Showing papers by "Mohammed N. Islam published in 1986"

Soliton propagation in long fibers with periodically compensated loss

Abstract: With computer simulation, we study soliton propagation in an all-optical, long-distance communications system where fiber loss is periodically compensated by Raman gain We find that distortion of the transmitted pulses from true solitons shows a peak near z_{0} = L/8 where L and z 0 are the amplification and soliton periods, respectively We also describe optimal system design based on the exceptional pulse stability and low soliton powers obtained in the region z_{0} \gg L/8 Typical amplification periods are in the range 30-50 km, pump powers are less than 100 mW, and for bit rates in the 10 GHz range, time average signal powers are at most a few milliwatts The single-channel rate-length product for error rate less than 10-9is \sim29 000 GHz Km Finally, we show that in the gain-compensated system with wavelength multiplexing, soliton-soliton collisions produce random modulation of individual pulse velocities Nevertheless, multiplexing can yield rate-length products greater than 300 000 GHz km

Picosecond study of near-band-gap nonlinearities in GaInAsP

Abstract: From picosecond pump‐probe and forward degenerate four‐wave mixing (DFWM) experiments, we obtain the near‐band‐gap nonlinear absorption and refraction properties of GaInAsP for λ∼1.5 μm. Using a mode‐locked color center laser, the nonlinear signals are studied in room‐temperature samples as a function of time and wavelength for different pump energies and for materials with different band‐gap energies. Nonlinear absorption cross sections σeh as large as −5.7×10−15 cm2 are obtained from the pump‐probe results, while effective nonlinear cross sections σeff as large as 7.8×10−16 cm2 (corresponding to a steady state ‖χ(3)‖∼3.8×10−3 esu for a 20‐ns relaxation time) are measured in the DFWM experiments. The spectral behavior of the data shows that above the band gap, the nonlinearity is due both to band filling and screening of excitonic effects. However, the effectiveness of the screening diminishes within one or two plasma frequencies of the band edge.

Fiber Raman amplification soliton laser

Abstract: By synchronously pumping a loop of fiber with ≈10-ps pulses from a mode-locked color center laser, we demonstrated the first Fiber Raman Amplification Soliton Laser (FRASL). The FRASL output pulses are determined by pulse compression and soliton pulse shaping in the fiber and have to date been as short as 240 fs. The lasing wavelength can be time dispersion tuned.1 The single-cavity FRASL is a much simpler configuration than the color center soliton laser,2 which consists of two coupled cavities and requires feedback stabilization to overcome interferometric instabilities.