#qsfp

Optical transceiver has developed to 400G optical transceiver, and manufacturers are stepping up research and development to seize the hot spot. Many mainstream manufacturers choose QSFP-DD as the package of 400 optical transceivers, but why do 400G optical transceivers prefer QSFP-DD? Does it mean that QSFP-DD will be the main package of 400G optical transceivers in the future?

A good packaging must first support the types of transmission media and optical transceivers that are widely used in the networking industry. The transmission media include passive direct connection copper cable (DAC), multimode fiber (MMF) and single-mode fiber (SMF). Optical transceivers, active copper cables, and active optical cables include the 100Gb /s, 200Gb/s, and 400Gb/s series defined by Ethernet, Fibre Channel, and InfiniBand standards. Furthermore, the port density of the new package should be the same as that of the already deployed network. Finally, the backward compatibility of the new package with the already widely used QSFP package is critical for industry adoption. The QSFP-DD optical transceiver is a package that meets all the above conditions.

I. The development history of QSFP-DD optical transceiver

On March 21, 2016, the plan to develop QSFP-DD high-speed interface was started.

On September 19, 2016, version 1.0 of the QSFP-DD hardware specification containing the drawings was released.

On March 13, 2017, version 2.0 of the QSFP-DD hardware specification and QSFP-DD white paper were released.

On September 19, 2017, version 3.0 of the QSFP-DD hardware specification was released, along with the CS Connector specification

On March 13, 2018, the QSFP-DD Thermal Design White Paper was released, addressing the issue of how to evaluate the thermal performance of the QSFP-DD module in a high-performance data center environment.

On August 30, 2018, it was announced that the QSFP-DD package had successfully passed the equipment interoperability test, and the QSFP-DD package optical transceiver was now ready for official use.

On 18 September 2018, version 4.0 of the QSFP-DD hardware specification and version 3.0 of the General Management Interface Specification for 8/16 Channel Placable Optical Modular were released.

So far, QSFP-DD MSA is relatively completed, and QSFP-DD optical transceivers of leading optical transceiver manufacturers were also listed in that period.

II. The application in the research and development of 400G optical transceiver

The QSFP-DD dual-density four-channel small pluggable package is a high-speed pluggable module package defined by the QSFP-DD MSA team as the preferred package for 400G optical transceivers, enabling data centers to effectively grow and expand cloud capacity as needed.

III. Characteristics of 400G QSFP-DD optical transceiver

The compatibility of the 400G QSFP-DD optical transceiver with the QSFP solution is one of its main advantages. The original QSFP28 module can still be used; you just need to insert another module.

In conclusion, the characteristics of the QSFP-DD optical transceiver package have unparalleled advantages in 400G applications (such as data center interconnection). It is expected that the world's leading ultra-large data center will soon deploy 400G, and QSFP-DD may become the mainstream package.

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What are the Categories of QSFP+ AOC?

FAQs of QSFP+ AOC

An active optical cable (AOC) has many advantages such as high transmission rate, long transmission distance, low energy consumption, and convenient use. It can replace passive optical cables or copper wire-based cable systems to be applied in high-density and high-bandwidth situations and has become the ideal transmission cables for data centers, consumer electronics and other fields.

However, active optical cables can be classified into various types according to different specifications and speeds, such as 200G QSFP-DD AOC, 100G/50G QSFP28 AOC, 56G/40G QSFP AOC, SFP28 AOC, and so on. So, what are their characteristics and what are their categories? This article will give a detailed introduction to QSFP+ AOC cable and its categories.

What is QSFP+ AOC?

QSFP+ AOC is an efficient integrated cable assembly product designed for short-distance multi-channel data communication and interconnection applications. Its communication distance ranges from 1 to 100 meters and it is suitable for supercomputers and SDR, DDR, QDR and other applications based on InfiniBand standards[1]. Moreover, active optical cables have more significant advantages over interconnected copper cables, such as lower transmission power on system links, only one-fourth of the weight of direct-connected copper cables, slightly half the volume of copper cables, better air flow and heat dissipation in the cabling system of the computer room, smaller bending radius, longer transmission distance, and lower bit error rate of the product transmission performance.

What are the Categories of QSFP+ AOC?

(1) 56G QSFP+ AOC

56G QSFP+ AOC: QSFP+ FDR active optical cable has a built-in 850nm VCSEL laser, PIN array, integrated driver and receiver chip. It supports the standards including InfiniBand FDR, 10G Ethernet, SAS2.0 and SAS3.0, 8G and 10G fibre channel. The transmission distance of OM3 optical fiber is 100 meters, and that of OM4 optical fiber is 150 meters. It is 100% perfectly compatible with a full range of brand servers, switches, routers, PDH/SDH transmission equipment, EPON, GPON, 10G EPON, 10G GPON and WDM PON base stations.

Its product features are as follows:

Full-duplex 4-channel 850nm active optical cable; transmission data rate of 14.0625gbit/s/channel; set trigger SFF-8436 QSFP+ compatible; hot-swappable electrical interface; 4-channel 850nm VCSEL array; 4-channel PIN photodetector array; OM3 multimode fiber (MMF) with a maximum link length of 100m and OM4 MMF of 150 meters; low-power shell and connector; 0°C + 70°C working temperature; 3.3 V power supply voltage; RoHS6.

56G QSFP+ AOC

(2) 40G QSFP+ to 4X10G SFP+ AOC

40G QSFP+ to 4X10G SFP+ AOC provides IT professionals with cost-effective host adapters, switches, and servers enabled by combining 40G QSFP and 10G SFP+.

For typical applications, users can install this breakout active optical cable between the QSFP ports on their 40Gbps rated switches and provide four upstream 10 gb/s-sfp+ enabled switches.

Each QSFP-SFP+ split active optical cable is characterized by a QSFP connector (sff-8436) at one end and SFP+ connector (SFF-8431), which are rated 40Gbps (SFF-8436), which is 10gb/s respectively.

The product features are as follows:

The electrical interface is compatible with QSFP+ connector (setting trigger-8436) and SFP+ connector (setting trigger-8431); hot pluggable; 850nm VCSEL transmitter, PIN laser detector; OM3 MMF up to 100m; operating temperature: 0-70℃; excellent EMI performance of all metal shell; RoHS6 (lead-free).

40G QSFP

(3) 40G QSFP+ AOC

40G QSFP+AOC is the core component to realize parallel optical interconnection. It consists of ribbon fiber jumpers connected to two high-speed 40G parallel connectors. Each signal direction has 4 data channels, and each channel can work at the speed of 10Gbps. Its transmission distance is generally 1 to 100m.

Advantages of 40G QSFP+ AOC:

Compared with traditional 40G copper cables, 40G active optical cables have incomparable advantages: high transmission efficiency, small size, light weight, and low energy consumption;

Compared with the optical transceiver, the AOC has no cleaning problem when the connector fails, and there is no need to test the terminal plug, which can help users save more time;

AOC QSFP has better cabling consistency and repeatability. The closed ends are easier to avoid the influence of environment and vibration. If there is a failure, it can be replaced directly, saving costs;

AOC is generally cheaper than optical transceivers. It can save deployment costs, and the transmission distance can also meet the requirements of a variety of short-distance transmission applications.

40G QSFP+ AOC

QSFP+ AOC is a mature and widely adopted interconnection solution for short-distance, high-bandwidth applications. With advantages such as low power consumption, lightweight design, easy installation, and high reliability, QSFP+ AOCs play a critical role in modern data centers and HPC environments.

By offering multiple configurations, such as 56G QSFP+ AOC, 40G QSFP+ AOC, and breakout QSFP+ AOC solutions, QSFP+ AOCs provide flexible options to meet diverse network architectures and performance requirements.

FAQs of QSFP+ AOC

What is QSFP+?

QSFP+ (QSFP full form is Quad Small Form-factor Pluggable) is a high-speed, hot-pluggable optical interface that supports four parallel data channels. Each channel can transmit up to 10 Gbps, enabling a total bandwidth of 40 Gbps. QSFP+ is widely used in data centers, high-performance computing, and InfiniBand-based systems for short- to medium-distance interconnections.

What are QSFP types?

QSFP-28: designed for use with 100G Ethernet applications

QSFP-DD: a double density version of the QSFP module, with increased connector density and higher data rates

QSFP56: supports speeds of up to 56Gbps per channel, suitable for high-speed data transmission applications

What fiber type is used in QSFP+ AOC cables?

QSFP+ AOCs typically use OM3 or OM4 multimode fiber (MMF). OM3 supports transmission distances up to 100 meters, while OM4 can extend the distance up to 150 meters, depending on the data rate and application.

Are QSFP+ AOCs hot-swappable?

Yes. QSFP+ active optical cables support hot-plugging, allowing installation or removal without powering down the system. This feature simplifies maintenance and improves operational efficiency.

Your network utilization report is clear: 40G is hitting its limit. The demands of AI, machine learning, and high-performance computing (HPC) are pushing your aggregation layer past its breaking point.

The decision to upgrade forces a crucial technical evaluation: Should you stick with the familiar 40G QSFP+ or make the leap to the far more efficient 100G QSFP28?

The Single Most Important Technical Shift

The QSFP family uses four parallel transmission lanes to achieve its speed. The entire comparison boils down to the efficiency of these lanes:

The 100G QSFP28 achieves five times the bandwidth of the old 10G SFP+ standard, and 2.5 times that of the QSFP+, without taking up a single millimeter more of valuable rack space.

Beyond Price Tag: The TCO Advantage of 100G

When dealing with hundreds of ports, the absolute price of a module is misleading. You must look at the Total Cost of Ownership (TCO), and here, the 100G QSFP28 wins decisively:

Lower Watts per Gigabit: Due to advanced chip design, 100G modules are dramatically more power-efficient per gigabit than 40G modules. This translates directly into reduced long-term electricity and cooling costs.

Superior Breakout Flexibility: The 100G module supports breaking out to 4 x 25G SFP28 connections. Since 25G is the current server access speed standard, a single 100G port can now service four high-speed servers, maximizing port utilization and simplifying design.

Future-Proofing: The QSFP28 electrical platform is the required foundation for the next generation of standards, like 200G and 400G QSFP-DD, ensuring a clear and affordable upgrade path.

Today, the 100G QSFP28 standard has reached cost maturity. When accounting for density, power savings, and future proofing, 100G is now often the cheaper solution on a cost-per-bit basis. Investing in 40G is investing in an obsolete standard.

Reliability and Cost Containment

Migrating to 100G does not require sacrificing reliability or budget. By utilizing high-quality, MSA-compliant transceivers from trusted partners like PHILISUN, you eliminate the financial barrier without compromising performance. We ensure every QSFP28 module is rigorously tested in real-world OEM equipment (Cisco, Arista, Juniper) for seamless integration and stable operation.

Ready to Make the Future-Proof Decision?

The shift to 100G QSFP28 is the necessary foundation for modern, scalable network architecture.

When building a high-performance, future-proof data center, the choice isn’t just about the switch; it’s about the module.

The Quad Small Form-factor Pluggable (QSFP) is the component that broke the networking speed barrier. Unlike its predecessor, the SFP, QSFP introduced the principle of parallel optics, fundamentally changing how we scale data density in the rack.

Why did QSFP become the universal standard, evolving from 40G to the imminent 800G? It’s not magic — it’s ingenious engineering designed to solve the two biggest challenges in modern networking: bandwidth and space.

The Engineering Breakthrough: Parallel vs. Single Lane

Before QSFP, SFP modules scaled bandwidth by increasing the speed of a single electrical lane (e.g., SFP28 runs at 25G per lane). This reached a physical limit quickly.

QSFP redefined this by packaging four independent transmit and receive channels into a compact module. This breakthrough allowed an immediate jump to 40G (4x10G) and 100G (4x25G QSFP28).

Deciphering the Double-Density Revolution: QSFP-DD

To reach speeds like 400G and 800G, engineers had to solve the puzzle of quadrupling density without physically expanding the module form factor.

The answer is QSFP-DD (Double Density).

The “DD” standard achieves 400G by a two-fold innovation:

Doubled Lanes: Increasing the total number of electrical and optical lanes from four to eight.

Dual Contact Rows: Adding a second, smaller row of physical contacts inside the switch interface.

This allows 8 lanes to run at 50G each (via PAM4 modulation), achieving 400G, while maintaining backward compatibility with older QSFP modules. This density is the key to scaling your spine-and-leaf architecture efficiently.

Deployment Demands: The MPO/MTP Mandate

The move to QSFP-DD is not just a module upgrade; it’s a necessary cabling infrastructure shift.

Because high-speed QSFP transceivers utilize parallel optics, the use of MPO/MTP multi-fiber assemblies becomes mandatory. These connectors are the only efficient way to manage the 8 or 16 fiber counts required for 400G/800G, ensuring signal integrity and drastically reducing complex, time-consuming on-site field termination.

The quality of your transceivers and the certified interoperability of your cabling are the two critical factors that will determine the scalability and total cost of ownership (TCO) of your next-generation network.

Ready to Master Your 400G/800G Deployment?

Understanding the engineering behind QSFP-DD, thermal management, and MPO/MTP deployment is the key to avoiding costly bottlenecks.