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ZyXEL
OLT-2300 Series Support Notes
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2006 ZyXEL Communications Corporation.
34
The network topology for this example is:
1. Check if RX optical power in OLT is within OLT transceiver’s dynamic range
We will base on the OLT’s receiver dynamic rage, the OLT receiver dynamic
range is -6dBm ~ -29dBm. We can calculate the total loss by above formula:
Total loss: 5*0.35+1*3.6+4*0.3=6.55dB.
According to 1000BASE-PX10-U, the ONU max output power is +4dbm and the
total loss is 6.55 dB, OLT RX power will be:
OLT Rx power (max): +4 - 6.65 = -2.65dBm
The result shows the signal power at the OLT receiver will be -2.65dBm and it
exceeds the OLT receiver dynamic range (-6~-29dbm) with 3.35dbm (-2.65-(-6)).
Therefore, at least 3.35dbm attenuation is needed for OLT Rx
2. Check if RX optical power in ONU is within ONU transceiver’s dynamic range.
The dynamic range of ONU is -3dBm ~ -26dBm, and according to
1000BASE-PX20-D the output power at the OLT side is 3dBm and the total loss is
6.55 dB, ONU Rx power will be:
ONU Rx power (max): +3 - 6.65 = -3.65dBm
The result shows the signal power at the ONU receiver will be -3.65dBm and it is
within the dynamic range of ONU transceiver. There is no need to add the
attenuations for ONU Rx.
Field site environment example
When design a PON system, we will need to consider the fiber reach based on
the power budget. In this example, we will take the 1:32 network topology to
calculate the allowed fiber reach. The network topology is like the below figure.
1:2
ONU-634HA-11
OLT-1308
Connector
Connector
Connector
Connector