Rajesh, M; Dr.Nampoori,V P N(Cochin University of Science & Technology, July , 2006)
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Abstract:
The thesis presented the fabrication and characterisation of
polymer optical fibers in their applications as optical amplifier and smart sensors.Optical polymers such as PMMA are found to be a very good host material due
to their ability to incorporate very high concentration of optical gain media like
fluorescent dyes and rare earth compounds. High power and high gain optical
amplification in organic dye-doped polymer optical fibers is possible due to
extremely large emission cross sections of oyes. Dye doped (Rhodamine 6G)
optical fibers were fabricated by using indigenously developed polymer optical
fiber drawing tower. Loss characterization of drawn dye doped fibers was carried
out using side illumination technique. The advantage of the above technique is
that it is a nondestructive method and can also be used for studying the
uniformity in fiber diameter and doping. Sensitivity of the undoped polymer
fibers to temperature and microbending were also studied in its application in
smart sensors.Optical amplification studies using the dye doped polymer optical fibers were
carried out and found that an amplification of l8dB could be achieved using a
very short fiber of length lOcm. Studies were carried out in fibers with different
dye concentrations and diameter and it was observed that gain stability was
achieved at relatively high dye concentrations irrespective of the fiber diameter.Due to their large diameter, large numerical aperture, flexibility and geometrical
versatility of polymer optical fibers it has a wide range of applications in the field
of optical sensing. Just as in the case of conventional silica based fiber optic
sensors, sensing techniques like evanescent wave, grating and other intensity
modulation schemes can also be efficiently utilized in the case of POF based
sensors. Since polymer optical fibers have very low Young's modulus when
compared to glass fibers, it can be utilized for sensing mechanical stress and
strain efficiently in comparison with its counterpart. Fiber optic sensors have
proved themselves as efficient and reliable devices to sense various parameters
like aging, crack formation, weathering in civil structures. A similar type of study
was carried out to find the setting characteristics of cement paste used for
constructing civil structures. It was found that the measurements made by using
fiber optic sensors are far more superior than that carried out by conventional
methods. More over,POF based sensors were found to have more sensitivity as
well.
Description:
International School of Photonics,
Cochin University of Science & Technology