Fiber Optic Lever Displacement Transducers: Principles, Improvements, & Applications

The recent flurry of activity in fiber optic sensors has resulted in a great variety of technically sophisticated devices employing interference, polarization and wavelength modulation techniques l. While all of these methods offer great promise for certain specific applications and dedicated sensors, the intensity modulated Fiber Optic Lever Displacement Transducer offers a powerful combination of simplicity, performance, versatility, and low cost, which make it well suited for a wide variety of laboratory and industrial applications. The basic principle employed in the Fiber Optic Lever Displacement Transducer comes down to the use of an adjacent pair of fiber optic elements, one to carry light from a remote source to an object or target whose displacement or motion is to be measured and the other to receive the light reflected from the object and carry it back to a remote photo sensitive detector. A complete analysis of the principles and performance characteristics of this type of transducer was done by R.O. Cook and C.W. Hamm 2. A fiber optic element is a flexible strand of glass or plastic capable of transmitting light along its length by maintaining near total internal reflection of the light accepted at its input end, as shown in Fig-1.