5G technology has entered the commercialization process, and its new service features and higher metrics require new challenges for the bearer network architecture and various layers of technical solutions. The optical module is the basic component of the high-speed interconnection of the 5G network. The cost in some devices is even more than 50%~70%, which is one of the key elements of 5G low-cost and wide coverage. Due to different requirements such as rate capacity, transmission distance, working environment, fiber resources, and synchronization characteristics, 5G pre-transmission and medium-retransmission are required to differentiate optical modules. Optical modules should meet higher speeds, longer distances, wider temperature ranges, and lower cost. A variety of solutions have emerged, and the types are complex, requiring industry efforts to promote further convergence.

Typical application scenarios for 5G preamble include fiber direct connection, passive WDM, semi-active WDM, and active WDM, as shown in Figure 1. The fiber-optic direct-connect network is simple, easy to maintain, and has a low latency but consumes a large amount of fiber. The WDM solution reduces the fiber footprint but faces other problems such as increased cost and additional power supply when active.

Typical application scenarios and development status of 5G optical modules


Figure 1 (a) Fiber Direct Connection (b) Passive WDM (c) Semi-Active WDM (d) Active WDM

The optical fiber direct connection scenario generally adopts a 25 Gbit/s gray-light module and supports two types of dual-fiber bidirectional and single-fiber bidirectional. It is the dominant solution in the short-term deployment of 5G. With deep coverage such as high-frequency networking and low-frequency boosting, WDM deployment will gradually increase in order to make full use of existing fiber resources or solve the problem of fiber resources shortage. Passive WDM scenarios mainly include point-to-point passive WDM and WDM-PON. One or one optical fiber is used to implement multiple AAU to DU connections. Typically, 10Gbit/s or 25Gbit/s color optical modules are required. Active WDM scenarios generally require 10 Gbit/s or 25 Gbit/s short-range gray-light modules between AAU/DU to WDM/OTN/SPN devices, and N×10/25/50/100 Gbit/ between WDM/OTN/SPN devices. s equal-rate dual-fiber bidirectional or single-fiber bidirectional color light module. The semi-active scene combines the characteristics of the above two scenarios, using active WDM/OTN/SPN devices on the DU side and passive wavelength division multiplexers on the AAU side.

For the AAU full outdoor application environment, the typical requirements for the optical module in the 5G pre-transmission application scenario are firstly to meet the industrial temperature range of -40 ° C ~ +85 ° C and environmental reliability requirements such as dustproof. In addition, the total demand for 5G optical modules is expected to exceed 4G. In particular, there may be tens of millions of orders for the pre-transmission modules, and the demand for corresponding optical resources will be greatly increased. Low cost is one of the main demands of the industry for optical modules.

The 5G mid-back transmission covers the metro access layer, the aggregation layer, and the core layer. The optical modules required by the existing optical network and the data center are not significantly different. The module can be upgraded by the module rate or WDM. capacity. The access layer will mainly adopt gray-light or color-light modules at rates of 25 Gbit/s, 50 Gbit/s, and 100 Gbit/s. The aggregation layer and above will use DWDM at rates of 100 Gbit/s, 200 Gbit/s, and 400 Gbit/s. Color light module.