A method for measuring the nonlinear refractive index of optical fibers with an error of less than 5% is demonstrated. The technique is based on measuring the nonlinear phase shift experienced by a dual-frequency beat signal, permitting a simple, highly sensitive, accurate, repeatable, and easily automated measurement procedure and sampling. Measurements of the nonlinear coefficient in standard telecommunication, dispersion-shifted, and a number of dispersion-compensated fibers are presented.

A more exact model is suggested for the description of nonlinear light propagation in fibers. In addition to the previously discussed self-phase modulation, parametric, dispersion, self-steepening, and Raman self-scattering effects, this model also takes into account the Stokes losses associated with the material excitation, the dependence of nonlinear effects on the light frequency, and the frequency dependence of the fiber mode area. The self-steepening effect is taken into account more correctly in comparison with previous models. The effects influence considerably the femtosecond soliton propagation. The model is generalized for the case of various fiber dispersion properties along the fiber length. The possibility of obtaining high-quality pulses of less than 15-fsec duration by compression of fundamental solitons with approximately 100-fsec duration in fibers with slowly decreasing dispersion is shown.

We have discovered a new mechanism for passive Q switching of fiber lasers. 10-kW peak power pulses with ~2-ns pulse widths are reported from a diode-pumped ytterbium-doped fiber laser. The laser generates a high-brightness Raman-dominated supercontinuum spectrum covering the complete window of transparency of silica fiber in the infrared from 1.06 to 2.3 mum.

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.

By adiabatic amplification of a periodically modulated cw signal in an optical fiber, a train of approximately independent solitons can be generated at a high repetition rate (up to the terahertz range). These pulse trains can be produced with fibers having slowly varying dispersion as well.