Abstract
The Low-Finesse Fabry-Perot(F-P) cavity, as a kind of fiber-optic sensor probe frequently used, can be applied to detect
physical parameters of strain, temperature, acoustic wave, pressure, and so on, and is an important optical sensing
component. In this paper, sensing properties of low-finesse F-P cavity is deeply and systemically analyzed. At first, the
interference principle of F-P cavity is illuminated from three aspects which include the distribution of light power, the
characteristic of interference fringe and the sensitivity. Considering the spectrum of incident beam obeys a Gaussian
distribution, the intensity distribution of reflected beam is approximate to a cosine function within a Gaussian envelope
and the visibility of interference fringes follows a Gaussian distribution also. Moreover, the operating point of low
finesse F-P cavity must be held near the quadrature-point for the maximum sensitivity. The operating characteristic of FP
cavity is analyzed from three aspects including linearity, property of temperature and contrast of fringe. Analyzing
results show that the F-P cavity can offer the linearity of 2.2%, and the fringe contrast drops as the length of F-P cavity
increases. In addition, the F-P cavity is insensitive to the change of environmental temperature and possesses an excellent
capability to suppress the temperature disturbance. Finally, a test scheme is established to verify the sensor performance
of F-P probe. Test results indicate that the F-P cavity offers the sensitivity of 7.5V/um and the measuring accuracy of
9.4nm, and can well satisfies the practical requirement.