Dynamic strain measurement with kHz-level repetition rate and centimeter-level spatial resolution based on Brillouin optical correlation domain analysis

Abstract

In this paper, we propose and demonstrate an ultrahigh-speed Brillouin optical correlation domain analysis (BOCDA) with a single-position sampling rate of 200 kS/s and a spatial resolution of 8 cm. The Brillouin gain spectrum (BGS) is obtained by using a data subtraction scheme rather than the conventional lock-in amplifier (LIA) detection configuration, thus removing the limitation of measurement speed imposed by the LIA. Meanwhile, a voltage controlled oscillator (VCO) is used to sweep the frequency interval between the pump and the probe rapidly. As a proof of concept, we implement measurements of various dynamic strains with frequencies up to 20 kHz at arbitrary position. Moreover, to implement high-speed distributed measurements of Brillouin frequency shift (BFS) along the whole fiber under test (FUT), we propose a novel measuring method which moves the correlation peak and sweeps the pump-probe frequency interval simultaneously. A repetition rate of 1 kHz is verified by measuring dynamic strains with frequencies up to 200 Hz, for distributed measurements performed with 200 points.

Enhancement of Strain/Temperature Measurement Range and Spatial Resolution in Brillouin Optical Correlation Domain Analysis Based on Convexity Extraction Algorithm

“…However, the measurement speed is normally less than 100 points/s due to the limited working bandwidth of the LIA. To achieve dynamic measurements, an injectionlocking scheme along with a balanced detection method is introduced [26], thus removing the limitation induced by LIA. A polarization-maintaining fiber (PMF) is used as the FUT to avoid the polarization-dependent gain fluctuation.…”

“…As another successful method, Brillouin correlationdomain sensors based on sinusoidal frequency modulation are able to simultaneously provide high spatial resolution, high measurement accuracy, high measurement speed, and low complexity [3], [20]- [26]. In this scheme, both the pump lightwave and the probe lightwave are sinusoidally modulated to synthesize periodical correlation peaks along the FUT.…”

Super-speed high-resolution distributed Brillouin sensor for mapping strain waves propagating an optical fiber

“…In basic BOCDA systems that adopt a lock-in amplifier and a microwave sweeper, the sampling rate is limited to kHz level [18][19]. When a balance detector and a voltage-control oscillator (VOC) are introduced the sampling rate is increased to the level of hundreds of kHz [20][21].…”

Recent progress in slope-assisted Brillouin optical correlation-domain reflectometry

“…Their performance has been dramatically enhanced, and even sub-centimeter spatial resolution and real-time operation have been achieved. Another Brillouin-based distributed sensing technique is a correlation-domain technique, which include Brillouin optical correlation-domain analysis (BOCDA) [26][27][28][29][30][31][32][33][34][35][36][37][38][39][40] and Brillouin optical correlationdomain reflectometry (BOCDR) . These techniques have not only sub-centimeter spatial resolution but also a unique advantage of random accessibility to measuring points.…”