As the smallest package of 400g optical devices,qsfp-dd can provide high port density and can be backward compatible with qsfp+/qsfp28 package,which is popular with suppliers.Nowadays,many suppliers have launched 400g qsfp-dd products,such as 400g qsfp-dd optical module,400g qsfp-dd DAC/AOC,etc.What do you know about qsfp-dd encapsulation?This article will take you to re understand the qsfp-dd package and understand its differences from qsfp+/qsfp28/qsfp56 and OSFP/cfp8/Cobo packages.
Overview of qsfp-dd packaging
Qsfp-dd(also known as qsfp56-dd),which is a dual density four channel small pluggable package,is a new type of high-speed pluggable module package and conforms to ieee802.3bs and qsfp-dd MSA standards.The electrical interface of the package has 8 channels,and the data rate of each channel can reach 25gb/s through NRZ modulation technology,realizing 200g network transmission;Through pam4 modulation technology,the data rate of each channel can be as high as 50GB/s,realizing 400g network transmission,which is suitable for high-performance computing data centers and cloud networks.
The advantages of qsfp-dd are shown in the following aspects:
Backward compatibility,compatible with qsfp packages such as qsfp+/qsfp28/qsfp56;
Use 2×1 stacked integrated cage and connector,which can support single height and double height cage connector systems;
Using SMT connector and 1xn cage,cage design and optical module shell optimization can achieve a thermal capacity of at least 12 watts per module.A higher heat capacity can reduce the requirements of the optical module on the heat dissipation function,thereby reducing some unnecessary costs.
When designing qsfp-dd,MSA working group fully considered the flexibility of users,and adopted ASIC design,which supports multiple interface rates and is backward compatible(compatible with qsfp+/qsfp28),thus reducing the port cost and equipment deployment cost.
In short,qsfp-dd is a high-speed,small,pluggable and low-power package.It will become one of the mainstream packages of 400g.What is the difference between qsfp-dd and the previous qsfp+/qsfp28/qsfp56?How is it different from other 400g packages such as OSFP/cfp8/Cobo?
Differences between qsfp-dd and qsfp+/qsfp28/qsfp56
Although qsfp-dd and qsfp+/qsfp28/qsfp56 belong to the same qsfp package with the same size,there are still some differences between them.What are the differences between them?
In terms of structure,there are some differences between qsfp-dd and qsfp+/qsfp28/qsfp56 in the depth of the mechanical interface of the main board,the number of channels of the electrical interface and the number of integrated circuits.The details are as follows:
Depth of mechanical interface on the main board-when designing qsfp-dd,MSA team members designed the mechanical interface on the main board to make qsfp-dd have the same port density as qsfp+/qsfp28/qsfp56 and can accommodate an additional row of contacts.The mechanical interface on the main board is slightly deeper than that of qsfp+/qsfp28/qsfp56.
Number of channels of electrical interface-it can be seen from the above that qsfp-dd package is equipped with 8-channel electrical interface.Compared with qsfp+/qsfp28/qsfp56 package with 4-channel electrical interface,the number of channels of electrical interface is doubled,which is also attributed to a row of additional contacts in qsfp-dd package.
Number of integrated circuits-although the size of qsfp-dd is the same as that of qsfp+/qsfp28/qsfp56,since qsfp-dd has 8-channel electrical interfaces,the number of integrated circuits(i.e.,ASICs)and density of qsfp+/qsfp28/qsfp56 with 4-channel electrical interfaces have been doubled.
It can be seen from the above that the maximum bandwidth of qsfp-dd can reach 400gbps,while the maximum bandwidth of qsfp+/qsfp28/qsfp56 can only reach 40Gbps/100gbps/200gbps respectively.Qsfp-dd is much higher than qsfp+/qsfp28/qsfp56.For this reason,qsfp-dd is generally used as the package of 400g optical modules and 400g high-speed cables(i.e.DAC and AOC)for the interconnection of 400g data centers to solve the problem of high-speed migration of massive data between data centers;While qsfp+/qsfp28/qsfp56 are respectively used for the packaging of 40g/100g/200g optical modules and high-speed cables,and for the interconnection of 40g/100g/200g networks.
Qsfp-dd has backward compatibility and supports modules or connectors encapsulated by existing qsfp+/qsfp28/qsfp56 to be inserted into the ports of qsfp-dd;However,qsfp+/qsfp28/qsfp56 ports cannot support modules or connectors packaged with qsfp-dd.