ZyXEL
OLT-2300 Series Support Notes
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2006 ZyXEL Communications Corporation.
33
How do I design my PON network from the power budget?
In order to make PON network work properly, we need to be sure the received
power of transceiver is within the overload and max sensitivity specification of the
transceiver. We can follow the below procedures to calculate,
1. Calculating the fiber loss
The first step is we need to know the fiber loss. Typically, the fiber loss is
0.25dB/km at 1550nm/1490nm and 0.35dB/km at 1310nm. If we have a 10Km
fiber the fiber loss will be 2.5dB at 1550nm/1490nm and 3.5dB at 1310nm.
Because the downstream (1550nm/1490nm) and upstream(1310nm)
transmission is on the same single fiber, so here we get it by 3.5dB.
2. Calculating the fiber connector loss
Single-mode connectors which are factory made and fiber fusion splice will have
losses of 0.1~0.2 dB. Field terminated single-mode connectors may have losses
as high as 0.5~1.0 dB. Let's use the typical value 0.3 dB.
3. Splice loss
The typical value of splice loss is around 0.1~0.5 dB. We can use the average
value 0.3 dB for this application note.
4. Splitter loss
Below is the splitter loss table for different splitter.
1:2 splitting loss in a 1:2 optical splitter
3.6 dB(max)
1:4 splitting loss in a 1:4 optical splitter
7.4 dB(max)
1:8 splitting loss in a 1:8 optical splitter
10.5 dB(max)
1:16 splitting loss in a 1:16 optical splitter
14 dB(max)
1:32 splitting loss in a 1:32 optical splitter
17.5 dB(max)
5. Total loss
When calculate the total loss, we can add above loss and get the total loss. For
example, we have a 10km fiber, 5 connectors, one splice and a 1:8 splitter, the
total loss will be:
10km*0.35+5*0.3+1*0.3+1x10.5=15.8 dB.
Lab environment example
The ONU and OLT transmitter output power must be appropriately attenuated, so
the optical signal power at the OLT and ONU receiver accordingly will be within
the dynamic range(between overload and sensitivity) as defined.
In this example, we have one ONU-634HA-11(1000BASE-PX10-U compliance),
OLT-1308(1000BASE-PX20-D compliance). A 5km single-mode, one 1:2 splitter
and 4 connectors are used to connect OLT and ONU
.
