Information Storage and Management: Storing, Managing, and Protecting Digital Information in Classic, Virtualized, and Cloud Environments, Second Edition

Appendix E

Network Technologies for Remote Replication

For remote replication over extended distances, various optical network technologies are deployed such as dense wavelength division multiplexing (DWDM), coarse wavelength division multiplexing (CWDM), and synchronous optical network (SONET).

DWDM

Dense wavelength division multiplexing (DWDM) is an optical technology by which different data from different channels are transported at different wavelengths over a fiber-optic link at the same time. This is in contrast with a conventional fibre-optic system in which just one channel is carried over a single wavelength traveling through a single fiber. DWDM is a fiber-optic transmission technique, and several separate wavelengths (or channels) of data can be multiplexed into a multicolored light stream transmitted on a single optical fiber. Using DWDM, different data formats at different data rates can be transmitted together. Specifically, IP, ESCON, FC, SONET, and ATM data can all travel at the same time within the optical fiber (see Figure E-1).

Figure E.1 Dense wavelength division multiplexing (DWDM)

DWDM can multiplex and demultiplex a large amount of channels. Each channel is allocated its own specific wavelength (lambda) band. Each wavelength band is generally separated by 10 nm spacing. As optical technologies improve, separations between each channel may be further reduced ...