Frequency-domain intermodal interferometer for the bandwidth measurement of a multimode fiber

A new bandwidth measurement technique for a multimode optical fiber (MMF) using a frequency-domain intermodal interferometer is proposed. We have demonstrated that the relative modal delay (RMD) of a MMF can be obtained easily and accurately based on an optical frequency-domain reflectometry (OFDR) technique by using an intermodal interference signal among the excited modes of a MMF. As an example, a photonic crystal fiber with a few modes is prepared and its RMD is measured by using our proposed measurement technique. Measurement results are compared with those from a previously reported frequency-domain method. We have also measured the RMD of a commercial MMF as a practical application and compared our result with the one obtained from a well-known time-domain differential mode delay measurement technique.