CoarseWDM

CoarseWDM, short for coarse wavelength-division multiplexing, is a form of wavelength-division multiplexing used in optical fiber networks that carries multiple data streams on separate, widely spaced wavelengths. It aims to simplify hardware and reduce cost by using broader channel spacing and more tolerant filtering than dense WDM approaches. In many contexts, coarseWDM is effectively synonymous with the commonly deployed coarse WDM (CWDM) technology.

Technically, coarseWDM relies on a relatively wide wavelength grid. Typical channel spacings are around 20 nanometers, and standard CWDM wavelengths span roughly from 1271 to 1611 nanometers, allowing up to about 18 channels in a single fiber. The wide spacing relaxes the precision requirements for lasers, filters, and temperature stabilization, enabling the use of simpler, lower-cost transceivers and components. Because of this, coarseWDM is often favored for metro and regional networks where cost and simplicity are prioritized over maximum channel count.

Implementation generally involves point-to-point links or small-mesh topologies using standard optical transceivers compatible with CWDM grids. The approach supports uncooled laser diodes and non-narrowband filters, contributing to lower equipment complexity and maintenance. It is commonly deployed in access and metropolitan networks, where reach is moderate and the emphasis is on economical scalability.

Advantages of coarseWDM include lower capital and operating costs, reduced engineering and maintenance complexity, and greater tolerance to environmental variations. Limitations center on spectral efficiency and capacity: fewer channels are available than in dense WDM systems, and network scalability can be constrained by the fixed channel grid and potential crosstalk if not properly managed. It is most suitable when network size, budget, and simplicity outweigh the need for extremely high throughput.