Broadband Access: Wireline and Wireless - Alternatives for Internet Services

5Optical Domain PON Technologies

5.1 Introduction

Optical domain PON technologies (i.e., PONs whose media access is defined by optical rather than electronic means) are ideal from the standpoint that they can be largely agnostic to the rate and format of the client signals they carry over the PON. For example, a purely optical domain PON could potentially carry each subscriber's UNI signal in its native format (e.g., DS1/DS3, 10/100/1000BASE Ethernet, etc.), allowing simple service upgrades without needing to upgrade other remote ONUs on the same PON. It also allows the highest potential data rates per subscriber. However, the optical domain technologies have been more expensive than TDM technologies, and will probably continue to have a cost disadvantage at least until around the 2015 time frame. Another drawback to all the optical domain technologies relative to TDMA is that they do not allow statistical multiplexing on the PON for more bandwidth efficiency at the OLT PON interface.

An important application for optical domain PON technologies in the meantime is to carry TDMA PON protocols in order to increase the number of ONUs and/or the per-subscriber service rates on a PON. This WDM application was introduced in Chapter 2 and 4 in the discussion of next generation FSAN/ITU PON protocols. This chapter focuses on the optical domain technologies, since their extension to hybrid combinations with TDMA PON is relatively straightforward.

5.2 WDMA (Wavelength Division Multiple ...