Upgrading and extending PON by using in-band WDM overlay

this paper presents a new approach to upgrade and extend the reach of the current passive optical network (pon) by using wavelength division multiplexing (wdm) in the standardized optical grid of gigabit pon (in-band wdm pon overlay). the aim is to increase the number of optical distribution networks (odns) fed by a single fiber while preserving the users bandwidth. in this approach four downstream (ds) wavelength signals are transmitted from an optical line terminal (olt) to four different odns using the standard ds pon spectrum ranging from 1480 to 1500 nm. the upstream (us) signals from the four different odns are also wavelength multiplexed within the standardized us pon spectrum ranging from 1270 to 1330 nm. experimental proofs of concept are presented in a 20 km pon serving 32 onts and in a 58 km extended pon in order to demonstrate the feasibility of this proposal.