By Oleh Sniezko , AT&T Broadband & Internet Services
This paper presents several methods of provisioning for frequency reuse in the reverse path. It analyzes several optical technologies existing today or feasible in near future. These technologies range from a traditional 1310 DFB lasers technology through ITU grid 1550 nm lasers to external modulators with distributed access. These transport technologies are augmented by several methods of multiplexing to achieve frequency reuse:
1) spatial division multiplexing (physical segmentation of the reverse plant)
2) wavelength division multiplexing (coarse or dense)
3) frequency division multiplexing (frequency stacking or frequency block conversion), and
4) time division multiplexing (either after digitization of the reverse signals or after demodulation of the reverse signals).
This multiplexing may take place in optical nodes or secondary hubs. Besides allowing for frequency reuse, the multiplexing schemes allow for fewer fibers and make the redundancy switching feasible.
The paper presents architectural implementation of these optical technologies and multiplexing methods. Further, the paper presents the results of the cost analysis for all these methods based on the most up-to-date pricing or estimated cost of the technologies being developed. Finally, the paper provides performance allocation for different segments of the reverse paths for the architectures analyzed, and achievable or projected end-of-line performance of the reverse path.