| Popis: |
This work presents a system for the interrogation of optical fiber Bragg grating sensors based on time domain reflectometry and fixed filters. In this system, filtering is accomplished by fiber Bragg gratings, and a pulsed broadband light source is employed to illuminate the gratings. The spectral informations from the sensors are related to the ratio of two pulse intensities, each from a different filter. The signals are measured with a unique photodetection system, which makes detection independent of intensity variations and minimizes external influences on the circuit, such as variations in the environment temperature. Also, a small number of optical couplers and circulators are needed, so the interrogation system costs per sensor is considerably reduced. A test approach has been assembled for the interrogation of six sensors. Comparisons between experimental results and simulations show a good agreement. Extrapolations indicate that it would be possible to interrogate sensors with spectral variations up to 2 nm, providing uncertainties smaller than 5 pm, which is adequate for multiplexed sensing of temperature in a range of 200°C. |
