The frequency chirps of the first-Stokes Raman (1.12-μm) and fundamental (1.06-μm) picosecond (~100-psec) pulses propagated through various lengths of single-mode optical fiber have been measured. The fiber lengths were varied from a regime in which walk-off was significant to a regime where it could be neglected. Besides being of positive sign and substantially greater than that of the fundamental, the chirp of the Raman radiation was found to be highly nonlinear, in good qualitative agreement with theoretical predictions.

Reshaping of ultrashort optical pulses at 1.53 μm by using an integrated acousto-optic tunable filter is reported. Control of the optical pulse shape is accomplished by adjusting the different radio-frequency electrical signals driving the acousto-optic filter. This is to our knowledge the first demonstration of ultrashort pulse shaping using an integrated-optic device and establishes a new application area for integrated wavelength-division-multiplexed devices, namely, for manipulation of coherent, ultrafast time-domain signals.

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Unrepeatered transmission is demonstrated over 501 km at 2.488 Gbit/s. Forward error correction enables a transmission distance of 529 km. A new SBS suppression technique, dispersion compensating fibre, and post- and pre-amplifiers remotely pumped by high power diode-pumped Raman lasers are employed.

The authors observe little or no accumulation of optical-power variations among wavelength-multiplexed signals as they traverse successive stages of a cooled, inhomogeneously broadened, erbium-doped fiber-amplifier cascade. The cascade instead exhibits separate automatic power regulation of each channel, decoupled from other channels, without the use of servo loops.