WO2014141469A1

WO2014141469A1 - Wavelength selection switch

Info

Publication number: WO2014141469A1
Application number: PCT/JP2013/057413
Authority: WO
Inventors: 英久田澤; 学塩崎; 健一郎高橋
Original assignee: 住友電気工業株式会社
Priority date: 2013-03-15
Filing date: 2013-03-15
Publication date: 2014-09-18

Abstract

A wavelength selection switch is provided with: a port array (14) in which an input port (12) and an output port (13) are arranged in the direction of the x-axis; a light dispersion element (18) that disperses signal light (L1) input from the input port (12) in the y-axis direction according to wavelength; a light collecting lens (19) that collects light of each of the signal light beams (L1) dispersed by the light dispersion element (18); a light polarizing element (15) that polarizes each of the signal light beams (L1) collected by the light collecting lens (19) toward the output port (13); a relay optical system (16) that makes the beam waist position (P1) for the signal light (L1) for the x-axis direction substantially match the front side focal point of the collecting lens (19); and an anamorphic optical system (17) that expands the beam size ratio of the signal light (L1) in the light polarizing element (15) for the x-axis direction with respect to the beam size for the y-axis direction.

Description

Wavelength selective switch

The present invention relates to a wavelength selective switch.

An optical device described in Patent Document 1 includes a plurality of input and output ports provided by a fiber coupling collimator, an anamorphic system that converts signal light from the input port into a beam having a predetermined beam profile, A diffraction grating for spatially separating the beam, a focusing optical device for converting the beam separated by the diffraction grating into a channel beam having an elongated beam profile, and an elongated shape adapted to the beam profile of the channel beam And an array of micromirrors and a control system that controls the rotation of the micromirrors to switch the channel beam to a predetermined output port.

Special table 2008-536168

In the optical device described in Patent Document 1, as an example of an anamorphic system for providing an elongated beam profile on a micromirror, a plurality of biconical, cylindrical, or annular lenses are used. Has been proposed. However, in that case, in order to increase the aspect ratio of the beam size, it is necessary to use a large number of the above-described lenses and the like, and the optical path length becomes long and the structure becomes complicated. Therefore, it is desirable to be able to adjust the aspect ratio of the beam size without complicating the structure. On the other hand, in the above technical field, it is desired to realize a multi-port without increasing the size of the apparatus.

The present invention has been made in view of such circumstances, and the aspect ratio of the beam size can be adjusted without complicating the structure, and a multi-port can be realized without increasing the size of the apparatus. An object is to provide a wavelength selective switch.

One aspect of the present invention relates to a wavelength selective switch. The wavelength selective switch includes a port array configured by arranging an input port for inputting signal light and an output port for outputting signal light in a first direction, and the signal light input from the input port in the first direction. A spectral element that splits light in a second direction different from the above, a condensing element that condenses each of the signal light dispersed by the spectroscopic element, and each of the signal light condensed by the condensing element toward the output port A deflecting optical deflection element, a relay optical system that adjusts the beam waist position of the signal light input from the input port in the first direction so as to substantially coincide with the front focal point of the condensing element, the relay optical system, and the optical Are arranged in front of or behind the relay optical system so as to be connected to each other, and the ratio of the beam size in the first direction to the beam size in the second direction of the signal light in the optical deflection element is expanded. Characterized in that it comprises the anamorphic optical system, a.

In this wavelength selective switch, the relay optical system adjusts the beam waist position so that the beam waist position of the signal light substantially coincides with the front focal point of the condensing element in the first direction. For this reason, since the spread of the beam due to diffraction can be suppressed in the first direction (arrangement direction of the input port and the output port) of the signal light at the output port, the beam size at the output port can be reduced. Therefore, according to this wavelength selective switch, it is possible to increase the number of ports without increasing the size of the apparatus. On the other hand, in this wavelength selective switch, the beam in the first direction with respect to the beam size in the second direction of the signal light in the optical deflection element is detected by the anamorphic optical system arranged at the front stage or the rear stage of the relay optical system. The ratio of sizes (hereinafter sometimes referred to as aspect ratio) is enlarged. In this way, it is possible to flexibly design the aspect ratio of the beam size in the optical deflecting element of the signal light condensed by the condensing element. Therefore, according to this wavelength selective switch, for example, the aspect ratio of the beam size of the signal light in the optical deflection element can be adjusted without increasing the optical path length and complicating the structure.

In the wavelength selective switch according to one aspect of the present invention, the relay optical system includes a first element having optical power in the first direction and the second direction, and a second element having optical power in at least the first direction. These elements may be included. Furthermore, the input port and the output port include an optical fiber and a collimating lens optically connected to the optical fiber, and the front focal point of the first element is the rear focal point of the collimating lens with respect to the first direction. And the front focal point of the second element is arranged to substantially coincide with the rear focal point of the first element in the first direction, and the rear side of the second element The focal point may be arranged so as to substantially coincide with the front focal point of the light collecting element. In this case, it becomes easy to adjust the beam waist position of the signal light so as to substantially coincide with the front focal point of the light collecting element in the first direction.

In the wavelength selective switch according to one aspect of the present invention, the second element has optical power only in the first direction, and the first element with respect to the beam size in the second direction of the signal light in the optical deflection element. The ratio of beam sizes with respect to direction can be expanded. In this case, the aspect ratio can be adjusted while adjusting the beam waist position in the first direction by providing the relay optical system also with a function of expanding the aspect ratio of the beam size of the signal light in the optical deflection element. It becomes easy.

In the wavelength selective switch according to one aspect of the present invention, the anamorphic optical system is arranged at the rear stage of the relay optical system, and the first element is signal light input from the input port and incident on the first element. The beam size at the beam waist position of the signal light emitted from the first element can be made relatively larger than the beam size at the beam waist position. In this way, for example, even when the aspect ratio of the signal light beam size is increased in an anamorphic optical system, an increase in loss can be suppressed.

In the wavelength selective switch according to one aspect of the present invention, the relay optical system and the anamorphic optical system constitute a beam waist position adjusting optical system that adjusts the beam waist position of the signal light. The system is arranged at the rear stage of the relay optical system, and the relay optical system adjusts the beam waist position of the signal light input from the input port in the second direction so as to be the rear stage of the anamorphic optical system. be able to. Further, the second element may have optical power in the first direction and the second direction. In this case, it is possible to make the aspect ratio of the beam size of the signal light in the optical deflection element different from the aspect ratio conversion magnification of the beam size in the anamorphic optical system. Therefore, according to this wavelength selective switch, for example, the aspect ratio of the beam size of the signal light can be adjusted without increasing the optical path length.

In the wavelength selective switch according to one aspect of the present invention, the relay optical system and the anamorphic optical system constitute a beam waist position adjusting optical system that adjusts the beam waist position of the signal light. The system is arranged at the subsequent stage of the relay optical system, and the relay optical system can adjust the beam waist position of the signal light input from the input port in the second direction so as to be at the front stage of the collimating lens. . Furthermore, the second element may have optical power only in the first direction. Also in this case, the aspect ratio of the beam size of the signal light in the optical deflection element can be made different from the aspect ratio conversion magnification of the beam size in the anamorphic optical system. Therefore, according to this wavelength selective switch, for example, the aspect ratio of the beam size of the signal light can be adjusted without increasing the optical path length.

In the wavelength selective switch according to one aspect of the present invention, the ratio of the beam size in the first direction to the beam size in the second direction of the signal light in the optical deflection element is the second direction in the anamorphic optical system. It is assumed that the signal beam beam size is about 3 times or more of the magnification of the signal light beam. Further, the distance between the beam waist position of the signal light input from the input port and entering the light collecting element and the light collecting element changes the beam size of the signal light in the light deflecting element when the distance is changed. It can be larger than the changing point distance. In this case, a beam having a sufficiently high aspect ratio can be formed in the optical deflection element. The change point distance here is a threshold value of the distance between the beam waist position of the signal light input from the input port and incident on the light collecting element and the light collecting element, and the distance is gradually changed. This is the distance at which the beam size of the signal light in the optical deflection element starts to change.

In the wavelength selective switch according to one aspect of the present invention, the optical deflection element independently receives each of the signal lights dispersed by the spectral element by the plurality of optical deflection element elements arranged along the first direction. The relay optical system and the anamorphic optical system are deflected toward the output port by performing phase modulation, and the ratio of the beam size in the first direction to the beam size in the second direction of the signal light in the optical deflection element Can be 30 or more. In this case, the optical path of the signal light can be suitably controlled by the optical deflection element that controls the optical path of the signal light based on such a principle.

In the wavelength selective switch according to one aspect of the present invention, the anamorphic optical system may be composed of at least a pair of prisms. At this time, in the wavelength selective switch according to one aspect of the present invention, the incident angle of the signal light input from the input port to the prism can be 70 ° or more. In this case, in the anamorphic optical system, the signal light can be sufficiently expanded in the second direction, and the aspect ratio of the beam size of the signal light in the optical deflection element can be sufficiently increased.

In the wavelength selective switch according to one aspect of the present invention, the incident angle of the signal light input from the input port to the prism can be substantially equal to the Brewster angle. In this case, reflection of P-polarized light contained in the signal light can be reduced.

In the wavelength selective switch according to one aspect of the present invention, the refractive index of the prism can be 1.5 or more. In this case, even if the signal light is incident on the prism at a large incident angle, the reflected light can be relatively reduced. For this reason, it is easy to set the incident angle of the signal light to the prism as described above.

In the wavelength selective switch according to one aspect of the present invention, the refractive index of the prism may be 3 or more. In this case, it can be suitably realized that the incident angle of the signal light to the prism is as described above.

The wavelength selective switch according to one aspect of the present invention can further include a polarization diversity module disposed in the previous stage of the relay optical system. In this case, polarization dependent loss can be reduced. In particular, the polarization diversity module can be miniaturized by disposing it before the relay optical system.

In the wavelength selective switch according to one aspect of the present invention, the polarization diversity module includes a polarization beam splitter that separates the signal light in the second direction according to the polarization direction, and signal light separated by the polarization beam splitter. A polarization rotation element that adjusts one polarization direction of the optical signal to the other polarization direction, and an optical path adjustment element that adjusts one optical path length of the signal light separated by the polarization beam splitter to the other optical path length. . In this case, since the signal light is polarized and separated in the spectral direction, the size of the wavelength selective switch in the first direction can be prevented from increasing.

According to the present invention, it is possible to provide a wavelength selective switch in which the aspect ratio of the beam size of signal light can be adjusted without complicating the structure and the number of ports can be increased without increasing the size of the apparatus. it can.

It is a schematic diagram which shows the structure of 1st Embodiment of the wavelength selective switch which concerns on 1 side of this invention. It is a schematic diagram which shows the structure of 2nd Embodiment of the wavelength selective switch which concerns on 1 side of this invention. It is a figure which shows the Gaussian beam which propagates through a lens. It is a diagram illustrating a distance S _1P from the beam waist relay position P2 to the prism installation position PP. The distance S _1P from the beam waist relay position P2 to the prism installation position PP as a parameter, a graph showing the results of calculating the y-axis direction beam size in the optical deflection element. It is a graph which shows the relationship between distance _S1L from a beam waist position to a condensing lens, and the y-axis direction beam size in an optical deflection element. It is a graph which shows the relationship between distance _S1L from a beam waist position to a condensing lens, and the y-axis direction beam size in an optical deflection element. It is a schematic diagram which shows the structure of the modification of the wavelength selective switch shown by FIG.

Hereinafter, an embodiment of a wavelength selective switch according to an aspect of the present invention will be described in detail with reference to the drawings. In the description of the drawings, the same elements or corresponding elements are denoted by the same reference numerals, and redundant description is omitted.
[First Embodiment]

FIG. 1 is a schematic diagram showing a configuration of a first embodiment of a wavelength selective switch according to one aspect of the present invention. In the following drawings, an orthogonal coordinate system S is shown. FIG. 1A is a diagram from the y-axis direction of the orthogonal coordinate system S, and is a diagram illustrating a schematic configuration of the wavelength selective switch in a plane (xz plane) including the x-axis and the z-axis. . FIG. 1B is a diagram from the x-axis direction of the orthogonal coordinate system S, and is a diagram illustrating a schematic configuration of the wavelength selective switch in a plane (xz plane) including the y-axis and the z-axis. .

As shown in FIG. 1, the wavelength selective switch 1 according to the first embodiment includes a port array 14 configured by arranging input ports 12 and output ports 13 in the x-axis direction (first direction), and an input. An optical deflection element 15 that deflects the signal light L1 input from the port 12 toward the output port 13 is provided. The wavelength selective switch 1 includes a relay optical system 16, an anamorphic optical system 17, a spectroscopic element 18, and a condenser lens that are sequentially arranged on the optical path of the signal light L 1 from the input port 12 toward the optical deflection element 15. (Condensing element) 19 is provided. Hereinafter, the input port 12 side on the optical path of the signal light L1 from the input port 12 toward the light deflection element 15 is referred to as a front stage and a front side, and the light deflection element 15 side is referred to as a rear stage and a rear side.

The port array 14 includes, for example, one input port 12 and a plurality of output ports 13. The input port 12 can include, for example, an optical fiber 12a and a collimating lens 12b optically connected to the optical fiber 12a. The input port 12 receives the signal light L1 that is, for example, wavelength multiplexed light. The output port 13 can include, for example, an optical fiber 13a and a collimating lens 13b optically connected to the optical fiber 13a. For example, the output port 13 outputs the signal light L1 of each wavelength component deflected by the light deflecting element 15.

The relay optical system 16 is optically connected to the

collimating lenses

12 b and 13 b and the condenser lens 19. The relay optical system 16 includes a first lens (first element) 16a and a second lens (second element) 16b. The first lens 16a is a rotationally symmetric lens such as a convex spherical lens having optical power in the x-axis direction and the y-axis direction (second direction), for example. The first lens 16a is disposed in front of the second lens 16b, and the front focal point of the first lens 16a is disposed so as to substantially coincide with the rear focal points of the

collimating lenses

12b and 13b. That is, the first lens 16a is arranged at a position separated from the

collimating lenses

12b and 13b by the focal length f1 of the

collimating lenses

12b and 13b and the focal length f2 of the first lens 16a. Note that the first element and the second element have optical power (that is, refractive power) as described, and a reflection type element such as a mirror in addition to a transmission type element such as a lens. Can be applied.

The second lens 16b has optical power at least in the x-axis direction. The second lens 16b is, for example, a cylindrical lens having optical power only in the x-axis direction. The front focal point of the second lens 16b is disposed so as to substantially coincide with the rear focal point of the first lens 16a. Further, the rear focal point of the second lens 16 b is disposed so as to substantially coincide with the front focal point of the condenser lens 19. That is, the second lens 16b is located away from the first lens 16a by the focal length f2 of the first lens 16a and the focal length f3 of the second lens 16b, and is the position of the second lens 16b. They are arranged at positions separated from the condensing lens 19 by the focal length f3 and the focal length f4 of the condensing lens 19. Accordingly, the signal light L1 emitted from the collimating lens 12b of the input port 12 enters the first lens 16a and then enters the second lens 16b.

The anamorphic optical system 17 is arranged in front of or behind the relay optical system 16. In the present embodiment, an embodiment in which an anamorphic optical system 17 is arranged at the subsequent stage of the relay optical system 16 is shown. The anamorphic optical system 17 receives the signal light L1 emitted from the relay optical system 16 (second lens 16b), and changes the beam size of the signal light L1 in the y-axis direction (in the yz plane). ) Enlarge and emit. The anamorphic optical system 17 has a function of converting and outputting the aspect ratio of an input beam, and can be configured by combining a prism pair, a cylindrical lens, a cylindrical mirror, or the like. In the present embodiment, for example, a pair of

prisms

17a and 17b is illustrated.

The incident angle of the signal light L1 emitted from the relay optical system 16 (that is, the signal light L1 emitted from the collimating lens 12b of the input port 12) to the prism 17a on the preceding stage can be set to, for example, 70 ° or more. . In that case, the beam size can be sufficiently expanded in the y-axis direction.

Further, the incident angle of the signal light L1 emitted from the relay optical system 16 (that is, the signal light L1 emitted from the collimating lens 12b of the input port 12) to the prism 17a on the front stage is substantially equal to, for example, the Brewster angle. can do. In that case, the reflected light due to the polarization dependence of the signal light can be reduced (the reflection of the P-polarized light included in the signal light L1 can be reduced).

The refractive index of the prism 17a (prism 17b) can be, for example, 1.5 or more. The refractive index of the prism 17a (prism 17b) can be set to 3 or more, for example. In these cases, even if the signal light L1 is incident on the prism 17a at a large incident angle, the reflected light can be relatively reduced. For this reason, it is easy to set the incident angle of the signal light L1 to the prism 17a as described above. In particular, if the refractive indexes of the

prisms

17a and 17b are 3 or more, the incident angle of the signal light L1 to the prism 17a can be set to be 70 ° or more and substantially equal to the Brewster angle.

The spectroscopic element 18 receives the signal light L1 that has been input from the input port 12 and passed through the relay optical system 16 and the anamorphic optical system 17, and enters the y-axis direction (second direction) according to the wavelength (that is, the second direction). , In the yz plane). In the spectroscopic element 18, the signal light L1 may be split into a plurality of signal lights L1 for each wavelength, but only a single signal light L1 is illustrated here. As the spectroscopic element 18, for example, a diffraction grating can be used. The spectroscopic element 18 is disposed at the front focal point Pf of the condenser lens 19. More specifically, the spectroscopic element 18 is located away from the second lens 16b by the focal length f3 of the second lens 16b of the relay optical system 16 and has a focal length f4 of the condenser lens 19. It is arranged at a position away from the condenser lens 19 by the amount.

The condensing lens 19 receives the signal light L1 that is split and emitted by the spectroscopic element 18, and the light deflecting element 15 collimates the signal light L1 in the x-axis direction (that is, in the xz plane), for example. And condensing on the light deflection element 15 in the y-axis direction (that is, in the yz plane). The condenser lens 19 may be a rotationally symmetric lens such as a convex spherical lens having optical power in the x-axis direction and the y-axis direction.

The light deflection element 15 is arranged at the rear focal point of the condenser lens 19. That is, the light deflection element 15 is arranged at a position separated from the condenser lens 19 by the focal length f4 of the condenser lens 19. The light deflection element 15 receives the signal light L1 collected by the condenser lens 19 and deflects it toward a predetermined output port 13 corresponding to the wavelength, for example. For this purpose, the light deflection element 15 has a plurality of light deflection element elements arranged along the x-axis direction. Then, the optical deflection element 15 deflects the signal light L1 split by the spectroscopic element 18 by the optical deflection element element toward the output port 13 by independently performing phase modulation.

As such an optical deflecting element 15, for example, LCOS (Liquid Cristal On Silicon) can be used. In that case, among the plurality of pixels arranged in a two-dimensional array along the x-axis and the y-axis, the light deflection in which the unit of the plurality of pixels arranged in the x-axis direction contributes to the deflection of the signal light L1. It functions as an element element. Note that a MEMS (Micro Electro Mechanical Systems) element may be used as the light deflection element 15.

The signal light L1 deflected by the light deflecting element 15 is incident on a predetermined output port 13 via the condenser lens 19, the spectroscopic element 18, the anamorphic optical system 17, and the relay optical system 16, and is output. .

Subsequently, the relay optical system 16 and the anamorphic optical system 17 will be described in detail. The relay optical system 16 adjusts the beam waist position P1 of the signal light (that is, the signal light emitted from the collimating lens 12b) L1 input from the input port 12. More specifically, as described above, the relay optical system 16 includes the first lens 16a having optical power in the x-axis direction and the y-axis direction, and the second lens 16b having optical power in at least the x-axis direction. It is comprised including. In the present embodiment, the first lens 16a is arranged so that the focal points thereof are substantially coincident with the

collimating lenses

12b and 13b in the x-axis direction, and the second lens 16b is first in the x-axis direction. The lens 16a and the condenser lens 19 are arranged so that their focal points are substantially coincident with each other. Thereby, the relay optical system 16 changes the beam waist position P1 of the signal light L1 input from the input port 12 in the x-axis direction (that is, in the xz plane) to the front focal point (that is, the condensing lens 19). The spectral element 18 is adjusted so that it substantially coincides with the installation position Pf.

The second lens 16b has optical power only in the x-axis direction (that is, in the xz plane), and has optical power in the y-axis direction (that is, in the yz plane). Not. For this reason, the signal light L1 incident on the condenser lens 19 has a beam size that is relatively small with respect to the y-axis direction in the x-axis direction. Therefore, the signal light L1 irradiated to the light deflection element 15 via the condenser lens 19 has a relatively enlarged beam size in the x-axis direction with respect to the beam size in the y-axis direction.

The anamorphic optical system 17 is disposed upstream or downstream (in the present embodiment) of the relay optical system 16 and optically connected to the relay optical system 16. The anamorphic optical system 17 relatively enlarges the beam size in the y-axis direction. Note that the beam shapes of the signal light L1 in the x-axis direction and the y-axis direction are reversed by the condenser lens 19, so that the anamorphic optical system 17 results in the y of the signal light L1 in the light deflecting element 15 as a result. The ratio (aspect ratio) of the beam size in the x-axis direction to the beam size in the axial direction is enlarged.

Thus, not only the anamorphic optical system 17 but also the relay optical system 16 has a function of expanding the ratio of the beam size in the x-axis direction to the beam size in the y-axis direction of the signal light L1 in the optical deflection element 15. If it is given, it becomes easy to increase the aspect ratio of the beam size.

The first lens 16a of the relay optical system 16 has a beam waist position of the signal light L1 input from the input port 12 (collimator lens 12b) and incident on the first lens 16a in the x-axis direction and the y-axis direction. The beam size at the beam waist position Pe of the signal light L1 emitted from the first lens 16a is relatively larger than the beam size at P1. In this way, for example, even when the aspect ratio of the beam size of the signal light L1 is increased in the relay optical system 16 and the anamorphic optical system 17, an increase in loss can be suppressed.

In the wavelength selective switch 1 as described above, the relay optical system 16 makes the beam waist position P1 of the signal light L1 input from the input port 12 coincide with the front focal point of the condenser lens 19 in the x-axis direction. adjust. Therefore, according to the wavelength selective switch 1, it is possible to increase the number of ports without increasing the size of the device.

In the wavelength selective switch 1, the relay optical system 16 is also provided with a function of expanding the aspect ratio of the beam size of the signal light L 1 in the optical deflection element 15. For this reason, according to the wavelength selective switch 1, it is possible to adjust (enlarge) the aspect ratio of the beam size without increasing the optical path length and complicating the structure, for example.

In particular, in this wavelength selective switch 1, if the beam size in the y-axis direction of the signal light L1 in the optical deflection element 15 is made smaller by the relay optical system 16 and the anamorphic optical system 17 (the previous stage of the condenser lens 19). If the beam size in the y-axis direction is made larger), the aspect ratio of the beam size of the signal light L1 in the optical deflection element 15 can be made sufficiently high. More specifically, the relay optical system 16 and the anamorphic optical system 17 can set the aspect ratio of the beam size of the signal light L1 in the optical deflection element 15 to 30 or more. Therefore, for example, it is suitable when a high aspect ratio is required in the beam size at the optical deflection element 15 such as when LCOS is used as the optical deflection element 15.

For example, in the wavelength selective switch 1, when the optical deflection element 15 requires an aspect ratio of about 40 (that is, in the optical deflection element 15, the beam size in the x-axis direction of the signal light L1 is a beam in the y-axis direction). In the case where the magnification of the beam size in the y-axis direction of the anamorphic optical system 17 is about 8 times, it is given to the relay optical system 16. The magnification of the function of enlarging the beam size in the x-axis direction with respect to the beam size in the y-axis direction of the signal light L1 in the optical deflection element 15 may be about 5 times.
[Second Embodiment]

FIG. 2 is a schematic diagram showing the configuration of the second embodiment of the wavelength selective switch according to one aspect of the present invention. As shown in FIG. 2, the wavelength selective switch 1A according to the present embodiment is different from the wavelength selective switch 1 according to the first embodiment in that a beam waist position adjusting optical system 20A is provided. The beam waist position adjusting optical system 20A adjusts the beam waist position P1 of the signal light L1 input from the input port 12. Unlike FIG. 1, in FIG. 2, in order to explain the beam waist position of the signal light L1, the illustration of the beam size expansion in the y-axis direction in the anamorphic optical system 17 is omitted.

The beam waist position adjusting optical system 20A includes a relay optical system 16A and an anamorphic optical system 17. The relay optical system 16 A is disposed in front of the anamorphic optical system 17. Further, the relay optical system 16A is optically connected to the

collimating lenses

12b and 13b and the condenser lens 19. The relay optical system 16A is different from the relay optical system 16 in that it includes a second lens 16c instead of the second lens 16b.

The second lens 16c is, for example, a rotating contrast lens having optical power in the x-axis direction and the y-axis direction. The front focal point of the second lens 16c is disposed so as to substantially coincide with the rear focal point of the first lens 16a. Further, the rear focal point of the second lens 16 c is disposed so as to substantially coincide with the front focal point of the condenser lens 19. That is, the second lens 16c is located away from the first lens 16a by the focal length f2 of the first lens 16a and the focal length f3 of the second lens 16c, and is the position of the second lens 16c. They are arranged at positions separated from the condensing lens 19 by the focal length f3 and the focal length f4 of the condensing lens 19.

Such a relay optical system 16A adjusts the beam waist position P1 of the signal light L1 input from the input port 12 in the y-axis direction so as to be positioned at the subsequent stage of the anamorphic optical system 17.

Subsequently, details of the beam waist position adjusting optical system 20A will be described. As described above, the beam waist position adjustment optical system 20A adjusts the beam waist position P1 of the signal light (that is, the signal light emitted from the collimator lens 12b) L1 input from the input port 12. More specifically, the beam waist position adjusting optical system 20A is configured to change the beam waist position P1 of the signal light L1 input from the input port 12 in the x-axis direction (that is, in the xz plane) to the relay optical system. By relaying using 16A, adjustment is made so as to substantially coincide with the front focal point of the condenser lens 19 (that is, the installation position of the spectroscopic element 18) Pf.

On the other hand, the beam waist position adjusting optical system 20A uses the relay optical system 16A and the anamorphic optical system 17 in the y-axis direction (that is, in the yz plane) to input signal light from the input port 12. The beam waist position P1 of L1 is adjusted. The adjustment of the beam waist position in the y-axis direction will be described in detail.

As shown in FIG. 3, the following relationship is known for the light L2, which is a Gaussian beam propagating through the lens A having a focal length f (for example, “Sidney A. Self,“ Focusing of spherical Gaussian ”). beams, ”Applied
Optics, vol.22, No.5, pp.658 (1983) ").

Here, S ₁ is a distance from the beam waist position A ₁ of the light L 2 incident on the lens A to the lens A, and S ₂ is a distance from the beam waist position A ₂ of the light L ₂ emitted from the lens A to the lens A. It is the distance to. Also, _{D 1} is the beam radius at the beam waist position _{A 1} of the light L2, _{D 2} is the beam radius at the beam waist position _{A 2} of the light L2. Note that λ is the wavelength of the light L2.

According to FIG. 3 and the above formula (1), the distance S ₂ from the beam waist position A ₂ of the light L ₂ emitted from the lens A to the lens A is from the beam waist position A ₁ of the light L ₂ incident on the lens A to the lens. it can be adjusted by adjusting the distance S ₁ to a. Further, according to FIG. 2 and the above equation (2), the beam radius D _{2 at} the beam waist position A ₂ of the light L ₂ emitted from the lens A is also changed from the beam waist position A ₁ of the light L ₂ incident on the lens A to the lens A. it can be adjusted by adjusting the distance S ₁ to. The present inventors have found that such a relationship is useful not only in the lens A as shown in FIG.

The beam waist position adjustment optical system 20A is, by utilizing their relationships, the y-axis direction, to adjust the distance S _1L from the beam waist position P1 of the signal light L1 input from the input port 12 to the condenser lens 19 . Figure 4 is a diagram for explaining a distance S _1P from the beam waist relay position P2 is a parameter to the prism installation position PP used for adjusting the distance S _1L. FIG. 4 shows the state of beam propagation in terms of wave optics. As shown in FIG. 4, the beam waist position adjusting optical system 20A first converts the beam waist position P1 of the signal light L1 input from the input port 12 into the prism of the anamorphic optical system 17 by the relay optical system 16A. Let it be a position (beam waist relay position) P2 subsequent to the installation position PP. That is, the beam waist position adjusting optical system 20A substantially relays the beam waist position P1 of the signal light L1 input from the input port 12 by the relay optical system 16, thereby substantially setting the prism installation position PP (anamorphic optical). Adjust so that it is located in the latter part of the system 17).

Distance S _1P from the beam waist relay position P2 to the prism installation position PP is considered to correspond to the distance S ₁ of the relationships in the lens A described above (however, the beam waist relay position P2, later than the prism installation position PP Therefore, the distance _S1P is a negative value). By adjusting the distance S _1P appropriate, to correspond to the distance S ₂ relationship of the lens A, which distance (described above from the beam waist position of the signal light L1 emitted from the anamorphic optical system 17 to the prism installation position PP Can be adjusted).

Since the signal light L1 emitted from the anamorphic optical system 17 is incident on the condensing lens 19, adjusting the beam waist position of the signal light L1 emitted from the anamorphic optical system 17 is not possible. distance S _1L from the beam waist position of the signal light L1 incident on 19 to the condenser lens 19 _(i.e., the distance S ₁ for the condensing lens ₁₉₎ is to be adjusted. As described above, the beam waist position adjusting optical system 20A sets the beam waist position P1 of the signal light L1 incident on the anamorphic optical system 17 to the beam waist relay position P2 by the relay optical system 16A, and the distance from the prism installation position PP. As a result, the distance S _1L from the beam waist position of the signal light L1 incident on the condenser lens 19 to the condenser lens 19 is adjusted by adjusting S _1P . In FIG. 4B, f1 is the focal length of the collimating lens 12b, and f4 is the focal length of the condenser lens 19. In FIG. 4A, f2 is the focal length of the first lens 16a, and f3 is the focal length of the second lens 16c.

Here, the beam waist position adjusting optical system 20 A sets the beam waist position P 3 of the signal light L 1 incident on the condensing lens 19 to the subsequent stage of the light deflection element 15, as indicated by a one-dot chain line in FIG. To be located. In this case, the distance S _1L from the beam waist position P3 to the condensing lens 19 is a negative value.

Thus, by adjusting the distance S _1L from the beam waist position P3 of the signal light L1 incident on the condenser lens 19 to condenser lens 19, as shown in equation (3) of the above-described relationship, the condenser lens 19 (corresponding to 2 times the beam radius D ₂ of the relationships in the lens a described above) the beam size at the beam waist position of the signal light L1 emitted from the can be adjusted. That is, the beam size in the y-axis direction of the signal light L1 in the optical deflection element 15 can be adjusted. In FIG. 2B, the broken line indicates the spread of the signal light L1 when the anamorphic optical system 17 is not provided. As shown by the broken line in FIG. 2B, when there is no anamorphic optical system 17, the beam waist position P3 of the signal light L1 incident on the condenser lens 19 is, for example, It substantially coincides with the front focal point Pf.

FIG. 5 shows the distance S _1L from the beam waist position P3 of the signal light L1 incident on the condenser lens 19 to the condenser lens 19 and the light, with the distance S _1p from the beam waist relay position P2 to the prism installation position PP as a parameter. 6 is a table showing a result of calculating a beam size in the y-axis direction in the deflection element 15. FIG. 6 is a graph showing the relationship between the distance S _1L and the beam size (diameter) in the y-axis direction in the optical deflection element 15. Here, the y-axis direction beam size is the beam size in the y-axis direction of the signal light L1 emitted from the condensing lens 19 in the light deflection element 15. The following conditions are used for the calculations shown in FIGS. In the following the beam waist diameter is the beam size at the beam waist position P3 of the signal light L1 incident on the condensing lens 19, which corresponds to twice the beam radius D ₁ described above.

[Prism (Anamorphic Optical System 17)]
Magnification 8 times (2 prisms (

prisms

17a and 17b)), glass material is Si
[lens]
The focal length f1: 1.4 mm of the collimating lens 12b
Focal length f2 of the first lens 16a: 65 mm
Focal length f3 of the second lens 16c: 65 mm
Focal length f4 of the condensing lens 19: 100 mm
Beam waist diameter: 0.2654mm
[wavelength]
Wavelength of signal light L1: 0.001548 mm

As shown in FIG. 5, the beam waist position P3 of the signal light L1 incident distance _{S 1P} from the beam waist relay position P2 to the prism mounting position PP from 25mm to the condensing lens 19 is gradually increased by 10mm intervals If the absolute value of the distance _S1L to the condensing lens 19 is adjusted so as to increase, the beam size (diameter) in the y-axis direction in the light deflection element 15 gradually decreases. For example, as shown in FIG. 6, the absolute value of the y-axis direction of the beam size in the vicinity of 450mm distance S _1L is gradually beginning to decrease. That is, when the distance S _1L between the beam waist position P 3 of the signal light L 1 input from the input port 12 and entering the condenser lens 19 and the condenser lens 19 is changed, the signal light L 1 in the light deflection element 15 is changed. Here, the change point distance at which the beam size in the y-axis direction changes is about 450 mm.

Thus, by adjusting the distance S _1P from the beam waist relay position P2 to the prism installation position PP by the relay optical system 16A, consequently, to adjust the beam size in the y-axis direction of the light deflector 15 it can. For example, when the beam expansion magnification in the y-axis direction of the anamorphic optical system 17 is set to 8 times, the beam size in the x-axis direction of the light deflection element 15 is expanded by 8 times by the anamorphic optical system 17. At the same time, by making the beam size in the y-axis direction relatively small by the beam waist position adjusting optical system 20A, the aspect ratio of the beam size in the optical deflection element 15 can be made 8 times or more. For example, in the example shown in FIG. 6, when the distance S _1P is adjusted by the relay optical system 16A so that the distance S _1L is about 3000 mm, the aspect ratio of the beam size in the light deflection element 15 is about 30. it can.

Furthermore, another calculation result is shown in FIG. The following conditions are used for the calculation shown in FIG.
[Prism (Anamorphic Optical System 17)]
Magnification 8 times (2 prisms (

prisms

17a and 17b)), glass material is Si
[lens]
The focal length f1: 0.7 mm of the collimating lens 12b
Focal length f2 of the first lens 16a: 65 mm
Focal length f3 of the second lens 16c: 65 mm
Focal length f4 of the condensing lens 19: 100 mm
Beam waist diameter: 0.133mm
[wavelength]
Wavelength of signal light L1: 0.001548 mm

As can be seen from the example shown in FIG. 7, when the absolute value of the distance S _1L is adjusted to be large, the beam size in the y-axis direction of the light deflection element 15 is gradually reduced. For example, in the example shown in FIG. 7, the beam size in the y-axis direction starts to gradually decrease when the absolute value of the distance S _1L is around 180 mm. That is, the changing point distance at which the beam size in the y-axis direction of the signal light L1 in the optical deflection element 15 changes when the distance _S1L is changed is about 180 mm here.

Particularly in this case as well, the conversion magnification of the beam size in the y-axis direction of the anamorphic optical system 17 (that is, the enlargement magnification of the beam size in the x-axis direction in the light deflection element 15 via the condenser lens 19) is 8. However, the aspect ratio of the beam size of the signal light L1 in the optical deflection element 15 can be 8 times or more by making the beam size in the y-axis direction in the optical deflection element 15 relatively small. For example, in the example shown in FIG. 7, when the distance S _1P is adjusted by the relay optical system 16A so that the distance S _1L is about 1900 mm, an aspect ratio of about 30 can be realized.

As shown in FIGS. 6 and 7, the magnitude (change point distance) of the distance S _{1L at which} the beam size in the y-axis direction of the light deflecting element 15 starts to decrease is that of the signal light L 1 incident on the condenser lens 19. It also varies depending on the beam waist diameter. Therefore, in the wavelength selective switch 1A according to the present embodiment, the distance _S1L between the beam waist position P3 of the signal light L1 input from the input port 12 and incident on the condenser lens 19 and the condenser lens 19 is determined as follows. When the distance _S1L is changed, the beam size of the signal light L1 in the optical deflection element 15 in the y-axis direction changes (becomes smaller) and becomes larger than the change point distance (for example, about 450 mm or 180 mm described above). It is preferable to set as follows.

Further, each of the signal light L1 dispersed by the spectroscopic element 18 is independently phase-modulated by a plurality of light deflecting element elements arranged along the x-axis direction, such as LCOS, as the optical deflecting element 15. When the optical deflection element that deflects toward the output port 13 is used, the beam waist position adjusting optical system 20A preferably sets the aspect ratio of the beam size of the signal light L1 in the optical deflection element 15 to 30 or more. In order to realize this, the aspect ratio of the beam size of the signal light L1 in the optical deflection element 15 is set in the y-axis direction in the anamorphic optical system 17 (that is, in the x-axis direction in the optical deflection element 15). It is preferable that the magnification of the beam size of the signal light L1 is three times or more.

As described above, in this wavelength selective switch 1A, the beam waist position adjusting optical system 20A sets the beam waist position P1 of the signal light L1 input from the input port 12 in the x-axis direction and the y-axis direction, respectively. adjust. In particular, the beam waist position adjusting optical system 20A adjusts the beam waist position P1 so that the beam waist position P1 of the signal light L1 substantially coincides with the front focal point Pf of the condenser lens 19 in the x-axis direction. For this reason, the beam size of the signal light L1 at the output port 13 in the x-axis direction (the arrangement direction of the input port 12 and the output port 13) can be reduced. Therefore, according to this wavelength selective switch 1, it is possible to increase the number of ports without increasing the size of the apparatus.

In the wavelength selective switch 1A, the beam waist position P1 of the signal light L1 input from the input port 12 is set on the spectroscopic element 18 by the beam waist position adjusting optical system 20A (relay optical system 16A) in the x-axis direction. To be located. For this reason, the spectroscopic element 18 can be reduced in size in the x-axis direction.

On the other hand, the beam waist position adjusting optical system 20A adjusts the beam waist position P1 of the signal light L1 input from the input port 12 in the y-axis direction so as to be the latter stage of the anamorphic optical system 17 (that is, adjust the distance S _1P described above), as a result, to adjust the distance S _1L from the beam waist position P3 of the signal light L1 incident on the condenser lens 19 to the condenser lens 19. Thereby, the beam size of the signal light L1 in the y-axis direction in the optical deflection element 15 is adjusted, and the aspect ratio of the beam size of the signal light L1 in the optical deflection element 15 is adjusted. Thus, according to the wavelength selective switch 1A, the aspect ratio of the beam size of the signal light L1 in the optical deflector 15 can be set, for example, in the y-axis direction of the anamorphic optical system 17 without complicating the structure. The beam size enlargement magnification (that is, the beam size enlargement magnification in the x-axis direction of the light deflection element 15 via the condenser lens 19) or more can be adjusted.

The above first and second embodiments describe one aspect of the wavelength selective switch according to one aspect of the present invention. Therefore, the wavelength selective switch according to the present invention is not limited to the wavelength

selective switches

1 and 1A described above. The wavelength selective switch according to the present invention can be arbitrarily modified from the wavelength

selective switches

1 and 1A described above without departing from the scope of the claims.

For example, the wavelength selective switch 1 (wavelength selective switch 1A) described above can further include a polarization diversity module 30 as shown in FIG. The polarization diversity module 30 is disposed in front of the relay optical system 16 (relay optical system 16A). The polarization diversity module 30 includes a polarization beam splitter 31 that separates the signal light L1 in the y-axis direction according to the polarization direction (s / p polarization), and the signal light DL1 and DL2 separated by the polarization beam splitter 31. A wave plate (polarization rotating element) 32 that matches the polarization direction of one signal light DL2 with the polarization direction of the other signal light DL1, and one of the signal lights DL1 and DL2 separated by the polarization beam splitter 31. And an optical path adjusting element 33 that matches the optical path length of the other signal light DL2 with the optical path length. In the polarization diversity module 30, the signal light DL 2 separated by the polarization beam splitter 31 is reflected by the mirror 34 and then enters the wave plate 32. As described above, the wavelength selective switch 1 (wavelength selective switch 1A) includes the polarization diversity module 30 and can reduce the polarization dependent loss. In particular, the polarization diversity module 30 can be miniaturized by disposing it in front of the relay optical system 16 (relay optical system 16A).

Here, in the wavelength selective switch 1 (wavelength selective switch 1A) including such a polarization diversity module 30, the signal light DL1 and the signal light DL2 follow different paths. The paths through which the signal lights DL1 and DL2 pass are reversed in the forward path and the return path. For example, the signal light DL1 that travels toward the optical deflection element 15 through the upper path in the figure passes through the lower path in the figure when returning from the optical deflection element 15. At this time, in the wavelength selective switch 1 (wavelength selective switch 1A), the above-described functions of the relay optical system 16 (16A) and the anamorphic optical system 17 are important. Therefore, in the forward and return paths of the signal lights DL1 and DL2 It is necessary to align the optical path length. For this reason, for example, it is more effective to arrange the optical path adjusting element 33 constituted by a cylindrical lens or a prism assembly.

By the way, as shown in FIG. 3 and the above equation (2), the beam radius D _{2 at} the beam waist position A ₂ of the light L ₂ emitted from the lens A is equal to the beam waist position A ₁ of the light L ₂ incident on the lens A. it can also be adjusted by adjusting the beam radius D ₁ in. Therefore, also in the wavelength selective switch 1A described above, in the y-axis direction, for example, the beam waist position adjusting optical system 20A is used to adjust the beam size at the beam waist position P3 of the signal light L1 incident on the condenser lens 19. The aspect ratio of the beam size of the signal light L1 on the optical deflection element 15 may be adjusted by adjusting the beam size in the y-axis direction of the signal light L1 on the optical deflection element 15.

Further, in the wavelength selective switch 1A described above, the relay optical system 16A is set so that the beam waist position P1 of the signal light L1 input from the input port 12 in the y-axis direction is in front of the

collimating lenses

12b and 13b. It is good also as a mode to adjust. In that case, it is desirable that the second lens 16c of the relay optical system 16A be a cylindrical lens having optical power only in the x-axis direction. According to such a configuration, the distance _S1P has a positive value, but the same effect can be achieved as shown in the above formula.

In the above-described embodiment, an example is described in which the wavelength

selective switches

1 and 1A are applied when wavelength multiplexed light is input from the input port 12 and light of each wavelength component after spectroscopy is output from the output port 13. However, the wavelength

selective switches

1, 1 A may be applied when light of each wavelength component is input from the plurality of input ports 12 and wavelength-multiplexed light after being combined is output from the output port 13.

Furthermore, in the above-described embodiment, the

ports

12 and 13 of the port array 14 are configured to include the

optical fibers

12a and 13a and the

collimating lenses

12b and 13b. It is not limited.

DESCRIPTION OF

SYMBOLS

1,1A ... Wavelength selection switch, 12 ... Input port, 12a, 13a ... Optical fiber, 12b, 13b ... Collimating lens, 14 ... Port array, 16, 16A ... Relay optical system, 16a ... 1st lens (1st Element), 16b ... second lens (second element), 16c ... second lens (second element), 17 ... anamorphic optical system, 17a, 17b ... prism, 18 ... spectroscopic element, 19 ... Condensing lens (condensing element), 20A ... beam waist position adjusting optics, 30 ... polarization diversity module, 31 ... polarizing beam splitter, 32 ... wavelength plate (polarization rotating element), 33 ... optical path adjusting element.

Claims

A port array configured by arranging an input port for inputting signal light and an output port for outputting signal light in a first direction;
A spectroscopic element that splits the signal light input from the input port in a second direction different from the first direction;
A condensing element that condenses each of the signal lights dispersed by the spectroscopic element;
An optical deflecting element that deflects each of the signal lights condensed by the condensing element toward the output port;
A relay optical system that adjusts the beam waist position of the signal light input from the input port so as to substantially coincide with the front focal point of the light collecting element with respect to the first direction;
It is arranged at the front stage or the rear stage of the relay optical system so as to be optically connected to the relay optical system, and the signal light in the light deflection element is in the first direction with respect to the beam size in the second direction. An anamorphic optical system that expands the ratio of beam sizes,
A wavelength selective switch characterized by that.
The relay optical system includes a first element having optical power in the first direction and the second direction, and a second element having optical power in at least the first direction. The wavelength selective switch according to claim 1, wherein:
The input port and the output port include an optical fiber and a collimating lens optically connected to the optical fiber,
The front focal point of the first element is arranged to substantially coincide with the rear focal point of the collimating lens in the first direction;
The front focal point of the second element substantially coincides with the rear focal point of the first element in the first direction, and the rear focal point of the second element is the front focal point of the light collecting element. Are arranged so that they match,
The wavelength selective switch according to claim 2.
The second element has optical power only in the first direction, and the ratio of the beam size in the first direction to the beam size in the second direction of the signal light in the optical deflection element is The wavelength selective switch according to claim 3, wherein the wavelength selective switch is expanded.
The anamorphic optical system is disposed at a subsequent stage of the relay optical system,
The first element has a beam size at the beam waist position of the signal light emitted from the first element, rather than a beam size at the beam waist position of the signal light input from the input port and incident on the first element. Is relatively large,
The wavelength selective switch according to any one of claims 2 to 4, wherein:
The relay optical system and the anamorphic optical system constitute a beam waist position adjusting optical system that adjusts a beam waist position of the signal light,
The anamorphic optical system is disposed at a subsequent stage of the relay optical system,
The relay optical system adjusts the beam waist position of the signal light input from the input port in the second direction so as to be a subsequent stage of the anamorphic optical system.
The wavelength selective switch according to claim 3.
The wavelength selective switch according to claim 6, wherein the second element has optical power in the first direction and the second direction.
The relay optical system and the anamorphic optical system constitute a beam waist position adjusting optical system that adjusts a beam waist position of the signal light,
The anamorphic optical system is disposed at a subsequent stage of the relay optical system,
The said relay optical system adjusts the beam waist position of the signal beam | light input from the said input port so that it may become a front | former stage of the said collimating lens about the said 2nd direction. Wavelength selective switch.
The wavelength selective switch according to claim 8, wherein the second element has optical power only in the first direction.
The ratio of the beam size in the first direction to the beam size in the second direction of the signal light in the optical deflection element is the beam size of the signal light in the second direction in the anamorphic optical system. The wavelength selective switch according to any one of claims 6 to 9, characterized in that the magnification is 3 times or more of the magnification.
The distance between the beam waist position of the signal light input from the input port and incident on the light condensing element and the light condensing element are such that the beam size of the signal light in the light deflecting element is changed when the distance is changed. The wavelength selective switch according to any one of claims 6 to 9, wherein the wavelength selective switch is larger than a changing point distance to be changed.
The light deflecting element is directed to the output port by independently phase-modulating each of the signal lights dispersed by the spectroscopic element by a plurality of light deflecting element elements arranged along the first direction. And deflect
In the relay optical system and the anamorphic optical system, the ratio of the beam size in the first direction to the beam size in the second direction of the signal light in the optical deflection element is 30 or more.
The wavelength selective switch according to any one of claims 1 to 11, wherein:
The wavelength selective switch according to any one of claims 1 to 12, wherein the anamorphic optical system includes at least a pair of prisms.
The wavelength selective switch according to claim 13, wherein an incident angle of the signal light input from the input port to the prism is 70 ° or more.
The wavelength selective switch according to claim 13 or 14, wherein an incident angle of the signal light input from the input port to the prism is substantially equal to a Brewster angle.
The wavelength selective switch according to claim 14 or 15, wherein a refractive index of the prism is 1.5 or more.
The wavelength selective switch according to claim 16, wherein the refractive index of the prism is 3 or more.
The wavelength selective switch according to any one of claims 1 to 17, further comprising a polarization diversity module disposed in front of the relay optical system.
The polarization diversity module includes: a polarization beam splitter that separates signal light in the second direction according to a polarization direction; and one polarization direction of the signal light separated by the polarization beam splitter is converted to the other polarization direction. The wavelength rotation device according to claim 18, further comprising: a polarization rotation element that adjusts the optical path length of the signal light, and an optical path adjustment element that adjusts one optical path length of the signal light separated by the polarization beam splitter to the other optical path length. Select switch.