5G bearer network provides the most basic network connection for the 5G wireless access network and the core network. Optical modules are the basic components of the 5G bearer network. With the increase in speed in recent years, the cost of optical modules in system equipment accounts for The ratio is constantly improving, and it has become a key part of 5G’s low cost and wide coverage. Compared with 4G , 5G carries stricter standards in terms of speed, transmission distance, working environment, and fiber cost.

The 5G bearer network is generally divided into the metro access layer, the metro aggregation layer, the metro core layer/provincial trunk line, and realizes the fronthaul and midhaul functions of 5G services.

Under the condition of 5G fronthaul network, the 25Gb/s rate module is mainly based on SFP 28, and the dual-fiber bidirectional, single-fiber bidirectional, 25GWDM and other solutions can save costs.

Under the condition of medium transmission network, 25G optical devices are used, and the bandwidth of optical devices is doubled by using PAM4 technology; 10km and 40km transmission distances will cover most application scenarios, and coherent technology will be used for transmission distances exceeding 80km.

Typical application scenarios of 5G fronthaul include direct fiber connection, passive WDM and active WDM, etc.

Fiber direct connection scenarios generally use 25Gb/s optical modules, which support two types of dual-fiber bidirectional and single-fiber bidirectional, mainly including two transmission distances of 300m and 10km.

Passive WDM scene point-to-point, using a pair or a fiber connection, requires 10Gb/s or 25Gb/s optical module.

Active WDM scenarios generally require 10Gb/s or 25Gb/s optical modules, and special cases require dual-fiber bidirectional or single-fiber bidirectional optical modules with rates of N×10 25 50 100G b/s.

Typical requirements for optical modules in 5G fronthaul application scenarios are as follows:

①Meet the temperature of industrial grade, high reliability requirements: Considering the outdoor working environment, the fronthaul optical module must meet the industrial grade temperature range of -40℃～+85℃, and also need to meet the dustproof requirements

②Low cost: The demand for 5G optical modules greatly exceeds that of 4G, especially for fronthaul optical modules. Low cost is one of the main requirements for optical modules in the 5G industry. 5G medium and backhaul covers the metropolitan access layer, aggregation layer and core layer. The required optical modules are not much different from the optical module technology used in the current data center . The access layer will mainly use 25Gb/s, 50Gb/s, 100Gb/s s and other rate optical modules, the convergence layer and above will mostly use DWDM optical modules with rates of 100Gb/s, 200Gb/s, 400Gb/s and so on . HYPERLINK “http://fiber.ofweek.com/KW-dwdm.html” \o “DWDM” \t “https://fiber.ofweek.com/2021-05/_blank”