Optical transmission system and transmission mode selection method

Abstract

An optical transmission system, which is an optical transmission system comprising an optical transmitting device and an optical receiving device for receiving a signal transmitted from the optical transmitting device via an optical transmission path, comprises: a transmission mode selection unit which selects transmission mode information in order of priority from a plurality of transmission mode information which is a combination of a plurality of parameters related to transmission performance and which is common to the transmission performance of the optical transmitting device and the optical receiving device; a signal transmitting unit which transmits a modulated signal to the optical receiving device based on the selected transmission mode information; and a signal receiving unit which receives a signal and demodulates the received signal based on the transmission mode information selected by the transmission mode selection unit.

Description

Technical Field

[0001] The invention relates to an optical transmission system and a transmission mode selection method.

[0002] This application claims priority based on Japanese Patent Application No. 2018-148920 filed in Japan on August 7, 2018, the contents of which are incorporated herein. Background Art

[0003] With the advancement of digital signal processing (hereinafter referred to as "DSP") for optical transmission, not only the modulation methods have increased, but also various parameters related to transmission performance, such as baud rate, types of error correction coding such as FEC (Forward Error Correction), and the number of carriers, have increased, and the transmission mode has become more diverse. For example, Patent Document 1 discloses a method for selecting an optimal modulation method based on a training signal.

[0004] Prior Art Literature

[0005] Patent Literature

[0006] Patent document 1: Japanese Patent No. 5753604. Summary of the invention

[0007] Problems to be solved by the invention

[0008] However, the technology described in Patent Document 1 has a problem in that it is not possible to select an optimal transmission mode in accordance with various parameters related to transmission performance, such as a baud rate, a type of error correction coding, and the number of carriers, in addition to the modulation method.

[0009] In view of the above circumstances, an object of the present invention is to provide a technology capable of selecting an optimal transmission mode from among transmission modes determined by a combination of a plurality of parameters related to transmission performance.

[0010] Solutions to Solve Problems

[0011] One embodiment of the present invention is an optical transmission system, which is an optical transmission system comprising an optical transmitting device and an optical receiving device for receiving a signal transmitted from the aforementioned optical transmitting device via an optical transmission path, and comprises: a transmission mode selection unit, which selects the aforementioned transmission mode information in order of high priority from a plurality of aforementioned transmission mode information which is a combination of a plurality of parameters related to transmission performance, i.e., transmission mode information, and is common to the aforementioned transmission performance of the aforementioned optical transmitting device and the aforementioned optical receiving device; a signal transmitting unit, which transmits a modulated signal to the aforementioned optical receiving device based on the selected aforementioned transmission mode information; and a signal receiving unit, which receives the aforementioned signal and demodulates the received aforementioned signal based on the aforementioned transmission mode information selected by the aforementioned transmission mode selection unit.

[0012] One embodiment of the present invention is the above-mentioned optical transmission system, further comprising: a signal quality detection unit, which detects the signal quality of the received signal; and a signal quality determination unit, which determines whether the signal quality of the signal is allowed based on information indicating the signal quality detected by the signal quality detection unit, and when the signal quality determination unit determines that the signal quality of the signal is not allowed, the transmission mode selection unit selects the transmission mode information with the next highest priority.

[0013] One embodiment of the invention is the above-mentioned optical transmission system, wherein the above-mentioned optical sending device comprises: a transmission mode candidate sending unit, which sends the sending side transmission mode candidate information including the above-mentioned transmission mode information of the optical sending device to the above-mentioned optical receiving device; a transmission mode candidate receiving unit, which receives the receiving side transmission mode candidate information including the above-mentioned transmission mode information of the above-mentioned optical receiving device from the above-mentioned optical receiving device; and the above-mentioned transmission mode selecting unit, wherein the above-mentioned optical receiving device comprises: a transmission mode candidate receiving unit, which receives the above-mentioned sending side transmission mode candidate information from the above-mentioned optical sending device; a transmission mode candidate sending unit, which sends the above-mentioned receiving side transmission mode candidate information to the above-mentioned optical sending device when the above-mentioned transmission mode candidate receiving unit receives the above-mentioned sending side transmission mode candidate information; and the above-mentioned transmission mode selecting unit.

[0014] One embodiment of the present invention is the above-mentioned optical transmission system, wherein the above-mentioned transmission mode candidate sending unit of the above-mentioned optical sending device overlaps the above-mentioned sending side transmission mode candidate information with a pilot tone signal which is a signal sequence whose power is concentrated on one or more specific frequencies and sends it to the above-mentioned signal sending unit, and the above-mentioned transmission mode candidate receiving unit of the above-mentioned optical receiving device receives the above-mentioned sending side transmission mode candidate information overlapped with the above-mentioned pilot tone signal received by the above-mentioned signal receiving unit.

[0015] One embodiment of the present invention is the above-mentioned optical transmission system, wherein the above-mentioned transmission mode candidate sending unit of the above-mentioned optical sending device writes the above-mentioned sending side transmission mode candidate information into a predetermined field of a signal frame of a main signal included in the above-mentioned signal and sends it to the above-mentioned signal sending unit, and the above-mentioned transmission mode candidate receiving unit of the above-mentioned optical receiving device reads the above-mentioned sending side transmission mode candidate information included in the above-mentioned predetermined field of the above-mentioned signal frame of the above-mentioned main signal.

[0016] One embodiment of the present invention is the above-mentioned optical transmission system, further comprising a control device, the aforementioned control device comprising the aforementioned transmission mode selection unit, the aforementioned transmission mode selection unit, when selecting the aforementioned transmission mode information, generates a transmission mode designation signal that specifies the selected aforementioned transmission mode information, sends the generated aforementioned transmission mode designation signal to the aforementioned optical transmitting device and the aforementioned optical receiving device, and the aforementioned optical transmitting device and the aforementioned optical receiving device operate in a transmission mode corresponding to the aforementioned transmission mode designation signal sent from the aforementioned transmission mode selection unit.

[0017] One embodiment of the present invention is the above-mentioned optical transmission system, which is further provided with a management device, wherein the aforementioned management device comprises: a transmission design information storage unit, which stores information on physical characteristic parameters of various modules equipped in the aforementioned optical transmission path, the aforementioned optical transmitting device and the aforementioned optical receiving device, and the aforementioned transmission mode information of the aforementioned optical transmitting device and the aforementioned optical receiving device; and a transmission design processing unit, which calculates the transmission quality based on the aforementioned physical characteristic parameters for each aforementioned transmission mode information, generates a transmission mode candidate list including a plurality of transmission mode information selected based on the calculated transmission quality, sends the generated aforementioned transmission mode candidate list to the aforementioned control device, and the aforementioned transmission mode selection unit of the aforementioned control device selects the aforementioned transmission mode information from the received aforementioned transmission mode candidate list in order of high priority.

[0018] One embodiment of the present invention is a transmission mode selection method, which is a transmission mode selection method in an optical transmission system including an optical transmitting device and an optical receiving device for receiving a signal transmitted from the optical transmitting device via an optical transmission path, wherein the transmission mode information is selected in order of priority from a plurality of transmission mode information common to the transmission performance of the optical transmitting device and the optical receiving device, i.e., a combination of a plurality of parameters related to transmission performance, i.e., transmission mode information, and a modulated signal is transmitted to the optical receiving device based on the selected transmission mode information, the signal is received, and the received signal is demodulated based on the transmission mode information selected by the transmission mode selection unit.

[0019] One embodiment of the present invention is the above-mentioned optical transmission system, which is further provided with a management device, wherein the aforementioned management device comprises: a transmission design information storage unit, which stores information on physical characteristic parameters of various modules equipped in the aforementioned optical transmission path, the aforementioned optical transmitting device and the aforementioned optical receiving device, and the aforementioned transmission mode information of the aforementioned optical transmitting device and the aforementioned optical receiving device; a transmission design processing unit, which calculates the transmission quality based on the aforementioned physical characteristic parameters for each of the aforementioned transmission mode information, and generates a transmission mode candidate list including a plurality of transmission mode information selected based on the calculated transmission quality; a network design information storage unit, which collects network information including any one or all of the topology information, node information, and path information of the aforementioned optical transmission path, and stores the collected aforementioned network information; and a network design processing unit, which uses the aforementioned network information to perform accommodation design processing of the optical path required to improve network utilization efficiency for each of the aforementioned transmission mode information, thereby sending the aforementioned transmission mode candidate list with information indicating priority attached to the aforementioned control device for each of the aforementioned transmission mode information, and the aforementioned transmission mode selection unit of the aforementioned control device selects the aforementioned transmission mode information from the received aforementioned transmission mode candidate list in order of high priority.

[0020] One embodiment of the present invention is the above-mentioned optical transmission system, wherein the above-mentioned control device further comprises: a transmission design information storage unit, which stores information on physical characteristic parameters of various modules equipped in the above-mentioned optical transmission path, the above-mentioned optical transmitting device and the above-mentioned optical receiving device, and the above-mentioned transmission mode information of the above-mentioned optical transmitting device and the above-mentioned optical receiving device; and a transmission design processing unit, which calculates the transmission quality based on the above-mentioned physical characteristic parameters for each of the above-mentioned transmission mode information, generates a transmission mode candidate list including a plurality of transmission mode information selected based on the calculated transmission quality, outputs the generated above-mentioned transmission mode candidate list to the above-mentioned transmission mode selection unit, and the above-mentioned transmission mode selection unit selects the above-mentioned transmission mode information from the output above-mentioned transmission mode candidate list in order of high priority.

[0021] One embodiment of the present invention is the above-mentioned optical transmission system, wherein the above-mentioned control device comprises: a signal quality detection unit, which detects the signal quality of the above-mentioned received signal; and a signal quality determination unit, which determines whether the signal quality of the above-mentioned signal is allowed based on the information indicating the above-mentioned signal quality detected by the above-mentioned signal quality detection unit, and the above-mentioned transmission mode selection unit selects the above-mentioned transmission mode information with the second highest priority when the above-mentioned signal quality determination unit determines that the signal quality of the above-mentioned signal is not allowed.

[0022] Effects of the Invention

[0023] According to the present invention, it is possible to select an optimal transmission mode from among transmission modes determined by a combination of a plurality of parameters related to transmission performance. BRIEF DESCRIPTION OF THE DRAWINGS

[0024] Figure 1 This is a block diagram showing the configuration of the optical transmission system according to the first embodiment.

[0025] Figure 2 This is a block diagram showing the internal structure of the optical transmission device according to the first embodiment and the connection relationship with other devices.

[0026] Figure 3 This is a diagram showing the structure of an OTN frame according to the first embodiment (Part 1).

[0027] Figure 4 This is a block diagram showing the internal structure of the error correction coding unit according to the first embodiment and the connection relationship with other functional units.

[0028] Figure 5 This is a diagram showing the structure of the OTN frame according to the first embodiment (part 2).

[0029] Figure 6 It is a diagram showing the structure of the transmission signal format according to the first embodiment.

[0030] Figure 7 It is a diagram showing the data structure of the transmission mode information table according to the first embodiment.

[0031] Figure 8 It is a diagram showing the data structure of the transmission mode information table on the transmission side according to the first embodiment.

[0032] Fig. 9 This is a block diagram showing the internal structure of the optical receiving device according to the first embodiment and the connection relationship with other devices.

[0033] Fig.10 This is a block diagram showing the internal structure of the error correction decoding unit according to the first embodiment and the connection relationship with other functional units.

[0034] Fig.11 It is a diagram showing the data structure of the reception-side transmission mode information table according to the first embodiment.

[0035] Fig.12 This is a diagram (part 1) showing the connection relationship between the optical receiving device and the optical transmitting device in the receiving-side system according to the first embodiment.

[0036] Fig.13 This is a diagram (part 1) showing the connection relationship between the optical transmitting device and the optical receiving device in the transmitting-side system according to the first embodiment.

[0037] Fig.14 This is a flowchart showing the flow of the transmission mode selection process according to the first embodiment.

[0038] Fig.15 This is a diagram (part 2) showing the connection relationship between the optical transmitting device and the optical receiving device in the transmitting-side system according to the first embodiment.

[0039] Fig.16 This is a diagram (part 2) showing the connection relationship between the optical receiving device and the optical transmitting device in the receiving-side system of the first embodiment.

[0040] Fig.17 This is a block diagram showing the internal configuration of the optical transmission device of another configuration example of the first embodiment and the connection relationship with other devices.

[0041] Fig.18 This is a block diagram showing the internal structure of the light receiving device of another structural example of the first embodiment and the connection relationship with other devices.

[0042] Fig.19 It is a block diagram showing the configuration of an optical transmission system according to the second embodiment.

[0043] Fig. 20 This is a flowchart showing the flow of the transmission mode selection process according to the second embodiment.

[0044] Fig.21 It is a block diagram showing the configuration of an optical transmission system according to the third embodiment.

[0045] Fig. 22 This is a flowchart showing the flow of processing by the management device according to the third embodiment.

[0046] Fig.23 This is a flowchart showing the flow of the transmission mode selection process according to the third embodiment.

[0047] Fig.24 It is a block diagram showing the configuration of an optical transmission system according to a fourth embodiment.

[0048] Fig.25 This is a flowchart showing the flow of processing by the management device according to the fourth embodiment.

[0049] Fig.26 It is a block diagram showing the configuration of an optical transmission system according to the fifth embodiment.

[0050] Fig. 27 It is a block diagram showing the configuration of an optical transmission system according to the sixth embodiment. DETAILED DESCRIPTION

[0051] (First embodiment)

[0052] Hereinafter, embodiments of the present invention will be described with reference to the drawings. Figure 11 is a block diagram showing the configuration of an optical transmission system S according to the first embodiment. The optical transmission system S includes a transmission side system T, a reception side system R, and an optical transmission path 3. The transmission side system T includes an optical transmission device 1t, an optical reception device 2t, and a multiplexing unit 4T. The reception side system R includes an optical reception device 2r, an optical transmission device 1r, and a multiplexing unit 4R.

[0053] The optical transmission path 3 physically connects the transmission side system T and the reception side system R. The optical transmission path 3 transmits signal light between the transmission side system T and the reception side system R. The optical transmission path 3 is, for example, an optical fiber 300. Multiplexing units 4T and 4R are connected to both ends of the optical fiber 300.

[0054] The multiplexing unit 4T is connected to the optical transmitter 1t and the optical receiver 2t of the transmission side system T. The multiplexing unit 4R is connected to the optical receiver 2r and the optical transmitter 1r of the reception side system R. The signal light transmitted by the optical transmitter 1t of the transmission side system T is transmitted to the optical receiver 2r of the reception side system R through the optical transmission path 3. In addition, the signal light transmitted by the optical transmitter 1r of the reception side system R is transmitted to the optical receiver 2t of the transmission side system T through the optical transmission path 3. The multiplexing units 4T and 4R may be functional units that perform wavelength multiplexing or may be functional units that do not perform wavelength multiplexing. For example, as an application case of the present invention, there is also a configuration in which the transmission side system T and the reception side system R are opposed to each other with only one wavelength that does not perform wavelength multiplexing. That is, there is also a configuration in which the transmission side system T and the reception side system R include the multiplexing units 4T and 4R as a part (multiplexing unit) that multiplexes the optical transmitter 1t and the optical receiver 2r instead of wavelength multiplexing.

[0055] In the optical transmission system S, the optical transmitter 1t and the optical receiver 2r are opposed to each other, that is, the transmission modes are matched so that signal light is transmitted from the optical transmitter 1t to the optical receiver 2r. Similarly, the optical transmitter 1r and the optical receiver 2t are opposed to each other.

[0056] exist Figure 1In the above, the transmission mode between the transmission side system T and the reception side system R is determined. However, since the transmission mode is usually the same in both directions in the above-mentioned opposing relationship, the optical transmission device 1t of the transmission side system T and the optical receiving device 2r of the receiving side system R are mainly indicated by solid lines, and the optical receiving device 2t and the optical transmission device 1r are indicated by dotted lines. In addition, when the transmission side system is regarded as the downstream side and the reception side system is regarded as the upstream side, in the case where the transmission mode of the uplink from the transmission side to the reception side and the downlink from the reception side to the transmission side are different, the optimal transmission mode may be determined between the optical receiving device 2t and the optical transmission device 1r of the downlink to achieve the normal operation state, or the transmission mode may be determined by performing the same processing as between the optical transmission device t1 and the optical receiving device 2r.

[0057] The "transmitting side" of the transmitting side system T and the "receiving side" of the receiving side system R are simplified names for explanation. The meaning is that the optical transmitting device 1t is the side that transmits the pilot tone signal when the process of selecting the transmission mode between the optical transmitting device 1t and the optical receiving device 2r is performed, and the optical receiving device 2r is the side that receives the pilot tone signal. Therefore, conversely, when the process of selecting the transmission mode between the optical transmitting device 1r and the optical receiving device 2t indicated by the dotted line is performed, the receiving side system R becomes the transmitting side system, and the transmitting side system T becomes the receiving side system.

[0058] (Configuration of Optical Transmitting Device of First Embodiment)

[0059] The optical transmission device 1t of the transmission side system T and the optical transmission device 1r of the reception side system R have the same configuration. Figure 2 The following description will be given by taking the optical transmission device 1t of the transmission-side system T as an example.

[0060] The optical transmission device 1t modulates a main signal of information to be transmitted to generate signal light, and transmits the generated signal light to the optical transmission path 3. Figure 2 As shown, the optical transmission device 1 t has a configuration for transmitting a main signal in parallel using two orthogonal polarized waves (ie, an X-polarized wave and a Y-polarized wave).

[0061] The optical transmission device 1t includes a frame division unit 11t, an error correction coding unit 12t, main signal modulation units 13t-1, 13t-2, multiplexing units 14t-1, 14t-2, electro-optical conversion units 15t-1, 15t-2, polarization wave multiplexing unit 16t, a clock control unit 17t, a control information modulation unit 18t, and a control unit 10t. Figure 2In the figure, the structure including the frame division unit 11t, the error correction coding unit 12t, the main signal modulation unit 13t-1, 13t-2, the multiplexing unit 14t-1, 14t-2, the electro-optical conversion unit 15t-1, 15t-2, the polarization wave multiplexing unit 16t and the clock control unit 17t is called the signal sending unit 110t.

[0062] The frame division unit 11t receives a client signal transmitted from an IP-based device such as an IP (Internet Protocol) router or an Ethernet (registered trademark) switch connected to the optical transmission device 1t, and forms a signal frame including the received client signal. Figure 3 The ITU-T G.709 recommended OTN (Optical Transport Network) frame 40 is shown. The frame section 11 t writes information used for monitoring in the signal frame of the OTN frame 40 into the overhead section 41 , and writes the received client signal into the payload section 42 .

[0063] The error correction coding unit 12t receives the error correction coding designation signal from the control unit 10t, and performs the error correction coding method indicated by the error correction coding designation signal on the signal frame output by the framing unit 11t to generate an error correction code. In addition, the error correction coding unit 12t writes the generated error correction code to the error correction coding unit 43 of the OTN frame 40. For example, Figure 4 As shown, the error correction unit 12t includes an outer error correction coding unit 121t, an inner error correction coding unit 122t, and a main signal separation unit 123t.

[0064] The inner coding error correction coding unit 122t performs coding based on, for example, a soft decision error correction technique. Here, the soft decision error correction technique is a technique for distinguishing signals by multiple thresholds and performing a judgment of likelihood information representing "probability" such as "1 close to 0" or "1 close to 1", which can achieve an error correction capability close to the ideal Shannon limit.

[0065] The outer coding error correction coding unit 121t performs coding based on hard decision error correction technology, for example. Here, hard decision error correction technology is a technology that discriminates a signal with a threshold value and makes a judgment as either a value of 0 or 1. In the soft decision error correction technology performed by the inner coding error correction coding unit 122t, an error floor in which the bit error rate after correction is skewed is easily generated as a price to pay for achieving an error correction capability close to the ideal Shannon limit. Therefore, by removing this error floor using the hard decision error correction technology performed by the outer coding error correction coding unit 121t, a very high error correction capability can be achieved. In this way, a method of using coding based on soft decision error correction technology for inner coding and cascading coding using hard decision error correction technology for outer coding is called a cascade coding method.

[0066] As a soft decision error correction technology, for example, low-density parity check coding (hereinafter referred to as "LDPC" (Low-Density Parity Check)) is applicable. As a hard decision error correction technology, for example, Reed-Solomon (hereinafter referred to as "RS") coding, BCH (Bose-Chaudhuri-Hocquenghem) coding, etc., which are block coding technologies, are applicable. In each of the inner coding error correction coding unit 122t and the outer coding error correction coding unit 121t, the bits can be sorted, i.e., interleaved, to improve the resistance to burst errors. As an example, it can be applied to the bit error rate (hereinafter referred to as "BER" (Bit Error Rate) "10 for BPSK signals. -12 "The NCG (Net Coding Gain) under " is "8.35dB" and the FEC overhead is "6.7%" using RS-FEC error correction technology for encoding.

[0067] In addition, Figure 4 In FIG. 1 , a case where a high error correction capability is required is shown, in which a concatenated coding method including an outer coding error correction coding unit 121t and an inner coding error correction coding unit 122t is applied. In this case, Figure 5 As shown, the outer error correction code 43-1 encoded by the outer error correction coding unit 121t and the inner error correction code 43-2 encoded by the inner error correction coding unit 122t are written to Figure 3 The error correction coding unit 43 of the OTN frame 40 is shown.

[0068] In contrast, when the required error correction capability is not so high, only one party may be provided, for example, only an externally coded error correction coding unit 121t that performs coding using hard decision error correction technology may be provided. In this case, only the externally coded error correction code 43-1 encoded by the externally coded error correction coding unit 121t is written into the error correction coding unit 43.

[0069] In the error correction coding unit 12t, the main signal separation unit 123t converts the serial signal output from the inner coding error correction coding unit 122t into a parallel signal to generate a main signal for an X-polarized wave and a main signal for a Y-polarized wave, which are two binary sequence information. In addition, the main signal separation unit 123t outputs the generated main signal for an X-polarized wave to the main signal modulation unit 13t-1, and outputs the generated main signal for a Y-polarized wave to the main signal modulation unit 13t-2.

[0070] The main signal modulators 13t-1 and 13t-2 each receive a modulation method signal from the control unit 10t, and modulate the main signal for the X-polarized wave and the main signal for the Y-polarized wave, which are the main signals output by the error correction coding unit 12t, based on the modulation method (i.e., mapping rule) indicated by the modulation method signal. In addition, the main signal modulators 13t-1 and 13t-2 generate a transmission symbol sequence by modulation, and output the generated transmission symbol sequence to the multiplexing units 14t-1 and 14t-2 connected to each other. As the modulation method, for example, BPSK (Binary Phase Shift Keying) modulation, QPSK (Quadrature Phase Shift Keying) modulation, QAM (Quadrature Amplitude Modulation) modulation, etc. are applicable. In addition, the applicable modulation method may also be a modulation method other than these modulation methods.

[0071] The X-polarized wave multiplexing unit 14t-1 calls in the transmission symbol sequence for the X-polarized wave output by the main signal modulation unit 13t-1, and calls in the predetermined signal output by the control information modulation unit 18t. Furthermore, the multiplexing unit 14t-1 inserts the called-in predetermined signal into each of the called-in transmission symbol sequences for the X-polarized wave, thereby performing time division multiplexing and generating a signal sequence for the X-polarized wave.

[0072] The multiplexing unit 14t-2 for the Y-polarized wave calls in the transmission symbol sequence for the Y-polarized wave output by the main signal modulation unit 13t-2, and calls in the control signal output by the control information modulation unit 18t. In addition, the multiplexing unit 14t-2 inserts the called-in control signal into each of the called-in transmission symbol sequences for the Y-polarized wave, thereby performing time division multiplexing to generate a signal sequence for the Y-polarized wave.

[0073] The electro-optical converter 15t-1 performs electro-optical conversion on the signal sequence for the X-polarized wave outputted from the multiplexing unit 14t-1, and outputs the optical signal for the X-polarized wave to the polarization wave multiplexing unit 16t. The electro-optical converter 15t-2 performs electro-optical conversion on the signal sequence for the Y-polarized wave outputted from the multiplexing unit 14t-2, and outputs the optical signal for the Y-polarized wave to the polarization wave multiplexing unit 16t.

[0074] The polarization wave multiplexing unit 16t is connected to the multiplexing unit 4T of the optical transmission path 3, and performs polarization wave multiplexing on the optical signals for the X polarization wave and the optical signals for the Y polarization wave outputted from the electro-optical conversion units 15t-1 and 15t-2, thereby generating a signal light that has been time-division multiplexed by polarization wave multiplexing. The polarization wave multiplexing unit 16t sends the generated signal light to the optical transmission path 3. The transmission signal format of the signal light 50 sent out by the polarization wave multiplexing unit 16t is as follows: Figure 6 As shown, time division multiplexing is performed to form Nt (Nt≧1, Nt is a positive integer) control information 45-1 to 45-Nt between Ns (Ns≧1, Ns is a positive integer) main signal information 40-1 to 40-Ns as the transmission symbol sequence. In addition, the control information 45-1 to 45-Nt is a predetermined signal in the X-polarized wave of the signal light 50, and is a control signal in the Y-polarized wave of the signal light 50.

[0075] The clock control unit 17t receives a baud rate control signal from the control unit 10t, and sets the clock frequency of the clock provided inside the optical transmission device 1t so that the baud rate of the main signal becomes the baud rate specified by the baud rate control signal. For example, if the clock control unit 17t receives a baud rate control signal from the control unit 10t to set the baud rate of the main signal to 32GBaud, the clock frequency is set to the baud rate. In addition, if the clock control unit 17t receives a baud rate control signal to change the baud rate of the main signal from 32GBaud to 64GBaud, the baud rate of the main signal is set to 64GBaud by overclocking (Clock up). In addition, if the clock control unit 17t receives a baud rate control signal to change the baud rate of the main signal from 64GBaud to 32GBaud, the baud rate of the main signal is set to 32GBaud by downclocking (Clock down).

[0076] The control unit 10t includes a transmission mode information storage unit 100t, a transmission mode candidate sending unit 101t, a transmission mode candidate receiving unit 102t, and a transmission mode selecting unit 103t. Figure 7The transmission mode information is explained. The transmission mode information is information that combines various parameters related to transmission performance, such as modulation method, baud rate, and error correction coding type. Figure 7 The transmission mode information table 1000 shown shows, for example, 24 types of transmission mode information composed of combinations of parameters of six modulation methods, two baud rates, and two error correction coding types. In this example, the transmission capacity in each of the 24 types of combinations is also described in the transmission mode information. Each transmission mode information is assigned a transmission mode number such as "mode 1" or "mode 2" as shown in the "transmission mode" item.

[0077] like Figure 7 As shown in the "Modulation Mode" item, the six modulation modes are BPSK, QPSK, 8QAM, 16QAM, 32QAM, and 64QAM. As shown in the "Baud Rate" item, the two baud rates are 32GBaud and 64GBaud. As shown in the "Error Correction Code Type" item, there are two error correction code types, one is RS-LDPC concatenated code FEC, which combines Reed Solomon (RS) coding on the outer coding and low-density parity check coding (LDPC) on the inner coding. The other is BCH coding on the outer coding and low-density parity check coding (LDPC) on the inner coding. Concatenated code FEC of BCH-LDPC.

[0078] Each of the optical transmitting device 1t and the optical receiving device 2r stores in advance Figure 7 The table is composed of data such as the transmission mode information table 1000 shown in the figure, so that if only the transmission mode number is sent and received between the optical transmitting device 1t and the optical receiving device 2r, each device can refer to the table and specifically specify the modulation method, baud rate, and error correction coding category. For example, in the case of "Mode 5", the modulation method can be specifically specified as QPSK, the baud rate can be specifically specified as 32GBaud, and the error correction coding category can be specifically specified as RS+LDPC. In the case of "Mode 16", the modulation method can be specifically specified as 16QAM, the baud rate can be specifically specified as 64GBaud, and the error correction coding category can be specifically specified as BCH+LDPC. In addition, the information stored in the transmission mode information table 1000 will not be as Figure 7 The number of limited to 24 types may be changed appropriately with the advancement of technology or the addition of new functions. For example, more than 24 types of modes may be set in the transmission mode information table 1000 by combining the three types of modulation method, baud rate, and error correction coding type, or additional information other than the three types of modulation method, baud rate, and error correction coding type may be added.

[0079] In the control unit 10t, the transmission mode information storage unit 100t stores, for example, Figure 8The data shown in FIG. 1001 is a transmission side transmission mode information table 1001t. The transmission side transmission mode information table 1001t stores transmission mode information that can be transmitted in the optical transmission device 1t. Figure 8 Shown in Figure 7 The transmission mode information table 1000 shown is an example of a transmission side transmission mode information table 1001t which stores transmission mode information whose error correction coding type is RS+LDPC as a function possessed by the transmission side.

[0080] The transmission mode candidate transmitting unit 101t generates transmission side transmission mode candidate information as transmission information, the transmission side transmission mode candidate information including all transmission mode numbers stored in the item "Transmission Mode" of the transmission side transmission mode information table 1001t stored in the transmission mode information storage unit 100t. In addition, if information is supplied from the outside, the transmission mode candidate transmitting unit 101t calls the supplied information as transmission information.

[0081] In addition, the transmission mode candidate transmitting unit 101t uses the transmission information as a signal sequence, differentially encodes the signal sequence for each bit, and outputs the differentially encoded signal to the control information modulating unit 18t. In addition, the transmission mode candidate transmitting unit 101t generates a signal sequence in which power is concentrated on one or more specific frequencies, and outputs the generated signal sequence as a predetermined signal to the control information modulating unit 18t.

[0082] The transmission mode candidate receiving unit 102t receives reception-side transmission mode candidate information including a transmission mode number indicating transmission mode information that can be transmitted in the light receiving unit 2r of the reception-side system R from the light receiving unit 2t of the transmission-side system T. The reception-side transmission mode candidate information of the light receiving unit 2r of the reception-side system R is information that the light receiving unit 2r of the reception-side system R transmits to the light transmitting unit 1r and the light transmitting unit 1r transmits to the light receiving unit 2t of the transmission-side system T via the optical transmission path 3. In addition, the transmission mode candidate receiving unit 102t outputs the received reception-side transmission mode candidate information to the transmission mode selecting unit 103t.

[0083] The transmission mode selection unit 103t extracts a common transmission mode number from all transmission mode numbers stored in the "Transmission Mode" item of the transmission side transmission mode information table 1001t stored in the transmission mode information storage unit 100t and the reception side transmission mode candidate information output by the transmission mode candidate reception unit 102t.

[0084] In addition, the transmission mode selection unit 103t selects the transmission mode number with the highest priority among the extracted common transmission mode numbers. Here, the priority is information indicating a predetermined priority level, for example, a transmission mode information including a modulation method with a higher multi-value degree and a higher baud rate becomes a transmission mode information with a higher priority. Figure 7 In the transmission mode information shown in the transmission mode information table 1000 shown in FIG. 1 , a transmission mode number having a large transmission capacity (high multi-value degree and high baud rate) has a high priority.

[0085] In addition, the transmission mode selection unit 103t has a storage area inside, and writes the selected transmission mode number into the internal storage area to store it. In addition, the transmission mode selection unit 103t performs the following processing. For example, when the notification included in the notification signal is a signal quality non-permit notification, the transmission mode selection unit 103t refers to the internal storage area and selects the transmission mode number of the transmission mode information with the second highest priority among the transmission mode information selected at that time. The notification signal is transmitted inline from the optical transmission device 1r of the receiving side system R to the optical receiving device 2t of the transmitting side system T without passing through an external loop.

[0086] In addition, the transmission mode selection unit 103t reads out the information on the modulation method of the item "Modulation method", the value of the baud rate of the item "Baud rate", and the information on the error correction coding method of the item "Error correction coding type" of the transmission mode information corresponding to the selected transmission mode number. In addition, the transmission mode selection unit 103t generates a modulation method signal including the information indicating the modulation method read out, and outputs it to the main signal modulation units 13t-1 and 13t-2. In addition, the transmission mode selection unit 103t generates a baud rate control signal including the value of the baud rate read out, and outputs it to the clock control unit 17t. In addition, the transmission mode selection unit 103t outputs an error correction coding designation signal including the information indicating the error correction coding method read out to the error correction coding unit 12t.

[0087] The control information modulation unit 18t receives the predetermined signal and the differential coded signal outputted from the transmission mode candidate transmission unit 101t, modulates the predetermined signal using the differential coded signal, and generates a control signal. In addition, the control information modulation unit 18t outputs the predetermined signal to the multiplexing unit 14t-1 for the X-polarized wave, and outputs the control signal to the multiplexing unit 14t-2 for the Y-polarized wave.

[0088] The predetermined signal and the control signal are time-division multiplexed with the main signal by the multiplexing units 14t-1 and 14t-2, and then converted into optical signals by the electro-optical converters 15t-1 and 15t-2. The signal generated by polarization-wave multiplexing of the predetermined signal and the control signal optical signal by the polarization-wave multiplexing unit 16t becomes a pilot tone signal which is a signal sequence with power concentrated at one or more specific frequencies.

[0089] Furthermore, the control information modulation unit 18t may output the control signal to the multiplexing unit 14t-1 for the X-polarized wave and the predetermined signal to the multiplexing unit 14t-2 for the Y-polarized wave in the opposite manner to the above configuration. In this case, the control information 45-1 to 45-Nt becomes the control signal in the X-polarized wave of the signal light 50 and becomes the predetermined signal in the Y-polarized wave of the signal light 50.

[0090] (Configuration of Light Receiving Device of First Embodiment)

[0091] The light receiving device 2r of the receiving system R and the light receiving device 2t of the transmitting system T have the same configuration. Fig. 9 The following description will be given taking the optical receiving device 2r of the receiving-side system R as an example.

[0092] The optical receiving device 2r receives the signal light transmitted from the optical transmitting device 1t and transmitted through the optical transmission path 3. The optical receiving device 2r performs coherent reception of the received signal light using a local oscillation laser provided inside, and demodulates the original signal from the signal light.

[0093] The light receiving device 2r has Fig. 9 The internal structure shown in the figure includes a polarization wave separation unit 21r, photoelectric conversion units 22r-1, 22r-2, AD (Analog-to-Digital) conversion units 23r-1, 23r-2, main signal demodulation units 24r-1, 24r-2, error correction decoding unit 25r, deframing unit 26r, clock control unit 27r, control information demodulation unit 210r and control unit 20r. In addition, Fig. 9 In the figure, the structure including the polarization wave separation unit 21r, the photoelectric conversion unit 22r-1, 22r-2, the AD conversion unit 23r-1, 23r-2, the main signal demodulation unit 24r-1, 24r-2, the error correction decoding unit 25r, the deframing unit 26r and the clock control unit 27r is called the signal receiving unit 220r.

[0094] The polarization separation unit 21r is connected to the multiplexing unit 4R of the optical transmission path 3, and receives the signal light sent by the optical transmission device 1t and transmitted by the optical transmission path 3. The signal light is a signal light in which the time-division multiplexed signal is polarization-multiplexed as described above. In addition, the polarization separation unit 21r performs polarization separation in the optical region on the received signal light, separates it into two orthogonal X-polarized waves and Y-polarized waves, and outputs each of the separated X-polarized waves and Y-polarized waves to the photoelectric conversion units 22r-1 and 22r-2.

[0095] Specifically, the polarization separation unit 21r includes, for example, a polarization diversity 90-degree hybrid coupler and a local oscillation laser, and performs polarization separation using these devices. The polarization separation unit 21r outputs the separated X polarization wave to the photoelectric conversion unit 22r-1, and outputs the separated Y polarization wave to the photoelectric conversion unit 22r-2.

[0096] The photoelectric converter 22r-1 on the X-polarized wave side takes in the signal light of the X-polarized wave output from the polarized wave separation section 21r, converts it into an electrical analog signal, and outputs the converted electrical analog signal to the AD converter 23r-1. The photoelectric converter 22r-2 on the Y-polarized wave side takes in the signal light of the Y-polarized wave output from the polarized wave separation section 21r, converts it into an electrical analog signal, and outputs the converted electrical analog signal to the AD converter 23r-2.

[0097] Each of the AD converters 23r-1 and 23r-2 converts the electrical analog signal output by the photoelectric converters 22r-1 and 22r-2 connected to each other into a digital signal, thereby generating a digital reception signal. In addition, each of the AD converters 23r-1 and 23r-2 outputs the generated digital reception signal to the main signal demodulators 24r-1 and 24r-2 connected to each other. In addition, the AD converters 23r-1 and 23r-2 output the generated digital reception signal to the control information demodulator 210r and the control unit 20r.

[0098] The main signal demodulation units 24r-1 and 24r-2 receive the modulation method signal from the control unit 20r, and demodulate the main signal included in the digital reception signal output by the AD conversion units 23r-1 and 23r-2 connected to them respectively according to the demodulation method corresponding to the modulation method indicated by the modulation method signal, that is, the demapping rule. The main signal demodulated by the main signal demodulation unit 24r-1 becomes the main signal corresponding to the signal light of the X-polarized wave, and the main signal demodulated by the main signal demodulation unit 24r-2 becomes the main signal corresponding to the signal light of the Y-polarized wave.

[0099] The error correction decoding unit 25r receives the error correction code designation signal from the control unit 20r, and performs decoding processing corresponding to the error correction coding method indicated by the error correction code designation signal on the main signal demodulated by the main signal demodulation units 24r-1 and 24r-2. The error correction code used by the error correction decoding unit 25r when performing the decoding processing may also use the error correction code information included in the error correction code unit 43 of the OTN frame 40 of the main signal.

[0100] The error correction decoding unit 25r corresponds to the outer error correction coding unit 121t and the inner error correction coding unit 122t included in the error correction coding unit 12t of the optical transmission device 1t. Fig.10 As shown, the optical transmission device 1t includes an inner coding error correction decoding unit 251r and an outer coding error correction decoding unit 252r. The inner coding error correction decoding unit 251r performs decoding using, for example, a soft decision error correction technique of LDPC, and the outer coding error correction decoding unit 252r performs decoding using, for example, a hard decision error correction technique such as RS-FEC or BCH-FEC. In addition, when the error correction coding unit 12t of the optical transmission device 1t includes only the outer coding error correction coding unit 121t, the error correction decoding unit 25r also includes only the outer coding error correction decoding unit 252r.

[0101] In the error correction decoding unit 25r, the main signal synthesis unit 253r converts a parallel signal consisting of a main signal corresponding to the signal light of the X-polarized wave output by the main signal demodulation unit 24r-1 and a main signal corresponding to the signal light of the Y-polarized wave output by the main signal demodulation unit 24r-2 into a serial signal and outputs it to the inner coding error correction decoding unit 251r.

[0102] The de-framing unit 26r Figure 3 The payload portion 42 of the illustrated OTN frame 40 reads out the client signal, and outputs the read out client signal to an IP-based device such as an IP router or an Ethernet (registered trademark) switch connected to the optical receiving device 2 r.

[0103] The clock control unit 27r receives a baud rate control signal from the control unit 20r, and sets the clock frequency of the clock of the optical receiving device 2r so that the baud rate when receiving the main signal becomes the baud rate specified by the baud rate control signal. For example, if the clock control unit 27r receives a baud rate control signal from the control unit 20r to set the baud rate to 32GBaud, the clock frequency is set to the baud rate. In addition, if the clock control unit 27r receives a baud rate control signal to change the baud rate from 32GBaud to 64GBaud, the baud rate is set to 64GBaud by overclocking, that is, increasing the clock frequency. In addition, if the clock control unit 27r receives a baud rate control signal to change the baud rate from 64GBaud to 32GBaud, the baud rate is set to 32GBaud by downclocking, that is, decreasing the clock frequency.

[0104] The control information demodulation unit 210r includes a control information detection unit 211r, control information extraction units 212r-1, 212r-2, and a differential decoding unit 213r. In the control information demodulation unit 210r, the control information detection unit 211r receives a digital reception signal in which the main signal information and the control information are time-division multiplexed, which is output from each of the AD conversion units 23r-1, 23r-2, and detects a specific frequency of the pilot tone signal from the received digital reception signal. Figure 6 The positions of the control information 45-1, 45-2, ..., 45-Nt included in the signal light 50 shown. In addition, the specific frequency of the pilot tone signal transmitted by the optical transmitting device 1t is supplied to the optical receiving device 2r in advance. In addition, the control information detection unit 211r outputs the detected positions of the control information 45-1, 45-2, ..., 45-Nt to the control information extraction units 212r-1, 212r-2 as timing information.

[0105] Furthermore, as described above, since the control information 45-1 to 45-Nt is a predetermined signal in the X-polarized wave and a control signal in the Y-polarized wave, the control information of the digital received signal output by the AD converter 23r-1 includes the predetermined signal, and the control information of the digital received signal output by the AD converter 23r-2 includes the control signal.

[0106] Each of the control information extraction units 212r-1 and 212r-2 detects a section including the control information 45-1, 45-2, ..., 45-Nt from the digital reception signal output by the AD conversion units 23r-1 and 23r-2 connected to the respective ones based on the timing information output by the control information detection unit 211r, and outputs the signal of the detected section to the differential decoding unit 213r. The differential decoding unit 213r performs differential decoding processing using the signals output by the control information extraction units 212r-1 and 212r-2, thereby generating a differential decoded signal, and outputs the generated differential decoded signal to the control unit 20r.

[0107] The control unit 20r includes a transmission mode information storage unit 200r, a transmission mode candidate receiving unit 201r, a transmission mode candidate sending unit 202r, a transmission mode selecting unit 203r, a signal quality detecting unit 204r, and a signal quality determining unit 205r.

[0108] In the control unit 20r, the transmission mode information storage unit 200r stores in advance Fig.11 The receiving side transmission mode information table 2001r is composed of the data shown in FIG. The receiving side transmission mode information table 2001r stores the transmission mode information that can be transmitted in the optical receiving device 2r. Fig.11 Shown in Figure 7The transmission mode information table 1000 shown is an example of a receiving side transmission mode information table 2001r storing transmission mode information with transmission mode numbers "mode 1", "mode 5", "mode 9" and "mode 13".

[0109] The transmission mode candidate receiving unit 201r demodulates the differential decoded signal output by the differential decoder 213r and obtains the transmission side transmission mode candidate information of the optical transmission device 1t from the differential decoded signal. In addition, the transmission mode candidate receiving unit 201r outputs the obtained transmission side transmission mode candidate information to the transmission mode selection unit 203r. In addition, if the transmission mode candidate receiving unit 201r obtains the transmission side transmission mode candidate information, it outputs a reception side transmission mode candidate information transmission instruction signal for transmitting the reception side transmission mode candidate information to the transmission mode candidate transmitting unit 202r.

[0110] When the transmission mode candidate sending unit 202r receives the receiving side transmission mode candidate information sending instruction signal from the transmission mode candidate receiving unit 201r, it generates the receiving side transmission mode candidate information including all the transmission mode numbers stored in the "transmission mode" item of the receiving side transmission mode information table 2001r stored in the transmission mode information storage unit 200r.

[0111] Furthermore, the transmission mode candidate transmitting unit 202r is connected to the transmission mode candidate transmitting unit 101r of the optical transmitting device 1r of the receiving system R, and transmits the generated receiving-side transmission mode candidate information to the transmission mode candidate transmitting unit 101r of the optical transmitting device 1r. Furthermore, after transmitting the generated receiving-side transmission mode candidate information to the transmission mode candidate transmitting unit 101r of the optical transmitting device 1r, the transmission mode candidate transmitting unit 202r outputs a signal quality detection instruction signal for detecting signal quality to the signal quality detecting unit 204r.

[0112] The transmission mode selector 203r extracts a common transmission mode number from all transmission mode numbers stored in the "Transmission Mode" item of the reception side transmission mode information table 2001r stored in the transmission mode information storage unit 200r and the transmission side transmission mode candidate information of the optical transmission device 1t output by the transmission mode candidate receiver 201r.

[0113] In addition, the transmission mode selection unit 203r selects the transmission mode number with the highest priority among the extracted common transmission mode numbers. In addition, the priority that becomes the reference when the transmission mode selection unit 203r selects is the same as the priority of the transmission mode selection unit 103t of the optical transmission device 1t. Therefore, the transmission mode number selected by the transmission mode selection unit 203r according to the priority and the transmission mode number selected by the transmission mode selection unit 103t of the optical transmission device 1t according to the priority become the same transmission mode number.

[0114] In addition, the transmission mode selection unit 203r has a storage area inside, and writes the selected transmission mode number into the internal storage area to store it. In addition, when the transmission mode selection unit 203r receives a notification signal from the signal quality determination unit 205r, if the notification included in the notification signal is a signal quality non-permit notification, the transmission mode number of the transmission mode information with the next highest priority among the transmission mode information selected at that time is selected by referring to the internal storage area.

[0115] In addition, the transmission mode selection unit 203r reads out the information of the modulation method of the item "Modulation method", the value of the baud rate of the item "Baud rate", and the information of the error correction coding method of the item "Error correction coding type" of the transmission mode information corresponding to the selected transmission mode number. In addition, the transmission mode selection unit 203r generates a modulation method signal including the information indicating the modulation method read out and outputs it to the main signal demodulation units 24r-1 and 24r-2. In addition, the transmission mode selection unit 203r generates a baud rate control signal including the value of the baud rate read out and outputs it to the clock control unit 27r. In addition, the transmission mode selection unit 203r outputs an error correction coding designation signal including the information indicating the error correction coding method read out to the error correction decoding unit 25r.

[0116] When the transmission mode information is newly selected in the optical transmission device 1t, the signal quality detection unit 204r detects the signal quality of the signal light transmitted by the optical transmission device 1t according to the newly selected transmission mode.

[0117] The signal quality detection unit 204r has a flag area inside, and the initial value of the flag is "OFF". In addition, if the signal quality detection unit 204r receives a signal quality detection instruction signal from the transmission mode candidate sending unit 202r, the flag is set to "ON". In addition, the signal quality detection unit 204r detects the signal quality in the state where the flag is "ON". In addition, the signal quality detection unit 204r may not use a flag. In this case, if the signal quality detection unit 204r receives a signal quality detection instruction signal, the pilot tone signal is used to detect the OSNR from the control information based on the timing information detected by the control information detection unit 211r.

[0118] The signal quality detection unit 204r detects a signal-to-noise ratio (hereinafter referred to as "SN" (Signal-to-Noise) ratio) based on the strength of a specific frequency of the pilot tone signal, for example, and uses the detected signal-to-noise ratio as information indicating signal quality. In addition, the information indicating signal quality is not limited to the SN ratio, and the strength of the specific frequency itself may be used as information indicating signal quality. In addition, the bit error rate (BER) may be used as information indicating signal quality. In addition, the signal quality detection unit 204r is connected to the two output ends of the polarization wave separation unit 21r, and the optical signal-to-noise ratio (hereinafter referred to as "OSNR" (Optical Signal-to-Noise Ratio)) is detected based on the optical signal obtained from the output end, and the detected OSNR may be used as information indicating signal quality.

[0119] In addition, the signal quality detection unit 204r may use information obtained from measuring instruments such as OTDR (Optical Time Domain Reflectometers), spectrum analyzers, and power meters as a signal quality detection method. The signal degradation position can be specifically specified or the signal quality detection can be made more accurate by the information obtained from the measuring instrument, and information that cannot be obtained only by the existing optical transmission system can be obtained. In this case, the measuring instrument may be prepared separately from the optical transmission system S, or the optical transmission system S may be provided with a measuring function.

[0120] In addition, the signal quality detection unit 204r outputs information indicating the detected signal quality to the signal quality determination unit 205r and sets the flag to "OFF". In addition, when the flag is "OFF", the signal quality detection unit 204r does not detect the signal quality when receiving the output from the control information detection unit 211r. This is because it is not a digital reception signal when the transmission mode is newly selected in the optical transmission device 1t.

[0121] The signal quality determination unit 205r determines whether the signal quality is an allowable quality based on information indicating the signal quality detected by the signal quality detection unit 204r and a threshold value predetermined according to the detected signal quality.

[0122] Furthermore, when the signal quality is determined to be acceptable, the signal quality determination unit 205r transmits a notification signal of signal quality acceptance notification inline to the optical receiving device 2t of the transmitting system T via the optical transmitting device 1r of the receiving system R. Furthermore, the signal quality determination unit 205r outputs the notification signal of signal quality acceptance notification to the transmission mode selection unit 203r.

[0123] Furthermore, when the signal quality is determined to be an unacceptable quality, the signal quality determination unit 205r transmits a notification signal of signal quality unacceptable notification inline to the optical receiving device 2t of the transmitting system T via the optical transmitting device 1r of the receiving system R. Furthermore, the signal quality determination unit 205r outputs the notification signal of signal quality unacceptable notification to the transmission mode selection unit 203r.

[0124] (Regarding the Optical Transmitting Device 1r of the Receiving-Side System R)

[0125] As described above, the optical transmission device 1r of the receiving system R has the same configuration as the optical transmission device 1t of the transmitting system T. Therefore, in the following description, when illustrating each functional unit of the optical transmission device 1r, the English letter "t" is replaced with "r". For example, when illustrating the transmission mode selection unit of the optical transmission device 1r, it is illustrated as "transmission mode selection unit 103r".

[0126] In addition, as described above, the optical transmission device 1r of the receiving system R receives the receiving side transmission mode candidate information transmitted by the optical receiving device 2r. Furthermore, the optical transmission device 1r transmits the received receiving side transmission mode candidate information of the optical receiving device 2r to the optical receiving device 2t of the transmitting system T via the optical transmission path 3. Fig.12 As shown, the transmission mode candidate transmitter 101r of the optical transmitter 1r of the receiving system R is connected to the transmission mode candidate transmitter 202r of the optical receiver 2r. Then, the transmission mode candidate transmitter 101r receives the receiving side transmission mode candidate information of the optical receiver 2r transmitted by the transmission mode candidate transmitter 202r of the optical receiver 2r.

[0127] The transmission mode candidate transmitting unit 101r of the optical transmitting device 1r calls in the received reception-side transmission mode candidate information of the optical receiving device 2r as transmission information. The transmission mode candidate transmitting unit 101r of the optical transmitting device 1r uses the transmission information as a signal sequence, differentially encodes the signal sequence for each bit, and outputs the differentially encoded signal to the control information modulating unit 18r. In addition, the transmission mode candidate transmitting unit 101r generates a signal sequence in which power is concentrated at one or more specific frequencies, and outputs the generated signal sequence as a predetermined signal to the control information modulating unit 18r. As a result, the reception-side transmission mode candidate information of the optical receiving device 2r is superimposed on the pilot tone signal and transmitted to the optical receiving device 2t of the transmission-side system T through the optical transmission path 3.

[0128] (Regarding the Light Receiving Device 2t of the Transmitting-Side System T)

[0129] As described above, the optical receiving device 2t of the transmission side system T has the same configuration as the optical receiving device 2r of the reception side system R. Therefore, in the following description, when illustrating each functional unit of the optical receiving device 2t, the English letter "r" is replaced with "t". For example, when illustrating the transmission mode selection unit of the optical receiving device 2t, it is illustrated as "transmission mode selection unit 203t".

[0130] In addition, as described above, the optical receiving device 2t of the transmission side system T receives the reception side transmission mode candidate information of the optical receiving device 2r transmitted by the optical transmitting device 1r of the reception side system R. Then, the optical receiving device 2t transmits the received reception side transmission mode candidate information of the optical receiving device 2r to the optical transmitting device 1t of the transmission side system T. Therefore, Fig.13 As shown, the transmission mode candidate receiving section 201t of the optical receiving device 2t of the transmission-side system T is connected to the transmission mode candidate receiving section 102t of the optical transmitting device 1t.

[0131] The transmission mode candidate receiving unit 201t of the optical receiving device 2t demodulates the differential decoded signal output by the differential decoder 213t and acquires the receiving side transmission mode candidate information of the optical receiving device 2r from the differential decoded signal. Then, the transmission mode candidate receiving unit 201t transmits the acquired receiving side transmission mode candidate information of the optical receiving device 2r to the transmission mode candidate receiving unit 102t of the optical transmitting device 1t. Thus, the transmission mode candidate receiving unit 102t of the optical transmitting device 1t of the transmitting side system T can acquire the receiving side transmission mode candidate information of the optical receiving device 2r of the receiving side system R.

[0132] (Transmission Mode Selection Process in First Embodiment)

[0133] Fig.14 1 is a flowchart showing the flow of the transmission mode selection process performed by the optical transmission system S according to the first embodiment. The dotted arrows indicate the transmission and reception of information between the optical transmission device 1 t and the optical reception device 2 r.

[0134] (Processing of Step ST1 by the Optical Transmitting Device 1 t)

[0135] The transmission mode candidate transmitting unit 101t of the control unit 10t of the optical transmission device 1t starts processing upon receiving an operation by a user or at the timing of starting the optical transmission device 1t. The transmission mode candidate transmitting unit 101t generates transmission-side transmission mode candidate information including all transmission mode numbers stored in the item "Transmission Mode" of the transmission-side transmission mode information table 1001t stored in the transmission mode information storage unit 100t.

[0136] The transmission mode candidate transmitting unit 101t uses the generated transmission side transmission mode candidate information as a signal sequence, performs differential encoding on the signal sequence for each bit, and outputs the differential encoding signal to the control information modulating unit 18t. The transmission mode candidate transmitting unit 101t generates a signal sequence in which power is concentrated on one or more specific frequencies, and outputs the generated signal sequence as a predetermined signal to the control information modulating unit 18t.

[0137] Here, the differential coding performed by the transmission mode candidate transmission unit 101t is described. In differential coding, when the setting information of the nth (n≧0, n is an integer) is set to C(n) (C(n) is two values ​​of 1 or 0), as shown in the following formula (1), the nth output (differential coding signal) D(n) is represented by the exclusive logical sum of C(n) and D(n-1). However, in formula (1), D(-1)=1.

[0138] [Number 1]

[0139]

[0140] Next, a predetermined signal (i.e., a signal sequence in which power is concentrated at a specific frequency) is described. As a signal sequence in which power is concentrated at a specific frequency, for example, an alternating signal that is point-symmetrical with respect to the origin on the IQ plane can be used. As an example, when generating a BPSK signal, an alternating signal that alternately repeats two signal points such as -S, S, -S, S, ..., -S, S can be used.

[0141] In addition, when generating a QPSK signal, if the signal point is represented as (real part, imaginary part), an alternating signal that alternately repeats two signal points such as (S, S), (-S, -S), (S, S), (-S, -S), ..., (S, S), (-S, -S) or (S, -S), (-S, S), (S, -S), (-S, S), ..., (S, -S), (-S, S) can be used. Here, S represents an arbitrary real number. In addition, (real part α, imaginary part β) can be represented as a complex number as α+jβ. However, j is an imaginary unit. The alternating signal can generate power of a specific frequency concentrated in two places.

[0142] In addition, an alternating signal in which one signal is repeated twice, such as -S, -S, S, -S, -S, S, S, ..., -S, -S, S, S, S, or an alternating signal in which each signal is repeated M times (a positive number M>0) may be used. In this way, power can be concentrated at more than four specific frequencies by multiplying or convolving the alternating signal that is repeated multiple times. In addition, a signal in which power is concentrated at more than two specific frequencies can be generated by overlapping multiple sinusoidal waves with different periods. In addition, a signal with a specific frequency can be generated by using an orthogonal frequency division multiplexing (OFDM) method to overlap only a signal on a specific subcarrier. Moreover, the frequency band in which power is concentrated can be expanded by using a specific frequency band signal sequence and another signal sequence for diffusion.

[0143] The control information modulation unit 18t receives the predetermined signal and the differential coded signal output by the transmission mode candidate transmission unit 101t, and modulates the predetermined signal using the differential coded signal to generate a control signal. Specifically, when the predetermined signal output by the transmission mode candidate transmission unit 101t is -S, S, -S, S, ..., -S, S, and when the differential coded signal is D(n) = 1, the control information modulation unit 18t outputs -S, S, -S, S, ..., -S, S as the control signal. In addition, when the differential coded signal is D(n) = 0, the control information modulation unit 18t inverts the sign and outputs S, -S, S, -S, ..., S, -S as the control signal. In addition, with respect to D(n)=1 and D(n)=0, the inversion of the sign can also be opposite, that is, when D(n)=1, the output is S, -S, S, -S, ..., S, -S, and when D(n)=0, the output is -S, S, -S, S, ..., -S, S.

[0144] The control information modulation unit 18t outputs a predetermined signal to the multiplexing unit 14t-1 for the X-polarized wave, and outputs a control signal to the multiplexing unit 14t-2 for the Y-polarized wave. The multiplexing unit 14t-1 for the X-polarized wave inserts the predetermined signal output by the control information modulation unit 18t into each transmission symbol sequence for the X-polarized wave output by the main signal modulation unit 13t-1, thereby performing time division multiplexing to generate a signal sequence for the X-polarized wave. The multiplexing unit 14t-2 for the Y-polarized wave inserts the control signal output by the control information modulation unit 18t into each transmission symbol sequence for the Y-polarized wave output by the main signal modulation unit 13t-2, thereby performing time division multiplexing to generate a signal sequence for the Y-polarized wave.

[0145] Each of the electro-optical converters 15t-1 and 15t-2 electro-optically converts the X-polarized wave and Y-polarized wave signal sequences output by the multiplexing units 14t-1 and 14t-2, and outputs the X-polarized wave and Y-polarized wave optical signals to the polarized wave multiplexing unit 16t.

[0146] The polarization wave multiplexing unit 16t performs polarization wave multiplexing on the optical signal for the X polarization wave and the optical signal for the Y polarization wave outputted by each of the electro-optical conversion units 15t-1 and 15t-2, thereby generating a signal light which is time-division multiplexed by polarization wave multiplexing. At this time, when the above-mentioned differential coded signal is D(n)=0, the control information in the signal outputted from one polarization wave becomes a signal which inverts the phase of the control information of the other polarization wave.

[0147] The polarization wave multiplexing unit 16t sends the generated signal light to the optical transmission path 3. Thus, the signal light including the pilot tone signal superimposed with the transmission side transmission mode candidate information of the optical transmission device 1t is transmitted through the optical transmission path 3 to the optical reception device 2r.

[0148] (Processing of Step SR1 by the Light Receiving Device 2r)

[0149] The polarization separation unit 21r of the optical receiving device 2r receives the signal light including the pilot tone signal transmitted through the optical transmission path 3. The polarization separation unit 21r performs polarization separation in the optical region on the received signal light, separates it into two orthogonal X-polarized waves and Y-polarized waves, and outputs the separated X-polarized waves and Y-polarized waves to the photoelectric conversion units 22r-1 and 22r-2. Each of the photoelectric conversion units 22r-1 and 22r-2 takes in the signal light of the X-polarized waves and the Y-polarized waves output by the polarization separation unit 21r, converts them into electrical analog signals, and outputs the converted electrical analog signals to the corresponding AD conversion units 23r-1 and 23r-2.

[0150] The AD converters 23r-1 and 23r-2 convert the electrical analog signals outputted by the photoelectric converters 22r-1 and 22r-2 connected to them into digital signals, thereby generating digital reception signals, and output the generated digital reception signals to the main signal demodulators 24r-1 and 24r-2 connected to them. The AD converters 23r-1 and 23r-2 output the generated digital reception signals to the control information detector 211r and the control information extractors 212r-1 and 212r-2 of the control information demodulator 210r.

[0151] The control information detection unit 211r receives the time-division multiplexed digital reception signals output by the AD conversion units 23r-1 and 23r-2, and detects the specific frequency of the known pilot tone signal from the received digital reception signals. Figure 6The positions of control information 45 - 1 , 45 - 2 , . . . , 45 -Nt included in the signal light 50 are shown.

[0152] As a method for detecting the position of the control information 45-1, 45-2, ..., 45-Nt, for example, there is a method in which the control information detection unit 211r detects the position where the power is concentrated at a specific frequency in the digital reception signal as the insertion position of the control information 45-1, 45-2, ..., 45-Nt. The position where the power is concentrated is, for example, a position where the signal power of the specific frequency of the digital reception signal is calculated and the calculated signal power exceeds a predetermined threshold or a position where the signal power exceeding the predetermined threshold is the largest. The control information detection unit 211r outputs the detected position to the control information extraction units 212r-1 and 212r-2 as timing information.

[0153] Each of the control information extraction units 212r-1 and 212r-2 detects an interval including control information 45-1, 45-2, ..., 45-Nt from the digital received signals output by the respectively connected AD conversion units 23r-1 and 23r-2 based on the timing information output by the control information detection unit 211r, and outputs the signal of the detected interval to the differential decoding unit 213r.

[0154] The differential decoding unit 213r performs differential decoding processing using the signals output by the control information extraction units 212r-1 and 212r-2, generates a differential decoded signal, and outputs the generated differential decoded signal to the transmission mode candidate receiving unit 201r. For example, if the output signals of the control information extraction units 212r-1 and 212r-2 in the nth frame are respectively Rx(n, k) and Ry(n, k), the differential decoded signal Z(n) is expressed by the following equation (2).

[0155] [Number 2]

[0156]

[0157] However, in equation (2), “*” represents a complex conjugate. Also, “K” represents the length of the digital reception signal stored in each buffer of the control information extraction units 212 r - 1 and 212 r - 2 , and K>k≧0.

[0158] The transmission mode candidate receiving unit 201r receives the differential decoded signal output by the differential decoder 213r, demodulates the received differential decoded signal, and obtains the transmission mode candidate information of the optical transmitter 1t from the differential decoded signal. Here, if the differential decoded signal in the nth frame is Z(n), the determination result P(n) is expressed by the following formula (3). However, in formula (3), the Pth (>0) is the determination threshold.

[0159] [Number 3]

[0160]

[0161] The modulation and demodulation method performed by the control information modulation unit 18t, the control information demodulation unit 210r, and the transmission mode candidate receiving unit 201r described above does not depend on the modulation method. Therefore, since the transmission mode is not determined, even in a communication environment where the modulation method of the main signal of the signal light transmitted by the optical transmission device 1t cannot be identified in the optical receiving device 2r, the transmission side transmission mode candidate information of the optical transmission device 1t can be transmitted.

[0162] The transmission mode candidate receiving unit 201r outputs the acquired transmission side transmission mode candidate information of the optical transmission device 1t to the transmission mode selecting unit 203r. When the transmission mode candidate receiving unit 201r acquires the transmission side transmission mode candidate information of the optical transmission device 1t, it outputs a reception side transmission mode candidate information transmission instruction signal for transmitting the reception side transmission mode candidate information to the transmission mode candidate transmitting unit 202r.

[0163] (Processing of Step SR2 by the Light Receiving Device 2r)

[0164] When receiving the receiving-side transmission mode candidate information transmission instruction signal from the transmission mode candidate receiving unit 201r, the transmission mode candidate transmitting unit 202r generates the receiving-side transmission mode candidate information including all the transmission mode numbers stored in the item "Transmission Mode" of the receiving-side transmission mode information table 2001r stored in the transmission mode information storage unit 200r. The transmission mode candidate transmitting unit 202r transmits the generated receiving-side transmission mode candidate information to the transmission mode candidate transmitting unit 101r of the optical transmitting device 1r of the receiving-side system R.

[0165] After transmitting the generated reception side transmission mode candidate information to the transmission mode candidate transmitting unit 101r of the optical transmitting device 1r, the transmission mode candidate transmitting unit 202r outputs a signal quality detection instruction signal for detecting signal quality to the signal quality detecting unit 204r. The signal quality detecting unit 204r receives the signal quality detection instruction signal and sets the flag to "ON".

[0166] The transmission mode candidate transmitting unit 101r of the optical transmitting device 1r performs the same processing as the processing performed by the transmission mode candidate transmitting unit 101t of the optical transmitting device 1t of the transmitting system T in step ST1 when the transmitting side transmission mode candidate information is superimposed on the pilot tone signal and transmitted. That is, the transmission mode candidate transmitting unit 101r of the optical transmitting device 1r superimposes the receiving side transmission mode candidate information of the optical receiving device 2r on the pilot tone signal and transmits it to the optical receiving device 2t via the optical transmission path 3.

[0167] (Processing of Step SR3 by the Light Receiving Device 2r)

[0168] The transmission mode selection unit 203r of the optical receiving device 2r of the receiving system R extracts a common transmission mode number from all the transmission mode numbers stored in the "transmission mode" item of the receiving transmission mode information table 2001r stored in the transmission mode information storage unit 200r and the transmission mode candidate information of the optical transmitting device 1t received from the transmission mode candidate receiving unit 201r. The transmission mode selection unit 203r selects the transmission mode number with the highest priority among the extracted common transmission mode numbers.

[0169] exist Figure 8 The transmission mode information table 1001t and Fig.11 In the reception side transmission mode information table 2001r shown, the common transmission mode information is "mode 1", "mode 5", "mode 9", and "mode 13". Here, if the priority is the multi-value degree of the modulation method as the first priority and the baud rate as the second priority, the transmission mode selection unit 203r selects "mode 13" including the modulation method of 16QAM with the highest multi-value degree from "mode 1", "mode 5", "mode 9", and "mode 13".

[0170] The transmission mode selection unit 203r writes "mode 13" as the selected transmission mode number into the internal storage area to store it. The transmission mode selection unit 203r reads the transmission mode information corresponding to the selected transmission mode number "mode 13" from the receiving side transmission mode information table 2001r of the transmission mode information storage unit 200r. The transmission mode selection unit 203r reads "16QAM" as the modulation method information of the "modulation method" item representing the read transmission mode information, the value of the baud rate "32GBaud" of the "baud rate" item, and the information "RS+LDPC" of the error correction coding method of the "error correction coding type" item.

[0171] The transmission mode selection unit 203r generates a modulation mode signal including the information "16QAM" indicating the modulation mode read out, and outputs it to the main signal demodulation units 24r-1 and 24r-2. The transmission mode selection unit 203r generates a baud rate control signal including the value "32GBaud" of the baud rate read out, and outputs it to the clock control unit 27r. The transmission mode selection unit 203r outputs an error correction coding designation signal including the information "RS+LDPC" indicating the error correction coding mode read out, to the error correction decoding unit 25r.

[0172] Thus, the transmission mode selected by the transmission mode selection unit 203r (i.e., the main signal demodulation units 24r-1, 24r-2) is demodulated in the 16QAM modulation method, the clock of the optical receiving device 2r set by the clock control unit 27r operates at a clock frequency that sets the baud rate to "32GBaud", and the error correction decoding unit 25r performs error correction decoding in the "RS+LDPC" method.

[0173] (Processing of Step ST2 by the Optical Transmitting Device 1 t)

[0174] The transmission mode candidate receiving unit 201t of the optical receiving device 2t of the transmission side system T performs the same processing as the processing performed by the transmission mode candidate receiving unit 201r of the optical receiving device 2r of the above-mentioned receiving side system R in step SR1 when receiving the pilot tone signal superimposed with the transmission side transmission mode candidate information and acquiring the transmission side transmission mode candidate information. That is, the transmission mode candidate receiving unit 201t of the optical receiving device 2t of the transmission side system T receives the pilot tone signal transmitted by the optical transmitting device 1r and acquires the reception side transmission mode candidate information of the optical receiving device 2r superimposed with the pilot tone signal.

[0175] The transmission mode candidate receiving unit 201t of the optical receiving device 2t of the transmitting system T transmits the acquired receiving-side transmission mode candidate information of the optical receiving device 2r to the transmission mode candidate receiving unit 102t of the optical transmitting device 1t. The transmission mode candidate receiving unit 102t of the optical transmitting device 1t receives the receiving-side transmission mode candidate information of the optical receiving device 2r. The transmission mode candidate receiving unit 102t of the optical transmitting device 1t outputs the received receiving-side transmission mode candidate information of the optical receiving device 2r of the receiving system R to the transmission mode selecting unit 103t.

[0176] (Processing of Step ST3 by the Optical Transmitting Device 1 t)

[0177] The transmission mode selection unit 103t extracts a common transmission mode number from all transmission mode numbers stored in the "Transmission Mode" item of the transmission side transmission mode information table 1001t stored in the transmission mode information storage unit 100t and the reception side transmission mode candidate information of the optical receiving device 2r received from the transmission mode candidate reception unit 102t.

[0178] The transmission mode selection unit 103t selects the transmission mode number with the highest priority among the extracted common transmission mode numbers. As described above, the priority that serves as the basis for the selection by the transmission mode selection unit 103t is the same as the priority of the transmission mode selection unit 203r of the optical receiving device 2r. Therefore, the transmission mode selection unit 103t selects the transmission mode number "mode 13" that is the same as the transmission mode number selected by the transmission mode selection unit 203r of the optical receiving device 2r in step SR3. The transmission mode selection unit 103t writes "mode 13" as the selected transmission mode number into the internal storage area to store it.

[0179] The transmission mode selection unit 103t reads the transmission mode information corresponding to the selected transmission mode number "mode 13" from the transmission side transmission mode information table 1001t of the transmission mode information storage unit 100t. The transmission mode selection unit 103t reads the modulation mode information "16QAM" of the "modulation mode" item of the read transmission mode information, the baud rate value "32GBaud" of the "baud rate" item, and the error correction coding mode information "RS+LDPC" of the "error correction coding type" item. The transmission mode selection unit 103t generates a modulation mode signal including the information "16QAM" indicating the read modulation mode and outputs it to the main signal modulation units 13t-1 and 13t-2. The transmission mode selection unit 103t generates a baud rate control signal including the read baud rate value "32GBaud" and outputs it to the clock control unit 17t. The transmission mode selection unit 103t outputs an error correction coding designation signal including the information "RS+LDPC' indicating the read error correction coding mode to the error correction coding unit 12t.

[0180] Thus, the main signal modulation units 13t-1 and 13t-2 are modulated in the transmission mode selected by the transmission mode selection unit 103t (i.e., the modulation method of 16QAM), the clock of the optical sending device 1t set by the clock control unit 17t operates at a clock frequency that sets the baud rate to "32GBaud", and the error correction coding unit 12t performs error correction coding in the "RS+LDPC" method.

[0181] (Processing of Step ST4 by the Optical Transmitting Device 1 t)

[0182] The signal transmission unit 110t of the optical transmission device 1t of the transmission side system T generates the main signal. That is, in the signal transmission unit 110t, the frame unit 11t calls in the client signal, writes the called in client signal to the payload unit 42 of the OTN frame 40, writes information used for monitoring to the overhead unit 41, and outputs it to the error correction coding unit 12t. The error correction coding unit 12t encodes the signal frame output by the frame unit 11t using the error correction coding method of "RS+LDPC" indicated by the error correction coding designation signal received from the transmission mode selection unit 103t to generate an error correction code. The error correction coding unit 12t writes the generated error correction code to the error correction coding unit 43 of the OTN frame 40 and outputs the OTN frame 40 to the main signal modulation units 13t-1 and 13t-2.

[0183] Each of the main signal modulation units 13t-1 and 13t-2 modulates the main signal for the X-polarized wave and the main signal for the Y-polarized wave, which are the main signals output by the error correction coding unit 12t, using the modulation method "16QAM" indicated by the modulation method signal received from the transmission mode selection unit 103t. The main signal modulation units 13t-1 and 13t-2 generate transmission symbol sequences by modulation, and output the generated transmission symbol sequences to the multiplexing units 14t-1 and 14t-2 connected to each other. The multiplexing units 14t-1 and 14t-2 perform time division multiplexing on the transmission symbol sequences of the main signals and control information. The electrical-optical conversion units 15t-1 and 15t-2 convert the electrical signals output by the multiplexing units 14t-1 and 14t-2 into optical signals, and the polarization wave multiplexing unit 16t performs polarization wave multiplexing on the optical signals and sends the optical signals to the optical transmission path 3.

[0184] (Processing of Step SR4 by the Light Receiving Device 2r)

[0185] The polarization separation unit 21r of the optical receiving device 2r of the receiving system R receives the signal light including the main signal transmitted through the optical transmission path 3. The polarization separation unit 21r performs polarization separation in the optical region on the received signal light, separates it into two orthogonal X-polarized waves and Y-polarized waves, and outputs each of the separated X-polarized waves and Y-polarized waves to the photoelectric conversion units 22r-1 and 22r-2. Each of the photoelectric conversion units 22r-1 and 22r-2 takes in the signal light of the X-polarized wave and the Y-polarized wave output by the polarization separation unit 21r and converts them into electrical analog signals, and outputs the converted electrical analog signals to the corresponding AD conversion units 23r-1 and 23r-2.

[0186] The AD converters 23r-1 and 23r-2 convert the electrical analog signals outputted by the photoelectric converters 22r-1 and 22r-2 connected to each other into digital signals to generate digital reception signals. The AD converters 23r-1 and 23r-2 output the generated digital reception signals to the main signal demodulators 24r-1 and 24r-2 connected to each other. In addition, the AD converters 23r-1 and 23r-2 output the generated digital reception signals to the control information detector 211r and the control information extractors 212r-1 and 212-r-2 of the control information demodulator 210r.

[0187] Here, since the flag is turned "ON", the signal quality detection unit 204r detects the signal quality using the pilot tone signal, for example, detects the SN ratio obtained from the strength of a specific frequency of the digital reception signal. The signal quality detection unit 204r outputs information indicating the detected signal quality (i.e., the value of the detected SN ratio) to the signal quality determination unit 205r and sets the flag to "OFF".

[0188] (Processing of Steps SR5, SR6, and SR7 by the Light Receiving Device 2r)

[0189] The signal quality determination unit 205r of the optical receiving device 2r determines whether the signal quality is the permitted quality based on the predetermined threshold value and the information indicating the signal quality detected by the signal quality detection unit 204r (step SR5). For example, when the information indicating the signal quality is the SN ratio, when the value of the SN ratio is greater than the threshold value, the signal quality determination unit 205r determines that the signal quality is the permitted quality (step SR5, yes). When it is determined that the signal quality is the permitted quality, the signal quality determination unit 205r transmits a notification signal of signal quality permission notification to the optical transmitting device 1r, and outputs the notification signal of signal quality permission notification to the transmission mode selection unit 203r (step SR6).

[0190] On the other hand, when the value of the SN ratio is less than the threshold value, the signal quality determination unit 205r determines that the signal quality is not allowed (step SR5, No). When the signal quality is determined to be not allowed, the signal quality determination unit 205r transmits a notification signal of signal quality not allowed notification to the optical transmission device 1r, and outputs the notification signal of signal quality not allowed notification to the transmission mode selection unit 203r (step SR7).

[0191] Upon receiving the notification signal of the signal quality permission notification from the signal quality determination unit 205r, the transmission mode selection unit 203r of the optical receiving device 2r determines the transmission mode information selected at that time as the transmission mode information used in operation and ends the processing.

[0192] On the other hand, when receiving the notification signal of signal quality non-permission notification from the signal quality determination unit 205r, the transmission mode selection unit 203r of the optical receiving device 2r performs the processing after step SR3. In step SR3, the transmission mode selection unit 203r selects "mode 9" of the transmission mode number which is the transmission mode information with the second highest priority among the transmission mode information selected at that time from the common transmission mode information.

[0193] (Processing of Steps ST5 and ST6 by the Optical Transmitting Device 1 t)

[0194] The transmission mode selection unit 103t of the optical transmission device 1t receives the notification signal from the signal quality determination unit 205r of the optical reception device 2r (step ST5). Specifically, the transmission mode selection unit 103t of the optical transmission device 1t receives the notification signal output from the signal quality determination unit 205r of the optical reception device 2r and transmitted inline from the optical transmission device 1r of the reception side system R to the optical reception device 2t. The transmission mode selection unit 103t determines whether the received notification signal is a signal quality permission notification (step ST6). When it is determined that the received notification signal is a signal quality permission notification (step ST6, yes), the transmission mode selection unit 103t determines the transmission mode information selected at this time as the transmission mode information used in operation and ends the processing.

[0195] On the other hand, when the received communication signal is not a signal quality permission notification (i.e., a signal quality permission notification) (step ST6, No), the transmission mode selection unit 103t of the optical transmitting device 1t performs processing after step ST3, and in step ST3, selects "mode 9" of the transmission mode number which is the transmission mode information with the second highest priority among the transmission mode information selected at this moment from the common transmission mode information.

[0196] According to the configuration of the first embodiment described above, in the optical transmission system S, the transmission mode selection units 103t and 203r select the transmission mode information in the order of highest priority from the plurality of transmission mode information common to the transmission performance of the optical transmitting device 1t and the optical receiving device 2r, which are the combination of a plurality of parameters related to the transmission performance. The signal transmitting unit 110t of the optical transmitting device 1t transmits the modulated signal via the optical transmission path 3 based on the transmission mode information selected by the transmission mode selection unit 103t. The signal receiving unit 220r of the optical receiving device 2r receives the signal transmitted by the optical transmission path 3 and demodulates the received signal based on the transmission mode information selected by the transmission mode selection unit 203r. The signal quality detection unit 204r of the optical receiving device 2r detects the signal quality of the signal received by the signal receiving unit 220r. The signal quality determination unit 205r of the optical receiving device 2r determines whether the signal quality of the signal is acceptable based on the information indicating the signal quality detected by the signal quality detection unit 204r. When the signal quality determination unit 205r determines that the signal quality of the signal is not acceptable, the transmission mode selection units 103t and 203r select the transmission mode information with the next highest priority.

[0197] Thus, the optical transmitter 1t of the transmission side system T and the optical receiver 2r of the reception side system R can select the transmission mode information with high priority and good signal quality from the multiple transmission mode information they have in common, and start the operation of the transmission mode represented by the selected transmission mode information. As described above, with the high functionality of digital signal processing (DSP) for optical transmission, the modulation method increases, the baud rate also becomes variable, and the frequency band occupied by the transmission mode varies. Moreover, by adding parameters such as error correction coding type, the transmission mode is diversified. In this way, the optical transmission system S can select the best transmission mode from a variety of transmission modes.

[0198] In other words, in the configuration of the first embodiment, the optical transmitting device 1t receives the operation of the user or sends a list of transmission mode numbers showing the transmission mode information of the optical transmitting device to the optical receiving device 2r at the time of startup. If the optical receiving device 2r receives the list of transmission mode numbers from the optical transmitting device 1t, it sends the list of transmission mode numbers showing the transmission mode information of the optical receiving device to the optical transmitting device 1t, and exchanges the lists of transmission mode numbers showing each other's transmission mode information. When the exchange is completed, the optical transmitting device 1t and the optical receiving device 2r select a transmission mode of a higher multi-value modulation method and a higher baud rate transmission mode from the common transmission mode, which matches the error correction coding category during transmission and reception under the condition of satisfying signal quality. The process of this processing is a processing order of so-called AutoNegotiation. In the first embodiment, the link establishment in the optimal transmission mode can be performed according to this order.

[0199] In addition, in the configuration of the first embodiment described above, when the transmission mode candidate information of the transmission side of the optical transmission device 1t is transmitted from the optical transmission device 1t of the transmission side system T to the optical reception device 2r of the reception side system R, and also when the transmission mode candidate information of the reception side of the optical reception device 2r is transmitted from the optical transmission device 1r of the reception side system R to the optical reception device 2t of the transmission side system T, a configuration is set to use a pilot tone signal that can be transmitted and received even in a state where the modulation mode cannot be distinguished. Therefore, even if pre-processing such as determining the modulation mode in advance is not performed on the transmission side and the reception side, it is possible to start the optical transmission device 1t and start the above-mentioned operation, for example, in a state where devices other than the optical transmission device 1t are started. Fig.14 Processing shown.

[0200] In addition, as mentioned above Fig.14 The premise of the processing shown in the figure is that the same transmission mode is also selected between the optical receiving device 2t and the optical transmitting device 1r in another opposing relationship, but this premise is not a necessary prerequisite. Fig.14 In parallel, the optical transmitting device 1r and the optical receiving device 2t perform Fig.14 Thus, in parallel with the process of selecting the optimal transmission mode between the optical transmitting device 1t and the optical receiving device 2r, the process of selecting the optimal transmission mode can also be performed between the optical transmitting device 1r and the optical receiving device 2t.

[0201] In this case, the connection relationship between the optical transmitting device 1t and the optical receiving device 2t of the transmission side system T becomes Fig.15In the case where the transmission mode selection has been completed between the optical receiving device 2t and the optical transmitting device 1r, Fig.13 In the case of the optical receiving device 2t, the differential decoding unit 213t of the optical receiving device 2t outputs only the differential decoded signal including the "receiving side transmission mode candidate information of the optical receiving device 2r". Fig.14 In the case of the processing shown, the differential decoding unit 213t of the optical receiving device 2t further outputs a differential decoded signal including "transmission mode candidate information of the optical transmitting device 1r". Therefore, the transmission mode candidate receiving unit 201t of the control unit 20t in the optical receiving device 2t needs to perform separate processing based on the content of the information included in the differential decoded signal output by the differential decoding unit 213t.

[0202] When the transmission mode candidate receiving section 201t demodulates the differential decoded signal output by the differential decoder 213t and acquires the "transmission mode candidate information on the transmission side of the optical transmitter 1r", the acquired information is output to the transmission mode selecting section 203t. On the other hand, when the transmission mode candidate receiving section 201t demodulates the differential decoded signal output by the differential decoder 213t and acquires the "reception side transmission mode candidate information on the optical receiver 2r", the acquired information is output to the transmission mode candidate receiving section 102t of the optical transmitter 1t.

[0203] In addition, since the transmission mode candidate transmitting unit 202t of the optical receiving device 2t transmits the "receiving side transmission mode candidate information of the optical receiving device 2t" to the optical transmitting device 1r of the receiving side system R, Fig.15 As shown, it is transmitted to the transmission mode candidate transmitting unit 101t of the optical transmitting device 1t.

[0204] In addition, the connection relationship between the optical receiving device 2r and the optical transmitting device 1r of the receiving side system R is as follows: Fig.16 In the case where the transmission mode selection is completed between the optical receiving device 2t and the optical transmitting device 1r, Fig.12 In the case of the optical receiving device 2r, the differential decoding unit 213r outputs only the differential decoded signal including the "transmission mode candidate information of the optical transmitting device 1t". Fig.14 In the case of the processing shown, the differential decoding unit 213r of the optical receiving device 2r further outputs a differential decoded signal including "the receiving side transmission mode candidate information of the optical receiving device 2t". Therefore, the transmission mode candidate receiving unit 201r of the control unit 20r needs to perform separate processing based on the content of the information included in the differential decoded signal output by the differential decoding unit 213r.

[0205] When the transmission mode candidate receiving section 201r demodulates the differential decoded signal output by the differential decoder 213r and acquires the "transmission mode candidate information on the transmission side of the optical transmission device 1t", the acquired information is output to the transmission mode selecting section 203r. On the other hand, when the transmission mode candidate receiving section 201r demodulates the differential decoded signal output by the differential decoder 213r and acquires the "reception side transmission mode candidate information on the optical receiving device 2t", the acquired information is output to the transmission mode candidate receiving section 102r of the optical transmission device 1r.

[0206] As such, it is necessary to perform parallel communication between the optical transmitting device 1t and the optical receiving device 2r and between the optical transmitting device 1r and the optical receiving device 2t. Fig.14 In contrast, for example, when the optical transmission device 1t and the optical reception device 2t of the transmission side system T are integrally configured and the types of transmission modes that can be transmitted are the same, or when the optical reception device 2r and the optical transmission device 1r of the reception side system R are integrally configured and the types of transmission modes that can be transmitted are the same, it is not necessary to perform the processing in parallel. Fig.14 This is because it can be performed only by using the optical transmission device 1t of the transmission side system T and the optical reception device 2r of the reception side system R. Fig.14 The processing shown is used to simultaneously select the optimal transmission mode between the optical transmitting device 1t and the optical receiving device 2r and between the optical transmitting device 1r and the optical receiving device 2t. However, the premise is that there is no large difference in the transmission quality of the path from the transmitting side system T to the receiving side system R of the optical transmission path 3 and the transmission quality of the path from the receiving side system R to the transmitting side system T. This is because when the transmission quality of the path from the receiving side system R to the transmitting side system T deteriorates to a greater extent than the transmission quality of the path from the transmitting side system T to the receiving side system R, there is a possibility that the transmission from the optical transmitting device 1r to the optical receiving device 2t cannot be performed normally in the transmission mode selected by the optical transmitting device 1t and the optical receiving device 2r. In addition, it is also possible to Fig.14 After the processing of step SR6 of the optical receiving device 2r of the receiving side system R shown in the figure, the optical transmitting device 1r of the receiving side system R transmits a response signal indicating that the transmission mode selection processing is completed in the finally selected transmission mode, and when the optical receiving device 2t of the transmitting side system T can normally receive the response signal, the operation state is transitioned to the normal operation state. Here, "transmission quality" refers to the OSNR when the receiving side system R receives the signal.

[0207] (Another Configuration Example of the First Embodiment)

[0208] In the optical transmission system S of the first embodiment, the optical transmission device 1t of the transmission side system T may be replaced by Fig.17 The optical transmitting device 1ta shown in the figure is replaced by the optical receiving device 2r of the receiving side system R. Fig.18 The light receiving device 2ra shown.

[0209] exist Fig.17 In the optical transmission device 1ta shown, the same reference numerals are used for the same components as those of the optical transmission device 1t, and the different components are described below. The optical transmission device 1ta does not include the control information modulation unit 18t and the multiplexing units 14t-1 and 14t-2 included in the optical transmission device 1t. The optical transmission device 1ta includes a framing unit 11ta instead of the framing unit 11t, and includes a control unit 10ta instead of the control unit 10t. The control unit 10ta includes a transmission mode candidate transmission unit 101ta instead of the transmission mode candidate transmission unit 101t.

[0210] In addition, Fig.17 In the figure, the structure including the frame division unit 11ta, the error correction coding unit 12t, the main signal modulation unit 13t-1, 13t-2, the electro-optical conversion unit 15t-1, 15t-2, the polarization wave multiplexing unit 16t and the clock control unit 17t is called the signal sending unit 110ta.

[0211] exist Figure 3 In the overhead section 41 of the OTN frame 40 shown, there are two RES (Reserved) fields indicated by reference numerals 410 and 411. RES410 and 411 are predetermined fields used for future standardization. The transmission mode candidate sending section 101ta outputs the transmission mode candidate information of the optical transmitter 1ta to be sent to the optical receiver 2ra to the framing section 11ta. The framing section 11ta forms the OTN frame 40, and when writing information used for monitoring to the overhead section 41, the transmission mode candidate information of the optical transmitter 1ta output by the transmission mode candidate sending section 101ta is written to the fields of RES410 and 411. As a result, the transmission mode candidate information of the optical transmitter 1ta is transmitted to the optical receiver 2ra via the optical transmission path 3 as part of the main signal.

[0212] exist Fig.18 In the optical receiving device 2ra shown in the figure, the same reference numerals are used for the same components as those of the optical receiving device 2r, and the different components are described below. The optical receiving device 2ra does not include the control information demodulation unit 210r included in the optical receiving device 2r. The optical receiving device 2ra includes a deframing unit 26ra instead of the deframing unit 26r, and includes a control unit 20ra instead of the control unit 20r. The control unit 20ra includes a transmission mode candidate receiving unit 201ra instead of the transmission mode candidate receiving unit 201r.

[0213] In addition, Fig.18 In the figure, the structure including the polarization wave separation unit 21r, the photoelectric conversion unit 22r-1, 22r-2, the AD conversion unit 23r-1, 23r-2, the main signal demodulation unit 24r-1, 24r-2, the error correction decoding unit 25r, the deframing unit 26ra and the clock control unit 27r is called the signal receiving unit 220ra.

[0214] When the deframe unit 26ra receives the error-corrected OTN frame 40 outputted from the error correction decoding unit 25r, the client signal is read out from the payload unit 42 of the OTN frame 40, and the read client signal is outputted to the IP type device connected to the optical receiving device 2r. In addition, the deframe unit 26ra reads the transmission mode candidate information of the optical transmitting device 1ta written in the fields RES410 and 411 of the overhead unit 41 of the OTN frame 40.

[0215] The deframe unit 26ra outputs the read transmission mode candidate information of the optical transmitter 1ta to the transmission mode candidate receiving unit 201ra. Thus, the transmission mode candidate receiving unit 201ra of the optical receiver 2ra can obtain the transmission mode candidate information of the optical transmitter 1ta transmitted by the optical transmitter 1ta.

[0216] Furthermore, the transmission mode candidate receiving unit 201ra outputs the acquired transmission side transmission mode candidate information to the transmission mode selecting unit 203r. Furthermore, if the transmission mode candidate receiving unit 201ra acquires the transmission side transmission mode candidate information, it outputs a reception side transmission mode candidate information transmission instruction signal for transmitting the reception side transmission mode candidate information to the transmission mode candidate transmitting unit 202r.

[0217] As described above, when information is transmitted using the fields of RES410 and 411 of the OTN frame 40, unlike the case of using the pilot tone signal, the receiving side cannot demodulate and obtain information when the receiving side cannot recognize the modulation method of the transmitting side. Therefore, in the optical transmitting device 1ta and the optical receiving device 2ra, for example, it is necessary to predetermine the initial value of the transmission mode that is automatically set at startup. For example, the transmission mode with the lowest multi-value degree and baud rate is numbered as "mode 1" and is predetermined as the initial value. The optical transmitting device 1ta sends the modulated main signal to the optical receiving device 2ra based on the transmission mode "mode 1" of the initial value, so that the optical receiving device 2ra can demodulate the received main signal based on the transmission mode "mode 1" of the initial value to obtain information.

[0218] In addition, when the fields RES410 and 411 of the OTN frame 40 are used to transmit information, power is not concentrated on a specific frequency as in the case of using a pilot tone signal. Therefore, the signal quality detection unit 204r cannot detect the SN ratio obtained from the strength of the signal at a specific frequency or the strength itself as the signal quality. Therefore, in this other configuration example, the signal quality detection unit 204r detects, for example, the bit error rate (BER) obtained in the error correction decoding unit 25r as information indicating the signal quality. In addition, it is also possible to preliminarily use the pilot tone signal as a reference. Figure 2 The optical transmission device 1t shown or Fig. 9 The optical receiving device 2r shown has a similar configuration, detects the OSNR obtained from the pilot tone signal as information indicating signal quality, and uses the fields of RES 410 and 411 of the OTN frame 40 for transmitting transmission mode information.

[0219] exist Figure 1 In the optical transmission system S of the transmission side, the optical transmission device 1t of the transmission side system T is replaced by Fig.17 The optical transmitting device 1ta shown in the figure is replaced by the optical receiving device 2r of the receiving side system R Fig.18 In the case of the optical receiving device 2ra shown in the figure, the transmission from the optical transmitting device 1r to the optical receiving device 2t in another opposing relationship transmits information through the pilot tone signal. Therefore, the transmission and reception using the fields of RES410 and 411 of the OTN frame 40 and the transmission and reception using the pilot tone signal are combined. In addition, it is also possible to Figure 1 In the configuration, the optical transmitting device 1t and the optical receiving device 2r are still configured to use the pilot tone signal, and the optical transmitting device 1r and the optical receiving device 2t in another opposing relationship are replaced with a configuration using the RES410 and 411 fields of the OTN frame 40.

[0220] In addition, Figure 1 In the optical transmission system S, the optical receiving device 2t of the transmission side system T and the optical transmitting device 1r of the receiving side system R may be replaced with an optical receiving device 2ra or an optical transmitting device 1ta configured to transmit and receive the transmission mode candidate information on the transmission side and the receiving side using the above-mentioned OTN frame 40. With such a configuration, the transmission and reception of the transmission mode candidate information on the transmission side and the receiving side between the optical transmitting device 1ta and the optical receiving device 2ra and between the optical transmitting device 1ra and the optical receiving device 2ta are all performed using the fields RES410 and 411 of the OTN frame 40.

[0221] In addition, an optical transmitting device having both the configuration of the optical transmitting device 1t and the configuration of the optical transmitting device 1ta and an optical receiving device having both the configuration of the optical receiving device 2r and the configuration of the optical receiving device 2ra may also be applied. In this way, the receiving side transmission mode candidate information or the transmitting side transmission mode candidate information can be transmitted using two systems of the pilot tone signal and the fields of RES410 and 411 of the OTN frame 40, thereby improving reliability. Not only the reliability is improved, but also the OSNR is detected as information indicating the signal quality, thereby realizing a flexible implementation method such as using the pilot tone signal and using the fields of RES410 and 411 of the OTN frame 40 for transmitting the transmission mode information.

[0222] In addition, in the configuration of the first embodiment described above, the signal quality determination unit 205r of the optical receiving device 2r sends the notification signal inline to the transmission mode selection unit 103t of the optical transmitting device 1t, but the configuration of the present invention is not limited to this embodiment, and the notification signal can also be sent from the optical receiving device 2r to the optical transmitting device 1t using the optical transmitting device 1r of the receiving side system R and the optical receiving device 2t of the transmitting side system T.

[0223] (Second embodiment)

[0224] Fig.19 1 is a block diagram showing the configuration of an optical transmission system Sb of the second embodiment. In the second embodiment, the same reference numerals are used for the same configurations as those of the first embodiment, and the different configurations are described below. The optical transmission system Sb includes an optical transmitter 1b, an optical receiver 2b, an optical transmission path 3b, and a control device 6. The optical transmission path 3b includes an optical fiber 300, which transmits the signal light output by the optical transmitter 1b to the optical receiver 2b. The control device 6 and the optical transmitter 1b, and the control device 6 and the optical receiver 2b are connected, for example, via a dedicated circuit or a communication circuit such as the Internet.

[0225] The control device 6 is a device including, for example, an SDN (Software Defined Networking) controller or a conventional type of operating system, and includes a transmission mode selection unit 60, a transmission mode information storage unit 61, and a signal quality determination unit 205r. The transmission mode information storage unit 61 may also store, for example, Figure 8 The transmission mode information table 1001t and Fig.11 The reception side transmission mode information table 2001r shown may collect information from any one of the optical transmitting device 1b and the optical receiving device 2b.

[0226] The transmission mode selection unit 60 extracts a common transmission mode number from the transmission mode information table 1001t on the transmission side and the reception mode information table 2001r on the transmission mode information storage unit 61. In addition, the transmission mode selection unit 60 selects a transmission mode number with the highest priority among the extracted common transmission mode numbers. As in the first embodiment, the priority is predetermined, and for example, a transmission mode number corresponding to transmission mode information including a modulation method with a higher multi-value degree and a higher baud rate has a higher priority.

[0227] In addition, the transmission mode selection unit 60 has a storage area inside, and writes the selected transmission mode number into the internal storage area to store it. In addition, the transmission mode selection unit 60 generates a transmission mode designation signal including the selected transmission mode number, and sends the generated transmission mode designation signal to the optical transmitting device 1b and the optical receiving device 2b. In addition, when the transmission mode selection unit 60 receives a notification signal from the signal quality determination unit 205r, when the notification included in the notification signal is a signal quality non-permitting notification, the transmission mode selection unit 60 refers to the internal storage area and selects the transmission mode number of the transmission mode information with the second highest priority among the transmission mode information selected at that time. In addition, in the second embodiment, the output destination of the notification signal of the signal quality determination unit 205r is the transmission mode selection unit 60.

[0228] The optical transmission device 1b includes a signal transmission unit 110b and a control unit 10b. The signal transmission unit 110b is connected to the optical transmission path 3b, for example, Fig.17 In the structure of the signal transmission unit 110ta shown in the figure, the frame division unit 11ta is replaced by Figure 2 The structure of the frame division unit 11t.

[0229] The control unit 10b includes a transmission mode receiving unit 120 and a transmission mode information storage unit 100b. The transmission mode information storage unit 100b stores the transmission mode information in advance. Figure 8 The transmission mode receiving unit 120 receives the transmission mode designation signal sent by the transmission mode selection unit 60 of the control device 6, and reads the transmission mode information of the transmission mode number included in the transmission mode designation signal from the transmission mode information storage unit 100b. In addition, the transmission mode receiving unit 120 outputs the modulation method signal to the main signal modulation units 13t-1 and 13t-2 of the signal transmission unit 110b, outputs the error correction coding designation signal to the error correction coding unit 12t, and outputs the baud rate control signal to the clock control unit 17t based on the read transmission mode information.

[0230] The optical receiving device 2b includes a signal receiving unit 220b and a control unit 20b. The signal receiving unit 220b is connected to the optical transmission path 3b and has, for example, Fig. 9 The structure of the signal receiving unit 220r of the light receiving device 2r shown.

[0231] The control unit 20b includes a transmission mode receiving unit 230, a transmission mode information storage unit 200b, and a signal quality detection unit 204b. The transmission mode information storage unit 200b stores the signal quality information in advance. Fig.11 The transmission mode receiving unit 230 receives the transmission mode designation signal sent by the transmission mode selection unit 60 of the control device 6, and reads the transmission mode information of the transmission mode number included in the transmission mode designation signal from the transmission mode information storage unit 200b. In addition, based on the read transmission mode information, the transmission mode receiving unit 230 outputs the modulation method signal to the main signal demodulation units 24r-1 and 24r-2 of the signal receiving unit 220b, outputs the error correction coding designation signal to the error correction decoding unit 25r, and outputs the baud rate control signal to the clock control unit 27r.

[0232] The signal quality detection unit 204b detects the signal quality and outputs information indicating the detected signal quality to the signal quality determination unit 205r.

[0233] The signal quality detection unit 204b detects, for example, OSNR detected from control information using a pilot tone signal as information indicating signal quality. Alternatively, the bit error rate (BER) obtained in the error correction decoding unit 25r may be used as information indicating signal quality.

[0234] The signal quality detection unit 204b may use information obtained from a measuring instrument such as an OTDR, a spectrum analyzer, or a power meter as a signal quality detection method, similarly to the signal quality detection unit 204r.

[0235] (Transmission Mode Selection Process in Second Embodiment)

[0236] Fig. 20 1 is a flowchart showing the flow of the transmission mode selection process performed by the optical transmission system Sb according to the second embodiment. The dotted arrows indicate the transmission and reception of information between the optical transmission device 1b, the control device 6, and the optical reception device 2b.

[0237] The transmission mode selection unit 60 of the control device 6 starts processing in response to an operation by a user or in accordance with the timing of activation of the control device 6 or the timing of connection between the optical transmission device and the optical reception device. The transmission mode selection unit 60 reads out the transmission mode information table 1001t and the reception mode information table 2001r from the transmission mode information storage unit 61 (step SCb1).

[0238] The transmission mode selection unit 60 extracts the common transmission mode number from the read transmission side transmission mode information table 1001t and the reception side transmission mode information table 2001r. The transmission mode selection unit 60 selects the transmission mode number with the highest priority among the extracted common transmission mode numbers, and writes the selected transmission mode number into the internal storage area to store it (step SCb2).

[0239] The transmission mode selection unit 60 generates a transmission mode designation signal including the selected transmission mode number, and outputs the generated transmission mode designation signal to the optical transmitting device 1b and the optical receiving device 2b (step SCb3). The transmission mode receiving unit 120 of the optical transmitting device 1b receives the transmission mode designation signal transmitted by the transmission mode selection unit 60 of the control device 6 (step STb1).

[0240] The transmission mode receiving unit 120 of the optical transmission device 1b reads the transmission mode information corresponding to the transmission mode number included in the received transmission mode designation signal from the transmission side transmission mode information table 1001t of the transmission mode information storage unit 100b. Based on the read transmission mode information, the transmission mode receiving unit 230 outputs the modulation method signal to the main signal modulation units 13t-1 and 13t-2 of the signal transmission unit 110b, outputs the error correction coding designation signal to the error correction coding unit 12t, and outputs the baud rate control signal to the clock control unit 17t, thereby setting the transmission mode (step STb2). The signal transmission unit 110b of the optical transmission device 1b transmits the main signal (step STb3).

[0241] The transmission mode receiving unit 230 of the optical receiving device 2b receives the transmission mode designation signal transmitted by the transmission mode selecting unit 60 of the control device 6 (step SRb1). The timing of receiving the transmission mode designation signal in step STb1 performed by the optical transmitting device 1b and the timing of receiving the transmission mode designation signal in step SRb1 may have a slight time difference due to the difference in the distance between the control device 6 and the optical transmitting device 1b and the distance between the control device 6 and the optical receiving device 2b.

[0242] The transmission mode receiving unit 230 of the optical receiving device 2b similarly reads out the transmission mode information corresponding to the transmission mode number included in the received transmission mode designation signal from the receiving side transmission mode information table 2001r of the transmission mode information storage unit 200b. Based on the read transmission mode information, the transmission mode receiving unit 230 outputs the modulation method signal to the main signal demodulation units 24r-1 and 24r-2 of the signal receiving unit 220b, outputs the error correction coding designation signal to the error correction decoding unit 25r, and outputs the baud rate control signal to the clock control unit 27r, thereby setting the transmission mode (step SRb2).

[0243] The signal receiving unit 220b of the optical receiving device 2b receives the main signal transmitted through the optical transmission path 3. The signal quality detection unit 204b of the optical receiving device 2b detects the signal quality of the main signal (step SRb3). Here, the signal quality detection unit 204b detects BER as information indicating the signal quality. The signal quality detection unit 204b sends the information indicating the detected signal quality to the signal quality determination unit 205r of the control device 6 (step SRb4).

[0244] The signal quality determination unit 205r of the control device 6 receives information indicating signal quality from the signal quality detection unit 204b (step SCb4). The signal quality determination unit 205r determines whether the signal quality is acceptable based on a predetermined threshold and the information indicating signal quality (step SCb5).

[0245] When the BER value detected by the signal quality detection unit 204b is less than the threshold value, the signal quality determination unit 205r determines that the signal quality is the permitted quality (step SCb5, yes). When it is determined that the signal quality is the permitted quality, the signal quality determination unit 205r outputs a notification signal of signal quality permission notification to the transmission mode selection unit 60. The transmission mode selection unit 60 determines the transmission mode information selected at this time as the transmission mode information used in operation and ends the processing.

[0246] On the other hand, when the BER value detected by the signal quality detection unit 204b is greater than the threshold value, the signal quality determination unit 205r determines that the signal quality is not allowed (step SCb5, No). When it is determined that the signal quality is not allowed, the signal quality determination unit 205r outputs a notification signal of signal quality not allowed notification to the transmission mode selection unit 60. When receiving the notification signal of signal quality not allowed notification from the signal quality determination unit 205r, the transmission mode selection unit 60 performs the processing after step SCb2. In step SCb2, the transmission mode selection unit 60 selects the transmission mode number of the transmission mode information with the second highest priority among the transmission mode information selected at this time from the common transmission mode information, and in step SCb3, generates a transmission mode designation signal including the selected transmission mode number and transmits it to the optical transmission device 1b and the optical reception device 2b.

[0247] According to the configuration of the second embodiment described above, the transmission mode selection unit 60c of the control device 6 of the optical transmission system Sb selects the transmission mode information in the order of high priority from the plurality of transmission mode information common to the transmission performance of the optical transmitting device 1b and the optical receiving device 2b, which are transmission mode information of a combination of a plurality of parameters related to the transmission performance. The signal transmitting unit 110b of the optical transmitting device 1b transmits the modulated signal via the optical transmission path 3b based on the transmission mode information selected by the transmission mode selection unit 60. The signal receiving unit 220b of the optical receiving device 2b receives the signal transmitted by the optical transmission path 3b and demodulates the received signal based on the transmission mode information selected by the transmission mode selection unit 60. The signal quality detection unit 204b of the optical receiving device 2b detects the signal quality of the signal received by the signal receiving unit 220b. The signal quality determination unit 205r of the control device 6 determines whether the signal quality of the signal is permitted based on the information indicating the signal quality detected by the signal quality detection unit 204b. When the signal quality determination unit 205r determines that the signal quality of the signal is not acceptable, the transmission mode selection unit 60 selects the transmission mode information having the next highest priority.

[0248] Thus, the control device 6 can select the transmission mode information with high priority and good signal quality from the plurality of transmission mode information commonly possessed by the optical transmitting device 1b and the optical receiving device 2b. Then, the control device 6 can make the optical transmitting device 1b and the optical receiving device 2b operate using the transmission mode indicated by the selected transmission mode information. That is, the optical transmission system Sb can select the best transmission mode from the transmission modes determined by the combination of various parameters related to the plurality of transmission performances.

[0249] In other words, in the configuration of the second embodiment, the control device 6 selects a transmission mode of an error correction coding category that matches the transmission and reception period as a modulation method with a higher multi-value degree and a higher baud rate from a plurality of transmission modes shared by the optical transmitting device 1b and the optical receiving device 2b, thereby enabling link establishment under the optimal transmission mode.

[0250] In addition, in the configuration of the second embodiment, the control device 6 selects the transmission mode information and transmits the transmission mode designation signal including the transmission mode number of the selected transmission mode information to the optical transmitting device 1b and the optical receiving device 2. Therefore, even in a state where the modulation method of the optical transmitting device 1b cannot be recognized on the optical receiving device 2b side, it is possible to perform the transmission mode designation signal without performing pre-processing such as determining the modulation method on the transmitting side and the receiving side in advance. Fig. 20 Processing shown.

[0251] (Third Embodiment)

[0252] Fig.21 1 is a block diagram showing the configuration of an optical transmission system Sc according to a third embodiment. In the third embodiment, the same reference numerals are used for the same configurations as those in the first embodiment and the second embodiment, and the different configurations are described below. The optical transmission system Sc includes an optical transmission device 1c, an optical receiving device 2c, an optical transmission path 3c, a control device 6c, and a management device 7. The management device 7 and the control device 6c, the control device 6c and the optical transmission device 1c, and the control device 6c and the optical receiving device 2c are connected, for example, via a dedicated circuit or a communication circuit such as the Internet.

[0253] The optical transmission device 1c includes a signal transmission unit 110b and a control unit 10c. The control unit 10c includes a transmission mode receiving unit 120, a transmission mode information storage unit 100b, and an information storage unit 150. The information storage unit 150 has a non-volatile storage area inside, and can also sequentially write information related to the optical transmission device 1c (for example, information on physical characteristic parameters such as the transmission light level, the reception light level, the center frequency, and the wavelength deviation of the optical signal transmitted and received through the optical interface of the optical transmission device 1c) into the internal storage area for storage, and can also monitor the information on the physical characteristic parameters when necessary.

[0254] The optical receiving device 2c includes a signal receiving unit 220b and a control unit 20c. The control unit 20c includes a transmission mode receiving unit 230, a transmission mode information storage unit 200b, a signal quality detection unit 204c, and an information storage unit 250. The information storage unit 250 has a non-volatile storage area inside, and stores information related to the optical receiving device 2c (for example, historical information of physical characteristic parameters such as the transmission light level, the reception light level, the center frequency, and the wavelength deviation of the optical signal transmitted and received through the optical interface of the optical receiving device 2c) by sequentially writing it into the internal storage area.

[0255] The signal quality detection unit 204c detects the OSNR detected from the control information using the pilot tone signal as information indicating the signal quality. The signal quality detection unit 204c outputs the information indicating the detected signal quality to the signal quality determination unit 205c of the control device 6c.

[0256] The signal quality detection unit 204c may use information obtained from a measuring instrument such as an OTDR, a spectrum analyzer, or a power meter as a signal quality detection method, similarly to the signal quality detection unit 204r.

[0257] The optical transmission path 3c includes optical fibers 300-T and 300-R, WSS (Wavelength Selective Switch) 301-T and 301-R, and optical amplifiers 302-T, 302-C and 302-R, and transmits the signal light sent from the optical transmission device 1c to the optical reception device 2c.

[0258] WSS301-T and 301-R are wavelength selection switches that can store information on physical characteristic parameters such as the center frequency of the signal light for wavelength selection, filter bandwidth, filtering order, insertion loss, polarization-dependent loss (hereinafter also referred to as PDL (PolarizationDependent Loss)) obtained in time series in the internal non-volatile storage area, and can also monitor the information on physical characteristic parameters when necessary.

[0259] Optical amplifiers 302-T, 302-C, and 302-R are amplifiers for amplifying signal light. They can also write information on physical characteristic parameters such as the input power level, output power level, gain, and noise figure (hereinafter referred to as "NF" (Noise Figure)) of the amplified signal light obtained in a time series into an internal non-volatile storage area for storage, and can also monitor the information on the physical characteristic parameters when necessary.

[0260] The control device 6c is a SDN controller or a device having an existing type of operating system similarly to the control device 6, and includes an information collection unit 62, a transmission mode selection unit 60c, and a signal quality determination unit 205c. The information collection unit 62 is connected to the transmission mode information storage unit 100b, the information accumulation unit 150, the WSS 301-T, 301-R, the optical amplifiers 302-T, 302-C, 302-R of the optical transmission device 1c, and the transmission mode information storage unit 200b and the information accumulation unit 250 of the optical reception device 2c via a communication circuit.

[0261] In addition, the information collecting unit 62 reads out information on physical characteristic parameters from the internal storage area of ​​the information storage unit 150 of the optical sending device 1c, the internal storage area of ​​the information storage unit 250 of the optical receiving device 2c, the internal storage area of ​​WSS301-T, 301-R, and the internal storage area of ​​the optical amplifiers 302-T, 302-C, 302-R, and writes the read physical characteristic parameters into the transmission design information storage unit 71 of the management device 7 for storage.

[0262] In addition, the information collecting unit 62 can also read out information on physical characteristic parameters related to the optical transmission path obtained by digital signal processing, and write it to the transmission design information storage unit 71 of the management device 7 to store it. The physical characteristic parameters related to the optical transmission path obtained by digital signal processing include wavelength dispersion, polarization mode dispersion, polarization-dependent loss, nonlinear coefficient, etc. These physical characteristic parameters can also be used to perform transmission design of an optical path set as an optical transmission path connecting certain bases.

[0263] In addition, the information collecting unit 62 reads out the information of the transmission mode information table 1001t and the reception mode information table 2001r stored in the transmission mode information storage unit 100b of the optical transmitting device 1c and the transmission mode information storage unit 200b of the optical receiving device 2c, respectively. In addition, the information collecting unit 62 writes the read information of the transmission mode information table 1001t and the reception mode information table 2001r into the transmission design information storage unit 71 of the management device 7 to store them.

[0264] The transmission mode selection unit 60c selects the transmission mode number with the highest priority from the transmission mode candidate list including a plurality of transmission mode information supplied from the management device 7. As in the first and second embodiments, the priority is predetermined, and for example, the transmission mode number corresponding to the transmission mode information including a modulation method with a higher multi-value degree and a higher baud rate has a higher priority.

[0265] In addition, the transmission mode selection unit 60c has a storage area inside, and writes the selected transmission mode number into the internal storage area to store it. In addition, the transmission mode selection unit 60c generates a transmission mode designation signal including the selected transmission mode number, and sends the generated transmission mode designation signal to the optical transmitting device 1c and the optical receiving device 2c. In addition, when receiving a notification signal from the signal quality determination unit 205c, when the notification included in the notification signal is a signal quality non-permitting notification, the transmission mode selection unit 60c refers to the internal storage area and selects the transmission mode number of the transmission mode information with the next highest priority from the transmission mode information selected at that time from the transmission mode candidate list.

[0266] The signal quality determination unit 205c receives the OSNR value sent from the management device 7 and uses the received OSNR value as a threshold. The signal quality determination unit 205c determines whether the signal quality is acceptable based on the threshold and information indicating the signal quality received from the signal quality detection unit 204c.

[0267] In addition, when it is determined that the signal quality is an allowed quality, the signal quality determination unit 205c outputs a notification signal of a signal quality permission notification to the transmission mode selection unit 60c. In addition, when it is determined that the signal quality is an unallowed quality, the signal quality determination unit 205c outputs a notification signal of a signal quality non-permit notification to the transmission mode selection unit 60c.

[0268] The management device 7 includes a transmission design information storage unit 71 and a transmission design processing unit 72. As described above, the transmission design information storage unit 71 stores the physical characteristic parameters of the optical transmission device 1c, the optical reception device 2c, the WSS 301-T, 301-R, the optical amplifiers 302-T, 302-C, and 302-R written by the information collection unit 62, the information of the transmission mode information table 1001t on the transmission side, and the information of the transmission mode information table 2001r on the reception side.

[0269] The transmission design processing unit 72 performs transmission design processing for the entire network based on a level diagram between the optical transmitting device 1c and the optical receiving device 2c based on the physical characteristic parameters stored in the transmission design information storage unit 71, the information in the transmission mode information table 1001t on the transmission side, and the information in the reception mode information table 2001r on the reception side.

[0270] In addition, the transmission design processing unit 72 calculates the transmission quality between the optical transmitting device 1c and the optical receiving device 2c as a result of the transmission design processing, and selects a plurality of transmission mode information as candidates based on the calculated transmission quality. In addition, the transmission design processing unit 72 generates a transmission mode candidate list including the selected plurality of transmission mode information, and outputs the generated transmission mode candidate list to the transmission mode selection unit 60c of the control device 6c. In addition, the transmission design processing unit 72 calculates the OSNR that can be allowed as the signal quality when the signal light transmitted by the optical transmitting device 1c is received in the optical receiving device 2c as a result of the transmission design processing. In addition, the transmission design processing unit 72 sends the calculated OSNR value to the signal quality determination unit 205c.

[0271] (Processing of Management Device in Third Embodiment)

[0272] Fig. 22 This is a flowchart showing the flow of processing performed by the management device 7 of the third embodiment. Fig. 22 Prior to the flowchart shown in FIG. 1 , information on the physical characteristic parameters of the WSS 301-T, 301-R, the optical amplifiers 302-T, 302-C, 302-R, the optical transmitter 1c, and the optical receiver 2c has been written in the transmission design information storage unit 71 by the information collection unit 62 of the control device 6c. In addition, information on the transmission mode information table 1001t on the transmission side and information on the transmission mode information table 2001r on the reception side have been written in the transmission design information storage unit 71 by the information collection unit 62 of the control device 6c.

[0273] The transmission design processing unit 72 of the management device 7 extracts common transmission mode information from the information of the transmission mode information table 1001t on the transmission side and the information of the transmission mode information table 2001r on the reception side stored in the transmission design information storage unit 71. The transmission design processing unit 72 performs transmission design processing on each extracted transmission mode information based on the physical characteristic parameters stored in the transmission design information storage unit 71, and calculates the transmission quality of each transmission mode information (step SMc1).

[0274] When performing transmission design processing based on the physical characteristic parameters stored in the transmission design information storage unit 71 , the transmission design processing unit 72 calculates the OSNR when the signal light transmitted by the optical transmission device 1 c is received in the optical reception device 2 c (step SMc2 ).

[0275] The transmission design processing unit 72 selects a predetermined number of transmission mode information as candidates in order, for example, from transmission mode information with high transmission quality based on the calculated transmission quality, and generates a transmission mode candidate list including the selected transmission mode information (step SMc3).

[0276] The transmission design processing unit 72 sends the generated transmission mode candidate list to the transmission mode selection unit 60 c of the control device 6 c , and sends the calculated OSNR value to the signal quality determination unit 205 c (step SMc4 ).

[0277] (Transmission Mode Selection Process in Third Embodiment)

[0278] Fig.23 1 is a flowchart showing the flow of the transmission mode selection process performed by the optical transmission system Sc according to the third embodiment. The dotted arrows indicate the transmission and reception of information among the optical transmission device 1c, the control device 6c, and the optical reception device 2c.

[0279] exist Fig. 22 In the process of step SMc4, the transmission design processing unit 72 of the management device 7 sends the generated transmission mode candidate list to the transmission mode selection unit 60c of the control device 6c, and sends the calculated OSNR value to the signal quality determination unit 205c. The transmission mode selection unit 60c of the control device 6c receives the transmission mode candidate list. The signal quality determination unit 205c of the control device 6c receives the OSNR value (step SCc1).

[0280] The transmission mode selection unit 60 c selects the transmission mode number of the transmission mode information having the highest priority from the transmission mode candidate list, and writes and stores the selected transmission mode number in the internal storage area (step SCc2 ).

[0281] The transmission mode selection unit 60 c generates a transmission mode designation signal including the selected transmission mode number, and outputs the generated transmission mode designation signal to the optical transmission device 1 c and the optical reception device 2 c (step SCc3 ).

[0282] In steps STc1 to STc3 in the optical transmission device 1c, Fig. 20 The same processing as steps STb1 to STb3 in the optical transmitter 1b of the second embodiment shown in FIG. Fig. 20 Steps SRb1 to SRb2 in the optical receiving device 2 b of the second embodiment shown are the same processing.

[0283] The signal receiving unit 220b of the optical receiving device 2c receives the main signal transmitted through the optical transmission path 3c. The signal quality detection unit 204c of the optical receiving device 2c detects the OSNR of the main signal (step SRb3). The signal quality detection unit 204c sends the detected OSNR value to the signal quality determination unit 205c of the control device 6c (step SRc4).

[0284] The signal quality determination unit 205c of the control device 6c receives the value of OSNR from the signal quality detection unit 204c (step SCc4). The signal quality determination unit 205c uses the value of OSNR received from the transmission design processing unit 72 of the management device 7 in step SCc1 as a threshold value, and determines whether the signal quality is an acceptable quality based on the threshold value and the value of OSNR received from the signal quality detection unit 204c (step SCb5).

[0285] For example, when the value of the OSNR detected by the signal quality detection unit 204c is greater than the threshold, the signal quality determination unit 205c determines that the signal quality is the permitted quality (step SCc5, yes). When it is determined that the signal quality is the permitted quality, the signal quality determination unit 205c outputs a notification signal of signal quality permission notification to the transmission mode selection unit 60c. The transmission mode selection unit 60c determines the transmission mode information selected at this time as the transmission mode information used in operation and ends the processing.

[0286] On the other hand, when the value of OSNR is less than the threshold value, the signal quality determination unit 205c determines that the signal quality is not allowed (step SCc5, No). When it is determined that the signal quality is not allowed, the signal quality determination unit 205c outputs a notification signal of signal quality not allowed notification to the transmission mode selection unit 60c. When receiving the notification signal of signal quality not allowed notification from the signal quality determination unit 205c, the transmission mode selection unit 60c performs the processing after step SCc2. In step SCc2, the transmission mode selection unit 60c selects the transmission mode number of the transmission mode information with the second highest priority among the transmission mode information selected at this time from the transmission mode candidate list, and generates a transmission mode designation signal including the selected transmission mode number in step SCc3 and sends it to the optical transmitting device 1c and the optical receiving device 2c.

[0287] According to the configuration of the third embodiment described above, in the management device 7 of the optical transmission system Sc, the transmission design processing unit 72 calculates the transmission quality for each of the plurality of transmission mode information common to the transmission performance of the optical transmitting device 1c and the optical receiving device 2c based on the physical characteristic parameters stored in the transmission design information storage unit 71. The transmission design processing unit 72 generates a transmission mode candidate list including the plurality of transmission mode information selected based on the calculated transmission quality, and sends the generated transmission mode candidate list to the transmission mode selection unit 60c of the control device 6c. Thus, the transmission mode selection unit 60c of the third embodiment can select the best transmission mode with a high priority and a large OSNR value as a transmission mode with high transmission quality required according to the transmission design based on the physical characteristic parameters of the various modules, the optical transmitting device 1c and the optical receiving device 2c equipped in the optical transmission path 3c.

[0288] (Fourth Embodiment)

[0289] Fig.24 1 is a block diagram showing the configuration of an optical transmission system Sd according to a fourth embodiment. In the fourth embodiment, the same components as those in the first to third embodiments are denoted by the same reference numerals, and the different components are described below. The optical transmission system Sd includes an optical transmission device 1c, an optical receiving device 2c, an optical transmission path 3c, a control device 6c, and a management device 7d. The management device 7d and the control device 6c, the control device 6c and the optical transmission device 1c, and the control device 6c and the optical receiving device 2c are connected via a communication circuit such as a dedicated circuit or the Internet.

[0290] The management device 7 d includes a transmission design information storage unit 71 , a transmission design processing unit 72 d , a network design processing unit 74 , and a network design information storage unit 73 .

[0291] The transmission design processing unit 72d performs transmission design processing in the same manner as the transmission design processing unit 72 to generate a transmission mode candidate list. The transmission design processing unit 72d outputs the generated transmission mode candidate list to the network design processing unit 74. In addition, the transmission design processing unit 72d calculates the OSNR that can be allowed as the signal quality when receiving the signal light sent by the optical transmission device 1c in the same manner as the transmission design processing unit 72. The transmission design processing unit 72d sends the calculated OSNR value to the network design processing unit 74. The network design information storage unit 73 stores the topology information, node information, path information, etc. of the optical transmission path 3 in advance. The information collection unit 62b of the control device 6c can also be used to collect the topology information, node information, path information, etc. of the network of the optical transmission path 3. In this way, network information including the optical frequency utilization efficiency at that moment can always be collected.

[0292] The network design processing unit 74 calls in the transmission mode candidate list and the OSNR value output by the transmission design processing unit 72. In addition, the network design processing unit 74 uses the information stored in the network design information storage unit 73 to perform accommodation design processing of the optical path that requires improved optical frequency utilization efficiency for each transmission mode information included in the transmission mode candidate list. Optical frequency utilization efficiency refers to the efficient use of limited optical frequency resources, and represents, for example, the ratio of frequencies allocated to a certain signal. In addition, the network design processing unit 74 adds information indicating priority to each transmission mode information included in the transmission mode candidate list, for example, based on the optical frequency utilization efficiency of each transmission mode information obtained as a result of the accommodation design processing. In addition, the network design processing unit 74 outputs the transmission mode candidate list to which the information indicating priority is added to the transmission mode selection unit 60c.

[0293] Furthermore, the network design processing unit 74 outputs the value of the OSNR output by the transmission design processing unit 72 to the signal quality determination unit 205 c .

[0294] (Processing of Management Device in Fourth Embodiment)

[0295] Fig.25 This is a flowchart showing the flow of processing performed by the management device 7d of the fourth embodiment. Fig.25 Prior to the flowchart shown in FIG. 1 , information on the physical characteristic parameters of the WSS 301-T, 301-R, the optical amplifiers 302-T, 302-C, 302-R, the optical transmitter 1c, and the optical receiver 2c has been written in the transmission design information storage unit 71 by the information collection unit 62 of the control device 6c. In addition, information on the transmission mode information table 1001t on the transmission side and information on the transmission mode information table 2001r on the reception side have been written in the transmission design information storage unit 71 by the information collection unit 62 of the control device 6c.

[0296] The transmission design processing unit 72d of the management device 7d extracts the common transmission mode information from the information in the transmission mode information table 1001t on the transmission side and the information in the transmission mode information table 2001r on the reception side. The transmission design processing unit 72d performs transmission design processing based on the physical characteristic parameters stored in the transmission design information storage unit 71, and calculates the transmission quality of each of the extracted transmission mode information (step SMd1).

[0297] The transmission design processing unit 72d selects a predetermined number of multiple transmission mode information as candidates in order, for example, from the transmission mode information with high transmission quality based on the calculated transmission quality, generates a transmission mode candidate list including the selected transmission mode information, and outputs the generated transmission mode candidate list to the network design processing unit 74 (step SMd2).

[0298] When performing transmission design processing based on the physical characteristic parameters stored in the transmission design information storage unit 71, the transmission design processing unit 72d calculates the OSNR when the signal light transmitted by the optical transmitting device 1c is received in the optical receiving device 2c (step SMd3). The transmission design processing unit 72d outputs the calculated OSNR value to the network design processing unit 74.

[0299] The network design processing unit 74 imports the transmission mode candidate list and the OSNR value output by the transmission design processing unit 72d. The network design processing unit 74 uses the information stored in the network design information storage unit 73 to perform accommodation design processing of the optical path requiring improvement of optical frequency utilization efficiency for each transmission mode information included in the imported transmission mode candidate list. The network design processing unit 74 adds information indicating priority to the transmission mode information in the order of high optical frequency utilization efficiency based on the optical frequency utilization efficiency of each transmission mode information obtained as a result of the accommodation design processing so that the transmission mode information has a high priority (step SMd4).

[0300] The network design processing unit 74 outputs the generated transmission mode candidate list to the transmission mode selection unit 60c. The network design processing unit 74 outputs the OSNR calculated by the transmission design processing unit 72 to the signal quality determination unit 205c (step SMd5).

[0301] The transmission mode selection process in the fourth embodiment is Fig.23 In the transmission mode selection process of the third embodiment shown in FIG. 1 , the process of step SCc2 of the control device 6c is replaced by the process shown below, and in addition, the same Fig.23 The same processing as shown. That is, in the fourth embodiment, information indicating the priority is added to the transmission mode information included in the transmission mode candidate list. Therefore, in the initial processing of step SCc2, the transmission mode selection unit 60c selects the transmission mode number corresponding to the transmission mode information with the highest priority according to the information indicating the priority added to the transmission mode information included in the transmission mode candidate list. The transmission mode selection unit 60c writes the selected transmission mode number to the internal storage area for storage. In the processing of step SCc2 after the second time, the transmission mode selection unit 60c selects the transmission mode number with the second highest priority among the transmission mode numbers stored in the internal storage area in the transmission mode candidate list, and writes the selected transmission mode number to the internal storage area for storage.

[0302] According to the configuration of the fourth embodiment described above, in the management device 7d of the optical transmission system Sd, the network design processing unit 74 calculates information indicating a priority for each transmission mode information included in the transmission mode candidate list generated by the transmission design processing unit 72d based on the information stored in the network design information storage unit 73. The transmission mode selection unit 60c of the control device 6c selects the transmission mode information in the order of the highest priority according to the information indicating the priority calculated by the network design processing unit 74.

[0303] (Fifth Embodiment)

[0304] Fig.261 is a block diagram showing the configuration of an optical transmission system Se according to a fifth embodiment. In the fifth embodiment, the same reference numerals are used for the same configurations as those in the first to fourth embodiments, and the different configurations are described below. The optical transmission system Se includes an optical transmission device 1c, an optical receiving device 2c, an optical transmission path 3c, and a control device 6e. The control device 6e and the optical transmission device 1c, and the control device 6e and the optical receiving device 2c are connected, for example, via a dedicated circuit or a communication circuit such as the Internet.

[0305] The fifth embodiment is different from the third embodiment in that the control device 6e replaces the information collecting unit 62 with an information collecting unit 62e and also has a transmission design information storage unit 71e and a transmission design processing unit 72e; and the optical transmission system Se does not have a management device 7.

[0306] The information collecting unit 62e is connected to the transmission mode information storage unit 100b, the information accumulation unit 150, the WSS 301-T, 301-R, the optical amplifiers 302-T, 302-C, 302-R of the optical sending device 1c, the transmission mode information storage unit 200b, and the information accumulation unit 250 of the optical receiving device 2c via a communication circuit.

[0307] In addition, the information collecting unit 62e reads out information on physical characteristic parameters from the internal storage area of ​​the information storage unit 150 of the optical sending device 1c, the internal storage area of ​​the information storage unit 250 of the optical receiving device 2c, the internal storage area of ​​WSS301-T, 301-R, and the internal storage area of ​​the optical amplifiers 302-T, 302-C, 302-R, and writes the read physical characteristic parameters into the transmission design information storage unit 71e for storage.

[0308] In addition, the information collecting unit 62e can also read out information on physical characteristic parameters related to the optical transmission path obtained by digital signal processing, and write it into the transmission design information storage unit 71e to store it. The physical characteristic parameters related to the optical transmission path obtained by digital signal processing include wavelength dispersion, polarization mode dispersion, polarization-dependent loss, nonlinear coefficient, etc. These physical characteristic parameters can also be used to perform transmission design of an optical path set as an optical transmission path connecting certain bases.

[0309] In addition, the information collecting unit 62e reads out the information of the transmission mode information table 1001t and the reception mode information table 2001r stored in the transmission mode information storage unit 100b of the optical transmitting device 1c and the transmission mode information storage unit 200b of the optical receiving device 2c, respectively. In addition, the information collecting unit 62e writes the read information of the transmission mode information table 1001t and the reception mode information table 2001r into the transmission design information storage unit 71e to store them.

[0310] The transmission design information storage unit 71e stores the physical characteristic parameters of the optical transmitting device 1c, the optical receiving device 2c, WSS301-T, 301-R, the optical amplifiers 302-T, 302-C, 302-R, the information of the transmitting side transmission mode information table 1001t and the information of the receiving side transmission mode information table 2001r written by the information collecting unit 62e.

[0311] The transmission design processing unit 72e performs transmission design processing for the entire network based on the level diagram between the optical transmitting device 1c and the optical receiving device 2c based on the physical characteristic parameters stored in the transmission design information storage unit 71e, the information in the transmitting side transmission mode information table 1001t, and the information in the receiving side transmission mode information table 2001r.

[0312] In addition, the transmission design processing unit 72e calculates the transmission quality between the optical transmitting device 1c and the optical receiving device 2c as a result of the transmission design processing, and selects a plurality of transmission mode information as candidates based on the calculated transmission quality. In addition, the transmission design processing unit 72e generates a transmission mode candidate list including the selected plurality of transmission mode information, and outputs the generated transmission mode candidate list to the transmission mode selection unit 60c. In addition, the transmission design processing unit 72e calculates the OSNR that can be allowed as the signal quality when the signal light transmitted by the optical transmitting device 1c is received in the optical receiving device 2c as a result of the transmission design processing. In addition, the transmission design processing unit 72e outputs the calculated OSNR value to the signal quality determination unit 205c.

[0313] As described above, the control device 6e in the fifth embodiment includes a transmission design information storage unit 71e and a transmission design processing unit 72e, thereby executing Fig. 22 Processing shown.

[0314] The configuration of the fifth embodiment described above enables transmission design even without using a management device. As a result, it can be easily applied to point-to-point data center / interconnection between data centers, etc., and operability can be improved.

[0315] (Sixth Embodiment)

[0316] Fig. 27 1 is a block diagram showing the configuration of an optical transmission system Sf according to the sixth embodiment. In the sixth embodiment, the same reference numerals are used for the same configurations as those in the first to fifth embodiments, and the different configurations are described below. The optical transmission system Sf includes an optical transmission device 1c, an optical receiving device 2f, an optical transmission path 3c, and a control device 6f. The control device 6f and the optical transmission device 1c, and the control device 6f and the optical receiving device 2f are connected, for example, via a dedicated circuit or a communication circuit such as the Internet.

[0317] The sixth embodiment is different from the fifth embodiment in that the control device 6e further includes a signal quality detection unit 204f and the optical receiving device 2f includes a signal receiving unit 220f instead of the signal receiving unit 220b and does not include the signal quality detection unit 204c.

[0318] The signal receiving unit 220f receives the main signal transmitted through the optical transmission path 3c. The signal receiving unit 220f demodulates the received main signal based on the transmission mode information selected by the transmission mode selecting unit 60c. The signal receiving unit 220f outputs the demodulated main signal to the signal quality detecting unit 204f of the control device 6f.

[0319] The signal quality detection unit 204f detects OSNR as information indicating signal quality from the main signal output from the signal reception unit 220f using the pilot tone signal. The signal quality detection unit 204f outputs information indicating the detected signal quality to the signal quality determination unit 205c.

[0320] The signal quality detection unit 204f may use information obtained from a measuring instrument such as an OTDR, a spectrum analyzer, or a power meter as a signal quality detection method, similarly to the signal quality detection unit 204r.

[0321] According to the configuration of the sixth embodiment described above, it is not necessary to prepare a large number of signal quality detection units for each optical receiving device 2f, and only one signal quality detection unit is required in the control device 6f. Therefore, the cost of the entire system can be reduced when the number of optical receiving devices 2f increases. In addition, it is also possible to improve functionality such as transferring the raw data received in the signal receiving unit 220f as it is to the control device 6f and performing a high-level analysis by machine learning using a deep neural network.

[0322] As described above, the high functionality of DSP for optical transmission leads to an increase in modulation methods, and the baud rate also becomes variable, so that the frequency bands occupied by the transmission mode are different. In addition, due to the progress of optical technology, the area of ​​fully transparent optical networks that reduce electrical relays has expanded, and the topology of the network has also become more complex from point-to-point to rings and meshes. In addition to the perspective of transmission design, the transmission mode selection unit 60c of the fourth embodiment not only performs an accommodation design process that improves the efficiency of optical frequency utilization and seeks to improve the efficiency of the frequency resources of the entire network, but also gives priority to the transmission mode information and selects in order from the transmission mode information with the highest priority. Therefore, it is possible to select the best transmission mode that has high transmission quality, high optical frequency utilization efficiency, and a large OSNR value.

[0323] In addition, in the first to sixth embodiments described above, the transmission mode information is information that combines the modulation method, baud rate, and error correction coding category, but if it is a parameter related to transmission performance, it can be any parameter, for example, it can also include parameters such as the number of carriers.

[0324] Furthermore, when a new error correction technology is developed, the new error correction technology may be added as a parameter to the error correction coding type of the transmission mode information for selection.

[0325] In the configuration of the first embodiment described above, only the transmission mode number is included in the transmission mode candidate information on the transmission side and the reception side, but the configuration of the present invention is not limited to this embodiment. The transmission mode information itself may be included in the transmission mode candidate information on the transmission side and the reception side.

[0326] In the second to sixth embodiments described above, the transmission mode selection units 60 and 60c include the transmission mode number in the transmission mode designation signal and transmit it, but it is also possible to include the transmission mode information in the transmission mode designation signal and transmit it. By doing so, it is not necessary for the optical transmitting devices 1b and 1c to have the transmission mode information storage unit 100b, and similarly, it is not necessary for the optical receiving devices 2b, 2c, and 2f to have the transmission mode information storage unit 200b. Instead, in the third to sixth embodiments, the information of the transmission side transmission mode information table 1001t stored in the transmission mode information storage unit 100b and the information of the reception side transmission mode information table 2001r stored in the transmission mode information storage unit 200b are stored in advance in the transmission design information storage unit 71.

[0327] In the first embodiment described above, the transmission mode information storage unit 100t is configured to store the transmission mode information table 1001t on the transmission side in advance, but the configuration of the present invention is not limited to this embodiment. For example, the control unit 10t may be provided with a write processing unit that receives the user's operation and writes information to the transmission mode information storage unit 100t. The write processing unit receives the user's operation and writes the transmission mode information table 1001t on the transmission mode information storage unit 100t. Furthermore, when the write processing unit finishes writing the transmission mode information table 1001t on the transmission side, it may also send a request to the transmission mode candidate sending unit 101t to use the transmission mode information. Fig.14 The process of step ST1 shown in FIG. 1 is started by a start instruction signal. Fig.14 The processing starts.

[0328] In addition, in the first to sixth embodiments described above, the use of Figure 3 The example of the OTN frame 40 recommended by ITU-T G.709 is shown, but other frames such as those having predetermined fields may also be applied.

[0329] In addition, in the first to fourth embodiments described above, the signal quality detection unit 204r is disposed inside the optical receiving devices 2r, 2ra, and the signal quality detection units 204t, 204b, 204c are disposed inside the optical receiving devices 2t, 2b, 2c, but the signal quality detection units 204r, 204b, 204c may be disposed inside the optical receiving devices 2t, 2b, 2c. However, the signal quality detection units 204r, 204b, 204c may be disposed outside the optical receiving devices such as a measuring instrument.

[0330] Furthermore, in the third embodiment and the sixth embodiment described above, OSNR is used to determine the signal quality, but BER may also be used.

[0331] In the third and fourth embodiments described above, the transmission design processing unit 72 or the network design processing unit 74 calculates the OSNR as the threshold value. However, instead of calculating the OSNR, a predetermined threshold value may be supplied to the signal quality determination unit 205c in advance.

[0332] In addition, in the above-mentioned third embodiment and fourth embodiment, the interface between the management device 7, 7d and the control device 6c, the interface between the control device 6c and the optical sending device 1c, the interface between the control device 6c and the optical receiving device 2c, and the interface between the control device 6c and various modules of the optical transmission path 3c (i.e., WSS301-T, 301-R, optical amplifiers 302-T, 302-C, 302-R) are based on the premise of applying API (Application Programming Interface), but it can also be an existing type of interface such as TL-1 (Transaction Language 1).

[0333] In the configurations of the first to sixth embodiments described above, the signal quality determination units 205r and 205c perform determination processing using a threshold value. In addition, the control information detection unit 211r and the transmission mode candidate reception unit 201r also perform determination processing using a threshold value. In these determination processings, determination processing such as "whether it exceeds the threshold value", "whether it is less than the threshold value", "whether it is above the threshold value", and "whether it is below the threshold value" is only an example, and it can also be replaced by determination processing such as "whether it is above the threshold value", "whether it is below the threshold value", "whether it exceeds the threshold value", and "whether it is less than the threshold value" according to the type of information indicating the signal quality to be determined or the method of determining the threshold value.

[0334] In the first to fourth embodiments described above, the signal quality detection units 204r, 204b, and 204c may detect the bit error information obtained from the error correction decoding units 25r and 220b as signal quality.

[0335] Furthermore, in the above-mentioned first and second embodiments, the transmission mode candidate information may be included in the control information.

[0336] In the first to sixth embodiments described above, when the transmission mode selection unit 103t, the transmission mode selection unit 203t, the transmission mode selection unit 60, and the transmission mode selection unit 60c select the transmission mode number with the highest priority among the common transmission mode numbers, the candidate is selected in a manner that has the largest transmission capacity, but the number of the transmission mode that will become a low power consumption or the number of the transmission mode that has improved optical frequency utilization efficiency may also be selected as the transmission mode number with a high priority. In the case of such a configuration, first, the transmission mode selection unit 103t, the transmission mode selection unit 203t, the transmission mode selection unit 60, and the transmission mode selection unit 60c select the transmission mode number of the candidate of the transmission capacity required during the transmission and reception period among the common transmission mode numbers. The transmission capacity required during the transmission and reception period may also be set in advance. For example, if the transmission capacity required during the transmission and reception period is 200G, the transmission mode numbers for the transmission capacity of 200G are four of "mode 7", "mode 8", "mode 13", and "mode 14". The transmission mode selection unit 103t, the transmission mode selection unit 203t, the transmission mode selection unit 60, and the transmission mode selection unit 60c select a transmission mode with lower power consumption or a transmission mode with better optical frequency utilization efficiency from among the candidates of the transmission capacity required during the selected transmission and reception period. The transmission mode with lower power consumption or the transmission mode with better optical frequency utilization efficiency may be set in advance based on a combination of any one of the modulation method, baud rate, and error correction coding type.

[0337] In the first to sixth embodiments described above, the functional units named "storage units" (i.e., the transmission mode information storage units 100t, 100r, 200r, 200t, 100b, 200b, 61, the transmission design information storage unit 71, and the network design information storage unit 73) are non-volatile storage areas. In addition, among the functional units included in the control information modulation unit 18t and the control information demodulation unit 210r of the first embodiment and the control units 10t, 10r, 20r, 20t, 10ta, 20ra, 10b, 20b, 10c, 20c of the first to fourth embodiments, the functional units other than the functional units named "storage units" described above may be functional units configured by executing a program in a processor such as a CPU (Central Processing Unit).

[0338] Therefore, the control information modulation unit 18t, the control information demodulation unit 210r in the above-mentioned embodiment and the functional unit named "control unit" in the first to fourth embodiments, i.e., the control units 10t, 10r, 20r, 20t, 10ta, 20ra, 10b, 20b, 10c, 20c, can also be implemented in a computer. In this case, it can also be implemented by recording a program for realizing the function in a recording medium that can be read by a computer and reading the program recorded in the recording medium into a computer system and executing it. In addition, the "computer system" described here is a computer system including hardware such as an OS or peripheral devices. In addition, the "computer-readable recording medium" refers to a recording medium of a storage device such as a removable medium such as a floppy disk, a magneto-optical disk, a ROM, a CD-ROM, or a hard disk built into the computer system. Furthermore, the "computer-readable recording medium" may also include a recording medium that dynamically stores the program for a short period of time, such as a communication line when the program is transmitted via a network such as the Internet or a communication circuit such as a telephone line, or a recording medium that stores the program for a certain period of time, such as a volatile memory inside a computer system that serves as a server or client in this case. In addition, the above-mentioned program may be a program for realizing a part of the aforementioned functions, or a program that can realize the aforementioned functions in combination with a program already recorded in a computer system, or a program realized using a programmable logic device such as an FPGA (Field Programmable Gate Array).

[0339] As mentioned above, the embodiment of the present invention is described in detail with reference to the drawings, but the specific configuration is not limited to the embodiment and includes designs and the like within the scope that does not depart from the gist of the present invention.

[0340] Industrial Applicability

[0341] In a DSP that has a variety of transmission modes as its functionality increases, it is possible to select an optimal transmission mode based on various parameters including not only the modulation method but also the baud rate, error correction coding type, number of carriers, and the like.

[0342] Explanation of symbols

[0343] 1t, 1r...optical transmitting device, 2r, 2t...optical receiving device, 3...optical transmission path, 4T, 4R...multiplexing unit, 9...communication circuit, T...transmitting side system, R...receiving side system, S...optical transmission system, 300...optical fiber.

Claims

1. An optical transmission system comprising an optical transmission device and an optical receiving device for receiving a signal transmitted from the optical transmission device via an optical transmission path, and comprising: a transmission mode selection unit for selecting the transmission mode information in order of highest priority from a plurality of transmission mode information common to the transmission performance of the optical transmitting device and the optical receiving device, which are transmission mode information that is a combination of a plurality of parameters related to transmission performance including at least a modulation method, a baud rate, and an error correction coding type, and which is obtained by mutually notifying the optical transmitting device and the optical receiving device of each applicable transmission mode information; a signal transmitting unit that transmits the modulated signal to the optical receiving device based on the selected transmission mode information; as well as A signal receiving unit receives the signal and demodulates the received signal based on the transmission mode information selected by the transmission mode selecting unit.

2. The optical transmission system according to claim 1, wherein: Also available: a signal quality detection unit configured to detect the signal quality of the received signal; and a signal quality determination unit configured to determine whether the signal quality of the signal is acceptable based on information indicating the signal quality detected by the signal quality detection unit, The transmission mode selection unit selects the transmission mode information having the next highest priority when the signal quality determination unit determines that the signal quality of the signal is not acceptable.

3. The optical transmission system according to claim 1, wherein: The optical transmitting device comprises: a transmission mode candidate sending unit that sends transmission-side transmission mode candidate information including the transmission mode information of the optical transmitting device to the optical receiving device; a transmission mode candidate receiving unit that receives, from the optical receiving device, reception-side transmission mode candidate information including the transmission mode information of the optical receiving device; as well as The transmission mode selection unit, The light receiving device comprises: a transmission mode candidate receiving unit configured to receive the transmission side transmission mode candidate information from the optical transmission device; a transmission mode candidate sending unit which sends the receiving-side transmission mode candidate information to the optical transmission device when the transmission mode candidate receiving unit receives the transmission-side transmission mode candidate information; as well as The transmission mode selection unit.

4. An optical transmission system comprising an optical transmission device and an optical receiving device for receiving a signal transmitted from the optical transmission device via an optical transmission path, and comprising: a transmission mode selection unit that selects the transmission mode information in order of priority from a plurality of transmission mode information that is a combination of a plurality of parameters related to transmission performance and is common to the transmission performance of the optical transmitting device and the optical receiving device; a signal transmitting unit that transmits the modulated signal to the optical receiving device based on the selected transmission mode information; as well as a signal receiving unit that receives the signal and demodulates the received signal based on the transmission mode information selected by the transmission mode selecting unit, The transmission mode candidate transmitting unit of the optical transmitting device superimposes the transmission side transmission mode candidate information including the transmission mode information of the optical transmitting device and a pilot tone signal which is a signal sequence having power concentrated at one or more specific frequencies, and transmits the superimposed transmission mode candidate information to the signal transmitting unit. The transmission mode candidate receiving unit of the optical receiving device receives the transmission mode candidate information on the transmission side superimposed on the pilot tone signal received by the signal receiving unit.

5. An optical transmission system comprising an optical transmission device and an optical receiving device for receiving a signal transmitted from the optical transmission device via an optical transmission path, and comprising: a transmission mode selection unit that selects the transmission mode information in order of priority from a plurality of transmission mode information that is a combination of a plurality of parameters related to transmission performance and is common to the transmission performance of the optical transmitting device and the optical receiving device; a signal transmitting unit that transmits the modulated signal to the optical receiving device based on the selected transmission mode information; as well as a signal receiving unit that receives the signal and demodulates the received signal based on the transmission mode information selected by the transmission mode selecting unit, The transmission mode candidate transmitting unit of the optical transmitting device writes the transmission side transmission mode candidate information including the transmission mode information of the optical transmitting device into a predetermined field of the signal frame of the main signal included in the signal and transmits it to the signal transmitting unit, The transmission mode candidate receiving section of the optical receiving device reads the transmission mode candidate information on the transmitting side included in the predetermined field of the signal frame of the main signal.

6. An optical transmission system comprising an optical transmission device and an optical receiving device for receiving a signal transmitted from the optical transmission device via an optical transmission path, and comprising: a transmission mode selection unit that selects the transmission mode information in order of priority from a plurality of transmission mode information that is a combination of a plurality of parameters related to transmission performance and is common to the transmission performance of the optical transmitting device and the optical receiving device; a signal transmitting unit that transmits the modulated signal to the optical receiving device based on the selected transmission mode information; as well as a signal receiving unit that receives the signal and demodulates the received signal based on the transmission mode information selected by the transmission mode selecting unit, The optical transmission system further comprises a control device, The control device includes the transmission mode selection unit, When the transmission mode information is selected, the transmission mode selection unit generates a transmission mode designation signal that designates the selected transmission mode information, and transmits the generated transmission mode designation signal to the optical transmitting device and the optical receiving device. the optical transmitting device and the optical receiving device operate in a transmission mode corresponding to the transmission mode designation signal transmitted from the transmission mode selection unit, The optical transmission system further comprises a management device, The management device comprises: a transmission design information storage unit that stores information on various modules provided in the optical transmission path, physical characteristic parameters of the optical transmitting device and the optical receiving device, and the transmission mode information of the optical transmitting device and the optical receiving device; and a transmission design processing unit, which calculates the transmission quality based on the physical characteristic parameter for each of the transmission mode information, generates a transmission mode candidate list including a plurality of transmission mode information selected based on the calculated transmission quality, and sends the generated transmission mode candidate list to the control device, The transmission mode selection unit of the control device selects the transmission mode information in order of priority from the received transmission mode candidate list.

7. An optical transmission system comprising an optical transmission device and an optical receiving device for receiving a signal transmitted from the optical transmission device via an optical transmission path, and comprising: a transmission mode selection unit that selects the transmission mode information in order of priority from a plurality of transmission mode information that is a combination of a plurality of parameters related to transmission performance and is common to the transmission performance of the optical transmitting device and the optical receiving device; a signal transmitting unit that transmits the modulated signal to the optical receiving device based on the selected transmission mode information; as well as a signal receiving unit that receives the signal and demodulates the received signal based on the transmission mode information selected by the transmission mode selecting unit, The optical transmission system further comprises a control device, The control device includes the transmission mode selection unit, When the transmission mode information is selected, the transmission mode selection unit generates a transmission mode designation signal that designates the selected transmission mode information, and transmits the generated transmission mode designation signal to the optical transmitting device and the optical receiving device. the optical transmitting device and the optical receiving device operate in a transmission mode corresponding to the transmission mode designation signal transmitted from the transmission mode selection unit, The optical transmission system further comprises a management device, The management device comprises: a transmission design information storage unit that stores information on various modules provided in the optical transmission path, physical characteristic parameters of the optical transmitting device and the optical receiving device, and the transmission mode information of the optical transmitting device and the optical receiving device; a transmission design processing unit that calculates transmission quality based on the physical characteristic parameter for each of the transmission mode information and generates a transmission mode candidate list including a plurality of transmission mode information selected based on the calculated transmission quality; A network design information storage unit, which collects any one or all of the network information including the topology information, node information, and path information of the optical transmission path, and stores the collected network information; as well as a network design processing unit that performs accommodation design processing of an optical path requiring improvement of network utilization efficiency using the network information for each of the transmission mode information, thereby sending the transmission mode candidate list to which information indicating a priority is attached for each of the transmission mode information to the control device, The transmission mode selection unit of the control device selects the transmission mode information in order of priority from the received transmission mode candidate list.

8. An optical transmission system comprising an optical transmission device and an optical receiving device for receiving a signal transmitted from the optical transmission device via an optical transmission path, and comprising: a transmission mode selection unit that selects the transmission mode information in order of priority from a plurality of transmission mode information that is a combination of a plurality of parameters related to transmission performance and is common to the transmission performance of the optical transmitting device and the optical receiving device; a signal transmitting unit that transmits the modulated signal to the optical receiving device based on the selected transmission mode information; as well as a signal receiving unit that receives the signal and demodulates the received signal based on the transmission mode information selected by the transmission mode selecting unit, The optical transmission system further comprises a control device, The control device also has: a transmission design information storage unit that stores information on various modules provided in the optical transmission path, physical characteristic parameters of the optical transmitting device and the optical receiving device, and the transmission mode information of the optical transmitting device and the optical receiving device; and a transmission design processing unit that calculates the transmission quality based on the physical characteristic parameter for each of the transmission mode information, generates a transmission mode candidate list including a plurality of transmission mode information selected based on the calculated transmission quality, and outputs the generated transmission mode candidate list to the transmission mode selection unit, The transmission mode selection unit selects the transmission mode information in order of priority from the output transmission mode candidate list.

9. The optical transmission system according to claim 8, wherein: The control device comprises: a signal quality detection unit configured to detect the signal quality of the received signal; and a signal quality determination unit configured to determine whether the signal quality of the signal is acceptable based on the information indicating the signal quality detected by the signal quality detection unit, The transmission mode selection unit selects the transmission mode information having the next highest priority when the signal quality determination unit determines that the signal quality of the signal is not acceptable.

10. A transmission mode selection method in an optical transmission system including an optical transmission device and an optical receiving device for receiving a signal transmitted from the optical transmission device via an optical transmission path, wherein: The transmission mode information is selected in order of highest priority from among a plurality of transmission mode information common to the transmission performance of the optical transmitting device and the optical receiving device, which are transmission mode information that is a combination of a plurality of parameters related to transmission performance including at least a modulation method, a baud rate, and an error correction coding type, and which is obtained by mutually notifying the optical transmitting device and the optical receiving device of each applicable transmission mode information, sending a modulated signal to the optical receiving device based on the selected transmission mode information, The signal is received, and the received signal is demodulated based on the transmission mode information selected by the transmission mode selection unit.

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