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Polarization switching in an Er-doped fiber lasers using an intra-cavity electro-optical switch

Optical fiber laser sources with switching capabilities are of interest in applications such as WDM fiber communications systems and optical fiber sensors. In particular, fiber sensor arrangements based on switched optical bridges would benefit with the development of a polarization switched optical source. Such an arrangement could lead to the realization of compact and low noise sensing configurations. We have studied the performance of a fiber laser in which polarization switching is achieved through intra-cavity devices. Besides using bulk optical components within the laser cavity, we have evaluated the switching characteristics with an all-fiber version of the proposed laser configuration. This was realized by means of an intra-cavity electro-optic polarization switch. The effects of intra-cavity losses and length of the gain medium on switching speed of the fiber laser have been experimentally studied. Whereas only low switching frequencies (a few hundred Hz) are attained with the first configuration, the all-fiber arrangement yields switching frequencies limited by the relaxation oscillations of the fiber laser. A simple arrangement for a polarization switched fiber laser is thus demonstrated using commercially available optical fiber devices. The application of this fiber laser source in switched optical bridges is discussed, and the potential features of this type of arrangement are evaluated. Other interesting features observed with this arrangement, such as anti-phase population dynamics, are also discussed.