Weicheng Chen

Modulation instability of femtosecond pulses in dispersion-decreasing fibers

Abstract Modulation instability (MI) to generate femtosecond pulse in dispersion-decreasing fibers (DDF) is investigated. Higher-order dispersion effect and higher-order nonlinear effects are taken into account when continuous wave or quasi-continuous wave evolves into sub-picosecond or femtosecond pulses by MI in optical fibers. Our research results show that the gain spectrum of the DDF is much wider than that in conventional fibers. The third-order dispersion effect has no contribution to gain spectrum, self-steepening effect reduces the maximum value and gain bandwidth of gain spectrum, and Raman self-scattering effect widens the extent where MI occurs.

Enhanced pulse adaptive to PMD by modulating breath-depth

The enhancement of adaptive abilities of nonlinear optical pulses to polarization mode dispersion (PMD) is obtained by modulating breath-depth of two polarization states of the pulses. The breath-depth modulation is realized based on the interaction among self-phase modulation, cross phase modulation, group velocity dispersion and degenerate four-wave mixing, which results in making two polarization states of the pulses into a tighter state when nonlinear pulses propagate in optical fibers with high birefringence. Numerical results show that the transmission stabilities of modulated breath-depth optical pulses are improved in conventional fibers with random birefringence. The pulse broadening trend of the modulated breath-depth pulses induced by PMD is effectively suppressed by our proposed method. The symmetric output pulse shape is also reshaped in conventional fibers.

ENHANCED POLARIZATION SOLITON'S ROBUSTNESS TO POLARIZATION MODE DISPERSION IN FIBER SYSTEMS WITH FREQUENCY-DEPENDENT LOSS

We propose a new method to strengthen the nonlinear pulses robustness to polarization mode dispersion in the conventional lossy fiber systems. The method is based on the generation of the stable trapped state of polarization solitons in an initial optical fiber with high birefringence. It is proven that the obtained bound state of nonlinear pulses have stronger adaptive abilities to polarization mode dispersion than common solitons when they propagate in conventional fibers with random birefringence.

SUPPRESSION OF SOLITON TIMING JITTERS BY PERIODIC OPTICAL PHASE CONJUGATIONS AND OPTICAL FILTERS

We propose a new method for suppressing the timing jitters of soliton pulses by using periodic phase conjugations and optical spectral filters in a high bit-rate transmission system. It is proven that the tolerable transmission distance limited by timing jitters can be increased through modulating frequency shifts by optical phase conjugators and eliminating the interaction between dispersive waves and the central pulses by optical filters. Our results also show that the optical-phase-conjugated soliton with spectral filters is superior to the common soliton in suppressing polarization mode dispersion induced by random birefringence. The physical mechanisms of soliton timing jitters are analyzed.

Higher-order effects on self-similar parabolic pulse evolution in microstructured fiber amplifier

The evolution properties of the self-similar parabolic pulse(similariton) with higher-order effects in microstructured fiber amplifier with normal group-velocity dispersion are investigated in this paper. The numerical results show that the higher-order effects greatly distort similaritons waveform, frequency and the linearity of chirp. The drift of pulse center increases with distance. The influence of different higher-order effects on similariton is analyzed. High quality propagation of similariton can be attained by manipulating the geometrical parameters of the microstructured fiber amplifier. These results are significant in the further study of similariton propagation in high-power ultrashort fiber amplifier, laser and transmission system.