Abstract
Power-coupling models are inherently unable to describe certain mode
coupling effects in multimode fiber (MMF) when using coherent sources at high
bit rates, such as polarization dependence of the impulse response. We develop
a field-coupling model for propagation in graded-index MMF, analogous to the
principal-states model for polarization-mode dispersion in single-mode fiber.
Our model allows computation of the fiber impulse response, given a launched
electric-field profile and polarization. In order to model both spatial- and
polarization-mode coupling, we divide a MMF into numerous short sections,
each having random curvature and random angular orientation. The model can
be described using only a few parameters, including fiber length, number of
sections, and curvature variance. For each random realization of a MMF, we
compute a propagation matrix, the principal modes (PMs), and corresponding
group delays (GDs). When the curvature variance and fiber length are small
(low-coupling regime), the GDs are close to their uncoupled values, and scale
linearly with fiber length, while the PMs remain highly polarized. In this
regime, our model reproduces the polarization dependence of the impulse response
that is observed in silica MMF. When the curvature variance and fiber length
are sufficiently large (high-coupling regime), the GD spread is reduced, and
the GDs scale with the square root of the fiber length, while the PMs become
depolarized. In this regime, our model is consistent with the reduced GD spread
observed in plastic MMF.
© 2009 IEEE
PDF Article
More Like This
Cited By
You do not have subscription access to this journal. Cited by links are available to subscribers only. You may subscribe either as an Optica member, or as an authorized user of your institution.
Contact your librarian or system administrator
or
Login to access Optica Member Subscription