In terms of 5G carry technology solutions and industrial research. The access layer is dominated by 25G and 50G. In the early stage of construction, the bandwidth and capacity of 5G have not yet been expanded. The 25G first-level return basically meets the demand. In the convergence layer and core layer, 100G is the main layer at present. With the expansion of network scale and network centralization, 400G May be achieved in the future, and the wave component technology may even be used to enhance the capacity.
There are several technologies in 5G prequel, the most mature CWDM is the earliest and most mature, it can support 6 waves, LWDM/MWDM support 12 wave 25G and can further save fiber. For optical modules, the prequel 25G/10G interface is compatible, and the technology is very mature. High-density and low-power packages are required for 100G, such as the SFP28. The overall requirements for 5G construction need to be low-cost and interconnected, which is essentially further reducing costs.
Under the model of co-construction and sharing, CRAN will become the main application scenario. CRAN has the following advantages: 1. Compared with DRAN, CRAN can reduce the demand of terminal machine room and transmission equipment, save site acquisition, room rent and transmission cost, and theoretically, the higher the concentration degree, the more obvious the effect is; 2. 2. Since DU is placed centrally for unified maintenance, it has certain advantages over DRAN in construction cost and maintenance cost. CRAN will become the main deployment mode for 5G construction. At the same time, CRAN mode can realize the pooling or cloud of DU, and realize the sharing of baseband resources and the business cooperation between multiple stations. XWDM will become the mainstream due to CRAN's high consumption of pre-fiber.
After co-construction and sharing, 100M changed to 200M, and the station type upgraded from S111 to S222, that is to say, the optical modules for pretransmission requirements of 3.5GHz carrier frequency changed from 3 to 6 25G. With the development of 5G, more 10G prequel interfaces will be introduced in the future. Under the spectrum of 3.5GHz 200MHz+ 2.1GHz, 6 25Gb/s +3 10Gb/s (single anchor points) or 6 25Gb/s +6 10Gb/s(double anchor points) will be used. In the future 3.5GHz 200MHz+ 2.1GHz + 1.8GHz spectrum, 6 25 GB/s +4 /8 10 GB/s will be used.
In the DRAN-oriented application scenario, the transmission of optical module reduces the sensitivity of optical fiber cost due to the short transmission distance. The 25 GB/s BIDI scheme is a relatively reliable scheme. Starting in 2018, the technology for the 25 GB/s BIDI has been deeply researched and standards developed. DML+PIN is adopted internally in this scheme, which has the advantages of low cost, high reliability and high temperature support, mature industry, multi-manufacturer support and interconnectivity.
In CRAN-oriented application scenarios, fiber direct drive consumes too much fiber and has no advantage. There are several solutions for CRAN. Passive CWDM scheme is the most mature and adopts DML+PIN. The advantages of passive CWDM scheme are simple, no temperature control (TEC) and low cost. 4 Wave CWDM has been widely used in data centers, while 6x10G CWDM has been applied in 4G prequel, and the industry chain is mature. Support 100MHz carrier frequency single station single fiber. Recently, in China mobile provincial companies and telecommunications groups to promote the collective mining, shipments reached hundreds of thousands of prices fell fast.
