An Er-doped bidirectional ring fiber laser with 90/spl deg/ Faraday rotator as phase nonreciprocal element

An Er-doped bidirectional ring fiber laser with 90/spl deg/ Faraday rotator in the resonator is investigated both theoretically and experimentally. Two different single-longitudinal-mode bidirectional behaviors are demonstrated. Namely, generation of the orto-conjugated counterpropagating modes pairs and generation of the complex-conjugated counterpropagating modes pairs are obtained separately. Considerable stabilization of the nonreciprocal frequency bias produced by the Faraday rotator is achieved in the latter case.