LBVM900 Series 1 GHz Indoor High Output Optical Node
Installation & Operation Manual
Page 3 of 4
OPTICAL, RF & POWER CONNECTIONS CONT'D.
FORWARD & REVERSE SETUP GUIDELINES
1.
Please note that LBVM900 uses JXP attenuator pads for output/input level control (forward/reverse pad) and 1 GHz JXP type equalizer for forward
equalizer plug-in.
2.
For the forward path setup, make sure that the forward optical input level to the LBVM900 is within range as shown in the table in section OPTICAL, RF & POWER
CONNECTIONS above. If the optical input is higher than +2 dBm, receiver overload may occur. If the optical input is < -6 dBm, the LBVM900 will deliver very
low RF output. The LBVM900 does not have AGC (Automatic Gain Control), and the RF output depends on the optical input to the ONU. The LBVM900 delivers
optimum performance at -1 dBm optical input level.
3.
The specified RF output level of 50 dBmV at 1 GHz is only guaranteed at -1 dBm optical input and with OMI ≥ 3.5% on the downstream optical signal. The output
will drop a further 2 dB with every 1 dB drop in optical input.
4.
To compensate for RF cable losses, the forward equalizer plug-in comes with a 15 dB JXP equalizer installed from the factory. This results in a 15 ± 1 dB slope on
the RF output of LBVM900 from low frequency to high frequency. The forward slope (tilt) can be changed by changing the forward equalizer plug-in value. Use only
1 GHz JXP equalizers in the forward equalizer plug-in.
5.
Connect a signal level meter at the RF OUT port to measure the RF output from the LBVM900. You can also use the forward output -20 dB TP to measure the RF
output.
6.
If the output level is too high or low, the forward pad plug-in can be changed to adjust the output of LBVM900. The forward pad plug-in takes a JXP attenuator pad.
7.
Verify the RF output levels from the LBVM900 are as expected.
8.
This completes the forward path setup for the LBVM900 ONU.
9.
The LBVM900 is also available in a downstream only model. If using a receive only LBVM900 node, then ignore the reverse (upstream) path setup.
10.
For the reverse path setup, make sure that the reverse input level to the LBVM900 is not too high or damage to the ONU may occur. The -20 dB forward TP is a
bi-directional TP and can also be used to inject the upstream test carrier. Compensate 20 dB if using the forward TP to inject the upstream test carrier. The injected
upstream test carrier can be measured on the -20 dB reverse input TP of the LBVM900.
11.
The upstream transmitter in the LBVM900 is a continuous ON laser transmitter and is always active. The LASER ON LED on the laser diode indicates the status of
the laser transmitter and will be illuminated when the LBVM900 turns ON (irrespective of upstream RF input).
12.
Make sure the upstream RF input is within the upstream frequency and input level range. The upstream RF input range for LBVM900 is 10-30 dBmV per channel
(digital channel level) for 42/54 MHz LBVM900 and 10-27 dBmV per channel (digital channel level) for 85/102 MHz LBVM900. These upstream levels are assumed
with the condition that a 42/54 MHz split unit will have 4 equally loaded channels in the upstream band, and the 85/102 MHz split will have 8 equally loaded
channels in the upstream band. If using a different number of channels from what is mentioned above, compensate for total RF power. The total RF input level to the
LBVM900 (for all channels combined) should not exceed more than 36 dBmV (digital channel level). More than 36 dBmV (digital channel level) total upstream RF
input may cause laser clipping and saturation on the LBVM900. Use the following formula to calculate total RF power: Total RF power = RF power per c
[10* log (# of channels)].
13.
Refer to the NPR plot below to better understand the RF input levels to the LBVM900.
14.
For optimum performance in the upstream direction, make sure the LBVM900 is operated with RF input levels to the left side of the NPR peak. Operating at RF
input levels to the left side of the NPR peak will provide the best MER/BER performance while assuring the laser saturation and clipping does not occur on the laser
transmitter.
15.
This completes the reverse path setup for the LBVM900 ONU.
16.
If you have any more questions regarding the LBVM900 setup, please contact Lindsay Broadband for support.
NOTE: The RF levels mentioned in this manual are analog channel levels, unless specified. For digital channels assume 6 dB less to that of
analog channels.
13.
The F-port labeled "RF" is the bi-directional RF input and output port for the LBVM900 optical node.
14.
There are separate forward output and reverse input -20 dB TPs labeled “FWD TP” and “REV TP” respectively. When not in use, please terminate these -20 dB
TPs with a 75 ohm terminator.
15.
When using the -20 dB TP to measure the RF input/output levels, make sure the RF port is terminated to 75 ohm. Please note the levels from -20 dB TP will be 20
dB lower than the RF port.
