Self-heated fiber thermal lever sensor based on the temperature gradient inside a hermetic chamber

A thermal convection-based fiber lever sensor is proposed and experimentally demonstrated. Instead of the solid or liquid mass found in a conventional lever sensor, a Co²⁺doped microfiber is self-heated with a pump laser as the heat source, generating a symmetrical temperature profile inside a hermetic chamber due to thermal convection. The convection current generated by the temperature gradient remains in the opposite direction to gravity with different tilt angles, due to a natural convection effect acting as a “gas pendulum”. However, the locations of two micro-single mode fibers are asymmetric, corresponding to the central axis of the temperature gradient. Therefore, the tilt angle can be detected by interrogating the wavelength shift of the Michelson interferometer induced by the temperature difference. The experimental results show that a tilt-angle sensitivity of 95 pm/deg can be achieved. The proposed fiber-optic lever sensor possesses large dynamic range, low cost, and high sensitivity.