Influence of radiation at wavelength near 1.5 µm on efficiency of inter-modal FWM in a few mode fiber in the region of 1 µm

We introduce an experimental and theoretical study of inter-modal four wave mixing (IMFWM) in a few mode optical fiber in the region of 1 µm, Influence of radiation with wavelengths near 1.5 µm on the efficiency of this process was shown. To study this effect we used pulsed Yb and Er fiber lasers emitting at 1 µm and 1.5 µm wavelength, respectively. The pulses from both sources were synchronized in time and were coupled into the same few mode optical fiber. We have observed IMFWM in the 1 µm region for different length of optical fiber and the efficiency of this nonlinear process significantly increased in presence of the 1.5 µm radiation for type of fiber we used. The transvers intensity distribution at the few mode fiber output was visualized for different IMFWM peaks. It helped to investigate the modal composition in the region of 1 µm, The mathematical model of propagation of light pulses through a few mode fiber with nonlinear interaction between 1 µm and 1.5 µm radiation was developed. The experimental results were in good agreement with the calculated phase matching curves for the IMFWM and FWM.