significant improvement in loss was obtained.

  It should be noted that the temperature sensor 7 and the rotation mechanism 11 shown in FIG. Further, the AD converter 8, the CPU 9, and the motor driver 10 are unnecessary.

“Third embodiment”:
In each of the embodiments described above, the optical path conversion element is arranged between the condenser lens and the signal processing element. On the other hand, the optical path conversion element can be disposed between the AWG and the condenser lens. In this case, the optical path conversion element operates to directly compensate the temperature of the spectral angle of the AWG itself.

  FIG. 7 is a diagram showing the configuration of the optical signal processing apparatus according to the third embodiment of the present invention. The optical signal processing apparatus of the present embodiment also has a reflection type configuration that includes a mirror and inputs and outputs an optical signal by one spectroscopic element. The configuration of the present embodiment is different from the configurations of the prior art and the first embodiment in that the optical path conversion means 21 is provided in the spatial optical system between the AWG 1 and the condenser lens 3. Furthermore, the optical path changing means 21 is characterized in that it acts as a temperature compensating means. The basic configuration and operation of the optical signal processing apparatus are the same as those of the optical signal processing apparatus described with reference to FIG.

  In the present embodiment, a temperature sensor on the AWG is not necessary, and temperature compensation is performed using the thermo-optic effect of the optical path changing means 21. Next, the case where a wedge plate is used as the optical path changing means will be described in more detail.

  FIG. 8 is a view for explaining the structure and arrangement method of the wedge plate in the optical signal processing apparatus of the present invention. The wedge plate 21 has a predetermined apex angle θ and is arranged so that the apex direction coincides with the short waveguide side of the AWG arrayed waveguide. Here, it is assumed that the thermo-optic constant of the wedge plate and the thermo-optic constant of the material constituting the AWG have opposite signs. The z-axis direction in FIG. 8a corresponds to the z-axis direction in FIG. The optical signal emitted from the AWG travels rightward along the z-axis along the optical paths 20a, 20b, and 20c toward the condenser lens. The wedge plate 21 can change the direction of the optical path with respect to the z-axis direction. This is the same as changing the angle of emission from the AWG itself. By changing the direction of the optical path with respect to the z-axis direction together with the temperature by using the wedge plate 4, it is possible to compensate for the deviation of the focal point position due to the temperature dependence of the spectral characteristics of the spectral element such as AWG.

  In FIG. 8a, the wedge plate 21 is shown as being arranged so that the incident surface and the exit surface of the optical signal are symmetric with respect to the x axis as the axis of symmetry. However, the direction of the wedge plate 21 is not limited to this direction. As shown in FIG. 8b, the entire wedge plate 21 may be tilted as long as the optical signal passes through the wedge plate so that the apex angle coincides with the short waveguide side of the array waveguide having the AWG. Do not place it in the orientation shown in FIG. However, it should be noted that if the signs of the thermo-optic constant of the wedge plate and the thermo-optic constant of the material constituting the AWG are the same, it must be arranged as shown in FIG.

  Here, the temperature fluctuation amount of the dispersion angle accompanying the AWG temperature fluctuation is expressed by the following equation.

Specifically, considering the same AWG configuration parameters as in the first embodiment, Δθ _A = 2.86 × 10 ⁻⁵ (rad / ° C.).

On the other hand, the incident angle of the optical signal with respect to the z-axis is θ _i , the outgoing angle of the optical signal with respect to the z-axis is θ _o , the apex angle of the wedge plate is θ, and the refractive index of the wedge plate is n2. At this time, the following relationship is established between θ _i and θ _o .

When the refractive index n2 of the material of the wedge plate changes with temperature due to the thermo-optic effect, the temperature change of the refractive index n2 can be used for temperature compensation. Variation in the emission angle due to the temperature dependence of the spectral characteristics of the AWG can be compensated for by the thermo-optic change of the refractive index n2. For example, when the apex angle θ of the wedge plate is 10.26 ° and the thermo-optic constant of the wedge plate is dn2 / dT = −1.6 × 10 ⁻⁴ , the temperature dependence of the dispersion angle represented by Equation 3 is obtained. Can be compensated.

  Further, according to the analysis, the insertion loss of the wedge plate is 0.1 dB or less, and a significant improvement effect of the loss compared with the loss of 1 dB in the conventional temperature dependence compensation method of forming grooves in the arrayed waveguide. was gotten.

“Fourth embodiment”:
An electro-optic crystal can be used as another method for performing temperature compensation using an optical path changing means arranged in the spatial optical system. By applying an appropriate voltage to the electro-optic crystal, its optical characteristics can be changed. Therefore, temperature compensation can be performed by controlling the refractive index with temperature.

  FIG. 9 is a diagram showing a configuration of an optical signal processing device according to the fourth embodiment of the present invention. The optical signal processing apparatus of the present embodiment also has a reflection type configuration that includes a mirror and inputs and outputs an optical signal by one spectroscopic element. The configuration of the present embodiment is different from the configurations of the prior art and the first embodiment in that the spatial optical system between the AWG 1 and the condenser lens 3 is provided with the optical path changing means 30. The optical path conversion means 30 is characterized in that it acts as a temperature compensation means. The basic configuration and operation of the optical signal processing apparatus are the same as those shown in FIG.

  In this embodiment, the electro-optic crystal 30 is used as the optical path changing means 30. Two wedge-shaped electrodes 30 and 31 facing the upper and lower surfaces of the electro-optic crystal 30 are formed so as to be parallel to the demultiplexing surface by the AWG 1. By applying a voltage to the wedge-shaped electrodes 30 and 31, the refractive index of the region in the electro-optic crystal between the electrodes can be changed.

  FIG. 10 is a block diagram showing a temperature compensation system including an optical signal processing device according to the fourth embodiment of the present invention. When an electro-optic crystal is used, the temperature sensor 7 on the AWG is required as temperature detecting means, as in the case of the first embodiment. The optical signal processing device shown in FIG. 9 is configured as an optical function module 38, and an AD converter 8 that receives a signal from the temperature sensor 7, a CPU 9, and a high voltage generator 35 are provided outside the optical function module 38. Is connected.

  The temperature detection signal from the temperature sensor 7 is converted into a digital signal by the AD converter 8. The CPU 9 gives a control signal to the high voltage generator 35 in order to apply a predetermined voltage to the electro-optic crystal 30 based on the temperature detection digital signal. The applied voltage from the high voltage generator 35 is determined by the control signal. This applied voltage across the electrodes 30 and 31 of the electro-optic crystal causes a change in the refractive index of the electro-optic crystal that compensates for the temperature dependence of the spectral angle of the AWG.

Examples of the electro-optic crystal include K _1-y Li _y Ta _1-x Nb _x O ₃ (0 <x <1, <y <1), LiNbO ₃ , LiTaO ₃ , LiIO ₃ , KNbO ₃ , KTiOPO ₄ , BaTiO ₄ . ₃ , SrTiO ₃ , Ba _1-x Sr _x TiO ₃ (0 <x <1), Ba _1-x Sr _x Nb ₂ O ₆ (0 <x <1), Sr _0.75 Ba _0.25 Nb ₂ O ₆ , Pb _{1 -y La y Ti 1-x Zr} x O 3 (0 <x <1, <y <1), Pb (Mg 1/3 Nb 2/3) O 3 -PbTiO 3, KH 2 PO 4, KD 2 PO ₄ , (NH ₄ ) H ₂ PO ₄ , BaB ₂ O ₄ , LiB ₃ O ₅ , CsLiB ₆ O ₁₀ , GaAs, CdTe, GaP, ZnS, ZnSe, ZnTe, CdS, CdSe, ZnO, and the like.

FIG. 11 is a diagram showing the relationship between temperature and the required applied voltage to the electro-optic crystal. This figure shows the required applied voltage at each temperature when LiNbO ₃ is used as the electro-optic crystal, the thickness (y direction) of the electro-optic crystal is 0.5 mm, and the apex angle of the wedge-shaped electrode is 30 °. The temperature dependence of the spectral angle of the AWG to be compensated is the same as in the third embodiment.

Further, according to the analysis, the insertion loss of LiNbO ₃ is 0.2 dB or less, which is a significant improvement effect of the loss compared to the loss of 1 dB in the conventional temperature dependence compensation method for forming the groove in the arrayed waveguide. was gotten.

"5th Example":
FIG. 12 is a diagram showing a configuration of an optical signal processing device according to the fifth embodiment of the present invention. This example is another embodiment using an electro-optic crystal. As the electro-optic crystal, potassium tantalate niobate KTa _1-x Nb _x O (hereinafter referred to as KTN) is used. Compared with the fourth embodiment, the basic configuration and operation as an optical signal processing device are the same except that the type of electro-optic crystal and the arrangement of electrodes are different. It is known that KTN can freely scan a light beam by inducing a refractive index distribution that changes in the electrode direction by applying a voltage between two electrodes arranged in a crystal. Depending on this refractive index distribution, the optical signal incident on the KTN can be deflected in the x-axis direction.

  The electro-optic crystal 30 made of KTN is a rectangular parallelepiped having a length L in the z-axis direction and a width W in the x-axis direction. The electrodes 33 and 34 are disposed facing each other in the zy plane. A voltage is applied to KTN in the x-axis direction.

  FIG. 13 is a diagram showing the relationship between temperature and the required applied voltage to the KTN crystal. The required applied voltage between the electrodes 33 and 34 when the width W (x-axis direction) of the electro-optic crystal is 1 cm and the length L is 6 mm is shown. The temperature dependence of the spectral angle of the AWG to be compensated is the same as that of the third embodiment.

  Further, according to the analysis, the insertion loss of the KTN crystal is 0.2 dB or less, and the loss is greatly improved compared to the loss of 1 dB in the conventional temperature dependence compensation method of forming grooves in the arrayed waveguide. was gotten.

“Sixth embodiment”:
The optical signal processing device described so far has a configuration including a condenser lens. However, even in the case of an optical signal processing device that does not include a condensing lens, it is possible to compensate for the deviation of the condensing point position caused by the temperature dependence of the spectral characteristics of a spectral element such as an AWG. Here, an example of an optical signal processing apparatus using a phase modulation element as a signal processing element will be described.

  FIG. 14 is a diagram for explaining the configuration and operation of a wavelength selection filter using a phase modulation element such as a liquid crystal according to a sixth embodiment of the present invention. Referring to FIG. 14a, a plurality of optical signals having different wavelengths are emitted from the AWG 1 in the z-axis direction at emission angles corresponding to the wavelengths. The phase modulation element 5 is combined with the mirror 6 and operates as a wavelength selection filter. The phase modulation element 5 operates as a variable prism that can reflect only an optical signal incident at a specific incident angle in the same direction. For example, the phase modulation element 5 can apply a different voltage stepwise to each pixel of the liquid crystal element to give a smooth phase change equivalent to a prism. FIG. 14 b conceptually shows the amount of phase change given by the phase modulation element. A wavelength selective filter can be configured by combining the AWG 1 and the liquid crystal element 5. Even in the case of such a wavelength selection filter, temperature variation occurs in the wavelength selection characteristics due to the temperature dependence of the spectral characteristics of the AWG 1 and the temperature dependence of the phase modulation characteristics of the phase modulation element 5.

  FIG. 14C is a configuration diagram of an optical signal processing device in which the present invention is applied to a wavelength selection filter. The optical path conversion element 21 is inserted in the optical path between the AWG 1 and the phase modulation element 5. As the optical path conversion element, a thermo-optic effect can be used as in the third embodiment described, or an electro-optic crystal can be used as in the fourth or fifth embodiment.

  For example, in the case of a wedge plate configuration using the thermo-optic effect, according to the analysis, the insertion loss of the wedge plate is 0.1 dB or less, and the conventional temperature dependence compensation method for forming grooves in the arrayed waveguide is used. Compared with the loss of 1 dB, a significant improvement effect of the loss was obtained.

“Seventh embodiment”:
FIG. 15 is a diagram for explaining the configuration and operation of an optical signal processing apparatus according to the seventh embodiment of the present invention. The optical signal processing apparatus described above has a configuration in which temperature compensation is performed by an optical path changing unit arranged in a spatial optical system. Here, paying attention to the light collection position of the signal processing element, temperature compensation can also be performed by moving the position of the signal processing element relative to other optical system components.

  FIG. 15b is a diagram showing the amount of movement due to the temperature of the condensing point, based on the temperature fluctuation amount of the dispersion angle represented by the above equation (3). If the position of the signal processing element is moved in conjunction with the amount of movement, the condensing point can always be condensed on a predetermined element of the signal processing element.

  FIG. 15a is a diagram showing a configuration of an optical signal processing device according to the seventh embodiment of the present invention. The basic configuration is the same as in the first embodiment, and the signal processing element 5 is fixed to the movable stage 40. The movable stage 40 is moved by the motor 12, for example, via the movable mechanism 41. Can be moved. The signal processing element 5 fixed to the movable stage 40 is moved relative to other optical system elements including the AWG 1 and the lens 3 in the direction of the axis of intersection between the wave separation plane of the AWG 1 and the signal processing element 5. be able to. Thereby, even if there is a temperature variation in the spectral characteristics, the optical signal is condensed at a predetermined fixed position in the signal processing element. The configuration form of the movable stage is not limited to the configuration of the present embodiment. For example, a configuration in which the position of the AWG is moved may be used. As long as the relative position between the signal processing element and the AWG can be varied, any one may be used. The overall temperature compensation system including the temperature detecting means is exactly the same as that of the configuration of FIG. 2, and detailed description thereof is omitted.

  In this case, it is not necessary to insert components such as a wedge plate, a parallel plate, and an electro-optic crystal in the optical path as in the previous embodiment. Therefore, in this embodiment, excessive loss does not occur due to temperature compensation.

  In each of the above embodiments, the optical signal processing apparatus having the reflection type configuration has been described as an example. However, it goes without saying that the present invention is not limited to the reflection type configuration. That is, the present invention can also be applied to an optical signal processing apparatus having a transmission type configuration or a configuration including a plurality of emission systems or incident systems.

  As described above, according to the present invention, the temperature variation of the optical signal processing apparatus caused by the temperature dependence of the spectral characteristics of the AWG is compensated for temperature in the spatial optical system, so that a simpler and lower cost method is possible. Can be made temperature-independent. The optical coupling loss in the spatial optical system of the optical signal processing device can be greatly reduced over a wide temperature range. Due to the temperature compensation action in the spatial optical system, sufficient temperature independence of the optical characteristics can be realized with a simpler configuration than the prior art. The temperature compensation in the AWG element itself becomes unnecessary, the AWG manufacturing process is simplified, and the cost of the entire optical signal processing apparatus is reduced.

  It can be used for an optical signal processing device used for optical communication. It can be applied to wavelength blockers, wavelength equalizers, wavelength tunable filters, dispersion compensators, and so on.

It is a block diagram of the optical signal processing apparatus which concerns on 1st Example of this invention. It is a figure which shows the temperature compensation system containing the optical signal processing apparatus of this invention. It is a figure explaining the structure and operation | movement of an inclination angle control mechanism. It is a figure explaining the structure and operation | movement of another inclination-angle control mechanism. It is a figure which shows the relationship between the optical axis moving effect | action of a glass parallel plate, temperature, and a required inclination angle. It is a figure explaining the effect of the temperature compensation by the thermo-optic effect in the optical signal processing apparatus which concerns on 2nd Example of this invention. It is a block diagram of the optical signal processing apparatus which concerns on the 3rd Example of this invention. It is a figure explaining the structure and arrangement | positioning method of a wedge board. It is a block diagram of the optical signal processing apparatus which concerns on the 4th Example of this invention. It is a figure which shows the temperature compensation system containing the optical signal processing apparatus which concerns on the 4th Example of this invention. It is a figure which shows the relationship between temperature and the required applied voltage to an electro-optic crystal. It is a block diagram of the optical signal processing apparatus which concerns on the 5th Example of this invention. It is a figure which shows the relationship between temperature and the required applied voltage to a KTN crystal | crystallization. It is a block diagram of the optical signal processing apparatus which concerns on the 6th Example of this invention. It is a figure explaining the block diagram and stage control amount of the optical signal processing apparatus which concerns on the 7th Example of this invention. It is a notional block diagram of the conventional optical signal processing apparatus.

Explanation of symbols

1, 51 AWG (spectral element)
2 Cylindrical lens 3, 52 Condensing lens 4 Parallel plate (optical path changing means)
5, 53 Signal processing element 6, 54 Mirror 7 Temperature sensor 8 AD converter 9 CPU
DESCRIPTION OF SYMBOLS 10 Motor driver 11 Angle variable mechanism 12 Motor 16 Bimetal 21 Wedge board (optical path conversion means)
30 Electro-optic crystal 31, 32, 33, 34 Electrode 35 High voltage generator 40 Movable stage

Claims (9)

In an optical signal processing device that splits an optical signal into a plurality of optical signals of different wavelengths and performs signal processing on the optical signals of each wavelength,
A spectroscopic means for splitting a plurality of optical signals having different wavelengths at an emission angle according to the wavelength of the optical signal;
Signal processing means for modulating the optical signal emitted from the spectroscopic means;
An optical path conversion unit that is disposed in an optical path between the spectroscopic unit and the signal processing unit and refracts the optical path of the optical signal so as to cancel the temperature dependence of the emission angle from the spectroscopic unit. An optical signal processing apparatus comprising: refracting an optical path of the optical signal.   The exit angle of the optical signal from the optical path changing means is changed so as to cancel out the temperature dependence of the outgoing angle of the spectroscopic means by the refractive index temperature dependency characteristic of the optical path changing means. Item 4. The optical signal processing device according to Item 1.   3. The light according to claim 2, wherein an emission angle of the optical signal from the optical path conversion unit is changed using a thermo-optic effect or an electro-optical effect of the optical path conversion unit as the refractive index temperature dependent characteristic. Signal processing device. In an optical signal processing device that splits an optical signal into a plurality of optical signals of different wavelengths and performs signal processing on the optical signals of each wavelength,
A spectroscopic means for splitting a plurality of optical signals having different wavelengths at an emission angle according to the wavelength of the optical signal;
Condensing means for condensing the optical signal emitted from the spectroscopic means;
Signal processing means for modulating the optical signal collected by the light collecting means;
An optical path conversion unit arranged in one of the optical paths between the spectroscopic unit and the condensing unit or between the condensing unit and the signal processing unit, and refracts the optical path of the optical signal; An optical signal processing apparatus comprising: refracting an optical path of the optical signal so as to cancel temperature dependence of the emission angle from the spectroscopic means. Driving means for changing an inclination angle of the light path conversion means arranged in the optical path between the light collecting means and the signal processing means with respect to a main optical path axis of the light collecting means;
Temperature detecting means for detecting the temperature of the spectroscopic means,
5. The condensing point position of the optical signal in the signal processing means is changed by changing the tilt angle by the driving means based on the temperature detected by the temperature detecting means. 2. An optical signal processing device according to 1.   Using the thermo-optic effect of the optical path conversion means arranged in the optical path between the condensing means and the signal processing means, the condensing point position of the optical signal in the signal processing means is changed. The optical signal processing device according to claim 4.   The optical signal processing apparatus according to claim 5 or 6, wherein the optical path conversion means arranged in an optical path between the light collecting means and the signal processing means is a glass parallel plate.   Using the thermo-optic effect or electro-optic effect of the optical path changing means arranged in the optical path between the spectroscopic means and the light collecting means, the emission angle of the optical signal from the optical path changing means is changed. The optical signal processing apparatus according to claim 4, wherein: In an optical signal processing device that splits an optical signal into a plurality of optical signals of different wavelengths and performs signal processing on the optical signals of each wavelength,
A spectroscopic means for splitting a plurality of optical signals having different wavelengths at an emission angle according to the wavelength of the optical signal;
Signal processing means for modulating the optical signal emitted from the spectroscopic means;
The relative position of the spectroscopic means and the signal processing means is connected to either the spectroscopic means or the signal processing means, and the crossing axis direction of the demultiplexing surface of the spectroscopic means and the signal processing means is An optical signal processing apparatus comprising: a movable means for changing, wherein the position of any one of the two is changed so as to cancel out the temperature dependence of the emission angle from the spectroscopic means.

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