Surface roughness measurement based on fiber optic sensor

•Multi-wavelength fiber sensor for measuring surface roughness is proposed.•Light scattering intensity ratio has good linear relationship with roughness.•Relative error of surface roughness is 2.92–13.4%, this is acceptable.•Average relative error is about 7.48%, this is acceptable.•Accuracy of multi-wavelength fiber sensor is twice than single wavelength.

The multi-wavelength fiber sensor for measuring surface roughness and surface scattering characteristics were investigated. In this paper, specimens with different surface roughness were analyzed by using 650 nm, 1310 nm and 1550 nm laser as the light source, respectively. The working distance of 2 mm was chosen as the optimum measurement distance. The experimental results indicate that multi-wavelength fiber sensor can accurately measure surface roughness, and can effectively reduce the unsystematic error. The light scattering intensity ratio has a good linear relationship with the surface roughness. The minimum relative error of the surface roughness is 2.92%, the maximum relative error is 13.4%, and the average relative error is about 7.48%. The accuracy for measuring surface roughness by multi-wavelength fiber sensor is about twice as large as that by single-wavelength fiber sensor.