Optical quantization based on soliton self-frequency shift and a flexible spectrum compression scheme utilizing...

We propose and experimentally demonstrate a novel optical spectrum compression scheme utilizing time-dependent filtering effect, which can be used to improve the resolution of the optical quantization based on soliton self-frequency shift (SSFS). The spectrum compression is realized through power-dependent filtering utilizing polarizers and nonlinear polarization rotation effect in a spool of high-nonlinear fiber (HNLF) after mapping the soliton spectrum to the time domain in a section of dispersive fiber. Theoretical analysis and numerical simulation indicate that, compared with the conventional spectrum compression scheme based on chirp compensation, the proposed scheme does not have a restrictive length match requirement of the dispersive fiber and the HNLF. In addition, the output spectral width variation is small for various pulse peak power, which is favorable for the subsequent optical coding. In the experiment, the spectra after SSFS are compressed to an average spectral width of 1.65 nm, which is 45% of that using comb-like fibers. The quantization resolution using the proposed scheme is 5.95 bits for a maximum wavelength shift of 100 nm, which is 1.13 bits higher than that using comb-like fibers.