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We investigate the adiabatic compression of picosecond and subpicosecond soliton pulses from all-fiber, passively mode-locked, erbium-doped fiber soliton lasers operating at 1550 nm in dispersion-decreasing fibers (DDF's). High-quality soliton compression from 630 down to 115 fs in a 100-m DDF and from 3.5 down to 230 fs in a 1.6-km DDF is obtained. The effects of third-order dispersion and Raman self-scattering on the compression process are observed and discussed.

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Despite the great success in the development of the Bi-doped fibers technology and the creation of Bi-doped fiber lasers and optical amplifiers, some problems are not solved yet. The main problem is that the nature of bismuth NIR emitting centers is not clear. At present, a number of hypotheses are published, but none of them have been directly confirmed. The aim of this letter is to discuss briefly some of the existing hypotheses and to propose our approach concerning the nature of Bi-related NIR active centers. In previous publications we suggest that Bi-related NIR emitting centers are clusters, consisting of Bi ions and oxygen deficiency centers but not Bi ions themselves. In this letter we present the results of our experiments which confirm this structure of the Bi NIR active centers in germanosilicate fibers.

We report the generation of 114 Gbit/s trains of 250 fs fundamental solitons. The pulses are generated due to the conversion of an intense optical beat signal (generated from two DFB laser diodes and an erbium doped fiber amplifier combination) into a soliton train due to nonlinear propagation in a 1.6 km fiber of steadily decreasing dispersion. The train repetition rate corresponds to the beat frequency of the input signal and was readily tunable between 80 and 120 GHz. The results of a computer simulation of the system are found to be in good qualitative agreement with the experimental observations.

Permanent long-period gratings were written using arc discharges in two aluminosilicate fibers, one of which was doped with erbium. Reversible gratings were also mechanically induced in both fibers. The thermal behavior of the arc-induced gratings was investigated at up to 1100 degrees C. It was found that the shift of the resonant wavelengths exhibited a well-defined linear dependence on temperature up to 700 degrees C.

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