Fig. 1. Principle of laser heterodyne interferometry

Fig. 2. Simulation of power spectral density of displacement noise at different measurement optical lengths. (a) 0; (b) 10 m; (c) 20 m; (d) 30 m

Fig. 3. Simulation of relationship between root mean square (RMS) of power spectral density of displacement noise and measurement optical length in different bandwidth ranges. (a) 0.9‒1.1 MHz; (b) 9‒11 MHz; (c) 2‒30 MHz

Fig. 4. Simulation of relationship between RMS of power spectral density of displacement noise and laser frequency noise

Fig. 5. Simulation of influence of length compensation on RMS of power spectral density of displacement noise

Fig. 6. Diagrams of experimental systems. (a) No delay fiber; (b)with delay fiber; (c) with delay fiber and compensation

Fig. 7. Experimental results of power spectral density of displacement with 30 m delay fiber and 30 m compensation fiber. (a) No delay fiber; (b) with delay fiber; (c) with delay fiber and compensation fiber

Fig. 8. Experimental results of power spectral density of displacement with 154.1 m delay fiber and compensation fiber of same length. (a) No delay fiber; (b) with delay fiber; (c) with delay fiber and compensation fiber