User's Manual

Powerwave Fiber Optics
VM100 56/EN – User’s Manual Rev. P1A9-Draft 2004-11 3 - 3
RF Path 2
An optical 1310 or 1550nm input signal is received by an optical receiver. The power
range for this input is between –15dBm and 1dBm optical power. To avoid receiver
saturation, it should be less than 1dBm.
After converting the optical RF modulated signal to an electrical RF modulated signal,
it is amplified in two 16dB amplifier stages with a noise figure of 4dB each.
Between the two 16dB amplifiers there is a software adjustable 0 – 20dB attenuator,
manually set by the operator via O&M software. This attenuator is differently set
depending on the FON usage.
• If the FON unit is part of a BMU, then it is adjusted to an uplink gain that is dependent
on the ratio of the BTS and the repeater coverage areas.
• If the FON unit is part of a FOR, then it should be adjusted to match the repeater input
amplifier power range.
Examples of this are found in Chapter 6, Commissioning.
The RF OUT port (P102) is usually connected to BTS/UL in a BMU, or to the DL
amplifier in a FOR. The output power can be between 0dBm and 20dBm with a
minimum noise (above the thermal noise) of 22dB.
There is also an RF test output (P103) with an output level of 15dB below the RF OUT
level. This output is intended for signal measurement without disconnecting the RF
cable.
IP Path
The IP communication circuitry is located in the control unit.
The subcarrier from the control unit is fed, via a filter, to the RF path before the optical
transmitter, see Figure 3-2. In the connection point, the subcarrier is added to the RF
signal. In the following optical transmitter, the RF signal with the added subcarrier is
converted to an optical signal and transmitted to the connected optical receiver or
receivers.
A received optical RF signal with an added subcarrier is converted to an electrical signal
in the optical receiver. After the first amplifier, the subcarrier passes a filter and is then
fed to the IP circuitry input in the control unit.
The subcarrier signal takes no power from the optical RF transmission.