Wavelength Division Multiplexing Architecture

WDM systems use multiplexers, demultiplexers, and optical fibers to transmit multiple data streams simultaneously over a single fiber, each on a distinct wavelength. Core Components of WDM1. Multiplexer (MUX): At the transmitter, a multiplexer combines multiple optical signals, each at a different wavelength, into a single optical fiber.

This allows multiple data streams to travel simultaneously without interference, effectively increasing the fiber's capacity. 2. Demultiplexer (DEMUX): At the receiver, a demultiplexer separates the combined wavelengths back into individual signals, which are then processed by optical receivers to recover the original data.

3. Optical Fiber: The fiber carries all wavelengths together. Depending on the system, standard single-mode fibers (ITU G.

652) are used for access networks, while low-dispersion fibers (ITU G. 655) are preferred for long-haul DWDM systems to reduce signal degradation and nonlinearity. 4.

Optical Amplifiers: Devices like Erbium-Doped Fiber Amplifiers (EDFAs) boost signal strength to overcome losses over long distances, ensuring reliable transmission. 5.

Optional Add-

Drop Multiplexers: These allow selective insertion or removal of specific wavelengths along the fiber path, enabling flexible network configurations without disrupting other channels. Types of WDM1.

Coarse WD

M (CWDM): Uses wider channel spacing (typically 20 nm) to reduce cost and complexity.

CWD

M supports fewer channels (up to 16) and is suitable for metro networks or short-distance applications. 2.

Dense WD

M (DWDM): Uses narrow channel spacing (50–100 GHz) to support many channels (40–96 or more) over long distances.

DWD

M operates mainly in the C-band (1530–1565 nm) and L-band (1565–1625 nm) and often requires dispersion-compensating fibers and optical amplifiers for high-speed, long-haul transmission. Transmission Modes1.

Dual-

Fiber Unidirectional: Each fiber carries signals in one direction, with different wavelengths multiplexed together. Demultiplexing occurs at the receiving end. 2.

Single-

Fiber Bidirectional: Also called wavelength-division duplexing, this allows bidirectional communication on a single fiber by assigning separate wavelengths for each direction.

Summary

The basic structure of a WDM system consists of multiplexers, demultiplexers, optical fibers, and amplifiers, with optional add-drop functionality.

CWDM and DWD

M differ mainly in channel spacing and capacity, while transmission can be unidirectional or bidirectional. This architecture enables efficient use of fiber infrastructure, supporting high-capacity data transmission without laying additional fibers.