基于循环频移器(RFS)载波产生原理，创新性地提出了一种在循环频移环路中插入一个非对称马赫曾德尔干涉仪(AMZI)，通过抑制噪声来提高信噪比的多载波产生改进方案。理论推导出光信号功率和放大自发辐射(ASE)噪声功率通过非对称马赫曾德尔干涉仪后的表达式。根据假设，在干涉仪两臂的光程差远远大于ASE噪声的相干长度，同时远远小于光信号相干长度的条件下，ASE噪声功率降低了3 dB，而光信号功率没有改变。同时通过仿真和实验分别得到了50个子载波的输出。结果表明，基于该改进方案产生的多载波的载噪比可以达到37.5 dB，比传统结构最多提高了17.5 dB。

According to the theory of multi-carrier generation based on recirculating frequency shifter (RFS), a modified scheme for multi-carrier generation to improve signal to noise ratio (SNR) through noise suppression by inserting an asymmetric Mach-Zehnder interferometer (AMZI) in the RFS loop is proposed creatively. The formulas of optical signal power and amplified spontaneous emission (ASE) noise power after AMZI are deduced. According to the assumption that the AMZI arms optical path difference is much shorter than the coherence length of the laser and longer than the coherence length of the ASE noise, ASE noise is reduced by 3 dB without affecting the optical signals power simultaneously. 50 output subcarriers are generated with both simulation and experiment confirmations, respectively. The results show that carrier to noise ratio of the multi-carrier generated by the improved scheme can be as high as 37.5 dB and is up to 17.5 dB higher than the traditional structures.