All-optical wavelength converter with recirculating configuration based on self-phase modulation in a highly nonlinear photonic crystal fiber

A novel scheme is proposed to achieve all-optical SPM-based wavelength conversion in a bismuth oxide-based highly nonlinear photonic crystal fiber. It consists of erbium-doped fiber amplifier, optical circulator, Fiber Fabry-Perot filters, photonic crystal fiber and fiber Bragg grating. Owing to SPM, a recirculating configuration is designed to induce the further spectral broadening and wavelength conversion is achieved with a tunable Fiber Fabry-Perot filter. The simulation results of bismuth oxide-based photonic crystal fiber indicate that the effective index of the fundamental mode increases monotonically with the increase in the hole pitch, or the decrease in the ratio of the hole diameter to the hole pitch. The mode effective area steadily increases with the hole pitch. The nonlinear coefficient, which is beneficial to shorten the fiber length and reduce the required optical power, is expected to be 1100W-1km-1 by using bismuth oxide-based glass with high nonlinear refractive index and reducing the effective core area with holey microstructure. The mode-field diameter of bismuth oxide-based is estimated to be 1.98μm and the predicted small effective core area is 3.3μm2. The propagation loss at 1550nm is about 0.8dB/m. The obtained results show that SPM-based PCF-WC has a potential of wide conversion bandwidth, high response time, simple configuration and low insertion loss etc.