JP2015025887A - Optical input-output device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To change the intensity of output light in an optical input-output device while suppressing the generation of a crosstalk to another port.SOLUTION: A drive circuit DRV applies, to each pixel of a phase modulation element 14, a composite pattern in which an emitting angle control phase pattern 51 having a first pattern cycle length Λ is superposed on a light intensity control phase pattern 52 having a second pattern cycle length w. In this case, the first pattern cycle length Λ comprises a pattern cycle length for generating light intensity distribution in which an object light intensity peak 61 of emitted light is located in an angle direction matching the angle direction of an object output port, and the second pattern cycle length w comprises a pattern cycle length for generating light intensity distribution in which an unwanted light intensity peak 62 of emitted light is located in an angle direction not matching the angle direction of each output port.

Description

  The present invention relates to an optical fiber communication technique, and more particularly to an output light control technique for controlling a route and intensity of output light by a phase modulation element in an optical input / output device.

  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 turning back a phase and a means for realizing the method. By superimposing a periodic phase pattern on the light beam deflection element, it is possible to disperse the light intensity 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.

For example, when an LCOS-SLM that is a phase modulation element is used as an actual light beam deflection element, it is known that an electric field applied to control the phase of each pixel also affects the phase of adjacent pixels. Yes. This phenomenon is called disclination and causes a deviation between a phase pattern applied for deflection and attenuation operation and a desired pattern. Disclination increases as a short-period phase is applied to the phase modulation element, and crosstalk increases particularly when a periodic phase is superimposed for attenuation.
Therefore, there is a need for development of optical attenuation technology that can suppress an increase in crosstalk even when disclination occurs.

  That is, in the optical input / output device, when the signal light intensity is attenuated, it is desirable that the crosstalk outside the target output port is low so that optical signals having different periods do not interfere with each other. On the other hand, in spatial light modulation elements that are pixilated with a finite size, the applied phase pattern deviates from the ideal pattern due to the influence of adjacent interference during deflection and attenuation operations, causing crosstalk. Become. The crosstalk due to the deviation from the ideal pattern becomes more prominent as the phase change of the phase pattern applied to the LCOS-SLM, which is a phase modulation element, increases. In particular, a short-period phase pattern is applied to perform the attenuation operation. This is a problem.

  The present invention is to solve such problems, and provides an output light control technique capable of changing the output light intensity while suppressing the occurrence of crosstalk to other ports in an optical input / output device. The purpose is to do.

  In order to achieve such an object, an optical input / output device according to the present invention includes one or more input ports and a plurality of output ports for inputting / outputting optical signals, 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 each pixel a phase amount that changes according to the pixel position, and the obtained output light By applying a drive signal indicating a phase pattern indicating a relationship between a pixel position and a phase amount to each pixel, and a phase modulation element that emits in the angular direction of a specified target output port among the output ports. A drive circuit that controls the emission angle and the light intensity of the emitted light by spatial phase modulation, and the phase pattern is a second pattern cycle length to the output angle control phase pattern having the first pattern cycle length. The first pattern cycle length has a light intensity distribution positioned in an angular direction in which the target light intensity peak of the emitted light coincides with the angular direction of the target output port. The second pattern cycle length is a pattern cycle length that generates a light intensity distribution located in an angular direction in which the unnecessary light intensity peak of the emitted light does not coincide with the angular direction of each output port. It consists of

  Also, in one configuration example of the optical input / output device according to the present invention, the second pattern cycle length is outside the emission angle range in which the unnecessary light intensity peak includes all of the angular directions of the output ports. It consists of a pattern period length that generates a positioned light intensity distribution.

One example of the configuration of the optical input / output device according to the present invention is an angle corresponding to one end and the other end of the emission angle range among the angles θ formed by the incident light and the emitted light in the phase modulation element. When θ is θ _max and θ _min respectively, the wavelength of the incident light is λ, and the emission angle of the emitted light is θ _o , the pattern period length w of the phase pattern for light intensity control is an expression (described later) 4) and variable within the range where equation (5) holds.

  Also, in one configuration example of the optical input / output device according to the present invention, the second pattern cycle length is such that the unnecessary light intensity peak is between the angular directions of the output ports, and these outputs are output. It consists of a pattern period length that generates a light intensity distribution located in a gap angle range that does not interfere with the port.

One example of the configuration of the optical input / output device according to the present invention is an angle corresponding to one end and the other end of the gap angle range, among the angles θ formed by the incident light and the emitted light in the phase modulation element. When θ is θ _a and θ _b , the wavelength of the incident light is λ, and the emission angle of the emitted light is θ _o , the pattern period length w of the light intensity control phase pattern is expressed by the following formula ( 6), variable within the range where the equations (7) and (8) hold.

  In one configuration example of the optical input / output device according to the present invention, the phase of the emission angle control phase pattern is an integral multiple of the pixel size of the phase modulation element.

  In one configuration example of the optical input / output device according to the present invention, the emission angle control phase pattern has a pattern period length corresponding to an integral multiple of the pixel size of the phase modulation element. .

  Further, in one configuration example of the optical input / output device according to the present invention, the drive circuit records a period length of a second pattern for each of the output ports obtained by measuring in advance, and the target Means are provided for selecting an optimum value for each output port.

  According to the present invention, due to the pattern period length of the light intensity control phase pattern, the light intensity distribution is generated in the angular direction in which each unnecessary light intensity peak caused by the light intensity control phase pattern does not coincide with the angular direction of each output port. Thus, the output light intensity can be changed while suppressing the occurrence of crosstalk to other ports.

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 an example of the phase pattern setting to a phase modulation element. It is an example of diffraction in a reflection type phase modulation element. It is an example of the phase pattern setting to the phase modulation element concerning 1st Embodiment. It is a light intensity distribution figure which shows the object light intensity peak of emitted light. It is a light intensity distribution figure which shows the unnecessary light intensity peak of emitted light. It is a graph which shows the relationship between the phase amount given to an emitted light, and the emitted light intensity of an emitted light. It is explanatory drawing which shows the positional relationship of the assumption angle range concerning 1st Embodiment, and an unnecessary light intensity peak. It is explanatory drawing which shows the angle relationship between the assumption angle range concerning 1st Embodiment, and an unnecessary light intensity peak. It is a figure which shows the example of a phase pattern setting to the phase modulation element concerning 2nd Embodiment. It is explanatory drawing which shows the positional relationship of the assumption angle range concerning 3rd Embodiment, and an unnecessary light intensity peak. It is explanatory drawing which shows the angle relationship between the assumption angle range concerning 3rd Embodiment, and an unnecessary light intensity peak. It is explanatory drawing which shows the other angle relationship between the assumption angle range concerning 3rd Embodiment, and an unnecessary light intensity peak. It is a setting example of the phase pattern for light intensity control.

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 constituting 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 includes a reflection type phase modulation element having a plurality of pixels arranged in a matrix and is input from an optical fiber 11 serving as an input port via optical system elements such as a collimator lens 12 and an optical element 13. relative to the incident light, the spatial phase modulation by providing a phase amount varying at each pixel according to the pixel position, out of the optical fiber 16 ₁ ~ 16 _n is an output port of the outgoing light obtained, designated It has a function to emit in the angle direction of the optical fiber corresponding to the target output port.

  In addition, the drive circuit DRV applies a drive signal indicating a phase pattern of the pixel position and the phase amount to each pixel of the phase modulation element 14, thereby outputting an emission angle of emitted light by spatial phase modulation in the phase modulation element 14 and It has a function to control 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 given again 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. As for the optical signal, the output port of the optical element 13 and the output light intensity are selected by the phase pattern applied 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, the wavelength dispersion element 17 is arranged between the collimating lenses 12, 15 ₁ to 15 _n and the optical element 13, 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 disposed between the optical element 13 and the phase modulation element 14. 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 via the optical fiber 27 ₁ to the optical fiber 27 ₁ to the output port is subjected to spatial phase modulation by giving each pixel a phase amount that periodically changes according to the pixel position. 27 _n 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 the phase pattern of the pixel position and the phase amount to each pixel of the phase modulation element 24, so that the emission angle of the emitted light by the spatial phase modulation in the phase modulation element 24 and It has a function to control 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, for example, from the first to n-th channels (collimating lenses 26 ₁ to 26) by selecting the output port and light intensity of the second optical element 25 according to the phase pattern given to the phase modulation element 24. 26 _n and the optical fibers 27 _{1 to} 27 _n ) are output to arbitrary output ports in arbitrary paths.

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 between the phase modulation element 24 and the optical element 25. 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. The planar optical waveguide may be integrated with the functions of the collimating lenses 12, 15 ₁ to 15 _n , 22, 27 _{1 to} 27 _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 amount of the finally applied phase modulation element may not periodically change with respect to the pixel position.

[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 portion 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 amount to each pixel according to a 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 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, the incident area differs for each wavelength channel as shown in FIG. become that way. 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 R1 to Rn 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, it is possible to change the optical path length for each pixel and to control the phase by displacing the mirror corresponding to the position of each pixel in the z-axis direction.

[Output route selection method]
Next, with reference to FIGS. 7 and 8, an optical signal output path selection method in the phase modulation element will be described. FIG. 7 is an example of phase pattern setting for the phase modulation element. FIG. 8 shows an example of diffraction by the reflection type phase modulation element. Here, the reflection type phase modulation element 14 will be described as an example, but the same applies to the transmission type phase modulation element 24.

The output path is selected by, for example, controlling the diffraction angle of light incident on the phase modulation element 14 and selecting the emission direction of the emitted light. By making the output angle control phase pattern 51 into a saw shape as shown in FIG. 7, the diffraction angle of the emitted light can be controlled as shown in FIG. Here, φ is the phase of each pixel, and the traveling direction is positive. Further, the diffraction angle θ _o , that is, the angle formed by the outgoing light with respect to the normal direction of the phase modulation element 14 is given by the following equation (1). Where θ _in is the incident light angle, m is the diffraction order, λ is the wavelength of the incident light, and Λ is a pattern period length (first time) indicating the length of one period of the output angle control phase pattern 51. Pattern cycle length).

FIG. 8 shows a case where light enters from the normal direction of the phase modulation element 14, that is, θ _in = 0.
Thus, it is possible to optically couple to an arbitrary output port by changing Λ so as to obtain an optimum optical coupling for a desired output port and adjusting the diffraction angle θ _o .

[Light intensity control method]
Next, a light intensity control method used in the optical input / output devices 10 and 20 according to the present invention will be described. The light intensity control method according to the present invention is roughly divided into four methods. These light intensity control methods are all realized by the optical input / output devices 10 and 20 having the above-described basic configurations. Here, the optical input / output device 10 using the reflection type phase modulation element 14 will be described as an example, but the same applies to the optical input / output device 20 using the transmission type phase modulation element 24.

[First Embodiment]
First, the light intensity control method of the optical input / output device 10 according to the first embodiment of the present invention will be described with reference to FIGS. FIG. 9 is an example of phase pattern setting for the phase modulation element according to the first embodiment. FIG. 10 is a light intensity distribution diagram showing the target light intensity peak of the emitted light. FIG. 11 is a light intensity distribution diagram showing an unnecessary light intensity peak of emitted light.

  The optical input / output device 10 according to the present embodiment has a light intensity as a phase pattern of the drive signal applied from the drive circuit DRV to the phase modulation element 14 with respect to the emission angle control phase pattern 51 shown in FIG. By using a composite pattern in which the control phase pattern 52 is superimposed, output route selection and output light intensity control are performed.

The output angle control phase pattern 51 that can be coupled to an arbitrary output port is, for example, a sawtooth-shaped phase pattern as shown in FIG. 7, and the amplitude of the sawtooth wave is preferably 2π. . When only this output angle control phase pattern 51 is used, a light intensity distribution having only the target light intensity peak 61 at the output angle θ _o indicating the angular direction of the target output port is generated as shown in FIG.

When the light intensity control phase pattern 52 is superimposed on the emission angle control phase pattern 51 such that the phase φ in one cycle is expressed by the following equation (2), as shown in FIG. As described above, unnecessary unnecessary light intensity peaks 62 due to light diffraction appear at a plurality of emission angles, here emission angles θ _s-2 , θ _s-1 , θ _{s + 1} , and θ _{s + 2} . Here, w is a pattern cycle length (second pattern cycle length) indicating the length of one cycle of the light intensity control phase pattern 52, and k is a constant representing the amplitude of the light intensity control phase pattern 52. . Mod (y, w) represents the remainder of y at w.

Therefore, by controlling the amplitude of the light intensity control phase pattern 52 by changing k, the light intensity of the target light intensity peak 61 at the emission angle θ _o indicating the angular direction of the target output port is changed to each unnecessary light intensity peak. Therefore, the light intensity of the target light intensity peak 61 can be attenuated. Thereby, it is possible to attenuate the light emitted to the target output port.

The emission angle θ _s indicating the angular direction of each unnecessary light intensity peak 62 generated by the light intensity control phase pattern 52 can be expressed by the following equation (3). Here, m ′ is the order of diffraction and is an integer. For example, θ _s when m ′ = ₁ is defined as θ _{s + 1} . Further, the emission angle interval Δθ _s of each unnecessary light intensity peak 62 is defined as Δθ _s = θ _s −θ _o .

  FIG. 12 is a graph showing the relationship between the phase amount given to the outgoing light and the outgoing light intensity of the outgoing light. An LCOS-SLM is used for the phase modulation element 14, and the fan is assumed to have a fan-shaped angular range of θ = −0.8 ° to 0.8 ° with the normal of the phase modulation element 14 as the center (θ = 0). And the pattern period length w of the light intensity control phase pattern 52 is set to 4 pixels. From FIG. 12, it is understood that the intensity of the emitted light can be arbitrarily controlled by changing the phase amount given to the emitted light by the phase pattern 52 for controlling the light intensity.

  Here, when each unnecessary light intensity peak 62 generated by the light intensity control phase pattern 52 is generated in an angular direction that coincides with the angular direction of the output port, this causes an increase in crosstalk. In the present embodiment, the pattern period length w of the light intensity control phase pattern 52 is selected so that each unnecessary light intensity peak 62 generates a light intensity distribution in an angular direction that does not coincide with the angular direction of each output port. It is what I did. w may be a decimal number. When a phase modulation element composed of pixels of a finite size such as LCOS is used, the actual phase pattern is quantized by the pixel of the phase modulation element and takes a spatially discrete value.

As a result, the pattern period length w of the light intensity control phase pattern 52 can be changed according to the angle direction of the designated target output port among the output ports, that is, the emission angle θ _o of the emitted light. It is possible to change the output light intensity while suppressing the occurrence of crosstalk to the port.

  In the present embodiment, the unnecessary light intensity peak 62 may be combined with each output port as a specific method for preventing the angular direction of each unnecessary light intensity peak 62 from matching the angular direction of each output port. The pattern period length w of the light intensity control phase pattern 52 is set so that a light intensity distribution located outside the assumed angular range, that is, the fan-shaped assumed angular range including all the angular directions of each output port is generated. It is what you choose.

  FIG. 13 is an explanatory diagram illustrating a positional relationship between the assumed angle range and the unnecessary light intensity peak according to the first embodiment. FIG. 14 is an explanatory diagram illustrating an angular relationship between an assumed angle range and an unnecessary light intensity peak according to the first embodiment.

  In the example of FIG. 13, an input port P0 and n output ports P1 to Pn are provided, and incident light input from the input port P0 via the optical element 13 is transmitted in an arbitrary angular direction by the phase modulation element 14. And output to one of the corresponding output ports P1 to Pn via the optical element 13. As shown in FIG. 13, when the optical element 13 exists between the phase modulation element 14 and the output port, the angular direction of the output port viewed from the phase modulation element 14 indicates the output in the optical element 13. The angle direction to the optical input area corresponding to the port is indicated.

Therefore, as shown in FIG. 14, among the angles θ formed by the incident light and the outgoing light, the port interference sections RI1 to RIn exist at the outgoing angles corresponding to the angular directions of the output ports P1 to Pn.
Here, as shown in FIGS. 13 and 14, the angle θ formed by the incident light and the outgoing light in the phase modulation element 14 is coupled to the outermost output port arranged at the outermost side among the output ports. When the outgoing angles are θ _max and θ _min , the outgoing angle θ _s1 (θ _{s + 1} , θ at the diffraction order m ′ = 1 is larger than the absolute values | θ _max | and | θ _min | of these θ _max and θ _{min. When} the absolute value | θ _s1 | of _s-1 ) is small, the unnecessary light intensity peak 62 assumes an assumed angle range RP in which the input / output ports are arranged, that is, θ _max to θ _min corresponding to one end and the other end of the assumed angle range RP. It exists inside the angle range up to. For this reason, when light is coupled to an output port other than the target output port, crosstalk occurs.

Therefore, in order to prevent such crosstalk, the unnecessary light intensity peak 62 adjacent to the target light intensity peak 61 is positioned in the outer region RE outside the assumed angle range RP, that is, | θ _s | is θ _max. , Θ _{min and} the pattern cycle length w (second pattern cycle length) of the light intensity control phase pattern 52 may be selected.
That is, w may be variable between w and θ _o within a range in which the relationship of the following expressions (4) and (5) is satisfied.

  If, for example, w is set to the maximum within a range satisfying these equations (4) and (5), a steep phase change in the phase modulation element 14 can be suppressed, and crosstalk due to disclination can be suppressed. Can be suppressed.

  At this time, the same effect can be obtained even if the light intensity control phase pattern 52 is not a sawtooth wave. For example, it may be a sine wave, a triangular wave, or a pulse wave. Similarly, the phase pattern that can be coupled to the output port can be the same effect even if it is not a sawtooth wave. For example, it may be a sine wave, a triangular wave, or a pulse wave. Further, the phase folding (amplitude) may not be 2π.

FIG. 19 is an example of setting a light intensity control phase pattern. When the period of the superposed light intensity control phase pattern is not an integral multiple of the pixel size of the phase modulation element, this is equivalent to the case where a plurality of frequency components are effectively superimposed as shown in FIG. In this case, since unnecessary light is slightly emitted in addition to the desired emission angle θ _s , it causes an increase in crosstalk.

  In order to suppress this, w may be set to an integral multiple of the pixel size of the phase modulation element while satisfying the relations of Expressions (4) and (5). According to the present embodiment, unnecessary light can be concentrated at a desired angle, and an excellent effect of reducing crosstalk can be obtained.

[Second Embodiment]
Next, with reference to FIG. 15, the light intensity control method of the optical input / output device 10 according to the second exemplary embodiment of the present invention will be described. FIG. 15 is a diagram illustrating an example of setting a phase pattern in the phase modulation element according to the second embodiment. Here, the optical input / output device 10 using the reflection type phase modulation element 14 will be described as an example, but the same applies to the optical input / output device 20 using the transmission type phase modulation element 24.

  In the first embodiment, by making the pattern period length w of the light intensity control phase pattern 52 variable, it is possible to control the light intensity while suppressing crosstalk due to disclination. However, when the pattern period length Λ of the output angle control phase pattern 51 is not an integral multiple of w, the number of aliasing sites where phase discontinuity increases increases, and crosstalk due to disclination increases.

  In order to suppress this, it is only necessary to select a pattern cycle length period in which Λ corresponds to an integer multiple of w as shown in FIG. 15 while satisfying the relationship of Expressions (4) and (5). According to this embodiment, it is possible to obtain an excellent effect that the folded portion is reduced and crosstalk due to disclination is reduced.

[Third Embodiment]
Next, an optical input / output device 10 according to a third embodiment of the present invention will be described with reference to FIGS. FIG. 16 is an explanatory diagram illustrating a positional relationship between an assumed angle range and an unnecessary light intensity peak according to the third embodiment. FIG. 17 is an explanatory diagram illustrating an angular relationship between an assumed angle range and an unnecessary light intensity peak according to the third embodiment.
Here, the optical input / output device 10 using the reflection type phase modulation element 14 will be described as an example, but the same applies to the optical input / output device 20 using the transmission type phase modulation element 24.

In the example of FIG. 16, an input port P0 and n output ports P1 to Pn are provided, and incident light input from the input port P0 via the optical element 13 is transmitted in an arbitrary angular direction by the phase modulation element 14. And output to one of the corresponding output ports P1 to Pn via the optical element 13.
Therefore, as shown in FIG. 17, among the angles θ formed by the incident light and the outgoing light, the port interference sections RI1 to RIn exist at the outgoing angles corresponding to the angular directions of the output ports P1 to Pn.

In the first embodiment, the light intensity control phase pattern 52 is set so that the unnecessary light intensity peak 62 is located in the outer region RE outside the fan-shaped assumed angle range RP including all the angular directions of the output ports. The case where the pattern cycle length w is selected has been described as an example. At this time, as can be seen from the equations (4) and (5), the selectable w value decreases as the values of | θ _min | and | θ _max | Crosstalk also increases.

  In the present embodiment, the light intensity control phase pattern 52 is such that the unnecessary light intensity peak 62 is located in the gap angle range RQ that is the gap in the angular direction of each output port and does not interfere with these output ports. The pattern cycle length w is selected.

That is, among the angles θ formed by the incident light and the outgoing light in the phase modulation element 14, angles θ corresponding to one end and the other end of an arbitrary gap angle range RQ are θ _a and θ _b , respectively, and the wavelength of the incident light Where λ is λ and the emission angle of the emitted light is θ _o , the pattern period length w of the light intensity control phase pattern 52 satisfies the following equations (6), (7), and (8). Variable in range.

  At this time, it is difficult to select the pattern cycle length w so that all of the unnecessary light intensity peaks 62 are located within the gap angle range RQ due to the number of output ports and the size of the free space in the optical input / output device 10. Cases are also conceivable. In such a case, w may be selected within a range in which the above-described formulas (4) and (5) are satisfied, whereby a part of the unnecessary light intensity peak 62 is outside the assumed angle range RP. As a result, all of the unnecessary light intensity peaks 62 can be generated in an angular direction that does not interfere with the output port.

  When w is selected in a range that satisfies the expressions (4) and (5), the unnecessary light intensity peak 62 of the high-order emitted light of m ′ ≧ 2 in the expression (3) unconditionally appears in the outer region RE. Will exist. However, when exiting light with m ′ = 1 is present in the gap of the port as in equation (6), the unnecessary light intensity peak 62 of the higher-order outgoing light with m ′ ≧ 2 needs to be emitted to the outside of the port. Therefore, the conditions of Expression (7) and Expression (8) are necessary.

In the above description, the case where there is one gap angle range RQ where there is no output port has been described as an example. However, the same effect can be obtained even when a plurality of gap angle ranges RQ where no port exists. In this case, the boundary condition may be appropriately changed according to the above-described concept.
FIG. 18 is an explanatory diagram showing another angular relationship between the assumed angle range and the unnecessary light intensity peak according to the third embodiment. Here, a case where there is a gap angle range RQs where no port exists between the angle sections RIa and RIb and a gap angle range RQp where no port exists between the angle sections RIb and RIc is shown as an example.

  In the example of FIG. 18, first, when the target output port exists in the angle section RIa, the light intensity control phase is set so that the unnecessary light intensity peak 62 of the high-order emitted light of m ′ = 1 appears in the gap angle range RQp. When the pattern period length w of the pattern 52 is selected and the target output port exists in the angle section RIc, w is set so that the unnecessary light intensity peak 62 of the high-order outgoing light with m ′ = 1 appears in the gap angle range RQs. Just choose.

  When the target output port is present in the angular interval RIb, w may be selected so that the unnecessary light intensity peak 62 of the high-order outgoing light with m ′ = 1 is located in the outer region RE. As a result, high-order light is not generated in the port setting section, and the length of one cycle of the phase to be superimposed can be made larger than in the case of the first and second embodiments, so that an excellent effect that crosstalk can be suppressed. Is obtained.

[Fourth Embodiment]
Next, a light intensity control method for the optical input / output devices 10 and 20 according to the fourth embodiment of the present invention will be described.
In the first to third embodiments 1 to 3, there is a possibility that the phase period that most suppresses the crosstalk to the target output port is not necessarily selected. In the present embodiment, the cycle dependency of the light intensity control phase pattern 52 on the pattern cycle length w regarding the crosstalk value to each output port is measured in advance for each output port, and the specified target In accordance with the output port, w is selected so that the crosstalk amount of the other output port becomes the minimum value.

  With respect to the cycle dependency regarding an arbitrary output port, the crosstalk amount at each output port other than the output port may be measured while changing the pattern cycle length w. Among the obtained cycle dependencies, w that minimizes the amount of crosstalk at each output port is specified as the optimum pattern cycle length ws of the output port, and is registered in a storage unit (not shown) of the drive circuit DRV. Just keep it.

  Thereby, according to the designation of the target output port from the outside, the drive circuit DRV reads the optimum value ws of the pattern cycle length w of the target output port from the storage unit, and the light intensity control phase pattern 52 having this ws is read. The drive signal indicating the composite pattern thus obtained may be applied to each pixel of the phase modulation element 14 while being superimposed on the output angle control phase pattern 51 indicating the angle direction to the target output port.

[Extended embodiment]
The present invention has been described above with reference to the embodiments, but the present invention is not limited to the above embodiments. Various changes that can be understood by those skilled in the art can be made to the configuration and details of the present invention within the scope of the present invention. In addition, each embodiment can be implemented in any combination within a consistent range.

DESCRIPTION OF SYMBOLS 10 ... Optical input / output device, 11 ... Optical fiber (input port), 12, 15 _{< 1 >} -15n ... Collimating lens, 13 ... Optical element, 14 ... Phase modulation element, 16 _{< 1 >} -16n ... 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, 51 ... phase pattern for emission angle control, 52 ... Light intensity control phase pattern, 61 ... target light intensity peak, 62 ... unnecessary light intensity peak, Λ ... pattern cycle length (first pattern cycle length), w ... pattern cycle length (second pattern cycle length), RP … Assumed angle Enclosed, RE ... outer region, RQ ... gap angle range.

Claims (8)

One or more input ports and a plurality of output ports for inputting and outputting optical signals;
By providing each pixel with a plurality of pixels arranged in a matrix and providing phase amounts that change according to the pixel position with respect to incident light input from the input port via an optical system element. A phase modulation element that spatially modulates and emits the obtained outgoing light in an angle direction of a specified target output port among the output ports;
A drive circuit that controls the emission angle and light intensity of the emitted light by the spatial phase modulation by applying a drive signal indicating a phase pattern indicating a relationship between a pixel position and a phase amount to each pixel;
The phase pattern includes a light intensity control phase pattern having a second pattern period length superimposed on an output angle control phase pattern having a first pattern period length,
The first pattern cycle length is a pattern cycle length that generates a light intensity distribution in which the target light intensity peak of the emitted light is located in an angular direction that coincides with the angular direction of the target output port. The period length is a pattern period length that generates a light intensity distribution in which an unnecessary light intensity peak of the emitted light is located in an angular direction that does not coincide with the angular direction of each output port. The optical input / output device according to claim 1,
The second pattern cycle length is a pattern cycle length that generates a light intensity distribution in which the unnecessary light intensity peak is located outside an emission angle range including all of the angular directions of the output ports. Optical input / output device. The optical input / output device according to claim 2,
Of the angle θ formed by the incident light and the outgoing light in the phase modulation element, angles θ corresponding to one end and the other end of the outgoing angle range are θ _max and θ _min , respectively, and the wavelength of the incident light is λ and then, when the emission angle of the emitted light was theta _o, pattern cycle length w of the light intensity control phase pattern, the following formula (a)

An optical input / output device that is variable within a range in which The optical input / output device according to any one of claims 1 to 3,
The second pattern period length is a pattern that generates a light intensity distribution in which the unnecessary light intensity peak is located between the angular directions of the output ports and in a gap angle range that does not interfere with the output ports. An optical input / output device comprising a periodic length. The optical input / output device according to claim 4,
Of the angle θ formed by the incident light and the emitted light in the phase modulation element, angles θ corresponding to one end and the other end of the gap angle range are θ _a and θ _b , respectively, and the wavelength of the incident light is λ and then, when the emission angle of the emitted light was theta _o, pattern cycle length w of the light intensity control phase pattern, the following formula (B)

An optical input / output device that is variable within a range in which In the optical input / output device according to any one of claims 1 to 5,
An optical input / output device characterized in that the phase of the phase pattern for emission angle control is an integral multiple of the pixel size of the phase modulation element. In the optical input / output device according to any one of claims 1 to 5,
The output angle control phase pattern has a pattern period length corresponding to an integer multiple of a pixel size of the phase modulation element. In the optical input / output device according to any one of claims 1 to 7,
The drive circuit records a period length of a second pattern for each of the output ports obtained by measuring in advance, and has means for selecting an optimum value for each of the target output ports. Optical input / output device.

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