By combining a special dispersion map that has nearly constant path-average dispersion, a hybrid amplification scheme involving backward-pumped Raman gain, and sliding-frequency guiding filters, we have demonstrated massive wavelength-division multiplexing at 10 Gbits/s per channel, error free (bit-error rate, =1x10(-9) for all channels), without the use of forward error correction, over greater than 9000 km, using dispersion-managed solitons. The number of channels (27) was limited only by a temporary lack of amplifier power and gain flatness. Terabit capacities are to be expected in the near future.
We describe a method, based on the phase mismatch of four-wave mixing, for direct and accurate measurement of the dispersion map, D(lambda, z), of an optical fiber. The method, which requires no wavelength scanning and access to only one end of the fiber, has produced the data for an entire 34-km span, including hundreds of repetitions for signal averaging, in less than 0.25 s. Spatial resolution and accuracy in that first experimental test were ~1 km and deltaD ~ +/-0.03 ps/(nm km), respectively.
Transmission of 50-psec solitons in a 75-km recirculating loop of dispersion-shifted fiber (D = 1.38 psec/nm/km at lambda(s)), using low-gain erbium amplifiers spaced 25 km apart, displays jitter in pulse arrival times consistent with low error rates for transmission over 9000 km and for bit rates ?4 Gbits/sec. Furthermore, a study of soliton pair propagation in the same loop shows no significant interaction over 9000 km for pair spacings >/=5tau.
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