Sensitivity enhanced fiber optic temperature sensor based on optical carrier microwave photonic interferometry with harmonic Vernier effect

•The harmonic Vernier effect is applied to the optical carrier microwave interferometry (OCMI) for the first time.•The equipment requirement could be reduced by tracking the intersection of inner envelopes.•In the range of adjacent inner envelope intersections, the temperature measurement range reached 317 degrees.•Higher fabrication tolerance is provided to meet the machining accuracy the Vernier effect sensing need.