The reflection and transmission characteristics of a high-birefringence fiber loop mirror (HiBi-FLM),which is composed of a standard fiber coupler and one-section or multisection high-birefringence fibers(HBFs), are analyzed and discussed in detail. Theoretical reflectivity and transmissivity expressions forHiBi-FLMs with one-, two-, and three-section HBFs were obtained. The procedure for calculating reflectivityand transmissivity for HiBi-FLMs with n-section HBFs is given. Experimental results have verifiedthe theoretical model. The basic characteristics of the one-section HiBi-FLM when strain and hightemperature are applied to HBFs were analyzed and investigated theoretically and experimentally. Theexperimental results are in good agreement with the theoretical analysis. Furthermore, a strain–temperature sensor that makes use of those characteristics, which is new for applications of HiBi-FLMs,has been proposed and demonstrated.