Wavelength division multiplexing method
with a very small channel spacing (typically: 0.8 nm).

Distributed feedback laser

Laser diode with a spectral full width at half maximum
of <<1 nm, by which very specific light wavelengths
can be reflected by means of a series of undulating
bumps on the semiconductor surface but with just one
single resonance wavelength being amplified.

Optical filter which only allows a small wavelength
range to pass through and all other wavelengths are
reflected.

The reversal of effects causing pulse spreading,
e.g. chromatic dispersion or polarisation-mode
dispersion.

Measure of the spectral properties of a transmitter.
Permits the dispersion-limited length to be determined,
provided the coefficient of chromatic dispersion
of the fiber is known.

Special fiber that can compensate for any dispersion
that occurs, e.g. with a large negative coefficient
of chromatic dispersion.

Singlemode fiber with a shifted zero-crossing point
of the coefficient of chromatic dispersion
(as per ITU-T G.653). This fiber has minimum chromatic
dispersion as well as minimum attenuation at
1550 nm.

Material with which the refractive index can be
changed.

Intentionally adding small quantities of a different
substance to a pure substance in order to alter its
properties. For example, the increased refractive
index of a fiber core is achieved by doping the basic
substance (silicon dioxide) with germanium dioxide.

Sequence of layers in an optoelectronic semiconductor
component, in which the active semiconductor
coating is sandwiched by two jacket layers with
a larger band gap. With laser diodes, the double
heterostructure confines the charge carriers and
creates a fiber in the active zone.