理论研究了基于级联四波混频系统的信噪比(SNR)优化。级联四波混频过程包括相敏和非相敏级联两种方式，其中非相敏级联系统的探测光强度始终被放大，同时SNR始终被降低；而相敏级联系统的探测光强度可以被放大或减小，这取决于两个铷池内光场的总相位调控。在相同增益条件下，相敏级联四波混频系统的有效增益比非相敏级联系统的高。另外，当两个铷池内光场的总相位等于0或者2π时，相敏级联四波混频系统中探测光的强度可以呈最大倍数放大，且SNR也被提高到最大。

Theoretical research on the optimization of the signal-noise ratio (SNR) based on the cascaded four-wave mixing process is performed. This cascaded four-wave mixing process includes the phase-sensitive and phase-insensitive two cascaded methods. In the phase-insensitive cascaded system, the intensity of the probe beam is always amplified and the SNR of the probe beam is always reduced. However, in the phase-sensitive cascaded system, the intensity of the probe beam can be either amplified or reduced which depends on the total phase modulation of the light field in two Rb pools. Under the same intensity gain condition, the efficient gain in the phase-sensitive cascaded four-wave mixing system is greater than that in the phase-insensitive cascaded four-wave mixing system. In addition, when the total phase of the light field in two Rb pools is equal to 0 or 2π, both the intensity of the probe beam shows an amplification with the maximal amplitude, and the SNR is increased to the maximal value in the phase-sensitive cascaded four-wave mixing system.