178 8163A/B, 8164A/B, 8166A/B User’s Guide
7 Return Loss Measurement
Getting Started With Return Loss
What is Return Loss?
When light passes through an optical component most of it travels in the
intended direction, but some light is reflected or scattered. In many
applications these reflections are unwanted, because they can affect the
emission characteristics of any laser in the system. In such applications, it
is important to measure the reflections for the components of the system.
The reflection factor for a component is a measure of how much light the
component reflects. It is a ratio of the power reflected by the device to the
power incident on the device. More normally we talk about the return loss
of a component. The return loss has units of dB. Return loss is given by:
What is Insertion Loss?
Light that is absorbed, scattered, or reflected by a component also affects
how much light a component transmits.
The transmission factor for a component is a measure of how much light
the component transmits. It is a ratio of the power transmitted by the
device to the power incident on the device. More normally we talk about
the Insertion Loss of a component. The insertion loss has units of dB.
Insertion Loss is given by:
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