Distributed phase birefringence measurements based on polarization correlation in phase-sensitive optical time-domain reflectometers

Abstract

Abstract:In this paper a technique to measure the distributed birefringence profile along optical fibers is proposed and experimentally validated. The method is based on the spectral correlation between two sets of orthogonally-polarized measurements acquired using a phase-sensitive optical time-domain reflectometer (φOTDR). The correlation between the two measured spectra gives a resonance (correlation) peak at a frequency detuning that is proportional to the local refractive index difference between the two orthogonal polarization axes of the fiber. In this way the method enables local phase birefringence measurements at any position along optical fibers, so that any longitudinal fluctuation can be precisely evaluated with metric spatial resolution. The method has been experimentally validated by measuring fibers with low and high birefringence, such as standard single-mode fibers as well as conventional polarizationmaintaining fibers. The technique has potential applications in the characterization of optical fibers for telecommunications as well as in distributed optical fiber sensing.

Chirped-pulse phase-sensitive reflectometry: hearing behind the walls with high fidelity

“…High measurand resolutions over long ranges can therefore be highly time consuming. The maximum achievable resolution is also limited by the pulse spectral content [7], in a somewhat similar manner to the temperature resolution limitation imposed by the spectral width of the Brillouin gain curve in Brillouin sensors.…”

“…Based on this principle ΦOTDR systems have been demonstrated to allow for very sensitive, quantitative measurements of temperature/strain [6] and birefringence [7] with high measurand resolutions. With these techniques, the demonstrated temperature resolutions (typ.…”

Highly sensitive distributed birefringence measurements based on a two-pulse interrogation of a dynamic Brillouin grating

“…While a high birefringence is intentionally imposed during the fabrication of polarisation-maintaining fibres (PMF), birefringence can also be highly affected by external environmental perturbations, thus giving the possibility to perform sensing of quantities such as temperature, strain, electric current, hydrostatic pressure, and others [1][2][3][4][5][6][7][8][9][10] . Although there exist several techniques for birefringence measurement, most of them can only measure the average birefringence value, thus limiting those methods only to discrete sensing applications.…”

Discrimination of temperature and strain by combined refractive index and birefringence measurements using coherent Rayleigh sensing

“…Thus, for instance, the phase birefringence profile along polarization-maintaining (PM) fibers can be retrieved by dynamic Brillouin gratings (DBG), optical frequency-domain reflectometry (OFDR) and coherent optical time-domain reflectometry (COTDR) [3][4][5] . Since the birefringence is also dependent on environmental variations, all methods for birefringence measurements can be used for distributed temperature and strain sensing, leading to sensitivities one order of magnitude higher than in a Brillouin sensor 3 .…”