Weakly-coupled multicore optical fiber taper-based high-temperature sensor

•The inter-core coupling strength of weakly-coupled multicore fiber can be strengthened by tapering method.•The transmission spectra of the proposed sensor vary with environmental temperature due to thermo-optic effects and thermal expansion effects of multicore fiber.•The annealing techniques should be adopted to eliminate the effect of residual stress in the sensor and improve the high-temperature sustainability of the sensor. A novel high temperature sensor based on weakly-coupled multicore fiber (MCF) is proposed and experimentally demonstrated. The sensor consists of a taper of weakly-coupled MCF sandwiched between two standard single-mode fibers (SMF). The temperature sensing mechanism is investigated theoretically and experimentally. In order to eliminate the effect of residual stress in the sensor and improve the high-temperature sustainability of the sensor, the annealing techniques for the proposed sensor is also investigated. The sensor annealed via the proposed techniques was demonstrated experimentally to be able to measuring temperatures up to 1000 °C with sensitivity of ∼36.8 pm/°C.