Technical Support

The Function of WDM/CWDM in the Expansion and Upgrade of Communication Network

Author:Takfly Group    Date:2017-03-07    Tags:Technical Support

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WDM (Wavelength Division Multiplexing) technology is a technology which can transmitter multi-wavelength fiber optic signal at the same time by an optical fiber. It is in the sending end of the different wavelengths of optical signals combined (multiplexed), and coupled to the same fiber optic cable in the transmission, at the receiver in turn combined with the wavelength of the optical signal (demultiplexing) and make further processing, restore the original signal into a different terminal. Therefore, this technology is called optical wavelength division multiplexing, referred to as optical wavelength division multiplexing (WDM) technology.

The 1310nm wavelength segment and the 1550nm wavelength segment are approximately 200nm low loss area, which is equivalent to the bandwidth of 30000GHz. However, in the current real fiber-optic communication system due to fiber dispersion and modulation rate constraints, single-channel TDM system communication rate is limited to 10Gbit / s or below, so single-mode fiber there are still most of the bandwidth resources to be developed.


As some of the current optical devices and related technology is not very mature, so to achieve a very dense optical channel reuse (called optical frequency division multiplexing) is also more difficult. In this case, wavelength division multiplexing with a smaller channel spacing in the same low loss window of the fiber is referred to as DDM Wavelength Division Multiplexing. WDM technology is very important for the expansion and expansion of communication network, the development of various broadband services and the full exploration of fiber bandwidth potential.

Simplex fiber bi-directional diagram
Duplex fiber two-way schematic diagram

WDM system consists of five parts: optical transmitter, optical relay amplification, optical receiver, optical monitoring channel and network management system.

The Key Technology of Optical Wavelength Division Multiplexing System

WDM system application to increase the communication capacity, information network construction is of great significance. But there are still some technical problems. For example, the wavelength and stability of the laser are demanding. The non-linearity of the fiber is very limited to the output power of the optical amplifier. The "four-wave mixing" effect causes the crosstalk between channels. The dispersion effect of the fiber Increase the speed; how to monitor the line optical amplifier and other issues.

In the WDM system, the wavelength of the light source must be precisely set and controlled, otherwise the wavelength of the drift will inevitably cause the system can not be stable and reliable work. So the requirements in the WDM system to have a matching wavelength monitoring and stability technology.

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The main methods currently used are temperature feedback control method and wavelength feedback control method to achieve the purpose of controlling and stabilizing the wavelength.

Mux / Demux and optical filter technology

Mux / Demux is a key component of wavelength division multiplexing system. Its function is to combine multiple wavelengths of different optical signals into the same fiber transmission (wavelength division multiplexer) or in a fiber in a number of different wavelengths of optical signal decomposition into different receiving Machine (demultiplexer).

Mux and Demux are also known as multiplexers and demultiplexers, and are wavelength-dependent fiber couplers.

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The performance of Mux/Demux has a decisive influence on the transmission quality of the WDM system.

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WDM system in the optical fiber transmission technology and the general optical fiber communication system, due to the existence of high transmission rate and the number of channels and more features, so there are some special requirements, including fiber selection, dispersion compensation technology and dispersion equalization technology.

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