48
2 Optical Fiber Structures and Light Guiding Principles
Table 2.2 Common birefringent crystals and some applications
Crystal name
Symbol n o
n e
Applications
Calcite
CaCO 3 1.658 1.486 Polarization controllers and beamsplitters
Lithium niobate LiNbOj 2.286 2.200 Light signal modulators
Rutile
TiO 2
2.616 2.903 Optical isolators and circulators
Yttrium vanadate yvo 4
1.945 2.149 Optical isolators, circulators, and beam displacers
Table 2.2 lists the ordinary index n o and the extraordinary index n e of some
common birefringent crystals that are used in optical communication components
and gives some of their applications.
2.3 Optical Fiber Configurations and Modes
This section first presents an overview of the underlying concepts of optical fiber
modes and optical fiber configurations. The discussions in Sects. 2.3 through 2.7
address conventional optical fibers, which consist of solid dielectric structures.
Section 2.8 describes the structure of photonic crystal fibers, which can be created
to have a variety of internal microstructures. Chapter 3 describes the operational
characteristics of both categories of fibers.
2.3.1 Conventional Fiber Types
An optical fiber is a dielectric waveguide that operates at optical frequencies. This
fiber waveguide is normally cylindrical in form. It confines electromagnetic energy
in the form of light to within its surfaces and guides the light in a direction parallel
to its axis. The transmission properties of an optical waveguide are dictated by its
structural characteristics, which have a major effect in determining how an optical
signal is affected as it propagates along the fiber. The structure basically establishes
the information-carrying capacity of the fiber and also influences the response of the
waveguide to different kinds of environmental perturbations.
The propagation of light along a waveguide can be described in terms of a set
of guided electromagnetic waves called the modes of the waveguide. These guided
modes are referred to as the bound or trapped modes of the waveguide. Each guided
mode is a pattern of electric and magnetic field distributions that is repeated along
the fiber at equal intervals. Only a certain discrete number of modes are capable
of propagating along the guide. These modes are those electromagnetic waves that
satisfy the homogeneous wave equation in the fiber and the electromagnetic field
boundary conditions at the core-cladding interface of the waveguide.
2 Optical Fiber Structures and Light Guiding Principles
Table 2.2 Common birefringent crystals and some applications
Crystal name
Symbol n o
n e
Applications
Calcite
CaCO 3 1.658 1.486 Polarization controllers and beamsplitters
Lithium niobate LiNbOj 2.286 2.200 Light signal modulators
Rutile
TiO 2
2.616 2.903 Optical isolators and circulators
Yttrium vanadate yvo 4
1.945 2.149 Optical isolators, circulators, and beam displacers
Table 2.2 lists the ordinary index n o and the extraordinary index n e of some
common birefringent crystals that are used in optical communication components
and gives some of their applications.
2.3 Optical Fiber Configurations and Modes
This section first presents an overview of the underlying concepts of optical fiber
modes and optical fiber configurations. The discussions in Sects. 2.3 through 2.7
address conventional optical fibers, which consist of solid dielectric structures.
Section 2.8 describes the structure of photonic crystal fibers, which can be created
to have a variety of internal microstructures. Chapter 3 describes the operational
characteristics of both categories of fibers.
2.3.1 Conventional Fiber Types
An optical fiber is a dielectric waveguide that operates at optical frequencies. This
fiber waveguide is normally cylindrical in form. It confines electromagnetic energy
in the form of light to within its surfaces and guides the light in a direction parallel
to its axis. The transmission properties of an optical waveguide are dictated by its
structural characteristics, which have a major effect in determining how an optical
signal is affected as it propagates along the fiber. The structure basically establishes
the information-carrying capacity of the fiber and also influences the response of the
waveguide to different kinds of environmental perturbations.
The propagation of light along a waveguide can be described in terms of a set
of guided electromagnetic waves called the modes of the waveguide. These guided
modes are referred to as the bound or trapped modes of the waveguide. Each guided
mode is a pattern of electric and magnetic field distributions that is repeated along
the fiber at equal intervals. Only a certain discrete number of modes are capable
of propagating along the guide. These modes are those electromagnetic waves that
satisfy the homogeneous wave equation in the fiber and the electromagnetic field
boundary conditions at the core-cladding interface of the waveguide.