JP2011203572A - Four port optical switch - Google Patents

Abstract

PROBLEM TO BE SOLVED: To switch an optical path of four ports arbitrarily only by two optical switch elements.SOLUTION: By combining first and second 2×2 optical switches, the first port A1 of the first 2×2 optical switch is connected to the first port B1 of the second 2×2 optical switch, and the third port A3 of the first 2×2 optical switch is connected to the second port B2 of the second 2×2 optical switch. With the second and fourth ports A2 and A4 of the first 2×2 optical switch being the first and fourth input/output ports P1 and P4 respectively, and the third and fourth ports B3 and B4 of the second 2×2 optical switch being the second and third input/output ports P2 and P3 respectively, the optical path connection is made by the selection from among these four input/output ports P1-P4.

Description

  The present invention relates to a four-port optical switch that arbitrarily switches an optical path of four ports with only two optical switch elements.

  An optical switch using a planar optical circuit has two inputs and two outputs. FIG. 4 shows the configuration of a conventional 2 × 2 optical switch. (a) is a type in which a phase modulator is provided in the optical multiplexer / demultiplexer and the connection port is switched, and (b) is a type in which a phase modulator is provided in the Mach-Zehnder optical interferometer and the connection port is switched by the interference effect. (C) is a type in which a reflection mirror is provided in the intersecting optical waveguide and the connection port is switched by changing the reflectance. In each figure, the black thick line represents the optical waveguide. In all these optical switches, there is only a two-state switching between port 1 ポ ー ト 4 and port 2⇔3, or port 1⇔3 and port 2⇔4. Port 1⇔2 and port 3⇔4 Connection is impossible.

  If there is a 4-port optical switch that can switch between these three states, the number of switching paths in a multi-stage matrix switch doubles, and it is suitable as an optical switch for constructing a mesh optical network in the future. As a method for realizing this 4-port optical switch, as shown in FIG. 5, a configuration in which four to five optical switch elements are combined is disclosed in Patent Document 1 “Waveguide type optical switch” and Patent Document 2 “4-port optical switch”. It is disclosed.

The waveguide type optical switch described in Patent Document 1 shown in FIG. 5 (a) is a combination of five optical switch elements, and between any four ports (A1, B3, D2, E4), the following states 1 to 3 connections are possible.
State 1: Connection of port A1⇔A3⇔B1⇔B3 and port D2⇔D4⇔E2⇔E4,
State 2: Connection between port A1⇔A4⇔C2⇔C4⇔D3⇔D2 and port B3⇔B2⇔C1⇔C3⇔E1⇔E4,
State 3: Connection between port A1⇔A4⇔C2⇔C3⇔E1⇔E4 and port B3⇔B2⇔C1⇔C4⇔D3⇔D2.

The 4-port optical switch described in Patent Document 2 shown in FIG. 5B is a combination of four optical switch elements between any four ports (A2, B2, B4, C4) and in the following states 1 to 3. Enable connection.
State 1: Port A2⇔A3⇔D2⇔D4⇔C1⇔C4 and port B2⇔B4 connection,
State 2: Connection between port A2⇔A4⇔B1⇔B4 and port B2⇔B3⇔C2⇔C4,
State 3: Connection of ports A2⇔A3⇔D2⇔D3⇔C3⇔C2⇔B3⇔B2 and ports C4⇔C1⇔D4⇔D1⇔A1⇔A4⇔B1⇔B4.

  As shown in FIGS. 5 (a) and 5 (b), the configuration of the proposed 4-port optical switch requires 4 to 5 optical switch elements. The problem is an increase in signal crosstalk to the unused ports.

Japanese Patent Laid-Open No. 9-218430 Japanese Patent No.2766531

  An object of the present invention is to solve the problems of the four-port optical switches that have been proposed so far, and to realize a four-port optical switch that arbitrarily switches the optical path of four ports with only two optical switch elements. Yes. Thereby, it is possible to reduce optical loss in each element and signal crosstalk to an unintended port.

  The four-port optical switch of the present invention includes a first 2 × 2 optical switch having first to fourth ports A1, A2, A3, and A4, and first to fourth ports B1, B2, B3, and B4. Combine with a second 2x2 optical switch. The first port A1 of the first 2 × 2 optical switch is connected to the first port B1 of the second 2 × 2 optical switch, and the third port A3 of the first 2 × 2 optical switch is connected. And the second port B2 of the second 2 × 2 optical switch. The second and fourth ports A2 and A4 of the first 2 × 2 optical switch are designated as first and fourth input / output ports P1 and P4, respectively, and the third and fourth ports of the second 2 × 2 optical switch are used. Ports B3 and B4 are designated as second and third input / output ports P2 and P3, respectively, and these four input / output ports P1 to P4 are selected and optically connected.

  The first and second 2 × 2 optical switches have a connection 1⇔4 between the first and fourth ports, a connection 2⇔3 between the second and third ports, and the first and third, respectively. Only two states of connection 1⇔3 between these ports and connection 2⇔4 between the second and fourth ports are possible. The optical path connection between I / O ports P1, P2, P3, P4 is the first connection state of port P1⇔A2⇔A3⇔B2⇔B3⇔P2 and port P3⇔B4⇔B1⇔A1⇔A4⇔P4, port Second connection status of P1⇔A2⇔A3⇔B2⇔B4 ポ ー ト P3 and port P2⇔B3⇔B1⇔A1⇔A4 接 続 P4, port P1⇔A2⇔A4⇔P4 and P2⇔B3⇔B1⇔A1⇔A3⇔ It has three states of the third connection state of B2⇔B4⇔P3.

  In the proposals so far, four to five optical switch elements are required. However, according to the present invention, since the optical switch element can be configured with two optical switch elements, the number of elements is greatly reduced. As a result, advantages such as downsizing of the entire device, low power consumption, low loss, and low crosstalk characteristics can be obtained.

It is a figure which illustrates the 4 port optical switch comprised based on this invention. It is an optical microscope photograph of the sample which produced the optical switch of this invention as an experiment using a silicon optical waveguide. It is an infrared light observation image of the sample end faces of P2, P3, and P4 when an optical signal is incident on P1 and the state of each switch element is switched. It is a diagram illustrating a conventional 2 × 2 optical switch, (a) a type in which a phase modulator is provided in an optical multiplexer / demultiplexer and a connection port is switched, and (b) a phase modulator is provided in a Mach-Zehnder optical interferometer, A type in which the connection port is switched by the interference effect, and a type (c) in which the reflection port is provided in the crossed optical waveguide and the connection port is switched by changing the reflectance are shown. It is a figure which shows the prior art structure described in patent document 1 and patent document 2, respectively.

  Hereinafter, the present invention will be described based on examples. FIG. 1 is a diagram illustrating a four-port optical switch configured according to the present invention. As shown in FIG. 1, the exemplary 4-port optical switch can arbitrarily switch the optical path of four ports with only two optical switch elements. As each switch element itself, a conventional 2 × 2 optical switch as illustrated in FIGS. 4A to 4C can be used. The connection between ports 1 and 4 and ports 2 and 3 and port 1 3. There are only two connection states, port 2 and port 4, and port 1 and port 2 and port 3 and port 4 cannot be connected. Here, if an optical path connecting ports A1 and B1 and ports A3 and B2 of two 2 × 2 optical switches is formed, any connection between the four ports of input / output ports P1, P2, P3, and P4 is possible. Become. Specifically, port P1⇔A2⇔A3⇔B2⇔B3⇔P2 and port P3⇔B4⇔B1⇔A1⇔A4⇔P4 connection status 1, port P1⇔A2⇔A3⇔B2⇔B4⇔P3 and port P2 There are three states: connection state 2 for B3, B1, A1, A4, and P4, and connection state 3 for ports P1, A2, A4, and P2, and P2, B3, B1, B1, A1, A3, B2, B4, and P3.

  FIG. 2 is an optical micrograph of a sample in which the optical switch of the present invention was prototyped using a silicon optical waveguide. The dark line is the optical waveguide. Inside the switch element, a metal heater and an electrode utilizing a thermo-optic effect are provided. As the 2 × 2 optical switch element, a Mach-Zehnder interference type optical switch using the thermo-optic effect was adopted (conventional optical switch in FIG. 4B). Ports P1 to P4 correspond to the ports in FIG.

  FIG. 3 is an infrared observation image of the sample end faces of P2, P3, and P4 when an optical signal is incident on P1 and the state of each switch element is switched. An infrared observation image near the end face on the right side of the sample when signal light is incident from port P1 on the left side of the prototype sample. The black line part on the left is the optical waveguide of ports P2, P3, and P4, and the part that appears white on the end face indicates the emission of signal light. (a), (b), (c) are observation images of the emitted light when the states of the two optical switch elements are switched, and it can be seen that the three-state switching of the present invention can be realized.

  With the increase in the amount of network information in recent years, electrical signal processing in IP routers has become a bottleneck for increasing capacity and reducing power consumption. An optical switch is an indispensable device for replacing electric signal processing with optical signal processing in optical communication. The present invention is used in communication equipment for optical signal processing using an optical switch.

Claims (3)

First 2 × 2 optical switch having first to fourth ports A1, A2, A3, A4, and second 2 × 2 optical switch having first to fourth ports B1, B2, B3, B4 Combine
The first port A1 of the first 2 × 2 optical switch is connected to the first port B1 of the second 2 × 2 optical switch, and the third port A3 of the first 2 × 2 optical switch is connected. And the second port B2 of the second 2 × 2 optical switch,
The second and fourth ports A2 and A4 of the first 2 × 2 optical switch are designated as first and fourth input / output ports P1 and P4, respectively, and the third and fourth ports of the second 2 × 2 optical switch are used. A 4-port optical switch in which the ports B3 and B4 are set as second and third input / output ports P2 and P3, respectively, and these four input / output ports P1 to P4 are selected and optically connected.   The first and second 2 × 2 optical switches have a connection 1⇔4 between the first and fourth ports, a connection 2⇔3 between the second and third ports, and the first and third, respectively. 2. The four-port optical switch according to claim 1, wherein only two states of connection 1 接 続 3 between the ports and connection 2 接 続 4 between the second and fourth ports are possible.   The optical path connection between I / O ports P1, P2, P3, P4 is the first connection state of port P1⇔A2⇔A3⇔B2⇔B3⇔P2 and port P3⇔B4⇔B1⇔A1⇔A4⇔P4, port Second connection status of P1⇔A2⇔A3⇔B2⇔B4 ポ ー ト P3 and port P2⇔B3⇔B1⇔A1⇔A4 接 続 P4, port P1⇔A2⇔A4⇔P4 and P2⇔B3⇔B1⇔A1⇔A3⇔ The four-port optical switch according to claim 2, having three states of a third connection state of B2⇔B4⇔P3.