Optical heterodyne micro-vibration measurement based on all-fiber acousto-optic frequency shifter

Abstract

An all-fiber optical heterodyne detection configuration was proposed based on an all-fiber acousto-optic structure, which acted as both frequency shifter and coupler at the same time. The vibration waveform within a frequency range between 1 Hz to 200 kHz of a piezoelectric mirror was measured using this optical heterodyne detection system. The minimal measurable vibration amplitude and resolution are around 6 pm and 1 pm in the region of tens to hundreds of kilohertz, respectively. The configuration has advantages of compact size, high accuracy and non-contact measurement. Moreover, it is of a dynamically adjustable signal-to-noise ratio to adapt different surface with different reflections in the measurement, which will improve the usage efficiency of the light power.

Optical Heterodyne Microvibration Detection Based on All-Fiber Acousto-Optic Superlattice Modulation

“…Furthermore, we also measured the frequency response of the PZM in the frequency range of 1 Hz to 150 kHz with V pp =10 V. The vibration amplitude decreased in general with increasing driving frequency. This is similar with the case reported in [14], so the measured results of the frequency response is not presented here. Apart from the sinusoidal vibration, the measurement of the complicated waveforms and related displacements were also experimentally achieved.…”

“…Note that the first all-fiber acousto-optic frequency shifter was constructed by using a dynamic grating introduced by the acoustic flexural wave in a two-mode fiber (TMF) in 1986 [11,12], and has been used to construct fiber-optic Fabry-Perot interferometers [13]. In 2015, we have also constructed an all-fiber optical heterodyne detection configuration based on an all-fiber acousto-optic structure [14], which acted as both the frequency shifter and the coupler at the same time. This configuration has high measurement accuracy and adjustable SNR in measurement of actual objects.…”

“…Because the complex vibration can be written as the sum of its Fourier components, a simple vibration u(t)=Ucos(2f0t) with only one Fourier component is considered with U and f0 being the amplitude and the frequency of the vibration, respectively. The phase modulation signal can produce a sequence of frequency sidebands whose amplitudes are given by a standard Bessel function expansion [14]  …”

Quantitative characteristic of phase signal with changed pulse in the coherent PHI-OTDR system

“…As above has been discussed, several structures have been developed to retrieve the phase information on the fiber. Among these structures, the coherent detection system which is widely used in the field of optical measurement is consequently and largely applied in the dynamic measurement of -OTDR due to its simple configuration and long sensing range [12][13][14]. In this structure, H. Cai et al have put forward the concept of digital coherent demodulation and successfully realized the phase extraction in the -OTDR system [15].…”

Nonzero-drift differential all-fiber-optic heterodyne Doppler measurement system

“…Compared with the homodyne configuration, heterodyne Doppler measurement systems offer much higher sensitivity and accuracy and much stronger anti-interference ability. 16,17 In all-fiber-optic heterodyne Doppler measurement systems, acousto-optic frequency shifters (AOFSs) are commonly used to achieve the frequency shift of the signal or reference beam. 15,[17][18][19][20][21] AOFSs offer low insertion loss, high extinction ratio, fast response, and relatively high-frequency stability and are compatible with fiber-optic paths.…”