Code conversion system and method based on coherent optical orthogonal frequency division multiplexing system

Abstract

The invention provides a code conversion system and method based on a coherent light orthogonal frequency division multiplexing system, and the system comprises a first low-loss band-pass filter which is used for processing an electric signal obtained after 16QAM signal conversion and then transmitting the processed electric signal to a pump laser CW1; the second low-loss band-pass filter is used for processing the electric signal converted from the QPSK signal and then sending the processed electric signal to the pump laser CW1; the pump laser CW1 is used for loading the output of the first low-loss band-pass filter and the output of the second low-loss band-pass filter to the optical laser; the first high-order nonlinear optical fiber HNLF1 is used for coupling the output of the optical laser and the output of the pump laser CW2; the second high-order nonlinear optical fiber HNLF2 is used for coupling the output of the first high-order nonlinear optical fiber and the output of the pump laser CW3; and the OFDM demodulator is used for demodulating and outputting the output of the second high-order nonlinear optical fiber.

Description

Technical Field

[0001] The present invention belongs to the field of optical communication technology, and in particular relates to a coding conversion system and method based on a coherent optical orthogonal frequency division multiplexing system. Background Art

[0002] The statements in this section merely provide background information related to the present invention and do not necessarily constitute prior art.

[0003] Orthogonal frequency division multiplexing (OFDM) is a multi-carrier transmission technology. Unlike traditional single carriers, OFDM uses a multi-carrier approach to transmit information within the allocated bandwidth while transmitting data streams using low-rate subcarriers. OFDM is widely used in optical communication systems because of its strong anti-interference ability, high dispersion and polarization mode dispersion (PMD) capabilities, spectrum utilization and considerable scalability. OFDM technology has been studied and implemented in the communication industry for a decade in applications such as digital video broadcasting (DVB), digital audio broadcasting (DAB), wired and wireless communication systems. Coherent multi-band sub-wavelength optical switching orthogonal frequency division multiplexing (MB-OFDM) super-channel operation at 100 Gbps has also been investigated. Coherent all-optical orthogonal frequency division multiplexing (AO-OFDM) systems for multi-Tbit / s passive optical networks (PONs) have also been proposed to increase downstream data rates for users. Coherent optical OFDM (CO-OFDM) is a communication system that combines coherent optical with high receiver sensitivity and OFDM technology with high spectral efficiency. CO-OFDM system has strong channel estimation and compensation capabilities. In the case of high-speed and large-capacity data exchange in optical fiber transmission systems, the next generation of mobile communications requires higher speed and bandwidth. In this regard, the multi-volume chaotic encryption scheme proposes a phase noise suppression method to enhance system performance. CO-OFDM can prove to be an effective technology for the next generation of mobile communications.

[0004] All-optical wavelength conversion (AOWC) realizes multiplexing in wavelength conversion fiber transmission systems. Wavelength conversion (WC) technology is essential for effectively utilizing bandwidth of fiber transmission missions and providing flexible routing. Therefore, AOWC plays an important role in next-generation optical systems and networks to achieve continuously enhanced routing and provide better network characteristics. WC methods include optical-electrical-optical (O / E / O) methods and full-optical domain methods. The traditional O / E / O WC method takes a considerable amount of time and the response speed of optoelectronic devices is slow. For large amounts of information and to meet more stringent requirements in terms of transmission speed, AOWC is more suitable for applications.

[0005] Traditional information modulation format conversion requires demodulating the optical signal into an electrical signal, demodulating the information, and then remodulating the information in a new modulation format for transmission. The current optoelectronic conversion part is relatively complicated, and when the information transmission system does not have a matching 16QAM receiver, the corresponding solution is no longer applicable. In addition, the existing all-optical modulation format conversion solution cannot achieve wavelength multicasting, and the two converted QPSK signals also have different and poor quality problems. Summary of the invention

[0006] In order to overcome the shortcomings of the above-mentioned prior art, the present invention provides a coding conversion system and method based on a coherent optical orthogonal frequency division multiplexing system, which simplifies the optoelectronic conversion part, and finally realizes the signal format conversion from one 16QAM decomposition into two identical QPSK signals through the four-wave mixing effect generated in the HNLF and the self-phase modulation and cross-phase modulation effects generated.

[0007] To achieve the above-mentioned purpose, one or more embodiments of the present invention provide the following technical solutions: A code conversion system based on a coherent optical orthogonal frequency division multiplexing system, comprising: a first low-loss bandpass filter, used to process the electrical signal converted from the orthogonal amplitude modulation signal and send it to a first pump laser;

[0008] A second low-loss bandpass filter is used to process the electrical signal converted from the quadrature phase shift keying signal and then send it to the first pump laser;

[0009] A first pump laser is used to load the outputs of the first low-loss bandpass filter and the second low-loss bandpass filter to the optical laser;

[0010] a first high-order nonlinear optical fiber for coupling the output of the optical laser with the output of the second pump laser;

[0011] A second high-order nonlinear optical fiber, used for coupling the output of the first high-order nonlinear optical fiber and the output of the third pump laser;

[0012] The OFDM demodulator is used to demodulate and output the output of the second high-order nonlinear optical fiber.

[0013] A second aspect of the present invention provides a coding conversion method based on a coherent optical orthogonal frequency division multiplexing system, comprising:

[0014] Preprocessing and converting the quadrature amplitude modulation signal and the quadrature phase shift keying signal and passing them through a first low-loss bandpass filter and a second low-loss bandpass filter to form an orthogonal electrical signal;

[0015] Loading the obtained electrical signal onto the optical laser via a first pump laser;

[0016] The output of the optical laser and the output of the second pump laser are coupled through a first high-order nonlinear optical fiber;

[0017] The output of the first high-order nonlinear optical fiber and the output of the second pump laser are coupled via the second high-order nonlinear optical fiber;

[0018] The OFDM demodulator demodulates the coupled signal output by the second high-order nonlinear optical fiber and then outputs it.

[0019] One or more of the above technical solutions have the following beneficial effects:

[0020] In the present invention, the photoelectric conversion part is simplified, and the signal format conversion from one 16QAM decomposition to two identical QPSK signals is finally achieved through the four-wave mixing effect and the self-phase modulation and cross-phase modulation effects generated in the HNLF.

[0021] The solution of the present invention is applicable when the information transmission system does not match the 16QAM receiver, and can realize wavelength multicast, that is, when information is sent from one sender to multiple receivers, the system is also applicable.

[0022] Advantages of additional aspects of the present invention will be given in part in the following description, and in part will become obvious from the following description, or will be learned through practice of the present invention. BRIEF DESCRIPTION OF THE DRAWINGS

[0023] The accompanying drawings in the specification, which constitute a part of the present invention, are used to provide a further understanding of the present invention. The exemplary embodiments of the present invention and their descriptions are used to explain the present invention and do not constitute improper limitations on the present invention.

[0024] Figure 1 This is a schematic diagram of a coding conversion system based on a coherent optical orthogonal frequency division multiplexing system in Embodiment 1 of the present invention;

[0025] Figure 2 This is the constellation diagram after coding conversion in the first embodiment of the present invention. DETAILED DESCRIPTION

[0026] It should be noted that the following detailed descriptions are exemplary and are intended to provide further explanation of the present invention. Unless otherwise specified, all technical and scientific terms used herein have the same meanings as those commonly understood by those skilled in the art to which the present invention belongs.

[0027] It should be noted that the terms used herein are for describing specific embodiments only and are not intended to be limiting of exemplary embodiments according to the present invention.

[0028] In the absence of conflict, the embodiments of the present invention and the features of the embodiments may be combined with each other.

[0029] Embodiment 1

[0030] like Figure 1-Figure 2 As shown, this embodiment discloses a code conversion system based on a coherent optical orthogonal frequency division multiplexing system, comprising: a first low-loss bandpass filter, used to process the electrical signal converted from the orthogonal amplitude modulation signal and then send it to the first pump laser CW1;

[0031] A second low-loss bandpass filter is used to process the electrical signal converted from the quadrature phase shift keying signal and then send it to the first pump laser CW1;

[0032] A first pump laser CW1, used to load the outputs of the first low-loss bandpass filter and the second low-loss bandpass filter into the optical laser;

[0033] a first high-order nonlinear fiber HNLF1, for coupling the output of the optical laser with the output of the second pump laser CW2;

[0034] A second high-order nonlinear optical fiber HNLF2, used for coupling the output of the first high-order nonlinear optical fiber HNLF1 and the output of the third pump laser CW3;

[0035] The OFDM demodulator is used to demodulate and output the output of the second high-order nonlinear optical fiber HNLF2.

[0036] In this embodiment, there are 128 available subcarriers at the OFDM transmitter, 80 of which are used as data-carrying subcarriers for QPSK and 16QAM modulation. The number of subcarriers per port for QPSK and 16QAM is set to 40, located at 25-64 and 65-104 respectively, and the remaining subcarriers are set to zero, thereby creating a guard band around the carrier to prevent inter-symbol interference. The average power of OFDM is set to 15dBm and the bit rate is set to 40Gbit / s.

[0037] The original signal at the transmitting end is modulated by a pseudo-random bit sequence (PRBS) with a length of 215-1, and the digital signal is obtained by using the inverse Fourier transform (IFFT). By adding a cyclic prefix (CP) parallel to the serial and digital and analog parallel, two orthogonal electrical signals can be obtained, and the electrical signals are loaded onto the original optical CW1 through two double-sided Mach-Zehnder modulators (MZM). Among them, the number of points of the FFT at the OFDM demodulator is 128.

[0038] Specifically, the first pump laser CW1 is located at f s =193.0THz, the initial phase is zero, the average power is 10dBm, and the bandwidth is 0.1THz.

[0039] In this embodiment, the outputs of CW1 and CW2 are coupled and enter HNLF 1. In HNLF 1, the outputs pass through the first bandpass filter BPF, the first amplifier and the second bandpass filter BPF in sequence to complete four-wave mixing.

[0040] The center frequency f of the second pump laser CW2 CW2 =193.14THz, average power is 22.5dBm, and linewidth is zero.

[0041] Specifically, the generated idler signal is obtained using the first bandpass filter (BPF) and the first amplifier, the center frequency of the first bandpass filter (BPF) is 193.18THz, and the bandwidth is 40GHz. The gain and noise of the first amplifier are 20dB and 4dB respectively. Then, the generated idler signal light is coupled with CW3, enters HNLF2, and sequentially passes through the third bandpass filter BPF, the second amplifier, and the fourth bandpass filter BPF for the second four-wave mixing.

[0042] CW3 is located at the center frequency f cw3 =193.22THz, the power is set to 22.5dBm, the line width is zero, and the light wave that has completed the wavelength conversion can be obtained after filtering and amplification. The center frequency of the third bandpass filter and the fourth bandpass filter is set to 193.26THz. The optical signal is coherently received, and the final wavelength of the 16QAM and QPSK signals after all-optical wavelength conversion can be obtained at the output end of the OFDM demodulator.

[0043] 16QAM and QPSK signals are divided into two outputs, one of which is output at 90° to obtain the imaginary part; the other output obtains the real part; the imaginary part and the real part are processed by LPF respectively, and then processed by FFT together and then converted to parallel-to-serial.

[0044] Embodiment 2

[0045] The purpose of this embodiment is to provide a coding conversion method based on a coherent optical orthogonal frequency division multiplexing system, including:

[0046] Preprocessing and converting the quadrature amplitude modulation signal and the quadrature phase shift keying signal and passing them through a first low-loss bandpass filter and a second low-loss bandpass filter to form an orthogonal electrical signal;

[0047] Loading the obtained electrical signal onto the optical laser via a first pump laser;

[0048] The output of the optical laser and the output of the second pump laser are coupled through a first high-order nonlinear optical fiber;

[0049] The output of the first high-order nonlinear optical fiber and the output of the second pump laser are coupled via the second high-order nonlinear optical fiber;

[0050] The OFDM demodulator demodulates the coupled signal output by the second high-order nonlinear optical fiber and then outputs it.

[0051] In this embodiment, the original signal is modulated by a pseudo-random bit sequence PRBS, and the digital signal is obtained by using inverse Fourier transform. By adding cyclic prefixes in parallel with the serial and in parallel with the digital and analog, two orthogonal electrical signals are obtained.

[0052] In this embodiment, the first pump laser loads the outputs of the first low-loss bandpass filter and the second low-loss bandpass filter to two double-sided Mach-Zehnder modulators of the optical laser respectively.

[0053] In this embodiment, the idler signal is obtained by using the first bandpass filter and the first amplifier, and the idler signal is coupled with the third pump laser.

[0054] Although the above describes the specific implementation mode of the present invention in conjunction with the accompanying drawings, it is not intended to limit the scope of protection of the present invention. Those skilled in the art should understand that various modifications or variations that can be made by those skilled in the art on the basis of the technical solution of the present invention without creative work are still within the scope of protection of the present invention.

Claims

1. A coding conversion system based on coherent optical orthogonal frequency division multiplexing system, characterized in that: include: A first low-loss bandpass filter is used to process the electric signal converted from the quadrature amplitude modulation signal and then send it to the first pump laser; A second low-loss bandpass filter is used to process the electrical signal converted from the quadrature phase shift keying signal and then send it to the first pump laser; A first pump laser is used to load the outputs of the first low-loss bandpass filter and the second low-loss bandpass filter to the optical laser; a first high-order nonlinear optical fiber for coupling the output of the optical laser with the output of the second pump laser; A second high-order nonlinear optical fiber, used for coupling the output of the first high-order nonlinear optical fiber and the output of the third pump laser; The OFDM demodulator is used to demodulate and output the output of the second high-order nonlinear optical fiber.

2. A code conversion system based on coherent optical orthogonal frequency division multiplexing system as claimed in claim 1, characterized in that: The original signal of the OFDM transmitter is modulated by a pseudo-random bit sequence PRBS. The digital signal is obtained by using inverse Fourier transform. By adding cyclic prefixes in parallel with the serial and in parallel with the digital and analog, two orthogonal electrical signals are obtained.

3. The coding conversion system based on coherent optical orthogonal frequency division multiplexing system as claimed in claim 1, characterized in that: The first pump laser loads the outputs of the first low-loss bandpass filter and the second low-loss bandpass filter to two double-sided Mach-Zehnder modulators of the optical laser respectively.

4. The coding conversion system based on coherent optical orthogonal frequency division multiplexing system as claimed in claim 1, characterized in that: The output of the first high-order nonlinear optical fiber passes through a first bandpass filter, a first amplifier, and a second bandpass filter in sequence.

5. A code conversion system based on coherent optical orthogonal frequency division multiplexing system as claimed in claim 4, characterized in that: An idler signal is obtained by using a first bandpass filter and a first amplifier, and the idler signal is coupled with a third pump laser.

6. The coding conversion system based on coherent optical orthogonal frequency division multiplexing system as claimed in claim 1, characterized in that: The output of the second high-order nonlinear optical fiber is input into the OFDM demodulator after passing through the third bandpass filter, the second amplifier and the fourth bandpass filter in sequence.

7. A coding conversion method based on coherent optical orthogonal frequency division multiplexing system, characterized in that: include: Preprocessing and converting the quadrature amplitude modulation signal and the quadrature phase shift keying signal and passing them through a first low-loss bandpass filter and a second low-loss bandpass filter to form an orthogonal electrical signal; Loading the obtained electrical signal onto the optical laser via a first pump laser; The output of the optical laser and the output of the second pump laser are coupled through a first high-order nonlinear optical fiber; The output of the first high-order nonlinear optical fiber and the output of the second pump laser are coupled via the second high-order nonlinear optical fiber; The OFDM demodulator demodulates the coupled signal output by the second high-order nonlinear optical fiber and then outputs it.

8. The method for transcoding based on coherent optical orthogonal frequency division multiplexing system as claimed in claim 7, characterized in that: The original signal is modulated by a pseudo-random bit sequence PRBS, and the digital signal is obtained by inverse Fourier transform. By adding cyclic prefixes in parallel with serial and in parallel with digital and analog, two orthogonal electrical signals are obtained.

9. The method for transcoding based on coherent optical orthogonal frequency division multiplexing system as claimed in claim 7, characterized in that: An idler signal is obtained by using a first bandpass filter and a first amplifier, and the idler signal is coupled with a third pump laser.

10. A method for transcoding based on a coherent optical orthogonal frequency division multiplexing system as claimed in claim 8, characterized in that: The first pump laser loads the outputs of the first low-loss bandpass filter and the second low-loss bandpass filter to two double-sided Mach-Zehnder modulators of the optical laser respectively.

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