A low-loss interferometric sensor array with unequal segments

An improved layer peeling algorithm removes the constraint of equal segments length in a low-loss interferometric sensor array. Consequently, the construction of the sensor array is greatly simplified while its performance remains essentially unaffected. With unequal segments, the frequency response of the sensor array, which is based on a serial concatenation of High Birefringence (HiBi) fibers, becomes effectively non-periodic. The original version of the layer peeling algorithm was based on scanning one period of the frequency response and expanding it in the form of a Fourier series. This led to decreased sensing performance since in practice it is virtually impossible to fabricate an array of identical segments. In the non-periodic case, we show that broadening the scanning range, as well as windowing the measured frequency dependent Stokes vector, prior to transforming it to the time-domain, greatly reduce sensing errors. The new approach is demonstrated in a 14-segments array of HiBi fibers with a total length of 235m. Sinusoidal strain modulation at up to 65Hz is applied to one of the segments. The improved layer peeling algorithm reveals the induced signal in the perturbed segment with only little crosstalk in the signals extracted from the other segments.