Hello Rajguru m Mohan,
I would like to mention that The main challenges of implementing NG-PON2 (TWDM PON) are the spectrum allocation and the need for “colourless” ONTs, which must be able to send and receive signals on any of the specified wavelengths. The ONT transmitter must be tunable while the receiver requires a tunable filter. Colourless ONTs based on tunable transmitters and receivers are likely to be more expensive than GPON ONTs. Optical component vendors are developing new technologies to help bring down costs. The use of photonic integrated circuits (PICs) in the ONT is highly attractive because a low-cost manufacturing process would enable mass deployment. Furthermore, since tuning technologies mainly rely on temperature control, a key challenge is to maintain low power consumption in the ONT.
Therefore, colourless” ONTs have importance with reference to selection of the the transceiver section of the Optical Line Terminal Units (OLT) and Optical Network Terminals (ONUs) in TWDM-PON.
Hope this is helpful.