Expanding Network Capacity with Coarse wavelength division multiplexing (CWDM)

Light Notes

The demands placed on networks by voice, video and data are increasing exponentially. Thus, service providers require more bandwidth and higher transmission speeds. However, deploying fiber cabling for each service is costly.

Transceiver-based solutions add more capacity to networks while avoiding the cost of expensive upgrades. Wavelength Division Multiplexing (WDM) transceivers are compatible with existing network switches. When used in passive networks, they fix network congestion cost-effectively.

Wavelength Division Multiplexing transmits multiple signals through a single fiber pair by modulating different wavelengths (or frequencies) of light. Each frequency carries a separate channel. Coarse wavelength division multiplexing (CWDM) is favored over Dense Wavelength Division Multiplexing (DWDM) when spectral efficiency or the need to transmit over distances beyond 80 km is not critical.

Wavelength Division Multiplexing

The most common method of transporting optical traffic is through a dark fiber pair. Each fiber strand either transmits traffic or receives traffic, but not both. Wavelength Division Multiplexing (WDM) is an optical transport technology that divides each fiber into multiple channels, thus transmitting several streams of data simultaneously.

Telecom Filters

WDM networks transmit multiple wavelengths (or frequencies) of light over the same fiber pair. Thus, operators may transmit several services on a single fiber pair by assigning a different wavelength to each service.

Equipment is placed at either end of a fiber pair. Multiplexers combine the different wavelengths onto a single fiber pair and demultiplexers separate these wavelengths further into the network. Optical Add-Drop Multiplexers (OADM) add or drop wavelengths anywhere along a WDM line.

Compare this with non-WDM networks, where dedicated fiber pairs are utilized for each service. In which case, service providers need to provision fiber pairs for each additional service, increasing the costs of operating the network.

Thus, businesses, government agencies, utilities, healthcare providers, financial institutions, and data center operators favor WDM technology for their mission-critical networks.

Coarse wavelength division multiplexing

Coarse wavelength division multiplexing (CWDM) carries (or multiplexes) up to 18 channels (wavelengths) over a single fiber pair. Coarse wavelength division multiplexing was standardized by the ITU-T G.694.2 based on a wavelength separation of 20 nm between 1270 nm and 1610 nm. Since the channel spacing is 20 nm, the signals do not interfere. Thus, any mix of SAN, WAN, voice and video services can be transmitted simultaneously over a single fiber pair.

Coarse wavelength division multiplexing is flexible enough to be deployed on most types of fiber networks. It is typically deployed in point-to-point topologies in enterprise networks and telecom access networks. Since Coarse wavelength division multiplexing is based on a 20 nm channel spacing, it is typically deployed on fiber spans of less than 80 km because optical amplifiers cannot be used with large channel spacings. The wide spacing of these channels also allows the use of moderately priced optics.

Coarse wavelength division multiplexing can be deployed over single-mode dual fiber, single fiber, or multimode fiber. Multimode fiber enables deployments over short distances, or inside buildings where regulatory or economic limitations prevent the replacement of existing fiber. Also, CWDM Small Form Pluggable (SFP) transceivers are available for all 18 CWDM wavelengths. They are inexpensive and can be used with any networking equipment supporting SFPs.

Most Coarse wavelength division multiplexing equipment is passive, requiring transceivers from active equipment to transmit data. Passive systems require no power, are easy to deploy, and can reduce costs by up to 50% compared to active systems. Fewer active elements mean less latency and higher reliability.

Coarse wavelength division multiplexing uses passive multiplexers and transceivers to quickly scale the capacity of an existing optical fiber infrastructure. It relieves fiber exhaust from video, Wi-Fi and DAS, data center connectivity, and Service Provider Access Networks.

Coarse wavelength division multiplexing is equipment and protocol agnostic. It is a cost-effective solution to optimize an existing fiber infrastructure. Coarse wavelength division multiplexing is inexpensive compared to circuit emulation or installing new fiber.

Iridian CWDM Filters

Iridian supplies a wide range of standard and custom coarse wavelength division multiplexing filters. Iridian Coarse wavelength division multiplexing filters multiplex and de-multiplex wavelength signals in metropolitan networks, access networks, enterprise networks, cable networks, and wireless backbone.

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