Practical sub-picosecond pulse generation at 1.55 μm by means of a pulse compressor featuring a highly-nonlinear dispersion-shifted fiber

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Abstract
Sub-picosecond optical pulse trains at a high repetition rate in the 1.55 /spl mu/m region are necessary for future ultra-high-speed optical fiber communication systems. For generation of such short pulses, the following two pulse compression scheme are usually employed. One is the adiabatic soliton compression using a dispersion-decreasing fiber (DDF) in the anomalous dispersion region. The other is the supercontinuum-based pulse compression method. In this method, the supercontinuum (SC) spectrum is first generated from initial pulses by the interplay of self-phase modulation (SPM) and normal group-velocity dispersion (GVD) of optical fibers. Such pulses are then compressed linearly by a proper amount of anomalous GVD, because they have the linear up-chirp across the entire pulse width. In these pulse compressors using optical fibers, the third-order dispersion (TOD) of fibers limits the achievable pulse width. Therefore, the dispersion-flattened DDF is strongly desired for the soliton compressor. Also, in the SC-based compression method, the fiber used for SC generation should be a dispersion-flattened fiber with a small normal GVD. We demonstrate a more practical SC-based pulse compressor featuring a highly-nonlinear dispersion-shifted fiber (HNL-DSP). Because of high nonlinearity of such fiber, we may use a relatively large normal GVD for SC generation, which, in turn, diminishes the harmful effect from TOD.