Multicomponent laser strainmeter using Fabry-Perot interferometers

A laser strainmeter for observing small strain changes of a medium by measuring changes of diameters of a container disposed in the medium, said laser strainmeter comprising:

• a plurality of sensor resonators, each resonator comprising a multiple reflection interferometer having a pair of concave mirrors which are attached to an inner wall of said container to face each other in a diametrical direction of said container so that optical axes of said sensor resonators extend in different directions;
• a reference resonator comprising a multiple reflection interferometer having a pair of concave mirrors which are disposed in the vicinity of said sensor resonators, and which are held at a fixed distance from each other;
• and
• laser oscillators which are connected to said sensor and reference resonators through optical fibers, respectively, so that laser light beams having the same resonance frequencies as those of the associated resonators are transmitted from said laser oscillators to said resonators through said optical fibers;
• wherein change in distance between the pair of concave mirrors of each of said sensor resonators is obtained from difference in resonance frequency between each sensor resonator and said reference resonator, thereby obtaining a strain change of the medium in which said container is buried.