Fiber recirculating delay-line tunable depolarizer.

A new type of all-single-mode fiber depolarizer, based upon a 2 x 2 coupler and a recirculating delay line and useable with a coherent light source, is proposed and demonstrated. The reduction in the degree of polarization is examined theoretically and experimentally. Design criteria and principles are discussed. With a narrow-band laser source, the degree of polarization was tuned between 99.8% and 1.15%. Experiments illustrate how this depolarizer can eliminate the effects of induced polarization fluctuation in a polarization-sensitive fiber-optic system. The experimental results support the theoretical model.