With the use of 40G/100G ports servers, switches and other equipment in data center, the demand for high-speed optical interconnect products is also growing. Currently domestic manufacturers continue to develop and innovate optical interconnect technology, and have in-depth understanding and research on the high-speed integrated parallel optical module and high-frequency signal integrity technology.  The critical demand of optical interconnect product is high rate, high density, low cost and low power consumption. Now the mainstreamed optical interconnect products on the market include: 10Gbps SFP+ AOC、40Gbps QSFP+AOC、56G QSFP+AOC and 120Gbps CXP AOC etc.

Data center/cloud computing system is required urgently to greater bandwidth and lower power consumption. AOC is the one of the best solution to this requirement. Compared with the interconnect copper cable, AOC has a lot of outstanding advantages, for instance, the transmission power is lower on the system link, the weight is only a quarter of the direct attach copper cable, the volume is about half of the copper cable, and it has better heat dissipation performance on the system of machine room cabling. The bend radius of optical cable is smaller than copper cable, and has longer transmission distance which of up to 100-300 meters, and have a better transmission performance of BER which can reach 10^-15. Compared with optical transceiver, the stability and reliability of system have greatly improved, and reduced the maintenance cost, which for the reason of no exposed optical interface, optical interface cleaning and contaminated issues.

High-speed optical interconnect products: 40Gbps QSFP+ AOC and 120Gbps CXP AOC doesn’t adopt TOSA/ROSA structure design of the traditional pluggable transceiver, but use highly integrated array of optical engine core components technology.

Using COB (Chip on Board) integration technology on the PCBA to achieve integrated mode: little form factor, high rate, low power consumption (QSFP+ is less than 1.5W, CXP is less than 2.5W). At the transmitter, array of optical engine deal with multiple high-speed electrical channels simultaneously, turns it into multi-lane optical signal, and combines these optical signal together, then send the messages to cloud computing system and the next node of data center server room via a 12 core (24 core) MPO high density optical cable. At the receiver, array of optical engine turns the optical signal of MPO optical cable into electrical signal, and transmit the multi-lane electrical signal to the equipment to deal with. These products are totally applicable to infiniBand interconnection, and also compliant with Ethernet IEEE 802.3ba. In the field of data center and cloud computing system, array of optical engine technology is widely used in the interconnection between AOC products, servers and switches. However, array of optical engine technology also faces a great challenge: the core laser has being monopolized by a few international manufacturers that makes the price stay at a high level, and the driver and limiting of laser magnified welding technique between chipsets also affect the production efficiency and restrict the domestic manufacturers to promote significantly. For these reasons, integrated silicon photon technology is the future develop trend of optical interconnect technology-- the entire optical engine will be integrated in the silicon platform, combines all necessary functions to realize the lower cost, simpler production technology and build a higher density optical transmission system.

Due to the highly integrated array of optical engine will produce a lot of concentrated heat, having a good cooling capacity has become one of the difficulties of structural design for optical device manufacturers. Based on the thermodynamics theory, heat dissipation effect mainly depends on thermal conductivity of heat dissipation medium, the contact area of shell, cooling channel distance and material thermal resistance. Excellent performance cooling design needs to meet 3 requirements: high thermal conductivity (such as tungsten copper, 260W/mK), the maximum cross-section of the heat dissipation medium is directly contact with the shell, the shortest vertical distance of cooling channel to conduct heat, and makes products can work stably in 0~70 degrees environment for a long term. 

With the remarkable growth of cloud computing and data center, multi-channel test cost and efficiency of parallel optical module is facing severe challenges. Multi-channel parallel transmission platform can be simply considered as: the sum of 4 sets (QSFP+ products) or 12 sets (CXP products) of independent 10G test system, which means that need to invest a large amount of fund in the early stages of research and development and improve the threshold of entering the high-speed optical interconnect market. Therefore, multi-channel test platform with high efficiency, easy to use and low cost is the key factor to measure whether domestic and foreign manufacturers can really enter the optical interconnection camp. The whole set of integrated system will significantly shortened the period of product testing, so that to improve product quality and the utilization rate of equipment resources and space.

In the server room of data center, the equipment which provide the various high-speed optical communication ports (server, switches and HBA etc.) need to connect by cables to work together. So, how to solve the interconnection between any two equipment?  Such as 10G SFP+ and 40G QSFP+. The optical interconnect product of active optical cable QSFP+ to 4 * SFP+ AOC has become one of the best solution to achieve and solve the interconnection between QSFP+ and SFP+. The one interface of QSFP+ to 4 * SFP+ high-speed optical interconnect product is 40Gbps QSFP+, and another interface is 4 * 10Gbps SFP+, the two interface can be connected by a 12 core MPO high density optical cable, and then add a splitter to the MPO cable based on the needs of costumer for the cable length of two ends, so that to realize the 40G optical signal is divided into 4 * 10G SFP+ that compliant with SFF-8432, it is the most economical and simplest solution to achieve the switches ports conversion. For the transmission distance that can reach 1~100 meters, the optical cable length of two ends of splitter can be chosen freely. Similarly, the interconnect product of 120G CXP to 3 * 40G QSFP+ can solve the problem of the interconnection between CXP and QSFP, but it is need to be noted: Through the 24 core MPO high-density cable can be divided into three 4 core products to complete the perfect conversion.

The outstanding advantage of optical interconnect product makes it to be the focus of the data center integrator and equipment manufacturers. Extensive deployment of optical interconnect products is gradually become the develop trend of global big data, large density and large capacity data center and cloud computing.