| Resumen |
In this work the feasibility of employing two well-known techniques already used on designing optical fiber sensors
is explored. The first technique employed involves monomode tapered fibers, which were fabricated using a taper
machine designed, built, and implemented in our laboratory. This implementation greatly reduced the costs and
fabrication time allowing us to produce the desired taper length and transmission conditions. The second technique
used fiber Bragg gratings, which we decided to have mechanically induced and for that reason we devised and
produced our own mechanical gratings with the help of a computer numerical control tool. This grating had
to be fabricated with aluminum to withstand temperatures of up to 600°C. When light traveling through an optical
fiber reaches a taper it couples into the cladding layer and comes back into the core when the taper ends. In the same
manner, when the light encounters gratings in the fiber, it couples to the cladding modes, and when the gratings end,
the light couples back into the core. For our experimentation, the tapering machine was programmed to fabricate
single-mode tapers with 3 cm length, and the mechanically induced gratings characteristics were 5 cm length, and
had a period of 500 μmand depth of the period of 300 μm. For the conducting tests, the tapered fiber is positioned
in between two aluminum slabs, one grooved and the other plane. These two blocks accomplish the mechanically
induced long period grating (LPG); the gratings on the grooved plaque are imprinted on the taper forming the
period gratings. An optical spectrum analyzer is used to observe the changes on the transmission spectrum as the
temperature varies from 20°C to 600°C. The resultant attenuation peak wavelength in the transmission spectrum
shifts up to 8 nm, which is a higher shift compared to what has been reported using nontapered fibers. As the
temperature increases there is no longer a shift, but there is significant power loss. Such a characteristic can be
used as well for sensing applications. |
