Method and apparatus for measuring the level of liquid using optical fiber strain gauge

The present invention relates to a method of measuring a height of liquid level (water level) and a liquid-level gauge and more particularly, to a method and liquid-level gauge for measurement of a water level of liquid by measuring a change in force acted by liquid (buoyancy or hydrostatic pressure) on a body movably arranged in the liquid as a change in strain or strain level in an optical fiber. For measurement of a liquid level, an optical fiber connected at its one end portion to force receiving means movably arranged in liquid to receive force from the liquid is dipped in the liquid together with the force receiving means, and a change in the force acting on said force receiving means when the liquid level changes is detected as a change in strain in the optical fiber by means of an optical fiber strain gauge connected to the other end of the optical fiber, thus measuring a water level of the liquid.