CN101807957B - Ultra-long span light transmission system - Google Patents

Abstract

The invention discloses an ultra-long-span optical transmission system. The system includes: a signal processing module, which is used to inversely multiplex high-speed electrical signals, generate 12 low-rate electrical signals, and convert the 12 low-rate electrical signals to output to the optical modulation module; the optical modulation module is used to use the 12 low-rate electrical signals output by the signal processing module to modulate the continuous light, generate 12 optical signals with a return-to-zero pattern, and complex the 12 optical signals It is used to form 1 channel signal and output to the optical fiber for transmission; the optical receiving module is used to demultiplex the 1 channel optical signal sent by the optical fiber into 12 channels of optical signals and convert them into electrical signals, and output 12 channels of electrical signals for demodulation module; a demodulation module, used to demodulate the 12 electrical signals output by the optical receiving module, and restore the original high-speed electrical signal. The system uses the IFFT module to process the input signal, realizing the inverse multiplexing of the signal to be transmitted, and the equipment is simple, low in cost and high in reliability.

Description

An ultra-long-span optical transmission system

technical field

The invention relates to the field of optical communication, in particular to an ultra-long-span optical transmission system.

Background technique

The ultra-long span is a point-to-point transmission system without any relay equipment, and the operation and maintenance costs are low. Solve the network construction needs of many special occasions, such as national power system communications, oil exploration communications, inter-island networking, etc. Since the transmission scheme without electric relay is adopted, there is no electric power injection in the line, so there is no need to take special safety measures for high voltage, which maximizes the reliability of the system. At the same time, the transmission between the spans only increases the optical fiber, which greatly reduces the cost of bandwidth construction. The ultra-long span system has a simple structure, which reduces the difficulty of installation and the cost of technical training and equipment maintenance.

For ultra-long-span optical transmission systems, there have been many researches in the world, but there are still many problems to be solved: compensation for long-distance transmission loss; control of chromatic dispersion and polarization mode dispersion in transmission; Non-linear effects; selection of transmission patterns, etc. At present, most of the foreign research is based on the optimization of the span structure and the configuration of the optical amplifier, and most of them are aimed at the submarine cable system. Its products are not only expensive, but also not suitable for domestic applications, especially in the construction of the national power system communication network.

The prior art [1] (see Journal of Lightwave Technology, Jean Armstrong, vol.27, 2009: 189-204) describes an ultra-long-distance optical transmission system based on optical orthogonal frequency division multiplexing (OOFDM), The system has strong anti-dispersion performance and high spectral efficiency. However, in addition to the Fourier transform module, this system also needs complex signal processing technologies such as digital-to-analog/analog-to-digital conversion, up-conversion, signal bias, and equalization, which requires extremely high hardware requirements.

Contents of the invention

In view of the shortcomings existing in the prior art, the object of the present invention is to provide an ultra-long-span optical transmission system, the ultra-long-span optical transmission system is simple in structure, low in cost, and can reduce data transmission in optical fibers during optical transmission. The bit rate can effectively suppress the dispersion effect and nonlinear effect in the transmission process, and extend the optical transmission span.

In order to achieve the above object, the technical scheme adopted in the present invention is:

An ultra-long-span optical transmission system, the system includes a signal processing module, an optical modulation module, an optical fiber, an optical receiving module, and a demodulation module, and is characterized in that:

A signal processing module, configured to inversely multiplex high-speed electrical signals to generate 12 low-rate electrical signals, and output the 12 low-rate electrical signals to the optical modulation module;

An optical modulation module, configured to use the 12 low-rate electrical signals output by the signal processing module to modulate continuous light, generate 12 optical signals with a return-to-zero pattern, and multiplex the 12 optical signals to output to optical fiber for transmission;

The optical receiving module is used to demultiplex the 1-way optical signal sent by the optical fiber into 12-way optical signals and convert them into electrical signals, and output 12-way electrical signals to the demodulation module;

The demodulation module is used to demodulate the 12 channels of electrical signals output by the optical receiving module, and restore the high-speed electrical signals at the input end of the signal processing module.

An ultra-long-span optical transmission system of the present invention has the advantages and effects compared with the prior art: the system uses an IFFT module to process the input signal, and realizes the inverse multiplexing of the signal to be transmitted; The bit rate of the signal is lower than the actual bit rate of the system, which can resist the dispersion effect caused by high-speed optical communication, and can also effectively suppress the nonlinear effect of optical fiber; the system only sets the IFFT module at the transmitting end and the FFT at the receiving end accordingly The module realizes inverse multiplexing, and the technical complexity is far less than that of the existing technology [1]; the system has simple equipment, low cost and high reliability.

Description of drawings:

FIG. 1 is a schematic block diagram of an ultra-long-span optical transmission system of the present invention.

Fig. 2 is a schematic structural diagram of the signal processing module (1) in Fig. `1.

Fig. 3 is a schematic structural diagram of the light modulation module (2) in Fig. `1.

Fig. 4 is a schematic structural diagram of the light receiving module (4) in Fig. `1.

Fig. 5 is a schematic structural diagram of the demodulation module (5) in Fig. `1.

Detailed ways

The present invention will be described in further detail below in conjunction with accompanying drawing and specific embodiment of description:

Referring to Fig. 1, a kind of ultra-long span optical transmission system of the present invention, it comprises signal processing module 1, optical modulation module 2, optical fiber 3, light receiving module 4, demodulation module 5, described signal processing module 1, It is used to inversely multiplex high-speed electrical signals, generate 12 low-rate electrical signals, and output 12 low-rate electrical signals to the optical modulation module 2; the optical modulation module 2 is used to use the signal processing module 1 to output 12 channels of low-rate electrical signals modulate the continuous light to generate 12 channels of optical signals with return-to-zero patterns, and multiplex the 12 channels of optical signals with return-to-zero patterns into 1 signal, which is output to optical fiber 3 for transmission ; The optical receiving module 4 is used to demultiplex the 1-way optical signal sent by the optical fiber 3 into 12-way optical signal, and the 12-way optical signal is converted into 12-way electrical signal, which is output to the demodulation module 5; The demodulation module 5 described above is used to demodulate the 12 channels of electrical signals output by the optical receiving module 4, and restore the original high-speed electrical signals.

Above-mentioned signal processing module 1, referring to Fig. 2, it specifically comprises: 4-QAM modulator 11, is used for modulating input signal, 4-QAM modulator (11) output port 0* is conjugated with conjugate operator array 12 respectively The input port of the operator #0 and the input port 1* of the 8-IFFT module 13 are connected, and the output port 1* of the 4-QAM modulator 11 is respectively connected to the input port of the conjugate operator #1 of the conjugate operator array 12 and the 8-IFFT module 13 input port 3* connected;

Conjugate operation unit array 12, is made up of 2 conjugate operation units, is used for carrying out conjugate operation to the signal that 4-QAM modulator 11 produces, the output port of conjugate operation unit #0, #1 in conjugate operation array 12 Be connected to ports 5*, 7* of 8-IFFT module 13 respectively;

8-IFFT module 13, for the signal that 4-QAM modulator 11 and conjugate operator array 12 produce carry out inverse fast Fourier transform, the input port 0*, 2*, 4* of 8-IFFT module 13 , 6* are set to zero, and the output ports 0*～7* of the 8-IFFT module 13 are respectively connected to the input ports of the shapers #0～#7 in the shaper array 14;

The shaper array 14 is made up of 8 shapers, and is used for shaping the output signal of the 8-IFFT module 13, and the output ports of the shapers #0, #2, #4, and #6 in the shaper array 14 are respectively connected to the decision The input port of the decision device #0～#3 in the device array 15, the output port of the shaper #1 is respectively connected to the input port of the decision device #4, #8, and the output port of the shaper #3 is connected to the decision device #5 respectively , the input port of #9, the output port of shaper #5 is connected to the input port of decision device #6, #10 respectively, the output port of shaper #7 is connected to the input port of decision device #7, #11 respectively;

The decider array 15 is composed of 12 deciders, and is used for performing threshold judgment on the output signal of the shaper array 14, and outputting an electrical signal of a return-to-zero pattern.

其中X₁ ^*和X₃ ^*分别为X₁和X₃的共轭信号，每次仅两个符号参与8-IFFT运算，即8-IFFT模块13输出信号的速率为10Gbps，且输出信号为实信号。整形器阵列14将输入负信号置零，设整形器阵列14中每个整形器的输入信号为x_m，输出信号x_cm可表示为：x_cm＝x_m(ifx_m≥0)，x_cm＝0(ifx_m≤0)。判决器阵列15中判决器#0、#1、#2、#3的判决门限设置为1/2，当输入信号等于1/2时判为“1”，小于1/2时判为“0”。判决器阵列15中判决器#4、#5、#6、#7的判决门限设置为

当输入信号等于

时判为“1”，小于

时判为“0”。判决器阵列15中判决器#8、#9、#10、#11的判决门限设置为

当输入信号大于

时判为“1”，小于

时判为“0”。判决器阵列15输出12路归零码型电信号，每路信号速率为10Gbps。An implementation example of a signal processing module 1 is as follows: the input port of the 4-QAM modulator 11 is a signal with a single-channel total capacity of 40Gbps, and the symbol rate after 4-QAM modulation becomes 20Gbps, and the conjugate operator array 12 Two conjugate operators carry out conjugate operation to the two symbols obtained by a 4-QAM modulation, and the input port data of the 8-IFFT module 13 can be expressed as:

Wherein X ₁ ^* and X ₃ ^* are the conjugate signals of X ₁ and X ₃ respectively, only two symbols participate in the 8-IFFT operation each time, that is, the rate of the output signal of the 8-IFFT module 13 is 10Gbps, and the output signal is a real Signal. The shaper array 14 sets the input negative signal to zero, assuming that the input signal of each shaper in the shaper array 14 is x _m , the output signal x _cm can be expressed as: x _cm = x _m (if x _m ≥ 0), x _cm = 0 (if x _m ≤ 0). The judgment thresholds of decision devices #0, #1, #2, and #3 in the decision device array 15 are set to 1/2, and when the input signal is equal to 1/2, it is judged as "1", and when it is less than 1/2, it is judged as "0"". The judgment threshold of decision device #4, #5, #6, #7 in the decision device array 15 is set to

When the input signal is equal to

When judged as "1", less than

The time judgment is "0". The judgment threshold of decision device #8, #9, #10, #11 in the decision device array 15 is set to

When the input signal is greater than

When judged as "1", less than

The time judgment is "0". The decider array 15 outputs 12 channels of return-to-zero code pattern electrical signals, and the rate of each signal is 10Gbps.

The above-mentioned optical modulation module 2, referring to Fig. 3, specifically includes: an optical transmitter array 21, which is composed of 12 optical transmitters, and is used to continuously optically modulate the output signal of the decision device array 15, and output 12 return-to-zero patterns light pulse signal;

The optical multiplexer 22 is used to multiplex the 12 channels of optical signals generated by the optical transmitter array 21 into 1 channel of signals, and output them to the optical fiber 3 for transmission.

The above-mentioned optical receiving module 4, referring to FIG. 4, specifically includes: an optical demultiplexer 41, which is used to demultiplex the 1-way optical signal sent by the optical fiber 3, and output 12-way optical signals;

The optical receiver array 42 is composed of 12 optical receivers, and is used for photoelectric conversion and sampling of the 12 optical signals output by the optical demultiplexer 41, and outputs 12 electrical signals. The optical receivers in the optical receiver array 42 The output ports of #0～#3 are connected with the input ports of multipliers #0, #2, #4 and #6 in the multiplier array 52, and the output ports of the optical receivers #4 and #8 are connected with the input ports of the adder array 51 respectively. The two input ports of adder #0 are connected, the output ports of optical receiver #5, #9 are connected with the two input ports of adder 51, the output ports of optical receiver #6, #10 are connected with the output port of adder #2 The two input ports are connected, and the output ports of the optical receivers #7 and #11 are connected with the two input ports of the adder #3.

Above-mentioned demodulation module 5, figure referring to Fig. 5, it specifically comprises: adder array 51, is made up of 4 adders, is used for receiver #4 and #8, #5 and #9, #5 and #9, in optical receiver array 42 The output signals of #6 and #10, #7 and #11 are added, and the output ports of adder #0～#3 are respectively connected to the multiplier #1, #3, #5, #7 in the multiplier array 52 input port;

乘法器阵列52输出8路信号连接到8-FFT模块53的输入端口0*-7*；The multiplier array 52 is made up of 8 multipliers, and is used for multiplying the output signal of the optical receiver #0～#3 in the optical receiver array 42 and the output signal of the adder array 51 by corresponding coefficients, wherein the multiplier # The coefficients of 0, #2, #4, #6 are set to 1/2, and the multiplication coefficients of multipliers #1, #3, #5, #7 are set to

The multiplier array 52 outputs 8 signals and is connected to the input port 0*-7* of the 8-FFT module 53;

8-FFT module 53, for carrying out Fast Fourier Transform to the output signal of multiplier array 52, the output port 1*, 3* of 8-FFT module 53 is connected to two input ports of 4-QAM demodulator 54 ;

The 4-QAM demodulator 54 is used to demodulate the signals of the output ports 1* and 3* of the 8-FFT module (53), and output serial high-speed electrical signals.

The present invention processes the high-speed transmission signal by preprocessing the transmission signal at the transmitting end, converting the transmission signal into a symbol form, and forming 12 code patterns that can be transmitted in the line through arithmetic processing for transmission, and the above-mentioned signal processing An implementation example of the module (1) shows that the code rate of each of the 12-channel signals is 1/4 of the effective information rate of the system.

Claims (3)

1. An ultra-long-span optical transmission system, which includes a signal processing module (1), an optical modulation module (2), an optical fiber (3), an optical receiving module (4), and a demodulation module (5), characterized in that : The signal processing module (1) is used to inversely multiplex the high-speed electrical signals to generate 12 channels of low-rate electrical signals, and output the 12 channels of low-rate electrical signals to the optical modulation module (2), the above-mentioned signal processing module (1) Specifically include: 4-QAM modulator (11), is used for modulating input signal, 4-QAM modulator (11) output port 0* is respectively connected with the input port of conjugate operator #0 in conjugate operator array (12), 8- The input port 1* of the IFFT module (13) is connected, and the output port 1* of the 4-QAM modulator (11) is respectively connected to the input port of the conjugate operator #1 in the conjugate operator array (12) and the input port of the 8-IFFT module (13) Port 3* is connected; Conjugate computing unit array (12), described conjugate computing unit array (12) is made up of 2 conjugate computing units, is used for carrying out conjugate operation to the signal that 4-QAM modulator (11) produces, conjugate operation The output ports of the conjugate operators #0 and #1 in the array (12) are respectively connected to the 5* and 7* ports of the 8-IFFT module (13); 8-IFFT module (13), for carrying out inverse fast Fourier transform to the signal that 4-QAM modulator (11) and conjugate operator array (12) produce, the input port of 8-IFFT module (13) 0*, 2*, 4*, 6* are set to zero, and the output ports 0*~7* of the 8-IFFT module (13) are respectively connected to the input ports of the shapers #0~#7 in the shaper array (14); Shaper array (14), described shaper array (14) is made up of 8 shapers, is used to carry out shaping to 8-IFFT module (13) output signal, shaper #0, # in shaper array (14) 2. The output ports of #4 and #6 are respectively connected to the input ports of decider #0~#3 in the decider array (15), and the output port of shaper #1 is connected to the input of decider #4 and #8 respectively port, the output port of shaper #3 is connected to the input port of decision device #5, #9 respectively, the output port of shaper #5 is connected to the input port of decision device #6, #10 respectively, the output port of shaper #7 The ports are respectively connected to the input ports of decision devices #7 and #11; Decider array (15), described decider array (15) is made up of 12 deciders, is used for carrying out threshold judgment to described shaper array (14) output signal, and outputs the electric signal of return-to-zero pattern; The optical modulation module (2) is used to modulate the continuous light by using the 12 channels of low-rate electrical signals output by the signal processing module (1), generate 12 channels of optical signals with a return-to-zero pattern, and convert the 12 channels of optical signals with a return-to-zero code The optical signal of the type is multiplexed into one optical signal, which is output to the optical fiber (3) for transmission; The optical receiving module (4) is used to demultiplex the 1-channel optical signal sent by the optical fiber (3) into 12-channel optical signals, convert the 12-channel optical signals into 12-channel electrical signals, and output them to the demodulation module (5) ; The demodulation module (5) is used to demodulate the 12 channels of electrical signals output by the optical receiving module (4), and recover the high-speed electrical signals at the input end of the signal processing module (1). The above-mentioned demodulation module (5) specifically includes: Adder array (51), described adder array (51) is made up of 4 adders, is used for receiver #4 and #8, #5 and #9, #6 and #6 in the optical receiver array (42) The output signals of #10, #7 and #11 are added, and the output port of adder #0～#3 is connected to the input of multiplier #1, #3, #5, #7 in the multiplier array (52) respectively port; Multiplier array (52), described multiplier array (52) is made up of 8 multipliers, is used for the output signal of optical receiver #0～#3 in optical receiver array (42) and adder array (51 ) is multiplied by the corresponding coefficient, and the multiplier array (52) outputs 8 signals and is connected to the input port 0*~7* of the 8-FFT module (53); 8-FFT module (53), for carrying out Fast Fourier Transform to the output signal of multiplier array (52), the output port 1*, 3* of 8-FFT module (53) is connected to 4-QAM demodulator Two input ports of (54); The 4-QAM demodulator (54) is used to demodulate the signals of the output ports 1* and 3* of the 8-FFT module (53), and output serial high-speed electrical signals. 2. An ultra-long-span optical transmission system according to claim 1, wherein the optical modulation module (2) specifically includes: an optical transmitter array (21), and the optical transmitter array (21) It consists of 12 optical transmitters, which are used to continuously optically modulate the output signal of the decision array (15), and output 12 channels of optical pulse signals of the return-to-zero pattern; the optical multiplexer (22), used to combine the optical transmitters The 12 optical signals generated by the array (21) are multiplexed into one optical signal, and output to the optical fiber (3) for transmission. 3. An ultra-long-span optical transmission system according to claim 2, characterized in that, the above-mentioned optical receiving module (4) specifically includes: an optical demultiplexer (41) for sending and receiving optical fibers (3) The 1-way optical signal that comes is demultiplexed, and output 12-way optical signal; Optical receiver array (42), described optical receiver array (42) is made up of 12 optical receivers, is used for demultiplexer (41) The output 12-way optical signal is subjected to photoelectric conversion and sampling, and 12-way electrical signal is output, and the output port of optical receiver #0 ~ #3 in the optical receiver array (42) and the multiplier in the multiplier array (52) The input ports of #0, #2, #4, #6 are connected, the output ports of optical receiver #4, #8 are respectively connected with the two input ports of adder #0 in the adder array (51), and the optical receiver The output port of #5, #9 links to each other with two input ports of adder (51), the output port of optical receiver #6, #10 links to each other with two input ports of adder #2, optical receiver #7, The output port of #11 is connected to the two input ports of adder #3.

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