Highly birefringent microstructured optical fiber for distributed hydrostatic pressure sensing with sub-bar resolution

Abstract

We demonstrate distributed optical fiber-based pressure measurements with sub-bar pressure resolution and 1 m spatial resolution over a ∼100 m distance using a phase-sensitive optical time-domain reflectometry technique. To do so, we have designed a novel highly birefringent microstructured optical fiber that features a high pressure to temperature sensitivity ratio, a high birefringence and a mode field diameter that is comparable to that of conventional step-index single mode fibers. Our experiments with two fibers fabricated according to the design confirm the high polarimetric pressure sensitivities (−62.4 rad×MPa −1 ×m −1 and −40.1 rad×MPa −1 ×m −1 ) and simultaneously low polarimetric temperature sensitivities (0.09 rad×K −1 ×m −1 and 0.2 rad×K −1 ×m −1 ), at a wavelength of 1550 nm. The fiber features a sufficiently uniform birefringence over its entire length (2.17×10 −4 ± 7.65×10 −6 ) and low propagation loss (∼3 dB/km), which allows envisaging pressure measurements along distances up to several kilometers.