Dynamic bandwidth and wavelength allocation with coexisting transceiver technology in WDM/TDM PONs

Passive Optical Networks (PONs) are continuously evolving. One important requirement of these systems is the possibility to smoothly upgrade the network infrastructure as technologies evolve. During the process of network upgrade, a coexistence of new and old end-users, i.e., Optical Network Units (ONU), with diverse transceiver technologies, is expected. In this work, we focus on a scenario where the network is upgraded from a TDM PON to a hybrid WDM/TDM PON (both short-reach and long-reach), and where the transceivers used in the old TDM PON can coexist with the new transceivers adopted in the hybrid WDM/TDM PON. Therefore, we consider that three different types of transceivers can be installed at the ONUs: single fixed tuned lasers, array of fixed tuned lasers, and tunable lasers. In particular, we propose new Dynamic Bandwidth and Wavelength Allocation (DBWA) algorithms which solve the problem of managing the traffic originated by end-users equipped with transceivers with different characteristics. In this paper we focus on the case of transceivers characterized by different tuning times. To investigate the importance of a DBWA able to manage transceivers with different tuning times, we also compare them to DBWAs which are not aware that different transmission technologies coexist in the network. Then, we test these DBWAs in different network scenarios, and discuss what are the network parameters that mostly affect the algorithms performance. After showing the importance of having a DBWA that supports transceivers characterized by different values of TTs, we investigate also the practical case of tunable lasers that have different values of TT depending on the wavelength they have to retune to (i.e., higher distances between two wavelengths require higher TTs). Finally, we evaluate the performance of the previously proposed DBWAs when the arrays of fixed tuned lasers can transmit over a limited number of wavelengths, i.e., the number of lasers of the array is limited.