Optical Carrier-Based Microwave Interferometers for Sensing Application
Optical fiber interferometers (OFIs) have been extensively utilized for precise measurements of various physical/chemical quantities (e.g., temperature, strain, pressure, rotation, refractive index, etc.). However, the random change of polarization states along the optical fibers and the strong dependence on the materials and geometries of the optical waveguides are problematic for acquiring high quality interference signal. Meanwhile, difficulty in multiplexing has always been a bottleneck on the application scopes of OFIs. Here, we present a sensing concept of optical carrier based microwave interferometry (OCMI) by reading optical interferometric sensors in microwave domain. It combines the advantages from both optics and microwave. The low oscillation frequency of the microwave can hardly distinguish the optical differences from both modal and polarization dispersion making it insensitive to the optical waveguides/materials. The phase information of the microwave can be unambiguitly resolved so that it has potential in fully distributed sensing. The OCMI concept has been implemented in different types of interferometers (i.e., Michelson, Mach-Zehnder, Fabry-Perot) among different optical waveguides (i.e., singlemode, multimode, and sapphire fibers) with excellent signal-to-noise ratio (SNR) and low polarization dependence. A spatially continuous distributed strain sensing has been demonstrated.
J. Huang et al., "Optical Carrier-Based Microwave Interferometers for Sensing Application," Proceedings of SPIE, Fiber Optic Sensors and Applications XI, vol. 9098, SPIE, May 2014.
The definitive version is available at https://doi.org/10.1117/12.2050482
SPIE Sensing Technology + Applications (2014: May 8-9, Baltimore, MD)
Electrical and Computer Engineering
Keywords and Phrases
Fiber optic sensors; Interferometers; Interferometry; Microwaves; Multimode fibers; Optical waveguides; Refractive index; Sapphire; Interferometric sensor; Microwave interferometer; Microwave interferometries; Microwave Photonics; Optical fiber interferometers; Polarization dependence; Polarization dispersion; Signaltonoise ratio (SNR); Microwave oscillators; Optical carrier based microwave interferometers
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