A method of modifying a uÌ ber optic fused biconical tapered coupler to produce a relatively temperature insensitive Michelson interferometer is presented. The modification was accomplished by cleaving the coupler after the minimum taper region and polishing, perpendicular to the endface, to a point just short of the interaction region. This allows one of the two fiber cores, which are within micrometers of each other with their claddings fused together, to be coated at its endface with a reflecting material. This reflecting core serves as the reference arm, while the other core serves as the sensing arm. Variations in the method of fabrication of the sensor are described. Because of the close proximity and short length of the reference and sensing arms, the interferometer is temperature insensitive. The miniaturized Michelson interferometer is characterized and its limitations are discussed. A surface acoustic wave detection scheme is successfully demonstrated. Results of a magnetic field sensor using the miniaturized Michelson interferometer and a magnetostrictive material are presented. / Master of Science