JP5856660B1 - Frame data division method - Google Patents

Abstract

The present invention provides a method for dividing frame data so that the frame structure can be maintained and transmitted using two subcarriers in a digital coherent optical transmission system. A method of dividing an OTU frame that is optically transmitted in an OTN into two, wherein a combination of a first OTU frame and a second OTU frame that are consecutive, the FEC region of the first OTU frame and the first OTU frame A plurality of data obtained by replacing the OH area and the payload area of the second OTU frame with the FEC area of the first OTU frame adjacent to the FEC area of the second OTU frame and then dividing the FEC area for each predetermined byte from the top. Are divided into a first sub-frame consisting of odd-numbered segments and a second sub-frame consisting of even-numbered segments. The occupation ratio of the FEC area in each subframe is equal to the occupation ratio of the FEC area in one OTU frame, and the FEC processing circuit can be shared. [Selection] Figure 3

Description

  The present invention relates to a frame data division method, and more particularly to a frame data division method for dividing frame data while maintaining a frame configuration in a digital coherent optical transmission system that divides and transmits two subcarriers.

  Conventionally, research and development of WDM (wavelength division multiplexing) technology capable of increasing the capacity of an optical transmission system has been performed. In addition, as with the WDM technology, as a technology capable of increasing the capacity of an optical transmission system, coherent communication technology and research and development have been actively conducted. In parallel with the increase in capacity of optical transmission systems, the bit rate of client data communicated over a LAN or the like is also increasing. Nowadays, there is a growing need for accommodating large-capacity client data (for example, 100 Gbps) directly in a line signal of an optical transmission system and transmitting it, and research is being actively conducted to realize this.

  FIG. 4 is a schematic configuration diagram of an optical transmission system integrated circuit (LSI) that transmits client data using a plurality of subcarriers. The optical transmission system LSI (10) of FIG. 4 includes one 100 Gbps high-speed I / F (12, 22) for each of transmission and reception. Through these 100 Gbps high-speed I / Fs, input / output of a 100 Gbps client signal is performed between a client device (for example, a router) and the optical transmission system LSI (10).

  In FIG. 4, the optical modulator / light source 150 has two sets of a light source and an IQ modulator, and the output from the IQ modulator is polarization-multiplexed and output to the transmission line. The light receiver 180 photoelectrically converts and outputs light incident from an optical fiber transmission line (light propagated through a transmission line polarization-multiplexed by an opposing optical modulator / light source).

  The 100 G symbol mapping unit 14 accommodates a 100 Gbps client signal input from the 100 Gbps high-speed I / F (12) in a transmission frame for optical transmission of 100 Gbps (for example, an OTU4 frame (112 Gbps)), and the client signal is 2 A symbol of QPSK modulation mapped (assigned) for each bit is determined, and an amplitude and a phase (angle) corresponding to the determined symbol are output.

  The digital coherent signal processing unit 16 generates and outputs a modulation signal to be supplied to the modulator / light source 150 based on the symbols from the 100G symbol mapping unit 14.

  The digital coherent signal processing unit 26 performs digital signal processing such as distortion compensation, clock extraction, phase estimation, and symbol identification based on the signal from the light receiver 180, and outputs the identified symbol.

  The 100G symbol demapping unit 24 demaps the symbol output from the digital coherent signal processing unit 26 and outputs a bit value (determines and outputs a bit value assigned to the symbol). Specifically, in the 100G symbol demapping unit 24, the demapped bit value is a bit value constituting a transmission frame for optical transmission (in the above example, an OTU4 frame), and is transmitted to the client signal in the transmission frame. The corresponding bit value is output.

  The 100 Gbps high-speed I / F (22) is used to output the bit value from the 100G symbol demapping unit 24 as a client signal received outside the optical transmission system LSI (10).

  However, the bit rate of the line signal of the optical transmission system may be limited due to the transmission characteristics and modulation method in the optical fiber transmission line, and all the transmission frames containing the client signal are transferred to the line signal of the optical transmission system. May not be able to be accommodated directly. Therefore, there is a need to divide a transmission frame and transmit it.

  The present invention has been made in view of such a problem, and an object of the present invention is to maintain frame configuration so that frame data can be transmitted using two subcarriers in a digital coherent optical transmission system. Provide a way to divide.

  In order to achieve such an object, a first aspect of the present invention is a data dividing method in which an optical transmission system integrated circuit divides data. This data division method is a method of dividing a frame, which is optically transmitted in an optical transmission network (OTN), each having an overhead (OH) region, a payload region, and a forward error correction (FEC) region into two. And a replacement step of replacing the FEC area of the first frame with the OH area and the payload area of the second frame for a set of continuous first FEC area and second FEC area. In addition, this method divides a plurality of segments divided for each predetermined byte in order from the head of the first FEC area and the second FEC area after the replacement step into odd-numbered segments and even-numbered segments. Then, a dividing step of making a first subframe and a second subframe is included.

  In one embodiment, the frame prior to the replacement step may be an OTU4 frame. In each of the first subframe and the second subframe after the replacement step, the first FEC area is arranged adjacent to the second FEC area. Further, in each of the first subframe and the second subframe after the replacement step, the occupation ratio of the first FEC region and the second FEC region is equal to the FEC region in one frame before the replacement step. Equal to occupation ratio.

  As described above, according to the present invention, it is possible to provide a method of dividing frame data so that the frame structure can be maintained and transmitted using two subcarriers in a digital coherent optical transmission system. Become.

It is a figure which shows the structural example which shows the optical transmission system using the optical transmission system integrated circuit which can mount the frame data division | segmentation method of one Embodiment of this invention. It is a reference diagram for explaining a frame data division method according to an embodiment of the present invention. It is a figure for demonstrating the frame data division | segmentation method which concerns on one Embodiment of this invention. It is a schematic block diagram of the optical transmission system integrated circuit which transmits client data using a several subcarrier.

  Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings. In the drawings, the same or similar reference numerals indicate the same or similar elements. Therefore, repeated description of the same or similar elements is omitted. In the following description, in an optical transmission system that transmits a 100 Gbps client signal from a sending client device to a receiving client device, a frame containing the 100 Gbps client signal is represented by two signals (in this specification, “transmission signal”). In the following, an example will be described in which transmission is performed using a coherent communication method using subcarriers (also referred to as “wavelength channels” in this specification) of wavelength bands of λ1 and λ2, respectively. However, the present invention is not limited to such specific numerical examples, and it goes without saying that losing generality can also be implemented with other numerical values.

  First, an example of an optical transmission system using an optical transmission system integrated circuit capable of implementing the frame data division method according to an embodiment of the present invention will be described with reference to FIG. In the optical transmission system of FIG. 1, an optical transmission system integrated circuit (100T) is an LSI that inputs and outputs a client signal to and from a client device (for example, a router) on the transmission side, and the optical transmission system integrated circuit (100R). Is an LSI that inputs / outputs client signals to / from client devices on the receiving side.

  The optical transmission system LSI (first optical transmission system LSI (100T-1)) has a 100 Gbps high-speed I / F (102) for inputting a client signal and a frame (OTU4, simply a transmission signal) containing a 100 Gbps client signal. 50G separation unit 104 that separates the transmission signal into two transmission signals (also referred to as subframes in the present application) and digital coherent processing on one transmission signal (first transmission signal (first subframe)). The other transmission signal (second transmission signal (second transmission signal (second transmission signal) (second transmission signal LSI)) is connected between the digital coherent signal processing unit 106-1 and the other optical transmission system LSI (second optical transmission system LSI (100T-2)). And an inter-chip transfer processing unit 108-1 for communicating subframes)).

  The optical transmission system LSI (100T-1) maps (assigns) the bits of the first transmission signal to the symbols of the modulation scheme (BPSK) between the 50G separation unit 104 and the digital coherent signal processing unit 106-1. A 50G mapping circuit (not shown) is provided.

  Also, the optical transmission system LSI (100T-1) maps the bits of the frame containing the 100 Gbps client signal to the modulation scheme (QPSK) symbol between the 100 Gbps high-speed IF 102 and the digital coherent signal processing unit 106-1. A 100G mapping circuit (not shown) that performs (assigns), and a selector (not shown) that switches the input to the digital coherent signal processing unit 106-1 between a 50G mapping circuit (not shown) and a 100G mapping circuit (not shown). (Shown) may be further provided. Accordingly, when 100 Gbps optical transmission is possible, a QPSK modulation symbol in which bits of a frame (transmission signal) containing a 100 Gbps client signal are mapped is supplied to the digital coherent signal processing unit 106-1, and 100 Gbps. When the optical transmission is not possible, the BPSK modulation symbol to which the first transmission signal divided from the frame accommodating the 100 Gbps client signal is mapped is supplied to the digital coherent signal processing unit 106-1. The applicability of the optical transmission system LSI (100T-1) can be improved.

  The digital coherent signal processing unit 106-1 performs digital coherent processing on the transmission signal (frame) or the first transmission signal (first subframe), and the modulation signal (for example, the amplitude) Digital coherent signal processing is performed and output. The modulation signal from the digital coherent signal processing unit 106-1 is supplied to the optical modulator / light source 150-1. As a result, a frame (transmission signal) containing a client signal of 100 Gbps or a first transmission signal separated from the frame is a subcarrier (wavelength channel) in the wavelength band of λ1 from the optical modulator / light source 150-1. It is transmitted by.

  The inter-chip transfer processing unit 108-1 transfers the other transmission signal (second transmission signal (second subframe)) separated from the frame (transmission signal) containing the client signal to the optical transmission system LSI (100T- 2) Performing lane processing, error correction processing, framing processing, and the like on the second transmission signal, which are necessary when communicating with 2).

  The optical transmission system LSI (100T-2) includes an inter-chip transfer processing unit 108-2 and a digital coherent signal processing unit 106-2. The optical transmission system LSI (100T-2) is separated from the second transmission signal (OTU4 frame) between the inter-chip transfer processing unit 108-2 and the digital coherent signal processing unit 106-2 that performs digital coherent processing. A 50G mapping circuit (not shown) is provided that maps (assigns) the bits of the signal to the symbols of the modulation scheme (BPSK).

  The inter-chip transfer processing unit 108-2 is opposed to the inter-chip transfer processing unit 108-1, and performs a process of decoding the second transmission signal.

  Similarly to the digital coherent signal processing unit 106-1, the digital coherent signal processing unit 106-2 performs digital processing on a modulation signal (for example, amplitude and phase) corresponding to the second transmission signal (second subframe). Perform coherent signal processing and output. The modulation signal from the digital coherent signal processing unit 106-2 is supplied to the optical modulator / light source 150-2. As a result, the second transmission signal is transmitted by the subcarrier (wavelength channel) in the wavelength band of λ2 from the optical modulator / light source 150-2.

  The wavelength channel of λ1 and the wavelength channel of λ2 are combined by the wavelength multiplexer 160 and propagated through the optical fiber to the wavelength separator 170 as a wavelength multiplexed signal. The wavelength channel of λ1 is photoelectrically converted by the light receiver 180-2 and input to the optical transmission system LSI (100R-2). The wavelength channel of λ2 is photoelectrically converted by the light receiver 180-2 and input to the optical transmission system LSI (100R-1).

  The optical transmission system LSI (100R-1) includes a digital coherent signal processing unit 126-1, a 50G multiplexing unit (50G integration unit) 124, an inter-chip transfer processing unit 128-1, and a 100 Gbps high-speed I / F (122). With. Further, the optical transmission system LSI (100R-1) includes a 50G demapping circuit (not shown) in the subsequent stage of the digital coherent signal processing unit 126-1, and outputs the 50G demapping circuit in the previous stage of the 50G multiplexing unit 124. A deskew buffer 125 is provided.

  The digital coherent signal processing unit 126-1 performs digital signal processing such as distortion compensation, clock extraction, phase estimation, and symbol identification based on the signal from the light receiver 180-1, and outputs the identified symbol. The identified symbols are demapped (decoded) into bits of a received signal (second received signal corresponding to the second transmitted signal) in a 50G demapping circuit (not shown), and temporarily stored in the deskew buffer 125. Timing with the bit of the received signal (first received signal corresponding to the first transmitted signal) demapped from the symbol identified in the digital coherent signal processing unit 126-2 of the optical transmission system LSI (100R-2) Is adjusted.

  The 50G multiplexing unit 124 multiplexes (combines) the first reception signal and the second reception signal to reproduce a frame containing a 100 Gbps client signal. The client signal extracted from the reproduced 100 Gbps frame is output from the 100 Gbps high-speed IF (122) to the receiving client apparatus.

  The optical transmission system LSI (100R-2) includes a digital coherent signal processing unit 126-2 and an inter-chip transfer processing unit 128-2. The optical transmission system LSI (100R-2) includes a 50G demapping circuit (not shown) between the digital coherent signal processing unit 126-2 and the inter-chip transfer processing unit 128-2.

  The digital coherent signal processing unit 126-2, like the digital coherent signal processing unit 126-1, performs digital signal processing such as distortion compensation, clock extraction, phase estimation, and symbol identification based on the signal from the optical receiver 180-2. To output the identified symbol. The identified symbol is demapped (decoded) into bits of a reception signal (first reception signal corresponding to the first transmission signal) in a 50G demapping circuit (not shown).

  The inter-chip transfer processing unit 128-1 and the inter-chip transfer processing unit 128-2 are required for communication between the optical transmission system LSI (100R-1) and the optical transmission system LSI (100R-2). 2 lane processing, error correction processing, framing processing, etc. are performed on the received signal.

  Similar to the optical transmission system LSI (100T-1), the optical transmission system LSI (100R-1) transmits a modulation scheme (QPSK) symbol between the 100 Gbps high-speed IF 122 and the digital coherent signal processing unit 126-1. And a 100G demapping circuit (not shown) that demaps (decodes) the received client signal into bits of the received signal and outputs the output from the digital coherent signal processing unit 126-1 to the 50G demapping circuit (not shown). And a 100G demapping circuit (not shown) may further be provided. Thus, when 100 Gbps optical transmission is possible, the digital coherent signal processing unit 126-1 supplies a QPSK modulation symbol to the 100G demapping circuit, and when 100 Gbps optical transmission is impossible, digital coherent The symbol of BPSK modulation can be supplied from the signal processing unit 126-1 to a 50G demapping circuit (not shown), and the applicability of the optical transmission system LSI (100R-1) can be improved. At the same time, the circuit scale of the optical transmission system LSI (100R-1) is shared by sharing the digital coherent signal processing unit 126-1 as compared with the case where a plurality of digital coherent signal processing units having a relatively high occupation ratio with respect to the entire LSI is used. Can be reduced.

  In the optical transmission system of FIG. 1 described above, the first reception signal is received by the inter-chip transfer processing unit on the receiving side, and the second transmission signal is input by the inter-chip transfer processing unit on the transmitting side. Processing and framing processing are performed. For this reason, the deskew of the optical transmission system LSI (100R-1) is compared with the case where each processing is performed in the inter-chip transfer processing unit on the transmission side and the reception side for both the first transmission signal and the first reception signal. The buffer can be made small. However, since it is not known which of the first reception signal and the second reception signal arrives with a larger delay, there is further a deskew buffer (between the inter-chip transfer processing unit 128-1 and the 50G multiplexing unit 124). (Not shown) may be provided.

  Next, a frame data dividing method according to an embodiment of the present invention will be described with reference to FIGS. It is mounted on the 50G separation unit 104 of the optical transmission system integrated circuit (LSI) 100T in the optical transmission system described above, and is mounted when the frame (OTU4) containing the client signal is separated into the first and second transmission signals. be able to. Each frame (OTU4 frame) of 100 Gbps input to the 50G separation unit 104 has an overhead (OH) area, a payload area, and an error correction code (FEC) area. The client signal is stored in the payload area. The byte length of each frame is 16 × 255 × 4 bytes.

  FIG. 2 (a) shows a 16 × 255-byte quarter frame (including an OH area) that is a part of a 100 Gbps frame (OTU4 frame) each containing a client signal input to the 50G separation unit 104. Part). In the following description, for the sake of simplicity, the ¼ frame shown in FIGS. 2A and 3A is used.

  Each sequentially input frame as shown in FIG. 2A is divided into 255 segments every 16 bytes, and a set of odd-numbered segments as shown in FIG. 2B1 (first transmission signal) (First subframe)) and an even-numbered segment set (second transmission signal (second subframe)) as shown in FIG. 2 (b2) can be considered.

  In the case of FIG. 2, since the cycle in which the FEC area appears is not fixed to an even multiple of 16 bytes, the occupation ratio of the FEC area differs between the first transmission signal and the second transmission signal for one frame (the first Since the byte lengths of the transmission signal and the second transmission signal are different), the positions (intervals or cycles) at which the FEC areas appear in each are not constant.

  As a result, in the case of FIG. 2, in order to process the FEC area of the first transmission signal and the second transmission signal, the FEC processing circuit for processing the FEC area of the frame (OTU4) before separation is shared (re-used). Use). Therefore, it is necessary to separately add a circuit for processing the FEC area in the first transmission signal and the second transmission signal, and the circuit scale of the optical transmission system LSI (100T, 100R) increases.

  On the other hand, as shown in FIG. 3 (b), for the set of two frames sequentially input as shown in FIG. 3 (a), the FEC area 1, the overhead area 2 and the payload area 2 are replaced, and 16 bytes. Each segment is divided into 2 × 255 segments, and a set of odd-numbered segments (first transmission signal (first subframe)) as shown in FIG. 3 (c1) and as shown in FIG. 3 (c2). It is conceivable to separate it into a set of even-numbered segments (second transmission signal (second subframe)).

  In the case of FIG. 3, the first transmission signal (FIG. 3 (c1)) and the second transmission signal (FIG. 3 (c2)) related to two frames have the same occupation ratio in the FEC area and one OTU4 frame. The same as the occupation ratio of the FEC area in FIG. Further, the position and size of the FEC area in the first transmission signal (FIG. 3 (c1)) and the second transmission signal (FIG. 3 (c2)) are also the same as the position and size of the FEC area in one OTU4 frame. It becomes.

  Therefore, in the case of FIG. 3, in order to process the FEC area of the first transmission signal and the second transmission signal, the processing circuit of the FEC processing circuit for processing the FEC area of the frame (OTU4) before separation is shared. (Reuse). Therefore, it is not necessary to add a circuit for processing the FEC area in the first transmission signal and the second transmission signal, so that the circuit scale of the optical transmission system LSI (100T, 100R) is larger than that in FIG. Can be small.

  Although the embodiments of the present invention have been described above, the present frame data division method may be used to divide one or a plurality of frames when there are a plurality of input client signals. May switch between even and odd segment selection for each frame so that frame synchronization patterns are alternately arranged in the first transmission signal and the second transmission signal.

10 Optical transmission system integrated circuit (LSI)
12 100Gbps high-speed interface (I / F)
14 100G Symbol Mapping Unit 16 Digital Coherent Signal Processing Unit 22 Optical Transmission System Integrated Circuit (LSI)
24 Symbol Demapping Unit for 100G 26 Digital Coherent Signal Processing Unit 150 Optical Modulator / Light Source 160 Wavelength Multiplexing Unit 170 Wavelength Separating Unit 180 Light Receiver 100T, 100R Optical Transmission System Integrated Circuit (LSI)
102, 122 100Gbps high-speed interface (I / F)
104 50G separation unit 106,126 Digital coherent signal processing unit 108,128 Inter-chip transfer processing unit 124 50G multiplexing unit (50G integration unit)
125 deskew buffer

Claims (3)

An optical transmission system integrated circuit divides a frame that is optically transmitted in an optical transmission network (OTN) into two, each of which includes an overhead (OH) region, a payload region, and a forward error collection (FEC). )
The method
A replacement step of replacing the FEC area of the first frame with the OH area and payload area of the second frame for a set of consecutive first FEC area, second OH area and payload area;
A plurality of segments divided for each predetermined byte in order from the top of the data sequence in which the FEC area, the OH area, and the payload area are replaced are divided into odd-numbered segments and even-numbered segments, and the first subframe and A data division method comprising: a division step of subframes.   In each of the first subframe and the second subframe, the FEC area of the divided first frame is arranged adjacent to the divided FEC area of the second frame. The data division method according to claim 1, wherein:   In each of the first subframe and the second subframe, the occupation ratio of the FEC area of the divided first frame and the FEC area of the divided second frame is the FEC area in the frame. The data division method according to claim 2, wherein the data division method is equal to the occupation ratio of the area.

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