Increase in the output power of radiation with a wavelength of about 1650 nm using dual-polarised Raman amplification

Nonlinear distortions of radiation at the Raman amplifier output in the regimes with one and two orthogonal polarisations (single- and dual-polarised amplification) in an extended optical fibre are compared. At an output power of 3.5 W and a wavelength of 1650 nm the nonlinear distortions for dual-polarised amplification are smaller, due to which a narrower spectrum can be provided for output radiation. As a result, one can measure more exactly, for example, the methane concentration using a remote lidar system. A somewhat higher power of an undistorted signal (~4 W) without deteriorating the spectral properties of output radiation is obtained in the dual-polarised amplification regime at the aforementioned wavelength.