For a fiber-grating time-division multiplexing (TDM) sensing system adopting the phase-generated carrier (PGC) modulation and demodulation schemes, the influence of the structure of the sensor array and the modulation and demodulation parameters on the system phase noise is investigated. The theoretical analysis results show that the array will constrain system structure design of modem design and selection of parameters, and by using polarization modulation in the fiber Bragg grating sensing system means to suppress the induced polarization signal fading. When the number of time-division multiplexing is larger, the system frequency modulation demodulation of the lower limit. The simulation analysis of the high-frequency aliasing effect in the PGC modulation and demodulation algorithms show that the smaller the modulation frequency, the greater the background phase noise of the system. In the experiment, four sets of interferometric fiber Bragg grating time-division multiplexing sensor arrays with different design structures are constructed. The PGC modulation frequencies are 6, 10, 16, and 50 kHz. The experimental results show that the phase noises of the first time-division multiplexing channel for the four systems at the frequency of 1 kHz, are -93, -96, -98, and -99 dB/Hz ^1/2, respectively, which are consistent with the theoretical analysis results.