In a typical passive optical network, one PON port is connected to 128 clients through the use of PLC splitters - unlike a WDM splitter which will insert or remove a specific wavelength, these simply split the whole signal. Where I work, that is a 4-4-8 configuration using 3 layers of splitters.
The OLT (optical line terminal, head-end) will tell each ONU/ONT (optical network unit/terminal) how much airtime they can use to transmit - each ONT will take their turn in transmitting so as not to interrupt others. Part of this calculation is the distance the ONT is from the OLT - each ONT will be a different distance depending on the geographic location, which means each ONT will have a different latency. The ONU can request additional airtime if it has a large amound of data to transmit. The amount of airtime the OLT will allocate depends upon the CIR (committed information rate i.e. what will the ISP guarantee at a minimum) and the PIR (peak information rate - the maximum rate based on the subscribers service).
The OLT (optical line terminal, head-end) will tell each ONU/ONT (optical network unit/terminal) how much airtime they can use to transmit - each ONT will take their turn in transmitting so as not to interrupt others. Part of this calculation is the distance the ONT is from the OLT - each ONT will be a different distance depending on the geographic location, which means each ONT will have a different latency. The ONU can request additional airtime if it has a large amound of data to transmit. The amount of airtime the OLT will allocate depends upon the CIR (committed information rate i.e. what will the ISP guarantee at a minimum) and the PIR (peak information rate - the maximum rate based on the subscribers service).