How Much Do You Know About 40G QSFP+ AOC

40 Gigabit Ethernet era is already upon us and makes a contribution to satisfying the increasing demands of higher throughputs and bandwidth. Existing and emerging network technologies are driving the need for high-density optical connectivity solutions to address the trends to optimized cable management and data center real estate usage. The 40G QSFP+ AOC (active optical cable) has been widely used in data center to achieve 40G interconnection. This article will introduce the 40G QSFP+ AOC in data center applications.

Development of AOC

Primarily, active optical cable (AOC) assemblies were invented to replace copper technology in data centers and high performance computing (HPC) applications. As we know, copper cable is heavy and bulky, making it difficult to physically manage the datacenter. And due to the nature of electrical signals, electromagnetic interference (EMI) limits copper’s performance and reliability. Though there are so many disadvantages of copper cable, at that time, it is the main stream while the idea of AOCs almost seems too good to be true. However, the advantages of AOC make the predecessors look obsolete and unsophisticated, and changes the limitation of copper cable as well as playing an important role in high speed data transmission. Nowadays, a variety of AOCs have been launched in the market, such as 10GbE SFP+ AOCs, 40Gbps QSFP+ AOCs and 120G CXP AOCs, for 10G, 40G and 100G applications.

What Is 40G QSFP+ AOC

40G AOC, is a type of active optical cable for 40GbE applications that is terminated with 40GBASE-QSFP+ on one end, while on the other end, in addition to QSFP+ connector, it can be terminated with SFP+ connector, LC, SC, FC, and ST connector etc. The 40G QSFP+ AOC is a parallel 40Gbps quad small form factor pluggable (QSFP+) active optical cable, which supplies higher port density and total system cost. The QSFP+ optical modules provide four full-duplex independent transmit and receive channels, each are able of 10Gbps operation 40Gbps aggregate bandwidth of at least 100m multimode fiber. Most DAC assemblies have one module on each end of the cable. But there is a special kind of DAC assembly which may have 3 or 4 modules on one end of the cable. For instance, Cisco QSFP-4X10G-AOC5M compatible QSFP+ to 4SFP+ breakout AOC from Fiberstore has a single QSFP+ module rated for 40-Gbps on one end and four SFP+ modules, each rated for 10-Gbps, on the other end.

40G QSFP+ AOC vs QSFP+ Optics

• Cost: 40G AOCs cost lower than SR4 modules and do not need to use together with extra fiber patch cables. For instance, Arista AOC-Q-Q-40G-10M compatible QSFP+ to QSFP+ active optical cables are suitable for very short distances and offer a very cost-effective way to establish a 40-gigabit link between QSFP ports of Arista switches within racks and across adjacent racks. Besides, when using 40G AOC, there are no cleanliness issues in optical connector and there is no need to do termination plug and test when troubleshooting, which can help user save more time and money.
• Insertion Loss & Return Loss: Under the same case of transmission distance, the repeatability and interchangeability performances of SR4 module interface are not good as 40G AOC. What’s more, when different fiber optic patch cables plug into the module, it will have the different insertion loss and return loss. Even for the same module, this issue is existed. Of course, the related metrics such as the testing eye pattern will have no significant changes so long as the variation in and conformed to the scope. In contrast, an AOC with good performance is more stable and has better swing performance than SR4 modules in this situation.

All in all, 40G QSFP+ AOC is highly recommended to use in data center interconnection. Apart from the 40G QSFP+ AOC, Fiberstore also supplies 10G SFP+ AOC, QSFP + AOC to 8 x LC and 120G CXP AOC, etc. All of them can meet the ever increasing need to cost-effectively deliver more bandwidth, and can be customized to meet different requirements.

Optical Fiber Loss Testing

Optical loss testing of multimode fiber can be affected by many variables, including fiber mismatch, the type and quality of the test reference cords and the launch conditions for launching light into the fiber under test. This article will look at how these different variables can affect the optical loss performance of a link under test.

Optical Loss Testing - Why It Is Important

Providing an accurate method for optical loss testing of multimode fiber is becoming a lot more important for higher data rate applications that place more stringent requirements on the maximum allowable loss for a channel between an optical transmitter and an optical receiver. The higher the data rate, the tighter the loss budget for a channel. The maximum allowable loss for a 10Gb/s Ethernet channel over OM3 multimode fiber is 2.6 dB. The maximum allowable loss for a 40 Gb/s and a 100 Gb/s Ethernet channel is 1.9 dB over OM3 fiber and 1.5 dB over OM4 fiber.

Factors That Affect The Accuracy of Optical Loss Testing

There are several major factors that can affect the testing accuracy for optical loss measurements. These include: 1.The type and quality of the “test reference cords”

The type and quality of the “test reference cord” is critical for accurate optical loss measurements in the field. The end-face geometry of the polished ferrule on the cord connector can have a significant effect on the test results and must meet precise parameters such as radius of curvature, apex and fiber protrusion.

2.Fiber mismatch between the test reference cords and the link under test

Fiber mismatches are the result of inherent fiber characteristics and are independent of the techniques used to join the two optical fibers. The intrinsic coupling loss due to fiber mismatch include core diameter differences, core/cladding concentricity error, numerical aperture differences.

3.The characteristics of light source and how light is coupled into the fiber

The launch conditions and how light is coupled into the fiber can have the greatest effect on optical loss measurements. For multimode fiber, different distributions of launch power (launch conditions) can result in different attenuation measurements.

Testing Tools

Fiber optic cable testing needs special tools and instruments. And they must be appropriate for the components or cable plants being tested. The following five kinds of fiber testing tools are needed for the testing work.

• OLTS—Optical loss test set (OLTS) with optical ratings matching the specifications of the installed system (fiber type and transmitter wavelength and type) and proper connector adapters. Power meter and source are also needed for testing transmitter and receiver power for the system testing.
• Reference test cable—This cable should be with proper sized fiber and connectors and compatible mating adapters of known good quality. And the connector loss is less than 0.5 dB.
• VFL—Visual fiber tracer or visual fault locator (VFL)
• Microscope—Connector inspection microscope with magnification of 100-200X, video microscopes recommended.
• Cleaning Materials—Cleaning materials intended specifically for the cleaning of fiber optic connectors, such as dry cleaning kits or lint free cleaning wipes and pure alcohol.

FiberStore offers a wide selection of fiber testers & tools to fit any fiber optic cable lineman or powerline worker jobs. We stock top high quality test equipment for the communications applications. In the fiber optic installation and maintenance works, Optical Power Meters, Fiber Light Sources, Fiber Scopes and OTDR are commonly used for fiber optic testing. And Splicing fiber tools, termination tool kits and cleaning tools, like strippers, cable cutters, splice protective sleeves help work easier. Besides, high quality fiber cables, such as Push-Pull MPO patch cable, push and pull cable, Push-Pull LC cable are also available for your choice. If you need any service, please contact us via sales@fs.com.

Guide to 40GBASE-SR4 QSFP+ Transceivers

Today’s enterprise data centers and networking environments are undergoing an infrastructure transformation, requiring higher speeds, greater scalability, and higher levels of performance and reliability to better meet the demands of business. As speed and performance needs increase, the 40GBASE-SR4 QSFP+ optical transceivers have become an integral part of overall system design. This article will give you a comprehensive introduction to 40GBASE-SR4 QSFP+ optical transceivers.

What Is 40GBASE-SR4 QSFP + Transceiver

40GBASE-SR4 is a fiber optic interface for multimode fiber of OM classes 3 and 4 with four parallel OM3 or OM4 fibers in both directions. “S” means short, indicating that it is an interface for short distances. The “R” denotes the type of interface with 64B/66B encoding and the numeral 4 indicates that the transmission is carried out over a ribbon fiber with four multimode fibers in every direction. Each lane has a 10 Gbit/s data rate. The 40GBASE-SR4 QSFP+ transceivers are hot-swappable, low-voltage digital diagnostic Ethernet optical transceivers that support high-speed serial links over multi-mode optical fiber at a signaling rate of 4×10 Gbps. They comply with QSFP+ mechanical, optical, and electrical specifications (SFF-8436). 40GBASE-SR4 QSFP+ modules usually use a parallel multimode fiber (MMF) link to achieve 40G. It offers 4 independent transmit and receive channels, each capable of 10G operation for an aggregate data rate of 40G over 100 meters of OM3 MMF or 150 meters of OM4 MMF. It primarily enables high-bandwidth 40G optical links over 12-fiber parallel fiber terminated with MPO/MTP multifiber female connectors.

Applications of 40GBASE-SR4 QSFP + Transceiver

40GBASE-SR transceivers are used in data centers to interconnect two Ethernet switches with 8 fiber parallel multimode fiber OM3/OM4 cables. The QSFP+ transceiver modules can be connected to both copper and optical cables. In the process of transmitting data, the 40GBASE-SR4 QSFP+ transceiver converts parallel electrical input signals into parallel optical signals by a 850nm vertical cavity surface emitting laser (VCSEL) array. All data signals are differential and the data rate can be up to 10 Gbps per channel. For example, Extreme 10319 compatible 40GBASE-SR4 QSFP+ transceiver from Fiberstore operates in 4-lanes at a wavelength of 850nm.

QSFP-40G-SR4 vs. QSFP-40G-CSR4

40GBASE-CSR4 QSFP modules extend the reach of the IEEE 40GBASE-SR4 interface to 300 and 400 meters on laser-optimized OM3 and OM4 multimode parallel fiber, respectively. Each 10-gigabit lane of this module is compliant to IEEE 10GBASE-SR specifications. This module can be used for native 40G optical links over 12-fiber parallel cables with MPO/MTP female connectors or in a 4x10G mode with parallel to duplex fiber breakout cables for connectivity to four 10GBASE-SR interfaces. Cisco compatible QSFP-40G-CSR4 transceiver from Fiberstore is optimized to guarantee interoperability over the complete specification range of 10GBASE-SR.

Fiberstore offers a wide range options of brand-compatible 40GBASE-SR4 QSFP+ transceivers. In order to ensure each transceiver with high-compatibility, we have a comprehensive and reliable test assured program for each optics. All these 40GBASE-SR4 QSFP+ transceivers will be tested in the original-brand switches to guarantees the high compatibility.

40G QSFP+ Direct Attach Copper Cables

With the wide deployment of 40 Gigabit Ethernet, the 40G QSFP+ direct attach copper cables are becoming more and more popular due to the compact size, low power and cost-effectiveness. 40G QSFP+ to QSFP+ direct attach copper cables and 40G QSFP+ to 4 x 10G SFP+ direct attach copper cables are hot pluggable and parallel passive / active copper cables for storage, data, and high-performance computing connectivity.

QSFP+ to QSFP+ Direct Attach Copper Cables

QSFP+ to QSFP+ direct attach copper cables are hot-removable and hot-insertable. A cable consists of a cable assembly that connects directly into two QSFP+ modules, one at each end of the cable. The cables use integrated duplex serial data links for bidirectional communication and are designed for data rates up to 40 Gbps. QSFP+ to QSFP+ direct attach copper cables are suitable for very short distances and offer a highly cost-effective way to establish a 40G link between QSFP+ ports of QSFP+ switches within racks and across adjacent racks. These cables connect to a 40G QSFP port of a switch on one end and to another 40G QSFP port of a switch on the other end.

QSFP+ to 4 SFP+ Direct Attach Copper Cables

The move from 10G to 40G Ethernet will be a gradual one. It is very likely that one may deploy switches that have 40G Ethernet ports while the servers still have 10G Ethernet ports. For that situation, we should use a QSFP+ to 4 SFP+ direct attach breakout copper cable. These cables connect to a 40G QSFP port of a switch on one end and to four 10G SFP+ ports of a switch on the other end, which allows a 40G Ethernet port to be used as four independent 10G ports thus providing increased density while permitting backward compatibility and a phased upgrade of equipment.

Directions for Use

The 40G QSFP+ direct attach copper cables are used to connect switch to switch or switch to server. When we use a fiber optic transceiver and patch cable to establish a fiber link, we should firstly plug the transceiver to the switch and then plug the patch cable to the transceiver. But for a QSFP+ direct attach copper cable, both SFP+ connector and QSFP+ connector can be directly inserted into the switch and don’t need a transceiver at all, which provides a really cost-effective solution for interconnecting high speed 40G switches to existing 10G equipment or 40G switches to 40G switches.

40G QSFP+ direct attach copper cables can provide inexpensive and reliable 40G speed connections using copper cables with distances reaching up to 30ft (~10 meters length). Cost of short reach connectivity is significantly reduced by avoiding the more costly fiber transceivers and optical cables. As the main fiber optical manufacturer in China, Fiberstore provides a good selection of 40G QSFP+ copper cables, both passive and active copper cables are available. For longer distances, active copper or optical cables are required. For more information or quotation, please contact us via sales@fs.com.

FAQ on Fiberstore 40G Cabling and Transceivers

With an increasing demand for more bandwidths, faster data rates and higher performance in telecommunication networks, the business case for 40 Gigabit Ethernet is becoming inescapably compelling. However, many users may feel confused when using 40G cables and optical transceivers. This article will solve the most frequently asked questions on Fiberstore’s 40G cabling and transceivers.

Q1: What 40G cables and transceivers are available from Fiberstore?

Fiberstore supplies a full range of both copper cables and optical transceivers for 40GbE, compliant to the IEEE standards. For copper both QSFP+ to QSFP+ (40G to 40G) and QSFP+ to SFP+ (40G to 4x10G) cables enable short reach options. For longer distances, Fiberstore offers a wide range of optical transceivers for various fiber types and reach requirements.

Q2: What does the IEEE 40GBASE-X standard describe?

The IEEE 40GBASE-X standard describes the following:

• 40GBASE-SR4 It reaches 40-Gbps Ethernet over four short-range multimode fiber optic cables and supports link lengths of 100m and 150m respectively on laser-optimized OM3 and OM4 multimode fiber cables. In this process, the multimode fiber uses parallel-optics transmission instead of serial transmission due to the 850nm vertical-cavity surface-emitting laser (VCSEL) modulation limits. For example, Mellanox MC2210411-SR4 compatible 40GBASE-SR4 QSFP+ transceiver from Fiberstore supports link length of 100m over multimode fiber cable.
• 40GBASE-LR4 It reaches 40-Gbps Ethernet over four wavelengths carried by a single long-distance singlemode fiber optic cable and supports link lengths of up to 10 km over single-mode fiber with duplex LC connectors. It operates at a wavelength of 1310 nm. The 40 Gigabit Ethernet signal is carried over four wavelengths with 10G on each wave.
• 40GBASE-CR4 It is a direct attach cable segment with the QSFP+ modules attached to each end of the cable. It reaches 40-Gbps Ethernet over four short-range twinaxial copper cables bundled as a single cable and supports link lengths of up to 10 km over a standard pair of G.652 single-mode fiber with duplex LC connectors.

Q3: Can the 40G-LR4 transceiver be split into 4x10G connections?

No, 40G-LR4 cannot be split into 4x10G. The 40GBASE-LR4 uses 4 lambdas (or wavelengths) on a pair of single mode fibers, and does not lend itself to “splitting” into 4 pairs without substantial complexity to split out the wavelengths. The unique characteristic of 40GBASE-SR4 is that it uses parallel (ribbon) fiber, which allows the creation of 4 fiber pairs. As an alternative single mode parallel 40G optics are available (40G-PLRL4 and 40G-PLR4) that do allow for splitting into 4x10G (single mode).

Q4: How does the QSFP+ to SFP+ fiber convertor allow 4x 10G?

The IEEE 40G-SR4 standard specified a parallel technology, with 4 lanes in each direction. The purpose of this was to allow for easier development of 40G, re-using 10G components. As a side result the 40G multi-mode transceivers can also support 4x10G modes. A fiber that connects from one 40G port to four 10G ports provides a physical path to allow the source “40G” port running in 4x10G mode to be connected to 4 unique 10G destinations. As the fiber is a passive medium it has no concept of the 40G or 10G signals.

Fiberstore provides various types of 40G cables and transceivers including single-mode and multi-mode with different channels and wavelengths. All these transceivers are compatible with famous brands, like Brocade QSFP+, HP QSFP+, Juniper QSFP+, etc. They can also be customized to meet your special requirements.