Fig. 1. Fabry-Perot etalon. (a) Design diagram; (b) physical device

Fig. 2. Ideal transmission functions of Fabry-Perot etalon with reflectivity of 95% and 80%, respectively

Fig. 3. Schematic of Fabry-Perot etalon adjusting system

Fig. 4. Spot on white screen

Fig. 5. Schematic of absolute distance measurement of femtosecond pulse laser

Fig. 6. Experimental data processing, when $D$=0.4960 mm. (a) Frequency domain interference signal; (b) three peaks in time domain; (c) wrapped phase; (d) unwrapped phase

Fig. 7. Measurement results. (a) Measured value and standard value; (b) deviation of measured value ; (c) standard deviation of measured value