Compression Of Laser Diode Pulses Based On Dispersion-Decreasing Fiber And Nonlinear Optical Loop Mirrors

Ultrashort optical pulses is becoming more and more important in optical information processing, various ultrafast phenomena and dynamic processes detecting as well as high-bit-rate optical communication systems. Pulses compression is.a main method to obtain ultrashort optical pulses, so the work of this paper is focused on picosecond optical pulses compression. The major research aspects are as follows.Firstly, low jitter optical pulses are generated from a gain-switched Fabry-Perot laser diode. Full width of half maximum (FWHM) of the red-chirped pulse is 47 ps.Secondly, we select dispersion compensation fiber (DCF) to remove the negative chirp of gain-switched pulses. Three compression conditions in which DCF has different dispersion values are simulated and compared with each other. The results show that DCF with three different dispersion values can realize the same compression, that is the same chirp removal effect and pulse width, but the larger the fiber dispersion value is, the shorter the fiber is needed to achieve this. For compressing the pulses generated from gain-switched laser diode, the fiber length and compression factor are worked out to get optimal compression effects.Then for the compressed pulses, a nonlinear optical loop mirror constructed from dispersion decreasing fiber (DDF) is adopted to get an even narrower pulse width and better pulsequality. The simulation results show that for linear, Gaussian and hyperbolic dispersion profiles DDF, the loop mirror compression result of the last one is worse than the other two, the longest fiber is needed for hyperbolic profile to achieve its best compression effect and the compressed pulse pedestal energy is the largest. The linear and Gaussian profile DDF-loop mirrors give nearly the same simulation results. From this, one can conclude that the varying slope of DDF profile affects the pulse compression quality greatly. The slower the dispersion profile varies, the better the compressed pulse quality is. So linear, Gaussian or others profiles with even less dispersion varying ratio are fit for constructing dispersion decreasing fiber-nonlinear optical loop mirror to compress picosecond optical pulses.Finally, based on the simulation results above, a pulses compression scheme is brought out to compress the experimental 47ps pulses to sub-picosecond pulses with small pulse pedestal energy.