AOC Cable vs DAC Cable: Which is Better for You

Direct Attach Cables (DAC) and Active Optical Cables (AOC) are the two important cabling solutions in regard to interconnections in the data center and enterprise networks. Both AOCs and DACs are plug-and-play, allowing the users to optimize the existing network without a new optical fiber cabling. But the question is in what situation you should use DAC or AOC cable? What are the advantages and disadvantages of the two types of network cables? The following part of this article will make a brief explanation of these questions.

10G, 25G, 40G, 100G, 400G DAC AOC Cable for servers, TOR switches and core swithces in data centers

 

DAC & AOC Cable Solutions for IDC High-Speed Interconnect 

1. What DO DAC and AOC Cables Have in Common?

Both DAC and AOC are common cabling solutions for data networking and are usually used for high-speed, high-reliability interconnection and transmission required by data centers, high-performance computers, and large-capacity storage devices. Both of their ends have cable assemblies with factory terminated transceivers, which are connected to fixed ports only. Besides, DAC and AOC cables can be manufactured in different lengths to support different transmission data rates, such as 10G SFP DAC/AOC cable, 25G AOC cable, 40G DAC cable, and 100G AOC cable.

2.  Pros and Cons of DAC Cable 

● Pros of Direct Attach Copper Cable

More Cost-effective— Generally speaking, the price of copper cables is much lower than that of optical fibers. The cost of passive copper cables is 2 to 5 times cheaper than fiber cables of the same length. Therefore, the use of high-speed cables will also reduce the cabling costs of the entire data center.

Lower Power Consumption— High-speed DAC (direct attach cable) consumes less power(the power consumption is almost zero) since passive cables do not require a power supply. The power consumption of active copper cables is generally around 440mW. If you use direct attach copper cables instead of AOC fiber cables, you can save hundreds of thousands of kilowatts of electrical power.

It is more durable–It is designed with a seamless connection form of optical module and optical cable, which reduces the cost and ensures that the optical port is not exposed to dust and other pollutants. Therefore, DAC is less susceptible to damage. 

 


Fiber Mall 10G SFP+ DAC Cable and 10G SFP+ Fiber Optic Transceiver

 

Cons of Direct Attach Copper Cable

One of the disadvantages of DAC cable is that it is heavier and bulkier than AOCs. In addition, it is more susceptible to the effect of electromagnetic interference and attenuation over longer distances due to the electrical signals transmitted between both ends.  

3. Pros and Cons of AOC Cable

● Pros of AOC

Lighter weight-An active optical cable is composed of two optical transceivers and a fiber optic patch cable, whose weight is only a quarter of the direct attach copper cable, and the bulk is about half of the copper cable.

Longer distances-AOC fiber can provide a greater and longer transmission reach up to 100-300m due to its better heat dissipation in the computer room’s wiring system and smaller bending radius of optical cable.

More Reliable– Active optical cable is less vulnerable to electromagnetic interference since optical fiber is a kind of dielectric that can sustain a static electric field within it. The bit error rate of the product transmission performance is also better, and the BER can reach 10^-15.

Fiber Mall QSFP28 100G AOC Cable

Fiber Mall QSFP28 100G AOC Cable

  

● Cons of AOC

The main defect of AOC active fiber cables is that it is a more expensive cabling assembly solution for high-density data center operators. Besides, AOCs are less durable if not managed properly since they are lighter and thinner AOCs are much lighter and thinner which makes them more susceptible to damage if not handled correctly. 

4. When do you Use DAC Cables?

According to the fabric architecture announced by Facebook, a server and Top-of-Rack switches(ToR) constitute the basic unit of the data center. Generally speaking, the distance between a ToR and a server NIC(Network Interface Card) is less than 5 meters. In this situation, DAC cable is more advantageous than AOC cables in the respects of cost, power consumption, and heat dispersion. Thus, DAC is a preferred option for IDC interconnect systems. Besides, on some special occasions, 100G QSFP28 to 4*SFP28 DAC is an alternative direct connection according to the users specific demand for the data connection.

Fiber Mall QSFP28-4*QSFP28 100G Passive DAC  

◮ Fiber Mall QSFP28-4*QSFP28 100G Passive DAC  

5. When do you use AOC Cables?

Nevertheless, the transmission distance between ToRs and edge core switches is usually less than 100m, where Integrated circuits are deployed densely. Therefore, the active optical cable is a better cabling solution for data connection due to its merits of lightweight, small wire diameter, and manageable cabling maintenance. Since the data center has strict specifications on signal transmission, active optical cable is better than twin-ax DAC cable in signal integrity and optical coupling design, greatly reducing the errors in signal processing. Furthermore, the high-frequency EMI signal is processed within pluggable optical modules, AOC fiber cable has a better EMI performance than the DAC cable. Undoubtedly, AOC cable is your first option in the interconnection between switches and switches within short or intermediate reach.

6. Popular DAC products

(1) 10G SFP+ Direct Attach Cable (DAC)

General Description

SFP+ Direct Attach Cables are compliant with SFF-8432 and SFF-8402 specifications. Various choices of wire gauge are available from 30 to 24 AWG with various choices of cable length (up to 7m).

FiberMall's 10G SFP+ DAC

FiberMall’s 10G SFP+ Direct Attach Cable (DAC)

Features

  • Up to 3125Gbps data rate
  • Up to 7-meter transmission
  • Hot-pluggable SFP 20PIN footprint
  • Improved Pluggable Form Factor(IPF) compliant for enhanced EMI/EMC performance
  • Compatible to SFP28 MSA
  • Compatible with SFF-8402 and SFF-8432
  • Temperature Range: 0~ 70 °C
  • RoHS Compatible

Benefits

  • Cost-effective copper solution
  • Lowest total system power solution
  • Lowest total system EMI solution
  • Optimized design for Signal Integrity

Applications

  • 10G Ethernet

 Product Description

The SFP+ passive cable assemblies are high-performance, cost-effective I/O solutions for 10G Ethernet. SFP+ copper cables allow hardware manufacturers to achieve high port density, configurability, and utilization at a very low cost and reduced power budget

 

(2) 25G SFP28 Direct Attach Cable (DAC)

General Description

SFP28 Direct Attach Cables are compliant with SFF-8432 and SFF-8402 specifications. Various choices of wire gauge are available from 30 to 26 AWG with various choices of cable length (up to 5m).

FiberMall's 25G SFP28 Direct Attach Cable (DAC)

FiberMall’s 25G SFP28 Direct Attach Cable (DAC)

Features

  • Up to 25.78125 Gbps data rate
  • Up to 5-meter transmission
  • Hot-pluggable SFP 20PIN footprint
  • Improved Pluggable Form Factor(IPF) compliant for enhanced EMI/EMC performance
  • Compatible with SFP28 MSA
  • Compatible with SFF-8402 and SFF-8432
  • Temperature Range: 0~ 70 °C
  • RoHS Compatible

Benefits

  • Cost-effective copper solution
  • Lowest total system power solution
  • Lowest total system EMI solution
  • Optimized design for Signal Integrity

Applications

  • 25G Ethernet

Product Description

  • The SFP28 passive cable assemblies are high-performance, cost-effective I/O solutions for 25G Ethernet. SFP28 copper cables allow hardware manufacturers to achieve high port density, configurability, and utilization at a very low cost and reduced power budget

(3)40G QFP+ to 4xSFP+ Breakout Direct Attach Cable

General Description

QSFP+ Direct Attach Cables are compliant with the SFF-8436 specifications.   SFP+ Direct Attach Cables are compliant with the SFF-8431, SFF-8432, and SFF-8472 specifications. Various choices of wire gauge are available from 30 to 24 AWG with various choices of cable length(up to 7m).

FiberMall's QSFP-4SFP-PCFiberMall’s QSFP-4SFP-PC

Features

  • Compliant with SFF- 8436, SFF-8431, SFF-8432 and SFF-8472
  • Up to 3125Gbps data rate per channel
  • Up to 7m transmission
  • Operating temperature:0℃ to +70℃
  • Single3Vpower supply
  • RoHS compliant

Benefits

  • Cost-effective copper solution
  • Lowest total system power solution
  • Lowest total system EMI solution
  • Optimized design for Signal Integrity

Applications

40G Ethernet

(4)40G QSFP+ Direct Attach Cable

General Description

QSFP+ Direct Attach Cables are compliant with the SFF-8436 specifications. Various choices of wire gauge are available from 30 to 24 AWG with various choices of cable length (up to 7m).

FiberMall's 40G QSFP+ Direct Attach Cable

FiberMall’s 40G QSFP+ Direct Attach Cable

Features

  • Compliant with SFF- 8436.
  • Up to 10.3125Gbps data rate per channel
  • Up to 7m transmission
  • Operating temperature: 0℃ to +70℃
  • Single 3.3V power supply
  • RoHS compliant

Benefits

  • Cost-effective copper solution
  • Lowest total system power solution
  • Lowest total system EMI solution
  • Optimized design for Signal Integrity

Applications

40G Ethernet

(5)100G QSFP28-2QSFP28 DAC

General Description

QSFP28 passive copper cable assembly feature eight differential copper pairs, providing four data transmission channels at speeds up to 25Gbps per channel, and meets 100G Ethernet and InfiniBand Enhanced Data Rate(EDR) requirements. Available in a broad range of wire gages-from 26AWG through 30AWG-this 100G copper cable assembly features low insertion loss and low cross talk.

Designed for applications in the data center, networking, and telecommunications markets that require a high-speed, reliable cable assembly, this next-generation product shares the same mating interface with the QSFP+ form factor, making it backward compatible with existing QSFP ports.

Features and Benefits

  • Compatible with IEEE 802.3bj
  • In accordance with the paging function in the protocol SFF-8636, paging can be selected 00H or 02H in 127 bytes
  • Supports aggregate data rates of 100Gbps
  • Optimized construction to minimize insertion loss and cross talk
  • Backward compatible with existing QSFP+ connectors and cages
  • Pull-to-release slide latch design
  • 26AWG through 30AWG cable
  • Straight and break out assembly configurations available
  • Customized cable braid termination limits EMI radiation   
  • Customizable EEPROM mapping for cable signature
  • RoHS compliant

Product   Applications

  • Switches, servers, and routers
  • Data Center networks
  • Storage area networks
  • High-performance computing
  • Telecommunication and wireless infrastructure
  • Medical diagnostics and networking
  • Test and measurement equipment

Industry  Standards

  • 100G Ethernet(IEEE 802.3bj)
  • InfiniBand EDR  

Technical  Documents

  • 108-32081 QSFP28  Copper  Module  Direct  Attach  Cable  Assembly

(6) 100G QSFP28 to 4xSFP28 Breakout Direct Attach Cable

General  Description

  • QSFP28 passive copper cable assembly feature eight differential copper pairs, providing four data transmission channels at speeds up to 28Gbps per channel and meets 100G Ethernet,25G Ethernet, and InfiniBand Enhanced Data Rate(EDR) requirements. Available in a broad range of wire gages-from 26AWG through 30AWG-this 100G copper cable assembly features low insertion loss and low cross talk.
  • Designed for applications in the data center, networking, and telecommunications markets that require a high-speed, reliable cable assembly, this next-generation product shares the same mating interface with the QSFP+ form factor, making it backward compatible with existing QSFP ports.QSFP28 can be used with current 10G and 14G applications with a substantial signal integrity margin.

FiberMall's 100G QSFP28 to 4xSFP28 Breakout Direct Attach Cable

FiberMall’s 100G QSFP28 to 4xSFP28 Breakout Direct Attach Cable

Features  and Benefits

  • Compatible with IEEE 802.3bj, IEEE 802.3by, and InfiniBand EDR
  • Supports aggregate data rates of 100Gbps
  • Optimized construction to minimize insertion loss and cross talk
  • Backward compatible with existing QSFP+ connectors and cages
  • Pull-to-release slide latch design
  • 26AWG through 30AWG cable
  • Straight and break out assembly configurations available
  • Customized cable braid termination limits EMI radiation   
  • Customizable EEPROM mapping for cable signature
  • RoHS compliant

Product   Applications

  • Switches, servers, and routers
  • Data Center networks
  • Storage area networks
  • High-performance computing
  • Telecommunication and wireless infrastructure
  • Medical diagnostics and networking
  • Test and measurement equipment

Industry  Standards

  • 100G Ethernet(IEEE 802.3bj)
  • 25G  Ethernet(IEEE 802.3by)
  • InfiniBand EDR
  • SFF-8665   QSFP+  28G  4X Pluggable  Transceiver  Solution(QSFP28)
  • SFF-8402 SFP+ 1X 28Gb/s Pluggable Transceiver  Solution(SFP28)

Technical  Documents

  • 108-32081 QSFP28  Copper  Module  Direct  Attach  Cable  Assembly
  • 108-2364  Single  Port and Ganged  SFP+ Cages, Zsfp+  Single  Port and Ganged Cages, and SFP+  Copper Direct Attach Cable Assemblies.

(7) 100G QSFP28 Direct Attach Cable(DAC)

General Description

QSFP28 Direct Attach Cables are compliant with the SFF-8665 specifications. Various choices of wire gauge are available from 30 to 26 AWG with various choices of cable length (up to 5m).

FiberMall's QSFP28-100G-PC5M

FiberMall’s QSFP28-100G-PC

Features

  • Compliant with SFF- 8665
  • Up to 3125Gbps data rate per channel
  • Up to 5m transmission
  • Operating temperature:0~70℃
  • Single3Vpower supply
  • RoHS compliant

Benefits

  • Cost-effective copper solution
  • Lowest total system power solution
  • Lowest total system EMI solution
  • Optimized design for Signal Integrity

Applications

  • 100G Ethernet

(8) 200G QSFP56 Direct Attach Cable – PAM4

General  Description

  • QSFP56 passive copper cable assembly feature eight differential copper pairs, providing four data transmission channels at speeds up to 56Gbps(PAM4) per channel and meets 200G Ethernet and InfiniBand  Data Rate(EDR) requirements. Available in a broad range of wire gages-from 26AWG through 30AWG-this 200G copper cable assembly features low insertion loss and low cross talk.
  • QSFP56 uses PAM4 signals for transmission, which doubles the rate. However, there are more stringent requirements for cable insertion loss. For detailed requirements, please see High-Speed Characteristics.
  • Designed for applications in the data center, networking, and telecommunications markets that require a high-speed, reliable cable assembly, this next-generation product shares the same mating interface with the QSFP+ form factor, making it backward compatible with existing QSFP ports.

FiberMall's QSFP56-200G-PC3M

FiberMall’s QSFP56-200G-PC

Features  and Benefits

  • Compatible with IEEE 802.3bjand IEEE 802.3cd
  • In accordance with the paging function in the protocol SFF-8636, paging can be selected 00H or 02H in 127 bytes
  • Supports aggregate data rates of 200Gbps(PAM4)
  • Optimized construction to minimize insertion loss and cross talk
  • Backward compatible with existing QSFP+ connectors and cages
  • Pull-to-release slide latch design
  • 26AWG through 30AWG cable
  • Straight and break out assembly configurations available radiation
  • Customized cable braid termination limits EMI radiation
  • Customizable EEPROM mapping for cable signature
  • RoHS compliant

Product   Applications

  • Switches, servers, and routers
  • Data Center networks
  • Storage area networks
  • High-performance computing
  • Telecommunication and wireless infrastructure
  • Medical diagnostics and networking
  • Test and measurement equipment

Industry  Standards

  • 200G Ethernet(IEEE 802.3cd)
  • InfiniBand EDR

Technical  Documents

  • 108-32081 QSFP28Copper  Module  Direct  Attach  Cable  Assembly

(9) 200G QSFP56 to 2XQSFP56 100G Breakout Direct Attach Cable – PAM4

General  Description

  • QSFP56 passive copper cable assembly feature eight differential copper pairs, providing four data transmission channels at speeds up to 56Gbps(PAM4) per channel and meets 200G Ethernet and InfiniBand Enhanced Data Rate(EDR) requirements. Available in a broad range of wire gages-from 26AWG through 30AWG-this 200G copper cable assembly features low insertion loss and low cross talk.
  • QSFP56 uses PAM4 signals for transmission, which doubles the rate. However, there are more stringent requirements for cable insertion loss. For detailed requirements, please see High-Speed Characteristics.
  • Designed for applications in the data center, networking, and telecommunications markets that require a high-speed, reliable cable assembly, this next-generation product shares the same mating interface with the QSFP+ form factor, making it backward compatible with existing QSFP ports.

FiberMall's 200G QSFP56 to 2XQSFP56 100G Breakout Direct Attach Cable

FiberMall’s 200G QSFP56 to 2XQSFP56 100G Breakout Direct Attach Cable

Features  and Benefits

  • Compatible with IEEE 802.3bjand IEEE 802.3cd
  • In accordance with the paging function in the protocol SFF-8636, paging can be selected 00H or 02H in 127 bytes
  • Supports aggregate data rates of 200Gbps(PAM4)
  • Optimized construction to minimize insertion loss and cross talk
  • Backward compatible with existing QSFP+ connectors and cages
  • Pull-to-release slide latch design
  • 26AWG through 30AWG cable
  • Straight and break out assembly configurations available
  • Customized cable braid termination limits EMI radiation   
  • Customizable EEPROM mapping for cable signature
  • RoHS compliant

Product   Applications

  • Switches, servers, and routers
  • Data Center networks
  • Storage area networks
  • High-performance computing
  • Telecommunication and wireless infrastructure
  • Medical diagnostics and networking
  • Test and measurement equipment

Industry  Standards

  • 200G Ethernet(IEEE 802.3cd)
  • InfiniBand EDR  

Technical  Documents

  • 108-32081 QSFP28Copper  Module  Direct  Attach  Cable  Assembly

(10) 400G QSFP-DD Direct Attach Cable – PAM4

General  Description

  • QSFP-DD passive copper cable assembly feature eight differential copper pairs, providing four data transmission channels at speeds up to 56Gbps(PAM4) per channel and meets 400G Ethernet and InfiniBand Enhanced Data Rate(EDR) requirements. Available in a broad range of wire gages-from 28AWG through 30AWG-this 400G copper cable assembly features low insertion loss and low cross talk.
  • QSFP-DD uses PAM4 signals for transmission, which doubles the rate. However, there are more stringent requirements for cable insertion loss. For detailed requirements, please see High-Speed Characteristics.

FiberMall's QSFPDD-400G-PC

FiberMall’s QSFPDD-400G-PC

Features  and Benefits

  • Compatible with IEEE 802.3bj and IEEE 802.3cd
  • Supports aggregate data rates of 400Gbps(PAM4)
  • Optimized construction to minimize insertion loss and cross talk
  • Pull-to-release slide latch design
  • 28AWG through 30AWG cable
  • Straight and break out assembly configurations available
  • Customized cable braid termination limits EMI radiation   
  • Customizable EEPROM mapping for cable signature
  • RoHS compliant

Product   Applications

  • Switches, servers, and routers
  • Data Center networks
  • Storage area networks
  • High-performance computing
  • Telecommunication and wireless infrastructure
  • Medical diagnostics and networking
  • Test and measurement equipment

Industry  Standards

  • 400G Ethernet(IEEE 802.3cd)
  • InfiniBand EDR

(11) 400G QSFP-DD to 2X200G QSFP56 Breakout Direct Attach Cable– PAM4

General  Description

  • QSFP-DD_2XQSFP56 passive copper cable assembly feature eight differential copper pairs, providing four data transmission channels at speeds up to 56Gbps(PAM4) per channel, and meets 400G Ethernet and InfiniBand Enhanced Data Rate(EDR) requirements. Available in a broad range of wire gages-from 28AWG through 30AWG-this 400G copper cable assembly features low insertion loss and low cross talk.
  • QSFP-DD_2XQSFP56 uses PAM4 signals for transmission, which doubles the rate. However, there are more stringent requirements for cable insertion loss. For detailed requirements, please see High-Speed Characteristics.

FiberMall's 400G QSFP-DD to 2X200G QSFP56 Breakout Direct Attach Cable

FiberMall’s 400G QSFP-DD to 2X200G QSFP56 Breakout Direct Attach Cable

Features  and Benefits

  • Compatible with IEEE 802.3bj and IEEE 802.3cd
  • Supports aggregate data rates of 400Gbps(PAM4)
  • Optimized construction to minimize insertion loss and cross talk
  • Pull-to-release slide latch design
  • 28AWG through 30AWG cable
  • Straight and break out assembly configurations available
  • Customized cable braid termination limits EMI radiation   
  • Customizable EEPROM mapping for cable signature
  • RoHS compliant

Product   Applications

  • Switches, servers, and routers
  • Data Center networks
  • Storage area networks
  • High-performance computing
  • Telecommunication and wireless infrastructure
  • Medical diagnostics and networking
  • Test and measurement equipment

Industry  Standards

  • 400G Ethernet(IEEE 802.3cd)
  • InfiniBand EDR

(12) 400G QSFP-DD to 8X50G SFP56 Breakout Direct Attach Cable – PAM4

General  Description

  • QSFP-DD_8XSFP56 passive copper cable assembly feature eight differential copper pairs, providing four data transmission channels at speeds up to 56Gbps(PAM4) per channel and meets 400G Ethernet and InfiniBand Enhanced Data Rate(EDR) requirements. Available in a broad range of wire gages-from 28AWG through 30AWG-this 400G copper cable assembly features low insertion loss and low cross talk.
  • QSFP-DD_8XSFP56 uses PAM4 signals for transmission, which doubles the rate. However, there are more stringent requirements for cable insertion loss. For detailed requirements, please see High-Speed Characteristics.

FiberMall's QSFPDD-8SFP56-PC

FiberMall’s QSFPDD-8SFP56-PC

Features  and Benefits

  • Compatible with IEEE 802.3bj and IEEE 802.3cd
  • Supports aggregate data rates of 400Gbps(PAM4)
  • Optimized construction to minimize insertion loss and cross talk
  • Pull-to-release slide latch design
  • 28AWG through 30AWG cable
  • Straight and break out assembly configurations available
  • Customized cable braid termination limits EMI radiation   
  • Customizable EEPROM mapping for cable signature
  • RoHS compliant

Product   Applications

  • Switches, servers, and routers
  • Data Center networks
  • Storage area networks
  • High-performance computing
  • Telecommunication and wireless infrastructure
  • Medical diagnostics and networking
  • Test and measurement equipment

Industry  Standards

  • 400G Ethernet(IEEE 802.3cd)
  • InfiniBand EDR

7. Application of 200G QSFP DD AOC in InfiniBand Network

With the continuous development and high demand of data centers, people are constantly updating the latest technologies and developing optimal-performance products and solutions. Some time ago, FiberMall released the 200G QSFP DD PSM8 optical module, marking the basic completion of the 200G low-cost data center internal parallel optical interconnection solution based on NRZ modulation, and also symbolizing the company’s leading position in 200G solutions. Different from the 400G solution advocated by the industry, FiberMall insists on the 200G data center solution and can provide customers with one-stop services and answers.

The following mainly analyzes the characteristics and application fields of InfiniBand technology among current switches based on the development process of the supercomputing center at this stage. Taking 200G QSFP-DD AOC as an example, it illustrates that the port packaging form of the interconnection technology of the supercomputing center is moving towards a state of higher operating bandwidths.

InfiniBand Technology in Supercomputing Systems

At present, there are InfiniBand, high-performance Ethernet, IBM’s BlueGene, Cray, and rising star Intel’s OmniPath in the supercomputing center interconnection technology camp. These five technologies occupy an important market share, among which InfiniBand and high-performance Ethernet occupy an absolute leading position.

top 500 interconnect trend

The interconnection technology of supercomputing centers is developing towards higher bandwidth, lower latency, lower power consumption, and denser interconnection ports. InfiniBand interconnection technology is currently the first choice for high-performance storage interconnection solutions, precisely because it meets the needs of large bandwidth and low latency.

InfiniBand is a unified interconnect fabric that handles storage I/O, network I/O, and inter-process communication. It can interconnect disk arrays, SANs, LANs, servers, and clustered servers, provide high-bandwidth, low-latency transmission over relatively short distances, support redundant I/O channels in single or multiple interconnected networks, and keep your data center running in the event of a partial failure. Especially in the future when the traffic inside the HPC data center will increase significantly, as a network connection technology is applied between servers, InfiniBand will have a broader space for development.

The following figure shows the product roadmap of InfiniBand.

the product roadmap of InfiniBand

InfiniBand Network Technology Trends

The interconnection interface of InfiniBand has gradually transitioned from the copper interconnection to the parallel optical interconnection technology dominated by VCSEL lasers. In contrast, the optical interconnection technology has more advantages:

1. Compared with copper cables, optical fiber has low attenuation and a longer transmission distance of up to 100 meters.

2. Strong anti-interference, zero packet loss rate, no matter how complicated the strong electricity coiled around the fiber is, the transmission speed is always consistent.

3. The service life is very long and the compatibility is high. Most of the optical fibers on the market can be used for 10 years or even longer, which the copper cable network cable can not compare.

The port form factor of the interconnect technology of the supercomputing center is developing towards a higher working bandwidth. The following table shows different InfiniBand’s interconnect port form factors and working rates.

NameAbbreviationRaw signaling rateApplied encodingEffective data rateAggregated
(4x)
Throughput
Interconnect port form
Single data rateSDR2.5Gb/s8b/10b2Gb/s8Gb/sCX4/SFF-8470
Double data rateDDR5Gb/s8b/10b4Gb/s16Gb/sCX4/SFF-8470
Quad data rateQDR10Gb/s8b/10b8Gb/s32Gb/sQSFP+
Fourteen data rateFDR14.1Gb/s64b/66b13.64Gb/s54.5Gb/sQSFP+
Enhanced data rateEDR25.8Gb/s64b/66b25Gb/s100Gb/sQSFP28
High data rateHDR51.6Gb/s64b/66b50Gb/s200Gb/sQSFP DD
Next data rateNDRTBDTBDTBDTBDTBD

Optical Module Packaging Evolution in the InfiniBand System

1.QSFP+

The QSFP+ package solution is designed for high-density interconnect ports, and its system components include electromagnetic interference (EMI) shields, fiber optic cables, optical engines, connectors, and stacking cages. The QSFP+ package meets the requirements for a high-density port, and it integrates 4-way transmitting and 4-way receiving channels. QSFP+ transceivers can replace 4 standard SFP+ transceivers, for it has greater port density and saves more overall-system cost savings than traditional SFP+ products do.

2.QSFP28

QSFP28 (25G quad small form-factor pluggable) package with a higher rate maintains the same size as the mechanical structure of the QSFP+ package. QSFP28 is a high-density, high-speed product solution designed for next-generation optical communication, data center, and supercomputing network market applications. The package provides 4-way high-speed signaling channels. Each channel has a transfer rate from 14Gbps to 25 (28)Gbps and will meet the needs of 100Gbps Ethernet (4x25Gbps) and 100Gbps 4X InfiniBand Enhanced Data Rate (EDR).

3. QSFP DD

Following the large-scale deployment and application of 40G QSFP+ and 100G QSFP28 packages, QSFP DD is considered to be the most advantageous form factor in the next-generation 200G/400G network deployment. The size of the QSFP DD package is basically the same as that of the QSFP28 package, but its length is slightly longer (with a dual-row gold finger connector), and its electrical interface supports 8x25Gbps NRZ (200G) and 8x28GBd PAM4 (400G). Therefore, on the space interface of the same density, its bandwidth is 2 to 4 times the working bandwidth of the 100G QSFP28 optical module. At the same time, the QSFP DD also has equipment that is backward compatible with the QSFP28 interface, which plays a role in protecting investment.

qsfp-dd optical transceiver

Application of 200G QSFP DD AOC in InfiniBand

Unlike Ethernet, which is used for high-level network communication, InfiniBand is mainly used for low-level server-side input/output performance tasks, and AOC is generally used for connection between devices. In addition, considering the problem that signals are easily distorted in ultra-high-speed optical fiber transmission, InfiniBand transmits data signals in a differential manner in optical fibers and adds filters at the signal receiving end to filter out signal noise, fully ensuring the signal integrity of the connected network.

FiberMall 200G QSFP DD multimode optical modules and 200G QSFP-DD 1- 100m AOC products use self-developed and packaged COB (Chip on Board) technology. The products can provide a new generation of optical interconnect solutions with low cost, low power consumption, high density, and high speed. The product integrates two optical engines in a limited and compact space, providing 8-way 25G high-speed data channels. Its excellent heat dissipation design solves the problem of temperature accumulation. The total power consumption is less than 3.5W at 0~70 degrees celsius at full temperature. The optical interface adopts MPO24 Interface (16 fibers), and the multi-mode OM4 fiber can guarantee a working distance of 1-100 meters.

FiberMall's 200G QSFP DD AOC

FiberMall’s 200G QSFP DD AOC

Mr. Gilad Shainer, vice president of marketing at Mellanox, a well-known InfiniBand network solutions company, said: “With the increasing development of machine learning and HPC cloud, customers’ requirements for network performance are demanding. The high performance of the InfiniBand HDR 200Gb/s interconnect solution, network computing, and network self-healing capabilities are the key technologies for future intelligent cloud computing centers.” FiberMall’s 200G QSFP DD AOC is an interconnection solution tailored for future cloud networks and high-performance computing data centers.

Conclusion

It can be concluded that either active optical cables(AOC) or direct attach copper cables(DAC) are the better cabling solution for IDC networking according to different application demands. When there are few transmission requirements for the data center, the DAC cable solution is suggested as a better internet cable solution for the interconnection between the server and the switch within 5m/10m, while the AOC fiber solution is perfect for the interconnection between switches and the switches. By all means, it is unnecessary to analyze which is the better solution, that is AOC cable is always your first for performance is way much more important than cost if budget is never your concern.

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