Additional Features; Rf Section - Motorola GX2 EA1000C Series User Manual

Overview

Additional Features

Functions performed by the GX2-EA1000C*/* include:
•
Provides local alarm indication by changing the color of the front-panel
•
Stores module identity, laser operating parameters, and set-up information in NVM
•
Downloadable firmware to support field upgrades
•
Factory birth certificate stored in NVM and accessible through local interfaces

RF Section

The RF input signals are applied to the GX2-HSG* equipment-shelf rear panel. The upper
connector is the main-broadcast input and the lower connector is provided for
narrowcast. The narrowcast input is a convenient method of adding channels to serve
select areas of the cable plant. The narrowcast input must be terminated in 75 ohms
when not in use. Both inputs provide full bandwidth. Gain through the narrowcast input
is -6 dB relative to the main input.
The RF input test point is located on the common path after the main and narrowcast
inputs are combined. This enables verification of the input signals.
Low noise, low distortion gain stages amplify the input signal to the optimum drive level
required for the laser. A programmable attenuator, located midway in the amplifier chain,
is controlled by the microprocessor and, in turn, controls the drive level.
A sample of the RF level is detected after the final gain stage. The output of the RF level
detector is a DC voltage level that corresponds to the total signal power applied to the
laser. There is also a pre-distortion circuit and some equalization in the RF path to help
with distortion levels and signal response.
When in Preset mode, the microprocessor references laser characteristics stored in the
NVM and adjusts the attenuator to apply the optimum RF level to the laser. The power
meter is constantly monitored and the attenuator is adjusted to maintain a constant drive
level into the laser.
Other AGC modes operate in a similar manner but use different laser drive level
reference points, as set by the user. These are described in the previous subsection,
"Operating Modes."
GX2 EA1000C*/* Multi-Wavelength DWDM 1550 nm Laser Transmitter • User Guide
589569-001-a
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