Optical Communication

Wavelength Division Multiplexing Technology

Being a technique where optical signals with different wavelengths are combined, transmitted together, and separated again, wavelength division multiplexing (WDM) is mostly used for optical fiber communications to transmit data in several (or even many) channels with slightly different wavelengths. This technique enables bidirectional communications over one strand of fiber, as well as multiplication of capacity.


WDM Operating Principle
There is a multiplexer at the transmitter and a demultiplexer at the receiver in a WDM system. With a right type of fiber, this system can simultaneously use the multiplexer to join the signals together and the demultiplexer to split them apart, functioning as an optical add-drop multiplexer. A WDM system can keep the transmission rates of each channel at reasonably low levels (e.g. 10 Gbit/s or 100 Gbit/s) and achieve a high total data rate by combining several or many channels. The first-generation WDM system combined only two signals. The modern system, however, can handle up to 160 signals and can thus expand a basic 10 Gbit/s system over a single fiber pair to over 1.6 Tbit/s.

Different Versions of WDM
Coarse Wavelength Division Multiplexing (CWDM) and Dense WaveLength Division Multiplexing (DWDM) are two kinds of wavelength-division multiplexing (WDM). Seeing from their development, DWDM came well before CWDM. DWDM appeared only after a booming telecommunications market, driving prices to affordable lows. Whereas CWDM breaks the spectrum into big chunks. Here is some information related to the differences between CWDM and DWDM.

CWDM is a method of combining multiple signals on laser beams at various wavelengths for transmission along fiber optic cables. Its WDM system has less than 8 active wavelengths per optical fiber. Each CWDM wavelength, which can be expanded to 10Gbps support, typically supports up to 2.5Gbps. This transfer rate is sufficient to support GbE, Fast Ethernet or 1/2/4/8/10G FC, STM-1/STM-4/STM-16 / OC3/OC12/OC48 and other protocols.

18-channels-Duplex-CWDM DWDM
DWDM is a fiber-optic transmission technique that employs light wavelengths to transmit data parallel-by-bit or serial-by-character. Its WDM system has more than 8 active wavelengths per optical fiber. Providing up to 96 wavelengths (at 50GHz) of mixed service types, the DWDM systems can transport to distances up to 3000 km through the deployment of amplifiers and dispersion compensators, which increases the fiber capacity by a factor of x100. Today’s DWDM solution is often embedded with Reconfigurable Optical Add Drop Multiplexer (ROADM).

Expanding the capacity of the network without laying more fiber, WDM systems are popular among telecommunications companies. Through the use of WDM and optical amplifiers, these companies can accommodate several generations of technology development in their optical infrastructure without having to overhaul the backbone network. A series of WDM modules are provided in Fiberstore, which enable the expansion of existing fiber capacity.

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