Optical channel capacity  From Mb/s to Tb/s and beyond
The history of optical channel capacity growth, from Mb/s to Tb/s and beyond, is reviewed. By considering only one polarization various types of optical channels can be categorized into three basic designs: Single Carrier Single Modulation-path (SCSM), e.g. a single carrier ETDM channel; Single Carrier Multiple Modulation-paths (SCMM), e.g. an OTDM channel; and Multiple Carrier Multiple Modulation-paths (MCMM), e.g. a superchannel. Techniques, such as polarization multiplexing (PM) and multi-level modulations, can be applied to the basic channel designs. The single carrier ETDM channel design has successfully supported all commercially available optical transport systems with channel capacity up to 100Gb/s, which is the highest channel capacity deployable in current fiber networks. Commercial optical channel designs for channel capacity beyond 100Gb/s, however, may experience a paradigm change from the single carrier ETDM channel to the multi-carrier superchannel based on the analysis in this paper.
optical channel etdm otdm superchannel optical fiber communications