Distributed Brillouin sensing with sub-meter spatial resolution: modeling and processing

Abstract

A general analytic solution for Brillouin distributed sensing in optical fibers with sub-meter spatial resolution is obtained by solving the acoustical-optical coupled wave equations by a perturbation method. The Brillouin interaction of a triad of square pump pulses with a continuous signal is described, covering a wide range of pumping schemes. The model predicts how the acoustic wave, the signal amplitude and the optical gain spectral profile depend upon the pumping scheme. Sub-meter spatial resolution is demonstrated for bright-, dark-and π-shifted interrogating pump pulses, together with disturbing echo effects, and the results compare favorably with experimental data. This analytic solution is an excellent tool not only for optimizing the pumping scheme but also for post-processing the measured data to remove resolution degrading features. ©2011 Optical Society of AmericaOCIS codes: (060.2370) Fiber optics sensors; (290.5900) Scattering, stimulated Brillouin. References and links1. L. Thévenaz, "Brillouin distributed time-domain sensing in optical fibers: state of the art and perspectives,"Front. Optoelectron. China 3(1), 13-21 (2010

Localized and stationary dynamic gratings via stimulated Brillouin scattering with phase modulated pumps

“…Since the acoustic velocity is orders of magnitude slower than the speed of light, the acoustic wave, generated by the optical pump waves at a given z, can be regarded as a local, time-dependent but non-propagating disturbance [1,8]. The temporal evolution of the density wave magnitude is governed by the following equation [1,8]:…”

“…The measurement range of a standard B-OTDA can reach tens of km, however its spatial resolution is fundamentally restricted to the order of 1 m by the acoustic lifetime: The use of either pump or probe pulses much shorter than τ leads to SBS amplification that is both weaker and spectrally broadened [7]. Recent, more advanced B-OTDA techniques rely on elaborate, multiple pulse patterns and multiple scans to provide an order-of-magnitude higher resolution, at the cost of added complexity (see [8] for a detailed analysis and [9,10] for a recent review, and references therein).…”

Rating the performance of a Brillouin distributed fiber sensor

“…This expression is valid for pulses longer than the acoustic amplitude lifetime τ=11 ns, so that the stationary approximation for the acoustic wave can be used. It must be pointed out that advanced configurations based on the pre-excitation of the acoustic wave turn out to experience a power transfer that is also given by Equ.1, provided that the pre-excitation is long enough to let the acoustic wave reach its steady state value 19 , so that this expression can safely be used for all ranges of spatial resolution.…”

Sensitive and Accurate Dispersion Map Extraction of HNLFs by Frequency Tuning of a Degenerate FWM

“…In the first two runs, the power traces of either of the probe sidebands for two states of PSw are obtained while the FWM pump is on. Measured traces of OSC relating to the probe power at location z = 0 of fiber can be written as [25], [28]:…”