| 摘要 |
An apparatus (60) or system (30) for determining a differential time derivative of strain in a device that has a low coherence light source (32) coupled to a plurality of Fabry-Perot etalons (62). The reflected signals from the Fabry-Perot etalons are coupled to a beam splitter (44) or acousto-optic modulator (66). A first beam (48) and a second beam (50) from the output (46) of the beam splitter (44) are combined in at least one interferometer (52, 64). The outputs of the interferometers (64) are detected by a plurality of detectors (124). The outputs of the detectors (124) are coupled to a plurality of FM demodulators (127). The output of the FM demodulators (127) are a plurality of signals proportional to the difference in the time derivative strain at the pair of mirrors (94, 96) of one of the Fabry-Perot etalons (62)
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