With the development of data communication and telecommunication technology, the intention of MAN(Metropolitan Area Network)is no longer relative to the wide area network. Due to the high bandwidth and data transmission transparency of DWDM(Dense Wavelength Division Multiplexing) tech, people naturally hope to introduce DWDM as the platform of MAN. However, in the MAN, an optical amplifier is not needed on account of the short transmission distance.
If the same DWDM devices as that of WAN(Wide Area Network) are adopted in the MAN, it will not be worth the candle. Thus, DWDM is not seemingly suitable for MAN. While as a simplified version of DWDM technology, CWDM can satisfy the requirements for the practical characteristic of Metropolitan Area Network(Metropolitan Area Network)in short transmission distance without the need of expensive devices such as amplifiers and transceivers. After that, the adoption of CWDM is undoubtedly the best choice to save cost.
What Is the CWDM?
CWDM (Coarse Wavelength Division Multiplexing/sparse wavelength division multiplexing), as its name implies, is a close relative of dense wavelength division multiplexing. Because the transmission distance of the metropolitan area network is usually not more than 100km, the system has low requirements for the transmission attenuation of the single mode fiber and the fiber amplifier is not also needed. In this way, the bandwidth window of 1200~1700nm can be used and the adjacent wavelength interval is relaxed to 10~20nm, which can also form dozens of wavelength division multiplexing systems. This is the coarse wavelength division multiplexing (CWDM) system.
What Are the Advantages of CWDM?
Compared with the application of DWDM communication in the backbone network, CWDM communication increases the multiple light signal wavelength interval multi-wavelength technology. It can take advantage of the light source without temperature control, as well as build a communication system with low cost. The features and advantages of CWDM are as below:
- The wide wavelength interval greatly reduces the requirements for the performance of optical devices, such as the corresponding lasers and filters.
- Laser without cooling function, direct modulation, without wavelength locked.
- Due to the short transmission distance(within 50KM), there is no need for an amplifier in general conditions.
- Low cost: CWDM technology makes full use of the feature of metropolitan area network such as short transmission distance; it can be directly applied in the entire optical fiber transmission window of 1310~1560nm and operates the wavelength division multiplexing based on the wider wavelength interval than DWDM system. On account of the wide wavelength interval and short transmission distance, it is unnecessary for CWDM to choose expensive laser, which greatly reduces the cost of laser. Besides, CWDM needn’t utilize complex control techniques to maintain higher system requirements. It just needs to choose low-cost coarse wavelength division multiplexer/demultiplexer and multi-channel laser receiving/transmitting device as the relay. The reduction to the cost of components and the requirements of the system leads to the lower cost in CWDM system than DWDM system. The cost of the CWDM filter is 70% less than that of the DWDM filter. The adoption of new filters and multiplexers/demultiplexers is possible to further reduce costs. The initial design of CWDM is aimed at low-cost wavelength division multiplexing tech, so that the advantage of CWDM in cost is the highlight of this tech.
- Low Power Consumption: the operating cost of an optical transmission system depends on the maintenance and the power consumption of the system. In this respect, the power consumption of the CWDM system is much lower than that of the DWDM system. For example, a DWDM laser with a cooler and control circuit needs to consume about 4W power per wavelength; while the CWDM laser without a cooler consumes only 0.5W power. The four waves of CWDM optical transmission system consumes about 10~15W power, while the power consumption of the DWDM system similar to it is up to 30W. In the DWDM system, with the increases in the total number of multiplexed wavelength and single-channel transmission rate, the power consumption and temperature management become a key problem in circuit board design.
- Small Size: a CWDM laser is much smaller than a DWDM laser. CWDM uses a laser without cooler; the laser is usually composed of a laser sheet and a monitoring photodiode sealed in a metal container with a glass window. The size of the DWDM laser transmitter is about five times the size of the CWDM laser transmitter. In addition to the above six aspects, CWDM has more obvious advantages in security, network flexibility and etc.
- Flexible Service Interface: the CWDM system is mainly used in the metropolitan area network; it provides multi-service transparent transmission. It is flexible in the client-side service interface, and can support the following services:
- SDH services: support the SDH service of the STM-x (x=1, 4 and 16) based on ITU-T G.707; Ethernet services: support 10M/100M and Gigabit Ethernet services;
- ATM services: support ATM services of STM-x (x=1, 4 and 16) based on ITU-T G.707 standard;
- other services possible to be widely applied in the future, such as Fiber Channel, ESCON, FICON, DigitalVideo, 10GE and so on); PDH service of 8/34/140Mb/s.
With various advantages, CWDM tech is naturally in great favor by many manufacturers and suppliers in the optical communication industry. It is believed that CWDM will be with more advantages with the future development of techs. In addition, Gigalight, as the professional supplier of optical components, has pushed out a series of CWDM products to follow the market’ trend, in which QSFP28 CWDM4 optical transceiver is the hottest one.