The difference between CWDM transceiver and DWDM transceiver

Wavelength division multiplexing (WDM) refers to the use of laser signal multiplexing to send multiple beams of different wavelengths simultaneously on a single optical fiber. Each optical signal has its own wavelength, and they are usually concentrated in the range of 1500nm to 1600nm, which is called the WDM ribbon. Optical signals are modulated by data (text, speech, video, etc.) and transmitted in its own color band. WDM supports existing network bandwidth expansion without the need to add additional fiber optic cables, and can save fiber installation costs, significantly reducing the operational capacity costs of metropolitan and wide area networks. WDM can also implement solutions that cannot be implemented without increasing the number of optical fibers. First, on the one hand, FDM is generally used to describe old multiplexing systems that process electrical signals, while WDM refers to newer multiplexing systems that process optical signals. Secondly, on the other hand, in the FDM system, each frequency multiplexing represents the multiplexing of models from a single transmitting source, while one of the main applications of WDM is the multiplexing of optical fiber synchronous network (SONET) signals. Each SONET signal can transmit multiple signals from multiple sources through time division multiplexing (TDM) technology. Therefore, in the application of timing, WDM technology will generally combine TDM and FDM technologies to achieve higher bandwidth utilization.

DWDM technology multiplexes the tight spectral spacing of a single optical fiber carrier in a given fiber to take advantage of the transmission performance that can be achieved. DWDM wavelength spacing is very tight, because the closer the spacing is, the more channels per fiber will be reused, and thus the higher the bandwidth. The international telecommunication union (ITU) g. 694.1 standard regulates the nominal wavelength interval of DWDM system. Each channel was spaced three ways: 0.4nm(50Ghz), 0.8nm(100Ghz), and 1.6nm(200Ghz). The most important advantage of CWDM is the low cost of equipment. Because of the wide wavelength interval of CWDM system, the requirement for the technical index of laser is low, so the structure of laser is greatly simplified and the yield is improved. In addition, the power consumption and physical size of CWDM system are much smaller than DWDM system. In addition, CWDM light modulation adopts non-cooling laser and electronic tuning. DWDM USES a cooling laser and temperature tuning. Temperature tuning is difficult and expensive to implement because of the unevenness of temperature distribution over a wide wavelength range. CWDM avoids this difficulty, thus significantly reducing the cost. Currently, the cost of CWDM system is generally only 30% of DWDM. As the name implies, sparse wavelength division multiplexing (RWDM) is a close relative of dense wavelength division multiplexing (DWDM). There are two main differences between them. Firstly, CWDM carrier channels are widely spaced. CWDM modulating laser USES non-cooling laser, while DWDM USES cooling laser. Temperature tuning is used for cooling laser and electronic tuning is used for non-cooling laser. Temperature tuning is difficult and expensive to implement because of the unevenness of temperature distribution over a wide wavelength range. CWDM avoids this difficulty, because it significantly reduces the cost, the cost of the whole CWDM system is only 50% of DWDM.CWDM provides a high access bandwidth at a very low cost and is suitable for point-to-point, Ethernet, SONET ring and other popular network structures. It is especially suitable for short distance, high bandwidth and point-intensive communication applications, such as network communication within or between buildings. CWDM and PON (passive optical network) are particularly worth mentioning. PON is an inexpensive, point-to-multipoint optical fiber communication method. By combining with CWDM, every single wavelength channel can be used as a PON virtual optical link to realize broadband data transmission between the center node and multiple distribution nodes. What are the differences between thick wavelength division multiplexer (CWDM) and dense wavelength division multiplexer (DWDM)? take the fast optical fiber as an example to compare the main band spacing and band 2 differences.

Differences between CWDM and DWDM Applications
CWDM is applied to:

1. Point-to-point, ethernet, SDH, SONET ring, EPR (resilient packet ring) and other popular network structures

2. Communication applications with short distance, high broadband and dense access points, such as network communication within or between buildings

3. With PON or DSLAN, each single wavelength channel can be used as a virtual optical link of PON to realize bandwidth data transmission of nodes and multiple distributed nodes. It can also be combined with DSLAN in convergence layer and access layer.

4. G. 652, G. 655 optical fibers, no relay transmission distance not more than 50 km
DWDM is suitable for long-distance, large-capacity long-distance trunk network, or ultra-large capacity MAN core nodes.

Communication systems are designed differently, and the spacing widths between each wavelength are also different. According to the different channel spacing, WDM can be subdivided into CWDM (coarse wavelength division multiplexing) and DWDM (dense wavelength division multiplexing). CWDM: Wavelength spacing (> 20 nm), usually using 1470-1610 nm of eight bands (one at 20 nm interval). DWDM: The wavelength interval is less than 10 nm, and the window is near 1550 nm. Optical devices are expensive and optical terminals are not commonly used. There are two main differences between CWDM and DWDM: one is that the CWDM carrier channel spacing is wider, so the same optical fiber can multiplex to about 10 wavelengths of light, while DWDM can multiply more than 10 wavelengths of light; the other is that CWDM modulated laser uses uncooled laser, while DWDM uses cooling laser. The cooling laser is tuned by temperature and the uncooled laser is tuned by electron. Because the temperature distribution is not uniform in a wide wavelength range, it is very difficult and costly to realize temperature tuning. CWDM avoids this difficulty and reduces the cost greatly. The cost of the whole CWDM system is only 30% of that of DWDM. The wavelength of CWDM ranges from 1470 nm to 1610 nm. DFB lasers are generally used. Because of the large channel spacing, CWDM devices and lasers are cheaper than DWDM devices. CWDM has wider channel spacing, and the number of wavelength multiplexed on the same fiber is less than that of DWDM. This is the reason for the appellation of "coarse" and "dense". CWDM optical modulation uses uncooled laser and electronic tuning, while DWDM uses cooling laser and temperature tuning. Because the temperature distribution is very uneven in a wide optical wavelength region, it is very difficult and costly to realize temperature tuning. CWDM avoids this difficulty and reduces the cost greatly. At present, the cost of CWDM system is only 30% of that of DWDM.