Ring fiber-optic sensor systems

摘要

A resonant fiber-optic sensor using a general ring fiber is proposed. A frequency sweep sinusoidal intensity modulated laser beam is injection locked to the ring fiber sensor using a fiber coupler of low coupling coefficient. The ring fiber is a resonant ring as well as an extracted carrier . In respect that the resonant ring of difference length has difference resonant frequency, the systems operating in the length range 0.6-2 meters and resonant frequency range 100-300MHz, frequency division multiplexing has been used in these sensor systems. Demodulation was achieved by using frequency tracking demodulator that uniform amplify signals in large bandwidth and a narrow band filter in it, so that it has a high signal to noise rate(SNR). According to the experiments with a general ring fiber, the method is very easy and inexpensive to implement, demodulation linearity over 1 decades and minimum relative variation detection ～0.1% attained. The ring fiber sensors have certain advantages that include high sensitivity, large bandwidth, and ease in implementing multiplexed or distributed sensors. Strain, temperature and pressure are the most appropriate measurands in the systems.