CWDM - Cost-Effective Alternative to Expand Network Capacity

Updated on Jul 23, 2021 by

Fiber optic cabling is highly favorable in the telecommunication world. However, deploying fiber cabling for each individual service can be cost prohibitive, thus Wavelength Division Multiplexing (WDM) technology shines out as an optimal choice - it combines multiple signals onto a single fiber strand by using several wavelengths (frequencies) of light - each frequency carrying a different type of data, enabling cost-efficient upgrade of network capacity. WDM has two variations: Coarse WDM (CWDM) and Dense WDM (DWDM), in which CWDM is well suited to the needs of enterprise networks and metropolitan short-distance transmission.


CWDM Technology - Alternative for Increasing Transmission Capacity

CWDM was standardized by the ITU-T G.694.2 based on a grid or wavelength separation of 20 nm in the range of 1270-1610 nm. It can carry up to 18 CWDM wavelengths over one pair of fibers. Each signal is assigned to a different wavelength of light. Each wavelength does not affect another wavelength, so the signals do not interfere. Each channel is usually transparent to the speed and type of data, so any mix of SAN, WAN, Voice, and Video services can be transported simultaneously over a single fiber or fiber pair.


Figure 1: CWDM System

CWDM is a cost-effective solution to provide a capacity boost in the access network. It can address traffic growth demands without overbuilding the infrastructure. For example, a typical 8-channel CWDM system offers 8 times the amount of bandwidth that can be achieved using a SONET/SDH system for a given transmission line speed with the same optical fibers. It is a perfect alternative for carriers looking to increase the capacity of their installed optical network without replacing existing equipment with higher bit rate transmission equipment, and without installing new fibers.

Key CWDM Network Component: CWDM Mux Demux

A Mux is commonly known as a multiplexer which combines multiple wavelength channels on a single fiber, and a Demux separates them again at the other end. A Mux/Demux set-up is especially useful to increase the end-to-end capacity of deployed fiber. The Mux is typically located in the central office, and the Demux unit is located in either a cabinet or splice closure from which the fibers go to their destination in a star-shaped topology. CWDM Mux Demux provides a cost-effective and efficient way to meet bandwidth requirements in different network scenarios.


Figure 2: CWDM Mux Demux

Dual-Fiber CWDM Mux Demux VS. Single-Fiber CWDM Mux Demux

CWDM Mux Demux types are divided into Single-fiber CWDM Mux Demux and Dual-Fiber CWDM Mux Demux. Dual-fiber CWDM Mux Demux enables up to 18 channels for transmitting and receiving 18 kinds of signals, with wavelengths from 1270 nm to 1610 nm. The CWDM transceiver inserted into the fiber optic Mux port should have the same wavelength as the Mux port to finish the signal transmission. Single-fiber CWDM Mux Demux should also be used in pairs. Considering that the single-fiber CWDM Mux Demux transmits and receives the integrated signals through the same fiber, the wavelengths for RX and TX of the same port on the single-fiber CWDM Mux Demux should be different. The working principle of single-fiber CWDM Mux Demux is more complicated, compared to the dual-fiber one.