A Novel Scheme Of Optical Meyer Wavelet Filter Based On Time Lenses In High-bit Rate Optical Fiber Communication System

The optical fiber communication system’s evolution is to be with higher bit rate, more channel capacity. How to upgrade the existing commercial fiber links and save the cost in practice is becoming the focus topic in optical fiber communication systems. Optical Meyer wavelet filter based on time lenses proposed in this work can achieve better results than other optical filters so it can improve the channel capability and guarantee the quality of higher bit rate optical fiber communication. And it was feasible and effective for optimize optical communication system. The main work was shown as below:Firstly analyzing basic structure of2-f time lenses sub-system showed its characteristics of Fourier transform for optical signal in all-optical domain and the relation between the dispersion of the dispersive component and the quadratic phase of the phase modulator that is a time lens. According to the relation between input and output optical signal of2-f sub-system, factors that would affect output signal and the methods for avoid these factors were discussed.In this paper we proposed a novel scheme of optical Meyer filter based on time lenses. Then the detailed mathematical derivation was stated and we got important functions about Meyer wavelet decomposition and reconstruction process. According to these functions, an optical Meyer wavelet filter was designed and realized by use of time lenses and Mach-Zehnder modulators (MZMs). It can realize the wavelet decomposition of optical signals in all-optical domain and directly de-noise the distorted optical signal in high bit rate optical communication systems without photo-electric conversion. Numerical simulations were performed in different types of fiber links for intensity modulated (IM) signal when optical Meyer wavelet filter was applied at the end of40Gbit/s multi-span dispersive and nonlinear fiber transmission systems. By comparing Normalized Squared Deviations (NSDs) and Bit Error Rates (BERs) of the signals without de-noising, after optical band-pass filter and optical Meyer wavelet filter, we demonstrated that the nonlinear noise can be removed more effectively by optical Meyer wavelet filter. The BER curves in dispersion compensation links with optical Meyer wavelet filter at1level with290G bandwidth shows the best immunity to nonlinear noise, which can reduce BER about11dB with6mW input power and900km transmission distance, and can extend transmission distance to840km longer than715km that de-noising with optical band-pass filter at BER=10-9when compared with the traditional optical band-pass filter de-noising. And it is convenient to be applied in the existing fiber systems without changing the arrangement of fiber links in use when considering the cost for upgrading fiber communication systems in commercial application.