Study of gain factor effect of erbium doped fiber amplifier on noise floor level of fiber-optic interferometric sensor

Abstract

Subject of Research. The paper presents experimental study results of the gain factor effect of an erbium doped fiber amplifier on the noise floor level of a fiber-optic interferometric acoustic sensor. Fiber-optic sensor is based on a Michelson interferometer. The optical amplifier is located behind the compensating interferometer which induces the auxiliary phase modulation to the interference signal. The homodyne demodulation algorithm is used to recover the sensor phase signal. Method. During the experiment there were no external acoustical impacts on the sensor. The power control of optical signals from the fiber amplifier was performed. Noise signals from the sensor were written into data files under the different values of the fiber amplifier gain factor. Spectral estimations of the noise floor level of the fiber-optic interferometric sensor were performed by the averaged modified periodogram method under the different values of the fiber amplifier gain factor. Obtained results were used to define the dependence of the noise floor level of the fiber-optic interferometric sensor on the fiber amplifier gain factor. Main Results. Mean noise floor levels were equal to 64 urad/Hz0.5 at 355 Hz, 68 urad/Hz0.5 at 450 Hz and 66 urad/Hz0.5 at 500 Hz. Experimental results showed insignificant increase of the noise floor level of the fiber-optic interferometric sensor with the growth of the optical amplifier gain factor from 14.6 dB to 25.8 dB. The gain factor increase was about several percent and did not exceed inaccuracies of performed measurements. Practical Relevance. The absence of significant changes in the noise floor level of the considered fiber-optic sensor with the changing of the fiber amplifier gain factor is caused by the intensity noise suppression of the used demodulation scheme. The considered fiber amplifier might be used for the amplification of optical signals from the fiber-optic multiplexed array of fiber-optic sensors without the significant deterioration of their noise performance on condition that the homodyne demodulation algorithm with the intensity noise suppression is used.