THz-Range Optical Frequency Shifter for Dual Polarization WDM Signals Using Frequency Conversion in Fiber
We propose an optical frequency shifter for dual-polarization signals using frequency conversion in fiber. The proposed optical frequency shifter is achieved by transmitting input signal combined with two orthogonally polarized continuous wave pump lights through a nonlinear fiber and a polarizer. In the scheme, a polarization switched and frequency shifted copy of an original signal is generated in the nonlinear fiber and the subsequent polarizer removes the original signal in a wavelength independent fashion. It allows a fractional bandwidth shift, in which the shifted signal is overlapped with the original signal. We achieve THz range frequency shift with original signal suppression without an optical filter by using a polarization diversity loop. A polarization beam splitter is used as a splitter and a combiner of the loop as well as for original signal rejection. A contention resolution of two dual-polarization 400-Gb/s superchannels is demonstrated by applying the optical frequency shifter with acceptable in-band crosstalk. For any-to-any optical frequency shift, wavelength arrangement for pumps and required zero dispersion and dispersion slope of nonlinear fibers are numerically simulated.