HP 70000 series - C Fiber-Optic Connections

C
Fiber-Optic Connections
This section contains information about how to make good ber-optic connections, how to
make dry and wet connections, and how to clean your connectors.
The Importance of a Good Connection
Fiber-optic connectors are used to connect two ber-optic cable ends together.For example,
ber-optic connectors join cables between optical ports on devices, laser sources, receivers,
patch panels, terminals, and many other types of systems or components. Fiber-optic
connectors are designed to provide a direct and low-loss optical signal transition from one ber
end to another.
In a ber-optic system, light is transmitted through an extremely small ber core. Because ber
cores
are
often
9
microns
(0.009
mm)
or
less
in
diameter
,
and
dust
particles
range
from tenths
of a micron to several microns in diameter, any contamination on the end of the ber core
can
degrade
the
performance
of
the
ber-optic
connection.
Therefore
,
the
connector
must
be
aligned
precisely
and
the
connector
interface
must
be
free
of
contamination
to
make
a
good
connection.
Characterizing a Connection
The
quality
of a connection can be characterized by connector loss and return loss. Connector
(or insertion) loss is one important performance characteristic of a ber-optic connector.
Typical values are less than 1 dB of loss, and sometimes as little as 0.1 dB of loss with high
performance connectors. Return loss is another important factor. It is a measure of reection
of the source (the less reection the better). A good, physically contacting connector can have
a return loss of 40 dB, although 20 to 30 dB is more common.
Causes of connector and return loss include:
Dierences in the numerical aperture of the two bers
Core misalignment
Spacing and air gaps
Damaged, worn, or loose ber ends
Contamination on the end face of the connector
Improper use and removal of index-matching compounds
Numerical aperture dierences are not connector related, but the remaining problems are
connector related and can be prevented by proper care and maintenance of connectors.
Fiber-Optic Connections C-1