Measuring the complex frequency response of multimode optical fibers

An improved frequency-sweeping method for measuring the complex frequency response (transfer function) H(omega) of multimode optical fibers is proposed. Measurement of the phase angle of H(omega) is difficult and has been performed infrequently and with poor accuracy. In the method proposed, this difficulty is overcome using a single-mode fiber as a reference for the phase angle of H(omega). The complex frequency responses of two multimode fibers measured with this new technique are shown and compared with pulse method results.