Atec Agilent-81618A - Manual (Page 12)

Getting Started with Optical Heads What is an Optical Head?
12
Agilent 81618A/9A and Agilent 81622B/3B/4B/6B/7B/8B User’s Guide, Second Edition
Analog Output
The analog output is the BNC connector on the back of the optical
head. It outputs a voltage directly proportional to the strength of the
optical signal at the optical input in the current range. The analog
signal is always in the range between 0 and 2V, 2V corresponding to a
full power input signal in the current range, 0V corresponding to no
input signal.
During autoranging, the level to which 2V corresponds changes. You
should disable autoranging when using the analog output.
Disabling Autoranging Select the best range for the application using the mainframes user
interface. Select
from the list of ranges.
Applications Possible applications for the analog output are:
• to close the feedback loop controlling the current supplied to a laser
• to aid positioning the system for fiber alignment tasks
• to monitor optical power on an oscilloscope
The analog signal reacts instantaneously to the input signal, whereas
the power shown on the display is subject to averaging.
Optical input
The optical input to the optical head requires a connector adapter to
match the connector type (or bare fiber) to the optical head interface.
The optical head interface can be either threaded or a D-type magnetic
interface depending on the model of optical head (e.g. the 81627B is
only available with a D-type interface, and the 81628B is only available
with a threaded interface). See “Accessories” on page 15 for details of
the connector adapters available.
When a connector adapter is fitted it should be locked in place by
tightening the locking screws located either side of the main optical
head housing.
Heat Sink for 81628B optical Head
The 81628B optical head has a heat sink that allows an extended
operating power range. This heat sink must be mounted on the
integrating sphere for operation from 34dBm to 38 dBm.