The coarse wavelength division multiplexer, CWDM for short, multiplexes the optical signals of different wavelengths to a single fiber for transmission by optical multiplexer, decomposes the signals of different wavelengths at the receiving end, and connects them to the corresponding receiving equipment. It is the best choice to increase the bandwidth capacity and reduce the cost.
Define
CWDM(Coarse wavelength division multiplexer), referred to as "CWDM, is to increase the bandwidth capacity can satisfy the best measures to reduce costs at the same time, suitable for WWDM, of CWDM and DWDM transmission PDH, SDH/SONET and ETHERNET services, can be widely used in the metropolitan area network transmission and access layer.
Principle
The coarse wavelength division multiplexer (WDM) adopts a low cost WDM transmission technology for man access layer. In principle, CWDM multiplexes optical signals of different wavelengths to a single fiber for transmission by optical multiplexer. At the receiving end of the link, optical demultiplexer is used to decompose mixed signals in the fiber into signals of different wavelengths and connect them to the corresponding receiving equipment.
Feature
1. Adopt passive technology without power supply;
2. Standard 18 channels, CWDM band 1270nm-1610nm, band interval of 20nm;
3. 1RU rack chassis;
4. Return loss ≥ 45dB;
5. Monitoring port ensures no time difference to troubleshoot;
6, LC/UPC duplex connector, easily support transceiver and passive device of indirect plug duplex jumper;
7. Channel insertion loss < 4.9db;
8. The operating temperature is -10~70°C.
Insufficient
The biggest problem with CWDM technology is that its cost advantage over DWDM equipment is still not obvious. At present, the number of optical channels (wavelength) supported by CWDM equipment is not more than 8, mainly for the manufacturing process of e-band optical transceiver module is not mature, in addition, the elimination of water absorption peak of the g. 652C optical cable in the network is less applied, so there is little market demand for e-band optical transceiver module. CWDM systems with higher rates and longer transmission distances still have many technical problems, such as 10G system dispersion problem, ultra-wideband optical amplification technology. In addition, the standardization process needs to be accelerated, especially the guidance of operators on the function of the business interface.
Differences between CWDM and DWDM
1. Compared with the wavelength interval of 0.2nm to 1.2nm in DWDM system, CWDM has a wider wavelength interval, and the standard wavelength interval in the industry is 20nm.
2. The number of coating layers of the filter in CWDM system can be reduced to about 50 layers, while the number of coating layers of the 100GHz filter in DWDM system is about 150 layers.
3. The cost of CWDM filter is more than 50% less than that of DWDM filter, and will be further reduced with the increase of automated production technology and batch;
4. CWDM modulated laser adopts uncooled laser, while DWDM adopts cooled laser. The cooled laser adopts temperature tuning, while the uncooled laser adopts electronic tuning.
