150  km fast BOTDA based on the optical chirp chain probe wave and Brillouin loss scheme

Abstract

Distributed long-range Brillouin optical time domain analysis (BOTDA) is an extremely time-consuming sensing scheme, which requires frequency mapping of the Brillouin spectrum and a large number of average times. Here, we propose a fast long-range BOTDA based on the optical chirp chain (OCC) probe wave and Brillouin loss scheme. The OCC-modulated probe wave is enabled by cascading fast-frequency-changing microwave chirp segments headto-tail, which covers a large frequency range around the anti-Stokes frequency relative to the pump wave. The combination of the OCC technique and Brillouin loss scheme provides several advantages, i.e., fast measurement, a high Brillouin threshold, no additional amplification scheme, and freedom from the nonlocal effect. In the experiment, 6 m spatial resolution, 3.2 s measurement time, and 3 MHz measurement precision were achieved over a 150 km singlemode fiber.

Recent Progress in Fast Distributed Brillouin Optical Fiber Sensing

“…A zoom-in view within the blue box is illustrated in Figure 15b, which clearly shows that the main peaks have frequency-shifts as the strain ranges from 0.0 µε to 700 µε. [1,47] have been implemented to recover the whole BGS or BLS in the time-domain thanks to the time-frequency mapping of the chirp signal. As demonstrated in Figure 14a, with a high-performance AWG, the frequency-sweeping process can be compressed into an optical chirp segment with a few tens of nanoseconds and the frequency ranged from 1 ν to N ν by the OFA technique.…”

High-Performance Distributed Brillouin Optical Fiber Sensing

“…To reduce the measurement time, several novel fast schemes are proposed, and their common point is to avoid frequency scanning or speed up the frequency switching. These schemes include: optical frequency comb technique [18][19][20][21][22], slope-assisted technique [23][24][25][26][27][28][29], optical frequency-agile technique [30][31][32][33], and the optical chirp chain (OCC) technique [34][35][36][37][38], based on which the measurement time has been reduced to millisecond and even to microsecond.…”

Ultrafast Resolution-Enhanced Digital Optical Frequency Comb-Based BOTDA with Pump Pulse Array Coding

“…To eliminate these two major factors that consume the sensing time, several sweeping-free techniques have been proposed to realize fast and dynamic measurements, such as slope-assisted BOTDA [ 7 , 8 ] and ultrafast sweeping BOTDA [ 9 , 10 ]. Besides, digital optical frequency comb (DOFC)-based BOTDA [ 11 , 12 , 13 ] and chirp-chain-based BOTDA [ 14 , 15 , 16 ] are presented, which are able to reconstruct the BGS and locate the BFS with one single shot. The combination of DOFC-BOTDA and multiple pump pluses provides a better signal-to-noise ratio (SNR) and breaks the inherent limitation between the spatial resolution and the detection accuracy within 0.1 ms [ 17 ].…”

“…The combination of DOFC-BOTDA and multiple pump pluses provides a better signal-to-noise ratio (SNR) and breaks the inherent limitation between the spatial resolution and the detection accuracy within 0.1 ms [ 17 ]. The chirp-chain-based BOTDA utilizing the Brillouin loss scheme achieves 150 km long range fiber sensing within a few seconds [ 14 ].…”

“…Besides, the multiple-pump-pulses scheme requires an identical power of pulses, which is difficult to achieve with a high peak power of pulses [ 17 ]. Some of the fast sensing schemes can provide a fine resolution or long sensing distance by a large amount of averaging, leading to a long measuring time (a few seconds) and missing the dynamic information [ 14 ].…”