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WDM Solutions

WDM - Wavelength Division Multiplexing

CWDM and DWDM systems

>> WDM products

In the past, the WAN world was dominated by time-division multiplex protocols such as PDH (2–34 Mbit/s) and SDH (155 Mbit/s–10 Gbit/s). Thanks to the increase in Ethernet services and the associated bandwidth explosion, new methods are necessary to continue meeting users’ requirements. Wavelength division multiplexing (WDM) is a promising technology for integrated voice and data networks with high transmission rates. Numerous optical signals can be transmitted over a single fibre-optic connection simultaneously.

Each signal is transmitted through the optical fibre at a slightly different wavelength (or colour). The individual signals are separated at the receiving end by using optical filters. This means the signal is completely independent of other channels in the same optical fibre and can take on any number of services. Several services (100/1,000/10,000 Mbit/s Ethernet, STM-1, -4, -16, -64, ESCON, Fibre Channel, etc.) can be jointly run over one or two optical fibres. Each service is transmitted as its own light colour. Thanks to optical add/drop multiplexers (OADM), individual channels can be decoupled and thus redundant ring structures can be built.

WDM does not need any special optical fibres, only ubiquitous standard fibres, meaning that existing links can be optimised using additional transmission channels. Two WDM techniques are currently widely used: CWDM and DWDM:

Kanalabstände CWDM / DWDM

CWDM / DWDM channel spacing

CWDM technology

Coarse wavelength division multiplexing (CWDM) is a WDM technology that works with large distances (20 nm) between the channels in the optical spectrum. This means that LEDs or uncooled lasers can be used as transmitters in place of costly temperature-controlled lasers. CWDM systems are currently used in the classic 1,310 and 1,550 nm areas. CWDM allows you to transfer up to 16 independent channels with just one optical fibre pair, which leads to significant cost reductions. Ranges of up to 120 km and data rates of up to 10 Gbit/s are possible.

Separation of process data transmission and LAN
Separation of process data transmission and LAN

DWDM technology

Dense wavelength division multiplexing (DWDM) is an optical wavelength division multiplexing process at a high density of 1,550 nm; the spacing of the channels is between 0.8 nm and 1.6 nm. The ITU-T sets out the wavelengths and channel spacing in Recommendation G.692, known as the ITU Grid. Our systems offer the transmission of up to 80 channels via an LWL pair with ranges of up to 720 km. The modular design, the wide transmission range (100 Mbit/s–100 Gbit/s) of the transponders and the use of numerous LWL interfaces as GBIC and SFP modules make the overall system extremely flexible.

DWDM ring configuration
DWDM ring configuration

WDM - Transport systems:

Ciena 6500  - Packet-Optical Platform
XTG-Series - Passive C/DWDM platform
XTM-Series - Carrier Class C/DWDM system