JP4803746B2 - Waveguide type optical switch - Google Patents

Description

  The present invention relates to a waveguide-type optical switch used in optical communication or the like, and particularly, an optical switch configured by cascading unit optical switch elements having 1 or 2 inputs / outputs, and the influence of manufacturing errors is small. The present invention also relates to a technique for realizing a circuit configuration with few waveguide intersections.

  Optical communication technology using an optical fiber as a transmission medium has led to an increase in signal transmission distance, and a large-scale optical communication network has been constructed. In recent years, with the widespread use of Internet communication, communication traffic has increased rapidly, and demands for large capacity, high speed, and high functionality for communication networks are increasing. Up to now, it has become possible to increase the transmission capacity between two points by introducing a wavelength multiplexing communication technique for simultaneously transmitting a plurality of optical signals having different wavelengths through one transmission line.

  However, in a communication network, it is necessary to set (route) a signal path or switch (switch) a signal path at a node where a plurality of transmission paths are gathered. Is becoming a bottleneck. Up to now, a method has been used in which a transmitted optical signal is once converted into an electrical signal, route setting and switching are performed, and the electrical signal is converted again into an optical signal and sent to the transmission path. It is expected that the throughput of a node can be drastically increased by using a method for setting and switching a signal path without converting an optical signal into an electrical signal. An optical switch is an indispensable component for introducing such a system into an optical communication network.

  As a specific method for realizing the optical switch, there are a system that mechanically moves an optical fiber, a system that uses a movable mechanism such as a minute mirror, and a system that uses a change in the refractive index of an optical waveguide.

  This method using the change in refractive index of the optical waveguide is superior in mass productivity and durability because of the use of the optical waveguide. There is an advantage that it can be integrated on top. Therefore, it is suitable for configuring a large-scale optical switch.

  A waveguide type optical switch is connected to a plurality of unit optical switch elements having 1 or 2 inputs / outputs, so that one input × multiple outputs (or multiple inputs × 1 output), multiple inputs × multiple outputs, two inputs × 2 Optical switches having various circuit configurations can be manufactured with respect to the number of input / output terminals and the connection pattern between terminals, such as those with multiple outputs. Among them, an optical switch of 1 input × multiple output (or multiple input × 1 output) is widely used as an optical switch that selects and connects one of a plurality of output ports (or input ports). The configuration of the 1-input × multi-output optical switch includes a tree configuration in which 1-input 2-output unit optical switch elements are connected in a tree shape, and a tap configuration in which 1-input 2-output unit optical switch elements are connected in cascade. .

  FIG. 6 shows an example of a 1 × 4 optical switch having a tap configuration. As shown in FIG. 6, the 1 × 4 optical switch of the tap configuration has a configuration in which four unit input / output unit optical switch elements 611, 612, 613, and 614 are integrated on a single substrate. ing.

  The unit optical switch elements 611, 612, 613, and 614 are arranged substantially in a straight line with respect to the traveling direction of the signal light (the direction indicated by the arrow in FIG. 6), and are connected in cascade. More specifically, the unit optical switch elements 611, 612, and 613 are unit optical switch elements 612, 613, and 614 in which one output port (on the left side in the drawing with respect to the traveling direction of the signal light in FIG. 6) is arranged in the subsequent stage. Are connected to each input port.

  When the unit optical switch element has an asymmetric structure and is connected to one output port when the drive signal is off, and connected to the other output port when the drive signal is on, the unit optical switch element is The cascaded tap configuration has the advantage that the number of optical switch elements to be driven is only one regardless of the scale of the optical switch, so that the control is simple and the drive power is small ( For example, refer nonpatent literature 1).

  In order to obtain a high extinction ratio, a 1 × N optical switch having a tap configuration can connect a gate switch element with one input and one output to each output port. Since this gate switch element can also function as a variable optical attenuator by controlling the driving power in an analog manner, the power level of the output light can be adjusted (for example, see Non-Patent Document 2). .

  FIG. 7 shows an example of a 1 × 4 optical switch to which a gate switch element is connected. As shown in FIG. 7, the 1 × 4 optical switch includes four 1-input 2-output unit optical switch elements 711, 712, 713, 714 and four 1-input 1-output gates on a single substrate. The switch elements 731, 732, 733, and 734 are integrated.

  The unit optical switch elements 711, 712, 713, and 714 are arranged substantially in a straight line with respect to the traveling direction of the signal light (the direction indicated by the arrow in the figure) and are connected in cascade. More specifically, the unit optical switch elements 711, 712, and 713 are unit optical switch elements 712, 713, and 714 in which one output port (on the left side in the drawing with respect to the traveling direction of the signal light in FIG. 7) is arranged in the subsequent stage. Are connected to each input port.

  Note that the other output port of the unit optical switch elements 711, 712, 713, and 714 (in FIG. 7, on the right side of the drawing with respect to the signal traveling direction) is an input port of the unit optical switch elements 731, 732, 733, and 734. The output ports of the unit optical switch elements 731, 732, 733, and 734 extend to the output end as output terminals of the 1 × 4 optical switch.

Kominato, 6 others, “C-3-141 Tree-tap composite quartz 1x16 thermo-optic switch”, 1999 IEICE General Conference, 1999, p.295 Okuno and 6 others "C-3-116 High extinction ratio 8 series 1x8 PLC switch and its application", 2002 IEICE Electronics Society Conference, 2002, p.216

  However, in the waveguide type optical switch shown in FIGS. 6 and 7, the plurality of output optical waveguides are unevenly distributed on one side with respect to the arrangement of the unit optical switch elements connected in a column, and the density of the waveguide pattern is low. Due to the non-uniformity in the plane, there is a problem that the influence of the unit optical switch element from the surroundings is not symmetric when the waveguide is manufactured, and a manufacturing error tends to occur in the characteristics of the optical switch.

  In the 1 × 4 optical switch shown in FIG. 7, when the gate switch elements 731, 732, 733, and 734 are replaced with unit optical switch elements with two inputs and one output, a waveguide type optical switch as shown in FIG. 8 is obtained. Here, among the input ports of the unit optical switch elements 821, 822, 823, and 824 each having two inputs and one output, the unit optical switch elements 811, 812, 813, and 814 are connected in cascade. The other port is used as an input terminal, and the input port of the first unit optical switch element 811 in the group of optical switch elements connected in cascade is used as another input terminal (hereinafter referred to as a redundant input terminal). By using the output ports of the output optical switch elements 821, 822, 823, and 824 as output terminals, a 4 + 1 input 4 output waveguide type optical switch can be configured (hereinafter, such an optical switch is referred to as “4 + 1”). : 4 optical switch ").

  This 4 + 1: 4 optical switch normally outputs the signal light input to each input terminal to the corresponding output terminal. However, by switching the optical switch element, the signal light input to the redundant input terminal It can be output from any one of the output terminals. However, in such a waveguide type optical switch, in order to draw out the input terminal and the output terminal to the end face of the waveguide chip, crossing of the waveguide is inevitable. In the case of an N + 1: N optical switch, N-1 intersections per port are generated at ports where waveguide crossings occur. Therefore, when N is large (for example, N = 8), N + 1: It has been considered that it is not practical to configure the N optical switch with a waveguide type optical switch.

  The present invention solves such problems, and provides a waveguide type optical switch capable of reducing the influence of manufacturing errors and capable of manufacturing a high-performance optical switch with a high yield. With the goal.

  As a result of examining the circuit configuration of a conventional waveguide-type optical switch in order to solve the above-mentioned problems, the present inventors have determined the output waveguides (or input waveguides) of a plurality of unit optical switch elements connected in cascade. In-plane uniformity of the waveguide pattern density by alternately arranging on both sides (for example, left and right with respect to the traveling direction of the signal light) across the optical switch element group composed of the plurality of unit optical switch elements I got the idea that it can be improved.

  Furthermore, in a waveguide type optical switch configured by connecting unit optical switch elements with two inputs and one output in cascade, an N: N + 1 optical switch is obtained by connecting a unit input switch element with one input and two outputs to each input port. When configured, the input waveguides of the plurality of unit optical switch elements connected in cascade are arranged on both sides (for example, with respect to the traveling direction of the signal light) with the optical switch element group composed of the plurality of unit optical switch elements interposed therebetween. By alternately arranging them on the left and right), it was found that the number of waveguide intersections can be reduced, and the present invention has been completed.

  That is, in the waveguide type optical switch according to the first invention for solving the above-mentioned problems, N unit optical switch elements each having one input and two outputs are connected in series (where N is an integer of 3 or more). Of the two output ports of the (i-1) th unit optical switch element (where i is an integer of 2 ≦ i ≦ N−1), One output port is connected to the input port of the i-th unit optical switch element, and one output port of the two output ports of the i-th unit optical switch element is the (i + 1) th unit optical switch element And the other output port of the (i-1) -th unit optical switch element and the other output port of the i-th unit optical switch element are connected in series. Optical switch element Characterized in that arranged in opposite positions across the Ranaru unit optical switch module.

  A waveguide type optical switch according to a second aspect of the present invention is a waveguide type optical switch configured by connecting N unit optical switch elements having two inputs and one output in series (where N is an integer of 3 or more). In the switch, one of the two input ports of the i-th unit optical switch element (where i is an integer satisfying 2 ≦ i ≦ N−1) is defined as the (i−1) -th unit. Connecting to the output port of the optical switch element, and connecting one input port of the two input ports of the (i + 1) th unit optical switch element to the output port of the i th unit optical switch element; A unit optical switch element group composed of the unit optical switch elements connected in a column with the other input port of the i-th unit optical switch element and the other input port of the (i + 1) th unit optical switch element. Pinch Characterized in that arranged in opposite positions.

  That is, the waveguide type optical switch according to the second invention corresponds to a configuration in which the input terminal and the output terminal are interchanged in the waveguide type optical switch according to the first invention.

  A waveguide type optical switch according to a third aspect is the waveguide type optical switch according to the first aspect, wherein the second unit optical switch element of the two output ports of the first unit optical switch element is used. A rear stage of an output port different from the connected output port, a rear stage of the other output port of the two output ports of the i-th unit optical switch element, and a rear stage of the N-th unit optical switch, A unit optical switch element having one input and one output is connected.

  A waveguide type optical switch according to a fourth aspect of the present invention is the waveguide type optical switch according to the second aspect of the present invention, wherein the input port of the first unit optical switch element and the i th unit optical switch element Of the two input ports, the preceding stage of the other input port and the input port connected to the (N−1) th unit optical switch element of the two input ports of the Nth unit optical switch element A unit optical switch element having one input and one output is connected to the preceding stage of different input ports.

  That is, the waveguide type optical switch according to the fourth invention corresponds to a configuration in which the input terminal and the output terminal are interchanged in the waveguide type optical switch according to the third invention.

  A waveguide type optical switch according to a fifth aspect is the waveguide type optical switch according to the first aspect, wherein the second unit optical switch element is one of the two output ports of the first unit optical switch element. A rear stage of an output port different from the connected output port, a rear stage of the other output port of the two output ports of the i-th unit optical switch element, and a rear stage of the N-th unit optical switch, A unit optical switch element having two inputs and one output is connected.

  A waveguide type optical switch according to a sixth aspect of the invention is the waveguide type optical switch according to the second aspect of the invention, wherein the first stage of the input port of the unit optical switch element and the i th unit optical switch element are Of the two input ports, the preceding stage of the other input port and the input port connected to the (N−1) th unit optical switch element of the two input ports of the Nth unit optical switch element A unit optical switch element having one input and two outputs is connected to the preceding stage of different input ports.

  That is, the waveguide type optical switch according to the sixth aspect of the invention corresponds to the configuration of the waveguide type optical switch according to the fifth aspect of the invention, in which the input terminal and the output terminal are interchanged.

  According to the present invention, in a 1-input × multi-output waveguide type optical switch configured by cascading 1-input 2-output unit optical switch elements, and 2-input 1-output unit optical switch elements are cascade-connected. In the multi-input × 1-output waveguide type optical switch configured as described above, the in-plane uniformity of the waveguide pattern density can be improved. Therefore, the influence of manufacturing errors can be reduced, and high-performance optical switches can be manufactured with a high yield.

  Further, according to the present invention, N + 1: N light is configured by connecting N 1-input 2-output unit optical switch elements in cascade, and connecting 2-input × 1-output unit optical switch elements at the subsequent stage of each output port. N-input N + 1-output optical switch configured by connecting N switches or two-input single-output unit optical switch elements in cascade, and connecting a single-input × 2-output unit optical switch element in front of each input port ( (Hereinafter referred to as N: N + 1 optical switch), the number of waveguide intersections is (N-1) / 2 or less when N is an odd number per port, and (N / 2) -1 when N is an even number. Thus, an optical switch with a small insertion loss can be realized.

  Hereinafter, embodiments of the present invention will be described. As a system of the waveguide type optical switch for implementing the optical switch according to the present invention, there are a system using a thermo-optic effect, a system using an electro-optic effect, a system using a refractive index change by current injection, and the like. Further, for example, in a method using the thermo-optic effect, there are quartz glass, organic polymer, silicon, and the like as materials used. Among them, optical switches using the thermo-optic effect of silica-based optical waveguides have good compatibility with optical fibers, low insertion loss, low principle of polarization dependence, and physical components. Therefore, it is most practical and suitable for practicing the present invention.

[First embodiment]
A first embodiment of the present invention will be described with reference to FIG. This embodiment corresponds to claim 1 of the present invention, and is an example in which a 1 × 4 optical switch with N = 4 is configured. As shown in FIG. 1, four 1-input 2-output unit optical switch elements 111, 112, 113, 114 are connected in cascade, and an output port 4 from each unit optical switch element 111, 112, 113, 114 is connected. In other words, the book is placed on both sides alternately with respect to the optical switch group composed of the unit optical switch elements 111, 112, 113, 114 at the output end of the 1 × 4 optical switch. It extends so as to face each other. Thereby, at the output end of the 1 × 4 optical switch, two output waveguides are arranged on both sides of the optical switch group.

Hereinafter, the input port of each of the unit optical switch elements 111 to 114 is the input port a, and the traveling direction of the signal light in FIG. 1 (the direction indicated by the arrow in the figure) among the two output ports of each of the unit optical switch elements 111 to 114 output ports b ₁ to the paper on the left side of the output port with respect to), describing the paper on the right side of the output port as an output port b ₂ to the traveling direction in FIG signal light.

First, in the first unit optical switch element 111, the input port a is the input terminal of the 1 × 4 optical switch, and one of the two output ports, the output port b ₁ is the second unit optical switch element. The other output port b ₂ connected to the input port a 112 is the output terminal of the 1 × 4 optical switch.

Further, the second unit optical switch element 112, while the output port b ₂ of one of the two output ports are connected to the input port a of the third unit optical switch element 113, the other output ports b ₁ Is the output terminal of the 1 × 4 optical switch.

In the third unit optical switch element 113, one output port b _{1 of the} two output ports is connected to the input port a of the fourth unit optical switch element 114, while the other output terminal b ₂ is connected. This is the output terminal of the 1 × 4 optical switch.

Further, 4-th unit optical switch element 114, the output port b ₁ of the two output ports is an output terminal of the 1 × 4 optical switch.

  According to the waveguide type optical switch according to this embodiment, the output waveguide is distributed almost uniformly without being unevenly distributed on one side with respect to the optical switch group composed of the unit optical switch elements 111, 112, 113, and 114. Therefore, in-plane uniformity of the waveguide pattern density can be obtained, the influence of manufacturing errors can be reduced, and high-performance optical switches can be manufactured with a high yield.

[Second Embodiment]
A second embodiment of the present invention will be described with reference to FIG. This embodiment corresponds to claim 2 of the present invention, and is an example in which a 4 × 1 optical switch with N = 4 is configured. As shown in FIG. 2, four 2-input 1-output unit optical switch elements 221, 222, 223, and 224 are connected in cascade, and four input ports to each optical switch element 221, 222, 223, and 224 are connected. However, at the input end of the 4 × 1 optical switch, the optical switch groups 221, 222, 223, and 224 connected in cascade extend so as to be alternately arranged on both sides. Thus, two input waveguides are arranged on both sides of the optical switch group at the input end of the waveguide type optical switch.

Hereinafter, the input ports a ₁ to the paper on the left side of the input ports for the two out Figure 2 in the traveling direction of the signal light input port (the direction indicated by the arrow) of each of the unit optical switch elements 221 to 224, FIG. 2, the input port a ₂ is the input port on the right side of the drawing with respect to the traveling direction of the signal light, and the output ports of the unit optical switch elements 221 to 224 are the output ports b.

First, in the first unit optical switch element 221, one input port a _{2 of the two} input ports is an input terminal of the 4 × 1 optical switch.

Further, the second unit optical switch element 222, while the input port a ₂ of one of the two input ports is connected to the output port b of the first unit optical switching element 221, the other input port a ₁ Are the input terminals of the 4 × 1 optical switch.

In the third unit optical switch element 223, one input port a ₁ of the two input ports is connected to the output port b of the second unit optical switch element 222, while the other input port a ₂ is connected. This is the input terminal of the 4 × 1 optical switch.

In the fourth unit optical switch element 224, one input port a _{2 of the two} input ports is connected to the output port b of the third unit optical switch element 223, while the other input port a ₁ is This is the input terminal for the 4 × 1 optical switch. The output port b of the unit optical switch element 224 is an output terminal of the 4 × 1 optical switch.

  According to this embodiment, the input waveguide is not unevenly distributed on one side at the input end of the 4 × 1 optical switch, and is substantially uniform with respect to the arrangement of the unit optical switch elements 221, 222, 223, and 224 connected in cascade. Therefore, the in-plane uniformity of the waveguide pattern density can be obtained, the influence of manufacturing errors can be reduced, and a high-performance optical switch can be manufactured with a high yield.

[Third embodiment]
A third embodiment of the present invention will be described with reference to FIG. This embodiment corresponds to claim 3 of the present invention, and is an example in which a 1 × 4 optical switch with N = 4 is configured. Note that, in this embodiment, when the input terminal and the output terminal are interchanged, a form corresponding to claim 4 of the present invention is obtained.

  As shown in FIG. 3, four 1-input 2-output unit optical switch elements 311, 312, 313, 314 are connected in cascade, and four output ports from each of the optical switch elements 311, 312, 313, 314 are With respect to an optical switch group consisting of optical switch elements 311, 312, 313, and 314 connected in cascade at the output end of the 1 × 4 optical switch via 1-input 1-output gate switch elements 331, 332, 333, and 334 It extends so as to be alternately arranged on both sides. As a result, two output waveguides are arranged on both sides of the optical switch group at the output end of the waveguide type optical switch.

Hereinafter, the input port of each of the unit optical switch elements 311 to 314 and the unit optical switch elements 331 to 334 is the input port a, and the progress of the signal light in FIG. The output port b ₁ is the output port on the left side of the drawing with respect to the direction (direction indicated by the arrow in the figure), and the output port b ₂ is the output port on the right side of the drawing with respect to the traveling direction of the signal light in FIG. The output port of the optical switch elements 331 to 334 will be described as an output port b.

First, in the first unit optical switch element 311, one output port b ₁ of the two output ports is connected to the input port a of the second unit optical switch element 312, while the other output port b ₂ is connected. It is connected to the input port a of the gate switch element 331 provided in the subsequent stage. The output port b of the gate switch element 331 is an output terminal of the waveguide type optical switch.

In the second unit optical switch element 312, one output port b _{2 of the two} output ports is connected to the input port a of the third unit optical switch element 313, while the other output port b ₁ is in the subsequent stage. The gate switch element 332 provided is connected to the input port a. The output port b of the gate switch element 332 is an output terminal of the waveguide type optical switch.

In the third unit optical switch element 313, one output port b _{1 of the} two output ports is connected to the input port a of the fourth unit optical switch element 314, while the other output port b ₂ is in the subsequent stage. The gate switch element 333 provided is connected to the input port a. The output port b of the gate switch element 333 is an output terminal of the waveguide type optical switch.

The fourth unit optical switch element 314 is a gate switch element in which one output port b _{2 of the two} output ports is an output terminal of the waveguide type optical switch, while the other output port b ₁ is provided in the subsequent stage. 334 to the input port a. The output port b of the gate switch element 334 is an output terminal of the waveguide type optical switch.

  According to the present embodiment, as in the first embodiment, the output waveguide is not unevenly distributed on one side of the waveguide type optical switch, and the arrangement of the unit optical switch elements 311, 312, 313, and 314 connected in series is not limited. Since the distribution is almost uniform, in-plane uniformity of the waveguide pattern density can be obtained, the influence of manufacturing errors can be reduced, and high-performance optical switches can be manufactured with high yield.

[Fourth embodiment]
A fourth embodiment of the present invention will be described with reference to FIG. This embodiment corresponds to claim 6 of the present invention and is an example in which a 4: 4 + 1 optical switch with N = 4 is configured. In the present embodiment, when the input terminal and the output terminal are interchanged, a form corresponding to claim 5 of the present invention is obtained.

  As shown in FIG. 4, four 2-input 1-output unit optical switch elements 421, 422, 423, and 424 are connected in cascade. The four input ports of each of the optical switch elements 421, 422, 423, and 424 are connected to the 4: 4 + 1 optical switch via the one-input and two-output optical switch elements 411, 412, 413, and 414 arranged in the preceding stage. At the input end, the optical switch elements 421, 422, 423, and 424 connected in cascade extend so as to be alternately arranged on both sides of the optical switch group. That is, the optical switch of the present embodiment uses the input ports of the unit optical switch elements 411, 412, 413, and 414 having 1 input and 2 outputs as input terminals.

  Of the two output ports of each of the 1-input 2-output optical switch elements 411, 412, 413, 414, the one not connected to the subsequent 2-input 1-output unit optical switch elements 422, 423, 424 The output port is used as an output terminal, and the output port of the unit optical switch element 424 located in the final stage of the two-input single-output optical switch element group connected in cascade is used as a redundant output terminal. Thereby, two waveguides are arranged on both sides of the optical switch group at the input end of the waveguide type optical switch, and the waveguide is provided on both sides of the optical switch group in addition to the center of the optical switch group at the output end. It is in a state where two are arranged.

Hereinafter, the input port of each of the unit optical switch elements 411 to 414 is the input port a, and of the two output ports of each of the unit optical switch elements 411 to 414, the traveling direction of the signal light in FIG. 4), the output port on the left side of the drawing sheet is the output port b ₁ , and the output port on the right side of the drawing sheet in FIG. 4 is the output port b ₂ . Of the two input ports, the input port a ₁ is the input port on the left side in FIG. 4 with respect to the traveling direction of the signal light, and the input port a ₁ is the input port on the right side in FIG. ₂ and the output port of each unit optical switch element 221-224 is demonstrated as the output port b.

First, the first two-input one-output unit optical switch element 421 has one input port a ₂ out of two input ports, and one of the two output ports of the unit optical switch element 411 with one input and two outputs. It is connected to port b ₁ . Other output port b ₂ of the unit optical switch element 411, the 4: is an output terminal of the 4 + 1 optical switch.

The second 2-input 1-output unit optical switch element 422 has one input port a ₂ connected to the output port b of the first 2-input 1-output unit optical switch element 421, and the other input port a _2. The input port a ₁ is connected to one output port b ₂ of the two output ports of the unit optical switch element 412 having one input and two outputs. One output port b ₁ of the two output ports of the 1-input 2-output unit optical switch element 412 is an output terminal of the 4: 4 + 1 optical switch.

The third 2-input 1-output unit optical switch element 423 has one input port a ₁ connected to the output port b of the second 2-input 1-output unit optical switch element 422, and the other input port a _1. The input port a ₂ is connected to _one output port b ₁ of the unit optical switch element 413 having one input and two outputs. The other output port b ₂ of the unit optical switch element 413 having one input and two outputs is an output terminal of the 4: 4 + 1 optical switch.

The fourth two-input one-output unit optical switch element 424 has one input port a ₂ connected to the output port b of the third two-input one-output unit optical switch element 423, while the other two input ports. The input port a ₁ is connected to the output port b ₂ of the unit optical switch element 414 having one input and two outputs, and the output port b of the unit optical switch element 424 extends to the emission end as a redundant output terminal. 1 Input 2 Output unit optical switch element 414, the output port b ₁ of one of the two output ports, the 4: is an output terminal of the 4 + 1 optical switch.

  According to this embodiment, the input waveguide and the output waveguide are not unevenly distributed on one side of the waveguide type optical switch, and the arrangement of the unit optical switch elements 421, 422, 423, and 424 connected in cascade is connected in cascade. Therefore, in-plane uniformity of the waveguide pattern density can be obtained, the influence of fabrication errors can be reduced, and high-performance optical switches can be fabricated with a high yield. Become. Furthermore, the number of waveguide intersections can be reduced as compared with the conventional one, and an optical switch with a small insertion loss can be realized.

  As described above in the first to fourth embodiments, in the optical switch configured by cascading unit optical switch elements having 1 or 2 inputs / outputs, the unit optical switch elements connected in tandem By arranging the output waveguide (or input waveguide) alternately on both sides of the optical switch element group so as to sandwich the optical switch element group at the output end (or input end) of the waveguide type optical switch, In-plane uniformity of pattern density can be improved.

  Further, N + 1: N optical switches can be obtained by connecting 2-input 1-output unit optical switch elements to each output port with respect to a waveguide-type optical switch configured by connecting 1-input 2-output unit optical switch elements in cascade. Or by connecting a single-input 2-output unit optical switch element to each input port to a waveguide-type optical switch configured by connecting unit optical switch elements of 2-input 1-output in cascade. In the case of configuring an N: N + 1 optical switch, the input waveguides of unit optical switch elements connected in cascade are alternately arranged on both sides of the optical switch element group so as to sandwich the optical switch element group, thereby providing a waveguide. The number of intersections can be reduced.

  The first embodiment of the present invention will be described in detail with reference to FIG. FIG. 5A is a top view illustrating a configuration example of the optical switch element according to the present embodiment, and FIG. 5B is a cross-sectional view taken along the line AA in FIG. In this example, a 1 × N optical switch, which is a waveguide type optical switch based on a circuit configuration corresponding to the third aspect of the present invention, is manufactured by an optical circuit described below.

As shown in FIG. 5, a cladding layer 2 formed of silica glass on a silicon substrate 1 having a thickness of 1 mm and a diameter of 6 inches (about 15.2 cm), and a buried core portion 31 embedded in the cladding layer 2. , 32 is produced by a combination of a deposition technique of a silica glass film using a flame hydrolysis reaction of a source gas such as SiCl ₄ or GeCl ₄ and a reactive ion etching technique, and a thin film heater 41 , 42 and a power supply electrode (not shown) were respectively formed on the surface of the cladding layer 2 by vacuum deposition and patterning. The core size of the manufactured optical waveguide was 7 μm × 7 μm, and the relative refractive index difference with the cladding layer 2 was 0.75%.

  The waveguide optical switch according to the present embodiment was formed by using the above-described optical waveguide and combining a straight waveguide and a curved waveguide.

  The optical switch element shown in FIG. 5 is a Mach-Zehnder interferometer circuit in which the effective optical path length difference of the arm waveguide is one half of the signal light wavelength. In this embodiment, the signal light wavelength is 1.55 μm, and the refractive index of the quartz glass is 1.45. Therefore, the difference in the actual arm optical waveguide length is 0.534 μm. Thin film heaters 41 and 42 having a thickness of 0.3 μm, a width of 20 μm, and a length of 2 mm were formed on the surface of the clad layer 2 positioned immediately above the embedded core portions 31 and 32 as a phase shifter by the thermo-optic effect. Further, heat insulating grooves 51, 52, 53 having a depth until the silicon substrate 1 is exposed are formed along the thin film heaters 41,.

As shown in FIG. 5A, in the unit optical switch element, the directional couplers 61 and 62 are formed by the curved waveguides being close to each other at two locations. Signal light input to the input port a ₁ or a _2, which depending on the presence or absence of energization of the thin film heater 41 is connected to the output port b ₁ or b _2.

  In this example, when N = 8 and a 1 × 8 optical switch element constituted by a Mach-Zehnder interferometer circuit shown in FIG. 5 was produced, the length of the 1 × 8 optical switch element was 6.5 mm. It was. The 1 × 8 optical switch elements were connected by a curved waveguide having a minimum bending radius R = 5 mm, and 8 sets of 1 × 8 optical switches based on the circuit configuration of the third invention of the present invention were arranged on one chip. The chip size was 110 mm × 22 mm, and 3 chips could be placed in a 6 inch diameter wafer.

  When optical characteristics were measured by connecting optical fibers to the input terminal and the output terminal of the 1 × 8 optical switch chip manufactured by the above method, the insertion loss was 1.5 dB or less and the extinction ratio for all three chips manufactured on the same wafer. It was 45 dB or more. Also, when the input and output were switched, light was input from the output terminal side, and the optical characteristics of the light output to the input terminal were measured, and the insertion loss and extinction ratio were the same characteristics.

  Furthermore, although four wafers were produced in another batch, the same optical characteristics were obtained in any wafer.

  A second embodiment of the present invention is shown below. The present embodiment is an example in which an N: N + 1 optical switch, which is a waveguide type optical switch based on the circuit configuration of the fifth aspect of the present invention, is manufactured by an optical circuit having a waveguide structure similar to that of the first embodiment. In addition, the description which overlaps with the description shown in FIG. 5 and mentioned above is abbreviate | omitted.

  In this example, when 8 = 8 + 1 optical switch based on the circuit configuration of the fifth invention of the present invention was manufactured with N = 8, the chip size when the 8: 8 + 1 optical switch 8 sets are arranged in one chip is as follows. Three chips could be placed in a wafer of 110 mm × 22 mm and a diameter of 6 inches (about 15.2 cm). When optical characteristics were measured by connecting optical fibers to the input and output terminals of the 8: 8 + 1 optical switch chip produced, the insertion loss was 1.5 dB or less between normal input and output ports, and between input and redundant output ports. However, it was 1.5 dB or less and the extinction ratio was 45 dB or more. All three chips made of the same wafer had equivalent optical characteristics.

  The present invention relates to a waveguide-type optical switch used in optical communication or the like, and particularly, an optical switch configured by cascading unit optical switch elements having 1 or 2 inputs / outputs, and the influence of manufacturing errors is small. Further, the present invention can be applied to a technique for realizing a circuit configuration with few waveguide intersections.

It is explanatory drawing which shows the circuit structure of the 1 * 4 optical switch by 1st embodiment of this invention. It is explanatory drawing which shows the circuit structure of the 4x1 optical switch by 2nd embodiment of this invention. It is explanatory drawing which shows the circuit structure of the 1 * 4 optical switch by 3rd embodiment of this invention. It is explanatory drawing which shows the circuit structure of the 4: 4 + 1 optical switch by 4th embodiment of this invention. FIG. 5A is a top view of a configuration example of the optical switch element used in the present invention, and FIG. 5B is a cross-sectional view taken along line AA in FIG. It is explanatory drawing which shows the circuit structure of the conventional 1x4 optical switch. It is explanatory drawing which shows the other circuit structure of the conventional 1x4 optical switch. It is explanatory drawing which shows the circuit structure of the conventional 4 + 1: 4 optical switch.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Silicon substrate 2 Clad layer 31, 32 Embedded type core part 41, 42 Thin film heater 51, 52, 53 Heat insulation groove 61, 62 Directional coupler 111-114, 311-314, 411-414, 611-614, 711- 714, 811 to 814 1-input 2-output unit optical switch elements 221-224, 421-424, 821-824 2-input 1-output unit optical switch elements 331-334, 731-734 Gate switch elements a, a ₁ , a ₂ input ports b, b ₁ , b ₂ output ports

Claims (6)

In a waveguide type optical switch configured by connecting N unit optical switch elements each having one input and two outputs in a column (where N is an integer of 3 or more),
Of the two output ports of the (i-1) th unit optical switch element (where i is an integer satisfying 2 ≦ i ≦ N−1), one output port is designated as the i-th unit optical switch. And connecting one output port of the two output ports of the i th unit optical switch element to the input port of the (i + 1) th unit optical switch element,
A unit optical switch comprising the unit optical switch elements connected in cascade with the other output port of the (i-1) th unit optical switch element and the other output port of the i-th unit optical switch element. A waveguide-type optical switch, which is arranged at positions facing each other across an element group so that the number of output ports on both sides of the unit optical switch element group is equal. In a waveguide type optical switch configured by connecting N unit optical switch elements each having two inputs and one output in a series of N (where N is an integer of 3 or more),
One of the two input ports of the i-th unit optical switch element (where i is an integer satisfying 2 ≦ i ≦ N−1) is designated as the (i−1) -th unit optical switch element. And one of the two input ports of the (i + 1) th unit optical switch element is connected to the output port of the i th unit optical switch element, and
A unit optical switch element group consisting of the unit optical switch elements connected in cascade with the other input port of the i-th unit optical switch element and the other input port of the (i + 1) th unit optical switch element. A waveguide-type optical switch characterized in that the number of input ports on both sides of the unit optical switch element group is made equal, so that the number of input ports is equal. The waveguide type optical switch according to claim 1,
Of the two output ports of the first unit optical switch element, a rear stage of an output port different from the output port connected to the second unit optical switch element, and two outputs of the i-th unit optical switch element Among the ports, the unit optical switch elements having one input and one output are arranged at the rear stage of the other output port and the rear stage of the Nth unit optical switch so that the numbers on both sides of the unit optical switch element group are equal. A waveguide-type optical switch characterized by being connected to The waveguide type optical switch according to claim 2,
A first stage of the input port of the first unit optical switch element, a front stage of the other input port of the two input ports of the i th unit optical switch element, and two of the Nth unit optical switch element Among the input ports, a unit optical switch element with one input and one output is connected to the preceding stage of the input port different from the input port connected to the (N-1) th unit optical switch element. A waveguide-type optical switch, characterized in that the number of both sides is connected to be equal. The waveguide type optical switch according to claim 1,
Of the two output ports of the first unit optical switch element, a rear stage of an output port different from the output port connected to the second unit optical switch element, and two outputs of the i-th unit optical switch element The number of unit optical switch elements with two inputs and one output is equal on both sides of the unit optical switch element group in the subsequent stage of the other output port and the subsequent stage of the Nth unit optical switch. A waveguide-type optical switch characterized by being connected to The waveguide type optical switch according to claim 2,
A first stage of the input port of the first unit optical switch element, a front stage of the other input port of the two input ports of the i-th unit optical switch element, and two of the Nth unit optical switch element Among the input ports, a unit optical switch element having one input and two outputs is connected to the preceding stage of the input port different from the input port connected to the (N-1) th unit optical switch element. A waveguide-type optical switch, characterized in that the number of both sides is connected to be equal.

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