S.V. Chernikov

Direct continuous-wave measurement of n2 in various types of telecommunication fiber at 1.55 μm

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.

Supercontinuum self-Q-switched ytterbium fiber laser

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.

Measurement of normalization factor of n(2) for random polarization in optical fibers.

The 8/9 normalization coefficient for the nonlinear refractive index in nonpolarization-maintaining optical fibers is confirmed directly by measurement of the ratio of the self- and cross-phase modulation coefficients for two orthogonal polarizations. The nonlinear phase shift is accurately measured with a dual-frequency beat signal as a pump source.

6-W Average power green light generation using seeded high power ytterbium fibre amplifier and periodically poled KTP

Up to 6 W average power, green laser source is demonstrated using a combination of laser-diode-seeded ytterbium fibre amplifier and quasi phase-matched second harmonic generation in periodically poled KTP. The source is used as a pump for a femtosecond Ti:Sapphire laser.

Temperature-dependent gain and noise in fiber Raman amplifiers

An experimental investigation of the temperature dependence of the gain and noise performance of a silica-fiber Raman amplifier is described. A decrease in the Raman scattering cross section in a fiber amplifier cooled from a temperature of 300 K to 77 K was measured and found to be in agreement with theoretical values. No difference between the Raman gain coefficients at these two temperatures was observed.

Broadband Raman amplifiers in the spectral range of 1480-1620 nm

Raman amplifiers using germano-silica fibers are demonstrated with a continuous operation bandwidth from 20 nm to more than 100 nm, 20-40 dB net gain and 4.5-7 dB noise figure. Single-, dual-, and triple-wavelength pumping are implemented in the configuration incorporating circulators for pump/signal multiplexing.

Low-noise high gain dispersion compensating broadband Raman amplifier

Raman gain module compensating for both loss and dispersion of a 40 km standard telecommunication fiber span over the 1510-1565 nm band is reported. The optimized configuration ensures a low signal-spontaneous noise figure and negligible double Rayleigh scattering noise. The high gain margin of the amplifier makes it applicable for compensation of an 80 km span.

Dispersion measurement in optical fibres over the entire spectral range from 1.1 μm to 1.7 μm

Abstract Using a super-continuum fibre laser we have measured the dispersion of optical fibre over the 1.1–1.7μm spectral window in silica fibre.

Efficient cascaded Raman generation and signal amplification at 1.3 μm in GeO2-doped single-mode fibre

We demonstrate a high-gain, cascaded fibre Raman amplifier, operating at 1.3 pm. Raman generation and amplification are achieved in a ring resonator constructed solely from fused fibre WDM couplers with low-loss GeOz-doped single mode fibre used as the active medium. The amplifier is pumped by a Nd:YAG laser at 1.064 p.m. In our resonant cascaded geometry, this generates the third Stokes line at 1.24 pm, which acts as a pump for Raman amplification of signals around 1.3 km. A gain of 28 dB is demonstrated with output signal powers of up to 20 dBm for 3.4 W of pump power. Our experiments also indicate the important role of filters to suppress feedback in the resonator, permitting high Raman gain and good signal quality. 0 1997 Elsevier Science B.V.

Fibre Raman amplifiers for broadband operation at 1.3 μm

A high-power fibre laser operating at 1.24 μm was used to provide broad band Raman gain around 1.3 μm in compact, efficient, silica fibre-amplifier configurations. The gain and noise performances of these broad band amplifiers are described, as well as the mechanism for further increasing and flattening the operational bandwidth.