Fig. 1. Schematic diagram of ultra-long fiber M-Z interferometer

Fig. 2. Experimental setup for the noise measurement of optical fiber interferometer

Fig. 3. Noise spectra of sources under different length differences. (a) Test results of semiconductor laser; (b) test results of fiber laser

Fig. 4. Experimental results. (a) Noise level and fitting value of different length interferometers; (b) comparison of fitting spectrum and theoretical spectrum of thermal noise

Fig. 5. Test results and analysis of ultralong fiber interferometer. (a) Noise analysis of semiconductor laser; (b) noise analysis of fiber laser