Shen, K.; Yuan, J.; Li, M.; Wen, X.; Lu, H. Measurement of the Acoustic Relaxation Absorption Spectrum of CO2 Using a Distributed Bragg Reflector Fiber Laser. Sensors2023, 23, 4740.
Shen, K.; Yuan, J.; Li, M.; Wen, X.; Lu, H. Measurement of the Acoustic Relaxation Absorption Spectrum of CO2 Using a Distributed Bragg Reflector Fiber Laser. Sensors 2023, 23, 4740.
Shen, K.; Yuan, J.; Li, M.; Wen, X.; Lu, H. Measurement of the Acoustic Relaxation Absorption Spectrum of CO2 Using a Distributed Bragg Reflector Fiber Laser. Sensors2023, 23, 4740.
Shen, K.; Yuan, J.; Li, M.; Wen, X.; Lu, H. Measurement of the Acoustic Relaxation Absorption Spectrum of CO2 Using a Distributed Bragg Reflector Fiber Laser. Sensors 2023, 23, 4740.
Abstract
Reconstruction of acoustic relaxation absorption curve is a powerful approach to ultrasonic gas sensing, but requires known of a series ultrasonic absorption at various frequencies around effective relaxation frequency. Ultrasonic transducer is a most widely deployed sensor for ultrasonic wave propagation measurement and works only at a fixed frequency or specific environment like water, so a large number of ultrasonic transducers operating at various frequencies are required to recover an acoustic absorption curve with a relative large bandwidth, which cannot suit for large-scale practical applications. This paper proposes a wideband ultrasonic sensor using a distributed Bragg reflector (DBR) fiber laser for gas concentration detection through acoustic relaxation absorption curve reconstruction. With a relative wide and flat frequency response, the DBR fiber laser sensor measures and restores a full acoustic relaxation absorption spectrum of CO2 using a decompression gas chamber between 0.1 and 1 atm to accommodate the main molecular relaxation processes, and interrogates with a non-equilibrium Mach-Zehnder (M-Z) interferometer to gain a sound pressure sensitivity of -45.4 dB. The measurement error of the acoustic relaxation absorption spectrum is less than 1.32%.
Copyright:
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