We report for the first time a unique multi-parameter optical fiber sensor based on the stimulated scattering of higher order acoustic modes of Orbital Angular Momentum (OAM) guiding fiber. Both optical modes and acoustic modes guided within the core region of OAM fiber are characterized and demonstrated theoretically and experimentally. Simulation analysis shows that the multi-peak feature in the Brillouin gain spectrum (BGS) of OAM fiber is attributed to the couplings among the guided optical modes and higher-order acoustic modes. The frequency shifts of first two Brillouin peaks are successfully monitored to discriminate the temperature and strain with an accuracy of 0.21oC and 4.6με.
We report two novel fiber-optic vibration sensors based on standard telecom bend-insensitive fiber (BIF). A tapered BIF forming a fiber Mach-Zehnder interferometer could measure continuous and damped vibration from 1 Hz up to 500 kHz. An enclosed microcantilever is fabricated inside the BIF by chemical etching and fusion spliced with a readout singlemode fiber that exhibits a frequency range from 5 Hz to 10 kHz with high signal-to-noise ratio (SNR) up to 68 dB. The unique double cladding structure of the BIF ensures both sensors with advantages of compactness, high resistance to the external disturbance and stronger mechanical strength.
We proposed and experimentally demonstrated a novel tapered polarization-maintaining fiber (PMF) sensor based on analysis of polarization evolution. The unique structure of the tapered PMF demonstrates extraordinary polarization characteristics under external disturbance such as twists and magnetic fields, exhibiting great advantages of compactness, high sensitivity, and versatility.