Topics: Wavelength-division multiplexing, Multiplexing, Synchronous optical networking Pages: 3 (1018 words) Published: September 29, 2006
Dense wavelength division multiplexing (DWDM) is a technology that puts data from different sources together on an optical fiber, with each signal carried at the same time on its own separate light wavelength. Using DWDM, up to 80 (and theoretically more) separate wavelengths or channels of data can be multiplexed into a light stream transmitted on a single optical fiber. Each channel carries a time division multiplexed (TDM) signal. In a system with each channel carrying 2.5 Gbps (billion bits per second), up to 200 billion bits can be delivered a second by the optical fiber. DWDM is also sometimes called wave division multiplexing (WDM). Since each channel is demultiplexed at the end of the transmission back into the original source, different data formats being transmitted at different data rates can be transmitted together. Specifically, Internet (IP) data, Synchronous Optical Network data (SONET), and asynchronous transfer mode (ATM) data can all be traveling at the same time within the optical fiber.

Multiplexing, by definition, is the process where multiple channels are combined for transmission over a common transmission path. In the early 1990s, fiber could only carry one wavelength, or color, of light at a time. Lasers were used by quickly turning them on and off. By the mid 1990s wave division multiplexing could split the light into two colors. The number of colors rapidly grew and today as many as 160 colors can be carved out by using the most advanced systems, in what is now called dense wave division multiplexing (DWDM). In other words, DWDM combines multiple optical signals so that they can be amplified and transported over a single fiber. An example would be a DWDM network with a mix of SONET signals operating at OC-48 (2.5 Gbps) and OC-192 (10 Gbps) over a DWDM infrastructure can achieve capabilities of over 40Gbps. The reliability of the system is maintained throughout this process. DWDM networks are self-regulated at the bit-rate and...
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