The fiber-optic recirculating delay line is made by closing a continuous strand of single-mode fiber on itself, using a directional coupler. By inserting a linear polarizer after a fiber-optic recirculating delay line, the system becomes highly polarization-dependent. The transfer function and the phase-induced intensity noise for different polarization inputs are studied for this case. The period of both functions can be halved as a result, and the PIIN spectrum can exhibit maximum noise instead of minimum noise at frequencies f equals n (loop delay). By controlling the polarization of the field, the depth of filtering notches at frequencies f equals (n plus 0. 5)/ tau can be varied, where tau is the delay, without changing the coupling coefficient of the coupler, thus enabling the RF filter to be polarization controlled.
|State||Published - 1988|