title: Fabrication of helical long-period fiber gratings by use of a CO2 laser.
abstract: We present a method of helical long-period fiber grating (H-LPFG) fabrication by use of a CO2 laser for use as an optical torque sensor. A conventional optical fiber grating has periodic vertical index changes along its fiber axis, but a H-LPFG has a screw-type index modulation. The helical index modulation is obtained with the asymmetric index change caused by a single-side laser beam exposure. The H-LPFG shows peak shifts with codirectional or contradirectional torsion to the helix. Also, the polarization-dependent loss is measured to be relatively small compared with that of a conventional long-period fiber grating.
authors.affiliation: Department of Information and Communications, Gwangju Institute of Science and Technology, 1 Oryong-dong, Buk-gu, Gwangju 500-712, South Korea. stoh@kjist.ac.kr
authors.forename: Seungtae
authors.initials: S
authors.lastname: Oh
authors.forename: Kyung Rok
authors.initials: KR
authors.lastname: Lee
authors.forename: Un-Chul
authors.initials: UC
authors.lastname: Paek
authors.forename: Youngjoo
authors.initials: Y
authors.lastname: Chung