Fast Brillouin optical time domain analysis for dynamic sensing

Abstract

A new technique for the fast implementation of Brillouin Optical Time Domain Analysis (BOTDA) is proposed and demonstrated, carrying the classical BOTDA method to the dynamic sensing domain. By using a digital signal generator which enables fast switching among 100 scanning frequencies, we demonstrate a truly distributed and dynamic measurement of a 100 m long fiber with a sampling rate of ~10 kHz, limited only by the fiber length and the frequency granularity. With 10 averages the standard deviation of the measured strain was ~5 µε.

Single-shot distributed temperature and strain tracking using direct detection phase-sensitive OTDR with chirped pulses

“…With traditional Brillouin Optical Time Domain Analysis (BOTDA), spatial/temperature resolutions of 2m/1.2K over 100 km have been demonstrated [3], but, due to the requirement of a large of number averages and a frequency sweep, the measurement times are still typically of several minutes. Recently, schemes using Brillouin based sensing have been proposed for dynamic strain sensing [4][5][6][7]. In 2011, samplings of 20 Hz were demonstrated in a version of Brillouin optical correlation-domain analysis (BOCDA) [4].…”

“…However typically the range is quite limited in this type of sensors. With a fast implementation of BOTDA [5], samplings of 10 kHz with a standard deviation of strain of 5με were demonstrated, although the technique was best suited for short fibers (100 meters in [5]) and a low number of averages, as a frequency sweep was still required. The same group later demonstrated a practical utilization of the slope-assisted BOTDA to allow for strain measurements without requiring a frequency sweep [6].…”

Brillouin Distributed Optical Fiber Sensor Based on a Closed-Loop Configuration

“…Considering the time-of-flight in the sensing fiber, along with the scan of a large number of frequencies (covering at least the full-width at half-maximum of the BGS) and the use of a large enough number of averaging (to reach a given target measurand accuracy through noise reduction), the whole measurement time turns out to be typically in the order of several minutes, thus restricting classical BOTDA to quasi-static measurements [2]. In order to expedite the measurement process, different methods have been proposed in the literature [4]- [15], in some cases even enabling the use of BOTDA sensing for distributed dynamic measurements. One of these methods circumvents the slow frequency switching time required during scanning, primarily by pre-loading the full set of scanned pump-probe frequency offsets in an arbitrary waveform generator (AWG), commonly designated as fast BOTDA (F-BOTDA) technique [4], [5].…”

“…In order to expedite the measurement process, different methods have been proposed in the literature [4]- [15], in some cases even enabling the use of BOTDA sensing for distributed dynamic measurements. One of these methods circumvents the slow frequency switching time required during scanning, primarily by pre-loading the full set of scanned pump-probe frequency offsets in an arbitrary waveform generator (AWG), commonly designated as fast BOTDA (F-BOTDA) technique [4], [5]. Another way to do without the lengthy frequency scan is to exploit optical frequency combs: the BGS information can be retrieved by generating multi-pump and multi-probe tones simultaneously in a sweep-free BOTDA (SF-BOTDA) technique [6], or utilizing advanced algorithm based on orthogonal frequency division multiplexing (OFDM) [7], [8].…”

“…Based on the working principle of SA-BOTDA, several techniques have been proposed to extend the covered BFS range [12]- [15]. However, the reduction of the BOTDA measurement time using the above-mentioned techniques turns out to systematically degrade other specifications, like a poorer spatial resolution [7], [8], a larger BFS uncertainty [4]- [15], or a limited temperature/strain measurement range [9]- [15].…”