Shum Ping

Nonlinear switching and pulse propagation in phase-shifted cubic quintic grating

We investigate numerically the nonlinear switching characteristics and pulse propagation behavior in the phase-shifted cubic quintic grating (CQG). The continuous-wave nonlinear switching curve shows an interesting feature whereby two switching thresholds and consequently double bistability hysteresis are formed in a certain detuning window. We show the unique bistability (U-bistability) region close to the upper-switching threshold in each of the hysteresis, where the high state in U-bistability can be reached when input is coming from low to high with fast rise time. For medium peak intensity Gaussian pulse propagation in phase-shifted CQG, the full-width at half-maximum of the output pulse varies in upward parabolic manner as the peak intensity increases, whereas for high peak intensity Gaussian pulse propagation, the output pulse will experience distortion from the Gaussian shape because of the compression in its leading edge and broadening in its trailing edge concurrently.

Matrix-Based Polarization Analysis and Application of Semiconductor Optical Amplifiers

Employing the Mueller matrix method with polar decomposition, we analyse the polarization rotation (PR) effects in semiconductor optical amplifiers (SOAs) and demonstrate that the PR angle is linear to the birefringence dependent gain while the average PR coefficient is about 0.625 for the employed SOA. It is further evident that the current and optical intensity dependent PRs rotate reversely around the same axis. Thus we propose an optical-electric synchronous control scheme to obtain orthogonal polarization states with power-equalization, and implement it by a polarization-sensitive SOA. The polarization duration time is about 10 ns which is applicable to high-speed polarization state generation.

All-optical transistor operation based on the bistability principle in nonlinear distributed feedback GaInAsP-InP waveguide: a transient perspective

We demonstrated all-optical transistor operation based on the bistability principle in nonlinear distributed feedback GaInAsP-InP waveguide. By increasing the pump power above a certain limit, the probe transmission that operates in the bistable regime can turn from switching to transistor mode. The unstable state is shown to play a crucial role in distinguishing the probe transmission artifacts between switching and transistor mode.

Room-temperature multiwavelength erbium-doped fiber ring laser employing equivalent low-frequency shift feedback

An effective method to implement room temperature operation of multiwavlength erbium-doped fiber ring laser (MW-EDFL) employing equivalent low frequency shift feedback (ELFSF) is presented. Simultaneous multiwavelength lasing with 0.5nm wavelength spacing is experimentally demonstrated by applying a sawtooth signal of the order of 10kHz to a phase modulator inserted in the ring cavity to prevent single-wavelength oscillation. A LiNbO3 multifunction chip of fiber gyro has been used as the phase modulator, the output coupler, and the polarizer of Lyot periodic filter. The MW-EDFL output is linearly polarization light that meets the requirement of external modulation for WDM applications.

Bound soliton pulses with FWHM duration of 326 fs and separation of 938 fs in a passively mode locked fiber laser

Summary form only given. A passively mode locked fiber soliton laser was successfully setup. After adjusting the polarization controllers (PC) carefully, bound soliton pulses with FWHM width of 326 fs and fixed separation of 938 fs were achieved with existence of a strong CW component at the center of the soliton spectrum. Hysteresis of bound soliton operation was also observed. Only under lower pump power, can the number of bound soliton pairs be controlled, and they are destroyed one pair by one pair when pump power is decreased. But multi-bound soliton operation is formed suddenly while increasing pump power, because energy competition exists with CW. We found that the soliton pulse width increased with the transmission fiber length linearly, and the separation between bound solitons increased linearly after 5 m.

Analysis of pulse broadening induced by the second-order PMD

We propose a new conception of depolarization vector to describe the effect of depolarization induced by the second-order polarization mode dispersion (PMD). Deriving the formula of pulse broadening induced by the second-order PMD, we find that the polarization-dependent chromatic dispersion (PCD) always enhances the pulse broadening. However the depolarization vector decreases the pulse broadening. The pulse broadening is correlated with the bit-rate of a transmission system. By adjusting the directions of the Stokes vector of initial state of polarization, initial first-order polarization dispersion vector and depolarization vector to be parallel to each other, one can obtain an optimum dispersion compensation. But when the PCD is not equal to zero, the optimum dispersion cannot achieve a complete compensation and the minimum pulse broadening is equal to σ = (21/2/4)(DCF/T0).