What is C band and L band in WDM (Wavelength Division Multiplexing)?

WDM (Wavelength Division Multiplexing) is a transmission technology that uses a single optical fiber to simultaneously transmit multiple optical carriers of different wavelengths in optical fiber communications. When the wavelength of light is different, the transmission loss in the fiber is also different. In order to reduce fiber loss, it’s important to find the most suitable transmission wavelength. After a long period of exploration and testing, light with a wavelength of 1260nm~1625nm has the smallest dispersion signal distortion with low loss, which is the most suitable for transmission in optical fiber.

The fiber loss of different wavelength

The wavelength of fiber can be divided into several bands, each band is used as an independent channel to transmit predetermined wavelength. According to the ITU-T standards, single-mode fiber with the band over 1260nm is divided into O/E/S/C/L/U
six bands.

Different bands

What is O band?
The O band is the original band with wavelenght from 1260 to 1360nm. The O-band is the first wavelength band used in optical communications in history, and the signal distortion (due to dispersion) is minimal.

What is E band?
The E-band (extended wavelength band: 1360-1460 nm) is the least common of these bands. The E-band is mainly used for the expansion of the O-band, but it is rarely used, mainly because many existing optical cables show high attenuation in the E-band and the manufacturing process is very energy-intensive, so the use in optical communication is limited.

What is S band?
The optical fiber loss in the S-band (Short-wavelength Band, 1460-1530 nm) is lower than the loss in the O-band. The S-band is used as many PON (passive optical network) systems.

What is C band?
The C-band (Conventional Band) ranges from 1530 nm to 1565nm and represents the conventional band. Optical fiber shows the lowest loss in the C-band and occupies a large advantage in long-distance transmission systems. It is usually used in many metropolitan areas combined with WDM, long-distance, ultra-long-distance and submarine optical transmission systems and EDFA technology. As the transmission distance becomes longer, and fiber optic amplifiers are used instead of optical-to-electronic-to-optical repeaters, the C-band becomes more and more important. With the advent of DWDM (Dense Wavelength Division Multiplexing) that allows multiple signals to share a single fiber, the use of the C-band has been expanded.

What is L band?
The L-band (Long-wavelength Band, 1565-1625nm) is the second lowest-loss wavelength band and is often used when the C-band is insufficient to meet the bandwidth requirements. With the wide availability of b-doped fiber amplifiers (EDFAs), DWDM systems have expanded upward to the L-band, and were initially used to expand the capacity of terrestrial DWDM optical networks. Now, it has been introduced to submarine cable operators to do the same thing-to expand the total capacity of submarine cables.

Due to its low transmission attenuation loss, C-band and L-band is usually selected to use in the DWDM system. Except for the O-band and L-band, there are two other bands, the 850nm band and the U band (ultra-long band: 1625-1675 nm). The 850nm band is the main wavelength of the multimode optical fiber communication system, which combines VCSEL (Vertical Cavity Surface Emitting Laser). The U frequency band is mainly used for network monitoring.

WDM technology can be divided into WDM, CWDM, DWDM according to different wavelength modes. The wavelength range stipulated by ITU for CWDM (ITU-T G.694.2) is 1271 to 1611nm, but considering the attenuation of the 1270-1470nm band in the application, the band of 1470~1610nm is usually used. The channel space of DWDM is more closeness, so choose the C-band (1530 nm-1565 nm) and L-band (1570 nm-1610 nm) transmission windows. Ordinary WDM generally uses 1310 and 1550nm wavelengths.

The wavelength of CWDM

With the growth of FTTH applications, the C-band and L-band will play an increasingly important role in optical transmission systems.

HYC Co., Ltd has 20 years of OEM/ODM manufacturing experience in the optical communications industry. The WDM devices independently developed and manufactured are fully used in metropolitan area networks and 5G networks. The diversified design and production capabilities meet various application requirements, such as pigtail modules, plug-in The LGX, high-density rack, 6port WDM, CCWDM, non-thermal multi-channel AWG, 5G module, etc., fully contribute to the global 5G deployment and development.

10,000 5G base stations will be added every week? What are the features of 5G?

One of the hot spots in China in 2020 is to accelerate the deployment of 5G networks and expand 5G applications. According to public data from the government, more than 10,000 5G base stations will be added in China every week. This shows that 2020 will be the explosive first year of China’s 5G base station construction, and 5G will also enter a new era of development.

What is 1G~5G network?
1G network is the first generation of mobile communication technology that first appeared in 1983. It uses analog voice signals to send and receive, and the call quality is not good. Each region has its own common standards, such as TACS in the United Kingdom, AMPS in the United States, RTMI in Italy, etc., leading to widespread failure.

2G network is the second generation of mobile communication technology using digital signals. It has SMS and fax functions on the basis of 1G, and the call quality is also better than 1G. During this period, there are already mobile phones, but only a simple call function.

3G third-generation communication technology can process images, music and videos, provide Web browsing, teleconferencing and e-commerce information services. It also has the global standard IMT-2000. It also defines China’s W-CDMA, CDMA2000 and TD-SCDMA communication standards.

The 4G fourth-generation communication technology integrates 3G and WLAN, and can transmit high-quality video images.

5G refers to the “fifth generation”, that is, the fifth generation mobile communication system or the fifth generation mobile network technology, which is the expansion and upgrade of 4G technology.

Some people have summarized these generations of mobile communication technologies: 2G opened the text era, 3G opened the image era, 4G opened the video era, and 5G is about to start the era of Internet of Everything. 5G has three main characteristics: “High rate, low latency and large capacity”.

1G, 2G, 3G, 4G, 5G

High speed
High speed is the most intuitive user experience. The 5G network speed has been greatly improved, reaching a maximum of 10Gbit/s, and the theoretical transmission speed is one hundred times faster than the previous 4G LTE cellular network.

Low latency
The simplest understanding of low latency is that when you enter a URL in a web browser, you must wait for two time delays to complete the process of opening a web page. Confirmation time requested by the user; and the time required to send text, images, and video to the user. This is the network delay.

5G technology can effectively reduce the delay and increase the data transmission rate. The response time can be reduced from the average 50ms (0.05s) of 4G to 1-2 milliseconds (0.001-0.002s). Similarly, the data transmission speed can be increased from 0.02-0.03Gbps to 0.1-5.0Gbps, which means that we can load the entire webpage in 1 second.

Low latency will provide reliable and extremely low latency for applications with high real-time performance, such as games, video, live broadcasting, Internet of Vehicles and industrial control, thus creating countless possibilities.

High capacity
Existing 4G base stations have only a dozen antennas, but 5G base stations can support hundreds of antennas. These antennas can form a large-scale antenna array through Massive MIMO technology, which means that the base station can simultaneously transmit and receive signals from more users. As a result, the capacity of the mobile network has increased tens of times or more. The large-capacity features of 5G will play a greater role in the Internet of Things, smart homes, smart cities, and real-time logistics tracking.

Micro base station
In the 2G era, the signal of one large signal tower can covers a small town. In the 3G/4G era, a large number of small base stations need to be deployed. In densely populated areas, more than ten small base stations need to be deployed every 100 meters. In the 5G era, the use of millimeter waves has increased bandwidth. The number of users is 100 times that of 4G and the network speed is 100 times that of 4G. This means that only a few large base stations need to be established, but small base stations are widely distributed. This is the micro base station of 5G network.

4G VS 5G

4G uses lower frequency bands, and one large base station can covers 2 to 40 kilometers. As the communication technology is deployed to the high frequency band of 5G, the diffraction ability of electromagnetic waves becomes weak, and the transmission distance and coverage are relatively small. Therefore, 5G must use multiple micro base stations to cover the same base station area.

HYC Co., Ltd. can provide customers with a full range of passive WDM modules for 5G fronthaul transmission. As a leading fiber optic cable manufacturer, HYC has 20 years of OEM ODM experience for passive optical devices. It has a strong R&D team and strong production capacity, and can provide customers with one-stop customized optical communication passive basic equipment design, research and development and manufacturing services. Its production line includes optical fiber connectors, optical fiber jumpers, PLC splitters, WDM wavelength division multiplexers, MEMS optical switches, etc.

What is 5G Fronthaul,Middlehaul,Backhaul?

5G network has three parts, Access Network, Bearer Network, and Core Network. The access network is also Radio Access Network(RAN), which is mainly composed of base stations.

So what does the base station include? The base station usually includes BBU (mainly responsible for signal modulation), RRU (mainly responsible for radio frequency processing), feeder (connecting RRU and antenna) and antenna (mainly responsible for the conversion between the guided wave on the cable and space wave in the air.

Each base station in 4G network has a BBU, which is directly connected to the core network. In 5G networks, the access network is no longer composed of BBU, RRU and antenna. Iit is reconstructed into the following three functional entities: CU (centralized unit), DU (distributed unit) and AAU (active antenna unit). The original 4G RRU and antenna are combined into AAU, and BBU is divided into CU and DU. DU sank to AAU. One CU can be connected to multiple DUs.

The 4G network has fronthaul and backhaul. But in the 5G network, it is divided into three parts. The AAU connected to the DU is called 5G Fronthaul. A part of the DU connected to the CU is Middlehaul, and the backhaul is the communication carrier between the CU and the core network.

HYC Co., Ltd has been dedicated to the manufacture of passive optical devices for 20 years, and has a strong R&D team and strong production capacity. HYC can provide one-stop OEM ODM services for design, R&D and manufacturing. The production line has optical fiber connectors, adapters, plc splitters, wdm, mems optical switches, etc.
www.hyc-system.com