Mode control on all-fiberized Raman fiber amplifier based on acoustically-induced fiber grating

Agile mode switching between LP₀₁ mode and LP₁₁ mode and power amplification in specific mode can be achieved at the same time by inserting an acoustically-induced fiber grating into a Raman fiber amplifier. The maximum signal light output power of the LP₀₁ mode and LP₁₁ mode is 8.51W and 7.98 W with the characteristic frequency of 769 kHz and 763 kHz, respectively. Moreover, the ratio of the two modes can be adjusted by modulating the frequency loaded on the acoustically-induced fiber grating. This work could provide an example of realizing a mode-switchable Raman fiber amplifier for practical application.