A proposal for a temperature and strain sensor, based on OAM interference in few-mode fibers

The orbital angular momentum (OAM) carried by vortex beams provides new possibilities for optical communication multiplexing. OAM modes can also carry information due to their helicalphase wave fronts, providing a new mechanism for optical fiber sensing. In this paper, a novel image detection scheme based on OAM intermodal interference in few-mode fibers is proposed. Temperature and strain are measured simultaneously based on components with different azimuthal distributions in the interference pattern. The sensing mechanism and demodulation principle of the proposed sensor are studied, and the linear response range and anti-interference capability are analyzed. Simulation results show that the variations in temperature and strain can be simultaneously demodulated by using a single image obtained at the output of the sensing fiber at a single working wavelength. External optical noise and the internal modal intensity fluctuations, have little effect on the temperature and strain sensitivities of the proposed sensor. The intermodal sensors based on OAM modes have a larger linear response range and better antiinterference capabilities than intermodal sensors based on linear polarization modes.