Vibration: history and measurement with an extrinsic Fabry–Perot sensor with solid-state laser interferometry

Abstract

We have studied the history of vibration and demonstrate a laser-based noncontact interferometric vibration sensor. The sensor promises the measurement of microdisplacement by using a Fabry-Perot cavity formed between a partially coated gradient-index lens and a movable reflector. Displacement is determined by the detection of interference fringes caused by phase modulation within the cavity. The sensor was tested in conjunction with both multimode and single-mode fiber transmission. Calibration with multimode fiber produced a fringe-contrast function that decreased monotonically with displacement. This calibration allowed at least 30 fringes to be discriminated, giving a displacement resolution of 0.034 microm across a range of 10.2 microm. Dynamic tests demonstrated a working range of at least 3.74 microm at frequencies as high as 2 kHz. Similar tests in which single-mode fiber was used indicated a dynamic working range of at least 4.29 microm.

The Possibility of a Simultaneous Transmission οf Ultrasound and Laser Radiation via Flexible Optical Silica Glass Fibre

“…The number of fringes can be used to calculate the displacement amplitude of an optical fibre (D). One fringe corresponds to half of the length of light wave [13][14][15][16][17]. Displacement amplitudes of the optical fibre were specified on the basis of the graphs presented in Fig.…”

Resolution Improvement in Fabry-Perot Displacement Sensor Based on Fringe Counting Method

“…Several algorithms have been proposed for the past few years. This includes wavenumber spacing method [6], combination of Fourier transform method and minimum mean square error estimation (MMSE)-based signal processing method [7], control and phase demodulation technique [8], and frequency modulated phase generated carrier (FMPGC) demodulation scheme based on the arctangent (Arctan) algorithm [9], and Fringe Counting Method (FCM) [10]- [12]. Nevertheless, all these methods have their own shortcomings.…”

Multi-longitudinal mode fiber-optic vibration sensor

“…There are several kinds of fiber-optic vibration sensors. For example, the vibration can be measured by an extrinsic Fabry-Perot sensor [9]. Another Bragg grating-based laser sensor system that is able to measure vibration was demonstrated by K. P. Koo et al [10].…”