There are different types of losses are involved in the FTTx network when we design the network. each loss is very important to understand otherwise your link loss budget calculation will be wrong and ultimately you will come up with the wrong optical power in your network.
The most important factor in designing a GPON network. First, we need to become familiar with sources of attenuation so that we can use them in designing the network and calculating the optical power level (dBm). For example, The B+ module starts with an output power of +3 dBm, while supporting an Rx minimum loss of -8 dBm and a maximum loss up to -28 dBm. All of the signals must be within this range.
As you can see below in my image, My OLT is alerting me few of your ONu power are exceeding the range.
These are general attenuation values and different vendors may lead to different values depending on the quality of the product. Each source of attenuation will decrease the starting power level to be within the acceptable range for the ONUs.
There are several types of losses we have in FTTx .
- Length of Fiber:- Fiber losses occur based on the distance of fiber, This is a standard loss which usually has a loss in downstream (~0.35 dB per Km on 1490 nm) and upstream (~0.5 dB per Km on 1310 nm) frequencies.
- Splices:- Each splice in a fiber optic run accounts for ~0.2 dB. This seems minimal at first, however, the count of splices in a single run can add up considerably.
- Connectors:- Each connector accounts for a ~0.75 dB loss. This starts from the SC connector at the B+ module and ~0.75 dB is added to each other connector.
- Splitter Loss:- Splitters are essential in a GPON network to connect multiple ONUs to a single PON port.
- SFP Insertion Loss:- There should not be any loss when you are inserting the SFP into PON port. Find the image given below where I have an insertion loss of 0.5 dBm or above .
Note:- The power must be between -6 to -27 dBm from OLT to ONU.