| Along with the emergence of a variety of new services,the amount of data that needs to be transmitted and exchanged over a communications optical network has exploded.Establishing a high-speed,large-capacity,long-distance communication system has become an increasingly urgent matter.This requires us to study higher-order modulation techniques and optical signal regeneration technologies to serve new types of network construction.WDM systems are a very effective method of increasing channel capacity.Limited by the fiber and optical device itself,the number of wavelengths available in a real optical network is limited,and wavelength conversion can increase the flexibility of the optical network and reduce the blocking rate.Signals of different modulation formats have their own advantages.High-order modulation signals can carry more information at the same symbol rate so that they can reach high spectrum utilization.They are widely used in backbone networks that need to transmit massive amounts of data.Low-order signals are more reliable because of their high anti-noise ability and lower cost of demodulation.They are solutions for short-range communication with complex network environments and more cost-sensitive.Faced with a optical network where multiple modulation formats coexist,format conversion can allocate resources reasonably according to different needs.As a all-optical processing technology,the phase-sensitive amplifier is not limited by the"electronic bottleneck" and can handle very high bit rates.It can be used as an optical amplifier to theoretically achieve NF=0 noise-free amplification,which can be applied to signal regeneration,phase quantization,format conversion and other aspects.This thesis takes phase-sensitive amplifier as the research object.Based on the four-wave mixing effect and the mathematical model of one-mode PSA and two-mode PSA,the phase regeneration,wavelength conversion and format conversion of high-order modulation signals are gradually researched.The main research work and contents of this thesis are as follows:1)High-order modulation signal reproduction with wavelength conversion function.According to the basic principle of phase-sensitive amplification,the regeneration of the M-order modulated signal requires the participation of(M-1)harmonics,and the pump and signal need to satisfy the phase matching condition.There are two conventional methods for satisfying the phase matching condition in the PSA:(1)Signal and pump one generate M-order harmonics through FWM,and M-order harmonics are inj ected into the inj ection-locked laser to obtain the required pump two;2)The pump one,the carrier wave and the pump two are generated by the optical comb,and then the carrier is modulated with the signal.The experiment involved in this paper is to produce a light comb by Method 2.The input signal of this experiment is a high-order phase-modulated signal,and QPSK and 8PSK are modulated by the experimental platform as the source signal in the regeneration experiment.The two pump and QPSK signals are amplified by EDFA and enter the high-fidelity fiber.Four-wave mixing produces multiple harmonics.The conjugated harmonics and the original signal contain the same information but the wavelengths are different.We use conjugate harmonics.For the object to be regenerated,two harmonics with the same phase as the original signal are selected as the pump,which is filtered by WSS and sent to another high-nonlinear fiber.The three will generate four-wave mixing and finally realize QPSK signal regeneration.At the same time achieve the goal of wavelength conversion.2)The 16QAM signal format is converted to two PAM4 signals.The MQAM signal and the PAM4 signal are representative Modulated signals of long-distance communication and short-range communication.This thesis first introduces the mathematical basis of phase-shifting amplifiers for format conversion.Taking QPSK as an example,it shows that this scheme can convert the QPSK signal without information redundancy into two orthogonal BPSK signals.The simulation device with modulation format of 16QAM is designed.Compared to the data before and after conversion,the system can convert 16QAM signal into two PAM4 signals,and the BER of the signal can be improved by conversion.The scheme interferes by means of harmonics and signal separation,making the power ratio of signals and harmonics easy to control.The amplitude ratio m of the signal and conjugate harmonics has a great influence on the EVM of the converted PAM4 signal.Therefore,the variation law of the input and output phases under different m values is calculated by MATLAB and verified by the simulation program. |
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