STUDY OF FREQUENCY TRANSFER VIA OPTICAL FIBER IN THE MICROWAVE DOMAIN

摘要

Technical issues are investigated for a precise frequency transfer system using two-way signals by wavelength division multiplexing (WDM) in a single fiber. Bi-directional optical amplifiers are necessary to make the distance longer. Frequency stability is shown in the tandem optical amplifier link where the amplified spontaneous emission (ASE) noises are accumulated. Increasing transmission speed is effective for improving the system performance; however, chromatic dispersion of the fiber degrades the frequency stability significantly in an experiment with 10 GHz signal and 50-km fiber. The degradation can be improved by using 1550 nm zero-dispersion-shifted fiber (DSF) instead of SMF. Effects of polarization mode dispersion (PMD) and polarization scrambling are experimentally shown with a differential group delay (DGD) generator. It is also important to use stable oscillators for stability evaluation, since the time difference between the original and the received signal at the far end degrades the performance if the phase noise of the OSC source is not small enough.