Abstract
M.Ing.
Optical fibre Bragg gratings are a periodic variation of the refractive index
in the core of an optical fibre andmay be formed by exposure to intense UV
laser light under specific conditions. Light at a certain wavelength, called
the Bragg wavelength, is reflected back when illuminating the grating with
a light source. Bragg gratings can relatively easily be employed as strain
and temperature sensors, but have small sensitivity for pressure. Special
transducers are required to increase the sensitivity. A pressure sensor was
manufactured by coating a fibre Bragg grating with a polymer. The polymer
coating converts transverse pressure into longitudinal strain through
the Poisson effect inside the polymer coating. This thesis investigates the
sensitivity of themanufactured Bragg grating pressure sensor, by using the
method of finite element analysis. An account of the experimental setup,
whereby the Bragg grating is written with a frequency tripled Nd:YAG
laser, is given. The process whereby the fibre is coated with the polymer
is described. The sensor is characterized through experimental results and
a comparison is made between theoretical and experimental results. Uses
for this sensor and ways with which the sensitivity may be increased are
suggested as future work.