In this blog, ETU-LINK will talk about 4G base stations and common types of optical modules. The base station can be divided into two modules: the RRU for transmitting signals and the BBU for processing signals. The BBU is small and exquisite, with low power consumption, while the RRU is large and has high power consumption. Because the base station is divided into two parts to work separately, so this site is also called a distributed site, which involves the connection between BBU and RRU. How to connect the BBU and RRU, the two devices that process electrical signals, with optical fiber? This requires our optical module.

The transmission bearer connecting BBU and RRU equipment is optical module and optical fiber.In 4G network, the equipment used for connecting BBU and RRU can be 1.25G optical module , 2.5G optical module, 6G optical module and 10G optical module.

Since the construction of 4G network requires a large number of BBU and RRU, and the distance between BBU and RRU is relatively far. RRU need at least 2-6 core optical fibers to transmit.Therefore, the passive wavelength division solution was born.

Through BBU / RRU serial networking, the problem of long-distance transmission and lack of optical fiber resources can be solved. BBU end can be connected to CWDM coarse wavelength division multiplexer through CWDM color optical module and OS2 single mode optical fiber patch cord, and then transmitted to CWDM coarse wavelength division multiplexer with one or two optical fibers. CWDM coarse wavelength division multiplexer is connected to RRU equipment with CWDM optical module and OS2 single mode optical fiber patch cord . The schematic diagram of BBU / RRU serial networking is shown below.

Using passive wavelength division system can effectively solve the problem of insufficient optical fiber between several stations, so that the base station can expand capacity quickly. Later 5g will gradually replace 4G, but 4G is still the mainstream. Many 5g pilot base stations will still use 10G optical modules for transmission. So 10G optical modules are still the mainstream products in the telecommunications industry.