30cm of spatial resolution using pre-excitation pulse BOTDA technique

Abstract

A pre-excitation pulse technique in Brillouin optical time domain analysis (PP-BOTDA) for enhancement of the spatial resolution is shown. The technique here exposed is based on the pre-excitation of the stimulated Brillouin scattering and the subtraction of the Brillouin scattering due to the intensity dc level present in the optical pulse. A main optical pulse with 3ns of duration followed by a pulse of 40ns and half the intensity of the main one are used for obtaining 30cm of spatial resolution. The spatial range is 3600m on a standard single mode optical fiber.

Brillouin Distributed Fiber Sensors: An Overview and Applications

“…To overcome this constraint, several techniques that include variations on the probe and handling the pumping (or probe) intensity have been proposed. In the timedomain pumping schemes, the more significant methods are (1) prepumping [30,31], (2) differential pulse-width pairs (DPP-BOTDA) with or without phase shift [32][33][34][35], (3) dark pulses [36] (by these methods, cm or even mm scale spatial resolution has been demonstrated [37,38]), and (4) dynamic Brillouin gratings (DBGs) [39].…”

“…The mentioned methods achieve the goal of simultaneously high spatial and spectral resolution thanks to an acoustic field preactivated by a low intensity prepump pulse [31][32][33][34][35][36][37][38][39][40][41] or a continuous pump background [42] (see Figure 7). Even, when the pump is restored to a nonnull intensity after the pulse, it interacts with the decaying acoustic wave, producing "echoes" in the acquired signal [35].…”

Chirped fiber Brillouin frequency-domain distributed sensing

“…5 Since the temperature and strain dependencies of the Brillouin frequency (typically ∼1.2 MHz∕K 6 and 500 MHz∕%, 7 respectively, near 1550 nm for conventional fiber 5 ) are not insignificant, it is natural that this phenomenon has been adapted for use in distributed sensor technologies, [8][9][10][11] with very impressive results. High-sensitivity and resolution measurement schemes and configurations have been demonstrated, [12][13][14][15][16][17][18][19][20] and a commercial market exists for such distributed sensing systems. Resolution is defined in this context to be the ability to resolve two events that are in close proximity to each other, or alternatively, to resolve a certain temperature or strain change within a given range in the sensor fiber.…”

Signal processing using artificial neural network for BOTDA sensor system

“…Among them, Brillouin Optical Time Domain Analyzer (BOTDA) sensor systems have been well developed for distributed temperature and strain sensing, which are useful in structural health monitoring, geotechnical engineering and so on [5][6][7][8]. In such systems, two counter-propagating signals, pump and probe with different frequencies, interact with an acoustic wave.…”