Mutual influence of intermodal and fundamental four-wave mixing of 1.0 µm and 1.5 µm nanosecond pulses in a dual-wavelength fiber laser.

We introduce the experimental and theoretical investigation of the mutual influence of two four-wave mixing (FWM) processes during the propagation of high-power nanosecond pulses at 1030 nm and 1562 nm wavelengths in the few-mode optical fiber. Both fundamental mode FWM (FM FWM) of laser pulses at these wavelengths, and intermodal FWM (IM FWM) of 1030 nm pulses, have common anti-Stokes components at 1003 nm wavelength. This leads to the mutual influence of FWM effects. As a result, the decrease of optical power of the fundamental mode is observed at both 1030 nm and 1562 nm wavelengths. The method for the suppression of such an adverse effect is proposed. It is based on the attenuation of the 1030 nm higher LP mode at the few-mode optical fiber input.