Simultaneous measurement of temperature and acoustic impedance based on forward Brillouin scattering in LEAF

Abstract

The detection of the surrounding environment is one of the most fundamental challenges in optical fiber sensors research. In this Letter, we report two new, to the best of our knowledge, phenomena in large effective area fiber (LEAF), which are the linear dependence of the radial acoustic mode induced forward Brillouin scattering (FBS) spectral linewidth on temperature and the linear dependence of the radial acoustic mode induced FBS spectral frequency shift on acoustic impedance. By utilizing these linear relationships, we present a novel temperature and acoustic impedance simultaneous measurement method based on FBS in LEAF. With a fiber Sagnac loop structure, the obtained measurement uncertainties of temperature and acoustic impedance surrounding LEAF are 0.1°C and 0.006 k g / ( s ⋅ m m 2 ) , respectively. The corresponding measurement uncertainties in the form of relative percentage values are 0.5% and 0.4%, respectively.

Fabrication and Characterization of an Optimized Low-Loss Two-Mode Fiber for Optoacoustic Sensing

“…The obtained measurement uncertainties of temperature and acoustic impedance are only 0.2 °C and 0.019 kg/(s·mm 2 ), respectively, achieving more than 36% accuracy improvements. In the future, combined with BBS-based distributed mechanisms, such as differential pulse-width pair [ 24 ], optical pulse coding [ 25 ] and in-line Raman amplification [ 28 ], the optimized MSI 2-LP-mode will be a new sensing fiber to achieve longer sensing distance or higher spatial resolution for distributed acoustic impedance and temperature simultaneous measurement, which would have potential applications in environmental engineering, chemical engineering and oil–gas reservoirs [ 14 , 20 ]. Furthermore, by employing multiple-input multiple-output (MIMO) and/or combining with a multi-core fiber structure [ 29 , 30 ], the proposed low-loss FMF will also be a good candidate for long-haul mode-division-multiplexing (MDM) and/or SDM to achieve a large enhancement of transmission capacity per optical fiber in the future.…”

“…To date, temperature and acoustic impedance simultaneous measurement methods based on FBS have been reported to use the resonance frequencies of two R 0, m -induced FBS spectra [ 14 ] or the linewidth and resonance frequency of one R 0, m -induced FBSS [ 20 ]. However, due to the limited spatial resolutions and sensing distances of FBS-based distributed acoustic impedance (~2 m and ≤3 km) [ 21 , 22 ] and temperature (~42.5 m and ≤0.4 km) [ 23 ] sensing techniques, it is not easy to achieve the medium/long-distance distributed acoustic impedance and temperature simultaneous measurement with a high spatial resolution using these two sensing methods.…”

“…Different from refs. [ 14 , 20 ], the abovementioned experimental results in which the impedance R 0,7 -induced FBSS and BGS have their individual frequency shift dependencies on temperature and acoustic impedance may provide a novel discriminative measurement method of temperature and acoustic impedance.…”

“…The actual temperatures of these two measured states are controlled at 40.1 °C and 20.1 °C, respectively. In our experiment, the measurement uncertainties of R 0,7 -induced FBSS and BGS can be obtained by calculating the standard deviation of seven measured results [ 14 , 20 ], which are 1.6 kHz and 157 kHz, respectively. Figure 10 a,c show the measured R 0,7 -induced FBSS at State 1 and State 2, where the corresponding central frequencies ( ν 7 _ 0 and ν 7 _ R ) are respectively 320.211 MHz and 319.766 MHz, respectively.…”

Quasi-acoustic impedance matching distributed opto-mechanical sensor with aluminized coating optical fibers

“…Forward stimulated Brillouin scattering (FSBS) is an intriguing nonlinear acousto-optic interaction between laser beams and electrostriction-induced transverse acoustic waves [1]. Since the excited transverse acoustic waves could low-loss transmit and re ect at the boundaries between the cladding, coating, and the ambient media, FSBS has been investigated for diverse acoustic metrologies such as ber diameter monitoring [2,3], temperature [4,5], strain [6,7], ionizing radiation [8] and acoustic impedance sensing [9][10][11][12] in standard bers. By measuring the frequency shift or linewidth of FSBS spectra, the information about the medium outside the optical bers under test (FUTs) is obtained.…”