A DAC high-speed cable (Direct Attach Cable) is generally translated as direct cable or direct-attached copper cable. It is usually a fixed-length cable assembly with fixed connectors at both ends, with ports not being able to be replaced and module heads and copper cables not being able to be separated. High-speed cables are accepted and used by more and more users due to their significant advantages such as high price-quality ratio, high performance, high speed, high composite, and low loss. They have become the first choice for high-speed data communication solutions. And they are widely used in storage area’s networks, data center and the connection between high-performance computers.

A It has become a preferred solution for users in short-distance application scenarios. It is widely used in data center’s interconnection scenarios such as SATA storage devices, RADI system scenarios, core routers, 10G or 40G Ethernet, etc.. In data centers, copper cables are generally used to connect servers and storage area’s networks.  The most commonly used is Direct Attach Copper Cable (DAC), and among which passive copper cables are most particularly used. Since passive copper cables are of low price and of fast transmission speed, they have become the best solution for short-distance transmission. For example, 40G QSFP+ passive cable is one of passive copper cables. Because of its low power consumption, high efficiency, low cost and low latency, it is widely used in 40G LAN, HPC and SAN. And 40G QSFP+ passive cable is also suitable for flexible wiring; we can say that 1 SFP+ high-speed cable is equal to 2 SFP+ 10 Gigabit optical modules and 1 pair of OM3 10 Gigabit fiber jumpers.
 

A Our DAC high-speed cable mainly takes silver-plated conductors and foamed insulated core wires as materials while some manufacturers use special PTFE films instead of insulating materials, foamed PE. Because this cable has high requirements for materials and processes, there are currently very few manufacturers that can produce them. The method of shielding and total shielding make our high-speed cables have excellent attenuation performance, low delay and anti-interference, and have the capability of realizing high-frequency broadband transmission. Our high speed cables range from 30AWG to 24AWG, with various structures such as 2P, 4P or 8P. And it can be used in many different applications.

A 400ZR, also known as 400G ZR, is a specification defined by the Optical Internetworking Forum (OIF). The specification uses a combination of the plans of Dense Wavelength Division Multiplexing (DWDM) and high-order modulation. Due to 400ZR, 400G can be transmitted on the  interconnect (DCI) link of the data center. Its purpose is to ensure long-term and stable implementation based on single carrier 400G. This single carrier uses complex polarization multiplexing’s 16-level quadrature amplitude modulation (DP-16QAM) with a rate of approximately 60 Gbaud.

A SFP optical module is an interface device that converts gigabit electrical signals into optical signals. Our SFP optical module is an industry-standard small and pluggable gigabit optical transceiver module which can be plugged into the SFP ports of network equipment such as switches, routers, and media converters. It can be used to connect optical or copper network cables for data transmission. Usually we can find it in Ethernet switches, routers, firewalls and network interface cards.

A Structure
In terms of structure, QSFP-DD and QSFP+/QSFP28/QSFP56 have some differences in depth of mechanical interface of motherboard, number of channels of electrical interface, and number of integrated circuits.

Depth of Mechanical Interface of Motherboard - When MSA team members are designing QSFP-DD, the mechanical interface on the motherboard is slightly deeper than the ones of QSFP+ /QSFP28/QSFP56 in order to make QSFP-DD and QSFP+/QSFP28/QSFP56 have the same port density and have the capability of accommodating an extra row of contacts.

The Number of Channels of the Electrical Interface -- as can be seen from the above, the QSFP-DD’s package is equipped with an 8-channel electrical interface. Compared with the QSFP+/QSFP28/QSFP56 package with a 4-channel electrical interface, the number of channels of the electrical interface is doubled, which is also due to the reason that QSFP - DD package has an extra row of contacts.

Number of Integrated Circuits—Although QSFP-DD has the same size as QSFP+/QSFP28/QSFP56, compared with QSFP+/QSFP28/QSFP56 with 4-channel electrical interface, the number of integrated circuits(i.e. ASIC) and density are doubled since QSFP-DD has 8-channel electrical interfaces.

Bandwidth & Application
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. The maximum bandwidth of QSFP-DD is much higher than the ones of QSFP+/QSFP28/QSFP56. Because of this, QSFP-DD is generally used as a package for 400G optical modules and 400G high-speed cables (i.e. DAC and AOC), is applied for the interconnection of 400G data center and to solve the problem of high-speed migration of massive data between data centers; and QSFP+/QSFP28/QSFP56 are respectively used for the packaging of 40G/100G/200G optical module and high-speed cable and for 40G/100G/200G network interconnection.

A With strong flexibility, the SFP port is a hot-swappable I/O interface (refers to input/output interface). It is suitable for a variety of products, for example, it can be switched with 1000BASE-SX, 1000BASE-LX/LH, 1000BASE-ZX or 1000BASE-BX10-D/U ports. Besides, the SFP port is backward compatible, supporting 10/100/1000Mbps.

A IDC (Internet Data Center) , i.e. the Internet data center, is not only the center of data storage, but also the center of data circulation. It is mainly applied in the places where data exchange is most concentrated. Therefore, IDC computer room refers to a place where some network operators or government enterprises store servers and provide IT services to their users or employees.

The most common equipment in the IDC computer room includes cabinets (rack), KVM switches, access/aggregation switches, routers, fiber jumpers, network jumpers, cable management/distribution frames, etc.. And these equipment are used to connect customers and servers.

A The 100G QSFP28 optical module is suitable for 100G Ethernet, EDR InfiniBand and 32G Fibre Channel. Generally, it has exactly the same volume and panel density as 40G QSFP+. 40G QSFP+ uses 4 10Gbps channels, which is of similarity of 100G QSFP28 module. 100G QSFP28 module uses 4 high-speed differential signal channels, and its data rate supports 25Gbps, up to 40Gbps. In addition, QSFP28 has an upgraded electrical interface that can support signals up to 28Gbps. QSFP28 SR4, QSFP28 LR4, QSFP28 PSM4, QSFP28 CWDM4, QSFP28 ER4. Compared with other package types of 100G optical modules (CFP/CFP2/CFP4), 100G QSFP28 has higher density, lower power consumption and lower price which is an obvious advantage.