Optical transceiver, communication system, and bandwidth control method

Abstract

To provide an optical transceiver, a communication system, and a band control method capable of connecting a peer device supporting a lower transmission rate than a capable transmission rate by a host device to the host device.SOLUTION: In a communication system 1, an optical transceiver 40 includes an optical transmission / reception unit 43, a transmission processing unit (AFE) 44, and a signal processing unit 45. When a host device side transmission rate is as a first rate and one or more transmission rates lower than the first transmission rate are as i-th rate (i is a natural number from 2 to n), the signal processing unit includes a signal conversion circuit 51 including: a first mode which outputs the first rate uplink frame without converting a transmission rate and outputs the first rate downlink frame without converting a transmission rate; and one or more i-th modes which output i-th rate uplink frame after converted to the first rate and output the first rate downlink frame after converted to the i-th rate, as types of switchable operation modes.SELECTED DRAWING: Figure 2

Description

[Technical Field]

[0001] The present disclosure relates to an optical transceiver, a communication system, and a bandwidth control method. [Background technology]

[0002] Patent document 1 describes an optical transceiver that includes an optical connector, an electrical connector, an optical signal interface that converts optical signals to electrical signals and vice versa, and a frame conversion circuit that converts maintenance frames based on the TS-1000 standard and OAM frames based on IEEE standards and vice versa. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Patent Publication No. 2021-34978 Summary of the Invention [Problem to be solved by the invention]

[0004] As communication speeds in access networks increase, for example in Layer 2 networks, there is a trend toward replacing these with line concentrators that only support transmission rates above 1G (increasing functionality). In this case, in order to connect a counterpart device with a transmission rate of less than 1G to a Layer 2 network, it is necessary to adopt a concentrator that can handle low transmission rates, which increases the installation and management costs of the communication system.

[0005] In view of the above-described conventional problems, the present disclosure aims to enable a counterpart device with a lower transmission rate than the transmission rate that can be supported by a higher-level device (such as the above-mentioned line concentrator) to be connected to the higher-level device. [Means for solving the problem]

[0006] An optical transceiver according to one embodiment of the present disclosure comprises an optical transmitter / receiver that converts optical signals into electrical signals and vice versa, a transmission processing unit that excites optical signals in the optical transmitter / receiver and amplifies electrical signals input from the optical transmitter / receiver, and a signal processing unit that outputs upstream frames input from the transmission processing unit to a higher-level device and outputs downstream frames input from the higher-level device to the transmission processing unit, wherein the transmission rate on the higher-level device side is a first rate and one or more transmission rates lower than the first rate are an ith rate (i = a natural number from 2 to n), and the signal processing unit has a signal conversion circuit that includes the following first mode and one or more ith modes as switchable operating mode types:

[0007] First mode: An operation mode in which upstream frames at the first rate are output without converting the transmission rate, and downstream frames at the first rate are output without converting the transmission rate. i-th mode: An operation mode in which upstream frames at the i-th rate are converted to the first rate and output, and downstream frames at the first rate are converted to the i-th rate and output.

[0008] A communication system according to one embodiment of the present disclosure comprises an upper device having a plurality of SFP ports and one or more optical transceivers connected to the SFP ports, wherein the transmission rate on the upper device side is a first rate and one or more transmission rates lower than the first rate are an ith rate (i = a natural number from 2 to n), and the types of operating modes to which the optical transceiver can switch include the first mode and one or more ith modes.

[0009] A method according to one aspect of the present disclosure is a bandwidth control method executed in the above-described communication system, and includes the steps of: the optical transceiver determining the type based on the identification result of the transmission rate of an upstream frame received from a counterpart device; the optical transceiver notifying the upper device of the determined type; and the upper device limiting the communication bandwidth related to the SFP port to which the optical transceiver is attached to an equivalent to the i-th rate if the notified type is the i-th mode.

[0010] A method according to another aspect of the present disclosure is a bandwidth control method executed in the above-described communication system, and includes a step in which the optical transceiver determines the type based on the identification result of the transmission rate of an upstream frame received from a counterpart device, and a step in which the optical transceiver limits the bandwidth of communication with the counterpart device to an equivalent to the i-th rate if the determined type is the i-th mode.

[0011] The present disclosure can be realized not only as a system and device having the above-described characteristic configuration, but also as a program for causing a computer to execute such characteristic configuration. Furthermore, the present disclosure can be realized as a semiconductor integrated circuit that realizes part or all of the system and device. [Effects of the Invention]

[0012] According to the present disclosure, it is possible to connect an opposing device with a lower transmission rate than the transmission rate that the upper device can support to the upper device. [Brief explanation of the drawings]

[0013] [Figure 1] FIG. 1 is a block diagram showing an example of the overall configuration of a communication system. [Figure 2] FIG. 2 is a block diagram illustrating an example of the internal configuration of the optical transceiver. [Figure 3] FIG. 3 is a block diagram showing an example of the internal configuration of the signal conversion circuit. [Figure 4] FIG. 4 is an explanatory diagram showing an example of a method for determining the encoding method. [Figure 5] FIG. 5 is a block diagram showing an example of a bandwidth control function of a concentrator. [Figure 6] FIG. 6 is a flowchart showing an example of control communication related to bandwidth control. [Figure 7] FIG. 7 is a block diagram showing another example of the internal configuration of the optical transceiver. [Figure 8]FIG. 8 is a block diagram showing another example of the internal configuration of the signal conversion circuit. DETAILED DESCRIPTION OF THE INVENTION

[0014] <Summary of Embodiments of the Present Disclosure> The following provides an outline of embodiments of the present disclosure. (1) The optical transceiver of this embodiment comprises an optical transmitter / receiver that converts optical signals into electrical signals and vice versa, a transmission processing unit that excites optical signals in the optical transmitter / receiver and amplifies electrical signals input from the optical transmitter / receiver, and a signal processing unit that outputs upstream frames input from the transmission processing unit to a higher-level device and outputs downstream frames input from the higher-level device to the transmission processing unit.

[0015] In the optical transceiver of this embodiment, when the transmission rate on the upper device side is a first rate and one or more transmission rates lower than the first rate are an ith rate (i = a natural number from 2 to n), the signal processing unit has a signal conversion circuit that includes the following first mode and one or more ith modes as switchable operating mode types: First mode: An operation mode in which upstream frames at the first rate are output without converting the transmission rate, and downstream frames at the first rate are output without converting the transmission rate. i-th mode: An operation mode in which upstream frames at the i-th rate are converted to the first rate and output, and downstream frames at the first rate are converted to the i-th rate and output.

[0016] According to the optical transceiver of this embodiment, the signal processing unit has a signal conversion circuit that includes the first mode and one or more i-th modes as switchable operation mode types. Therefore, by operating the optical transceiver in the i-th mode, it is possible to connect to a host device a counterpart device with a transmission rate lower than the transmission rate that the host device can support.

[0017] (2) In the optical transceiver of this embodiment, the signal processing unit may further include a signal identification unit that identifies the encoding method of the upstream frame input from the transmission processing unit, and an operating mode determination unit that determines the type of operating mode based on the identification result by the signal identification unit and instructs the signal conversion circuit to switch to the determined type.

[0018] In this case, the operating mode determination unit instructs the signal conversion circuit to switch the operating mode type depending on the identification result by the signal identification unit, which identifies the encoding method of the upstream frame, so that the optical transceiver can automatically switch the operating mode type.

[0019] (3) In the optical transceiver of this embodiment, the signal processing unit may further include a flow control unit that, when the determined type is the i mode, sends a control frame to the upper device to temporarily stop the upper device from sending downstream frames.

[0020] This eliminates the need to implement a bandwidth control function in the host device to accommodate optical transceivers operating in the i-th mode, which has the advantage of reducing the manufacturing costs of the host device.

[0021] (4) In the optical transceiver of this embodiment, the operating mode determination unit may transmit a control signal to the higher-level device indicating that the optical transceiver is attached to the higher-level device, on the condition that the type of operating mode has been determined.

[0022] The reason is that if the host device is notified of the installation of an optical transceiver before the operating mode has been determined, the host device will not be able to recognize the transmission rate that should be applied to the optical transceiver.

[0023] (5) In the optical transceiver of this embodiment, the value of n may be 2, the first rate may be 1G, and the second rate may be 100M.

[0024] In this case, an optical transceiver is obtained in which the first rate is 1G and the second rate is 100M.

[0025] (6) In the optical transceiver of this embodiment, the value of n may be 3, the first rate may be 10G, the second rate may be 1G, and the third rate may be 100M.

[0026] In this case, an optical transceiver is obtained in which the first rate is 10G, the second rate is 1G, and the third rate is 100M.

[0027] (7) The communication system of this embodiment includes a host device having a pluggable port, and one or more optical transceivers connected to the pluggable port. In the communication system of this embodiment, when the transmission rate on the upper device side is a first rate and one or more transmission rates lower than the first rate are an ith rate (i = a natural number from 2 to n), the types of operating modes that the optical transceiver can switch between include the above-mentioned first mode and one or more ith modes.

[0028] According to the communication system of this embodiment, the types of operating modes that the optical transceiver can switch to include the above-mentioned first mode and one or more i-th modes, so by operating the optical transceiver in the i-th mode, it is possible to connect to the upper device an opposing device with a transmission rate lower than the transmission rate that the upper device can handle.

[0029] (8) The bandwidth control method of this embodiment is a bandwidth control method executed in the above-mentioned communication system, and includes the steps of: the optical transceiver determining the type based on the identification result of the transmission rate of the upstream frame received from the opposing device; the optical transceiver notifying the upper device of the determined type; and the upper device limiting the communication bandwidth related to the SFP port to which the optical transceiver is attached to an equivalent to the i-th rate if the notified type is the i-th mode.

[0030] According to the bandwidth control method of this embodiment, when the notified type is the i-th mode, the upper device limits the communication bandwidth related to the SFP port to which the optical transceiver is attached to an amount equivalent to the i-th rate, thereby preventing frames from being discarded due to buffer overflow in the optical transceiver.

[0031] (9) The bandwidth control method of this embodiment is a bandwidth control method executed in the above-mentioned communication system, and includes the steps of: the optical transceiver determining the type based on the identification result of the transmission rate of the upstream frame received from the opposing device; and the optical transceiver, if the determined type is the i mode, transmitting a control frame to the upper device to temporarily stop the transmission of downstream frames by the upper device.

[0032] According to the bandwidth control method of this embodiment, when the optical transceiver determines that the type is the i-th mode, the concentrator transmits a control frame to the upper device to temporarily stop the upper device from transmitting downstream frames, thereby preventing frames from being discarded due to buffer overflow in the optical transceiver.

[0033] <Details of the embodiment of the present invention> DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention will be described in detail below with reference to the accompanying drawings. At least some of the embodiments described below may be combined in any desired manner.

[0034] [Transmission rate and communication frame notation, etc.] In this embodiment, when the communication rate of the information to be communicated is 1 Gbps and 100 Mbps, the transmission rates become 1.25 Gbps and 125 Mbps, respectively, after encoding for transmission, but the transmission rates may also be abbreviated as "1G" and "100M." Therefore, "1G" actually means a transmission rate exceeding 1 Gbps.

[0035] Furthermore, "10G," "25G," and "100G" are also abbreviated transmission rates, and the actual transmission rates are greater than the abbreviated values. In this embodiment, the term "SFP" (Small Form Factor Pluggable) is used as a general term for SFP, SFP+, SFP28, QSFP, QSFP28, and their upwardly compatible pluggable optical modules.

[0036] In this embodiment, the concentrator 2 is a type of higher-level device from the perspective of the associated device 4. Therefore, among communication frames passing through the inside of the optical transceiver 40, communication frames traveling from the associated device 4 to the concentrator 2 are referred to as “upstream frames.” Furthermore, among the communication frames passing through the inside of the optical transceiver 40, a communication frame going from the concentrator 2 to the opposite device 4 is called a "downstream frame."

[0037] In this embodiment, the transmission rate on the concentrator 2 side, i.e., the transmission rate of the communication frame (electrical signal) at the port of the L2 switch 22, is referred to as the "first rate." One or more transmission rates lower than the first rate are referred to as the "i-th rate" (i = a natural number from 2 to n, i.e., i = 2, 3, ...). Note that when i is 3 or greater, the larger the i, the lower the transmission rate.

[0038] For example, if the transmission rate on the concentrator 2 side of a given pluggable port 20 is 1G and one type of transmission rate lower than 1G is 100M, the first rate is 1G and the second rate is 100M. Furthermore, if the transmission rate on the concentrator 2 side at a specified pluggable port 20 is 10G and the two transmission rates lower than 10G are 1G and 100M, the first rate is 10G, the second rate is 1G, and the third rate is 100M.

[0039] [Overall configuration of communication system] FIG. 1 is a block diagram showing an example of the overall configuration of a communication system 1. As shown in FIG. As shown in FIG. 1, a communication system 1 of this embodiment includes a concentrator 2, optical transceivers 30 and 40, and an opposing device 4 connected to the optical transceivers 30 and 40 by an optical fiber 3.

[0040] In the example of Figure 1, ten optical transceivers 30, 40 and opposing devices 4 are connected to one concentrator 2, but it is sufficient if at least one optical transceiver 30, 40 and opposing device 4 are connected to one concentrator 2. The concentrator 2 of this embodiment is, for example, a 100 Gigabit Ethernet switch capable of relaying Ethernet frames ("Ethernet" is a registered trademark).

[0041] The concentrator 2 includes a housing 21 having a plurality of pluggable ports 20, each of which is, for example, an SFP port, and an L2 switch 22 and a management control unit 23 housed in the housing 21. Hereinafter, the pluggable port 20 may be abbreviated as "port 20." The transmission rate of communication frames (electrical signals) at each port of the L2 switch 22 is equal to or higher than 1 G and equal to or lower than 100 G. Therefore, the concentrator 2 in Fig. 1 is a concentrator that does not support transmission rates lower than 1 G.

[0042] The management control unit 23 communicates with a communication terminal (not shown) such as a personal computer of a communication administrator to acquire setting information. According to the acquired setting information, the management control unit 23 sets the communication band and VLAN (Virtual LAN) of each port of the L2 switch 22. Each port of the L2 switch 22 is electrically connected to a plurality of pluggable ports 20 in one-to-one correspondence.

[0043] The plurality of pluggable ports 20 are fitted with, for example, SFP type optical transceivers (hereinafter also referred to as "optical modules") 30, 40. 1, the optical module 30 without diagonal lines is a conventional transceiver (hereinafter referred to as a "single-rate type") with a single transmission rate on the opposing device 4 side. The optical module 40 with diagonal lines is a transceiver of this embodiment (hereinafter referred to as a "multi-rate type") with a transmission rate on the opposing device 4 side that can be switched between 1G and less than 1G.

[0044] [The Significance of Multi-Rate Optical Transceivers] The opposite device 4 that can be connected to the concentrator 2 may be, for example, the following communication devices. Device 1) 5G (5th Generation) CU (Central Unit) with a transmission rate of over 1G (10G or 25G in Figure 1) Device 2) 5G DU (Distributed Unit) with a transmission rate of over 1G (10G or 25G in Figure 1) Device 3) 5G RU (Radio Unit) with a transmission rate of over 1G (10G or 25G in Figure 1) Device 4) Other concentrators (upper side) with a transmission rate of more than 1G (10G or 100G in Figure 1)

[0045] Device 5) IoT (Internet of Things) server with a transmission rate of 1G Device 6) Media converter with a transmission rate of 1G Device 7) IoT gateway with a transmission rate of less than 1G (100M) Device 8) Media converter with a transmission rate of less than 1G (100M)

[0046] As communication speeds in access networks increase, Layer 2 networks are being replaced with concentrators that only support transmission rates of 1G or higher (higher functionality). 1 is one such example, and does not have an SFP port that can connect to an optical module with a transmission rate of less than 1 G. Therefore, if only single-rate modules are available, a concentrator with an SFP port that can accommodate optical modules with a transmission rate of less than 1 G must be manufactured, which poses a problem of increased installation and management costs for the communication system 1.

[0047] In contrast, the optical module 40 of this embodiment is a multi-rate type in which the transmission rate on the opposing device 4 side can be switched between 1G and less than 1G. Therefore, by operating the optical transceiver 40 at a transmission rate of less than 1G, it is possible to connect a counterpart device 4 of less than 1G to a concentrator 2 having a 1G pluggable port 20. This eliminates the need to employ a concentrator that can accommodate a low-speed counterpart device 4, thereby preventing an increase in the equipment and management costs of the communication system 1.

[0048] [Internal configuration of a multi-rate optical transceiver] FIG. 2 is a block diagram showing an example of the internal configuration of the optical transceiver 40. As shown in FIG. As shown in Figure 2, the optical transceiver 40 of this embodiment is a transceiver with a transmission rate (first rate) on the concentrator 2 side of 1.25 Gbps, and the transmission rate on the opposing device 4 side (left side) can be switched between the first rate (1.25 Gbps) or the second rate (125 Mbps).

[0049] The optical transceiver 40 includes a housing 41 and electronic components mounted on a circuit board (not shown) inside the housing 41. The electronic components include, in order from the opposing side (left side) to the line concentration side (right side), an optical connector 42, an optical transmitting / receiving unit 43, a transmission processing unit 44, a signal processing unit 45, and an electrical connector 46.

[0050] The optical connector 42 is an LC connector to which the optical fiber 3 can be detachably connected. The electrical connector 46 is a connector that can be detachably connected to an electrical connector (not shown) provided inside the port 20 of the line concentrator 2.

[0051] The optical transmitter / receiver 43 is an electronic component that converts optical signals into electrical signals and vice versa, and includes a laser diode 47 and a photodiode 48 . The laser diode 47 converts the 1G or 100M electrical signal into an optical signal and sends it to the optical connector 42. The photodiode 48 converts the 1G or 100M optical signal into an electrical signal and outputs it to the post-amplifier 50.

[0052] The transmission processing unit 44 is an electronic component that excites the optical transmitting / receiving unit 43 with an optical signal and amplifies the electrical signal input from the optical transmitting / receiving unit 43 , and includes a laser driver 49 and a post-amplifier 50 . The laser driver 49 drives the laser diode 47 with the 1G or 100M electrical signal input from the signal processing unit 45. The post-amplifier 50 amplifies the 1G or 100M electrical signal input from the photodiode 48 and outputs it to the signal processing unit 45.

[0053] In this embodiment, the optical transceiver 43 and the transmission processor 44 are made of electronic components for 1.25 Gbps. In addition, the optical transmitting / receiving unit 43 and the transmission processing unit 44 may be composed of a TOSA (Transmitter Optical SubAssembly), which is an electronic component that combines the functions of the transmitting side, and a ROSA (Receiver Optical SubAssembly), which is an electronic component that combines the functions of the receiving side.

[0054] The signal processing unit 45 is an electronic circuit including, for example, an FPGA (Field-Programmable Gate Array). The signal processing unit 45 may also include an ASIC (Application Specific Integrated Circuit) or a CPU (Central Processing Unit). The signal processing unit 45 has multiple functional units realized by configuring the FPGA, including a signal conversion circuit 51, an operation mode determination unit (hereinafter sometimes abbreviated as "determination unit") 52, and a signal identification unit 53.

[0055] The signal conversion circuit 51 has two types of switchable operation modes, n, and can execute the following two operation modes. First mode: An operating mode in which upstream frames at the first rate (1G: high speed) input to the device are output to the outside without converting the transmission rate, and downstream frames at the first rate (1G: high speed) input to the device are output to the outside without converting the transmission rate.

[0056] Second mode: An operating mode in which upstream frames input at the second rate (100M: low speed) are converted to the first rate (1G: high speed) and output to the outside, and downstream frames input at the first rate (1G: high speed) are converted to the second rate (100M: low speed) and output to the outside.

[0057] Therefore, when the signal conversion circuit 51 is executing the first mode, it outputs the 1G upstream frame input from the postamplifier 50 to the electrical connector 46 as is, and outputs the 1G downstream frame input from the electrical connector 46 to the laser driver 49 as is. In addition, while executing the second mode, the signal conversion circuit 51 converts the transmission rate of the 100M upstream frame input from the postamplifier 50 to 1G and outputs it to the electrical connector 46, and converts the transmission rate of the 1G downstream frame input from the electrical connector 46 to 100M and outputs it to the laser driver 49.

[0058] The signal identification unit 53 determines whether the encoding method of the upstream frame (upstream frame received from the opposite device 4) input from the post-amplifier 50 is a method adopted at the second rate (100M), and outputs the determination result to the decision unit 52. The operation mode determination unit 52 determines the type of operation mode (first mode or second mode) to be executed by the signal conversion circuit 51 based on the encoding method determination result input from the signal identification unit 53, and outputs the determined type to the signal conversion circuit 51.

[0059] Specifically, if the determination result is not the second rate (100M) encoding method, the determination unit 52 outputs to the signal conversion circuit 51 a control signal instructing the first mode which does not involve rate conversion of communication frames. Conversely, if the determination result is the second rate (100M) encoding method, the determination unit 52 outputs to the signal conversion circuit 51 a control signal instructing the second mode involving rate conversion of communication frames.

[0060] Therefore, when the transmission rate of the opposite device 4 is the first rate (1G), the signal conversion circuit 51 operates in the first mode, and rate conversion of the upstream and downstream frames is not performed. Conversely, when the transmission rate of the opposing device 4 is the second rate (100M), the signal conversion circuit 51 operates in the second mode, and rate conversion is performed on upstream frames from the second rate (100M) to the first rate (1G), and rate conversion is performed on downstream frames from the first rate (1G) to the second rate (100M).

[0061] [Configuration example of signal conversion circuit] FIG. 3 is a block diagram showing an example of the internal configuration of the signal conversion circuit 51. As shown in FIG. 3, the signal processing unit 45 includes an opposing SerDes (SERializer / DESerializer) unit 54 and a concentrator SerDes unit 55. The signal conversion circuit 51 is interposed between the SerDes units 54 and 55.

[0062] The signal conversion circuit 51 includes a receiving buffer 61 and an upstream rate switching unit 62 as processing units for upstream frames. The upstream rate switching unit 62 has a 1-input, 2-output selector 62A, a 2-input, 1-output selector 62B, a 1G receiving circuit 62C interposed between terminals a of the selectors 62A and 62B, and a serially connected 100M receiving circuit 62D and 100M / 1G conversion circuit 62E interposed between terminals b of the selectors 62A and 62B.

[0063] The signal conversion circuit 51 includes a transmission buffer 71 and a downstream rate switching unit 72 as downstream frame processing units. The downstream rate switching unit 72 has a 1-input, 2-output selector 72A, a 2-input, 1-output selector 72B, a 1G transmission circuit 72C interposed between terminals a of the selectors 72A and 72B, and a serially connected 1G / 100M conversion circuit 72E and 100M transmission circuit 72D interposed between terminals b of the selectors 72A and 72B.

[0064] An upstream frame output from the SerDes unit 54 on the opposite side is input to the signal identification unit 53 and the selector 62A. The signal identification unit 53 converts the upstream frame into a predetermined low-speed code (for example, NRZI: Non Return Zero Inversion) on the condition that the Rx_LOS signal supplied from the transmission processing unit 44 indicates reception of an optical signal, determines whether or not the converted low-speed code has a predetermined pattern (for example, an idle code), and outputs the determination result to the operation mode determination unit 52. The method for determining the predetermined pattern of the low-speed code will be described in detail later.

[0065] The signal identifying unit 53 does not perform the above determination every time an upstream frame is received, but performs it when an optical signal is received (when there is a change from the extinction state). That is, the signal identifying unit 53 identifies an idle signal in an idle state in which an upstream frame has not yet been received, and maintains the identification result while an optical signal is being received.

[0066] If the judgment result input from the signal identification unit 53 is not for low speed (100M), the operating mode determination unit 52 outputs a control signal to each selector 62A, 62B, 72A, 72B of the signal conversion circuit 51 to instruct the selection of terminal a (first mode). If the judgment result input from the signal identification unit 53 is for low speed (100M), the operating mode determination unit 52 outputs a control signal instructing the selection of terminal b (second mode) to each selector 62A, 62B, 72A, 72B of the signal conversion circuit 51.

[0067] When the selectors 62A and 62B are selecting terminal a (first mode), an upstream frame at the first rate (1G) input from the opposing SerDes unit 54 follows the path of selector 62A → 1G receiving circuit 62C → selector 62B → receiving buffer 61. Therefore, the upstream frames at the first rate (1G) are not converted in transmission rate and are stored as is in the receiving buffer 61. The stored upstream frames at the first rate (1G) are output to the SerDes unit 55 on the line concentrator side.

[0068] When the selectors 62A and 62B are selecting terminal b (second mode), the upstream frame at the second rate (100M) input from the opposite SerDes unit 54 follows the path of selector 62A → 100M receiving circuit 62D → 100M / 1G conversion circuit 62E → selector 62B → receiving buffer 61. Therefore, upstream frames at the second rate (100M) are converted to the first rate (1G) and stored in the receiving buffer 61. The stored upstream frames at the first rate (1G) are output to the SerDes unit 55 on the line concentrator side.

[0069] The receive buffer 61 is also necessary to prevent underruns, i.e., a frame is output to the SerDes unit 55 only after at least one entire frame has been input to the buffer, or after enough frame data to prevent underruns even if the frame is of the maximum length has been input to the receive buffer 61.

[0070] High-speed (1G) downstream frames output from the concentrator SerDes unit 55 are accumulated in a transmission buffer 71. When the selectors 72A and 72B are selecting terminal a (first mode), a downstream frame at the first rate (1G) output from the transmission buffer 71 follows the path of the selector 72A → the 1G transmission circuit 72C → the selector 72B. Therefore, the downstream frame at the first rate (1G) is output to the opposite SerDes unit 54 without its transmission rate being converted.

[0071] When the selectors 72A and 72B are selecting terminal b (second mode), a downstream frame at the first rate (1G) output from the transmission buffer 71 follows the path of the selector 72A → 1G / 100M conversion circuit 72E → 100M transmission circuit 72D → selector 72B. Therefore, the transmission rate of the downstream frame at the first rate (1G) is converted to the second rate (100M) and output to the SerDes unit 54 on the opposite side.

[0072] As shown in FIG. 3, the operation mode determination unit 52 can output a control signal (Mod_Abs) indicating whether its own module is attached to the SFP port 20 or not to the outside. This control signal is output on the condition that the operation mode is determined, and is transmitted to the management control unit 23 of the concentrator 2. The reason for this is that if the concentrator 2 is notified of the installation of the optical module 40 before the operation mode is determined, the concentrator 2 may start communication without recognizing the transmission rate that should be applied to the optical module 40, which may cause malfunction. The operation mode determination unit 52 can also execute control communication with the management control unit 23 of the concentrator 2 in accordance with a predetermined communication protocol (for example, I2C).

[0073] [Method for determining encoding method] FIG. 4 is an explanatory diagram showing an example of a method for determining the encoding method. The determination method in FIG. 4 is a method for determining whether or not a low-speed (100M) communication frame encoding method is present by sampling a 125 MHz carrier signal at 1.25 GHz.

[0074] Specifically, the signal identifying unit 53 samples the upstream frame at 1.25 GHz to generate a bit string with a 10-bit width, and finds change points in the generated bit string (step ST11). Next, the signal identification unit 53 samples the data by regarding the point shifted 5 bits from the transition point as the center of the carrier signal (step ST12), converts the sampled data using NRZI, and checks whether the converted data matches the code defined by the transmission code (4B / 5B) (step ST13).

[0075] In the illustrated example, the bit string of the sampled data is a repetition of "01010" and "10101", which matches the code for 125 Mbps. In this case, the signal identification unit 53 determines that the transmission rate of the upstream frame is 125 Mbps. On the other hand, if the bit string of the sampled data does not match the 125 Mbps code, the signal identifying unit 53 determines that the transmission rate of the upstream frame is not 125 Mbps.

[0076] [Bandwidth control function of the concentrator] FIG. 5 is a block diagram showing an example of the bandwidth control function of the concentrator 2. As shown in FIG. 5, the L2 switch 22 of the concentrator 2 includes a switch unit 24, flow control units 25A and 25B, frame transmission units 26A and 26B, and frame reception units 27A and 27B. The flow control units 25A and 25B, the frame transmission units 26A and 26B, and the frame reception units 27A and 27B are provided for each pluggable port 20.

[0077] In the illustrated example, the flow control unit 25A, the frame transmitting unit 26A, and the frame receiving unit 27A correspond to the pluggable port 20 with port number P1. Similarly, a flow control unit 25B, a frame transmitting unit 26B, and a frame receiving unit 27B correspond to the pluggable port 20 with port number P2.

[0078] The management control unit 23 of the concentrator 2 has a bandwidth setting unit 28 that instructs the flow control units 25A and 25B whether or not to impose a bandwidth restriction of less than 1G. The flow control units 25A and 25B have a buffering function for communication frames and a shaping function for narrowing the communication band of high-speed (1G) communication frames. When instructed by the bandwidth setting unit 28, the flow control units 25A and 25B narrow the communication bandwidth of high-speed (1G) communication frames.

[0079] Here, assume that the optical transceiver 40A attached to port number P1 decides to operate in the "first mode" (high speed: 1G), and the optical transceiver 40B attached to port number P2 decides to operate in the "second mode" (low speed: 100M). In this case, the optical transceiver 40A transmits a control signal including identification information M1 representing the first mode to the bandwidth setting unit 28, and the optical transceiver 40B transmits a control signal including identification information M2 representing the second mode to the bandwidth setting unit 28.

[0080] The band setting unit 28 that has received the identification information M1 does not issue a command to narrow the communication band to the flow control unit 25A that corresponds to the port number P1. In this case, the flow control unit 25A does not limit the bandwidth of the upstream frames received by the frame receiving unit 27A and the downstream frames transmitted by the frame transmitting unit 26A.

[0081] The band setting unit 28, which has received the identification information M2, issues a command to narrow the communication band to the flow control unit 25B corresponding to the port number P2. In this case, the flow control unit 25B performs bandwidth control to limit the bandwidth of the upstream frame received by the frame receiving unit 27B and the downstream frame transmitted by the frame transmitting unit 26B to a second rate (low speed: 100M).

[0082] [Control communication related to bandwidth control] FIG. 6 is a flowchart showing an example of control communication related to bandwidth control. As shown in FIG. 6, the optical module 40 waits to receive an optical signal (step ST21), and upon receiving an optical signal from the opposite device (YES in step ST22), it identifies the idle code of the signal received from the opposite device 4 (step ST23). Next, the optical module 40 determines whether the identified idle code is a code for the second rate (100M) (step ST24).

[0083] If the determination result in step ST24 is negative, the optical module 40 sets its own operation mode to the first mode (high speed: 1G) (step ST25). If the determination result in step ST24 is positive, the optical module 40 sets its own operation mode to the second mode (low speed: 100M) (step ST26). Next, the optical module 40 transmits to the concentrator 2 a control signal S1 (for example, the above-mentioned Mod_Abs) notifying the standby of the optical module itself, and a control signal S2 including identification information M1 and M2 of the determined operation mode.

[0084] When the concentrator 2 receives the control signals S1 and S2 from the optical module 40 (step ST27), it extracts the operating modes M1 and M2 of the optical module 40 from the control signal S2 (step ST28), and determines whether or not to perform bandwidth control for the optical module 40 based on the identification information M1 and M2 of the extracted operating modes (step ST29). In this case, the concentrator 2 does not perform bandwidth limitation by the flow control unit 25 if the extracted identification information of the operation mode is M1 (first mode).

[0085] Furthermore, if the extracted operation mode identification information is M2 (second mode), the concentrator 2 causes the flow control unit 25 to perform bandwidth control to limit the communication bandwidth for the optical module 40 to a second rate (low speed: 100M). Next, based on the received control signal S1, the concentrator 2 activates the port of the L2 switch 22 connected to the pluggable port 20 to which the optical module 40 is attached (step ST30).

[0086] [First Modification] FIG. 7 is a block diagram showing another example of the internal configuration of the optical transceiver 40. In FIG. The signal processing unit 45 of the optical transceiver 40 in Figure 7 further includes the following functional units as additional parts compared to the optical transceiver 40 in Figure 2. The following units 56, 58, and 60 are arranged on the line concentration side of the signal conversion circuit 51 in the signal processing unit 45.

[0087] 1) Upstream frame receiver 56 2) Downstream frame receiving unit 58 3) Flow control unit 60 It is not necessary to have both or either of the frame receiving units 56 and 58. For example, if the frame receiving unit 58 is not present, the flow control unit 60 monitors the availability of the transmission buffer 71 of the signal conversion circuit 51.

[0088] In the concentrator 2 of the first modified example, the flow control unit 60 executes a process of substantially narrowing the communication band depending on the operating state of the signal conversion circuit 51. Specifically, when a predetermined amount of frames are accumulated in the transmission buffer 71 of the signal conversion circuit 51 during a burst, the flow control unit 60 generates a flow control frame and inserts it between the upstream frames.

[0089] The flow control frame is a control frame that instructs the upstream device, the concentrator 2, to temporarily stop sending downstream frames. When the flow control unit of the concentrator 2 receives the flow control frame, it temporarily suspends transmission in accordance with the instruction.

[0090] 7, the flow control unit 60 transmits a control frame to the concentrator 2, which is the upper device, to temporarily stop downstream transmission, so there is no need to implement a bandwidth control function such as a shaper function in the concentrator 2. This has the advantage of reducing the manufacturing cost of the concentrator 2.

[0091] [Second Modification] FIG. 8 is a block diagram showing another example of the internal configuration of the signal conversion circuit 51. In FIG. The signal conversion circuit 51 in Figure 8 differs from the signal conversion circuit 51 in Figure 3 in that the number of types n of switchable operating modes is "3" and an upstream rate switching unit 63 and a downstream rate switching unit 73 are adopted that can execute three types of operating modes with 10G as the first rate.

[0092] That is, the signal conversion circuit 51 in FIG. 8 is a circuit in which the transmission rate (first rate) on the concentrator 2 side in the pluggable port 20 is 10G, 1G is adopted as the second rate, and 100M is adopted as the third rate.

[0093] The upstream rate switching unit 63 has a one-input, three-output selector 63A and a three-input, one-output selector 63B. The upstream rate switching unit 63 has a 10G receiving circuit 63C interposed between terminals a of selectors 63A and 63B, a serially connected 1G receiving circuit 63D and a 1G / 10G conversion circuit 63E interposed between terminals b of selectors 63A and 63B, and a serially connected 100M receiving circuit 63F and a 100M / 10G conversion circuit 63G interposed between selectors 63A and 63B.

[0094] The downstream rate switching unit 73 has a 1-input, 3-output selector 73A and a 3-input, 1-output selector 73B. The downstream rate switching unit 73 includes a 10G transmission circuit 73C interposed between terminals a of the selectors 72A and 72B, a serially connected 10G / 1G conversion circuit 73E and a 1G transmission circuit 73D interposed between terminals b of the selectors 73A and 73B, and a serially connected 10G / 100M conversion circuit 73G and a 100M transmission circuit 73F interposed between terminals c of the selectors 73A and 73B.

[0095] By adopting the second modified signal conversion circuit 51 shown in Figure 8, when the first rate on the concentrator 2 side is 10G, it is possible to manufacture an optical transceiver 40 that can support three types of transmission rates: the first rate (10G), a second rate (1G) that is slower than that, and a third rate (100M) that is even slower than that.

[0096] In the second modified example, the signal identifying unit 53 may determine the transmission rate of the optical signal using a determination logic including the following procedure, for example. Step 1: Determine whether the upstream frame is a 100M code. Step 2: If the result of the determination in step 1 is not 100M, it is further determined whether it is a 1G code (8B / 10B). Step 3: If the result of the determination in step 2 is negative, determine it as 10G.

[0097] [Other Modifications] The embodiments disclosed herein are illustrative in all respects and are not restrictive. The scope of the present invention is not limited to the above-described embodiments, but includes all modifications within the scope of equivalents to the configurations described in the claims.

[0098] In the above-described embodiment (including the modified examples), a signal conversion circuit 51 (FIG. 3) in which the number of switchable operating mode types n is 2 and a signal conversion circuit 51 (FIG. 8) in which the number of types n is 3 are exemplified, but the value of the number of types n may be 4 or more.

[0099] In the above-described embodiment (including the modified examples), the concentrator 2 is exemplified as a type of upper-level device that is a communication device on the upper side of the opposing device 4, but the upper-level device may also be a communication device such as a media converter having a pluggable port 20 for optical communication. [Explanation of symbols]

[0100] 1. Communication Systems 2. Concentrator (host device) 3. Optical Fiber 4 Opposite device 20 pluggable ports 21. Cabinet 22 L2 Switch 23 Management and Control Unit 24 Switch section 25A flow control section 25B Flow control section 26A Frame transmitter 26B Frame transmitter 27A Frame receiver 27B Frame receiver 28 Bandwidth setting section 30 Optical Transceiver (Single Rate Type) 40 Optical transceiver (multi-rate type) 40A Optical Transceiver (Multi-rate Type: 1st Mode) 40B Optical Transceiver (Multi-rate Type: 2nd Mode) 41 Case 42 Optical Connector (CNo) 43 Optical transmitter / receiver 44 Transmission Processing Unit (AFE) 45 Signal Processing Section 46 Electrical Connector (CNe) 47 Laser Diode 48 photodiodes 49 Laser Driver 50 Post-amp 51 Signal conversion circuit 52 Operation mode determination unit 53 Signal Identification Unit 54 SerDes section 55 SerDes section 56 Frame receiver 58 Frame receiver 60 Flow control section 61 receive buffer 62 Uplink rate switching unit 62A Selector 62B Selector 62C 1G receiving circuit 62D 100M receiving circuit 62E 100M / 1G conversion circuit 63 Uplink rate switching unit 63A Selector 63B Selector 63C 10G receiving circuit 63D 1G receiving circuit 63E 1G / 10G conversion circuit 63F 100M receiving circuit 63G 100M / 10G conversion circuit 71 Send Buffer 72 Downstream rate switching unit 72A Selector 72B Selector 72C 1G transmitter circuit 72D 100M transmitter circuit 72E 1G / 100M conversion circuit 73 Downstream rate switching unit 73A Selector 73B Selector 73C 10G transmitter circuit 73D 1G transmitter circuit 73E 10G / 1G conversion circuit 73F 100M transmitter circuit 73G 10G / 100M conversion circuit

Claims

1. An optical connector that is connected to a counterpart device in a one-to-one correspondence by a single optical fiber; an optical transceiver that converts optical signals into electrical signals and vice versa; a transmission processing unit that excites an optical signal in the optical transceiver and amplifies an electrical signal input from the optical transceiver; a signal processing unit that outputs an upstream frame input from the transmission processing unit to a higher-level device side and outputs a downstream frame input from the higher-level device side to the transmission processing unit, When the transmission rate on the upper device side is a first rate, and one or more transmission rates lower than the first rate are the i-th rate (i=a natural number from 2 to n), The signal processing unit An optical transceiver having a signal conversion circuit that includes the following first mode and one or more i-th modes as switchable operation mode types: First mode: An operation mode in which upstream frames at the first rate are output without converting the transmission rate, and downstream frames at the first rate are output without converting the transmission rate. i-th mode: An operation mode in which upstream frames at the i-th rate are converted to the first rate and output, and downstream frames at the first rate are converted to the i-th rate and output.

2. The signal processing unit further a signal identification unit that identifies the coding method of an upstream frame input from the transmission processing unit; 2. The optical transceiver according to claim 1, further comprising: an operation mode determination unit that determines a type of the operation mode in accordance with a result of identification by the signal identification unit, and instructs the signal conversion circuit to switch to the determined type.

3. The signal processing unit further 3. The optical transceiver according to claim 2, further comprising a flow control unit that, when the determined type is the i mode, transmits a control frame to the upper device to temporarily stop the upper device from transmitting downstream frames.

4. The operation mode determination unit 4. The optical transceiver according to claim 2, wherein, on condition that the type of operation mode has been determined, the optical transceiver transmits to the host device a control signal indicating that the optical transceiver is attached to the host device.

5. the value of n is 2; the first rate is 1G; 5. The optical transceiver according to claim 1, wherein the second rate is 100M.

6. the value of n is 3; the first rate is 10G; the second rate is 1G; 5. The optical transceiver according to claim 1, wherein the third rate is 100M.

7. a host device having a pluggable port; one or more optical transceivers connected to the pluggable port; an opposing device connected to the optical transceiver in a one-to-one correspondence with the optical transceiver by a single optical fiber; When the transmission rate on the upper device side is a first rate, and one or more transmission rates lower than the first rate are the i-th rate (i=a natural number from 2 to n), A communication system, wherein the types of operation modes that can be switched by the optical transceiver include a first mode and one or more i-th modes as follows: First mode: An operation mode in which upstream frames at the first rate are output without converting the transmission rate, and downstream frames at the first rate are output without converting the transmission rate. i-th mode: An operation mode in which upstream frames at the i-th rate are converted to the first rate and output, and downstream frames at the first rate are converted to the i-th rate and output.

8. A bandwidth control method executed in the communication system according to claim 7, determining the type of the upstream frame according to a result of identifying a transmission rate of the upstream frame received from the optical transceiver; the optical transceiver notifying the host device of the determined type; a step in which, when the notified type is the i-th mode, the upper device limits the communication bandwidth related to the pluggable port to which the optical transceiver is attached to an equivalent to the i-th rate.

9. A bandwidth control method executed in the communication system according to claim 7, determining the type of the upstream frame according to a result of identifying a transmission rate of the upstream frame received from the optical transceiver; a step of the optical transceiver transmitting a control frame to the upper device to temporarily stop the upper device from transmitting downstream frames.

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