Study On Ultra-short Pulse Source And High Power Nanosecond Pulse Propagation In Fiber

Ultra-short pulse source, which is one of the key techniques in high-speed optical communication system, has become the hotspot in the current research. And with the development of high-power fiber laser and amplifier, nonlinearity management techniques are of great importance now. The presented dissertation focuses on the generation of ultra-short pulse and transmission behavior of high-power optical pulse in fiber by theoretical analysis and experiments, and the main contents are as follows:1. Nonlinear polarization rotation passively mode-locked fiber laser1) Operation principle of a nonlinear polarization rotation passively mode-locked fiber laser is investigated theoretically by solving temporal mode-locking equation.2) Based on polarization additive pulse mode-locking technique, Stable, self-starting mode-locked pulse train at 25MHz repetition rate with central wavelength of 1558.4nm, pulse-width of 520.5fs and spectral width of 25.9nm is obtained. The influence of coupling ratio, coupler position and total dispersion on mode-locked pulse is experimentally investigated.2. Optical pulse compression techniques1) A novel adiabatic soliton technique based on loss management fiber transmission line is proposed. When the fiber length is set, the best compressing performance can be achieved by controlling the pump power carefully.2) A new optical pulse compression method on the basis of quasi-nonlinear increasing fiber consisting of single-mode fiber (SMF), dispersion-shifted fiber (DSF) and high nonlinear fiber (HNLF) is presented. This scheme is easy realized in practice because the fiber used in the simulation is commercial. Moreover, it can be controlled flexibly by simply changing the gain of EDFA.3. Propagation characteristics of high power, nanosecond pulse in fiber1) The influence of nonlinear effects including self phase modulation (SPM), stimulated Raman scattering (SRS) and stimulated Brillouin scattering (SBS) on high-power (peak power ~1000W) pulse with a pulse-width of ~1ns is investigated numerically. The conclusions could be used to guide experiments.2) The supression of nonlinear effects by use of large mode area (LMF) fiber is investigated, which is useful to the further research.