Research On All-Optical Regeneration Technologies Of Vector Signals

The acceleration of 5G commercialization,the introduction and popularization of "big data" and "cloud computing",and the emergence of 4k/8k high-definition video,virtual reality and augmented reality continue to stimulate the growth of data traffic.In order to cope with this pressure,the optical fiber communication network as the basic physical infrastructure adopts vector signals that is modulated by multiple dimensions such as amplitude and phase combined with multiple multiplexing technologies to improve spectrum efficiency and expand system capacity.However,vector signals are highly sensitive to channel noise,which can easily cause a significant reduction in transmission quality and shorten the transmission distance.In this context,it is of great significance to explore efficient signal regeneration schemes.The all-optical signal regeneration technology has the advantages of fast response,high energy efficiency,no need for "optical-electrical-optical" conversion,and high bandwidth provision capability,which has attracted widespread attention in recent decades.Among them,all-optical signal regeneration schemes such as multi-level phase regeneration,multi-level amplitude regeneration and amplitude-phase regeneration have been proposed and continuously improved.It based on non-linear effects such as phase sensitive amplification(PSA)and has a good application prospect.This thesis focuses on all-optical regeneration technology of vector signals,and is committed to alleviating the contradiction between current and future network bandwidth utilization and transmission distance by improving signal quality.Specifically,the main research contents and innovations are as the following:1.An all-optical regeneration scheme for quadrature phase shift keying(QPSK)signals based on vector PSA is proposed.This scheme uses vector PSA to separate the coherent superposition process of hannonics from other non-linear processes,and effectively achieves the optimal phase squeezing performance at low pump power by controlling the polarization angle of the harmonic addition.At the same time,by introducing a subsequent phase-preserving amplitude regeneration device,the output of the phase regeneration process is conjugated and frequency-converted,and finally the amplitude and phase regeneration of the signal with wavelength preservation is completed.Its characteristic is that it has higher system energy efficiency and better phase compression capability under the same pump input compared with the traditional scheme.The simulation results show that,for 10 Gbaud QPSK signals,the spectrum of the harmonic width of is narrower.Unnecessary harmonic components are reduced by about 40 dB in this scheme.In addition,the bit error rate-optical signal-to-noise ratio curve reflects the improvements of the optical signal-to-noise ratio(OSNR)required for reception are approximately 2 dB and 1.1 dB under noisy signal inputs with 13 dB and 18 dB OSNR respectively.It shows potential applications in extending the signal transmission distance.2.A phase regeneration scheme for DP-QPSK/8PSK signal based on conjugate dual-pump PSA is proposed.The scheme realizes the simultaneous regeneration of the orthogonal polarization components of the multi-level phase modulation format signal by the reasonable setting of the input pump and signal frequencies and the reduction of the order of required harmonics addition.The characteristic is that the scheme avoids the complex diversity structure and overcomes the difficulties caused by the harmonic interference introduced by the vector four wave mixing in the process of dual polarization signal regeneration.The simulation results show that,taking the DP-QPSK and DP-8PSK signals of 40 Gbit/s and 60 Gbit/s as an example,under the input phase noise of 15 degrees and 7.5 degrees,approximately 16%and 5%EVM decrease is achieved.In addition,for input phase noise of 20 degrees and 10 degrees,the OSNR reduction required for reception of about 1.9 dB and 2.1 dB is achieved respectively.The improvement of the bit error rate performance of the scheme shows that it can effectively recover the signal quality and improve the noise resistance,and has application value in the large-capacity long-distance transmission network.3.An all-optical regeneration scheme for rectangular quadrature amplitude modulation(QAM)signals based on multi-wave interference is proposed.This scheme uses the pump-assisted self-phase modulation effect to achieve the Fourier series approximation of the staircase response of the signal amplitude.What's more,by analyzing the performance of the staircase response under different order approximations,a hybrid regeneration scheme which connects both high-order and low-order systems is proposed.The characteristic is that the signal amplitude and phase characteristics do not interfere with each other.The signal processing in the same high nonlinear fiber is completed by orthogonal polarization states and opposite propagation directions,which simplifies the system structure and enhances scalability.The simulation results show that the hybrid regeneration scheme can effectively absorb the advantages of the first-order regeneration system and the high-order regeneration system for different levels of noise compression,and reduce the number of cascades when the regeneration effect is unchanged.The EVM of QPSK,16QAM,64QAM signals are all have been effectively improved.Taking the 80 Gbit/s 16QAM signal as an example,after being processed by the hybrid regeneration scheme,it receives 1.1 dB and 2.7 dB reduction of required reception OSNR at the bit error rate threshold at the input of 25 dB and 20 dB OSNR respectively.