Technology and system issues for the WDM-based fiber loop architecture

A fiber-optic subscriber loop architecture employing multichannel wavelength-division multiplexing (WDM) techniques is discussed. The architecture, which is called the passive photonic loop (PPL), eliminates the need for outside-plant multiplexing and routing electronics while maintaining complete compatibility with broadband ISDN. An experimental demonstration of the PPL employing 32-channel WDM and a combination of distributed-feedback (DFB) laser and light emitting diode (LED) transmitters is described. A family of alternative PPL implementations is identified. Tradeoffs between these alternatives are explored, and related hardware issues such as wavelength alignment and WDM-component temperature sensitivity are discussed. An economic analysis comparing the PPL with the use of dedicated fiber between the central office and customer premises is presented. The analysis predicts that the PPL can achieve a cost advantage for at least 80 to 90% of the subscribers served in today´s network, given DFB-laser and dense-WDM-component cost reductions of approximately one order of magnitude from today´s unit-quantity prices