Optical Transmitter / Receiver

Abstract

The present invention comprises an optical transmit unit (101) and an optical receive unit (107) and constitutes an optical transceiver (1) constituting a network, the optical transmit unit (101) transmitting data at a common symbol rate in the network. The optical transceiver (1) comprises: an N-input 1-output optical switch (105) that switches an optical signal (S2) to be received by the optical receive unit (107); a 1-input N-output optical switch (103) provided upstream of the optical switch (105) with respect to the optical signal; and N delay lines (d) which are connected between the optical switch (105) and the optical switch (103) and have different lengths. The optical signal input to the optical switch (103) is input to the optical switch (105) through one optical waveguide, and is received by the optical receive unit (107).

Description

[Technical Field]

[0001] The present disclosure relates to an optical transceiver for transmitting and receiving optical signals. [Background technology]

[0002] With the spread of the Internet, demand for data communication networks is rapidly increasing. To meet this rapidly increasing demand, optical communication networks capable of transmitting large volumes of data with low power consumption are being widely constructed. In optical communication networks, technologies utilizing optical switches that flexibly configure the combination of transceivers and their intermediate paths, such as CDC-ROADM (Colorless, Directionless, Contentionless Reconfigurable Optical Add Drop Multiplexer), have already been put into practical use and are used primarily in long-distance networks. Furthermore, to efficiently use networks utilizing optical switches in relatively short-distance networks such as within campuses or station buildings, research and development is underway to shorten the transient response time of devices used in optical switches and transceivers. Such technologies are described, for example, in Patent Document 1 and Non-Patent Document 1. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] International Publication No. WO / 2021 / 149243 [Non-patent literature]

[0004] [Non-Patent Document 1] Kenya Suzuki, Kazushige Yonenaga, Noboru Takachio, Toshiki Tanaka, Osamu Moriwaki, and Hiroshi Onaka: “Device Response Time Reduction for Large-Scale and Fast Optical Switching Systems,” Optical Fiber Communication Conference(OFC), Paper Tu6A.6(2021). Summary of the Invention

[0005] In optical communication networks, if the downtime caused by route changes can be reduced by shortening the transient response time of devices used in optical switches, transceivers, etc., the ratio of downtime can be kept low even when routes are changed frequently, thereby improving network utilization efficiency. However, the downtime caused by route changes is not determined solely by the transient response time of the devices, but also by the time required for the receiver to operate at the correct time interval (frequency) and timing (phase) to read data.

[0006] When receiving optical signals that have propagated from different transmitters over paths of different lengths due to a path change, the time interval (frequency) of the data sent by each transmitter may differ. In such cases, the receiver must adjust the time interval (frequency) at which it reads the data to match the received signal each time the path is changed. Furthermore, even if the time interval (frequency) of the data sent by each transmitter is the same, the timing at which each transmitter sends the data differs and the signals propagate over paths of different lengths. Therefore, the receiver must adjust the timing (phase) at which it reads the data to match the received signal each time the path is changed. This requires a long time to adjust the time interval (frequency) and timing (phase) at which it reads the data to match the received signal, which poses a problem in that it is not possible to reduce downtime due to path changes.

[0007] One aspect of the present disclosure has been made in consideration of the above points, and relates to an optical transceiver that reduces the time required to match the time interval and timing for reading data to a received signal when a route is changed in a network, and thus reduces the downtime associated with a route change.

[0008] JPEG0007795134000001.jpg104170 JPEG0007795134000002.jpg71170

[0009] According to the above embodiment, it is possible to provide an optical transceiver that can shorten the time required to match the time interval and timing for reading data to the received signal when changing the route in a network, and thus shorten the downtime caused by the route change. [Brief explanation of the drawings]

[0010] [Figure 1] FIG. 1 is a diagram for explaining an optical transceiver according to an embodiment of the present disclosure, and is a top view of the optical transceiver. DETAILED DESCRIPTION OF THE INVENTION

[0011] An embodiment of the present disclosure will be described below. The drawings used in the description of this embodiment are intended to explain the configuration, arrangement of each part, operation, function, and technical concept of the present disclosure, but do not limit the specific shape of the optical transceiver of the present disclosure, and do not necessarily accurately represent the aspect ratio or thickness.

[0012] FIG. 1 is a diagram illustrating an optical transceiver 1 according to the present embodiment, showing a top view of the optical transceiver 1. In this embodiment, multiple optical transceivers 1 constitute a network in which signals, including data signals, are transmitted and received via wired connections. Here, the present disclosure will be described using an optical network communication system including multiple optical transceivers 1 as an example. A data signal refers to a signal containing information to be transmitted, excluding control signals, among signals transmitted and received in an optical network system. The optical transceiver 1 includes a circuit fabricated using planar lightwave circuit technology, made of silica-based glass primarily composed of SiO2 on a silicon substrate, for example. The optical transceiver 1 includes an optical transmitter 101 and an optical receiver 107, and has the functions of transmitting and receiving optical signals. Furthermore, the optical transceiver 1 includes optical switches 103 and 105, which are waveguide-type optical switches fabricated using planar lightwave circuit technology and are driven using the thermo-optic effect.

[0013] Optical switches using the thermo-optic (TO) effect are highly reliable because they do not have moving parts like mechanical switches. Furthermore, because the temperature that causes the refractive index change is a scalar quantity, they have less polarization dependency than optical switches using the electro-optic effect, which changes the refractive index using a vector electric field, or liquid crystals. Thermo-optic switches can be realized using a variety of materials, but thermo-optic switches using planar lightwave circuits have the following advantages: 1) the silica-based glass optical waveguide material has excellent physical and chemical stability; 2) low connection loss with optical fiber; 3) high-density integration of switching elements, which allows integration with other optical circuit elements such as wavelength multiplexers / demultiplexers and branching circuits; and 4) multiple chips can be fabricated simultaneously on a wafer, making them suitable for mass production. Furthermore, the response speed of thermo-optic switches is limited by heat conduction and is therefore on the order of milliseconds, but this is fast enough for path switching in current optical fiber communication networks.

[0014] Optical switch 103 and optical switch 105 are connected by delay line bundle 104 including a plurality (N) of delay lines d, which are optical waveguides. N is an integer equal to or greater than 2. Optical switches 103 and 105 and optical receiving unit 107 constitute optical circuit 106. Note that such optical circuit 106 can be fabricated as a silica-based planar lightwave circuit device using the technology disclosed in Patent Document 1, for example.

[0015] 1 shows an example of the first embodiment in which N=4, that is, an optical transceiver 1 equipped with four delay lines d. Note that N may be any number equal to or greater than 2 and is not limited to 4.

[0016] Next, each of the above components will be described. The optical transmitter 101 receives a clock signal from a system clock 102 and transmits an optical signal S1 at a symbol rate synchronized with the clock signal. The clock signal is a common synchronization signal used throughout the entire network system including the optical transceiver 1.

[0017] The optical switch 103 is a switch with one input and N outputs. The optical switch 103 receives the optical signal S2 and outputs it to one of the four delay lines d. The optical switch 105 is a switch with four inputs and one output. The optical switch 105 receives the optical signal S2 from the four delay lines d and outputs it to the optical receiving unit 107. It is desirable that the optical switches 103 and 105 perform switching within a time that is the same as or shorter than the transient response time of an optical switch (not shown) that switches the path of the optical signal within the communication network system in which the optical transceiver 1 includes the optical signal.

[0018] The four delay lines d included in the delay line bundle 104 are optical waveguides, all of which have different lengths. Due to the differences in the lengths of the delay lines d, the timing at which a signal passing through the delay lines reaches the optical receiving unit 107 via the optical switch 105 differs. In this embodiment, when a path change is made within the optical communication network, the optical switch 103 selects one of the delay lines d of different lengths in accordance with the optimal timing for reading the signal, and outputs the signal. Therefore, in this embodiment, it is not necessary to adjust the timing for reading data to the received signal every time the path is changed in the optical receiving unit 107, and it is possible to reduce the downtime caused by a path change.

[0019] That is, a change in the path of an optical communication network can cause the timing at which a signal reaches the optical switch 103 to be earlier or later. In such a case, a difference occurs between the appropriate timing at which the optical receiving unit 107 reads the signal before and after the path change. In this embodiment, the optical switch 103 changes the delay line d from which the signal is output to a shorter or longer one, thereby enabling the signal to be received without changing the timing at which the optical receiving unit 107 reads the signal. The delay line d selected by the change is determined based on the difference in timing between before and after the path change. For example, if the timing at which the signal reaches the optical switch 103 is delayed, the delay line d from which the signal is output is changed to a shorter one. Furthermore, for example, if the timing at which the signal reaches the optical switch 103 is earlier, the delay line d is changed to a longer one.

[0020] Furthermore, in this embodiment, among the four delay lines d, the length of the shortest delay line d is Ld1, the length of the next shortest delay line d is Ld2, the length of the next shortest delay line d is Ld3, and the length of the longest delay line d is Ld4. In this case, better performance can be achieved if Ld2 = Ld1 + ΔL, Ld3 = Ld1 + 2ΔL, and Ld4 = Ld1 + 3ΔL are satisfied. That is, the lengths of the delay lines d are designed to differ by a constant length ΔL, and the length ΔL is equal to 1 / (symbol rate at which the optical transmitter 101 transmits data) / 4 (=N), i.e., the length of the optical signal S2 propagating through the delay line d in 1 / 4 (1 / N) of the period at which the data is read at the receiver. When all optical transceivers in a communication network are configured with the optical transceiver 1, all signals are synchronized to a common clock, and a common symbol rate is used in the system. Therefore, in this embodiment, even if a route is changed within the optical communication network, the time interval (frequency) for reading data does not need to be changed, and the same setting can be maintained before and after the change.

[0021] Furthermore, changing the route changes the optimal timing (phase) for reading data. To optimize this timing, the optimal timing for each route may be measured in advance, and the relationship between the route and the delay line d to be selected may be obtained. Then, the optical switch 103 may be configured to select an appropriate delay line d based on this relationship. In this way, even if a route is changed within the optical communication network, it is not necessary to change the timing (phase) for reading data on the optical receiving unit 107 side. Therefore, in an optical communication network in which all optical transceivers are configured with the optical transceiver 1 of the present invention, the present embodiment can shorten the time required to match the time interval (frequency) and timing (phase) for reading data to the received signal when a route is changed, thereby reducing downtime.

[0022] The disclosure detailed above is not limited to this embodiment, and includes design modifications and the like within the scope of the present invention. In particular, the number of delay lines d between the optical switches 103 and 105 is not limited to four as shown in Fig. 1, but may be any number, and the more the number, the more accurately the timing at which the signal reaches the optical switch 105 can be adjusted to match the signal read timing. [Explanation of symbols]

[0023] 1 Optical transceiver 101 Optical transmitter 102 System Clock 103 Optical Switch 104 Delay line bundle 105 Optical Switch 106 Optical circuit 107 Optical receiver

Claims

1. An optical transceiver that includes an optical transmitting unit and an optical receiving unit and configures a network, the optical transmitter transmits a data signal at a common symbol rate in the network; a first optical switch with N inputs and one output for switching optical signals received by the optical receiving unit; a second optical switch with one input and N outputs, which is provided upstream of the first optical switch in the optical signal; N optical waveguides each having a different length, connected between the first optical switch and the second optical switch; the optical signal input to the second optical switch passes through one of the optical waveguides, inputs to the first optical switch, and is received by the optical receiving unit; an optical transceiver, wherein the first optical switch and the second optical switch operate with a transient response time that is the same as or shorter than that of an optical switch used to change the propagation path of the optical signal in the network;

2.

3.

4. The first optical switch and the second optical switch are formed on a silicon substrate, and 2 4. The optical transceiver according to claim 1, wherein the optical transceiver is a waveguide-type optical switch made of silica-based glass containing SiO 2 as a main component and fabricated by planar lightwave circuit technology, and is driven using the thermo-optic effect.

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