M-Z and Sagnac composite interferometer based on polarization multiplexing

The invention discloses an M-Z and Sagnac composite interferometer based on polarization multiplexing. The composite interferometer comprises an input light source, a polarizer, a circulator, a first coupler, a first polarization beam splitter, a second polarization beam splitter, a first phase modulator, a first optical fiber ring, a first detector, a second detector, a second phase modulator, a second optical fiber ring, a third optical fiber ring, a second coupler, a third detector and a fourth detector. The system comprises a first signal processing unit, a second signal processing unit, a computer, a first electric lead, a second electric lead, a first data transmission line and a second data transmission line. PBS devices are additionally arranged on the two arms of the polarization-maintaining Mach-Zehnder interferometer, so that a loop is formed between the two arms, multiplexing of the Sagnac interferometer and the Mach-Zehnder interferometer is achieved, and after the interferometer is combined with