Measurement of beat length in short low-birefringence fibers using the fiber optical loop mirror

Abstract In this paper we provide a detailed analysis and investigation of a novel experimental method to measure the birefringence in short low-birefringence fibers. This method is based on the fiber’s twist in a fiber optical loop mirror. It allows simple birefringence measurement in fibers with beat length within the range of 0.4–100 m. The shortest fiber we were able to measure was 0.034 of beat length. Statistical error of measurements was less than 3%. To demonstrate the measurement technique we present experimental results for three optical fibers whose beat lengths were in the range from 1 to 19 m.