The invention relates to the technical field of
optical fiber sensing, in particular to a
fiber bragg
grating low-temperature sensor and a preparation method and a monitoring method thereof, and the
fiber bragg
grating low-temperature sensor makes use of the characteristics that a polyether-
ether-
ketone material is large in
thermal expansion coefficient and has good adaptability in a frozen soil environment, so that the sensitivity enhancement effect of the packaged sensor is obvious; the device can well
resist frozen soil freezing and thawing,
water erosion and other influences, realizes long-term stable and high-precision
temperature measurement, and is simple in structure and easy to process; according to the preparation method, the extra
pressure stress acting on the
fiber bragg
grating in the cooling process after the thermosetting
adhesive is heated and cured is counteracted through enough tensile stress, the
chirp phenomenon caused by full-pasting packaging can be effectively avoided, good
thermal coupling between the substrate and the
fiber bragg grating is achieved, the use reliability is improved, and the service life is prolonged; the monitoring method adopts a specific mounting mode to realize good contact between the base and the mounting position, and the base can freely expand and retract under the action of temperature, so that the requirement of high longitudinal resolution of the
temperature gradient of the frozen earth stratum is met.