FTTH Link Budget Calculation and End to End Attenuation

FTTH Link Budget Calculation and End to End Attenuation: I would not like to spread this topic, I will only write the point that will help you in practical life.Some people wander from their topic to prolong their posts and they include unwanted topics. come to the point- In conventional PON based FTTH the minimum transmitter power and minimum receiver sensitivity is set as 0 and -34 dBm.

34dBm power value or power budget for the design architecture.Dynamic range also consider 31dBm with margin of 3dBm. but you should remember that total allowed optical budget from the OLT to the ONT is 28dB. All FTTH design losses from OLT to ONT cannot be bigger than 26,5db (5% margin).

Calculating Link Budget

FTTH Link Budget Calculation and End to End Attenuation

Average Loss Calculation in FTTH Link

Often the engineers are troubled by these thinking that what is splitter loss,how much power should get on the ODB etc.for your convenience I have mentioned details in below table.The following Parameters should be taken into account while calculating the optical losses in the FTTH network.

Optical Losses in Optical Network

Average Losses to Calculate Link Budget

Because of these losses, the maximum average distance that this FTTH-GPON network can reach is about 15 Km with 1:64 splitting ratio (20 km with 1:32). The actual maximum distance depends on the brand and type of FTTH equipment used.

When using splitting lower than 32, the maximum distance limit increases depending on the splitting ratio.All information regarding the PON equipments, materials and cables that shall affect attenuation should be considered and provided by the vendors.

Budget loss calculation = (Fiber cable + Connectors + Splices + Splitter) Losses.

Where: Fiber attenuation = 0.4 dB/Km for (1310 – 1490) nm; and 0.25 dB/Km for 1550 nm.

Connector Loss = 0.35 dB SC/UPC & = 0.25 dB for SC/APC connectors

Fusion Splice Loss = 0.1 dB

Splitter losses = 4 – 20.1 dB, depending on ratio; should be provided by the vendor.

Calculation of Attenuation

Attenuation calculations:

I have used these charts for example but will help you understand that how to calculate the attenuation Commercial PON-based FTTH network systems commonly use the 1x16 or 1x32 splitting ratio.

Summary

The average exact optical power or total system loss is determined by using an optical power meter (for 1310, 1490 and 1550 nm) and OTDR.The two most common tools used for fiber optic cable testing are optical power meter and OTDR. Both can measure attenuation (signal loss) on a fiber optic link.