title: Thermal properties of highly birefringent optical fibers and preforms.
abstract: Temperature cycling of highly birefringent optical fibers and preforms has been used to investigate the thermal properties of bow-tie and elliptically clad structures. The thermal hysteresis of the birefringence is shown to be a direct consequence of the thermal history of the fiber or preform and has been related to volume changes in the stress-producing borosilicate sections. Annealing increases the axial stress as well as the stress anisotropy and hence the birefringence. Increases of up to a factor of 2 in the birefringence on suitable thermal treatment indicate a new method for further improvement of high birefringence fibers. The implications of the results in the design, fabrication, and use of such fibers are discussed.
authors.affiliation: University of Southampton, Electronics Department, Southampton, S09 5NH, UK.
authors.forename: A
authors.initials: A
authors.lastname: Ourmazd
authors.forename: M P
authors.initials: MP
authors.lastname: Varnham
authors.forename: R D
authors.initials: RD
authors.lastname: Birch
authors.forename: D N
authors.initials: DN
authors.lastname: Payne