1. What is an optical module? The optical module is composed of optoelectronic devices, functional circuits and optical interfaces, etc. The optoelectronic devices include two parts: transmitting and receiving. To put it simply, the function of the optical module is to convert the electrical signal into an optical signal at the sending end, and then convert the optical signal into an electrical signal at the receiving end after transmission through the optical fiber.

Commonly divided into single-mode optical modules and multi-mode optical modules, the former is suitable for long-distance transmission, and the latter is mostly suitable for short-distance transmission. Today we will not talk too much about the types and working principles of optical modules, but will focus on the application scenarios of optical modules

2. Several application scenarios of optical modules

2.1 Data Center Interconnection Scenario

With the Internet of Everything becoming the social norm, data centers, especially large data centers in the form of clusters, are rising rapidly. In addition to realizing the high-speed operation and stable support of Internet terminal services, the interaction between data centers is also very important, creating a new Scenario: DCI (Data Center Interconnect).

This concept was born in recent years. With the rapid development of many emerging services such as cloud computing, big data, and VR, many applications that rely heavily on data centers are experiencing explosive growth. A single data center is overwhelmed and quickly runs out of resources. A single data center cannot easily expand capacity due to site and energy supply issues. At this time, multiple data centers are built in the same city or in different places, and the support for interconnection and collaborative business completion between them has become a new option.

In addition, more and more enterprises are undergoing digital transformation, and enterprises in the same industry need to share and collaborate at the data level, which also prompts the interconnection between data centers of different enterprises.

Going back to our optical modules, in the data center interconnection scenario, data centers need to realize massive information interaction. In this case, both the amount of information and the transmission frequency will be larger and denser, and the distance will be farther than a single data center. Then, optical fiber communication advantages stand out.

In addition, the data center interconnection scenario requires switching devices with higher speed, lower power consumption, and smaller size, and one of the core factors that determines whether these performances can be realized is the optical module.

The data traffic in the data center continues to grow, and the trend of large-scale and flattening between data centers is also gradually promoting the development of optical modules to a faster transmission rate. The transmission distance of multimode fiber is limited by the increase in signal rate, so it will gradually be replaced by single-mode fiber in data center interconnection scenarios. At present, China has gradually evolved from 100G-400G to 400-800G, and the application of single-mode optical fiber may become higher and higher.

2.2 Telecom market: 5G deployment will greatly increase the demand for optical modules

The 5G network is divided into three parts: access network, bearer network and core network. The bearer network is generally divided into the metro access layer, the metro aggregation layer, the metro core layer/provincial trunk line, and the fronthaul and midhaul functions of real-line 5G services. Compared with 4G, 5G has undergone some changes compared with 4G base stations. The link of mid-transmission has been added, and the market for mid-transmission optical modules has been opened since then. In addition, in the fronthaul and backhaul of 4G, the optical modules used do not have such high requirements on the transmission rate, and the 10G optical modules are used, while the characteristics of high bandwidth, low delay, and large connection possessed by 5G wireless communication have great impact on optical modules. The function and performance of the module put forward higher requirements. The future needs and requirements of 25G, 50G, and even more 100G optical modules will be greatly improved.

2.3 Passive WDM We have talked about the technical principle of wavelength division multiplexing before. The core principle of this passive wavelength division technology is to use WDM technology to couple optical signals with different wavelengths and carrying a series of information into a bundle and transmit them in an optical fiber. In order to realize the transmission between services. The optical signals of these different wavelengths can be separated at the receiving end. At present, many applications are deployed in the campus network. While ensuring high-speed and low-latency transmission, it can also greatly improve the utilization rate of backbone optical cables. At the same time, it can greatly reduce network operation and maintenance management through passive combiners. WDM is composed of color light module (commonly referred to as coarse wavelength division module, and dense wavelength division module is called color light module, usually using dual-fiber module) and passive components.

The transmit and receive wavelengths in the color light module indicators will have a nominal center frequency/center wavelength; the gray light module has a wide range of transmit and receive wavelengths without a center wavelength. Therefore, it can be judged by whether there is a center wavelength in the index.

CWDM optical modules are widely used in Gigabit Ethernet and point-to-point networks; DWDM optical modules are mainly used in large network environments such as metropolitan area networks and local area networks.

3. Summary Nowadays, many scenes in our current daily work and life have realized "light into copper back", that is to say, the metal medium in transmission has been gradually replaced by the optical fiber medium, and optical communication has become a trend. The optical module is the core device of optical communication, and its strategic significance is self-evident. In the future, with the acceleration of 5G network construction, the rapid development of cloud computing and the batch construction of large-scale data centers, 400G-800G will become the main competition direction of the optical communication industry.