Fiber optic measuring device with compensation for reflections in the fiber optic and with a possibility of simultaneous measurement of several quantities

Claim 1

A fiber optic measuring device for measuring physical and chemical quantities, comprising: at least one measuring transducer adapted to influence the spectral composition of incident light such that emitted light from the measuring transducer includes a spectrum having at least one wavelength interval different than another wavelength interval of the incident light, said measuring transducer including a material having an optical absorption edge within at least one wavelength interval coinciding with the spectrum of said emitted light such that the dependence of the response spectrum of the emitted light on the measured quantity induces wavelength displacement of said absorption edge; an evaluating electronic unit including at least one source of said incident light; at least one light conducting fiber interconnecting said measuring transducer and said evaluating electronic unit for transmitting said incident light from said at least one source to said measuring transducer and emitted light from said measuring transducer to said evaluating electronic unit; said evaluating electronic unit further including at least one photo-detector and an optical coupling device for coupling said incident light into said at least one light conducting fiber and for coupling light from said at least one light conducting fiber to said photo-detector; an optical filter means positioned in the light ray path between said at least one light conducting fiber and said photo-detector for analyzing the emitted light spectrum from said at least one measuring transducer, said optical filter means having filtering spectra dividing the emitted spectrum from said measuring transducer into at least three non-identical wavelength intervals; said photo-detector being adapted to measure the emitted light to measure the filtered emitted light from said optical filter means and generating detector signals in the respective wavelength intervals; and said evaluating unit further including means for multiplying the detector signals by constants including the constant unity, means for forming the difference between said detector signals multiplied by said constants, and means for forming the quotient therebetween.