Experimental analysis of a new multipoint integrated-optic vibrometer

A multipoint vibration sensor realized in integrated optics is presented. The sensor is composed of four optical heads that have been conceived for the simultaneous measurement of vibrations (in terms of displacement) in several points of a vibrating mechanical system with the aim of an industrial diagnostic. The system presented here is realized on small silicon chips (28 mm×28 mm) using integrated optic (IO) technology, each chip realizing a dual Michelson interferometer. The conditioning and acquisition system for the signal, based on an A/D conversion board is reported together with a brief description of the optical circuit. Experimental tests carried out on the sensor have provided maximum velocity and maximum operating frequency of the sensing system. Frequency response function tests carried out with a commercial single-point laser Doppler displacement sensor are reported in the present article together with the laboratory setup and test results. The network of vibration sensors in integrated optics, the object of the study, have proven to be capable of measuring the vibration displacement of varnished metal surfaces optically untreated with good accuracy (1% standard uncertainty on the instantaneous amplitude) in a frequency range 0–200 Hz with surface velocities up to 100 mm/s. Limitation of the data processing unit have been discussed for vibration frequencies higher then 200 Hz.