We demonstrate a grating recording method using an excimer KrF UV laser for batch imprinting of distributed feedback (DFB) fiber lasers (FL) with complex profiles and high grating strength (up to K<4 cm-1) for underwater acoustic sensing applications. The specially developed FPGA-controlled stepping algorithm allows for the recording of long (up to 52mm) DFB laser structures with step error compensation, chirping and apodisation for the FL side-lobe suppression at arbitrarily high exposures. Batch recording involving simultaneous exposure of a number of fibers placed in the recording zone, to achieve time and cost reduction during manufacturing is demonstrated. A number of different gratings in a passive fiber as well as DFB FL in Er-doped active fiber have been fabricated and studied. Further ways to improve the recording process are proposed.
We have developed an 8-element fibre laser seabed array demonstrating state-of-the art performance characteristics for a
fibre laser sensing system. The system employs sea-state-zero sensitivity hydrophones with a flat acoustic response over
a bandwidth exceeding 5kHz and very low inertial sensitivity. The system contains no outboard electronics and few metal
components making it extremely light, compact, and low complexity. The array may be deployed up to 4 km from a land
or sea based platform to a depth of up to 80m. Power delivery and telemetry for all 8 sensors is achieved via a single 2mm
diameter optical fibre cable weighing less than 5kg per km. We report here results of the first field trials of this system.
We have developed an 8-element fibre laser seabed array demonstrating state-of-the art performance characteristics for a fibre laser sensing system and highlighting the advantage this technology provides in the underwater sensing domain. The system employs sea-state-zero sensitivity hydrophones with a flat acoustic response over a bandwidth exceeding 5kHz and very low inertial sensitivity. The system contains no outboard electronics and few metal components making it extremely light, compact, and low complexity. The array may be deployed up to 4 km from a land or sea based platform to a depth of up to 80m. Power delivery and telemetry for all 8 sensors is achieved via a single 2mm diameter optical fibre cable weighing less than 5kg per km. We report here results of the first field trials of this system.
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