ABSTRACT
We describe the retrieval of nighttime lidar profiles by use of a large holographic optical element to simultaneously collect and spectrally disperse Raman-shifted return signals. Results obtained with a 20-Hz, 6-mJ/pulse , frequency-tripled Nd:YAG source demonstrate profiles for atmospheric nitrogen with a range greater than 1 km for a time average of 26 s.
ABSTRACT
The operation of a fiber Bragg grating strain sensor system that uses interferometric determination of strain-induced wavelength shifts and incorporates a reference channel to compensate for random thermal-induced drift in the output is described. This system is shown to be capable of resolving sub-microstrain changes in the quasi-static strain applied to a grating and has a resolution of ~6 x 10(-3) microstrain/ radicalHz at a strain perturbation frequency of 1 Hz.
ABSTRACT
A description and demonstration of a fiber interferometer that uses a short segment of silica hollow-core fiber spliced between two sections of single-mode fiber to form a mechanically robust in-line cavity are presented. The hollow-core fiber is specifically manufactured to have an outer diameter that is equal to the outer diameter of the single-mode lead fibers, thereby combining the best qualities of existing intrinsic and extrinsic Fabry-Perot sensors. A dynamic strain resolution of ~22 nepsilon/ radicalHz at frequencies of >5 Hz with a sensor gauge length of 137 microm is demonstrated.
