MEASUREMENT OF THE BEAT LENGTH IN HIGH-BIREFRINGENT OPTICAL-FIBER BY WAY OF MAGNETOOPTIC MODULATION

One of the most important parameters about high-birefringent optical f iber is the beat length. Because of its shortness and periodicity, the measurement of the beat length is very critical. Here, a highly accur ate measurement method that relies on magnetooptic modulation techniqu es is proposed, and the theoretical analysis and discussion about the measurement theories and the instrument construction are given in deta il. Finally, the construction of the beat length measurement instrumen t based on this novel method is described and several kinds of high-bi refringent optical fiber samples are measured. The beat-length resolut ion of this instrument is better than 0.01 mm, and the final measuring results are not influenced by the external interference on the fiber or the status of the placement of the optical fiber.