Optical transceiver and method for frame synchronization of supervisory control signals for optical transceiver

Abstract

To enable synchronization with a plurality of kinds of frames included in a supervisory control signal superposed on an optical signal.SOLUTION: An optical transceiver comprises: an optical transmission unit for transmitting an optical transmission signal on which a supervisory control signal is superposed; an optical reception unit for extracting a supervisory control signal from an optical reception signal; and a processing unit for generating a bit stream from the supervisory control signal and reproducing supervisory control data from the bit stream. The supervisory control signal includes a first frame having a first header part and a second frame having a second header part in a time division manner. When a first byte sequence generated from the bit stream is matched with the first header part, the processing unit generates the supervisory control data by processing the first byte sequence and a byte sequence continued to the first byte sequence as the first frame, and when the first byte sequence is different from the first header part and a second byte sequence generated from the bit stream is matched with the second header part, generates the supervisory control data by processing the second byte sequence and a byte sequence continued to the second byte sequence as the second frame.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The present disclosure relates to an optical transceiver and a frame synchronization method for a supervisory control signal of the optical transceiver. [Background technology]

[0002] For example, an optical transceiver extracts supervisory control data from a low-speed signal superimposed on a received high-speed optical signal. The extracted supervisory control data is used for supervisory control of the optical transceiver and the optical network. For supervisory control, the optical transceiver also superimposes the low-speed supervisory control data onto a high-speed optical signal and transmits it (see, for example, Patent Documents 1 and 2).

[0003] For example, a frame synchronization device determines in parallel whether the input data and the synchronization pattern match consecutively for a period of the frame length for multiple matching timings based on the timings at which the input data and the synchronization pattern match, and then performs frame synchronization of the input data based on the determination results (see, for example, Patent Document 3). [Prior art documents] [Patent documents]

[0004] [Patent Document 1] Special Publication No. 2018-520561 [Patent Document 2] Special Publication No. 2018-514982 [Patent Document 3] Japanese Patent Application Publication No. 2016-072848 Summary of the Invention [Problem to be solved by the invention]

[0005] For example, the frame length (frame size) of the HTMC (Head to Tail Message Channel) frame of ITU-T (International Telecommunication Union Telecommunication Standardization Sector) Recommendation G.698.4 is 6 bytes (48 bits). In an HTMC frame, the data body (message) accounts for 50% of the frame length, and the size of the data body is 3 bytes (24 bits). The portion of the frame that stores the data body is also called the payload. For example, when transmitting large amounts of monitoring data between optical transceivers, it is preferable that the ratio of the payload size to the frame size is large in order to improve the transmission efficiency of the monitoring data.

[0006] For example, in the SONET (Synchronous Optical Network) / SDH (Synchronous Digital Hierarchy) standard established by the ITU-T, a frame structure consisting of multiple rows and multiple columns has a fixed frame length (number of columns) according to the transmission speed, and the ratio of the payload section, which stores the payload, to the frame length is greater than in the HTMC frame. Furthermore, a header section containing a synchronization pattern for frame synchronization is provided at the beginning of the frame structure, and frame synchronization is achieved by detecting the synchronization pattern in the header section.

[0007] On the other hand, the larger the size of the payload section, the more likely it is that the payload section will contain the same pattern as the synchronization pattern in the header section, increasing the possibility of false detection of the header section. Therefore, by scrambling the payload data so that the payload section does not contain the synchronization pattern, false detection of the header section can be avoided.

[0008] However, when scrambling payload data, the scrambling process must be performed on the transmitting side and the descrambling process must be performed on the receiving side. For example, processors such as MCUs (Micro Control Units) installed in optical transceivers are smaller in size than processors installed in servers, etc. This makes it difficult to implement hardware that performs scrambling and descrambling processes in the MCUs installed in optical transceivers. Furthermore, if the MCUs installed in optical transceivers are made to execute scrambling and descrambling programs, there is a risk that other existing processes will not be able to be executed at the desired timing.

[0009] In addition, optical transceivers are sometimes required to transmit and receive supervisory control data using multiple types of frames with different frame structures. When receiving multiple types of frames, it is necessary to properly synchronize with each frame and extract the data stored in the payload of each frame.

[0010] Therefore, an object of the present disclosure is to enable synchronization with multiple types of frames contained in a supervisory control signal superimposed on an optical signal. [Means for solving the problem]

[0011] According to one aspect of this embodiment, an optical transceiver includes an optical transmitter that transmits an optical transmission signal on which a supervisory control signal is superimposed, an optical receiver that receives an optical reception signal on which the supervisory control signal is superimposed and extracts the supervisory control signal from the optical reception signal, and a processor that generates a bit string from the supervisory control signal and recovers supervisory control data from the bit string, wherein the supervisory control signal includes, in time division fashion, a first frame having a first header portion at its head and a second frame having a second header portion at its head that is different from the first header portion, and the processor generating a first byte sequence having the same length as the first header portion from the bit sequence, and when the first byte sequence matches the first header portion, processing the first byte sequence and a byte sequence following the first byte sequence as the first frame to generate the supervisory control data, and when the first byte sequence differs from the first header portion, generating a second byte sequence having the same length as the second header portion, and when the second byte sequence matches the second header portion, processing the second byte sequence and a byte sequence following the second byte sequence as the second frame to generate the supervisory control data a length of the second header portion is equal to a length of the first header portion, and the processing unit uses the first byte sequence as the second byte sequence when the first byte sequence is different from the first header portion; . [Effects of the Invention]

[0012] According to the present disclosure, it is possible to synchronize with multiple types of frames included in a supervisory control signal superimposed on an optical signal. [Brief explanation of the drawings]

[0013] [Figure 1] FIG. 1 is a block diagram illustrating an example of a configuration of an optical transceiver according to an embodiment. [Figure 2] FIG. 2 is an explanatory diagram showing an example of a format of a frame including supervisory control data transmitted between the optical transceivers of FIG. [Figure 3] FIG. 3 is an explanatory diagram illustrating an example of a storage area allocated to the RAM of FIG. [Figure 4] FIG. 4 is a flowchart illustrating an example of a transmission operation of the first frame or the second frame by the optical transceiver of FIG. [Figure 5]FIG. 5 is a flowchart illustrating an example of a receiving operation of the first frame or the second frame by the optical transceiver of FIG. [Figure 6] FIG. 6 is a flow chart showing a continuation of the receiving operation of FIG. [Figure 7] FIG. 7 is an explanatory diagram illustrating an example of a transmission and reception operation of a first frame including supervisory control data between the optical transceivers of FIG. DETAILED DESCRIPTION OF THE INVENTION

[0014] [Description of the embodiments of the present disclosure] First, embodiments of the present disclosure will be listed and described.

[0015] [1] An optical transceiver according to one aspect of the present disclosure includes an optical transmitter that transmits an optical transmission signal on which a supervisory control signal is superimposed, an optical receiver that receives an optical reception signal on which the supervisory control signal is superimposed and extracts the supervisory control signal from the optical reception signal, and a processor that generates a bit string from the supervisory control signal and recovers supervisory control data from the bit string, wherein the supervisory control signal includes, in time division fashion, a first frame having a first header section at its head and a second frame having a second header section at its head that is different from the first header section, and the processor A first byte sequence having the same length as the first header portion is generated from the bit sequence, and when the first byte sequence matches the first header portion, the first byte sequence and the byte sequence following the first byte sequence are processed as the first frame to generate the monitoring control data, and when the first byte sequence differs from the first header portion, a second byte sequence having the same length as the second header portion is generated, and when the second byte sequence matches the second header portion, the second byte sequence and the byte sequence following the second byte sequence are processed as the second frame to generate the monitoring control data.

[0016] In this optical transceiver, the processing unit sequentially detects whether a synchronization pattern of the first or second header portion is included in a bit string generated from a supervisory control signal superimposed on an optical signal and transmitted / received. This prevents the optical transceiver from erroneously detecting the first or second frame, even when different types of frames are superimposed on the optical signal and transmitted / received between optical transceivers, thereby preventing malfunction of the optical transceiver. As a result, the reliability of the optical transceiver and the communication system in which the optical transceiver is installed can be improved.

[0017] [2] In the above [1], when the second byte sequence differs from the second header portion, the processing unit may shift the bit sequence by one bit to generate a new first byte sequence. In this case, the processing unit can reliably detect the first header portion or the second header portion from the new bit sequence by comparing new first byte sequences sequentially generated by shifting the bit sequence by one bit at a time with the synchronization pattern of the first header portion or the second header portion, respectively. The processing unit can then reliably acquire the first frame based on the detection of the first header portion, and the second frame based on the detection of the second header portion.

[0018] [3] In the above [1] or [2], the length of the second header section may be equal to the length of the first header section. In this case, when the first byte sequence is different from the first header section, the first byte sequence may be used as the second byte sequence. This allows the processing unit to detect the synchronization pattern of the first header section or the second header section using byte sequences of a common length as the first byte sequence and the second byte sequence, and process the first frame or the second frame. As a result, part of the detection process for the first frame and the second frame can be made common, and the acquisition process for the first frame and the second frame can be simplified compared to detecting frames with header sections of different lengths.

[0019] [4] In any one of [1] to [3], the first frame may include the first header section, a frame number section, and a first information storage section, and the second frame may include the second header section and a second information storage section. This allows the processing unit to selectively use the first frame or the second frame depending on the type or amount of supervisory control data to be transmitted to the optical transceiver of the communication partner. For example, if the amount of supervisory control data is greater than a predetermined amount, the processing unit uses the first frame (or the second frame) including the first information storage section (or the second information storage section) capable of storing supervisory control data. This allows the processing unit to minimize the size of the bit string including the supervisory control data to be superimposed on the optical transmission signal. Alternatively, the first frame FRM1 and the second frame FRM2 may be used depending on the configuration or purpose of the supervisory control data. This allows the optical transceiver 100 to perform more sophisticated supervisory control by combining two different supervisory control methods.

[0020] [5] A frame synchronization method for a supervisory control signal of an optical transceiver according to another aspect of the present disclosure includes a step of receiving an optical reception signal on which a supervisory control signal is superimposed, and extracting the supervisory control signal from the optical reception signal; a step of generating a bit string from the supervisory control signal and generating a first byte string from the bit string, the first byte string having the same length as the first header string, when the first byte string matches the first header string, to generate supervisory control data; a step of generating a second byte string having the same length as the second header string when the first byte string is different from the first header string; and a step of generating the supervisory control data by processing the second byte string and the byte string following the second byte string as the second frame when the second byte string matches the second header string.

[0021] In this method for frame synchronization of a supervisory control signal for an optical transceiver, the optical transceiver sequentially detects whether a synchronization pattern in the first or second header section is included in a bit string generated from the supervisory control signal superimposed on an optical signal that is transmitted and received. This prevents the optical transceiver from erroneously detecting the first or second frame, even when different types of frames are superimposed on the optical signal and transmitted between optical transceivers, thereby preventing malfunction of the optical transceiver. This improves the reliability of the optical transceiver and the communication system in which the optical transceiver is installed.

[0022] [6] In the above [5], the method may further include, when the second byte sequence differs from the second header portion, shifting the bit sequence by one bit to generate a new first byte sequence. In this case, the optical transceiver can reliably detect the synchronization pattern of the first header portion or the second header portion from the new bit sequence by shifting the bit sequence by one bit and comparing the new first byte sequences sequentially generated with the first header portion or the second header portion. The optical transceiver can then reliably acquire the first frame based on the detection of the first header portion, and the second frame based on the detection of the second header portion.

[0023] [7] In the above [5] or [6], the length of the second header portion may be equal to the length of the first header portion. In this case, when the first byte sequence is different from the first header portion, the first byte sequence may be used as the second byte sequence. This allows the optical transceiver to detect the first header portion or the second header portion using byte sequences of a common length as the first byte sequence and the second byte sequence, and process the first frame or the second frame. As a result, part of the detection process for the first frame and the second frame can be made common, and the acquisition process for the first frame and the second frame can be simplified compared to detecting frames with header portions of different lengths.

[0024] [8] In any of [5] to [7] above, the first frame may include the first header section, a frame number section, and a first information storage section, and the second frame may include the second header section and a second information storage section. This allows the optical transceiver to selectively use the first frame or the second frame depending on the type or amount of supervisory control data to be transmitted to the other optical transceiver. For example, if the amount of supervisory control data is large, the optical transceiver uses the first frame (or the second frame) including the first information storage section (or the second information storage section) capable of storing supervisory control data. This allows the optical transceiver to minimize the size of the bit string including the supervisory control data to be superimposed on the optical transmission signal. Alternatively, the first frame FRM1 and the second frame FRM2 may be used depending on the configuration or purpose of the supervisory control data. This allows the optical transceiver 100 to perform more sophisticated supervisory control by combining two different supervisory control methods.

[0025] [Details of the embodiments of the present disclosure] Specific examples of optical transceivers according to the present disclosure will be described below with reference to the drawings. Note that the present embodiment is not limited to the following description. In the following description, the signal lines through which information such as signals is transmitted will be designated by the same reference numerals as the signal names. Unless otherwise specified, arrowheaded lines in block diagrams indicate signal lines, optical cables, or information transmission paths. Furthermore, signal lines shown as single lines in the diagrams may be multi-bit.

[0026] [One embodiment] [Overall configuration of optical transceiver] FIG. 1 is a block diagram illustrating an example of the configuration of an optical transceiver according to an embodiment. For example, in FIG. 1, two optical transceivers 100 connected to each other via a two-core optical cable (optical fiber) transmit and receive optical signals on which low-speed modulated signals are superimposed. Each optical transceiver 100 can transmit and receive supervisory control data via the low-speed modulated signals. Since the optical transceivers 100 have the same configuration, the following description will focus on the optical transceiver 100 on the left side of FIG. 1.

[0027] The optical transceiver 100 includes, for example, an MCU (Micro Control Unit) 10, a transceiver IC (Integrated Circuit) 20, a bias supply unit 30, a low-pass filter (LPF) 40, a TOSA (Transmitter Optical Sub-Assembly) 50, and a ROSA (Receiver Optical Sub-Assembly) 60. For example, the optical transceiver 100 is detachably mounted in an optical transmission device (not shown) that transmits and receives digital signals. The bias supply unit 30 and the TOSA 50 are examples of an optical transmitter. The ROSA 60 and the low-pass filter 40 are examples of an optical receiver.

[0028] When transmitting an optical signal through an optical fiber, the side that transmits the optical signal is called the transmitting end, and the side that receives the optical signal transmitted from the transmitting end is called the receiving end. The optical transceiver 100 at the transmitting end converts the transmit data signal (digital electrical signal) received from the optical transmission device at the transmitting end into an optical signal and transmits the converted optical signal via an optical cable to the optical transceiver 100 attached to the optical transmission device at the receiving end. The optical transceiver 100 at the receiving end converts the optical signal received from the optical transceiver 100 at the transmitting end via the optical cable into a receive data signal (digital electrical signal) and outputs the converted receive data signal to the optical transmission device at the receiving end. Note that the distinction between the transmitting end and the receiving end here is for convenience of explanation; because optical signals are transmitted and received in both directions, the optical transceiver 100 that is referred to as the transmitting end for transmission is referred to as the receiving end for reception.

[0029] Furthermore, the optical transceiver 100 superimposes a low-speed modulated signal containing supervisory control data onto an optical signal and transmits the superimposed signal to another optical transceiver 100 connected via an optical cable. For example, the optical transceiver 100 transmits Manchester-encoded supervisory control data and receives Manchester-encoded supervisory control data from another optical transceiver 100. The low-speed modulated signal containing supervisory control data is an example of a supervisory control signal.

[0030] Although not particularly limited, the monitoring and control data may include, for example, monitor values measured by the optical transceiver 100 (at least one of the temperature of internal components, power supply voltage, laser bias current, optical transmission power, and optical reception power). The monitoring and control data may also include unique information that can identify the optical transceiver 100, instructions to change the wavelength (or frequency) of the optical signal, instructions to change the optical output power, etc. For example, the unique information that can identify the optical transceiver 100 may include the serial number (manufacturing number) and model number of the optical transceiver 100.

[0031] The MCU 10 includes, for example, an I 2 The MCU 10 includes various communication interfaces 12 such as an Inter-Integrated Circuit (C) interface, peripheral functions such as a DMAC 14 (Direct Memory Access Controller), and a Random Access Memory (RAM) 16. The MCU 10 also includes a Read Only Memory (ROM) (not shown) in which various programs executed by the MCU 10 are stored. The ROM may be, for example, a flash memory. The MCU 10 controls the operation of the optical transceiver 100 and has the function of processing supervisory control data. The MCU 10 may be, for example, a microcomputer or a logic device such as a Complex Programmable Logic Device (CPLD) or a Field Programmable Gate Array (FPGA). In the MCU 10, the functional unit that processes supervisory control data is an example of a processing unit.

[0032] For example, the MCU10 2 The MCU 10 receives supervisory control data from an optical transmission device via the C bus and generates a frame containing the received supervisory control data. The supervisory control data is stored, for example, in the payload section of the frame. The MCU 10 converts (encodes) a bit string corresponding to the generated frame into a Manchester code and outputs the converted Manchester code to the bias supply unit 30. For example, if the frame size is 6 bytes, the length of the bit string is 48 bits. In other words, the bit string is data consisting of 48 consecutive binary "0"s or "1"s.

[0033] The MCU 10 also receives, via the ROSA 60 and the low-pass filter 40, a low-speed modulated signal superimposed on an optical signal transmitted from another optical transceiver 100 via an optical cable. The low-pass filter 40 extracts the low-speed modulated signal from the optical signal received from the other optical transceiver 100 and outputs it to the MCU 10 as a Manchester-encoded low-speed received signal. The MCU 10 converts (decodes) the received Manchester-encoded low-speed received signal into a bit string. The converted bit string is processed by the MCU 10, frames are detected from the bit string, and supervisory control data is generated.

[0034] The MCU 10 extracts frames from the converted bit string by frame synchronization, and extracts supervisory control data from the extracted frames. The MCU 10 then stores the extracted supervisory control data in a format such as I 2 The MCU 10 outputs the low-speed modulated signals to the optical transmission device via the C bus. For example, the MCU 10 has a Manchester code encoder and decoder. Note that the code used for the low-speed modulated signals transmitted and received between the optical transceivers 100 is not limited to Manchester code, and other codes may be used.

[0035] The transceiver IC 20 generates a digital signal, for example, an NRZ (Non Return to Zero) signal, based on a transmission data signal received from an optical transmission device, and outputs the generated digital signal to the TOSA 50. The transceiver IC 20 may be, for example, a CDR (Clock Data Recovery) IC, which may waveform-shape the transmission data signal and output the resulting digital signal to the TOSA 50. Alternatively, the transceiver IC may be a digital signal processing IC, which may digitally process the transmission data signal and output the resulting digital signal to the TOSA 50.

[0036] The transceiver IC 20 also receives, from the ROSA 60, digital signals such as NRZ signals converted from optical signals received from another optical transceiver 100 connected via an optical cable. The transceiver IC 20 converts the received digital signals into received data signals (digital signals) and outputs the converted received data signals to the optical transmission device. For example, a CDR-IC may output a signal obtained by waveform-shaping the received digital signal as the received data signal. Alternatively, the transceiver IC may be a digital signal processing IC, which may, for example, digitally process the received digital signal and output the processed signal as the received data signal.

[0037] The bias supply unit 30 amplitude-modulates the bias current that drives a laser diode (not shown) mounted in the TOSA 50 in accordance with, for example, the Manchester code, and supplies the amplitude-modulated bias current to the TOSA 50. For example, when the Manchester code is "0," the bias current is decreased, and when the Manchester code is "1," the bias current is increased. For example, the ratio of the magnitude of the increase or decrease in the bias current based on the Manchester code to the magnitude of the bias current without amplitude modulation (amplitude modulation rate) is set to approximately several percent. The TOSA 50 converts an electrical signal into an optical signal using the bias current amplitude-modulated by the bias supply unit 30, thereby superimposing a low-speed modulated signal containing Manchester-encoded supervisory control data onto an optical signal. The signal speed of the low-speed modulated signal is not particularly limited, but is, for example, 50 Kbit / s. The speed of the high-speed optical signal is, for example, 10 Gbit / s or higher.

[0038] The laser diode of the TOSA 50 converts an electrical signal, such as an NRZ signal, received from the transceiver IC 20 into an optical signal. For example, when the electrical signal is an NRZ signal, the laser diode reduces the signal strength (optical power) of the optical signal output when the NRZ signal is "0" and increases the signal strength (optical power) of the optical signal output when the NRZ signal is "1." At this time, a low-speed modulation signal is superimposed on the high-speed optical signal by using a bias current amplitude-modulated based on the Manchester code described above as the bias current for the laser diode. The amplitude of the low-speed modulation signal is, for example, several percent of the amplitude of the high-speed optical signal. The laser diode then outputs the optical signal with the superimposed low-speed modulation signal as an optical transmission signal to another optical transceiver 100 via an optical cable. Note that the TOSA 50 may also include a laser diode that outputs continuous wave (CW) light and an optical modulator to which the CW light is input, and the optical signal may be generated from the CW light by driving the optical modulator with an electrical signal.

[0039] The ROSA 60 receives an optical signal superimposed with a low-speed modulation signal from another optical transceiver 100 via an optical cable as an optical reception signal. The ROSA 60 converts the optical reception signal into a current signal and amplifies the converted current signal to convert it into a voltage signal (digital signal). For example, the ROSA 60 includes a photodetector and a transimpedance amplifier. The photodetector converts the optical signal into a current signal, and the transimpedance amplifier amplifies the current signal and converts it into a voltage signal. The photodetector is, for example, a photodiode. The ROSA 60 then outputs the converted voltage signal to the transceiver IC 20 and the low-pass filter 40.

[0040] The low-pass filter 40 extracts the low-speed received signal superimposed on the optical received signal by blocking the high-frequency components of the voltage signal received from the ROSA 60. The extracted low-speed received signal is a Manchester-encoded signal containing frame data (bit strings) including supervisory control data. The low-pass filter 40 outputs the extracted low-speed received signal to the MCU 10. The MCU 10 decodes the Manchester-encoded low-speed received signal to generate a bit string. The MCU 10 may also be provided with a digital filter and use the digital filter instead of the low-pass filter 40 to extract the low-speed received signal.

[0041] A low-speed modulation signal, which is an example of a supervisory control signal, includes a first frame FRM1 and a second frame FRM2, which are described in FIG. 2, in a time-division manner. That is, the first frame FRM1 and the second frame FRM2 are transmitted from the transmitting optical transceiver 100 without overlapping with each other, and are received by the receiving optical transceiver 100 without overlapping with each other. For example, the low-speed modulation signal is transmitted by including a bit sequence corresponding to one or more first frames FRM1 followed by a bit sequence corresponding to one or more second frames FRM2. Alternatively, the low-speed modulation signal is transmitted by including a bit sequence corresponding to one or more second frames FRM2 followed by a bit sequence corresponding to one or more first frames FRM2.

[0042] [Frame format of frames containing supervisory control data] Fig. 2 is an explanatory diagram showing an example of a frame format (frame structure) of a frame including supervisory control data transmitted between the optical transceivers in Fig. 1. The frames for transmitting supervisory control data are, for example, a first frame FRM1 and a second frame FRM2.

[0043] For example, the MCU 10 may use the first frame FRM1 when the data size of the supervisory control data is larger than a predetermined amount, and may use the second frame FRM2 when the data size of the supervisory control data is smaller than the predetermined amount. This allows the MCU 10 to minimize the size of the frame including the supervisory control data to be superimposed on the optical transmission signal. Note that the first frame FRM1 and the second frame FRM2 may be used depending on the configuration or use of the supervisory control data, rather than the data size of the supervisory control data.

[0044] For example, the first frame FRM1 has a first header section HD1, a frame number section FN, and a first payload section PL1. In the following description, the first header section HD1 may also be referred to as the header, the frame number section FN as the frame number, and the first payload section PL1 as the payload. The first payload section PL1 is an example of a first information storage section. Although not particularly limited, for example, the length of the first header section HD1 is 2 bytes, the length of the frame number section FN is 1 byte, the length of the first payload section PL1 is 253 bytes, and the frame length (frame size) of the first frame FRM1 is 256 bytes. A frame having such a frame format (frame structure) will be referred to as a Long Frame.

[0045] The first header section HD1 contains a unique value for identifying the beginning of the first frame FRM1. The value to be placed in the first header section HD1 is agreed upon between the optical transceivers 100 that transmit and receive supervisory control data. For example, the first header section HD1 may contain F628h, which is a combination of the values F6h ("h" indicates that the preceding number is a hexadecimal number) and 28h used in the section overhead (SOH) of a SONET / SDH frame. In this case, the bit string in the first header section HD1 is 1111011000101000b ("b" indicates that the preceding number is a binary number).

[0046] The frame number section FN stores a frame number that is updated each time the first frame FRM1 is transmitted. For example, the frame number is updated (e.g., incremented) by "1" each time the first frame FRM1 is transmitted. Note that the frame number is not limited to a value that is updated sequentially, as long as it is a value that is updated according to a rule agreed upon between the optical transceivers 100 that transmit and receive supervisory control data.

[0047] The first payload section PL1 stores, as a message, monitoring and control data indicating at least one of the monitored values measured by the optical transceiver 100, such as the temperature of internal components, power supply voltage, laser bias current, optical transmission power, and optical reception power. The first payload section PL1 may also include a storage section for the message and a storage section for the frame number and message checksum. In this case, for example, the message may be 251 bytes and the checksum may be 2 bytes. The checksum placed in the first payload section PL1 may also be the message checksum.

[0048] As described above, the first frame FRM1 includes a first header section HD1 and a frame number section FN, which is updated each time the first frame FRM1 is transmitted. As will be described later, frame synchronization of the first frame FRM1 requires that the value in the frame number section FN match a specific value. This improves the accuracy of detecting the first frame FRM1 compared to detecting the first frame FRM1 solely based on a match in the value in the first header section HD1. This reduces false detection of the first frame FRM1, enabling more efficient transmission and reception of supervisory control data. Furthermore, the probability that a bit string formed by a combination of the header and frame number is included in the supervisory control data bit string in the payload is lower than the probability that only the header bit string is included in the supervisory control data bit string. This reduces the likelihood of the supervisory control data bit string containing the same bit string as the frame detection bit string being erroneously detected as the header and frame number. As a result, supervisory control data superimposed on an optical signal can be received without scrambling, reducing the probability of false detection.

[0049] For example, the second frame FRM2 has a second header section HD2 and a second payload section PL2. The second payload section PL2 is an example of a second information storage section. While not particularly limited, for example, the length of the second header section HD2 is 2 bytes, the same as the length of the first header section HD1, and the length of the second payload section PL2 is 4 bytes, shorter than the length of the first payload section PL1, and the frame length of the second frame FRM2 is 6 bytes. The second frame FRM2 may be an HTMC frame. A command identifying the type of data to be placed in the second payload section PL2 may be placed in the second header section HD2. That is, multiple different values may be placed in the second header section HD2. The second header section HD2 may also include a header placement section and a header checksum placement section. In this case, for example, the header may be 11 bits and the checksum may be 5 bits. The header is used to identify the beginning of a frame but is also used to identify different frames. Therefore, the value set in the first header part HD1 is different from the value set in the second header part HD2.

[0050] The second payload section PL2 may contain, for example, unique information for identifying the optical transceiver 100 itself. The second payload section PL2 may also contain supervisory control data that instructs the other optical transceiver 100 to change the wavelength (or frequency) of the optical signal or the optical output power. The second payload section PL2 may include a message storage section and a message checksum storage section. In this case, the message may be 3 bytes and the checksum may be 1 byte, for example.

[0051] In this embodiment, the MCU 10 selectively uses the first frame FRM1 or the second frame FRM2 depending on the type or amount of supervisory control data to be transmitted to the optical transceiver 100 of the communication partner. For example, the MCU 10 uses the first frame FRM1 when the data size of the supervisory control data is larger than a predetermined amount, and uses the second frame FRM2 when the data size of the supervisory control data is smaller than the predetermined amount. This allows the MCU 10 to adjust the size of the frame transmitted by the low-speed modulation signal and improve the transmission efficiency of the supervisory control data. Alternatively, the MCU 10 may selectively use the first frame FRM1 or the second frame FRM2 depending on the configuration or purpose of the supervisory control data. This allows the optical transceiver 100 to perform more sophisticated supervisory control by combining two different supervisory control methods.

[0052] [Memory area allocated to RAM] 3 is an explanatory diagram showing an example of storage areas allocated to the RAM 16 of FIG. A receive buffer unit 161, a receive header unit 162, a first supervisory control data storage unit 163, a frame error flag storage unit 164, a frame number storage unit 165, and a second supervisory control data storage unit 166 are allocated to the RAM 16 as storage areas for reception processing. A first transmit buffer unit 167 and a second transmit buffer unit 168 are also allocated to the RAM 16 as storage areas for transmission processing. At least one of the various storage areas shown in FIG. 3 may be allocated to an external memory, such as a dynamic random access memory (DRAM), that is mounted on the optical transceiver 100 and accessible by the MCU 10.

[0053] The receive buffer unit 161 sequentially stores, as a byte sequence, a bit sequence converted (decoded) from the Manchester code received via the low-pass filter 40. The receive header unit 162 has a storage area of 2 bytes, the same length as the first header unit HD1 and the second header unit HD2, and holds 2 bytes of the bit sequence held in the receive buffer unit 161. When the lengths of the first header unit HD1 and the second header unit HD2 are different, the receive header unit 162 has a storage area of the same length as either of the longer headers.

[0054] The first supervisory control data storage unit 163 stores supervisory control data included in the first payload section PL1 of the first frame FRM1. The frame error flag storage unit 164 stores information indicating whether the operation of receiving the supervisory control data of the first frame FRM1 was successful. The frame number storage unit 165 stores the frame number included in the first frame FRM1. The second supervisory control data storage unit 166 stores supervisory control data included in the second payload section PL2 of the second frame FRM2.

[0055] The first transmission buffer unit 167 holds data of a first frame FRM1 to be transmitted, and the second transmission buffer unit 168 holds data of a second frame FRM2 to be transmitted.

[0056] [Transmission operation of a frame containing supervisory control data] FIG. 4 is a flow diagram illustrating an example of the transmission operation of the first frame FRM1 or the second frame FRM2 by the optical transceiver 100 of FIG. 1. For example, the operation illustrated in FIG. 4 is realized by the MCU 10 executing a control program stored in its internal ROM. That is, FIG. 4 illustrates an example of a control method for the optical transceiver 100 and an example of a control program for the optical transceiver 100. Note that the operation illustrated in FIG. 4 may be realized by a logic circuit programmed in a programmable logic unit provided in the MCU 10. Alternatively, the operation illustrated in FIG. 4 may be performed by a logic device such as a CPLD or FPGA instead of an MCU.

[0057] The operation shown in Fig. 4 is initiated when an optical transceiver 100 transmits supervisory control data to a partner optical transceiver 100. In the operation shown in Fig. 4, checksums are placed in the second header section HD2 and second payload section PL2 of the second frame FRM2 and in the first payload section PL1 of the first frame FRM1. If a checksum is not placed, the processes of steps S110, S112, S118, S120, S124, and S126 described below are omitted. By placing a checksum, it is possible to detect whether there is an error in the received frame, thereby improving the reliability of the transmission and reception of control and supervisory data.

[0058] First, in step S102, the MCU 10 determines whether to use the first frame FRM1 or the second frame FRM2 to transmit the supervisory control data, depending on the type of supervisory control data to be transmitted. If the first frame FRM1 is to be used, the process proceeds to step S104, and if the second frame FRM2 is to be used, the process proceeds to step S116.

[0059] In step S104, the MCU 10 stores the header value (for example, F628h) in the area of the first header section HD1 allocated to the first transmission buffer section 167 of the RAM 16.

[0060] Next, in step S106, the MCU 10 increments by "1" the value of the frame number stored in the area of the frame number section FN allocated to the first transmission buffer section 167. In the RAM 16, the frame number value is handled as a hexadecimal number. Note that when the frame number is 1 byte long, the MCU 10 initializes the value of the frame number to, for example, "00h" before the first transmission of the first frame FRM1.

[0061] Next, in step S108, the MCU 10 stores the message (monitoring control data) in an area of the first payload section PL1 allocated to the first transmission buffer unit 167. Next, in step S110, the MCU 10 calculates a checksum of the message. Next, in step S112, the MCU 10 stores the checksum calculated in step S110 in an area of the first payload section PL1 allocated to the first transmission buffer unit 167.

[0062] Next, in step S114, the MCU 10 generates a bit string from the data included in the first frame FRM1 generated in the first transmission buffer unit 167, encodes the bit string into a Manchester code, and outputs the encoded bit string to the bias supply unit 30. The bias supply unit 30 supplies a bias current amplitude-modulated according to the Manchester code to the TOSA 50. The TOSA 50 converts a transmission signal, such as an NRZ signal, received from the transceiver IC 20 into an optical transmission signal using the bias current amplitude-modulated according to the Manchester code. This results in a low-speed modulation signal containing supervisory control data converted into Manchester code being superimposed on the optical transmission signal. The TOSA 50 outputs the optical transmission signal superimposed with the low-speed modulation signal to the optical cable connected to the receiving optical transceiver 100. This completes the transmission operation of the first frame FRM1. Note that, if multiple first frames FRM1 are to be transmitted consecutively, steps S104 to S114 are repeated.

[0063] If the generation timings of the first frame FRM1 and the second frame FRM2 do not overlap, the first frame FRM1 and the second frame FRM2 may be generated using a common frame buffer allocated to the RAM 16. In this case, the size of the common frame buffer is set so that it can store, for example, data of the first frame FRM1 that is longer than the length of the second frame FRM2.

[0064] On the other hand, when transmitting the second frame FRM2, in step S116, the MCU 10 stores the header value in the area of the second header section HD2 allocated to the second transmission buffer unit 168, for example. Note that, for example, if an HTMC frame is used as the second frame FRM2, the header value is set for each transmission of the frame according to multiple TOM (Type of Message) values and the TOM checksum value. Therefore, the header value may be set to a different value for each transmission. Also, as described above, the value set in the first header section HD1 of the first frame FRM1 is different from any value that may be set in the second header section HD2. Next, in step S118, the MCU 10 calculates the header checksum. Next, in step S120, the MCU 10 stores the checksum calculated in step S118 in the area of the second header section HD2 allocated to the second transmission buffer unit 168.

[0065] Next, in step S122, the MCU 10 stores the message (monitoring control data) in an area of the second payload section PL2 allocated to the second transmission buffer unit 168. Next, in step S124, the MCU 10 calculates a checksum of the message. Next, in step S126, the MCU 10 stores the checksum calculated in step S124 in an area of the second payload section PL2 allocated to the second transmission buffer unit 168. Then, data of the second frame FRM2 is generated in the second transmission buffer unit 168.

[0066] Next, in step S128, the MCU 10 generates a bit string from the data included in the second frame FRM2 generated in the second transmission buffer unit 168, encodes the bit string into a Manchester code, and outputs the encoded bit string to the bias supply unit 30. Similar to the transmission process for the first frame FRM1 described in step S114, the optical transceiver 100 outputs an optical transmission signal on which a low-speed modulation signal including information about the second frame FRM2 is superimposed to the receiving optical transceiver 100. The transmission operation for the second frame FRM2 then ends. Note that, if multiple second frames FRM2 are to be transmitted consecutively, steps S116 to S128 are repeated.

[0067] [Receiving operation of frames containing supervisory control data] 5 and 6 are flow diagrams illustrating an example of the operation of receiving the first frame FRM1 or the second frame FRM2 by the optical transceiver 100 of FIG. 1. For example, the operations illustrated in FIGS. 5 and 6 are implemented by the MCU 10 executing a control program stored in its internal ROM, similar to the operation illustrated in FIG. 4. That is, FIGS. 5 and 6 illustrate an example of a control method for the optical transceiver 100 and an example of a control program for the optical transceiver 100. The operations illustrated in FIGS. 5 and 6 may be implemented by a logic circuit programmed in a programmable logic unit provided in the MCU 10. Alternatively, the operations illustrated in FIGS. 5 and 6 may be implemented by a logic device such as a CPLD or FPGA instead of an MCU.

[0068] 5 and 6 are initiated when the optical transceiver 100 is powered on and starts receiving an optical signal. For example, if the optical transceiver 100 is a pluggable optical transceiver, when it is inserted into a cage of an optical transmission device, power is supplied to the optical transceiver 100 from the optical transmission device, and the optical transceiver 100 is powered on. Note that the data of the first frame FRM1 and the second frame FRM2 received from the source optical transceiver 100 are sequentially stored in the receive buffer unit 161 allocated in the RAM 16 before frame synchronization with either frame is performed.

[0069] First, in step S202, the MCU 10 sets the value of the frame error flag in the frame error flag holding unit 164 to the initial value "1." Next, in step S204, the MCU 10 decodes the Manchester code extracted by the low-pass filter 40 to generate a bit string. The MCU 10 converts the generated bit string into one-byte data in units of eight bits, starting from the first bit, and stores the generated one-byte data sequentially from the beginning in the receive buffer unit 161 in the order in which it was generated. In this way, a byte string is generated in the receive buffer unit 161. Of the byte string held in the receive buffer unit 161, the MCU 10 transfers two bytes that have not yet been acquired and that were received earlier to the receive header unit 162. That is, the MCU 10 generates a first byte string (two bytes) having the same length as the first header unit HD1 from the byte string held in the receive buffer unit 161.

[0070] Because the first header section HD1 and the second header section HD2 are set to the same size, the MCU 10 can start the detection process for the first frame FRM1 and the second frame FRM2 by transferring two bytes from the receive buffer section 161 to the receive header section 162. In other words, part of the frame header detection process can be standardized, which simplifies the frame synchronization process.

[0071] Next, in step S206, the MCU 10 extracts the two bytes stored in the received header section 162 and generates a first byte sequence. The MCU 10 determines whether the value of the generated first byte sequence matches a unique value set in the header of the first header section HD1 of the first frame FRM1. This corresponds to, for example, determining whether a bit sequence matches the header synchronization pattern (e.g., the above-mentioned 1111011000101000b). If the value of the first byte sequence matches the header value of the first header section HD1, the MCU 10 determines that the received frame is likely to be the first frame FRM1, and proceeds to step S218 in FIG. 6. If the value of the first byte sequence does not match the header value of the first header section HD1, the MCU 10 determines that the received frame is not the first frame FRM1, and proceeds to step S208.

[0072] If the MCU10 determines in step S206 that the first byte sequence is likely to be the first header section HD1, it performs the processes from step S218 onwards in Fig. 6 which do not include the detection process of the second header section HD2 before the detection process of the second header section HD2. Therefore, even when the bit sequence of the data stored in the first payload section PL1 of the first frame FRM1 includes the same bit sequence as the bit sequence of the second header section HD2 (the synchronization pattern of the second frame FRM2), the MCU10 can reduce erroneous detection of the second header section HD2.

[0073] In step S208, the MCU 10 extracts two bytes stored in the received header section 162 and generates a second byte sequence. The value of the second byte sequence is equal to the value of the first byte sequence. The MCU 10 then checks the checksum to determine whether the value of the generated second byte sequence matches the header value of the second header section HD2 of the second frame FRM2. If the header value of the second header section HD2 can take multiple different values, as in an HTMC frame, the MCU 10 determines whether the header value of the second header section HD2 matches any of the multiple different values. If the value of the second byte sequence matches the header value of the second header section HD2 and the checksum is correct, the MCU 10 determines whether the received frame is likely to be the second frame FRM2, and proceeds to step S212. This corresponds to, for example, checking whether the bit sequence matches the header synchronization pattern (e.g., in the case of an HTMC frame, a 16-bit pattern consisting of 11 bits of TOM and a 5-bit TOM checksum). If the value of the second byte sequence does not match the value of the header in the second header section HD2, or if the checksum is incorrect, MCU10 transitions to step S210 to continue detecting the header of the first frame FRM1 or the second frame FRM2.

[0074] If the MCU10 determines in step S208 that the second byte sequence is likely to be the second header section HD2, it performs the processes from step S212 onwards, which do not include the process of detecting the first header section HD1. Therefore, even when the bit sequence of the data stored in the second payload section PL2 of the second frame FRM2 contains the same bit sequence as the bit sequence of the first header section HD1 (the synchronization pattern of the first frame FRM1), the MCU10 can reduce erroneous detection of the first header section HD1.

[0075] In step S210, the MCU 10 shifts the two bytes of data held in the receive buffer unit 161 that were previously transferred to the receive header unit 162 by shifting the leading bit back by one bit to generate two new bytes, transfers the newly generated two bytes to the receive header unit 162, and returns the process to step S206. When shifting the leading bit back by one bit, the last bit of the new two bytes is the leading bit of the byte next to the two bytes previously transferred. Alternatively, the new two bytes are generated by adding the next byte to the two bytes previously transferred, shifting the leading bit by one bit, and converting each 8 bits into one byte starting from the shifted leading bit. That is, the MCU 10 shifts the data in the receive header unit 162 by one bit, expelling the oldest bit from the receive header unit 162, and adding the last bit to the byte that has not yet been acquired and that was received earlier in the receive buffer unit 161. Then, the MCU 10 uses the new two bytes including the new one bit added to the reception header portion 162 to perform the process of step S206.

[0076] Steps S206, S208, and S210 correspond to, for example, storing the received bit string in a shift register, shifting it by one bit to remove the leading bit, and then searching to see if the first two bytes of the shift register match the frame synchronization pattern. Note that when the leading bit is shifted by one bit in step S210, the value of the byte string after the leading bit is shifted will be different from the value of the byte string before the leading bit is shifted. Therefore, the data held in the receive buffer unit 161 is updated according to the shift of the leading bit of the bit string, or is updated by a shift operation or the like when the data is extracted as a message, and then stored in the monitoring data holding unit.

[0077] Thus, if the two-byte data stored in the reception header section 162 is neither the first header section HD1 nor the second header section HD2, the MCU 10 shifts the leading bit of the bit string obtained by decoding the Manchester code one bit backward (toward the later reception) and generates a byte string based on the shifted leading bit. This allows the MCU 10 to reliably detect the first header section HD1 or the second header section HD2 from the byte string stored in the reception header section 162. The MCU 10 can then obtain the first frame FRM1 based on the detection of the first header section HD1 and detect the second frame FRM2 based on the detection of the second header section HD2. In other words, the optical transceiver 100 can frame synchronize with the first frame FRM1 and the second frame FRM2 transmitted by the low-speed modulation signal.

[0078] In step S212, the MCU 10 acquires, from the data held in the receive buffer unit 161, the four bytes that have not yet been acquired and that were received earlier as the message and checksum of the second payload section PL2 of the second frame FRM2. That is, the MCU 10 acquires the byte sequence following the second byte sequence. Note that it is assumed here that the data held in the receive buffer unit 161 contains values that have been converted into one-byte data for each eight bits from the beginning of the bit sequence when the value of the receive header unit 162 matches the value (synchronization pattern) of the second header section HD2 and the process reaches step S212. Next, in step S214, the MCU 10 calculates the checksum of the acquired message and determines whether it matches the checksum acquired from the receive buffer unit 161. For example, if the second frame FRM2 is an HTMC frame, the first three bytes of the four bytes of the second payload section correspond to the message, so the MCU 10 calculates the checksum for the first three bytes and compares it with the checksum value of the fourth byte.

[0079] If the checksums match, the MCU 10 has detected the second frame FRM2 and proceeds to step S216. If the checksums do not match, the MCU 10 has not detected either the first frame FRM1 or the second frame FRM2 and proceeds to step S204 to obtain the next two bytes from the receive buffer unit 161.

[0080] In step S216, the MCU 10 extracts the message stored in the second payload section PL2 of the second frame FRM2 and stores it in the second supervisory control data storage unit 166. For example, the message (supervisory control data) stored in the second supervisory control data storage unit 166 is then read by the MCU 10 as I 2The message is transmitted to the computer device via the C bus. Alternatively, it is stored in an area provided in the RAM 16 for supervisory control. The second supervisory control data storage unit 166 is overwritten with the message extracted from the newly received second frame FRM2. After this, the MCU 10 returns the process to step S204 to detect the next first frame FRM1 or second frame FRM2.

[0081] In step S218 of FIG. 6, the MCU 10 acquires one byte of data stored in the receive buffer unit 161 that has not yet been acquired and that was received earlier as the frame number section FN of the first frame FRM1, and proceeds to the process of step S220. That is, the MCU 10 acquires a byte sequence that follows the first byte sequence. Note that it is assumed here that the data stored in the receive buffer unit 161 contains values that have been converted into one-byte data in 8-bit increments from the beginning of the bit sequence that was acquired when the value of the receive header unit 162 matched the value (synchronization pattern) of the first header section HD1 and the process reached step S212. If the data of the first frame FRM1 has been received correctly, the one-byte data acquired in step S218 is expected to be, for example, a value obtained by adding "1" to the value of the frame number stored in the frame number storage unit 165.

[0082] Therefore, in step S220, the MCU 10 determines whether the 1 byte of data acquired in step S218 matches the expected value, i.e., the value obtained by adding "1" to the value of the frame number held in frame number holding unit 165. If the 1 byte of data acquired in step S218 matches the expected value, the MCU 10 executes step S226, and if the 1 byte of data does not match the expected value, the MCU 10 executes step S222.

[0083] In step S222, the MCU 10 determines whether the frame error flag stored in the frame error flag storage unit 164 is "1." A frame error flag of "1" indicates that the previous reception operation of the monitoring and control data failed or that there was no previous reception operation (i.e., the first reception operation). A frame error flag of "0" indicates that the previous reception operation of the monitoring and control data was successful.

[0084] If the frame error flag is "1", the MCU 10 proceeds to step S226; if the frame error flag is not "1", the MCU 10 proceeds to step S224. In step S224, the MCU 10 determines that the reception operation of the supervisory control data failed due to a mismatch between the one byte of data acquired in step S218 and the expected value in step S220, and sets "1" in the frame error flag holding unit. The MCU 10 then proceeds to step S204 in FIG. 5 to acquire the next two bytes. In this way, if the MCU 10 cannot detect a frame number subsequent to the frame number of the previous reception, it can determine that frame synchronization has not occurred and quickly start the next reception operation, thereby increasing the frequency of detection of supervisory control data.

[0085] In step S226, the MCU 10 acquires the 253 bytes of data held in the receive buffer unit 161 that have not yet been acquired and that were received earlier as the message and checksum of the first payload section PL1 of the first frame FRM1. Next, in step S228, the MCU 10 calculates a checksum of the frame number acquired in step S218 and the message of the first payload section PL1 acquired in step S226. The MCU 10 then determines whether the calculated checksum value matches the checksum value acquired from the receive buffer unit 161. Note that the value calculated for the message of the first payload section PL1 excluding the frame number may be used as the checksum.

[0086] If the checksums match, the MCU 10 has detected the first frame FRM1, and proceeds to step S230. If the checksums do not match, the MCU 10 has not detected the first frame FRM1, and proceeds to step S236. That is, the MCU 10 determines whether to store the acquired message of the first payload section PL1 in the first supervisory control data holding section 163 of the RAM 16, depending on whether the checksums match or not in step S228. In this way, frame synchronization is achieved for the first frame FRM1 when the value of the first header HD1, the value of the frame number, and the value of the checksum all match predetermined values. In this way, by using the checksum to determine whether the data of the acquired first payload section PL1 is supervisory control data, the accuracy of supervisory control data detection can be improved and the probability of erroneous supervisory control data detection can be reduced.

[0087] In step S230, the MCU 10 extracts the message stored in the first payload section PL1 of the first frame FRM1 and stores it in the first supervisory control data storage unit 163. The message (supervisory control data) stored in the first supervisory control data storage unit 163 is then read by the MCU 10 as I 2 The message is transmitted to the computer via the C bus, or is stored in an area provided in the RAM 16 for supervisory control. The first supervisory control data storage unit 163 is overwritten by the message extracted from the newly received first frame FRM1.

[0088] Next, in step S232, the MCU 10 retrieves the frame number stored in the frame number section FN of the first frame FRM1 and stores it in the frame number holding section 165, thereby updating the frame number held in the frame number holding section 165. That is, the MCU 10 rewrites the frame number held in the frame number holding section 165, which is the frame number to be used in the next receiving operation, with the 1-byte data acquired in step S218. Note that when rewriting the frame number holding section 165, it is also possible to add "1" to the 1-byte value acquired in step S218 in advance to set this as the expected value of the next frame number, and determine whether the value of the newly acquired frame number in step S220 matches the expected value held in the frame number holding section 165.

[0089] Next, in step S234, since the MCU 10 has successfully received the monitoring control data, it sets the frame error flag holding unit 164 to "0" and proceeds to step S204 in FIG. 5 to obtain the next two bytes.

[0090] In step S236, the MCU 10 discards the data of the first payload section PL1 acquired in step S226. Next, in step S238, the MCU 10 sets the frame error flag holding unit 164 to "1" because the operation of receiving the monitoring control data has failed, and executes step S204 to acquire the next two bytes.

[0091] [Transmission and reception of frames containing supervisory control data] FIG. 7 is an explanatory diagram showing an example of the transmission and reception operation of a first frame FRM1 containing supervisory control data between the optical transceivers 100 shown in FIG. 1. In reality, the optical transceivers 100 transmit and receive the first frame FRM1 containing Manchester-encoded supervisory control data. However, for ease of understanding, the figures shown here show values before Manchester encoding and after decoding the Manchester code. The numerical values shown in FIG. 7 are expressed in decimal. For example, the operation shown in FIG. 7 is realized by the MCU 10 executing a control program. Note that, for ease of understanding, FIG. 7 shows an example in which only the first frame FRM1 is continuously transmitted and received without the second frame FRM2 intervening.

[0092] The MCU 10 of the transmitting optical transceiver 100 sequentially transmits first frames FRM1 containing supervisory control data to the receiving optical transceiver 100 while updating the frame number value according to the operations described in steps S104 to S114 of Fig. 4. Fig. 7 shows only the frame numbers transmitted by the transmitting optical transceiver 100. The MCU 10 of the receiving optical transceiver 100 sequentially receives first frames FRM1 containing supervisory control data by performing the operations described in steps S204, S206, and S218 to S238 of Fig. 5 and Fig. 6.

[0093] 7 shows nine receive operations OP (OP1-OP9) of the first frame FRM1. The frame number storage unit 165 and frame error flag storage unit 164 of the RAM 16 of the receiving optical transceiver 100 initially store a frame number of "255" and a frame error flag of "1." The following describes the operation of the MCU 10 of the receiving optical transceiver 100. The following description is based on the assumption that the receive buffer 161 shown in FIG. 3 stores a value obtained by converting every eight bits from the beginning of the bit string into one byte of data when the value of the receive header unit 162 matches the value (synchronization pattern) of the first header unit HD1.

[0094] First, in the receive operation OP1, the MCU 10 acquires data from the receive buffer 161 until the values of the first two bytes of the received byte string (i.e., the receive header section 162) match a unique value (e.g., F628h) of the first header section HD1. When the value of the receive header section 162 matches a unique value (synchronization pattern) of the first header section HD1 (this is hereinafter referred to as detecting a synchronization pattern), the MCU 10 acquires the next byte as a frame number. Note that, here, when the first bit of the bit string is shifted back by one bit, the byte string held in the receive buffer 161 is updated to a value converted into one byte of data, with each 8 bits starting from the new first bit.

[0095] The MCU 10 determines that the frame numbers do not match because the acquired frame number (="1") is not "0", which is the frame number (="255") held in RAM 16 + 1. Note that since the frame number is a 1-byte value, for example, adding 1h to FFh results in 0h, and the carry is ignored. On the other hand, since the frame error flag is "1", the MCU 10 acquires the byte string of 253 bytes following the byte acquired as the frame number as the first payload section PL1 from the receive buffer unit 161 in accordance with the format of the first frame FRM1 in Figure 2. The circle shown in the "Acquire Payload" column indicates the execution of the payload acquisition operation.

[0096] In this way, during the first reception operation, an incorrect value or the like may be stored as the initial value of the frame number (update data) in the frame number storage unit 165. Even in this case, if the frame error flag is "1", the MCU 10 obtains a byte sequence of a predetermined length from the reception buffer unit 161 as the first payload portion PL1.

[0097] This prevents a situation in which the message stored in the first payload section PL1 cannot be acquired due to repeated mismatches between the value of the frame number acquired from the receive buffer unit 161 and the expected value calculated from the frame number (update data) stored in the frame number storage unit 165. As a result, it is possible to prevent successive failures in the receiving operation even though the correct frame number of the first frame FRM1 is received, for example, and to increase the frequency of receiving frame numbers.

[0098] The MCU 10 calculates a checksum from the acquired frame number value and the value of the byte string acquired as the message of the first payload section PL1, and compares it with the value of the byte string acquired as the checksum of the first payload section PL1. If the checksums match, the MCU 10 stores the acquired message (monitoring control data) of the first payload section PL1 in the first monitoring control data storage unit 163 of the RAM 16.

[0099] The circle in the "Data Storage" column indicates that the checksums match, and therefore the acquired message of the first payload section PL1 is stored in the first supervisory control data holding unit 163. The MCU10 stores the value of the received frame number (="1") in the frame number holding unit 165, stores "0" indicating the success of the supervisory control data receiving operation in the frame error flag holding unit 164, and ends the receiving operation OP1.

[0100] In receive operation OP2, the MCU10 determines that the frame numbers match because the frame number (="2") acquired following detection of the synchronization pattern in the first header section HD1 is the frame number (="1") held in frame number holding section 165 + 1. The MCU10 acquires a byte string of a predetermined length from receive buffer section 161, starting from the byte for which the frame number was acquired as the first payload section PL1. The MCU10 calculates a checksum from the value of the frame number for which the match was confirmed and the value of the byte string acquired as the message of first payload section PL1.

[0101] Because the calculated checksum matches the received checksum, the MCU10 stores the byte sequence acquired as the message of the acquired first payload section PL1 in the first supervisory control data holding unit 163. The MCU10 stores the value of the received frame number (="2") in the frame number holding unit 165, stores "0" indicating success of the supervisory control data receiving operation in the frame error flag holding unit 164, and ends the receiving operation OP2. The receiving operation OP3 is executed in the same way as the receiving operation OP2.

[0102] In the receiving operation OP4, the frame number "4" sent by the transmitting optical transceiver 100 is transmitted to the transmitting optical transceiver 100 as "12", for example, due to a deterioration in the communication quality of the optical cable transmitting the optical signal (due to the influence of noise, etc.).

[0103] The MCU 10 determines that the frame numbers do not match because the received frame number (="12") is not "4", which is the frame number value (="3") held in the frame number holding unit 165 + 1. Because the frame error flag held in the frame error flag holding unit 164 is "0", the MCU 10 rewrites the "0" held in the frame error flag holding unit 164 to "1", which indicates a failure of the receiving operation. In this case, the MCU 10 ends the receiving operation OP4 without storing the acquired frame number value (="12") in the frame number holding unit 165.

[0104] In the receiving operation OP5, because the previous receiving operation OP4 failed, the frame number stored in the frame number storage unit 165 was not updated. As a result, the updated frame number value output by the transmitting optical transceiver 100 and the frame number value stored in the frame number storage unit 165 are not consistent.

[0105] The MCU10 determines that the frame numbers do not match because the frame number (="5") acquired following detection of the synchronization pattern in the first header section HD1 is not "4," which is the frame number value (="3") + 1 held in the frame number holding section 165. However, as with the receiving operation OP1, the frame error flag is "1," so the MCU10 assumes that it may have detected the frame number and acquires a byte string of a predetermined length from the receive buffer section 161, starting from the byte from which the frame number was acquired as the first payload section PL1. The MCU10 then calculates a checksum from the value of the acquired frame number and the value of the byte string acquired as the message of the first payload section PL1.

[0106] In this example, the calculated checksum matches the received checksum, so the MCU 10 stores the byte sequence acquired as the message in the first payload section PL1 in the first supervisory control data storage unit 163. The MCU 10 also stores the received frame number (="5") in the frame number storage unit 165, stores "0" indicating the success of the supervisory control data receiving operation in the frame error flag storage unit 164, and ends the receiving operation OP5.

[0107] In this way, it is possible to prevent the wasteful termination of the receiving operation OP5 due to failure to acquire the received monitoring and control data even though the correct monitoring and control data has been received. Furthermore, it is possible to prevent repeated mismatches between the frame numbers sequentially updated by the transmitting optical transceiver 100 and the expected values calculated from the frame numbers stored in the frame number storage unit 165. As a result, it is possible to prevent consecutive failures in the receiving operation even though the correct frame numbers are being received. As a result, it is possible to increase the frequency of receiving frame numbers.

[0108] The receive operation OP6 is executed in the same way as the receive operation OP2. In the receive operation OP7, the MCU10 determines that the frame numbers match because the value (="7") of the frame number acquired following detection of the synchronization pattern in the first header section HD1 is the frame number value (="6") held in the frame number holding section 165 + 1. The MCU10 acquires a byte string of a predetermined length from the receive buffer section 161 following the byte from which the frame number was acquired as the first payload section PL1, and calculates a checksum from the value of the acquired frame number and the value of the byte string acquired as the message of the first payload section PL1.

[0109] In the receiving operation OP7, since the calculated checksum does not match the received checksum, the MCU10 discards the byte sequence acquired as the message in the first payload section PL1 (i.e., does not store it in the first supervisory control data holding unit 163). The MCU10 does not update the frame number held in the frame number holding unit 165, stores "1" in the frame error flag holding unit 164, indicating a failure in the supervisory control data receiving operation, and ends the receiving operation OP7.

[0110] In the receiving operation OP8, the MCU10 determines that the frame numbers do not match because the frame number value (="8") acquired following detection of the first header section HD1 synchronization pattern is not "7", which is the frame number value (="6") + 1 held in the frame number holding unit 165. Thereafter, the receiving operation OP8 is executed in the same manner as the receiving operation OP1, "8" is stored in the frame number holding unit 165, and "0", indicating the success of the receiving operation of the supervisory control data, is stored in the frame error flag holding unit 164. The receiving operation OP9 is executed in the same manner as the receiving operation OP2.

[0111] 7, the MCU 10 stores the frame number acquired following detection of the synchronization pattern in the first header section HD1 in the frame number holding unit 165, and compares the frame number acquired following detection of the synchronization pattern in the first header section HD1 in the next receiving operation with the value of the frame number held in the frame number holding unit 165, incremented by "1." However, the MCU 10 may also store the value of the frame number acquired in the receiving operation, incremented by "1," in the frame number holding unit 165 in advance as an expected value. In this case, the MCU 10 compares the frame number acquired in the next receiving operation with the frame number held in the frame number holding unit 165.

[0112] As described above, in this embodiment, the optical transceiver 100 transmits and receives an optical signal on which a low-speed modulated signal including a first frame FRM1 and a second frame FRM2, which have different formats (frame structures), is superimposed. The MCU 10 sequentially detects whether a synchronization pattern of the first header portion HD1 or the second header portion HD2 is included in a bit string generated from the low-speed modulated signal superimposed on the optical signal and transmitted and received. This allows the optical transceiver 100 to reduce false detections of the first frame FRM1 and the second frame FRM2, thereby reducing malfunctions of the optical transceiver 100. As a result, the reliability of the optical transceiver 100 and the reliability of a communication system in which the optical transceiver 100 is installed can be improved.

[0113] In a frame-synchronized reception operation of supervisory control data, if the two-byte value held in the reception header section 162 is neither the value of the first header section HD1 nor the value of the second header section HD2, the MCU 10 executes a process of shifting the generation start position (first bit) of the byte string in the bit string generated from the low-speed modulated signal backward by one bit. This allows the MCU 10 to reliably detect the first header section HD1 or the second header section HD2 from the value held in the reception header section 162. The MCU 10 can then reliably acquire the first frame FRM1 based on the detection of the first header section HD1, and can reliably detect the second frame FRM2 based on the detection of the second header section HD2.

[0114] The first header section HD1 and the second header section HD2 are set to the same length (size). Therefore, the MCU 10 can start the detection process for the first frame FRM1 and the second frame FRM2 by transferring the first two bytes generated from the first bit of the bit string from the receive buffer section 161 to the receive header section 162. In other words, compared to detecting frames with header sections of different lengths, part of the frame detection process can be made common, and the frame detection process can be simplified.

[0115] The MCU 10 can selectively use either the first frame FRM1 or the second frame FRM2 depending on the type or amount of supervisory control data to be transmitted to the optical transceiver 100 of the communication partner. For example, if the data size of the supervisory control data is large, the MCU 10 uses the first frame FRM1, and if the data size of the supervisory control data is small, the MCU 10 uses the second frame FRM2. This allows the MCU 10 to minimize the size of the bit string containing the supervisory control data to be superimposed on the optical transmission signal. The MCU 10 may also use either the first frame FRM1 or the second frame FRM2 depending on the configuration or purpose of the supervisory control data. This allows the optical transceiver 100 to perform more sophisticated supervisory control with higher functionality by combining two different supervisory control methods.

[0116] Although the embodiments of the present disclosure have been described above, the present disclosure is not limited to the above embodiments. Various changes, modifications, substitutions, additions, deletions, and combinations are possible within the scope of the claims. These changes also naturally fall within the technical scope of the present disclosure. [Explanation of symbols]

[0117] 10 MCU 12 Communication Interface 14 DMAC 16 RAM 20 Transceiver IC 30 Bias supply unit 40 Low-pass filter 50 TOSA 60 ROSA 100 Optical Transceiver 161 Receive buffer section 162 Received header section 163 First monitoring and control data storage unit 164 Frame error flag holder 165 Frame number storage section 166 Second monitoring and control data storage unit 167 First transmit buffer section 168 Second transmit buffer section FN Frame Number FRM1 First frame FRM2 Second frame HD1 First header section HD2 Second header section PL1 First Payload Section PL2 Second Payload Section

Claims

1. an optical transmitter that transmits an optical transmission signal on which a supervisory control signal is superimposed; an optical receiving unit that receives an optical reception signal on which the supervisory control signal is superimposed and extracts the supervisory control signal from the optical reception signal; a processing unit that generates a bit string from the supervisory control signal and reproduces supervisory control data from the bit string; Equipped with the supervisory control signal includes, in a time-division manner, a first frame having a first header portion at its beginning and a second frame having a second header portion at its beginning that is different from the first header portion; the processing unit generates a first byte sequence from the bit sequence, the first byte sequence having the same length as the first header portion, and when the first byte sequence matches the first header portion, processes the first byte sequence and a byte sequence following the first byte sequence as the first frame to generate the monitoring control data, and when the first byte sequence differs from the first header portion, generates a second byte sequence having the same length as the second header portion, and when the second byte sequence matches the second header portion, processes the second byte sequence and a byte sequence following the second byte sequence as the second frame to generate the monitoring control data, The length of the second header portion is equal to the length of the first header portion, the processing unit uses the first byte sequence as the second byte sequence when the first byte sequence is different from the first header portion. Optical transceiver.

2. When the second byte sequence is different from the second header portion, the processing unit shifts the bit sequence by one bit to newly generate the first byte sequence.

10. The optical transceiver of claim 1.

3. the first frame includes the first header portion, a frame number portion, and a first information storage portion, the second frame includes the second header portion and a second information storage portion; 3. The optical transceiver according to claim 1.

4. A frame synchronization method for a supervisory control signal of an optical transceiver, comprising: the supervisory control signal includes, in a time-division manner, a first frame having a first header portion at its beginning and a second frame having a second header portion at its beginning that is different from the first header portion; receiving an optical reception signal on which the supervisory control signal is superimposed, and extracting the supervisory control signal from the optical reception signal; generating a bit string from the supervisory control signal, and generating a first byte string from the bit string, the first byte string having the same length as the first header portion; a step of generating supervisory control data by processing the first byte sequence and a byte sequence following the first byte sequence as the first frame when the first byte sequence matches the first header portion; generating a second byte sequence having the same length as the second header portion when the first byte sequence is different from the first header portion; and generating the monitoring control data by processing the second byte sequence and a byte sequence following the second byte sequence as the second frame when the second byte sequence matches the second header portion, The length of the second header portion is equal to the length of the first header portion, generating the second byte sequence having the same length as the second header portion when the first byte sequence is different from the first header portion includes using the first byte sequence as the second byte sequence when the first byte sequence is different from the first header portion; Frame synchronization method.

5. further comprising the step of shifting the bit string by one bit to newly generate the first byte string when the second byte string is different from the second header portion.

5. The frame synchronization method according to claim 4.

6. the first frame includes the first header portion, a frame number portion, and a first information storage portion, the second frame includes the second header portion and a second information storage portion; 6. A frame synchronization method according to claim 4 or 5.

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