All-optical Wavelength Conversion Of OFDM Signal Based On Polarization Diversity Structure

In order to meet the ever-increasing business and bandwidth requirements,building an All-Optical Network?AON?based on Wavelength Division Multiplexing?WDM?has become an inevitable goal for the development of the optical communications field.The all-optical wavelength converter is a key device in the AON.It can avoid wavelength competition and network jam,and improve the intelligence and survivability of WDM networks.Orthogonal Frequency Division Multiplexing?OFDM?signal has a strong ability to resist chromatic dispersion?CD?and polarization mode dispersion?PMD?,and the modulation and demodulation of OFDM signal can be completed easily depending powerful Digital Signal Processing?DSP?technology,OFDM signal has been widely used in the field of optical fiber communication.Combining OFDM technology with AOWC technology is of great significance for achieving high-speed and large-capacity information exchange.Based on such a background,this article conducts theoretical and experimental research on AOWC of OFDM signal.The main research contents are as follows:Firstly,a new scheme for AOWC of OFDM signal lightwave based on the SOA-FWM effect of polarization-diversity structure is studied by theory and simulation.Theoretical analysis shows that the wavelength converter under this scheme is polarization insensitive,and its wavelength tunability is larger than that of the parallel pump scheme and the orthogonal pump scheme.Then a simulation platform was built based on the theoretical model,and the main factors affecting the scheme are studied,including input optical power,ECL line width,and SOA injection current.Simulation results show that the power variation of the converted lightwave is less than 0.5 d B with polarization angle of the signal lightwave changed from-90°to 90°.Under the same simulation conditions,the conversion range of the polarization diversity scheme,the parallel pump scheme and the orthogonal pump scheme are 0.14 THz,0.05 THz,0.08 THz,respectively,which proves that the wavelength tunability of the polarization-diversity scheme is the largest.Secondly,an experimental platform is built on the basis of numerical simulation and experimentally study the performance of the wavelength converter under this scheme,including polarization sensitivity,wavelength tunablilty and system performance under QPSK/16-QAM modulation format.Experimental results show that the scheme can achieve a conversion range of 8 nm and is polarization insensitive.At BER=2×10^-2,the 16-QAM signal increases the power penalty of 8 d B compared to the QPSK signal after wavelength conversion.Thirdly,a new scheme for AOWC of OFDM signal lightwave based on the HNLF-FWM effect of polarization-diversity structure is studied by theory and simulation.Theoretical analysis shows that the wavelength converter under this scheme is polarization insensitive.Then the performance of the wavelength converter is studied by simulation,including polarization sensitivity and power cost under different signal modulation formats.Simulation results show that when the polarization angle of the signal lightwave changes from-90°to 90°,the variation of converted signal's EVM is less than 1.5 dB.When system BER equals 1×10-3,the power cost of 16-QAM signal and 64-QAM signal before and after wavelength conversion are 1 d B and 1.5 d B,respectively.