JP5906300B1 - Spatial phase modulator - Google Patents

Abstract

To provide a spatial phase modulator capable of suppressing occurrence of crosstalk to other ports due to a phase pattern switching operation. In the present invention, when a phase pattern formed on a phase modulation element is switched from an initial pattern to a final pattern, an intermediate pattern is created and switched from the initial pattern to the intermediate pattern and the final pattern at predetermined time intervals. When the phase pattern of the phase modulation element is switched from the initial pattern to the final pattern, an intermediate pattern corresponding to the pattern in the process of changing from the initial pattern to the final pattern is generated, and the initial pattern is switched to the intermediate pattern and the final pattern. Thus, the phase control value change amount and phase control value change speed in one phase pattern switching are controlled. As a result, unintended distortion of the phase pattern due to phase pattern switching can be suppressed, and crosstalk due to higher-order light can be suppressed. [Selection] Figure 7

Description

  The present invention relates to a spatial phase modulator that controls a path and light intensity of output light using a phase modulation element.

  In recent years, with the increase in Internet traffic, the need for an increase in communication capacity in optical fiber communication is further increased. An optical switch is a technology that is attracting attention as a routing function device for optical fiber communication. Among optical switches, a spatial optical system optical switch that switches a light path in free space is superior to other systems from the viewpoint of high-density mounting and power consumption reduction, and technological development is progressing in recent years.

  The basic configuration of the spatial optical system optical switch will be described. In general, a spatial optical system optical switch is composed of several lenses and a light beam deflecting element arranged in a free space between an input fiber and an output fiber to change the traveling direction of the light beam. Typical optical switches include an input / output fiber array and a collimating lens array, an optical cross-connect switch (OXC) composed of two sets of light beam deflection elements, an input / output fiber array and a collimating lens array, a lens group, and a dispersion. There is a wavelength selective switch (WSS) composed of elements and beam deflection element groups.

  Such a spatial optical system optical switch has a high degree of freedom in wiring in space, but cannot confine light by a fiber or the like, so that unintentional leakage of light outside the target output port becomes a problem. In particular, in an optical switch having a configuration in which a plurality of output ports are arranged, leakage of light to adjacent output ports causes signal quality degradation as crosstalk, which is an extremely important technical development item.

  One of the functions of the optical switch is an optical attenuation function that controls the optical intensity of the output port. As an optical attenuation function in the spatial optical system optical switch, there is a method of individually attaching an optical attenuator at the subsequent stage of each output port. However, as the number of output ports increases, cost and size increase. Therefore, a method of adding the function to the light beam deflecting element in the optical switch can be considered.

  When an attenuation function is added to the light beam deflecting element, the problem is how to suppress the above-described crosstalk. As the light beam deflecting element, Micro Electro Mechanical Systems (MEMS) or Liquid Crystal on Silicon Spatial Light Modulator (LCOS-SLM) is used.

  As a method for adding an attenuation function, for example, Non-Patent Documents 1 and 2 describe a method of periodically returning a phase and a means for realizing the method. By superimposing a periodic phase pattern on the light beam deflecting element, the light intensity can be dispersed in an angular direction corresponding to the period. The power of the dispersed light can be controlled by selecting the amplitude of the phase pattern to be superimposed, and thereby optical attenuation by spatial phase modulation is possible.

T. Fujita et al, "Blazed grating and Fresnel lensen fabricated by electron-beam lithography", OPTICS LETTERS, Vol.7, No.12, pp.578-580, December 1982. R. Magnusson et al, "Diffraction efficiencies of thin phase gratings with arbitrary grating shape", J. Optical Society of America, Vol.68, No.6, pp.806-809, June 1978.

  FIGS. 21A and 21B show a schematic diagram of a configuration of a spatial phase modulator using a conventional LCOS-SLM and a phase pattern of the LCOS-SLM.

As shown in FIG. 21 (a), when the phase pattern of the LCOS-SLM113 form a desired pattern, the input light incident from the input port 111 ₂ is incident on the LCOS-SLM113 through the optical element 112 , it is reflected while being deflected in accordance with the phase pattern LCOS-SLM113, is output from the output port 111 ₃ via the optical element 112.

  As described above, when the LCOS-SLM is used as the light beam deflecting element, it is necessary to change the phase pattern of the LCOS-SLM by controlling the phase of each pixel by a driving circuit in order to perform deflection and attenuation operations. At this time, as shown in FIG. 21 (b), unintended phase pattern distortion occurs due to the phase pattern switching operation, and the higher-order light deflected by the distorted phase pattern is crosstalk to the outside of the target output port. There was a problem of becoming.

  The crosstalk due to the distortion of the phase pattern becomes more prominent as the phase change of the phase pattern applied to the LCOS-SLM, which is a phase modulation element, is larger, especially when a short-period phase pattern is superimposed to perform an attenuation operation. It becomes a problem. Similarly, the occurrence of crosstalk becomes a problem when switching between ports.

  The present invention has been made to solve such problems, and an object of the present invention is to provide a spatial phase modulator capable of suppressing the occurrence of crosstalk to other ports accompanying a phase pattern switching operation. .

In order to solve the above problems, the present invention is a spatial phase modulator, in which one or more input ports for inputting / outputting optical signals and one or more output ports are arranged in a matrix in a plane. The incident light having a plurality of pixels and spatially phase-modulated by giving a phase control value according to each pixel position to the incident light input from the input port through the optical system element, and the emitted light after modulation By applying a drive signal indicating a phase pattern consisting of a phase control value for each pixel position and a phase modulation element that emits in the angular direction of the target output port specified among the output ports to the pixels, a drive circuit for controlling the emission angle and the light intensity of the outgoing light by the spatial phase modulation, when switching the phase pattern from the first phase pattern to the second phase pattern, before Light intensity values of the target output port takes a value between the light intensity value at the target output port in the optical intensity value and the second phase pattern at the target output port of the first phase pattern M intermediate phase patterns (M is an integer equal to or greater than 1) are created . Further, when the intermediate phase pattern compares the amount of crosstalk coupled to an output port other than the target output port between the intermediate phase patterns. In the region where the crosstalk amount is relatively large, the intermediate phase pattern is created so that the difference between the light intensity values at the target output ports of the front and rear phase patterns is small, and the crosstalk amount is relatively small in creating the intermediate phase pattern so that the difference in light intensity value at the target output port of the intermediate phase pattern before and after increase, or the first phase pattern The via an intermediate phase pattern for controlling said drive circuit to switch to the second phase pattern, characterized in that a control circuit.

The invention according to claim 2 is a spatial phase modulator comprising one or more input ports and one or more output ports for inputting and outputting an optical signal, and a plurality of pixels arranged in a matrix in a plane. The incident light input from the input port via the optical system element is spatially phase-modulated by giving a phase control value according to each pixel position, and the output light after the modulation is output to the output port. By applying to each pixel a phase modulation element that emits in the angle direction of the designated target output port and a drive signal indicating a phase pattern consisting of a phase control value for each pixel position. A drive circuit that controls an emission angle and light intensity of the emitted light, and the first and second phase patterns when the phase pattern is switched from the first phase pattern to the second phase pattern. A control circuit for creating M (M is an integer equal to or greater than 1) intermediate phase patterns based on the phase pattern of the first phase pattern to the second phase pattern via the intermediate phase pattern A control circuit for controlling the drive circuit to switch , wherein the control circuit alternately arranges the first region of the first phase pattern and the second region of the second phase pattern. It is characterized in that an intermediate phase pattern is created.

According to a third aspect of the invention, the spatial phase modulator according to claim 2, the boundary between the first region and the second region, the arrangement direction of the incoming and outgoing light of said input and output ports It is characterized by being perpendicular to it.

According to a fourth aspect of the invention, the spatial phase modulator according to claim 2, the boundary between the first region and the second region, the arrangement direction of the incoming and outgoing light of said input and output ports It is characterized by being parallel to each other.

According to a fifth aspect of the present invention, in the spatial phase modulator according to the second aspect , the intermediate phase pattern includes two or more first regions and two or more second regions arranged alternately. The repetition period of the first region and the second region is set so as to perform spatial phase modulation so that the incident light is emitted in a direction other than the angular direction of the output port. .

The invention according to claim 6 is the spatial phase modulator according to any one of claims 1 to 5 , wherein the switching time interval of the intermediate phase pattern is other than the target output port at the time of switching the intermediate phase pattern. When the crosstalk amounts coupled to the output ports are compared, the time when the crosstalk amount is relatively large is lengthened, and the time when the crosstalk amount is relatively small is shortened .

  The present invention has an effect of suppressing crosstalk to other ports that occurs during a phase pattern switching operation in a spatial phase modulator.

It is explanatory drawing which shows the 1st basic composition concerning the optical input / output device to which this invention is applied. It is explanatory drawing which shows the other structural example concerning a 1st basic composition. It is explanatory drawing which shows the 2nd basic composition concerning the optical input / output device to which this invention is applied. It is explanatory drawing which shows the other structural example concerning a 2nd basic composition. It is explanatory drawing which shows the structural example (single wavelength) of a phase modulation element. It is explanatory drawing which shows the structural example (WDM) of a phase modulation element. It is a figure explaining the control method of the phase modulation element in the spatial phase modulator which concerns on one Embodiment of this invention. It is a figure which shows the initial pattern and final pattern of the phase pattern of a phase modulation element. (A) shows some of the particular pixel, the phase control value of the initial pattern and the final pattern, the phase control value of the intermediate pattern in the case of dividing the difference D _C of the phase control value to evenly number of intermediate pattern (B) is a case where the number of intermediate patterns is larger than the other ranges in the phase control values of the initial pattern and the final pattern and the phase control values in the range of X to Y of a specific pixel. It is a figure which shows the phase control value of these intermediate patterns. It is a figure which shows the example of the time interval of switching of the phase pattern in the optical phase modulator which concerns on one Embodiment of this invention. It is a figure which shows the phase pattern which implement | achieves the light intensity and the each light intensity in the object output port. In the intermediate pattern when the number of intermediate patterns is larger than the other ranges in the range of the light intensity value at the target output port in the initial pattern and the final pattern and the phase control value of X to Y of a specific pixel. It is a figure which shows the light intensity value in an object output port. (A), (b) is the optical phase modulator according to the second embodiment of the present invention, the light intensity (coupling rate) of one port (Ch16) is −10 dB or more by switching the phase pattern of the phase modulation element. It is a figure which shows transition of the light intensity (coupling | bonding rate) of all the ports (Ch1-Ch16) when conducting experiment to lower to -30dB or less. It is a figure which shows a mode that the phase pattern of a certain area | region on a phase modulation element is switched from A pattern to B pattern. It is a figure which shows a mode that the phase pattern of a certain area | region on a phase modulation element is switched from an A pattern to a B pattern at unequal intervals. It is a figure which shows a mode that the phase pattern of a certain area | region on a phase modulation element is switched from A pattern to B pattern with a 1st switching method. It is a figure which shows a mode that the phase pattern of a certain area | region on a phase modulation element is switched from A pattern to B pattern by the 2nd switching method. It is a figure which shows a mode that the phase pattern of a certain area | region on a phase modulation element is switched from A pattern to B pattern by the 3rd switching method. It is a figure which shows a mode that the phase pattern of a certain area | region on a phase modulation element is switched from A pattern to B pattern by the 4th switching method. (A)-(c) is a figure which shows the example of a pattern division | segmentation whose division directions are parallel, perpendicular | vertical, and diagonal with respect to the beam steering direction. (A), (b) is the schematic of the structure of the spatial phase modulator using the conventional LCOS-SLM, and the phase pattern of LCOS-SLM.

Next, embodiments of the present invention will be described with reference to the drawings.
[Basic configuration of optical input / output device]
The optical input / output device 10 according to the present invention is an optical input / output device used in an optical fiber communication network, and has a function of controlling a path and light intensity of output light using a phase modulation element.

  First, a basic configuration of the optical input / output device 10 to which the present invention is applied will be described. The optical input / output device 10 to which the present invention is applied has the following two basic configurations depending on the type of the phase modulation element.

[First basic configuration]
First, a first basic configuration of an optical input / output device 10 to which the present invention is applied will be described with reference to FIG. FIG. 1 is an explanatory diagram showing a first basic configuration of an optical input / output device to which the present invention is applied.

  A feature of the first basic configuration is that a reflection type is used as the phase modulation element. FIG. 1 shows a first basic configuration viewed from the x-axis direction. However, the direction in which the output ports are arranged is the y-axis, the direction in which the optical signal propagates is the z-axis, and these x, y, and z axes are orthogonal to each other.

In the first basic configuration, in the free space in the optical input / output device 10, as main optical system elements, an optical fiber 11 that constitutes an input port, collimating lenses (arrays) 12, 15 ₁ to 15 _n , optical elements 13, a phase modulation element 14 and optical fibers 16 _{1 to} 16 _n constituting an output port are arranged. In addition, a drive circuit DRV that applies a drive signal to each pixel of the phase modulation element 14 is provided.

The phase modulation element 14 is composed of a reflection type phase modulation element having a plurality of pixels arranged in a plane in a matrix, and is input from an optical fiber 11 serving as an input port through optical system elements such as a collimator lens 12 and an optical element 13. with respect to the incident light, the spatial phase modulation by providing a phase control value that varies depending on the pixel position in each pixel, of the optical fiber 16 ₁ ~ 16 _n is an output port of the outgoing light obtained, It has a function of emitting light in the angular direction of the optical fiber corresponding to the designated target output port.

  Further, the drive circuit DRV applies a drive signal indicating a phase pattern representing the relationship between the pixel position and the phase control value to each pixel of the phase modulation element 14, thereby emitting light by spatial phase modulation in the phase modulation element 14. Has a function of controlling the emission angle and light intensity. The drive circuit DRV may be disposed outside the semiconductor chip on which the phase modulation element 14 is formed, or may be disposed within the semiconductor chip.

The input light (signal light) is emitted to free space through the optical fiber 11 and given to the optical element 13 through the collimator lens 12. The light emitted from the optical element 13 is reflected by the phase modulation element 14 and is again provided to the collimating lenses 12, 15 ₁ to 15 _n and the optical fibers 11, 16 _{1 to} 16 _n via the optical element 13. The output port and output light intensity of the optical signal are selected according to the phase pattern given to the phase modulation element 14.

Thereby, the optical signal reflected by the phase modulation element 14 is composed of the _first to _n- th channels (the optical element 13, the collimating lenses 12, 15 ₁ to 15 _n, and the optical fibers 11, 16 _{1 to} 16 _n. Are output at an arbitrary intensity to an arbitrary output port.

  As the optical element 13, means for changing the emission direction of the signal light so that the input light is emitted toward the phase modulation element 14 can be used. For example, a lens, a prism, or a diffraction grating can be used. .

FIG. 2 is an explanatory diagram showing another configuration example according to the first basic configuration. The signal light input to the optical input / output device 10 may be, for example, WDM (Wavelength Division Multiplexing) light that bundles wavelengths λp to λq. In this case, as shown in FIG. 2, a wavelength dispersion element 17 is arranged between the collimating lenses 12, 15 ₁ to 15 _n and the optical element 13 so that the condensing position is different for each wavelength, and the output is different for each wavelength. The port and light intensity may be selectable.

  The wavelength dispersion element 17 has diffraction performance along the x-axis direction, and irradiates light to different positions in the x-axis direction of the phase modulation element 14 according to the wavelength of the input light. The wavelength dispersion element 17 may be arranged between the optical element 13 and the phase modulation element 14 or in the middle of the plurality of optical elements 13 when the optical element 13 is composed of a plurality of optical elements. Further, the phase modulation element 17 may superimpose a phase pattern having not only a deflection function but also a lens function.

[Second basic configuration]
Next, a second basic configuration of the optical input / output device 20 to which the present invention is applied will be described with reference to FIG. FIG. 3 is an explanatory diagram showing a second basic configuration of an optical input / output device to which the present invention is applied.

  A feature of the second basic configuration is that a transmission type is used as the phase modulation element. FIG. 3 shows a second basic configuration viewed from the x-axis direction. However, the direction in which the output ports are arranged is the y-axis, the direction in which the optical signal propagates is the z-axis, and these x, y, and z axes are orthogonal to each other.

In the second basic configuration, an optical fiber 21, a collimating lens (array) 22, a first optical element 23, and a phase that constitute an input port are provided in the free space in the optical input / output device 20 as main optical system elements. A modulation element 24, a second optical element 25, collimating lenses (arrays) 26 _{1 to} 26 _n , and optical fibers 27 _{1 to} 27 _n constituting an output port are arranged. In addition, a drive circuit DRV that applies a drive signal to each pixel of the phase modulation element 24 is provided.

The phase modulation element 24 is composed of a transmission type phase modulation element having a plurality of pixels arranged in a plane in a matrix, and includes optical elements such as the collimating lens 22 and the first optical element 23 from the optical fiber 21 serving as an input port. The incident light input through the optical fiber is subjected to spatial phase modulation by giving a phase control value to each pixel according to the pixel position, and the obtained outgoing light is output from optical fibers 27 _{1 to} 27 _{n serving} as output ports. , Has a function of emitting in the angular direction of the optical fiber corresponding to the designated target output port.

  In addition, the drive circuit DRV applies a drive signal indicating a phase pattern representing the relationship between the pixel position and the phase control value to each pixel of the phase modulation element 24, thereby emitting light by spatial phase modulation in the phase modulation element 24. Has a function of controlling the emission angle and light intensity. The drive circuit DRV may be arranged outside the semiconductor chip on which the phase modulation element 24 is formed, or may be arranged in the semiconductor chip.

Input light (signal light) is emitted into free space through the optical fiber 21 and is incident on the first optical element 23 through the collimator lens 22. Light emitted from the first optical element 23 is given to the collimating lenses 26 _{1 to} 26 _n and the optical fibers 27 _{1 to} 27 _n via the phase modulation element 24 and the second optical element 25.

At this time, the optical signal is selected from the output port and the light intensity according to the phase pattern applied to the phase modulation element 24, for example, the first to n-th channels (collimating lenses 26 _{1 to} 26 _n and the optical fiber 27. _{1 to} 27 _n, and output to an arbitrary output port in an arbitrary output port.

FIG. 4 is an explanatory diagram showing another configuration example according to the second basic configuration. The input signal light may be, for example, WDM light that bundles wavelengths λp to λq. In this case, as shown in FIG. 4, the wavelength dispersion element 28 is disposed between the collimating lens 22 and the optical element 23, and the wavelength dispersion element 29 is disposed between the collimating lenses 26 _{1 to} 26 _n and the optical element 25. Thus, the condensing position may be different for each wavelength, and a different output port and light intensity may be selectable for each wavelength.

  The wavelength dispersion element 28 has diffraction performance along the x-axis direction, and irradiates light to different positions in the x-axis direction of the phase modulation element 24 according to the wavelength of the input light. The wavelength dispersion element 28 may be disposed between the optical element 23 and the phase modulation element 24 or in the middle of the plurality of optical elements 23 when the optical element 23 is composed of a plurality of optical elements. Further, the wavelength dispersion element 29 may be disposed between the phase modulation element 24 and the optical element 25 or in the middle of the plurality of optical elements 25 when the optical element 25 is composed of a plurality of optical elements. The phase modulation element 24 may have a lens function as well as a deflection function.

[Other basic configurations]
The first and second basic configurations of the optical input / output device 10 of the present invention are not limited to the configurations described above. For example, in the first and second basic configurations, the optical fibers 11, 21, 16 _{1 to} 16 _n and 27 _{1 to} 27 _n may be replaced with planar optical waveguides. Further, the planar optical waveguide may integrate the functions of the collimating lenses 12, 15 ₁ to 15 _n , 22, 26 _{1 to} 26 _n . Further, the phase modulation elements 14 and 24 may further superimpose a phase pattern having not only a deflection function but also a lens function, for example. As a result, the phase control value of the finally applied phase modulation element may not periodically change with respect to the pixel position.
In addition, the configuration example in which there is one input port and a plurality of output ports is shown, but a configuration in which there are a plurality of input ports and one or a plurality of output ports may be used. Also in this case, incident light from an arbitrary input port is output to an arbitrary output port with an arbitrary intensity by the phase pattern applied to the phase modulation element 24.

[Configuration of phase modulator]
Next, the phase modulation elements 14 and 24 used in the optical input / output device 10 of the present invention will be described in detail with reference to FIGS. FIG. 5 is an explanatory diagram showing a configuration example (single wavelength) of the phase modulation element. FIG. 6 is an explanatory diagram showing a configuration example (WDM) of the phase modulation element. 5 and 6 show the configuration when viewed from the z-axis direction of the phase modulation element.

The reflection type phase modulation element 14 includes a large number of pixels 41 _{11 to} 41 _pq arranged in a matrix on the xy plane, and a reflection section 42 arranged on the back surface. These pixels 41 _{11 to} 41 _pq have a function of performing spatial phase modulation by giving a phase control value to each pixel according to the pixel position in accordance with a drive signal from the drive circuit DRV. The transmission-type phase modulation element 24 has a configuration in which the reflection part 42 on the back surface shown in FIGS. 5 and 6 is not provided, and is basically the same as the reflection-type phase modulation element 14. Operate.

  In the optical input / output devices 10 and 20 of the present invention, when the phase modulation elements 14 and 24 are irradiated with input light having a single wavelength, the light irradiation region is within one region R as shown in FIG. Thus, by giving a specific phase pattern from the drive circuit DRV to each pixel in the region R, the wavefront of the emitted light from these elements is controlled, and the traveling direction of the emitted light and the light intensity in that direction are controlled. Control can be performed.

On the other hand, when the incident light is converted into a WDM signal and dispersed in the x-axis direction by the diffraction grating of the first optical element 23 or the wavelength dispersion elements 17 and 28, the incident area is as shown in FIG. Differently, a plurality of regions R _{1 to} R _n are obtained. In this case, different output ports and output light intensities can be set for each wavelength channel by independently controlling the phase patterns of the regions R _{1 to} R _n by the drive circuit DRV.

  The phase modulation elements 14 and 24 can be realized using LCOS, for example. In this element, the orientation direction of the liquid crystal material can be controlled by a voltage applied to the driver electrode, and thus the phase can be controlled by changing the refractive index of the liquid crystal felt by the input signal. A reflective phase modulator can be realized by using the front electrode as a transparent electrode and the back electrode as a reflective electrode. Further, by using both the front and back electrodes as transparent electrodes, a transmissive phase modulator can be realized. A material exhibiting an electro-optic effect may be used instead of the liquid crystal material.

  The phase modulation elements 14 and 24 can also be realized using a MEMS mirror. For example, by applying a voltage, a mirror corresponding to the position of each pixel is displaced in the z-axis direction, thereby changing the optical path length for each pixel and controlling the phase.

  FIG. 7 is a diagram illustrating a method for controlling a phase modulation element in a spatial phase modulator according to an embodiment of the present invention.

  In the present invention, when the phase pattern formed on the phase modulation element is switched from the initial pattern to the final pattern, an intermediate pattern is created and switched from the initial pattern to the intermediate pattern and the final pattern at predetermined time intervals. By reducing the amount of change of the phase pattern in one switching, it is possible to prevent unintended phase pattern distortion, suppress unnecessary high-order light, and prevent crosstalk.

  The intermediate pattern is created based on the initial pattern and the final pattern by a control circuit connected to the drive circuit DRV.

[Embodiment 1]
With reference to FIGS. 8 and 9, a method of controlling the phase modulation element used for controlling the light intensity in the port in the optical phase modulator according to the first embodiment of the present invention will be described.

  FIG. 8 shows an initial pattern and a final pattern of the phase pattern of the phase modulation element. First, an intermediate pattern is created from the initial pattern and the final pattern as follows.

(1) to calculate the difference D _C of the phase control value for each pixel in the initial pattern A and the final pattern B.
(2) The number M of intermediate patterns C is determined.
(3) A phase control value change amount D _C / (M + 1) is calculated by dividing the calculated phase control value difference D _C for each pixel by M + 1.
(4) An intermediate pattern C ₍₁₎ is obtained by adding the phase control value change amount D _C / (M + 1) for each pixel to the initial pattern A. The intermediate pattern C _(i) (i = 2,..., M) is obtained by adding the phase control value change amount D _C / (M + 1) for each pixel to the previous intermediate pattern C _(i−1). And

Next, the phase pattern of the phase modulation element is switched from the initial pattern A to the final pattern B via the intermediate patterns C _{(1) to} C _(M) by the drive circuit DRV at predetermined time intervals.

9A and 9B show the transition of the phase control value change amount of the created intermediate pattern. 9 (a) is of a particular pixel, the phase control value of the initial pattern and the final pattern, the phase control value of the intermediate pattern in the case of dividing the difference D _C of the phase control value to evenly number of intermediate pattern Is shown.

  On the other hand, FIG. 9B shows the case where the number of intermediate patterns is larger than the other ranges in the phase control values of the initial pattern and the final pattern and the phase control values in the range of X to Y of a specific pixel. And the phase control value of the intermediate pattern. Specified when there is a range where the phase pattern is likely to be distorted, for example, when there is a range where the LCOS liquid crystal response is slow, or when there is a phase pattern with large crosstalk to other ports even in a static state The amount of change in the phase control value between the intermediate patterns in the range can be reduced, and the number of intermediate patterns in the range can be made larger than in other ranges.

  FIG. 10 shows an example of a time interval for switching the phase pattern in the optical phase modulator according to the embodiment of the present invention. The time intervals for switching from the initial pattern to the intermediate pattern and the final pattern can all be set equal, but different time intervals can also be set individually as shown in FIG. In a pattern change region where crosstalk is difficult to occur, the time interval can be shortened and switched quickly, and in a pattern change region where crosstalk is likely to occur, the time interval can be increased and switched slowly.

  Thus, in the present invention, when the phase pattern of the phase modulation element is switched from the initial pattern to the final pattern, an intermediate pattern corresponding to a pattern in the process of changing from the initial pattern to the final pattern is generated, By switching between the intermediate pattern and the final pattern, the phase control value change amount and the phase control value change speed in one phase pattern change are controlled. As a result, unintended distortion of the phase pattern due to phase pattern switching can be suppressed, and crosstalk due to higher-order light can be suppressed.

  In the first embodiment, since the amount of change in phase control value between patterns can be minimized for each pixel, the final pattern can be transferred with a small number of intermediate patterns.

[Embodiment 2]
With reference to FIGS. 11 to 13, a method of controlling the phase modulation element used for controlling the light intensity in the port in the optical phase modulator according to the second embodiment of the present invention will be described.

  FIG. 11 shows the light intensity at the target output port and the phase pattern that realizes each light intensity. First, an intermediate pattern is created from the initial pattern and the final pattern as follows.

(1) to calculate the difference D _P between the light intensity value of the target output port in the optical intensity value and the final pattern B of the target output port in the initial pattern A.
(2) The number M of intermediate patterns C is determined.
(3) A light intensity value change amount D _P / (M + 1) is calculated by dividing the calculated light intensity value difference D _P for each pixel by M + 1.
(4) A light intensity value obtained by adding the light intensity value change amount D _P / (M + 1) to the light intensity value at the target output port in the initial pattern A is realized at the target output port, and a predetermined pattern is superimposed on the initial pattern This pattern is defined as an intermediate pattern C ₍₁₎ . The superposed pattern is, for example, a sawtooth wave, a triangular wave, a rectangular wave, or a sine wave pattern, and the period and amplitude are appropriately set with respect to the initial pattern based on the port arrangement and the light intensity value.
The intermediate pattern C _(i) (i = 2,..., M) has a light intensity value change amount D _P / into the light intensity value at the target output port in the previous intermediate pattern C _(i−1) . It is assumed that the light intensity value obtained by adding (M + 1) is realized at the target output port.

In addition to the above conditions, the intermediate patterns C _{(1) to} C _(M) may be patterns that minimize the amount of change in the light intensity value of other output ports other than the target output port.

Next, the phase pattern of the phase modulation element is switched from the initial pattern A to the final pattern B via the intermediate patterns C _{(1) to} C _(M) by the drive circuit DRV at predetermined time intervals.

The intermediate pattern may be created based on the light intensity value change amount D _P / (M + 1) obtained by equally dividing the light intensity value difference D _P by the number M of the intermediate patterns.

  On the other hand, FIG. 12 shows the light intensity value at the target output port in the initial pattern and the final pattern, and the intermediate pattern when the number of intermediate patterns is larger than the other ranges in the light intensity values in the range of X to Y. Indicates the light intensity value at the target output port. In the range of light intensity values X to Y, an intermediate pattern is shown when the number of intermediate patterns is larger than in other ranges. Specified when there is a range where the phase pattern is likely to be distorted, for example, when there is a range where the LCOS liquid crystal response is slow, or when there is a phase pattern with large crosstalk to other ports even in a static state It is also possible to reduce the amount of change in the light intensity value between the intermediate patterns in this range and increase the number of intermediate patterns in that range.

  As in the first embodiment, the time intervals for switching from the initial pattern to the intermediate pattern and the final pattern can all be set equal, but different time intervals can be set individually as shown in FIG. it can. In a pattern change region where crosstalk is difficult to occur, the time interval can be shortened and switched quickly, and in a pattern change region where crosstalk is likely to occur, the time interval can be increased and switched slowly.

  Thus, in the present invention, when the phase pattern of the phase modulation element is switched from the initial pattern to the final pattern, an intermediate pattern corresponding to a pattern in the process of changing from the initial pattern to the final pattern is generated, By switching to the intermediate pattern and the final pattern, the light intensity change amount and the light intensity value change speed in one phase pattern change are controlled. As a result, unintended distortion of the phase pattern due to phase pattern switching can be suppressed, and crosstalk due to higher-order light can be suppressed.

  FIGS. 13A and 13B show the light intensity (coupling rate) of one port (Ch16) by switching the phase pattern of the phase modulation element in the optical phase modulator according to the second embodiment of the present invention. The transition of the light intensity (coupling rate) of all ports (Ch1 to Ch16) when an experiment for reducing from 10 dB or more to −30 dB or less is shown.

  FIG. 13A shows 11 intermediate patterns, while FIG. 13B shows 101 intermediate patterns. In FIG. 13A, the maximum value of the coupling rate to other ports was −24.5 dB, whereas in FIG. 13B, the maximum value of the coupling rate to other ports was −30.3 dB. there were. By increasing the number of intermediate patterns, reducing the light intensity value change amount at one switching, and reducing the light intensity value change speed, crosstalk to other ports could be suppressed.

  In the second embodiment, since all intermediate patterns are generated based on the light intensity of the target output port in the entire pattern in a static state, generation of high-order light can be prevented.

[Embodiment 3]
With reference to FIGS. 14 and 15, a method of controlling the phase modulation element used for port switching control in the optical phase modulator according to the third embodiment of the present invention will be described.

  FIG. 14 shows how the phase pattern of a certain region on the phase modulation element is switched from the A pattern to the B pattern. In the present embodiment, when switching the phase pattern of a certain region, the entire pattern is switched gradually as shown in FIG. 14 instead of switching the entire pattern simultaneously. In FIG. 14, the area of the A pattern is divided into two parts, and each area is gradually divided into a plurality of steps from the left side to switch to the B pattern, but the area for pattern switching is divided into three or more parts. You can also

  FIG. 15 shows how the phase pattern of a certain region on the phase modulation element is switched from the A pattern to the B pattern at unequal intervals. In FIG. 14, the switching areas to be switched at the same time are arranged at equal intervals, but the switching areas can be arranged at unequal intervals. Higher order light in the intermediate pattern is affected by diffraction due to the spacing of the switching regions. Therefore, by making the intervals between the switching regions unequal, it is possible to prevent unnecessary high-order light generated by dividing the pattern from being generated at a specific location.

  A detailed procedure for switching between the two patterns will be described. As an example, a case where the switching area is divided and switched at a cycle of 5 pixels is shown.

  FIG. 16 shows how the phase pattern of a certain region on the phase modulation element is switched from the A pattern to the B pattern by the first switching method. In the first switching method, switching in each switching area in one step is set as one pixel row.

  FIG. 17 shows a state in which the phase pattern of a certain region on the phase modulation element is switched from the A pattern to the B pattern by the second switching method. In this second switching method, switching in each switching area in one step is a two-pixel column, and only the last one column is a one-pixel column.

  In addition to the examples shown in FIGS. 16 and 17, the number of pixel columns to be switched in one step can be arbitrarily designed according to the switching time and the state of generation of unnecessary high-order light.

  FIG. 18 shows how the phase pattern of a certain region on the phase modulation element is switched from the A pattern to the B pattern by the third switching method. In the third switching method, switching of each switching area is a 1-pixel row in the first, second, and fourth steps, and a 2-pixel row in the third step. In addition to the example shown in FIG. 18, a column in which unnecessary high-order light is likely to be generated by pattern switching is set to one pixel column in one step, and a column in which unnecessary high-order light is difficult to generate is set to two or more pixel columns in order to increase the switching speed. For example, the number of pixel columns to be switched at each switching step can be arbitrarily designed according to the state of generation of unnecessary high-order light.

  FIG. 19 shows how the phase pattern of a certain region on the phase modulation element is switched from the A pattern to the B pattern by the fourth switching method. In the fourth switching method, the left half area is switched by the first switching method, and the right half is switched by the second switching method. In addition to the example shown in FIG. 19, for each switching region, for example, the pixel row to be switched in one step is changed for each switching region, or the number of pixel rows to be switched for each step is changed as in the third switching method. The switching method can be arbitrarily designed. 20A to 20C show pattern division examples in which the division direction is parallel, vertical, and oblique to the beam steering direction. Beam steering using a phase modulation element is premised on making a pattern perpendicular to the steering direction and deflecting light by a diffraction phenomenon. Therefore, the light beam on the phase modulation element is often long in the steering direction so as to be affected by more phase modulation elements. Thus, when the light beam is long in the steering direction, there are the following characteristics depending on the pattern dividing direction.

  When the pattern is divided in parallel to the steering direction, the direction of unnecessary diffracted light generated by the pattern division and the steering direction of the light beam are perpendicular, so the influence of unnecessary high-order light is minimized. However, in the region near the center irradiated with the light beam, there is a possibility that the influence on the phase change due to the pattern change becomes large. In this case, the number of divisions may be reduced in order to reduce the pattern change amount in one step.

  If the pattern is divided perpendicularly to the steering direction, the steering of the light beam may be affected, but the number of divisions should be increased because the light beam hits widely across the divided areas. Therefore, it is easy to control, and the influence of unintended high-order light can be reduced by adjusting the number of divisions.

  When the pattern is divided obliquely with respect to the steering direction, both the parallel and vertical characteristics are obtained, and which characteristic appears larger depending on the inclination angle.

  The third embodiment can be realized with a simple configuration because it is not necessary to calculate a new phase control value other than the pattern before and after switching by the phase pattern, and it is only necessary to change the display ratio of the previous and subsequent patterns. Further, since the diffraction by the phase pattern of each divided region and the diffraction by the repetition of two phase patterns can be completely separated, the influence of diffraction by the pattern switching can be controlled by controlling the pattern switching repetition period. . In other words, the pattern switching repetition period can be adjusted so as to diffract in the direction in which the output port is not arranged. Note that the time interval between steps in the third embodiment can be arbitrarily set, as can the time interval between patterns in the first embodiment.

10 Optical input / output device 11 Optical fiber (input port)
12, 15 ₁ to 15 _n collimating lens 13 optical element 14 phase modulation element 16 _{1 to} 16 _n optical fiber (output port)
17 Wavelength dispersion element 20 Optical input / output device 21 Optical fiber (input port)
22 collimating lens 23 first optical element 24 phase modulation element 25 second optical element 26 _{1 to} 26 _n collimating lens 27 _{1 to} 27 _n optical fiber (output port)
DRV drive circuit 28 ... wavelength dispersion element 29 ... wavelength dispersion element

Claims (6)

One or more input ports and one or more output ports for inputting and outputting optical signals;
Spatial phase modulation by providing a phase control value according to each pixel position for incident light input from the input port via an optical system element. A phase modulation element that emits the modulated outgoing light in the angular direction of the target output port specified among the output ports;
A drive circuit for controlling an emission angle and light intensity of the emitted light by the spatial phase modulation by applying a drive signal indicating a phase pattern composed of a phase control value for each pixel position to each pixel;
When the phase pattern is switched from the first phase pattern to the second phase pattern , the light intensity value at the target output port becomes equal to the light intensity value at the target output port in the first phase pattern and the second phase pattern . M (M is an integer of 1 or more) intermediate phase patterns that take values between the light intensity values at the target output port in the phase pattern of the target phase , and the intermediate phase pattern is other than the target output port When the crosstalk amount coupled to the output port is compared between the intermediate phase patterns, the difference between the light intensity values at the target output ports of the preceding and following phase patterns becomes small in a region where the crosstalk amount is relatively large. In the region where the amount of crosstalk is relatively small, the light intensity value at the target output port of the front and rear intermediate phase patterns Create the intermediate phase pattern so that the difference becomes greater, and controls the drive circuit to switch to the first of said from the phase pattern intermediate phase pattern via the second phase pattern, and a control circuit A spatial phase modulator characterized by that. One or more input ports and one or more output ports for inputting and outputting optical signals;
Spatial phase modulation by providing a phase control value according to each pixel position for incident light input from the input port via an optical system element. A phase modulation element that emits the modulated outgoing light in the angular direction of the target output port specified among the output ports;
A drive circuit for controlling an emission angle and light intensity of the emitted light by the spatial phase modulation by applying a drive signal indicating a phase pattern composed of a phase control value for each pixel position to each pixel;
A control circuit that creates M (M is an integer of 1 or more) intermediate phase patterns based on the first and second phase patterns when the phase pattern is switched from the first phase pattern to the second phase pattern; A control circuit that controls the drive circuit to switch from the first phase pattern to the second phase pattern via the intermediate phase pattern;
The control circuit creates the intermediate phase pattern in which the first region of the first phase pattern and the second region of the second phase pattern are alternately arranged. spatial phase modulator you. The spatial phase modulator according to claim 2 , wherein a boundary between the first region and the second region is perpendicular to an arrangement direction of incident / exit light of the input port and the output port. 3. The spatial phase modulator according to claim 2 , wherein a boundary between the first region and the second region is parallel to an arrangement direction of incoming and outgoing light of the input port and the output port. In the intermediate phase pattern, two or more first regions and two or more second regions are alternately arranged, and a repetition period between the first region and the second region is the incident light. The spatial phase modulator according to claim 2 , wherein the spatial phase modulator is set so as to emit light in a direction other than the angular direction of the output port. The intermediate phase pattern switching time interval is a time when the crosstalk amount is relatively large when comparing crosstalk amounts coupled to output ports other than the target output port at the time of switching the intermediate phase pattern. long, and the spatial phase modulator according to any one of claims 1 to 5 weight the crosstalk, characterized in that to shorten the time relatively small.