An apparatus and method for use with a coherent optical source to detect
environmental changes. The apparatus comprises: an optical cavity,
including an input coupling port, and an optical fiber section; a
detector optically coupled to the optical cavity to monitor radiation in
the optical cavity; and a processor electrically coupled to the detector
for analyzing the environmental changes adjacent the detection portion of
the optical cavity based on a rate of decay of the radiation in the
optical cavity monitored by the detector. The optical fiber section of
the optical cavity includes a detection portion coated with a conductive
layer capable of supporting a surface plasmon to provide cavity loss. The
surface plasmon is responsive to the environmental changes adjacent the
detection portion. The coherent optical source is optically coupled to
the input coupling port of the optical cavity to provide the radiation in
the optical cavity.