Introduction

What is OptiFiber?

Telecommunications using fibers as the transmission media is now a major industry.
Choosing appropriate fiber parameters is an important issue for a given optical
system. Cross-sectional dimensions, material composition, and refractive index
profile all influence the losses, dispersion and the nonlinearities of the fiber and must
be chosen carefully to achieve a satisfactory trade off for a given application.

All these parameters of existing fiber samples could be experimentally measured and
then the fiber manufacturing process adjusted towards an optimized production.
However, this trial and error approach is extremely slow, expensive and unreliable.
Moreover, some important fiber parameters, for example the total group-velocity
dispersion and the effective nonlinear coefficient, are not directly measurable with
compact tabletop devices. Because of that, the number of professionals who use an
appropriate fiber design and modeling software is growing constantly across the
photonics industry.

OptiFiber is the leading commercial product in that category. It is a powerful tool that
blends numerical mode solvers for fiber modes with calculation models for group
delay, group-velocity dispersion, effective mode area, losses, polarization mode
dispersion, effective nonlinearity, etc. Among the most powerful features of OptiFiber
are its abilities to predict how any given fiber could be optimized versus a design goal,
for example small, but non-zero dispersion and maximal mode area. In addition,
OptiFiber can supplement and extend the fiber characterization capabilities of real
laboratory devices, such as EXFO’s NR-9200 Optical Fiber Analyzer, by importing
and analyzing the refractive index profiles of real fiber samples. OptiFiber is an
indispensable tool for engineers, scientists and students who design fibers, fiber
components and optical communications systems.

With OptiFiber the user can:

• Design a multilayer fiber with an arbitrary 2D refractive index profile by either:
• Defining the profile internally, using a library of built-in functions or a using a
  user-specified formula
• Importing an external profile (directly supports profiles scanned with NR-
  9200)
• Assign material dispersion based on Sellmeier model or user-defined functions
• Model material losses based on known experimental formulas
• Calculate the following characteristics of any supported mode, fundamental or
  higher order:
• Mode field pattern, displayed in a number of ways
• Effective refractive index and the propagation constant
• Group delay
• Three types of group-velocity dispersion (material, waveguide, total)
• Mode field diameters according to various definitions and eff. mode area
• Estimations of the cutoff wavelengths
• Macrobending, microbending and splicing losses
• Optimize the dependence of these characteristics on numerous technological
  parameters of the fiber:
• geometry, profile shape, composition.
• Calculate and visually compare the parameters of an arbitrary group of modes vs.
  the mode number
• Calculate birefringence effects induced by intrinsic or extrinsic perturbations
• Estimate the PMD based on stochastic model
• Use two alternative ways of defining the profile of the fiber:
• As a refractive index profile.
• As a dopant concentration profile.
• Access the models:
• Macrobending losses of higher order modes.
• Estimations of the cutoff wavelength as given by the ITU-T recommended
  experimental
• procedure.
• Effective mode area.
• Effective nonlinear refractive indices of arbitrary mode as determined by the
  nonlinear indices of
• the bulk materials and on the waveguiding properties of the fiber: shape of
  mode pattern, degree of
• confinement, etc.
• Access a rich material library
• Try the examples.
• Use experimental profiles of real fiber samples scanned with NR-9200 from
  EXFO Inc.

What is new in OptiFiber version 2.0

Meshless mode solvers for LP and vector modes. As with the original mode solver
of OptiFiber, the fibers can consist of an arbitrary number of concentric layers of
lossless materials, and graded index fibers can be approximated using a sequence of
constant index layers. The new mode solvers are different from the original one in that
they do not use meshes to approximate the structure. Instead, they find an exact
solution based on matching boundary conditions at layer boundaries. These mode
solvers should be especially useful for multimode fiber calculations, where there are
many modes in the spectrum. Another advantage of the meshless mode solver is the
calculation of fields far from the fiber. Meshing introduces finite difference errors of a
certain level, and fields weaker than the differencing error cannot be calculated. The meshless mode solvers, on the other hand, have the correct asymptotic behavior far
from the fiber, and can calculate fields of magnitude 10^-15 or less. In OptiFiber
version 2.0, the desired mode solver is selected by radio button in the Modes dialog
box.

Propagation over distance feature. OptiFiber allows users to decompose an
arbitrary field into the modes of a multimode fiber. It calculates the complex
coefficients of the modes for the arbitrary field. Similarly, given the amplitude of a set
of modes, OptiFiber can display the sum (composition of modes). OptiFiber 2.0 can
also calculate this multimode field after propagating down the fiber by a specified
distance. The user enters a distance. Each of the complex coefficients of the modes
is multiplied by the appropriate phase factor, and the new field pattern is displayed in
the preview box.

What is new in OptiFiber 2.1

In OptiFiber 2.1, four enhancements were introduced to the user interface. The first
two enhancements, radius specified instead of layer widths, and layer index specified
relative to cladding, are implemented in a Settings dialog box to customize data entry
and display according to user preference. The parabolic function layer was enhanced
with an option to reverse the sense of direction, and it is now possible to export the
data found in the Cutoff dialog box.

Radius specified instead of layer widths. In OptiFiber, the fiber profile is specified
as a list of Regions (layers) of various widths. There is a read only field to show the
position (radius) of the selected layer. It is now possible to enter the radius of the layer
instead of the layer width. In this option, the width field will become read only instead
of the position field.

Layer index specified relative to cladding. In the Fiber Profile dialog box, the
refractive index of the selected layer is displayed in the Refractive Index field. It is
now possible to specify the refractive index relative to the cladding layer instead. With
this option, when the last layer is selected, the cladding refractive index will be
displayed in the Refractive Index field. However, when other layers are selected, the
index of current layer relative to the cladding layer will be shown. Data entry is also
relative.

Export Cutoff data. An option to export this data to a text file has been added.

Parabolic function layer can go both ways. The parabolic layer has its extreme
value on the left side of the layer by default. Now the layer can have the extreme
value on the right side as well.