This article is presented by:
H. Erkan, ASM D.
Hossain, R. Dorsinville,
M.A.Ali A. Hadjiantonis
Abstract
This work proposes a simple and cost effective local access WDM-PON architecture that combines the salient features of both traditional static WDM-PON (i.e., dedicated connectivity to all subscribers with bit rate and protocol transparencies, guaranteed QoS, and increased security) and dynamic WDM-PON (i.e., efficiently utilizing network resources via dynamic wavelength allocation/sharing among end-users). Specifically, this paper proposes and devises a novel ring-based local access WDM-PON architecture that efficiently supports dynamic allocation of wavelengths/timeslots and sharing traffic as well as a truly shared LAN capability among PON end-users.
INTRODUCTION
Passive Optical Network (PON) technology is emerging as a viable solution for next-generation broadband access networks [1-5]. A PON connects a group of Optical Network Units (ONUs) located at the subscriber premises to an Optical Line Terminal (OLT) located at the service provider’s central office (CO). Among the various PON schemes, single channel Time-Division Multiplexed PON (TDM-PON) and multi-channel Wavelength-Division Multiplexed PON (WDM-PON) architectures are the two most viable candidates. TDM-PON supports a single wavelength channel in the downstream direction (OLT to ONUs) and another wavelength in the upstream direction (ONUs to OLT). WDM-PONs are emerging as the most promising future access solutions that can provide evolutionary upgrade to existing TDM-PONs. These schemes can support multiple wavelengths in either or both the upstream and downstream directions. In traditional WDM-PON, each subscriber (ONU) is assigned a separate pair of dedicated upstream and downstream wavelength channels. In addition to its operational simplicity, this approach provides dedicated point-to-point optical connectivity to each subscriber with bit rate and protocol transparencies, guaranteed QoS, and increased security. Despite these aforementioned numerous crucial advantages, typical static WDM-PON architectures suffer from several limitations including inability to efficiently utilize network resources and to cope with the dynamic and bursty traffic patterns of the emerging integrated triple play services [5-6]. The former limitation is exacerbated when some wavelength channels are heavily loaded while others are underutilized or are totally idle. In this case, unused dedicated channel capacities of those lightly loaded/idle subscribers cannot be shared by any of the other heavily loaded users attached to the PON, leading to the waste of scarce network resources. Therefore, to increase the total throughput, future WDM-PON architectures must support dynamic bandwidth allocation (DBA) and sharing. To address these problems, several WDM-PON architectures and protocols that dynamically manage and allocate bandwidth in both time and wavelength dimensions have been proposed recently [6-10]. Most of these schemes, however, are costly and assume complex OLT and ONU setups which require tunable, or arrays of fixed transceivers or both, WDM filters, and wavelength-band-selective receivers. Furthermore, schemes that support dynamic wavelength sharing [6-7], where additional wavelength channels are added to accommodate the fraction of bursty downstream traffic that may exceed the user’s dedicated downstream wavelength channel rate, are still falling short of addressing the fundamental problem of the inefficient utilization of network resources. This is because the unused capacities of those lightly loaded/idle dedicated downstream wavelength channels are still being wasted.
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