Distributed analysis of forward stimulated Brillouin scattering for acoustic impedance sensing by extraction of a 2nd-order local spectrum*

Abstract

Distributed fiber sensors based on forward stimulated Brillouin scattering (F-SBS) have attracted special attention because of their capability to detect the acoustic impedance of liquid material outside fiber. However, the reported results were based on the extraction of a 1st-order local spectrum, causing the sensing distance to be restricted by pump depletion. Here, a novel post-processing technique was proposed for distributed acoustic impedance sensing by extracting the 2nd-order local spectrum, which is beneficial for improving the sensing signal-to-noise ratio (SNR) significantly, since its pulse energy penetrates into the fiber more deeply. As a proof-of-concept, distributed acoustic impedance sensing along ∼ 1630 m fiber under moderate spatial resolution of ∼ 20 m was demonstrated.

Distributed temperature–strain sensor based on inter-mode Kerr four-wave mixing of PMF: proposal and proof-of-concept

“…This much weaker IM-FSBS scattering is caused by the strong phonon dissipation at the thick coating layer. [18][19][20][21][22][23] Therefore, although the IM-FSBS scattering coefficient for uncoated PMF exposed in air (∼1.2 W −1 km −1 17) ) is comparable with IM-KFWM, the dominated physical mechanism in this work was IM-KFWM, instead of IM-FSBS.…”

“…Note that for distributed optomechanical sensing, higher signal-to-noise ratio (SNR) and sub-meter spatial resolution as high as 0.8 m 18,19) has been achieved through intra-mode FSBS of single mode fiber, however, all of the reported results via intra-mode FSBS suffer from the noise due to differential operation. [18][19][20][21][22][23] In this work, an attempt was made to realize distributed temperature-strain sensing based on the inter-mode Kerr fourwave mixing (IM-KFWM) of the PMF. To the best of our knowledge, this is the first report for distributed temperaturestrain sensing using IM-KFWM of PMF.…”

Temperature and strain sensitivities of surface and hybrid acoustic wave Brillouin scattering in optical microfibers

“…SBS has been studied intensely in applications such as forward/backward Brillouin sensors [7][8][9][10][11] and distributed/point fiber sensing. [12][13][14][15][16][17] Qian et al realized the sensitive enhancement of a fiber laser sensor by Brillouin slow light. [18] Liu et al realized a triple Brillouin frequency spacing Brillouin fiber laser sensor for temperature measurement.…”