title: Modal power decomposition of beam intensity profiles into linearly polarized modes of multimode optical fibers.
abstract: We calculate the modal power distribution of a randomly and linearly polarized (LP) multimode beam inside a cylindrical fiber core from knowledge of spatial-intensity profiles of a beam emitted from the fiber. We provide an exact analysis with rigorous proofs that forms the basis for our calculations. The beam from the fiber end is collimated by a spherical lens with a specific focal length. The original LP-mode basis is transformed by the spherical lens and forms another orthogonal basis that describes the free-space beam. By using this basis, we calculate the modal power distribution from the mutual-intensity profile. This is acquired by adopting a well-known mutual-intensity-profile-retrieving technique based on measurements of the intensity patterns several times after two orthogonal cylindrical lenses with varying separation. The feasibility of our decomposition algorithm is demonstrated with simulations.
authors.affiliation: Optoelectronics Research Centre, University of Southampton, Southampton, SO17 1BJ, UK. dbs@orc.soton.ac.uk
authors.forename: Daniel Beom Soo
authors.initials: DB
authors.lastname: Soh
authors.forename: Johan
authors.initials: J
authors.lastname: Nilsson
authors.forename: Seungin
authors.initials: S
authors.lastname: Baek
authors.forename: Christophe
authors.initials: C
authors.lastname: Codemard
authors.forename: Yoonchan
authors.initials: Y
authors.lastname: Jeong
authors.forename: Valery
authors.initials: V
authors.lastname: Philippov