A highly nonlinear photonic crystal fiber (PCF) is proposed to construct a nonlinear optical loop mirror (NOLM) for pulse compression and shaping. The proposed highly nonlinear PCF is a large air-filling fraction holey fiber with a small fiber core. The characteristics of the fiber have been studied. The NOLM made up of this PCF and an asymmetrical coupler for pulse compression and pedestal suppression is theoretically investigated. The results show that when compared with a soliton-effect compression in which only a piece of PCF is used, a NOLM based on a highly nonlinear PCF significantly suppresses pulse pedestals with a relatively short loop length. For a given input pulse, there exists an optimal loop length at which the high quality compressed pulse can be obtained. The proposed scheme can be used to compress long pulses by use of appropriate fiber lengths and works well for a broad range of input soliton orders.
In this paper, the experiment on all-optical switching based on microstructured optical fiber (MOF) is reported. In experiment, a 25-meter-long MOF(γ=36W-1km-1@1550nm) is used as nonlinear medium of nonlinear optical loop mirror and the input signal is generated by a 10GHz tunable picosecond laser source (u2t TMLL1550), with a full-width at half-maximum (FWHM) pulse width of 2 ps centered at 1550 nm. With the increase of input power, a π nonlinear phase shift is obtained by 40/60 coupler in experiment, but the same thing not be found by 48/52 coupler. Strong confinement of electromagnetic radiation in the fiber core allow that microstructured optical fiber can have a much higher nonlinearity per unit length than conventional fibers, and consequently devices based on such fibers can be much shorter in length than their conventional counterparts. Additionally, the switching can also be used as reshaping devices.