Investigation On Noise Suppression Of Brillouin Amplification And Dual Signal Amplification Competition

Aiming at the problems in the detection systems operating under the conditions of strong background illumination such as the submarine laser communication, lidar system working by day and so on, a new approach to raise detection sensitivity and signal noise ratio(SNR) by using Brillouin amplification is presented. Simply increasing the pump energy could increase the signal magnification, but also increases the noise intensity. Based on the above background, this paper advances a single-pumped, double-signal Brillouin amplification program, which uses non-collinear strong signal weaken the noise, and then amplify the collinear weak optical signal. Thereby enhancing the signal noise ratio.Firstly, this article introduces stimulated Brillouin scatters's basic physical process, derives the coupled wave equations of Brillouin amplification. Based on these equations, allowing for the plane wave approximation and the oscillation amplitude slowly changing approximation,I establishe the common Brillouin amplification theoretical model and the theoretical model of Brillouin amplification including noise.Then, research the ABS noise characteristic and enervating it. I establish the ABS noise physical model, analyse its production mechanism, the spatial distribution situation. And experimental research the relations between ABS noise and the pump, the profile characteristic and so on. Then research the collinear signal weaking the ABS noise. Discover that the relationship between the signal and the noise is investigated theoretically and experimentally. When the signal increases, the noise intensity become small, moreover the noise pulse width become narrow. This provides fundamental basis for the single pump, double signal Brillouin amplification scheme. Finally, research the competition and enlargement relations between two signals and the noise restraint in this case. In order to obtain the high signal magnification and high signal-to-noise ratio, let the collinear weak signal incidence first and the non-collinear big signal incidence later. Here I mainly research the non-collinear influence the collinear signal and the ABS noise, obtaining the conditions for optimizing the amplifier performances. For an input signal of～10-6mJ, an gain of～106 was obtained. If considered to make the signal-to-noise ratio to be biggest, can enlarge the 10-6mJ collinear small signal 105 times, at the same time reduce the ABS noise to about 1%. The Brillouin amplification of weak signals in low noise is realized.