A wavelength-encoded interferometric high-temperature sensor based on an all-solid photonic bandgap fiber (AS-PBF) is reported. It consists of a small piece of AS-PBF spliced core offset with standard single-mode fibers. Two core modes and are conveniently utilized as optical arms to form Mach– Zehnder-type interference at both the first and the second photonic bandgaps, and the maximum extinction ratio exceeds . Experimental and theoretical investigation of its response to temperature confirms that high temperatures up to can be effectively sensed using such an AS-PBF interferometer, and benefiting from a large effective thermo-optic coefficient of fiber structure, the sensitivity can be significantly enhanced ( at ).
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