Optical switch

Abstract

Provided is an optical switch which has a plurality of input ports and can be used as one or more 1×N optical switches depending on the selected input port.　The optical switch according to the present disclosure has: a plurality of 2×2 optical switch elements (110) arranged in a tree structure from a first column to a last column; a plurality of input ports (120) connected to one of the input terminals of the respective optical switch elements; and a plurality of output ports (1309) connected to the output terminals of the respective optical switch elements, wherein the plurality of optical switch elements (110): have a function such that when an optical signal can propagate between certain input / output terminals, an optical signal can also propagate between the other input / output terminals; are configured such that the other input terminal is connected to an output terminal of an optical switch element located in the preceding column or has no connection; and are configured such that an optical signal that has passed through an optical switch element is not inputted into the same optical switch element again.

Description

Optical switch

[0001] The present disclosure relates to optical switches.

[0002] With the spread of the Internet, the demand for data communication networks is rapidly increasing. To meet this rapidly increasing demand, optical communication networks that can transmit large amounts of data with low power consumption are being widely constructed.

[0003] In optical communication networks, there is a demand for increasing the availability of communication paths, and backup communication paths are constructed in addition to the current communication paths, and in the event of a failure of the current communication path, communication is switched to the backup communication path (see, for example, Non-Patent Documents 1 and 2).

[0004] In addition, optical fibers are generally used as communication paths in such optical communication networks. To check the quality of the optical fibers serving as communication paths, there is a demand for connecting an optical time domain reflectometer (OTDR) measuring instrument to the optical fiber and acquiring characteristic data of the optical fiber.

[0005] Optical fibers used in optical communication networks are often used in connection with optical switches. For example, when switching between the working communication path and the backup communication path as described above, it is preferable to connect a one-input, two-output optical switch or a two-input, one-output optical switch to the optical fiber. On the other hand, when connecting an OTDR or the like to the optical fiber to acquire optical fiber characteristic data, it is preferable to connect via a one-input, multi-output optical switch to avoid the need to change the optical wiring between the OTDR and the optical fiber.

[0006] As such, optical switches used in optical communication networks do not always require the same type of optical switch; for example, a one-input, two-output optical switch or a one-input, multiple-output optical switch is preferable. Optical switches of different types are generally provided as different hardware. Therefore, when using an optical switch of a different type, it is necessary to reconnect the optical wiring and reconnect it to a different optical switch.

[0007] NTT Advanced Technology Corporation, "NTT will begin general sales of a new model of optical switch with the ability to constantly monitor optical lines and instantly switch routes," [online], April 13, 2021, Advanced Technology Product Introduction Site, [Retrieved July 4, 2023], Internet <URL: https: / / keytech.ntt-at.co.jp / network / docs / p10229.pdf> Nippon Telegraph and Telephone Corporation, "N:1 Protection Function," [online], June 2016, NTT R&D Website, [Retrieved July 4, 2023], Internet <URL: https: / / www.rd.ntt / as / times / 093 / 01 / 02.html>

[0008] The present disclosure has been made in consideration of the above-mentioned problems, and its purpose is to provide an optical switch that has multiple input ports and can be used as one or multiple single-input, multiple-output optical switches depending on the selection of the multiple input ports.

[0009] In response to the above-mentioned problems, the present disclosure provides an optical switch comprising: a plurality of optical switch elements arranged in a tree shape from the first column to the last column, each having two inputs and two outputs; a plurality of input ports connected to one input terminal of each of the plurality of optical switch elements; and a plurality of output ports connected to the output terminal of each of the plurality of optical switch elements, wherein the plurality of optical switch elements are elements having a function such that when an optical signal can propagate between certain input / output terminals, the optical signal can also propagate between the remaining input / output terminals, and the other input terminal is connected to the output terminal of an optical switch element arranged in the previous column or has no connection destination, so that an optical signal that has passed through an optical switch element does not circulate and be input to the same optical switch element again.

[0010] 1 is a diagram illustrating a conceptual configuration of an optical switch 100 according to the present disclosure; FIG. 2 is a diagram illustrating a conceptual structure of an optical switch element 110; FIG. 3 is a diagram illustrating optical signal paths when the optical switch 100 according to the present disclosure is made to function as a single 1-input, 15-output optical switch; FIG. 4 is a diagram illustrating optical signal paths when one 1-input, 8-output optical switch and one 1-input, 7-output optical switch are made to function simultaneously in the optical switch 100 according to the present disclosure; and FIG. 5 is a diagram illustrating optical signal paths when one 1-input, 8-output optical switch, one 1-input, 3-output optical switch, and two 1-input, 2-output optical switches are made to function simultaneously in the optical switch 100 according to the present disclosure.

[0011] Various embodiments of the present disclosure will be described in detail below with reference to the drawings. The same or similar reference numerals indicate the same or similar elements, and redundant description may be omitted. Numerical values ​​are for illustrative purposes and are not intended to limit the technical scope of the present disclosure. Furthermore, the following description is an example, and some configurations may be omitted or modified, or additional configurations may be added, as long as they do not deviate from the gist of one embodiment of the present disclosure.

[0012] 1 is a diagram showing a conceptual configuration of an optical switch 100 according to the present disclosure. As shown in Fig. 1, the optical switch 100 according to the present disclosure includes two-input and two-output optical switch elements 110, input ports 120 connected to one input end of each of the optical switch elements 110, and an output port 130 connected to the output end of the optical switch element 110.

[0013] Although FIG. 1 depicts optical switch 100 as including fourteen optical switch elements 110a, 110b1-110b2, 110c1-110c4, 110d1-110d7, fourteen input ports 120a, 120b1-120b2, 120c1-120c4, 120d1-120d7, and fifteen output ports 130a1-130a2, 130b1-130b2, 130c1-130c2, 130d1-130d2, 130e1-130e2, 130f1-130f2, 130g1-130g2, 130h, this is for illustrative purposes only, and any number of optical switch elements 110, input ports 120, and output ports 130 may be provided depending on the design.

[0014] In the optical switch 100, one output end of the optical switch element 110a is connected to one input end of the optical switch element 110b1, and the other output end is connected to one input end of the optical switch element 110b2. One output end of the optical switch element 110b1 is connected to one input end of the optical switch element 110c1, and the other output end is connected to one input end of the optical switch element 110c2. One output end of the optical switch element 110b2 is connected to one input end of the optical switch element 110c3, and the other output end is connected to one input end of the optical switch element 110c4.

[0015] In this way, in the optical switch 100, two-input, two-output optical switch elements 110 are arranged so as to be connected in a tree configuration (hereinafter, for the sake of explanation, the row in which optical switch element 110a is arranged will be referred to as the first row, the row in which optical switch elements 110b1-110b2 are arranged will be referred to as the second row, the row in which optical switch elements 110c1-4 are arranged will be referred to as the third row, and the row in which optical switch elements 110d1-7 are arranged will be referred to as the fourth row). The output ends of the optical switch elements 110d1-110d7 arranged in the final column (the column closest to the output side, which in the example shown in FIG. 1 corresponds to the fourth column), and one output end of one of the optical switch elements 110c1-4 (which corresponds to the optical switch element 110c4 in FIG. 1, for example) arranged in the column immediately before the final column (which corresponds to the third column in the example shown in FIG. 1) are connected to output ports 130a1-130a2, 130b1-130b2, 130c1-130c2, 130d1-130d2, 130e1-130e2, 130f1-130f2, 130g1-130g2, and 130h, respectively.

[0016] In other words, in the optical switch 100 shown in FIG. 1, the optical switch elements 110 are arranged in a tree shape from the first column to the Nth column (N is an integer of 2 or more), and there is one optical switch element 110 in the first column, two in a 1×2 arrangement in the second column, four in a 2×2 arrangement in the third column, and two in the Nth column. （Ｎ－１） Both output ends of all the optical switch elements 110 arranged in the final row and one output end of one of the optical switch elements 110 arranged in the row immediately preceding the final row are connected to the output port 130, and the output ends of the other optical switch elements 110 are connected to one input end of the optical switch element 110 arranged in the row immediately following (on the output side).

[0017] In addition, in Figure 1, the optical switch elements 110 connected to the output port 130 are depicted as being arranged in the last row and one row before the last row, but this is for the purpose of illustration, and the output ends of all optical switch elements 110 arranged in the optical switch 100 can be connected to the output port 130.

[0018] On the other hand, in the optical switch 100, the optical switch element 110a arranged in the first column has two input terminals, one of which is connected to the input port 120a, and the other is not connected to any other terminal. As described above, one of the input terminals of the optical switch elements 110b1-110b2 arranged in the second column is connected to the output terminal of the optical switch element 110a, but the other terminals are connected to each of the input ports 120b1-120b2, respectively. This type of connection is repeated in a tree shape up to the Nth column (the final column). That is, in the optical switch 100, the input port 120 is connected to one input terminal of each of the optical switch elements 110 arranged in each column.

[0019] 1, the input ends of all optical switch elements 110 except for the optical switch element 110a arranged in the first column are depicted as being connected to the output ends of the optical switch elements 110 arranged in the column immediately preceding it and the input ports 120. However, the input ends of the optical switch elements 110 arranged in the second column and subsequent columns do not necessarily have to be connected to the input ports 120 (i.e., one of the two input ends may be connected to the output of another optical switch element 110, while the other may have no connection destination). For example, in FIG. 1, the optical switch element 110b1 is depicted as having one of its two input ends connected to the input port 120b1, but the input end of the optical switch element 110b1 may be connected only to one output end of the optical switch element 110a, and the other input end may have no connection destination.

[0020] Furthermore, the optical switch 100 is configured so that, in all optical signal paths from the input port 120 to the output port 130, an optical signal that has passed through an optical switch element 110 once circulates and is not input again to the same optical switch element 110. For example, an optical signal output from an optical switch element 110b1 arranged in the second row is propagated only to optical switch elements 110 arranged in the third row or later that are arranged closer to the output side, circulates through the optical switch element 110a located on the input side, and is not input again to the optical switch element 110b1.

[0021] FIG. 2 is a diagram illustrating the conceptual structure of the optical switch element 110. Each optical switch element 110 is an element that has a function such that when an optical signal can propagate between certain input / output terminals, the optical signal can also propagate between the remaining input / output terminals (when an optical signal can propagate between one of two inputs and one of two outputs, the optical signal can also propagate between the other of the two inputs and the other of the two outputs). For example, the optical switch element 110 may be a two-input, two-output Mach-Zehnder interferometer (hereinafter referred to as MZI) type element as shown in FIG. 2. Note that in FIG. 2, the optical switch element 110 is depicted with the left side as the input side and the right side as the output side. That is, in the optical switch element 110, optical signals are input through input terminals 2A and 2B, and optical signals are output through output terminals 2C and 2D.

[0022] As shown in FIG. 2, the optical switch element 110 includes two arm waveguides 112a-112b formed on a substrate 111, an optical splitter 113 installed on the arm waveguides 112a-112b and splitting an input optical signal, a thin-film heater 114 that heats at least one of the arm waveguides 112a-112b on the output side of the optical splitter 113, and an optical coupler 115 that combines and outputs the optical signals output from the optical splitter 113.

[0023] In one example, the arm waveguides 112a and 112b of the optical switch element 110 can be designed to have equal lengths. In this case, for example, when an optical signal is input from the input end 2A, the optical signal is output from the output end 2D under the condition that no power is supplied to the thin-film heater 114.

[0024] In another example, the arm waveguides 112a-112b of the optical switch element 110 can be designed so that the difference in their waveguide lengths is half (λ / 2) of the wavelength λ of the optical signal. In this case, for example, when an optical signal is input to the input end 2A, the optical signal is output from the output end 2C under the condition that no power is supplied to the thin-film heater 114.

[0025] Furthermore, in the optical switch element 110, the optical path length can be changed by applying a voltage to the thin-film heater 114 and heating at least one of the arm waveguides 112a-112b. (FIG. 2 depicts a configuration in which only the arm waveguide 112b is heated by the thin-film heater 114.) This change in the optical path length occurs because the refractive index of the arm waveguides 112a-112b heated by the thin-film heater 114 changes based on the thermo-optic effect. For example, if the wavelength of the input optical signal is λ, when the change in the optical path length due to heating using the thin-film heater 114 reaches λ / 2, the phase of the optical signal input to the optical coupler 115 changes (is inverted) by π, and accordingly, the output terminal from which the optical signal is output can be switched from 2D to 2C.

[0026] The optical switch 100 having such a configuration has a plurality of input ports, and can function as one or more single-input, multiple-output optical switches depending on the selection of the plurality of input ports.

[0027] 3 is a diagram showing the paths of optical signals when the optical switch 100 according to the present disclosure is made to function as a single 1-input, 15-output optical switch. As an example of the function of the optical switch 100 according to the present disclosure, if an optical signal is input using the input port 120a and a port from which the optical signal is output can be selected from all 15 output ports 130, the optical signal propagates along one of the paths indicated by the arrows in FIG. 3. In other words, in this case, the optical switch 100 functions as a 1-input, 15-output optical switch.

[0028] 4 is a diagram showing the path of an optical signal when one 1-input, 8-output optical switch and one 1-input, 7-output optical switch are simultaneously functioning in the optical switch 100 according to the present disclosure. As another example, if an optical signal is input using input port 120b1, and the optical signal is output via one of eight output ports 130a1-130a2, 130b1-130b2, 130c1-130c2, or 130d1-130d2 via one of optical switch elements 110b1, 110c1-110c2, or 110d1-110d4, the optical signal propagates along one of the paths indicated by solid arrows in FIG. 4. In other words, the optical switch 100 functions as a 1-input, 8-output optical switch A. At the same time, if an optical signal is input using input port 120b2 and the port from which the optical signal is output is selected from among seven output ports 130e1-130e2, 130f1-130f2, 130g1-130g2, and 130h via one of optical switch elements 110b2, 110c3-110c4, or 110d5-110d7, the optical signal input from input port 120b2 propagates along one of the paths indicated by dashed arrows in FIG. 4. That is, optical switch 100 also simultaneously functions as a 1-input, 7-output optical switch B. In other words, if input ports 120b1 and 120b2 are used simultaneously, optical switch 100 becomes an optical switch that can simultaneously function as a 1-input, 8-output optical switch A and a 1-input, 7-output optical switch B.

[0029] 5 is a diagram showing the paths of optical signals when one 1-input, 8-output optical switch, one 1-input, 3-output optical switch, and two 1-input, 2-output optical switches are simultaneously functioning in the optical switch 100 according to the present disclosure. As another example, when an optical signal is input using input port 120b1 to function the 1-input, 8-output optical switch A in the optical switch 100, if an optical signal is simultaneously input using input port 120c4 and the optical signal is output via one of the three output ports 130g1-130g2, 130h via optical switch elements 110c4 and 110d7, the optical signal input from 120c4 propagates along one of the paths indicated by the dashed arrows in FIG. 5. In other words, the optical switch 100 is an optical switch that can simultaneously function the 1-input, 8-output optical switch and the 1-input, 3-output optical switch C. Furthermore, in this configuration, if input port 120d5 is used simultaneously to input an optical signal, the optical signal input from input port 120d5 will propagate along one of the paths indicated by the light solid arrows in Figure 5, so it is possible to simultaneously operate a 1-input, 2-output optical switch D that can select the port from which the optical signal is output from one of output ports 130e1-130e2.Furthermore, if input port 120d6 is used simultaneously to input an optical signal, the optical signal input from input port 120d6 will propagate along one of the paths indicated by the light dotted arrows in Figure 5, so it is also possible to simultaneously operate a 1-input, 2-output optical switch E that can select the port from which the optical signal is output from one of output ports 130f1-130f2. In other words, if input port 120b1, input port 120c4, input port 120d5, and input port 120d6 are used simultaneously, optical switch 100 becomes an optical switch that can simultaneously function as one 1-input, 8-output optical switch A, one 1-input, 3-output optical switch C, and two 1-input, 2-output optical switches D and E.

[0030] In this way, if the relationship is satisfied such that optical signals input from input ports 120 that are used simultaneously among multiple input ports 120 are not input to the same optical switch element (i.e., multiple optical signals are not input to one optical switch element), the optical switch 100 allows the user to arbitrarily select and use one or more single-input, multi-output optical switches, as shown in Figures 3-5, depending on the selection of input port 120.

[0031] The optical switch 100 according to the present disclosure having such a configuration has the advantage that, even in situations where it is required to connect optical switches with different numbers of outputs, it is not necessary to reconnect the optical wiring and reconnect it to another optical switch.

[0032] For example, a single optical switch 100 can serve as both the one-input, two-output optical switch for switching between the working communication path and the backup communication path and the one-input, multiple-output optical switch for acquiring optical fiber characteristic data using an OTDR measuring instrument, eliminating the need for a process of reconnecting the optical switch for switching between the working communication path and the backup communication path as a separate optical switch after checking the quality of the optical fiber. These technical features can contribute to reducing the manufacturing lead time and manufacturing costs of optical switches used in optical communication networks.

[0033] The optical switch 100 according to the present disclosure can be fabricated by integrating it on a silicon substrate using silica-based planar lightwave circuit technology. The optical switch 100 having such a configuration is expected to achieve good optical characteristics at low cost.

[0034] Optical switch 100 may also include additional elements. For example, a one-input, one-output gate optical switch may be provided at the output of output port 130 of the optical switch in order to improve the extinction ratio of the output light from optical switch 100.

[0035] As described above, the optical switch according to the present disclosure can function as either a single single-input, multiple-output optical switch or multiple single-input, multiple-output optical switches, depending on the input port selection. Such an optical switch according to the present disclosure is superior to optical switches according to conventional techniques in terms of manufacturing lead time and manufacturing cost, and is expected to be applied as an optical switch for optical communication networks.

Claims

1. An optical switch comprising: a plurality of optical switch elements arranged in a tree shape from a first row to a last row, each having two inputs and two outputs; a plurality of input ports connected to one input end of each of the plurality of optical switch elements; and a plurality of output ports connected to an output end of each of the plurality of optical switch elements, wherein each of the plurality of optical switch elements is an element having a function such that when an optical signal can propagate between a certain input / output end, the optical signal can also propagate between the remaining input / output ends, and the other input end is configured to be connected to the output end of the optical switch element arranged in the previous row or to have no connection thereto, and wherein the optical signal that has passed through the optical switch element is configured not to circulate and be input to the same optical switch element again.

2. An optical switch as described in claim 1, wherein the output port is connected to an output end of the plurality of optical switch elements arranged in the final row and one output end of one of the plurality of optical switch elements arranged in the row one row before the final row.

3. The optical switch of claim 1, wherein said plurality of optical switch elements are Mach-Zehnder interferometer type elements having two arm waveguides.

4. The optical switch according to claim 3, wherein said plurality of optical switch elements further comprises a thin-film heater disposed on at least one of said two arm waveguides and is driven using the thermo-optic effect.

5. The optical switch of claim 1, wherein said optical switch is a silica-based planar lightwave circuit.

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