US 12,467,813 B2
System and method for monitoring Fabry-Pérot cavity displacements
Daniel C. Sweeney, Oak Ridge, TN (US); Anthony Birri, Oak Ridge, TN (US); and Christian M. Petrie, Oak Ridge, TN (US)
Assigned to UT-Battelle, LLC, Oak Ridge, TN (US)
Filed by UT-Battelle, LLC, Oak Ridge, TN (US)
Filed on Jul. 10, 2023, as Appl. No. 18/219,746.
Claims priority of provisional application 63/388,156, filed on Jul. 11, 2022.
Prior Publication US 2024/0011859 A1, Jan. 11, 2024
Int. Cl. G01L 9/00 (2006.01); G01N 17/00 (2006.01)
CPC G01L 9/0079 (2013.01) [G01N 17/00 (2013.01)] 20 Claims
OG exemplary drawing
 
1. A system for measuring variations in time of a length of a Fabry-Perot cavity (FPC), the system comprising:
an optical interrogator apparatus configured to
interrogate the FPC with light,
produce a periodic spectral interference pattern from the light that interrogated the FPC, wherein the periodic spectral interference pattern spans over an operational spectral range {λmin, λmax}, and wherein locations of peaks of the periodic spectral interference pattern vary in time in accordance with the variations of the FPC length, and
output a signal of the peak locations; and
a data processing apparatus communicatively coupled with the optical interrogator apparatus and configured to
receive, from the optical interrogator apparatus, the signal of the peak locations,
determine a reference length of the FPC as an average of FPC lengths corresponding to a reference instance of the signal of the peak locations,
for each instance of the signal of the peak locations following the reference instance,
determine a current length of the FPC as an average of FPC lengths corresponding to a current instance of the signal of the peak locations,
predict peak locations corresponding to the current instance of the signal of the peak locations based on the current length, the reference length, and the reference instance of the signal of the peak locations,
identify as corrected peak locations the corresponding ones from among the peak locations of the current instance of the signal within the operational spectral range that are nearest to the predicted peak locations,
estimate a current FPC length variation as a median of FPC length variations corresponding to the corrected peak locations, the reference instance of the signal of the peak locations, and the reference length, and
determine the current FPC length variation as a median of previously estimated FPC length variations over a moving time window of predetermined duration, and
output a signal of the determined FPC length variations.