Photoinduced, refractive-index gratings in germanium-doped two-mode, elliptical-core optical fibers

Permanent, photoinduced refractive-index gratings written along the longitudinal axis of germanium-doped, two-mode, elliptical-core fibers are found to affect the differential phase modulation between the co-propagating LP₀₁ and LP₁₁ even modes. The modal beat length of a two-mode fiber grating is found to vary inversely with strain induced to the fiber and leads to a new type of weighted optical fiber sensor whose sensitivity varies as a function of length along the structure to which it is attached or embedded. A weighting function is imparted to the fiber sensor by way of a chirped, two-mode grating written into the core, the chirp adopting the shape of a specific vibration-mode amplitude. This novel type of spatially-weighted, distributed fiber sensor is shown experimentally to function as an efficient vibration-mode filter by enhancing either the first or second mode of a thin, one dimensional cantilever beam. These results support future applications of spatially-weighted/ distributed optical fiber sensors for the evaluation and control of vibrating structures.

Name thesis:degree_name

Master of Science

Level thesis:degree_level

masters

Discipline thesis:degree_discipline

Electrical Engineering

Department dc:contributor.department

Electrical Engineering

Grantor dc:publisher

Virginia Tech

Year dc:date.issued

1991

Author dc:creator

• Greene, Jonathan A.

Chair dc:contributor.committeechair

• Claus, Richard O.

Committee members dc:contributor.committeemember

• Besieris, Ioannis M.
• Jacobs, Ira

• Optical fibers

Statement dc:rights

• In Copyright

Licence dc:rights.uri

• http://rightsstatements.org/vocab/InC/1.0/

Language dc:language.iso

en_US

Dc Identifier Other

etd-08222009-040313

OAI identifier oai:identifier

oai:vtechworks.lib.vt.edu:10919/44380