A rotational-angle sensor composed of two Fiber Bragg gratings glued axially on a cylindrical cantilever beam to be bent by the resultant repulsion force of three magnets is designed and proposed for detecting the rotary random position of a rotor. By means of using three different materials on cantilever beams for checking each feature’s effect on this fiber optic sensor, it has been experimentally confirmed that a nearly identical performance is achieved among them. From these experimental results, a maximum deviation of 1.3 deg is obtained and it is in good agreement with the theoretical prediction. As a whole, the cantilever design exploited in this proposed optical fiber sensor configuration is independent of the intrinsic materials used. This sensor can provide a robust kind of technique for accurately measuring the rotational angle or rotational rate of a rotor in an arbitrary rotational direction for a wide range of industrial applications.
We demonstrated that a high-sensitivity fiber sensor based on a superstructure fiber grating (SFG) can simultaneously measure the pressure and temperature by encapsulating the grating in a polymer-half-filled metal cylinder, in which there are two openings on opposite sides of the wall filled with the polymer to sense the pressure. The mechanism of sensing pressure is to transfer the pressure into the axial extended-strain. According to the optical characteristics of an SFG composed of a fiber Bragg grating (FBG) and long period grating (LPG), the various pressure and temperature will cause the variation of the center-wavelength and reflection simultaneously. Thus, the sensor can be used for the measurement both of the pressure and temperature. The pressure sensitivity of 2.28×10<sup>-</sup><sup>2</sup>MPa<sup>-1</sup> and the temperature sensitivity both of 0.015nm/°C and -0.143dB/°C are obtained.
An all-fiber pressure sensor based on a fiber Bragg grating with the pressure sensitivity of 2.2x10<sup>-2</sup> MPa<sup>-1</sup> has been demonstrated. The physical configuration includes a FBG encapsulated in a polymer-half-filled metal cylinder with its end bonded to the central of a round plate attached to the surface of polymer, and the Young’s modulus of the polymer is four orders lower than FBG. This cylinder has two opening on opposite side of the wall at the polymer part. Under the pressure environment, the polymer can be pressurized along one radial direction only, and responds an axial force acting on the round plate, producing an axial strain on FBG. With a nice linearity, this sensor should be applied potentially for the measurement of mediums pressure, liquid level and depth underwater.
The application of the acoustic-induced vibration on a fiber Bragg grating has been proposed as the function of controlling reflectivity levels and switching reflection wavelengths. Moreover, a switchable multi-wavelength optical filter is expected to develop for various applications in optics. Thus an acousto-optic interaction in a superstructure fiber grating (SFG) can provide a multi-wavelength reflective filter with the function of switching the operation wavelength. In this paper, we experimentally demonstrated that the channels of a blazed SFG could be increased or switched as the acoustic waves were launched into the fiber. When the acoustic wave is applied in the fiber and travels along the fiber axis, the cladding modes of a blazed SFG can couple back to the core mode by acousto-optic interaction in the fiber. The grating reflectivity and the number of the induced wavelength channels can be controlled by acoustic flexural amplitude. Thus, this device acts as a switchable multi-wavelength comb filter for the applications in a WDM system, or in fiber lasers or in fiber sensors.