Cisco GainMaker Optoelectronic Node 1GHz with 65 86 MHz Split Installation Guide
Chapter 3 Balancing and Setup
The reverse optical transmitter in the node
The reverse optical receiver in the headend or hub
The fiber optic cable that transports the optical signal from the reverse
transmitter output to the reverse receiver input
For the purpose of this document, balancing refers to the process of adjusting the RF
gain of the reverse optic link to achieve optimum, repeatable transmission
characteristics.
There are a variety of test equipment combinations that enable proper balancing of
There are a variety of test equipment combinations that enable proper balancing of
the reverse path. Regardless of the type of equipment used, the balancing process is
fundamentally the same.
Injection of Test Signal(s)
During the balancing process, a reverse RF test signal or signals of known amplitude
During the balancing process, a reverse RF test signal or signals of known amplitude
are injected into the RF input path of the node, prior to the reverse amplifier and
reverse transmitter. The injected signals are amplified and routed to the reverse
optical transmitter in the station.
The reverse transmitter converts the RF test signal to an optical signal and transmits
The reverse transmitter converts the RF test signal to an optical signal and transmits
it to the headend or hub via fiber optic cable. At the headend, the reverse optical
receiver converts the optical signal back to an RF signal that is routed out through
the receiver RF output.
Monitoring and Adjusting Received Amplitude
The received test signal is monitored at a headend or hub test point on the output of
The received test signal is monitored at a headend or hub test point on the output of
the reverse optical receiver associated with the particular node. The amplitude of the
received test signal is compared to the desired “reference value" amplitude. Any
deviation from reference value amplitude is then minimized by adjusting the RF
level at the receiver output. This is typically accomplished either via adjustment of
an RF output level control on the optical receiver, or through the use of external
attenuation at the RF output of the optical receiver.
Methods of Generating and Monitoring Test Signals
The reverse RF test signals to be injected into the reverse fiber link node may be
The reverse RF test signals to be injected into the reverse fiber link node may be
generated by the following.
Multiple CW signal (tone) generator
Reverse sweep transmitter
The amplitude and tilt of the received test signals at the output of the reverse optical
receiver in the headend or hub may be measured and monitored using the
following.
Spectrum analyzer (when using a CW generator for test signals)
Signal level meter (when using a CW generator for test signals)
Reverse sweep receiver (when using a reverse sweep transmitter for test signal)
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