Intensity and phase modulated multimode fiberoptic sensors are described. Cross-talk between two multimode fibers has been used to develope sensors for the detection of oil films on the surface of water and for analog liquid level and temperature measurements. Frustrated total reflection at the end of an optical fiber is used for detecting air or gas bubbles and for measuring refractive index and turbidity of liquids. Development of multimode interferometer in the form of Fiber Fabry-Perot sensor (FFP) is described. The versatility of multimode FFP sensors is demonstrated and the advantages of multimode technology in fiber-optic interferometry are indicated.
