Development of High-Speed Optical Modules

With the rapid development of information technology, the information capacity of optical communication networks has surged. At the same time, the application of optical communication technology in wireless communication, short-distance high-speed interconnection, such as high-performance computers, board interconnection, etc. has become more and more extensive. The high-speed broadband optical transceiver module is the core device in the optical communication system and network, and the related technology is a research hotspot in the field of optical communication systems and network technology. Achieving ultra-high-speed, increasing integration, reducing volume and power consumption, reducing cost, and improving reliability have always been the mainstream direction of optical module development.

Optical module structure

Optical modules take optical devices as the core and add some circuit parts and structural components to complete the corresponding functions. According to their functions, they can be divided into three categories: transmitter modules, receiver modules, and transceiver modules. The optical transceiver module technology has gone through the development process from the transceiver alone to the transceiver integration. The transceiver integrated optical module technology includes transmitting, receiving, various functional circuits, standardized optical fiber connectors, and electrical signal interface technology, forming a highly integrated system. module.

The high-speed broadband optical transceiver module is the core component that realizes optical signal processing and constitutes various miniaturized and highly integrated on-chip photonic systems and optical networks. The intermediate transmission uses light to transmit in the optical fiber. The optical transceiver module consists of three parts: optoelectronic devices, electronic functional circuits, and optical interfaces. Internally it can be divided into two independent parts: receive and transmit. The receiving part realizes the optical-electrical conversion, and the transmitting part realizes the electric-optical conversion.

The optical transmission part is composed of the interface, light source, drive circuit, official business, and monitoring circuit, automatic bias control circuit, temperature control circuit, and so on.

The light-receiving part consists of a photodetector, a low-noise preamplifier, and other signal processing circuits. Compared with the analog receiver, the digital receiver is more complicated, and there are equalization filtering, timing extraction, decision regeneration, peak detection, and automatic gain control amplification after the main amplifier.

The optical transmitter and receiver are integrated inside the optical module, and the SFP+ optical transceiver module is composed as shown in the following figure:

Development trend of high-speed optical modules

Due to the development of information technology, various new technologies and new systems used in optical fiber communication systems are constantly updated and rapidly developed. In order to meet different needs, optical modules are constantly developing from low speed to high speed.

In the transmission development of 100/Gigabit Ethernet and SDH (Synchronous Digital Hierarchy) network, the development of optical modules has mainly gone through the following processes: First, the 1×9 package, which was first produced in 1999. , SC (Square Connector) interface, used as a fixed optical module; then SFF (Small Form Factor) package, which is currently widely used in ONU (Optical Network Unit) in EPON (Ethernet Passive Optical Network) systems; followed by GBIC (Gigabit Interface Converter) package, GBIC is a Gigabit Ethernet interface converter, switching and routing products have widely used GBIC modules, which can support hot-swappable features; Pluggable), SFP can be understood as an upgraded version of GBIC. Although the SFP optical module product is the latest optical module of 100/Gigabit Ethernet, it is also the most widely used optical module product at present, inheriting the hot pluggability of GBIC. , and also draws on the advantages of SFF miniaturization.

In the transmission process of 10Gbps Ethernet, the main development process of optical modules: firstly 300pin, then XENPAK (10 Gigabit Small Form-factor Pluggable), followed by XENPAK’s directly improved version X2 (only as a transition); Then came the smaller, cheaper XFP (10 Gigabit Small Form Factor Pluggable); and finally SFP+. Both XFP and SFP+ are 10G optical fiber modules, which can communicate with other 10G modules. SFP+ and SFP have the same size and have strong compatibility. Therefore, the SFP+ packaging mode is the mainstream of 10G optical modules.

For 40GE/100GE high-speed optical modules, the development trend is shown in the figure below. It shows the development trend of 40GE/100GE high-speed optical modules in recent years. The mainstream 100G broadband modules are packaged in the CFP module series and the latest QSFP+ modules. Optical modules are developing rapidly in the direction of high speed, low power consumption, miniaturization, and hot swappability.