Research On All-optical Format Conversion Technology Of Optical Vector Signal

With the introduction of big data,cloud computing,and the concept of"Internet+",a new generation of information and communication technologies has also developed rapidly with the explosive growth of data traffic in communication transmission networks.Optical communication technology is widely used in large-capacity and long-distance communication because of its strong anti-noise ability and large bandwidth capacity.Under the condition that the bandwidth resources are more and more restricted,the advanced modulation signals are widely concerned,researched and applied due to the high spectral efficiency and the fact that the unit symbols can carry more information.When using the electrical signal to complete the information processing,the electron rate can no longer be greatly improved due to the bottleneck limitation of the"electronic rate" and the "scale effect" of the device integration,while the traffic volume in the network requires more bandwidth and signal.Processing rate,however,the photon rate is much higher than the electron rate.There is no bottleneck limitation of "electronic rate" in optical signal processing,so optical signals have strong advantages and development potential in information processing,and have been demonstrated.Since different types of optical transmission networks require different types of modulated signals,and low-order signals are easier to process than higher-order signals,the study of all-optical signal format conversion between different networks is of great significance.This thesis studies the common optical format conversion of several common optical vector signals.The main work and research contents are as follows:1)For the all-optical format conversion of the star 8QAM(Eight Quadrature amplitude modulation)signal,the four-wave mixing is used to generate the idler light conjugated with the signal,and the spectrum shifting device is used to move the idler light to the signal frequency.Then the original signal and the moved idler light are sent to the cross-coupler.Since the coupler has a 90° phase shift effect on the input signal,the signal can be de-multiplexed without changing the gain axis of the PSA(Phase Sensitive Amplifier)process.The de-multiplexed two PAM4(Pulse amplitude modulation)signals are simultaneously obtained from the coupler output.The hierarchically modulated star 8QAM signal format is converted to the PAM4 signal,which on the one hand maintains the integrity of the information,On the other hand,it is advantageous for the OLT(Optical Line Terminal)to selectively distribute information to different ONUs(Optical Network Unit)in the PON(Passive Optical Network)system.2)For the all-optical format conversion of the 8PSK signal,the phase sensitive amplifier and the spectrum shifting device are used to realize the coherent superposition of the original signal and the negative first harmonic to obtain the PAM4 signal in the coupler.The SPM and the coherent superposition are used to convert the PAM4 signal format into the BPSK(Binary Phase Shift Keying)signal to extract the first and second bit information of the 8PSK information coding.The second harmonic and the negative second harmonic are conjugated QPSK(Quadrature Phase Shift Keying)signals,QPSK contains the third bit of 8PSK signal information.The PSA has phase de-multiplexing function,which can de-multiplex QPSK into in-phase BPSK to extract the third bit of information of the 8PSK information coding.The advanced modulation format 8PSK signal is converted into three low-level modulation format BPSK signals,which can improve the anti-noise performance to make the signal the propagate farther,on the other hand,it is beneficial to the bandwidth resource allocation.3)All-optical format conversion for PAM4 signals.The four-level PAM4 signal can be regarded as being superimposed by two OOK(On-off Keying)signals,and the two-level PAM4 signal can be regarded as being obtained by multiplexing and superimposing two BPSK signals.The four-level PAM4 signal can be converted to a two-level PAM4 signal using a non-degenerate PSA format.The two-level PAM4 signal is divided into two branches,one signal is directly sent to the HNLF(High Nonlinear Linear Fiber),and the signal is affected by the SPM when transmitted in the HNLF,and the PAM4 signal with nonlinear phase shift is generated,and the signal is superimposed with the original signal.By adjusting the signal power and phase,it is possible to compress two constellation points on each side of the quadrant into one constellation point to obtain a first BPSK signal.The other PAM4 signal is sent into another HNLF to obtain the PAM4 signal pre-disturbed by the SPM,and then processed in a manner similar to obtaining the first BPSK signal to obtain the second BPSK signal,and the two-way BPSK is adjusted.The power of the signal is realized by the cross-coupler to achieve the coherent superposition of the two BPSK signals to obtain the QPSK signal.This facilitates the transmission of signals from short-distance to long-distance communication networks and the allocation of signal bandwidth resources,and adapts the choice of network nodes to signal format conversion according to different networks.At the same time,the scheme can be extended to the format conversion of high-order MQAM signals to MPSK signals.