Abstract
M.Ing.
Bragg gratings are important components for sensing and for wavelength-division
multiplexed optical communication systems. These gratings are manufactured by
either side-writing of the fiber with a high intensity UV light through a phase mask,
or by exposing the fiber to interference fringes through an interferometer arrangement.
With one phase mask, only a small range of grating wavelengths is possible. This is
achieved by pre-straining the fiber during the writing process. The limitation arises
from the break strength of the fi ber, allowing a maximum range of Bragg wavelengths
of only approximately 10 nm. The interferometric technique uses a beam splitter to
divide a single input UV beam into two and intersecting them at the fiber. The angle
at which the beams intersect will determine the period of the interference fringes and
thus the Bragg grating written in the optical fiber. The Argon-ion laser is used with a
1060 nm phase mask (used to split beam) to write Bragg gratings with reflections from
1012 to 1600 nm. Three accurate- translation and rotation stages are used to keep
the fiber at the beam intersection. Alignment, mechanical stability and coherence of
laser are critical.