Four-bit all-optical quantization based on Raman self-frequency shift and spectral compression

An all-optical quantization based on Raman self-frequency shift (RSFS) in a photonic crystal fiber (PCF) and spectral compression in a dispersion-increasing fiber (DIF) is analyzed, and the evolution of femtosecond pulse in fibers is described by numerically solving the generalized nonlinear Schr?dinge equation (GNLSE). Gaussian pulse with the width of 300 fs and center wavelength of 1550 nm is injected into 15 m-long PCF and 100 m-long DIF. The simulation results show that the center wavelength increases linearly with the input peak power which changes from 110 W to 165 W. The RSFS of 65.3 nm and maximal spectral compression ratio of 3.38 can be obtained. The resolution of the quantization is improved from 2.4 bits to 4 bits by using the spectral compression in the DIF.