JP2006071664A - Optical switching method and optical switching system - Google Patents

Abstract

PROBLEM TO BE SOLVED: To freely control the output end of signal light and to prevent the spatial spread of light due to a diffraction effect.
An input port 3 and a plurality of output ports 4 are defined in a nonlinear optical medium 2 having physical properties exhibiting a spatial light soliton effect, and control light L2 is incident on the output port 4 selected from the plurality of output ports 4. Then, a region having an increased refractive index is formed in the nonlinear optical medium 2, and the signal light L1 incident on the input port 3 is drawn to the selected refractive index increasing region and guided to the selected output port 4, whereby the signal light L1. Switch the output destination.
[Selection] Figure 1

Description

  The present invention relates to an optical switching method and an optical switching system. More specifically, the present invention relates to an optical switching method and an optical switching system using the spatial optical soliton effect.

  An optical switch generally changes various properties of signal light incident on a switching element, such as intensity and propagation direction, by a control signal input to the switching element separately from the signal light. Used in.

  Since light tends to bend into a region having a high refractive index, a simple optical switch shown in FIG. 8 can be configured using this property (see Non-Patent Document 1). FIG. 8A shows a case where the signal light 101 is incident on the optical crystal 100 used as a switching element. Here, as shown in FIG. 8B, it is considered that the control light 102 is incident on the incident surface of the signal light 101 in the optical crystal 100 from a direction different from the signal light 101. If the intensity and wavelength of the control light 102 are selected and the refractive index in the optical crystal 100 can be changed, the propagation direction of the signal light 101 is also affected by the change in the refractive index, so that optical switching can be performed. Yes. Here, even if the laser light has a strong directivity, it has a property of spreading spatially due to the diffraction effect (particularly, the light tends to spread as the beam diameter becomes smaller), so that the property can also be seen in FIG. It is shown as follows.

  On the other hand, an optical crystal for a switching element is also manufactured so as to have a structure having a high refractive index only in a specific region. In other words, a path of signal light called a waveguide is produced in an optical crystal for a switching element. FIG. 9 shows an example of an optical switch using a waveguide (see Non-Patent Document 2). The waveguide 103 is formed in the optical crystal 106 so as to branch from one input port 104 to two output ports 105A and 105B, and the signal light 101 passing through the waveguide 103 travels at a branch point of the waveguide 103. Electrodes 107A and 107B for controlling the direction are provided. When the voltages applied to the electrode 107A and the electrode 107B are equal, the signal light 101 input from the input port 104 is branched in two directions with equal intensity at a branch point in the middle of the waveguide 103, and the like from the output port 105A and the output port 105B. Output in intensity. Here, when different voltages are applied to the electrodes 107A and 107B, the refractive index in the optical crystal 106 differs between the electrodes 107A and 107B, and the signal light 101 output from the output port 105A and the output port 105B is It is not equal strength. In this way, the output destination of the signal light 101 can be switched by controlling the voltage applied to the electrodes 107A and 107B. As a means for controlling the traveling direction of the signal light 101 passing through the waveguide 103, in addition to the above-described means using the electrodes 107A and 107B, a temperature gradient is given to the optical crystal 106, and the vicinity of the branching portion of the waveguide 103 is provided. Some have different refractive indices.

D. Kip, et al., “All-optical beam deflection and switching in strontium-barium-niobate waveguides,” Appl. Phys. Lett., Vol. 72, pp. 1960? 1962 (1998). Kenichi Yukimatsu, “Optical switching and optical interconnection,” Kyoritsu Shuppan (1998).

  However, the conventional optical switch shown in FIG. 8 has an advantage that the propagation path of the signal light 101 in the optical crystal 100 can be freely controlled by changing the direction of the control light 102, but the light is spatially affected by the diffraction effect. Have the problem of spreading. For this reason, the optical switch shown in FIG. 8 requires a condensing lens for reducing the beam diameter, and it is difficult to miniaturize and integrate the optical switching device.

  On the other hand, the conventional optical switch shown in FIG. 9 confines and propagates light in the waveguide 103, and thus has the advantage of preventing the spatial spread of light due to the diffraction effect. In addition, since the signal light emitting ends (output ports 105A and 105B) are fixed, the propagation path of the signal light 101 cannot be freely controlled, and the request for changing the output port cannot be flexibly handled. In addition, the size of the cross section of the waveguide 103 is extremely small, from several μm to several tens of μm, for reasons such as miniaturization of the switching element and reduction of the loss of light to be transmitted. This is required and contributes to the cost of the optical switch. In addition, an optical switch incorporating the electrodes 107A and 107B may cause a malfunction due to an unintended voltage difference between the electrodes 107A and 107B in a place where a strong electric field or magnetic field acts. Also, in an optical switch that performs switching by applying a temperature gradient to the optical crystal 106, it takes time from when the temperature change is applied to the optical crystal 106 to when the output destination of the signal light is actually switched after the heater or the like is turned on, for example. Has a problem that the response is poor.

  Accordingly, the present invention provides an optical switching method and an optical switching system that enable free control of the output end of signal light, and that can improve the degree of integration by preventing spatial spread of light due to diffraction effects. Objective.

  In order to achieve such an object, an optical switching method according to claim 1, wherein an input port and a plurality of output ports are defined in a nonlinear optical medium having physical properties exhibiting a spatial light soliton effect, and selected from the plurality of output ports. A control light is incident on the output port to form a region in which the refractive index is increased in the nonlinear optical medium, and the signal light incident on the input port is drawn to the refractive index increased region to the selected output port. By guiding, the output destination of the signal light is switched.

  The optical switching system according to claim 4 is a non-linear optical medium having physical properties exhibiting a spatial optical soliton effect, an input port and a plurality of output ports set in the non-linear optical medium, and signal light to the input port. An incident communication light source, a plurality of light receiving means for receiving the signal light emitted from the output port, a control light source for entering control light into the output port, and from the control light source to the output port An optical path setting unit that transmits the control light and transmits the signal light from the output port to the light receiving unit, and the control light is incident on an output port selected from the plurality of output ports. A region having an increased refractive index is formed in the nonlinear optical medium, and the signal light incident on the input port is attracted to the refractive index increased region and the selected output By inducing the over bets, and to switch the output destination of the signal light.

  Therefore, when the control light is incident on the output port of the nonlinear optical medium, the control light itself causes a refractive index change in the nonlinear optical medium, and a spatial light soliton effect in which the control light propagates without spreading in the medium appears. The signal light is attracted to a refractive index increasing region (that is, a waveguide) created by the control light, and is guided to the incident end of the control light while its spatial expansion is suppressed by the waveguide. That is, by making the control light enter the nonlinear optical medium exhibiting the spatial light soliton effect, the output destination of the signal light incident on the nonlinear optical medium can be switched.

  According to a second aspect of the present invention, in the optical switching method according to the first aspect, the signal light or the control light is transmitted by an optical fiber outside the nonlinear optical medium. According to a fifth aspect of the present invention, in the optical switching system according to the fourth aspect, the signal light or the control light is transmitted by an optical fiber outside the nonlinear optical medium.

  In this case, in the nonlinear optical medium, the spatial spread of the signal light and the control light can be reduced by the spatial light soliton effect. In addition, the signal light and the control light are transmitted to the optical fiber outside the nonlinear optical medium. Since the light is confined and transmitted, the spatial spread of these lights can be greatly reduced, and the spread can be minimized.

  According to a third aspect of the present invention, in the optical switching method according to the first or second aspect, the sensitivity of the refractive index change of the nonlinear optical medium is greater for the control light than for the signal light. It is supposed to be. According to a sixth aspect of the present invention, in the optical switching system according to the fourth or fifth aspect, the sensitivity of the refractive index change of the nonlinear optical medium is greater for the control light than for the signal light. It is supposed to be. In this case, the signal light can be reliably and accurately controlled effectively by the control light.

  Therefore, according to the optical switching method according to claim 1 and the optical switching system according to claim 4, the signal light is guided to the incident end of the control light while reducing the spatial spread of the signal light by the spatial light soliton effect. In addition, since the propagation destination can be switched, a condensing lens or the like for reducing the beam diameter is unnecessary, and the optical switch can be downsized and the optical switching device can be integrated. In addition, there is no need for a special and precise process in which an electrode is provided in a nonlinear optical medium that is a switching element or a fixed waveguide is manufactured, so that the cost of the optical switch can be reduced. Furthermore, since the waveguide according to the present invention is not a fixed one but a variable one generated by control light, the signal light propagation path can be freely controlled, and the output port and input port can be controlled. Can easily handle setting changes. In addition, when the control light source and the light receiving means are configured as a single-unit receiving device, the receiving device that desires to receive the signal light can output the control light by itself to receive the signal light. A new optical switching system can be realized. In addition, since the optical switch of the present invention performs switching by control light, unlike the type in which an electrode is built in the optical element, there is no problem of causing malfunction even in a place where a strong electric or magnetic field acts, and a temperature gradient is given. Responsiveness can be improved compared to an optical switch that performs switching.

  Furthermore, according to the optical switching method according to claim 2 and the optical switching system according to claim 5, since the signal light or the control light is transmitted by the optical fiber outside the nonlinear optical medium, the spatial expansion of these lights. Can be greatly reduced, and the spread can be minimized.

  Further, according to the optical switching method according to claim 3 and the optical switching system according to claim 6, it is assumed that the sensitivity of the refractive index change of the nonlinear optical medium is greater for the control light than for the signal light. Therefore, the signal light can be reliably and accurately controlled effectively by the control light.

  Hereinafter, the configuration of the present invention will be described in detail based on embodiments shown in the drawings.

  1 to 4 show an embodiment of an optical switching method and an optical switching system 1 according to the present invention. This optical switching method uses a spatial light soliton effect, and an input port 3 and a plurality of output ports 4 are defined in a nonlinear optical medium 2 having physical properties exhibiting a spatial light soliton effect. The control light L2 is incident on the output port 4 selected from the above to form a region with an increased refractive index in the nonlinear optical medium 2, and the signal light L1 incident on the input port 3 is attracted to the refractive index increased region for selection. By guiding to the output port 4, the output destination of the signal light L1 is switched.

  The spatial light soliton effect is a phenomenon in which light is confined and propagated in a refractive index increasing region (that is, a waveguide) formed by a refractive index change caused by light in the nonlinear optical medium 2. The nonlinear optical medium 2 refers to an optical medium having a strongly nonlinear dielectric response function with respect to light radiation.

  Light has the property of spreading spatially due to the diffraction effect even if it is a highly directional laser beam. For this reason, as shown in FIG. 6, the light L that normally travels in the optical medium 100 propagates while spreading in the optical medium 100. In contrast, when the spatial light soliton effect occurs in the nonlinear optical medium 2 by the light L incident on the nonlinear optical medium 2, the light L itself is formed in the nonlinear optical medium 2 as shown in FIG. Since the propagation is confined in the waveguide, the influence of the diffraction effect is reduced, and the propagation does not spread spatially in the nonlinear optical medium 2.

  The inventor of the present application pays attention to the fact that a refractive index increasing region (that is, a waveguide) is formed in the nonlinear optical medium 2 when the first light is incident on the nonlinear optical medium 2 exhibiting the spatial light soliton effect. When the second light is incident on the nonlinear optical medium 2 in the state where the refractive index increasing region is formed, the second light is attracted to the waveguide and confined in the waveguide and propagates. It was confirmed by experiment that the above-mentioned matter actually occurred. Then, the inventor of the present application makes the first optical light the control light L2, the second light is the signal light L1, and the control light L2 is incident on the nonlinear optical medium 2 exhibiting the spatial light soliton effect. The idea has been reached that the output destination of the signal light L1 incident on the medium 2 can be switched, that is, optical switching can be realized.

  Here, it is preferable that the sensitivity of the refractive index change of the nonlinear optical medium 2 is larger for the control light L2 than for the signal light L1. More desirably, the spatial light soliton effect does not occur even when the signal light L1 enters the nonlinear optical medium 2, that is, the refractive index does not increase in the nonlinear optical medium 2 even when the signal light L1 enters, but the control light When L2 is incident on the nonlinear optical medium 2, a spatial light soliton effect is generated, that is, when the control light L2 is incident, an increase in refractive index is generated in the nonlinear optical medium 2. Thereby, the signal light L1 can be reliably and accurately controlled by the control light L2.

  The degree of the spatial light soliton effect generated in the nonlinear optical medium 2, in other words, the sensitivity of the refractive index change of the nonlinear optical medium 2 depends on the composition of the nonlinear optical medium 2 and the intensity and wavelength of incident light. Therefore, by selecting the composition of the nonlinear optical medium 2, selecting the light intensity and wavelength of the control light L2, and selecting the intensity and wavelength of the signal light L1, the sensitivity of the refractive index change of the nonlinear optical medium 2 with respect to the control light L2 can be expressed as a signal. The sensitivity of the refractive index change of the nonlinear optical medium 2 with respect to the light L1 can be increased. For example, the light intensity of the signal light L1 is made weaker than the light intensity (threshold value) necessary to generate the spatial light soliton effect, and the light intensity of the control light L2 is set to be equal to or higher than the above threshold value. Alternatively, the signal light L1 has a wavelength outside the optical wavelength range and the control light L2 has a wavelength within the optical wavelength range with respect to the optical wavelength range in which the spatial light soliton effect is generated. The light intensity necessary to generate the spatial light soliton effect and the light wavelength range that generates the spatial light soliton effect may vary depending on the composition of the nonlinear optical medium 2.

Examples of the nonlinear optical medium 2 that exhibits the spatial light soliton effect include glass materials and photorefractive crystals. In particular, the photorefractive crystal has high sensitivity to the spatial light soliton effect and is suitable as the optical switching element of the present invention. Specific examples of suitable photorefractive crystals include SBN (Strontium Barium Niobate) crystals, BSO (Bi ₁₂ SiO ₂₀ ) crystals, Fe: InP crystals, and the like. The SBN crystal has high sensitivity of the nonlinear optical effect in visible light, and visible light can be used as the control light L2. The BSO crystal is slightly inferior in sensitivity to the SBN crystal, but has the advantage of a high reaction rate. The Fe: InP crystal is a semiconductor, has high sensitivity in the near infrared region, and can use near infrared light as the control light L2.

  The optical switching method of the present invention is implemented as an optical switching system 1 shown in FIG. 1, for example. The optical switching system 1 includes a nonlinear optical medium 2 having physical properties that exhibit a spatial light soliton effect, an input port 3 and a plurality of output ports 4 set in the nonlinear optical medium 2, and signal light L1 incident on the input port 3. Communication light source 5, a plurality of light receiving means 6 for receiving the signal light L 1 emitted from the output port 4, a control light source 7 for entering the control light L 2 into the output port 4, and an output port from the control light source 7. 4 and an optical path setting means 8 for transmitting the signal light L1 from the output port 4 to the light receiving means 6.

  The nonlinear optical medium 2 of this embodiment has, for example, one input port 3 and two output ports 4. The nonlinear optical medium 2 has a cubic or rectangular parallelepiped shape, for example, and the surface on which the input port 3 is set and the surface on which the output port 4 is set are two opposing surfaces in the nonlinear optical medium 2. That is, the output port 4 is set on the surface opposite to the surface on which the input port 3 is set. By making the control light L2 incident on the nonlinear optical medium 2 from the opposite side of the signal light L1, the signal light L1 can be easily guided to the waveguide formed by the control light L2. However, the shape of the nonlinear optical medium 2 and the positional relationship between the input port 3 and the output port 4 are not necessarily limited to the example of the present embodiment, as long as the signal light L1 can be guided to the waveguide formed by the control light L2. good.

  In the optical switching system 1 of the present embodiment, as the control light source 7, the first control light source 7A that enters the first control light L2a to the first output port 4A, and the second control light L2b to the second output port 4B. And the incident second control light source 7B. In the present embodiment, the control light source 7 is provided for each output port 4. However, the present invention is not necessarily limited to this configuration example, and the control light source 7 can be moved mechanically. The configuration may be such that the control light L2 can be selectively incident on any of the plurality of output ports 4 by the light source 7 for use. Further, the control light source 7 and the communication light source 5 of the present embodiment are laser light sources. Since the laser light has strong directivity, the spatial spread of the signal light L1 and the control light L2 can be suppressed by using the signal light L1 and the control light L2 as laser light.

  In the optical switching system 1 of the present embodiment, as the light receiving means 6, the first light receiver 6A that receives the signal light L1 emitted from the first output port 4A and the signal light L1 emitted from the second output port 4B are used. And a second light receiver 6B for receiving light. Further, the optical switching system 1 of the present embodiment is disposed as the optical path setting means 8 between the first output port 4A and the first control light source 7A, and is transferred from the first control light source 7A to the first output port 4A. The first mirror 9A that transmits the control light L2 emitted toward the first output port and reflects the signal light L1 emitted from the first output port 4A toward the first light receiver 6A, and the second output port 4B and the second control. The control light L2 emitted from the second control light source 7B toward the second output port 4B and transmitted from the second output port 4B to the second signal light L1. And a second mirror 9B that reflects toward the light receiver 6B. The first and second mirrors 9A and 9B are wavelength selective mirrors (also called dielectric multilayer mirrors) that reflect light of a specific wavelength and transmit light of other wavelengths. For this reason, in this embodiment, the signal light L1 and the control light L2 are selected to have different wavelengths, and the wavelength of the signal light L1 is selected to be reflected by the first and second mirrors 9A and 9B. The wavelength of the light L2 is selected to be transmitted through the first and second mirrors 9A and 9B.

  Further, the composition of the nonlinear optical medium 2, the light intensity and wavelength of the signal light L1, and the light intensity and wavelength of the control light L2 cause a spatial light soliton effect in the nonlinear optical medium 2 with respect to the signal light L1. Instead, the non-linear optical medium 2 is set to produce a spatial light soliton effect with respect to the control light L2.

  The optical switching system 1 configured as described above operates as follows. First, when only the signal light L1 is incident on the nonlinear optical medium 2 from the communication light source 5, the nonlinear optical medium 2 of the present embodiment does not generate a spatial light soliton effect on the signal light L1, and therefore, as shown in FIG. In addition, as the signal light L1 propagates through the nonlinear optical medium 2, the size of its cross section is widened by the diffraction effect. At this time, the first and second mirrors 9A and 9B reflect the relatively weak part toward the end of the signal light L1, and the first and second light receivers 6A and 6B have weak signals having substantially the same intensity. The light L1 is detected.

  Next, when the signal light L1 is incident on the nonlinear optical medium 2 from the communication light source 5, and the first control light L2a is incident on the first output port 4A of the nonlinear optical medium 2 from the first control light source 7A, As a result, the signal light L1 is guided to the first light receiver 6A side. Since the first mirror 9A transmits the first control light L2a, the first control light L2a enters the nonlinear optical medium 2. The nonlinear optical medium 2 causes a change in refractive index, that is, an increase in refractive index with respect to the first control light L2a, and the light is attracted to a region having a high refractive index. Therefore, the first control light L2a is the nonlinear optical medium 2 A spatial light soliton effect is generated therein, and the first control light L2a forms a beam that does not spread spatially in the nonlinear optical medium 2 as shown in FIG.

  Here, the signal light L1 output from the communication light source 5 and incident on the nonlinear optical medium 2 from the surface opposite to the first control light L2a is the light beam of the first control light L2a in the nonlinear optical medium 2. 4 and guided along the propagation path of the first control light L2a as shown in FIG. 4, in other words, the propagation path of the first control light L2a is reversed. Proceed to trace. That is, in the nonlinear optical medium 2, a region where the refractive index increases along the propagation path of the first control light L <b> 2 a is generated. When entering L1, the signal light L1 propagates in a form guided to the refractive index change region created by the first control light L2a. In addition, since the signal light L1 is confined and propagated in the refractive index increasing region (that is, the waveguide), the spatial spread of the signal light L1 is reduced. The first mirror 9A reflects the signal light L1 emitted from the first output port 4A of the nonlinear optical medium 2 toward the first light receiver 6A. Thus, the first light receiver 6A can detect the signal light L1 with a stronger intensity than the second light receiver 6B.

  Conversely, when the output of the first control light source 7A is stopped and the second control light L2b is output from the second control light source 7B, the signal light L1 is guided to the second control light L2b side, and the second light receiver 6B can detect the signal light L1 with stronger intensity than the first light receiver 6A.

  Therefore, by appropriately controlling the first control light L2a and the second control light L2b, the signal light L1 can be efficiently incident on the desired light receiving means 6, and an optical switch can be realized. That is, while the outputs of both the first control light source 7A and the second control light source 7B are stopped, the first light receiver 6A and the second light receiver 6B receive the signal light L1 having the same intensity, and the second While the output of the control light source 7B is stopped and the first control light L2a is output from the first control light source 7A, the first light receiver 6A receives the signal light L1 with a stronger intensity than the second light receiver 6B. While the output of the first control light source 7A is stopped and the second control light L2b is output from the second control light source 7B, the second light receiver 6B has a stronger signal than the first light receiver 6A. The light L1 is received.

  Note that when the control light L2 has different wavelengths and light intensities, and the plurality of control lights L2 are incident on the nonlinear optical medium 2 at the same time, the signal light L1 is the specific control light in the nonlinear optical medium 2. It may be guided to the L2 side (that is, a region having a higher refractive index). In this case, priority can be set for a plurality of light receivers.

  According to the optical switching method and the optical switching system 1 described above, the signal light L1 is guided to the incident end of the control light L2 while reducing the spatial spread of the signal light L1 by the spatial light soliton effect, and the propagation thereof Since the tip can be switched, a condensing lens or the like for reducing the beam diameter is unnecessary, and the optical switch can be downsized and the optical switching device can be integrated. In addition, there is no need for a special and precise process in which an electrode is provided in the nonlinear optical medium 2 that is a switching element or a fixed waveguide is manufactured, so that the cost of the optical switch can be reduced. Furthermore, since the waveguide according to the present invention is not a fixed one but a variable one generated by the control light L2, the propagation path of the signal light L1 can be freely controlled. It is possible to easily cope with the setting change of the input port 3. Further, the first control light source 7A and the first light receiver 6A are configured as a single unit receiver, and similarly, the second control light source 7B and the second light receiver 6B are configured as a single unit receiver. In this case, it is possible to realize a new optical switching system 1 that does not exist in the past, by which the receiving device that desires to receive the signal light L1 can output the control light L2 by itself to receive the signal light L1. In addition, since the optical switch of the present invention is switched by the control light L2, unlike the type in which the electrode is built in the optical element, there is no problem of causing malfunction even in a place where a strong electric or magnetic field acts, and a temperature gradient is given. Therefore, the responsiveness can be improved as compared with the optical switch that performs switching.

  Furthermore, other embodiments of the present invention will be described below. In other embodiments described below, configurations similar to those in the above-described embodiment are denoted by the same reference numerals, detailed description thereof is omitted, and structures and the like unique to each embodiment will be described.

  FIG. 5 shows an optical switching system 1 according to the second embodiment of the present invention. In the optical switching system 1, the signal light L 1 and the control light L 2 are transmitted by the optical fiber 10 outside the nonlinear optical medium 2. According to this configuration, in the nonlinear optical medium 2, the spatial spread of the signal light L1 and the control light L2 can be reduced by the spatial light soliton effect, and in addition to the signal light outside the nonlinear optical medium 2, Since L1 and the control light L2 are confined and transmitted in the optical fiber 10, the spatial spread of these lights can be greatly reduced, and the spread can be minimized. In the example of FIG. 5, both the signal light L1 and the control light L2 are transmitted to the nonlinear optical medium 2 via the optical fiber 10, but only one of the signal light L1 and the control light L2 is transmitted to the optical fiber 10. It may be transmitted to the nonlinear optical medium 2 via

  This optical switching system 1 has an optical circulator 11 as the optical path setting means 8. The optical switching system 1 includes a first optical fiber 10A that transmits light between the communication light source 5 and the input port 3 of the nonlinear optical medium 2, a first output port 4A of the nonlinear optical medium 2, and a first output port 4A. A second optical fiber 10B that transmits light between the first port 12 of the optical circulator 11A and a third light that transmits light between the second port 13 of the first optical circulator 11A and the first light receiver 6A. A fiber 10C, a fourth optical fiber 10D that transmits light between the third port 14 of the first optical circulator 11A and the first control light source 7A, a second output port 4B of the nonlinear optical medium 2, and a second light A fifth optical fiber 10E that transmits light between the first port 12 of the circulator 11B and a sixth optical fiber that transmits light between the second port 13 of the second optical circulator 11B and the second light receiver 6B. It has a fiber 10F, and a seventh optical fiber 10G for transmitting light between the third port 14 of the second optical circulator 11B and the second control light source 7B.

  The optical circulator 11 transmits light to only one row and transmits light input to the first to third ports 12, 13, and 14 immediately from the port where the light is input toward the one row. This is a known device that outputs from a port. The first optical circulator 11 </ b> A outputs the light input from the third port 14 only from the first port 12, and outputs the light input from the first port 12 only from the second port 13. Accordingly, the first control light L2a emitted from the first control light source 7A passes through the fourth optical fiber 10D, the first optical circulator 11A, and the second optical fiber 10B, and the first output port 4A of the nonlinear optical medium 2 is output. Is incident on. Further, the signal light L1 emitted from the first output port 4A of the nonlinear optical medium 2 is transmitted to the first light receiver 6A via the second optical fiber 10B, the first optical circulator 11A, and the third optical fiber 10C. . Similarly, the second optical circulator 11 </ b> B outputs light input from the third port 14 only from the first port 12, and outputs light input from the first port 12 only from the second port 13. Therefore, the second control light L2b emitted from the second control light source 7B passes through the seventh optical fiber 10G, the second optical circulator 11B, and the fifth optical fiber 10E, and the second output port 4B of the nonlinear optical medium 2. Is incident on. The signal light L1 emitted from the second output port 4B of the nonlinear optical medium 2 is transmitted to the second light receiver 6B via the fifth optical fiber 10E, the second optical circulator 11B, and the sixth optical fiber 10F. . The basic operation of the optical switching system 1 shown in FIG. 5 is the same as that of the optical switching system 1 shown in FIG.

  The above-described embodiment is an example of a preferred embodiment of the present invention, but is not limited thereto, and various modifications can be made without departing from the gist of the present invention. For example, in the above-described embodiment, the nonlinear optical medium 2 has two output ports 4 (in other words, the incident end of the control light L2), but the number of output ports 4 may be three or more. In this case, it is desirable that the intensity of the control light L2 incident on each output port 4 is not uniform, but the intensity of the control light L2 that is further away from the optical axis of the signal light L1 is increased. By configuring in this way, even the control light L2 outside the optical axis of the signal light L1 can reliably attract the signal light L1 and guide it to the target output port 4. A plurality of optical switches according to the present invention may be connected in cascade. That is, the signal light L <b> 1 output from the nonlinear optical medium 2 may be input to the input port 3 of another nonlinear optical medium 2. In this case, the optical switching element (nonlinear optical medium 2) of the downstream optical switching system 1 serves as the light receiving means 6 viewed from the upstream optical switching system 1.

It is a block diagram which shows one Embodiment of the optical switching method and optical switching system of this invention. 2 shows a state in which only signal light is incident on a nonlinear optical medium in the optical switching system of FIG. FIG. 2 shows a part of the optical switching system of FIG. 1 and shows a state in which control light is incident on a nonlinear optical medium. 2 shows a state in which signal light is attracted to control light in the optical switching system of FIG. It is a block diagram which shows other embodiment of the optical switching method and optical switching system of this invention. It is a conceptual diagram which shows a mode that the light which propagates in an optical medium spreads spatially by a diffraction effect. It is a conceptual diagram which shows a mode that the light which propagates in a nonlinear optical medium is confine | sealed in the waveguide which self formed by the spatial light soliton effect, and propagates. It is a conceptual diagram which shows the principle of the conventional optical switch, (a) shows a mode that signal light entered into the optical crystal used as a switching element, (b) is the said optical crystal from the direction different from signal light. A state in which the propagation direction of the signal light is changed by entering the control light is shown. It is a conceptual diagram which shows the principle of the conventional optical switch incorporating a waveguide and an electrode.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Optical switching system 2 Nonlinear optical medium 3 Input port 4 Output port 5 Communication light source 6 Light receiving means 7 Control light source 8 Optical path setting means 10 Optical fiber L1 Signal light L2 Control light

Claims (6)

  An input port and a plurality of output ports are defined in a nonlinear optical medium having physical properties exhibiting a spatial light soliton effect, and control light is incident on the output port selected from the plurality of output ports and refracted into the nonlinear optical medium. Forming a region with an increased rate, and drawing the signal light incident on the input port to the refractive index increasing region and guiding it to the selected output port, thereby switching the output destination of the signal light, Optical switching method.   The optical switching method according to claim 1, wherein the signal light or the control light is transmitted by an optical fiber outside the nonlinear optical medium.   3. The optical switching method according to claim 1, wherein a sensitivity of the nonlinear optical medium to change in refractive index is greater for the control light than for the signal light.   A nonlinear optical medium having physical properties exhibiting a spatial light soliton effect; an input port and a plurality of output ports set in the nonlinear optical medium; a communication light source that inputs signal light to the input port; and an output from the output port A plurality of light receiving means for receiving the signal light, a control light source for entering control light to the output port, the control light from the control light source to the output port, and from the output port to the output port An optical path setting means for transmitting the signal light to the light receiving means, and a region in which the control light is incident on an output port selected from the plurality of output ports and a refractive index is increased in the nonlinear optical medium. Forming and guiding the signal light incident on the input port to the refractive index increasing region and guiding it to the selected output port, thereby switching the output destination of the signal light. Optical switching system, characterized in that changing.   5. The optical switching system according to claim 4, wherein the signal light or the control light is transmitted by an optical fiber outside the nonlinear optical medium. 6. The optical switching system according to claim 4, wherein the sensitivity of the nonlinear optical medium for changing the refractive index is greater for the control light than for the signal light.

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