Decrease in Photosensitivity of Erbium-Doped Fiber Under Tension: Implications for Distributed Feedback Fiber Lasers

Applying strain to a fiber prior to grating inscription is often used to provide some flexibility in the design wavelength for phase mask based grating fabrication systems. Although earlier studies have characterized germanosilicate fibers under strain, an analysis has never been performed on photosensitive erbium-doped fiber (EDF). For this experiment, arrays of 10-mm-long gratings were written in EDF under various strains and exposure conditions. As with studies performed in passive fiber, a decrease in the photosensitivity of the EDF was observed with increasing strain. The reduction in grating strength with strain was characterized and utilized to model the threshold of distributed feedback fiber lasers inscribed at various strains. Multiplexed arrays of fiber lasers were then fabricated to verify the simulations.