A Broadband Scalable Hierarchical PON for Cost-efficient Fiber Access Networks

The traffic flow in long-haul dense wavelength division multiplexing fiber networks has surpassed by far the traffic deliverability from/to the access network thus creating what is known as “access bottleneck”. This bottleneck was the result of two major factors, the inherent cost sensitivity of access networks that impedes deployment of new optical technology prior to cost maturity, and the lack of popularized new broadband services that would demand from the access network bandwidth higher than broadband that digital subscriber lines or cable could deliver. Nevertheless, the bandwidth landscape at the access is changing and it has been widely recognized that optical is the technology that can efficiently address the current and future bandwidth needs of the access network. In order to also meet low-cost objectives, it has been recognized that the optical technology should be mostly limited to passive culminating to a passive optical access network (PON). To date, two passive optical network proposals have prevailed. The time division multiplexing passive optical network (TDM-PON) uses a single optical channel and a complex timing protocol. The coarse wavelength division multiplexing PON (CWDM-PON) uses multiple optical channels with a complex wavelength management procedure. In this paper we describe the hierarchical CWDM/TDM-PON (hCTPON). We show that the hCT-PON is scalable, , and it delivers synchronous and asynchronous bandwidth flexible from as low as DS0 to as high as Gbps. In addition, we show that the hCT-PON can serve more than 16,000 end-users thus reducing the cost per user.