A novel digital phase tracking algorithm for a high resolution fibre Bragg grating based sensor system

The development of a high-resolution, optical fibre Bragg grating sensor system is described that incorporates a novel digital, condition-based, phase-tracking algorithm for unwrapping the 2π phase ambiguity and permits the continuous up/down phase-tracking of multiple fringe changes. An all-fibre, Michelson interferometric phase-measurement approach is utilised for the determination of strain and temperature induced Bragg wavelength shifts. The system incorporates orthoconjugate mirrors and a stabilised reference channel to compensate for polarisation and random thermal induced drifts and has the potential for resolving sub-μstrain and mK temperature changes with a resolutions of <100n/√Hz (at 1Hz) and <10mK respectively.

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