Frequency-domain analysis of dynamically applied strain using sweep-free Brillouin time-domain analyzer and sloped-assisted FBG sensing.

Fast reconstruction of the whole Brillouin gain spectrum is experimentally demonstrated using sweep-free Brillouin optical time-domain analysis (SF-BOTDA). Strain variations with the frequencies up to 400 Hz are spectrally analyzed, achieving strain sensitivity of 1 microstrain per root Hz at a sampling rate of 5.5 kHz and a spatial resolution of 4m. The results favorably compare with fiber Bragg grating sensing.

Nondegenerate four-wave-mixing-based radio frequency up/downconversion using a parametric loop mirror.

We propose a method of reconfigurable radio frequency up/downconversion using a parametric optical loop mirror. The baseband optical signal can be unconverted to a carrier-suppressed radio-over-fiber signal at a wide range of frequencies without the help of optical filters to remove the optical carrier. Upconversion of up to 60 GHz and downconversion from 40 GHz for both single-channel and wavelength-division-multiplexing signals using the same setup are demonstrated.

Sweep-free distributed Brillouin time-domain analyzer (SF-BOTDA).

A frequency-sweep-free method for distributed Brillouin sensing is proposed, having the potential for fast dynamic strain measurements. In this reported implementation of the method, multiple probe waves with carefully chosen optical frequencies simultaneously propagate in the fiber against an equal number of sequentially-launched, short pump pulses of matching frequencies, where each of pump-probe pair replaces one sweeping step in the classical BOTDA technique. Experimentally, distributed sensing is demonstrated with a spatial resolution of a few meters.