Fiber-optic thermometric probe utilizing GRIN lenses

A multimode optical fiber thermometer is described, which makes use of a single fiber for light guiding and a thermochromic solution as a differential absorption temperature transducer. The probe has a novel design and utilizes graded-index microlenses to achieve high coupling efficiency between fiber and transducer. Technical data of the electrooptic unit, along with the working principle of the probe are presented, and calibration tests of the thermometer are given.