The influence of lateral pressure on the propagation constant of grapefruit microstructure optical fibers is theoretically
investigated using a full-vector finite element method in this paper. With the different direction of lateral pressure, the change of
the propagation constant of grapefruit microstructure optical fibers is different. At present, the report of this aspect has not
been found out. The research has great signification in microstructure fiber sensors especially multidimensional optical fiber
An innovative algorithm based on the evolutionary programming (EP) method is developed for recovering distributions of axial strain along a fiber grating from its reflection spectral response. The proposed method exhibits a number of attractive features that prove to be effective for solving the inverse problems. The basics of EP are reviewed and the detailed programming procedures of the proposed algorithm are presented. By combining EP and the matrix method for calculating the reflection spectrum of a FBG, we obtain a new method for the distributed sensing. The numerical simulations show good agreements between the original and the reconstructed strain profiles.
A novel temperature-independent FBG-type torsion sensor has been proposed and analyzed. Two FBGs with different Bragg wavelengths are symmetrically bonded to the surface of the torsion beam with an identical angle. This sensor is able to achieve torsional angle measurement over the range from -40° to +40° without suffering from the influence of temperature within the range between -15°C and 75°C.
In this paper, we propose a novel and simple method to measure the force vector by bonding the uniform fiber Bragg grating along the erect main strain line of the structure. With the same direction but various magnitudes or with the same magnitude but different directions, the center wavelength and bandwidth may both change. Based on the different responses of the reflection spectrum, we can measure the direction as well as magnitude of various forces in theory. We also offer some elementary experiment results to demonstrate the feasibility of this sensing principle. The experimental results are in agreement with our theoretical analysis.