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 Encyclopedia of Physical Science and Technology  EN005F-954  June 15, 2001  20:48




















                                     Fiber-Optic Chemical Sensors






              David R. Walt
              Israel Biran
              Tarun K. Mandal
              Tufts University



               I. Introduction
              II. Fundamental Principles of Fiber-Optic
                 Chemical Sensors
              III. Sensing Schemes for Fiber-Optic
                 Chemical Sensors
              IV. Applications of Fiber-Optic Chemical Sensors
              V. Recent Developments
              VI. Conclusions








              GLOSSARY                                          Imaging fiber Bundle of coherently ordered individual
                                                                  optical fibers through which an image can be transmit-
              Absorption Process by which electromagnetic energy is  ted from one side to the other.
                transferred to an atom or molecule. Different molecules  Immobilization Attachment of chemical species to sur-
                absorb light at different discrete wavelengths and there-  faces, polymers, or other insoluble substrates. For ex-
                fore each molecule has a characteristic absorption  ample, with optical sensors, indicators are attached to
                spectrum.                                         the optical fiber surface.
              Antibody Biologically derived molecule able specif-  Indicator Molecule that undergoes changes in optical
                ically to recognize and bind to another molecule  properties on interaction with chemical species.
                (antigen).                                      Intrinsic sensor Sensor based on the direct spectroscopic
              Biosensor Sensor in which the sensing material is of bi-  detection of a molecule of interest.
                ological origin (e.g., enzyme, antibody, cell, DNA).  Optical fiber Transparent filament made out of glass or
              Extrinsic sensor Sensor based on indirect analysis using  plastic through which light can propagate by total in-
                an indicator (compound that changes optical properties  ternal reflection.
                by reaction with an analyte).                   Sensing element Combination of sensing materials (indi-
              Fluorescence Emission of light at a longer wavelength  cators and/or biological compounds) and a transducer
                by molecules or other chemical species after excitation  (optical fiber).
                at a shorter wavelength.                        Sensing material Material (indicator, dye, polymer,




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