Dual wavelength fiber-optic polarimeter for path-integrated strain sensing: Application to the measurement of local slope on a flexible beam
Abstract
An all-optical fiber, single-ended, polarimetric sensor system has been developed and characterized for applications in structural strain measurement, particularly in the aerospace field. Laser diode optical sources were operated at multiple wavelengths to achieve interferometric quadrature, and hence provide a linear sensor strain response. System behavior for path-integral strain measurements under DC conditions was determined for two sensors surface-adhered to aluminum cantilever beams. Linear strain responses were obtained which agreed well with theoretical sensitivities. The strain sensitivity of the polarimetric sensor at temperatures from 25 to 60 C was also found to be consistent with theory. One sensor was tested up to the 14-Hz second mode of beam vibration as a novel point-slope measuring device. The sensor responded linearly to changes in the relative orientation of its endpoints, as predicted by theory. Excellent angular tracking was demonstrated. The experimental observations are interpreted in terms of a comprehensive theoretical discussion of the polarimetric sensor's behavior, taking into account the effects of strain, temperature, and wavelength. A detailed analysis of the limitations of the sensor system is included, and recommendations are made as to the optimum practical implementation of this sensor for real applications.
- Publication:
-
Thesis Toronto Univ. (Ontario). Inst. for Aerospace Studies
- Pub Date:
- October 1990
- Bibcode:
- 1990toru.rept.....T
- Keywords:
-
- Fiber Optics;
- Polarimeters;
- Strain Gages;
- Strain Measurement;
- Structural Strain;
- Beams (Supports);
- Diodes;
- Lasers;
- Performance Tests;
- Quadratures;
- Spacecraft Structures;
- Structural Analysis;
- Structural Mechanics