SELF-CALIBRATING OPTICAL FIBER PRESSURE, STRAIN AND TEMPERATURE SENSORS

摘要

Broadband energy incident on a transducer having partially or fully reflective surfaces separated by a gap which is greater than the coherence length of the broadband energy but smaller than one-half a coherence length of a band of energy within said broadband energy causes a portion of the spectral content of the broadband energy corresponding to a coherence length greater than twice the gap length to exhibit interference effects while the average power of the broadband energy remains unaffected. Splitting energy reflected from the transducer into two beams which are filtered at preferably similar center frequencies but with different pass bands yields beams which are radically different in sensitivity to changes in gap length. Analyzing the beams to derive a ratio of powers (since source intensity and fiber attenuation in a common fiber are thus self-cancelling) allows high accuracy and high resolution absolute measurement of temperature, pressure or strain.