From
Xmultiple Engineering Dept.

**Insertion
Loss **

In
the electronic field, insertion loss is the loss of signal
power resulting from the insertion of a device in a transmission
line. This can also be an optical fiber cable. Insertion
Loss is expressed as a ratio in dB relative to the transmitted
signal power. Insertion Loss can alos be referred to as
attenuation. To calculate insertion loss, If the power
transmitted by the source is PT and the power received
by the load is PR, then the insertion loss in dB is given
by:

In
metallic conductor systems, radiation losses, resistive
losses in the conductor as well as losses in the surrounding
dielectric all reduce the power. Line terminations play
an important part in insertion loss because they reflect
some of the power. All of these effects can be conceptually
modelled as various elements which make up the equivalent
circuit of the line In an optical fiber system, insertion
loss is introduced by things such as connectors, splices,
and couplers.

For
our analysis related to connectors, insertion loss is
typically the effect on a signal as it runs from a PCB
into a connector. Insertion loss is often due to a difference
of impedance, or impedance mismatch, from PCB to connector.
Testing
for inserstion loss can be made by analyzing a signal
as it passes through a connector system. Most designers
target a -3 dB insertion loss as the critical value
of connector performance.