为了克服光源频率调制深度、信号相位延迟、伴生调幅等参数对基于正交项解调的相位生成载波(OT-PGC)解调方法的影响，提出一种基于固定相位延迟的PGC检测方法(FPD-PGC)，采用3×2耦合器产生固定相位延迟，分别利用两路信号的倍频信号进行解调。详细阐述了该方法的检测原理，分析了关键参数的影响。当伴生调幅系数为0.4时，仿真对比了FPD-PGC方法与OT-PGC方法的解调性能，结果表明新方法谐波比提高30 dB以上，系统信噪比(SNR)也有显著改善。对实际信号进行解调，得到了类似结果。分析及实验表明该方法完全消除了信号相位延迟的影响，较好地抑制了调频深度和伴生调幅的影响。

In order to eliminate the effects of frequency modulation depth, signal phase delay and intensity accompanying modulation on phase generated carrier demodulation approach using orthogonal terms (OT-PGC), a new PGC method is proposed based on fixed phase delay (FPD-PGC) introduced by 3×2 directional coupler. The second harmonics of two interferometric signals are used for demodulation. The demodulation principle of the new method is described in detail and its performances are studied. The harmonic suppression ratio (HSR) of the new method is increased by more than 30 dB compared with OT-PGC method under the condition of intensity accompanying modulation coefficient of 0.4 according to simulation. The signal-to-noise ratio (SNR) is also improved significantly. Experimental test shows the same result. Theoretical analysis and experimental results show that the new method eliminates the effect of signal phase delay and suppresses the impacts of frequency modulation depth and intensity accompanying modulation to a great extent.