CWDM Multiplexer Technology for MAN Access Layer 

As a result of rapid development of data services, network convergence speed accelerated MAN has become a hotspot of network construction, plus more understanding of the pressure of market competition helps make the price of telecom operators around the network (including construction costs and operation and maintenance costs). MAN with this market demand, low-cost CWDM products emerged. MAN, short transmission distance, do not have to utilize the amplifier, optical fiber transmission attenuation value is less sensitive CWDM multiplexer technology can help to eliminate the performance requirements of the device, components, thus greatly reducing the cost.

DWDM Mux and Demux

The spacing between the transmissions of different wavelengths inside the same fiber may be the main parameter to distinguish between DWDM and CWDM. Normally the wavelength interval of the DWDM system 200GHz (1.6nm), 100GHz (0.8nm) or 50GHz (0.4nm), future systems could have a more narrow pitch. DWDM system, DFB (distributed feedback) laser because the light, the temperature drift of the latter coefficient of 0.08nm /°C, it has to make use of a cooling technique to stabilize the wavelength, to avoid alterations in wavelength as a result of temperature drift for the multiplexer demultiplexing a filter pass band.

DWDM SFP+ Optical Transceiver

CWDM(Coarse Wavelength Division Multiplexing) systems is a low-cost WDM transmission technology for MAN access layer. Principle, CWDM may be the use of the optical multiplexer to different wavelengths regarding signals multiplexed with a single optical fiber for transmission, in the receiving end of the link, with the optical demultiplexer fiber mixed signal is decomposed into different wavelengths signal, coupled to the respective receiving apparatus. The real difference is the fact that with the DWDM: 0.2nm to at least one.2nm wavelength interval according to the DWDM product is concerned, CWDM has a wider wavelength interval, a accepted standards wavelength intervals of 20 nm.

CWDM technology optimum use with the characteristics of your short transmission distance of the MAN, without by EDFA amplification band limited, but might be around the entire optical fiber transmission window within the 1310-1560 nm wavelength interval much wider than DWDM system wave stars multiplexing. As a result of wide wavelength interval, the transmission distance is brief, CWDM without selecting the expensive high wavelength stability along with a high dispersion tolerance from the laser, which can greatly reduce the laser cost. 

In addition, CWDM without selecting costly dense wavelength division demultiplexer and multiplexer, simply choose the cheap coarse wavelength division multiplexer and demultiplexer; without complex control technology to keep high system requirements. Simply using less expensive than the multichannel laser without the need for EDFA, send and receive like a relay. Reduce device cost and system requirements, CWDM system cost than DWDM systems have dropped significantly.

Even though prices are reduced cost than DWDM, CWDM systems and DWDM interface to aid multi-service SDH interface, for example, provides IP / Ethernet over SDH, ATM, over SDH; provide direct fiber connection port for that routers and ATM switches, IP / Ethernet over Optical and ATM over Optical. CWDM system can also use OTU (optical transmission unit) and OADM (optical add / drop multiplexing) with the use of standard wavelength DWDM system interconnect ring or access DWDM backbone layer. CWDM 1310nm SDH system compatibility may be popular in MAN, the present DWDM can’t do this. The CWDM technology even offers the opportunity applied to the long-distance transmission capacity, broadband LAMAN (Raman) optical amplifiers to the commercial the CWDM technology there's more likely to go into the long-distance transmission market.

CWDM by larger wavelength interval so that the optical transceiver modules and passive optical multiplexer / demultiplexer, cost reduction, and business transparency, simple operation and maintenance, scalability advantages, so by the industry attention, but CWDM cost advantage isn't outstanding, the gear is not perfect, the little quantity of optical channels. With all the increase of industry and technology development, found in the metropolitan area network access layer CWDM technology can have a good prospect of application.

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