Demonstration of all-optical RZ-to-NRZ format conversion based on self phase modulation in a dispersion flattened highly nonlinear photonic crystal fiber

We propose a novel all-optical format conversion scheme from the return-to-zero (RZ) to non-return-to-zero (NRZ) based on a single dispersion-flattened highly nonlinear photonic crystal fiber (DF-HNL-PCF) and an optical band-pass filter (OBPF). The polarity-preserved, 30 Gbit/s RZ-to-NRZ format conversion with Q factor and extinction ration (ER) of 6.57 and 16.06 dB is demonstrated by exploiting self-phase modulation (SPM) induced spectral broadening together with subsequent spectral tailoring in the DF-HNL-PCF. The experiments are carried out to investigate the wavelength tunability and the dynamic characteristics of the newly designed PCF-based format converter. Our results show that the designed format converter has a wide operating wavelength range of 24 nm and higher tolerance to input signal power fluctuation. This is very useful and attractive for engineering applications of optical-fiber-based RZ-to-NRZ format converter in future ultra-high speed photonic networks.