Design of a pressure sensor based on optical fiber Bragg grating lateral deformation

Abstract

This paper describes steps involved in the design and realization of a new type of pressure sensor based on the optical fiber Bragg grating. A traditional pressure sensor has very limited usage in heavy industrial environments, particularly in explosive or electromagnetically noisy environments. Utilization of optics in these environments eliminates all surrounding influences. An initial motivation for our development was the research, experimental validation, and realization of a complex smart pressure sensor based on the optical principle. The main benefit of this solution consists of increasing sensitivity, resistance to electromagnetic interference, dimensions, and potential increased accuracy.

Keywords: fiber Bragg grating; fiber optic; pressure sensor.

Figure 1.

(a) Cross-section of the FBG with marked fiber shape (dashed line) under pressure. (b) Schematic drawing of the FBG with indicated direction of applied pressure. (c) Spectral response of the FBG depending on the applied strain and temperature.

Figure 2.

Design pressure sensor that is used for computational model, and subsequently in manufacturing process.

Figure 3.

Complete measurement setup with super luminescent diode as the source of optical signals, optical path components and spectral analyzer for evaluation of reflected optical signals from the sensing FBG. The red line shows the optical signal trace and the blue arrow the direction of an applied pressure.

Figure 4.

(a) Global and (b) detailed FEM computational model of pressure sensor based on the fiber Bragg grating deformation.

Figure 5.

(a) Von Mises stress distribution and (b) X-direction deformation in the membrane for pressure of 2 bars.

Figure 6.

Relationship of maximal Von Mises stress in the optical fiber on an optical fiber line load with respect to a strength limit of 1,100 MPa and safety factor of 1.5.

Figure 7.

(a) Measured spectral characteristics from realized pressure sensor (notes: Inc—incrementing pressure, Dec—decrementing pressure). (b) Dependence of applying pressure on the resulted calculated peaks wavelength distance value.

Figure 8.

(a) 3D manufacturing drawing of a pressure sensor capsule (b) Realized pressure sensor capsule from stainless steel with second reference FBG placed outside the sensor.