Operating Characteristics of Polarization-Independent Active Birefringent Fiber Loop Filter Using Two Traveling-Wave-Type Ultrafast Phase Modulators

摘要

Polarization-independent active birefringent optical fiber loop filters using two traveling-wave-type phase modulators are studied theoretically and experimentally. Theoretical analysis based on the Jones Matrix method reveals that polarization-independent operation requires a bidirectional phase modulator that is usually realized by the lumped-circuit-type modulator with a low response speed. To obtain an ultrahigh operating speed, we introduce a simple configuration in which two traveling-wave-type phase modulators are cascaded in series but with opposite traveling-wave directions. As a result, polarization-independent, high-speed modulation/wavelength switching characteristics are realized.