User`s guide

Getting Started with Return Loss What is Return Loss?
16 Agilent 81610A/11A/12A/13A/14A Return Loss Module, Fifth Edition
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:
Return loss can be measured in several ways. A typical setup using the
Agilent 81610A Return Loss module, where the DUT is a connector
pair, is described in Figure 6.
Figure 6 Return Loss Equipment
5HWXUQ /RV V G%() 10 5HIOH FWLRQ )DFWRU() G%()log–=
5HWXUQ /RVV G%() 10
5HIOH FWHG 3RZ HU
,QFLGHQW 3RZHU
---------------------------------------------
G%()log–=
or
M
dut
P
dut
Termination
Knot
DUT
External Laser
Source
patchcord
physical contact
Agilent 81113PC