SDH optical interface adaptive rate identification method

Abstract

The application provides a kind of SDH optical interface adaptive rate identification method, the line rate equal to optical interface rate is set in optical transmitting terminal, different interface rate uses same reference clock and same data bit width, then framing and scrambling are carried out;In optical receiving terminal processing module, after cross-clock domain processing of SDH code stream data, cyclic ordering, frame header search are carried out, use byte number to judge SDH data code stream frame format with frame header search success flag bit as starting point to count byte number, then confirm corresponding line rate, so as to determine what kind of optical interface rate, the application associates mapping of optical interface rate, line rate, cross-clock processing, local clock, line clock, frame format in optical transmitting terminal and optical receiving terminal, four kinds of optical interface rate can be accurately identified at low cost by using a set of procedures, which solves the problems existing in prior art.

Description

Technical Field

[0001] The present invention relates to the field of optical synchronous digital transmission, in particular to an SDH optical interface adaptive rate identification method. Background Art

[0002] Synchronous Digital Hierarchy (SDH) has transmission and switching functions, can flexibly implement various network topologies, has good horizontal compatibility, and is widely used in backbone networks and access networks.

[0003] SDH features a unified frame structure, standard digital transmission rates, and a standardized optical path architecture. Common SDH frame formats include STM-1, STM-4, STM-16, and STM-64, corresponding to optical interface rates of 155.52 Mbit / s, 622.08 Mbit / s, 2488.32 Mbit / s, and 9953.28 Mbit / s. For SDH data streams with unknown optical interface rates, efficient identification of the optical interface rate facilitates rapid interoperability across network management systems. Existing optical interface rate identification methods rely on separate programs designed for each optical interface rate, resulting in high costs, poor compatibility, and limited flexibility. Summary of the Invention

[0004] The present invention provides an SDH optical interface adaptive rate identification method, which solves the problem of "high cost in identifying the optical interface rate of SDH code stream data" in the prior art.

[0005] The present invention solves the technical problem through the following technical solutions:

[0006] An SDH optical interface adaptive rate identification method includes an optical transmitting end processing module and an optical receiving end processing module;

[0007] At the optical transmitting end, the optical transmitting end processing module sets the reference clock, line rate and data bit width of the external optical signal according to the optical interface rate instruction, and then obtains the optical transmitting signal after framing and scrambling processing;

[0008] There is at least one optical interface rate; the reference clocks set for each optical interface rate are the same; the data bit widths set for each optical interface rate are the same; the optical receiving end processing module includes a cross-clock domain processing submodule, a frame header search submodule, and a line rate adaptation submodule; at the optical receiving end, the optical receiving end processing module performs cross-clock domain processing, frame header search, and line rate adaptation on the optical transmission signal.

[0009] Furthermore, the cross-clock domain processing submodule uses a first buffer;

[0010] For the optical transmission signal at each optical port rate, the cross-clock domain processing submodule reads and writes the data of the optical transmission signal in an asynchronous first-in-first-out manner, specifically:

[0011] Using the line clock corresponding to the line rate as a write clock signal, continuously and uninterruptedly write each SDH code stream data having a width equal to the data bit width;

[0012] After writing the valid data, using the local clock as the read clock signal, continuously and uninterruptedly read each SDH code stream data having a width equal to the data bit width to the first buffer;

[0013] The number of bits of the first buffer is the same as the data bit width; the first buffer outputs SDH code stream parallel data with the same width as the data bit width.

[0014] Furthermore, the frame header search submodule uses a second buffer and a third buffer; the number of bits of the second buffer is twice the number of bits of the data bit width; the number of bits of the third buffer is the same as the number of bits of the data bit width;

[0015] The frame header search submodule performs cyclic sorting and frame header search on the SDH code stream parallel data outputted by the first buffer each time;

[0016] The specific process of the cyclic sorting is:

[0017] For each piece of SDH code stream parallel data, the SDH code stream parallel data is stored in the low order of the second buffer, the SDH code stream parallel data is delayed by one clock cycle under the local clock, and then stored in the high order of the second buffer;

[0018] The parallel data outputted from the second buffer is sequentially shifted into the third buffer.

[0019] Furthermore, the SDH code stream parallel data entering the third buffer is continuously searched, and when 0XF6F6F6F6 is searched in the current data of the third buffer and 0X28282828 is searched in the subsequent data, a frame header search success flag is provided.

[0020] Furthermore, the bytes of the SDH code stream parallel data entering the third buffer are counted starting from the flag bit, and the line rate is determined according to the number of bytes.

[0021] Furthermore, the optical interface rate is one of 155.52 Mbit / s, 622.08 Mbit / s, 2488.32 Mbit / s and 9953.28 Mbit / s.

[0022] Furthermore, the frame formats involved in the framing are STM-1, STM-4, STM-16 and

[0023] One of the STM-64.

[0024] Furthermore, the framed signal is scrambled by a 7-level scrambler to obtain an optical transmission signal.

[0025] The advantages and effects of the present invention are:

[0026] At the optical transmitting end, a line rate equal to the optical interface rate, a corresponding reference clock and a data bit width are set according to the optical interface rate, and the four optical interface rates use the same reference clock and data bit width. At the optical receiving end, a local clock is used for cross-clock domain processing, and then a frame header search and line rate adaptation are performed. The present invention uses the same reference clock and data bit width for any optical interface rate at the optical transmitting end. Even if the optical interface rate is unknown at the optical receiving end, a cross-clock domain processing method can be uniformly used to realize the reading and writing of SDH code stream data, and then a frame header search is performed to obtain a frame header search success flag bit. The flag bit is then used as a starting bit for byte statistics, and the SDH code stream data frame format is confirmed based on the bytes, and then its optical interface rate is confirmed. The present invention can identify the four optical interface rates using one set of programs, without setting up four sets of programs to identify the four optical interface rates, thereby realizing low-cost identification of the optical interface rate of the SDH code stream data. BRIEF DESCRIPTION OF THE DRAWINGS

[0027] Figure 1 Flow chart of the method of the present invention. DETAILED DESCRIPTION

[0028] The present invention will be further described below with reference to the following examples, but the present invention is not limited to these examples.

[0029] A method for identifying an adaptive rate of an SDH optical interface includes an optical transmitting end processing module and an optical receiving end processing module; at the optical transmitting end, the optical transmitting end processing module sets the reference clock, line rate and data bit width of the external optical signal according to the optical interface rate instruction, and then obtains the optical transmission signal after framing and scrambling processing; the optical interface rate is at least one; the reference clocks set for the various optical interface rates are the same; the data bit widths set for the various optical interface rates are the same; the optical receiving end processing module includes a cross-clock domain processing submodule, a frame header search submodule and a line rate adaptation submodule; at the optical receiving end, the optical receiving end processing module performs cross-clock domain processing, frame header search and line rate adaptation on the optical transmission signal. The flow chart of the method of the present invention is as follows: Figure 1 shown.

[0030] At the optical transmitter, after receiving the optical interface rate setting instruction, the reference clock, line rate and data bit width related to the optical interface rate can be set before framing and scrambling. The specific mapping relationship is shown in Table 1:

[0031] Table 1 Mapping relationship of optical transmitter

[0032]

[0033] At the optical transmitting end, when the optical interface rate is 155.52 Mbit / s, the first reference clock is set to 311.04 Mbit / s, the first line rate is set to 622.08 Mbit / s, the first data bit width is set to 32 bits, and then the framing is performed according to the STM-1 frame format; when the optical interface rate is 622.08 Mbit / s, the second reference clock is set to 311.04 Mbit / s, the second line rate is set to 622.08 Mbit / s, the second data bit width is set to 32 bits, and then the framing is performed according to the STM-4 frame format. When the optical interface rate is 2488.32 Mbit / s, the third reference clock is set to 311.04 Mbit / s, the third line rate is set to 2488.32 Mbit / s, and the third data bit width is set to 32 bits, and then framing is performed according to the STM-16 frame format; when the optical interface rate is 9953.28 Mbit / s, the fourth reference clock is set to 311.04 Mbit / s, the fourth line rate is set to 9953.28 Mbit / s, and the fourth data bit width is set to 32 bits, and then framing is performed according to the STM-64 frame format. It can be seen from the above four optical interface rate setting methods that they use the same reference clock and data bit width, so that the cross-clock domain processing method, frame header search method, and rate adaptation method can be shared at the receiving end, saving costs in code stream processing and making the present invention more practical. Since the line rate cannot be lower than 500MHz, the present invention sets the line rate corresponding to the optical interface rate of 155.52Mbit / s to 622.08Mbit / s, and repeats the STM-1 data four times to meet the line rate requirement.

[0034] Framing is a well-known technology. A frame consists of a header and a trailer, along with numerous control signals for frame delimitation, frame synchronization, flow control, and error detection. Framing is the process of adding a header and a trailer to the front and back of a segment of data to form a frame. The present invention frames SDH code stream data using a frame format corresponding to the optical interface rate. The optical interface rate is associated with the line rate and participates in framing, providing a basis for "using a single program to identify four optical interface rates." The optical interface rate is then confirmed using the frame format at the optical transmitter, ensuring accuracy and reliability.

[0035] Scrambling is an existing technology. After the optical transmitter completes the framing, it performs NRZ (non-return-to-zero) scrambling. The scrambling is completed by a 7-level scrambler that generates a polynomial. The scrambling code generating polynomial is 1+X 6 +X 7 The scrambling sequence length is 127 bits. The scrambler code is simple, does not increase the line signal rate, has no optical power penalty, and does not require encoding. Optical path interconnection can be achieved by using only a scrambler at the optical transmitter and a descrambler of the same standard at the optical receiver.

[0036] The optical transmit signal is a 32-bit SDH data stream. Upon reaching the optical receiver, it performs cross-clock domain processing, frame header search, and line rate adaptation. Table 2 shows the mapping between the frame format, line clock, local clock, the number of bytes in the data stream for each frame format, and the corresponding optical interface rate.

[0037] Table 2 Mapping relationship of optical receiver

[0038]

[0039] The cross-clock domain processing submodule is used for cross-clock domain processing, synchronizing the SDH code stream data from the optical transmitter to the local clock domain. The cross-clock domain processing submodule uses the first buffer; for each optical transmission signal at the optical port rate, the cross-clock domain processing submodule reads and writes the data of the optical transmission signal in an asynchronous first-in-first-out (FIFO) manner, specifically:

[0040] Using the line clock corresponding to the line rate as a write clock signal, continuously and uninterruptedly write each SDH code stream data having a width equal to the data bit width;

[0041] After writing the valid data, using the local clock as the read clock signal, continuously and uninterruptedly read each SDH code stream data having a width equal to the data bit width to the first buffer;

[0042] The number of bits of the first buffer is the same as the data bit width, and the first buffer outputs SDH code stream parallel data with the same width as the data bit width.

[0043] Combining Table 1 and Table 2, it can be seen that at the optical transmitter, the line rate of the STM-1 frame format is 622.08 Mbit / s, so the line clock of the 32-bit SDH code stream data is 19.44 MHz. The line rate of the STM-4 frame format is 622.08 Mbit / s, so the line clock of the 32-bit SDH code stream data is 19.44 MHz. The line rate of the STM-16 frame format is 2488.32 Mbit / s, so the line clock of the 32-bit SDH code stream data is 77.76 MHz. The line rate of the STM-64 frame format is 9953.28 Mbit / s, so the line clock of the 32-bit SDH code stream data is 311.04 MHz. The specific steps of cross-clock domain processing are as follows: the write clock w_clk of the asynchronous FIFO is the line clock (one of 19.44MHz, 77.76MHz or 311.04MHz), the write data w_data is 32-bit wide SDH code stream parallel data, the read clock r_clk of the asynchronous FIFO is the local clock 320MHz, and the read data r_data is 32-bit wide SDH code stream parallel data; the write enable w_en of the asynchronous FIFO is always valid, so that the FIFO is always in the write state. Since the read clock r_clk of the FIFO is 320MHz, which is greater than any line clock, the FIFO will never be fully written. When valid data is stored in the FIFO, the read enable signal r_en is set high and is in a valid state. Every time a valid value is read, the read data r_data is stored in the first buffer.

[0044] The frame header search submodule uses the second buffer and the third buffer; the number of bits of the second buffer is twice the data bit width; the number of bits of the third buffer is the same as the data bit width; the frame header search submodule performs cyclic sorting and frame header search on the SDH code stream parallel data output by the first buffer each time;

[0045] The specific process of the cyclic sorting is:

[0046] For each piece of SDH code stream parallel data, the SDH code stream parallel data is stored in the low order of the second buffer, the SDH code stream parallel data is delayed by one clock cycle under the local clock, and then stored in the high order of the second buffer;

[0047] The parallel data outputted from the second buffer is sequentially shifted into the third buffer.

[0048] Specifically, for each 32-bit SDH code stream parallel data, the 32-bit SDH code stream parallel data is stored in the low order of the 64-bit second buffer, and the 32-bit SDH code stream parallel data is stored in the high order of the 64-bit second buffer after being delayed for one clock cycle under the local clock 320Mhz; the parallel data in the 64-bit second buffer is cyclically sorted, that is, the 64-bit parallel data is shifted into the 32-bit third buffer every 8 bits, shifted four times, and the sorted 32-bit wide cyclic parallel data is obtained.

[0049] Continuously searching the SDH code stream parallel data entering the third buffer, providing a frame header search success flag when 0XF6F6F6F6 is found in the current data of the third buffer and 0X28282828 is found in the subsequent data. Counting the bytes of the SDH code stream parallel data entering the third buffer using the flag as a starting point, and determining the line rate based on the byte count. The SDH code stream bytes are counted starting from the flag bit. When the frame byte count is 2430 bytes, the optical interface rate of the current SDH code stream data can be determined to be 155.520 Mbit / s. When the frame byte count is 9720 bytes, the optical interface rate of the current SDH code stream data can be determined to be 622.08 Mbit / s. When the frame byte count is 38880 bytes, the optical interface rate of the current SDH code stream data can be determined to be 2488.32 Mbit / s. When the frame byte count is 155520 bytes, the optical interface rate of the current SDH code stream data can be determined to be 9953.28 Mbit / s.

[0050] The present invention provides an optical transmitter processing module and an optical receiver processing module. In the optical transmitter processing module, four optical interface rates are set to the corresponding line rates. The four optical interface rates are set to the same reference clock and data bit width. After the settings are completed, framing and scrambling are performed. The resulting optical transmission signals contain optical interface rate information and have the same data bit width, facilitating unified processing at the optical receiver. In the optical receiver processing module, SDH code stream data is processed across clock domains before cyclic sorting and frame header search. The number of bytes is counted starting from the frame header search success flag bit, and the frame format of the SDH data code stream is determined using the byte count to further confirm the corresponding optical interface rate. The present invention associates and maps the optical interface rate, line rate, line clock, local clock, and frame format at the optical transmitter and receiver. Using a single program, the four optical interface rates can be accurately and cost-effectively identified, effectively resolving the problems of the prior art.

Claims

1. A method for identifying an adaptive rate of an SDH optical interface, characterized by: It includes an optical transmitting end processing module and an optical receiving end processing module; At the optical transmitting end, the optical transmitting end processing module sets the reference clock, line rate and data bit width of the external optical signal according to the optical interface rate instruction, and then obtains the optical transmitting signal after framing and scrambling processing; The optical interface rate is at least one; the reference clocks set for the optical interface rates are the same; the data bit widths set for the optical interface rates are the same; the optical receiving end processing module includes a cross-clock domain processing submodule, a frame header search submodule, and a line rate adaptation submodule; At the optical receiving end, the optical receiving end processing module performs cross-clock domain processing, frame header search, and line rate adaptation on the optical transmission signal; The cross-clock domain processing submodule uses a first buffer; For the optical transmission signal at each optical port rate, the cross-clock domain processing submodule reads and writes the data of the optical transmission signal in an asynchronous first-in-first-out manner, specifically: Using the line clock corresponding to the line rate as a write clock signal, continuously and uninterruptedly write each SDH code stream data having a width equal to the data bit width; After writing the valid data, using the local clock as the read clock signal, continuously and uninterruptedly read each SDH code stream data having a width equal to the data bit width to the first buffer; The number of bits of the first buffer is the same as the data bit width; the first buffer outputs SDH code stream parallel data with the same width as the data bit width; The frame header search submodule uses a second buffer and a third buffer; the number of bits of the second buffer is twice the data bit width; the number of bits of the third buffer is the same as the data bit width; The frame header search submodule performs cyclic sorting and frame header search on the SDH code stream parallel data outputted by the first buffer each time; The specific process of the cyclic sorting is: For each piece of SDH code stream parallel data, the SDH code stream parallel data is stored in the low order of the second buffer, the SDH code stream parallel data is delayed by one clock cycle under the local clock, and then stored in the high order of the second buffer; The parallel data outputted from the second buffer is sequentially shifted into the third buffer.

2. The method for identifying an SDH optical interface adaptive rate according to claim 1, wherein: The SDH code stream parallel data entering the third buffer is continuously searched, and when 0XF6F6F6F6 is searched in the current data of the third buffer and 0X28282828 is searched in the subsequent data, a frame header search success flag is provided.

3. The method for identifying an SDH optical interface adaptive rate according to claim 2, wherein: The bytes of the SDH code stream parallel data entering the third buffer are counted with the flag bit as a starting point, and the line rate is determined according to the number of bytes.

4. The method for identifying an SDH optical interface adaptive rate according to claim 1, wherein: The optical interface rate is one of 155.52 Mbit / s, 622.08 Mbit / s, 2488.32 Mbit / s and 9953.28 Mbit / s.

5. The method for identifying an SDH optical interface adaptive rate according to claim 1, wherein: The frame format involved in the framing is one of STM-1, STM-4, STM-16 and STM-64.

6. The method for identifying an adaptive rate of an SDH optical interface according to claim 1, wherein: The framed signal is scrambled by a 7-level scrambler to obtain an optical transmission signal.

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