Selective transverse mode operation of a fiber laser based on few-mode FBG for rotation sensing

A fiber laser with selective transverse mode operation based on few-mode FBG was designed, and rotation sensing via hybrid mode operation was successfully demonstrated. The mode selection was achieved by a few-mode FBG inscribed in homemade elliptical multilayer-core fiber (EMCF). The particular designed EMCF only supports LP₀₁ and LP₁₁ ^even mode groups, and the resonance of a few-mode FBG could be adjusted through mode excitation. Therefore, selective transverse mode operation was realized by switching the resonance wavelengths corresponding to the self-coupling mode or cross-coupling mode. Besides, rotation sensing was achieved in the hybrid mode operation due to the asymmetric multilayer-core design. A sensitivity of 0.074 mW/° was preliminarily demonstrated. The measured angle of the rotation sensing system is within ± 2° in the temperature range of 10-90 °C, showing that this system was inherently insensitive to temperature, eliminating the requirement for temperature compensation.