Polarization-independent Fiber-optic Microwave Modulator

Many types of modulators suitable for fiber-optic systems exhibit a strong dependence of the modulation on the input state of polarization (SOP). Several schemes have been devised to overcome the effects of polarization changes including feedback input polarization control,' source depolarization: and use of polarization maintaining fiber (PMF). Recently, we reported a passive scheme to address low-frequency modulators over conventional fiber links.3 The configuration, termed an orthoconjugating loop mirror (OCLM), uses a polarization beam splitter (PBS) with the fibers from the output ports connected in a loop that contains a 90° Faraday rotator. Here we expand the technique to include wideband dual-feed traveling-wave devices