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100G CFP and QSFP28 Modules’ Functional Mode Comparison

100G CFP and QSFP28 Modules’ Functional Mode Comparison

To meet the growing data rates of optical interconnects, 100G optical modules are booming in 2017. And there are many types of 100G optical transceivers in the market such as CFP modules and QSFP28. Those who have experienced in using optical transceivers may know each kind of transceiver has their own functional mode. And knowing this functional mode helps you to choose the suitable 100G optics for your networks.

CFP SR10

CFP SR10 is a 100Gbps parallel transceiver for optical communication applications. It supports link lengths of 100 m and 150 m on laser-optimized OM3 and OM4 cable. This transceiver converts the 10-channel 10Gbps electrical input data into 10-channel 850nm optical signals and then coupling them into ribbon fiber array (MPO connector) for 100Gbps optical signal transmission. On the receiver side, the optical signals are converted into electrical data for 10 output channels. Following is the functional diagram.

cfp sr10

CFP LR4

CFP LR4 is another member of 100G CFP modules. But its working process is a little different from CFP SR10 module. CFP LR4 uses four channels for transmitting and four channels for receiving. It uses four WDM optical signals and multiplexes them into a single channel for 100G transmission. On the receiver side, it demultiplexes the 100Gbps signals into four WDM optical signals and then converts them into four output channels. Its functional diagram is below.

cfp lr4

QSFP28 SR4

QSFP28 SR4 is also a parallel optical transceiver. It offers four channels for transmitting and four channels for receiving, each capable of 25Gb/s operation for an aggregate data rate of 100Gbps on 100 meters of multimode fiber, which is similar to the CFP LR4. However, the QSFP28 SR4 doesn’t multiplex the optical signals into WDM for transmitting. Its functional diagram is shown below.

QSFP28 SR4

QSFP28 PSM4

The functional mode of QSFP28 PSM4 is much similar to that of QSFP28 SR4. It uses four independent transmit and receive channels. Each channel operates at 25Gbps. The difference mainly lies in the fiber they use. QSFP28 PSM4 works on single mode ribbon fiber cable, while QSFP28 SR4 works on multimode ribbon fiber cables.

qsfp8 PSM4

QSFP28 CWDM4

Similar to PSM4, the QSFP28 CWDM4 also uses 4x25Gbps to achieve 100Gbps. But the difference is that the CWDM4 utilizes an optical MUX and DEMUX to reduce the fiber it needs, which is like the CFP LR4. It only needs a duplex single mode fiber cable to connect two 100G CWDM4 optical modules. At present, CWDM4 links are used in both 100G CFP4 or the QSFP28 optical transceivers.

QSFP28 CWDM4

Conclusion

From the comparison above, we can find that there are mainly two differences between of the functional mode of these 100G optical transceivers. One is the transmission channel and another is the cable type. Except for that, wavelengths, connectors, and other factors also can affect the working performance of optical transceiver in optical connections.

Nowadays, as the competition is getting severe, some vendors have cut the price of 100G modules price. FS.COM is a professional optical products supplier. It offers various compatible optical transceiver for different applications at a lower price. For instance, the 100G QSFP28 SR4 price in FS.COM is only $269. Here is part of the price of 100G optical modules. If you have any need, please welcome to visit our website www.fs.com for more information.

Mode Description Price
CFP-100G-SR10 CFP Cisco Compatible 100GBASE-SR10 850nm 150m Transceiver $1500
CFP-100G-LR4 CFP Cisco Compatible 100GBASE-LR4 1310nm 10km Transceiver $1500
QSFP-100G-SR4-S QSFP28 Cisco Compatible 100GBASE-SR4 850nm 100m Transceiver $269
QSFP-100G-PSM4-S QSFP28 Cisco Compatible 100GBASE-PSM4 1310nm 500m Transceiver $750
QSFP-100G-CWDM4-S QSFP28 Cisco Compatible 100GBASE-CWDM4 1310nm 2km Transceiver $1400
Introduction to 10GbE/25GbE/40GbE/100GbE Fiber Optic Cabling

Introduction to 10GbE/25GbE/40GbE/100GbE Fiber Optic Cabling

Technology is changing rapidly. Just when you got used to Gigabit Ethernet speeds being a fast & reliable system, someone unveiled 10GbE, 25GbE, 40GbE or even 100GbE systems a few years later. The newer and higher performing iterations are indeed the great breakthrough for telecommunication industry, but also pose difficulty in choosing network migration path—10G to 40G to 100G, or to 25G to 50G to 100G. We have described 10G, 25G, 40G and 100G Ethernet technology before, now in this blog, we’d like to introduce the four fiber optic cabling, and compare two 100G migration paths.

Cost-effective 10GbE Fiber Optic Cabling

10 Gigabit Ethernet technology defined by IEEE 802.3ae-2002 standard, is matured nowadays. Just like the “old” Gigabit Ethernet, 10Gb network can be terminated with either copper or fiber cabling. 1000BASE-T standard usually uses the Cat5e cables as the transmission media, while 10GbE bandwidth requires high grade copper cables like Cat6/Cat6a/Cat7 cables to support 10Gbps data rate. For instance, 10G SFP+ 10GBASE-T transceiver modules utilize Ethernet copper cables (Cat6a/Cat7) for a link length of 30m. SFP+ direct attach cables (DAC) and active optical cables (AOC) are also regarded as the cost-effective solutions for 10G short-reach applications. Besides 10G copper cables, there are single-mode (OS2) and multimode fiber patch cables (OM3/OM4) applied to different 10GbE IEEE standards. For the detailed information about the 10G cabling options, please see the following table.

10G fiber optic cable

As to the 10G fiber optic transceivers, there are a series of optical form factors including the XENPAK, X2, XFP, SFP+. The former three 10GbE optical transceivers were released earlier than smaller 10G form factor—SFP+ module. However, owing to their larger footprint, they are not successful on the 10G hardware market. Furthermore, SFP+ optics, compliant with several IEEE standards (SR, LR, LRM, ER, ZR and 10GBASE-T…) wins the heart of 10G end-users.

Singe-lane Design Makes 25GbE Shine

When 25G Ethernet was developed to support a single-lane 25Gbps standard in 2014, it was treated as the “new” 10GbE technology but delivers 2.5 times more data. Compared to 40GbE that was based on 10GbE, 25GbE with one lane obviously improves the port density and cost requirement. 25GbE network can support both copper and fiber optic cables, seen in the below table.Similar to 10GbE networks, 25G Ethernet physical interface specification supports several 25Gbps capable form factors, including CFP/CFP2/CFP4, SFP28 (1×25 Gbps) and QSFP28 (4×25 Gbps), which is also used for 100GbE. SFP28 25GBASE-SR and 25GBASE-LR SFP28 are two popular 25GbE optical transceiver modules available on the market, the former supports up to 100m link length while the latter allows a maximum transmission distance of 10 km.

25G optical modules

The available optical switches of the market do not support direct 25GbE connections using an SFP28 direct attach copper (DAC) cable. It is recommended to use a breakout cable that allows four 25GbE ports to connect to a 100GbE QFSFP28 switch port. FS.COM SFP28 DAC cable lengths are limited to four meters (1m, 2m, 3m, 5m) for 25GbE. And if you prefer a longer length, the 25GbE active optic cable (AOC) solutions are good recommendations.

25G Optics SFP28 Type
Media/Reach
All 25G SFP28 Ports 25GBASE-SR 50µm MMF / 70m
25GBASE-LR 9µm SMF / 10km
25GBASE-AOC Pre-terminated in 3, 5, 7, 10, 15, 20, 25, 30m lengths
OM4 MMF MTP/MPO 150m
25G Copper SFP28 Type Media/Reach
All 25G SFP28 Ports 25GBASE-CR Twinax / ‘Direct Attach’ Pre-terminated in 1m, 2m, 3m, 5m lengths

 

Fast & Reliable 40GbE Fiber Optic Cabling

Like the 10GbE fiber optic cabling, there are several IEEE standards of 40GbE transceiver in the whole evolution. 40G QSFP+ optical transceivers are the most commonly used optics for 40G network. So how to choose fiber optic cables for 40G optical transceivers? The following table will help you out.

40G modules

Besides the QSFP+ fiber transceivers and fiber optic cables, 40G DAC cables available in QSFP+ DAC cables and AOC cables enable short-reach options. For 40G cabling, QSFP+ to QSFP+ (40G to 40G) and QSFP+ to 4SFP+ (40G to 10G) breakout cables satisfy customers for various fiber types and reach requirements.

100GbE Fiber Optic Cabling For Future Proofing

With the price of 100G optics cutting down in 2017, 100GbE network is no longer out of customers’ reach. Telecom giants like Cisco, Arista, HPE launches series of 100G optical switches to meet the market demand. And for other 100G components like 100G optical transceivers, fiber patch cables, racks & enclosures, etc, those are ubiquitous on the market.

100G optical transceivers including the CFP, CFP2, CFP4, CXP and the most popular 100G QSFP28 optics in IEEE standards provide a great selection to the overall users.For 100G inter-rack connections, QSFP28 to QSF28 Direct Attach Copper (DAC) Cables and Active Optical Cables (AOC) as well as the QSFP28 to SFP28 breakout cables are the cost-effective solutions.

Path 1: 10G to 40G to 100G

Many of the largest data centers has already moved to 40GbE, which are constructed out of 4 parallel SerDes 10Gb/s links between the Ethernet chip and the QSFP pluggable. The short-reach QSFP interfaces (QSFP+ SR4 modules) use 4 pair of fiber between them, and the copper Direct Attach Cable (DAC) equivalent carry the same on several copper cables inside the big cable. Longer-reach QSFP interfaces (QSFP+ LR4 optics) put the 4 10Gb/t streams onto separate Wave Division Multiplexing (WDM) waves which can be carried over a single pair of fiber. This is part of the reason why QSFP optics are fairly expensive still, especially for longer distances.10GbE to 40GbE to 100GbESimilarly for the 100GbE interfaces that are available today, these are really constructed out of 10 parallel paths of 10Gb/t streams. 100G SR10 modules is the optical transceiver modules that support 10×10Gb/s modes. But neither the CXP SR10 modules or CFP 100G SR10 optics are not popular on the 100G hardware market owing to their larger form factors. Eventually, they need to utilize the smaller footprint 100G modules—QSFP28 transceiver, which is mentioned above as the optical transceivers that can be used in 25GbE and 100GbE.

Result: Although the migration path from 10G to 40G to 100G requires more ports and increases cost per bit, 40GbE between switches is expected to be remain and will not be affected in the near future.

Path 2: 25G to 100G—The Move From 10 Lanes to 4

The old transition path of Ethernet has increased by 10X in speed like the 10G to 40G to 100G. However, 25 Gbps over a single lane for server makes 100G migration be 4×25Gb/s mode.100-gbe-block-diagramUsing four-lane variants like QSFP28 is more economical in several ways:

  • The single-lane design makes four 25 Gbps lanes transceivers less expensive than ten 10Gbps lanes because the transceiver is simpler and less costly to manufacture.
  • The power required to run SFP28 transceivers is much less than required for a typical 10-lane transceiver, it is the same case as the cooling costs.
  • For fiber connections, moving from 10GbE to 40GbE may require an upgrade to four times the number of fibers (MPO), but a 25GbE connection does not because it is the same as 10GbE (single TX and single RX, not four each for TX and RX).
  • Moving from 10GbE to 40GbE typically requires a forklift upgrade to thicker, more expensive cables, but a 25GbE direct attach copper connection does not.

Result: There are few switches and NIC cards that directly support 25GbE. But the curve for 25GbE won’t fade away, rapid development and pre-standard 25GbE products coming soon!

Conclusion

This article introduces 10G/40G/100G fiber optic cabling, and make a clear comparison between the two paths to 100GbE. Customers prefer 4×25Gbps for the reasons: Less parallel paths, less fibers, less optics, less everything. For those who want to upgrade from 40G to 100G, appreciate the reliable performance of 40G with the potential to run across 2 parallel 25Ghz rather than 4 required today.

Will CPAK 100G Transceiver Module Thrive in 2017?

Will CPAK 100G Transceiver Module Thrive in 2017?

Currently, prices on 100G optical transceivers have been dropping faster than those devices at 40G, which drives customers to migrate to 100G directly instead of turning to the intermediate 40G Ethernet. For example, QSFP-40G-SR-BD ($300) costs higher than QSFP-100G-SR4-S ($269) at FS.COM. It is the same case as other vendors. QSFP28 and CFP optical transceivers as the main transmission media of 100G network, dominate 100G hardware market.

100G transceiver modules

CPAK, released right after CFP2 100G modules, is the Cisco proprietary form factor, which greatly effect the popularity of this module type. However, in 2017, many third party optical solution vendors like FS.COM announce to help market to cut down this pricing and save budgets for services providers and operators. So will it thrive in 2017? Today’s article will describe CPAK 100G module in detail attached with the positive analytics of the future of this module type.

Unveiling CPAK Optical Transceiver Module

CPAK 100GBASE optical module, designed as a smaller, low-cost alternative to CFP transceiver, can be plugged into the CPAK ports of Cisco switches and routers. Besides, CPAK module is the first 100G optical transceivers that use CMOS Photonics technology. This type of 100GBASE modules can work in the following Cisco networking equipment—ASR 9000 Series Router; CRS-X Carrier Routing System; NCS 2000, 4000, and 6000 Series Routers; the Nexus 7000 and 7700 Series Switches, and the Cisco ONS Transport Platform.

CPAK optical transceiver incorporates IEEE standard interfaces available in several different types: 100GBASE-SR10, 100GBASE-ER4L, 100GBASE-LR4, 10x10G-ERL, 10x10GBASE-LR, etc. CPAK transceivers can support 10X10Gbps and 4X25Gbps mode for an aggregate of 100Gbps data rate. It can also operate high-density 10G breakout with MPO-24 cables. CPAK-100G-SR10 is backward compatible with 10GBASE-SR. While CPAK 10X10G-LR is compatible with 10GBASE-LR optics. CPAK LR4 module is compatible with other 100GBASE-LR4 compliant modules such as CFP to support high-bandwidth 100Gb optical links over standard single-mode fiber terminated with SC connectors.

CPAK Out-Competes CFP/CFP2 for Smaller Footprint & Energy Economy

Once the CPAK transceiver module had been released, it was marked as the smallest 100G footprint providing higher-port density and low power consumption for 100G networks. When comparing with CFP modules, CPAK transceivers are less than one third the size of CFP modules, and dissipate less than one third the power. In a comparison with CFP2 modules, CPAK optical transceivers are 20% smaller and consume 40% less power. In other word, if you use CPAK other than CFP2 modules in your data center switches, it can offer 20% greater port density and front-panel bandwidth.

100G-module-evolution

To sum up, CPAK optical module has smaller footprint than CXP, CFP and CFP2, but bigger than CFP4 and QSFP28 optics. Besides, CPAK 100GBASE-LR4 consumes less than 5.5W, which is less than CFP LR4 (24W), CFP2 LR4 (12W), CFP4 (9W) and CXP LR4 optics (6W) but a little higher than QSFP28 (3.5W). CPAK represents a significant advancement in optical networking, providing dramatic space and power efficiency.

CPAK Vs. QSFP28

QSFP28 optical transceiver is regarded as the most promising 100G optical module due to its smallest form factor and lowest power consumption. For example, Cisco CPAK 100GBASE-LR4 module supports link lengths of up to 10 km over standard single-mode fiber with SC connector with a nominal power consumption of less than 5.5W. QSFP28 100GBASE-LR4 supports up to 10km and consumes nearly 3.5W. CPAK optics obviously don’t have a shot when competing with QSFP28 optical transceivers.

What About the Future of CPAK Modules?

According to IHS Infonetics’s analytics, the prospect of the 100GbE transceivers market will be better in the coming years. At the same time, the development of 100GbE transceivers will be faster. In 2017, 100G technology and relevant optical transceivers gradually become mature. 100G optics like CXP, CFP/CFP2/CFP4, 100G QSFP28 in different standards offers a huge selection for customers. Of which QSFP28 100G modules, thanks to the smallest form factor and reliable performance, maintain large market share in 100G hardware market. In addition, some newly released 100G switches only have QSFP28 ports which in turn promotes the popularity of 100G QSFP28 transceivers.

100G-transceivers-evolution

In such a fierce market environment, it is hard to say whether CPAK will be a hot star in 100G hardware market or not. Anyhow—CPAK module is the first optical transceivers that use CMOS electronic technology. Furthermore, Cisco and several other vendors offer CFP2 to CPAK adapter to support the conversion between CPAK and CFP2 modules. Third party vendors like ourselves are also beginning to supply 100G CPAK modules in 2017. We will see if such industry development will take place!

Summary

CPAK module was launched just days after the certification of CFP2 optics. It is popular for the smaller footprint and energy economy. However, when competing with open source MSA compatible 100G products (CFP/CFP2/CFP4 and QSFP28), CPAK is not the ideal one for 100G high-density connectivity. The world undergoes a myriad changes in the twinkling of an eye. For the newly information about our new-coming CPAK modules, please visit fs.com or pay attention to the updated article in this blog.

Several 100G DWDM Solutions for Arista 7500E Series

Several 100G DWDM Solutions for Arista 7500E Series

To keep up with the global demand for higher bandwidth, Arista has designated 7500E series switch to address 100G long-hual dense wavelength division multiplexing (DWDM) connectivity. Arista 100G interconnect solution combines Layer 2/Layer 3 switching, wire-speed encryption and coherent DWDM into a high-density line card for the Arista 7500E data centers. Along with the introduction of Arista 7500E series switches, this article will illustrate several 100G DWDM solutions for distance up to 80 km, 150 km and 3000 km as well.

Arista 7500E Series Switch & Line Card

Arista 7500E series is the second generation of 7500 series switch that delivers scalable and deterministic network performance for mission critical data centers, enterprise and HPC environments. Available in a compact 7RU (4-slot) or 11RU (8-slot), Arista 7500E offers over 30Tbps of total capacity for 1,152 ports of 10GbE, 288 ports of 40GbE and support for 96-port 100GbE with a broad choice of interface types that support flexible combinations of 10G, 40G and 100G modes on a single port.

The 7504 and 7508 are the two types of Arista 7500E series switches. The 7508 systems support 8 linecards, dual supervisor modules and 6 fabric modules to provide a full 30Tbps of capacity. The smaller 7504 systems share a common architecture with the 7508 with the primary difference being support for 4 linecards and 15Tbps of forwarding capacity. The most unique feature of this switch is that it can connect with 10G SFP+, 40G QSFP+, 100G QSFP28 and CFP2 modules.

arista-7500E-switch

Arista 7500E series line card for addressing 1/10G, 40G and 100G with full support for industry standard connections and comprehensive layer 2 and 3 features for flexible deployment choice. The line card delivers error-free performance up to 3000 km of fiber and consumes less than 140W per 100Gbps. Similar to any other Arista platform, the DWDM line card utilizes the single binary image of Arista’s extensible operating system (EOS). Line cards with CFP2 and QSFP support standard 100G for both single and multimode fiber for distance up to 40 km.

Why Need 100G DWDM Solution?

100G optical transceivers provide the most straightforward method to connect 100G traffic over long-hual applications. 100G optics like CFP and QSFP28 offer cost-optimized solutions for connecting 100G switches together in a rack or data center. Nevertheless, the small and cost-effective QSFP28 100G optics now can only handle connections over distances of less than 10 km. For example, QSFP28 LR4 is compliant with 100GBASE-LR4 standard that operates over duplex LC cables for a link length of 10 km.

As to the CFP form factors, coherent CFP modules is designed to support metro and long-hual DWDM applications. CFP 100GbASE-ER4 can support up to 40 km. However, owing to its large size and high power consumption, CFP transceivers are less popular on the market. If you want to use CFP optics for 100G deployment, keep in mind, CFP modules are too large to fit in the Ethernet switches and will significantly reduce port counts and increase power usage, making 100G switches poor performance in cost-effectiveness. Therefore, customers who want to upgrade 100G network can only cover a distance of 10 km, which is obviously insufficient for geographically separated data centers or metro infrastructures. Figure 2 shows the basics of DWDM system.

DWDM-System

To realize 100G long-distance transmission, Arista 100G DWDM solution combines DWDM optics with a fully passive Mux/Demux system that can handle up to 3,000 km. Arista 100G DWDM solution is a 6 x 100G Coherent DWDM line card for the 7500E series with integrated wire-speed encryption and analog coherent CFP2 optical interfaces. Several use cases for the Arista 7500E Series DWDM card in multi-site data center networks exist. The following sections identify three use cases for Arista 7500E DWDM solutions.

Use Cases for Arista 7500E DWDM Solutions
  • Use Case 1—Less Than 80KM Dark Fiber Connection

For a typical metro link that is less than 80 km, Arista 7500E Series DWDM line cards can directly terminate a dark fiber connection providing a point-to-point connection between two locations.

DWDM solution for 80 km

Just as figure 3 shows, Arista DWDM solution is ideal for metro applications transmitting up to 9.6Tbps traffic without the need for any additional amplification.

  • Use Case 2—Greater Than 80 km But Less Than 150 km

When extending the distance beyond 80 km, there is a need to amplify the signal to offset heavy signal loss that occurred in the light signal when passing through fiber cables, patch panels and other optical devices. Under this circumstance, EDFA’s or Erbium Doped Fiber Attenuators are employed to give the aggregated wave a boost.

100G DWDM solution about 100 km

By using EDFAs (seen in Figure 4) to the transmit side of each end of the dark fiber link, the signal can be boosted to achieve distances of up to 150 km. Exact distances will be dependent on the number of patches, fiber splices and quality of the fiber.

  • Use Case 3—Greater Than 150 km But Less Than 3,000 km

Arista 7500E DWDM solutions can also cover the distance of greater than 150 km but less than 3000 km. Employing further EDFAs at a spacing of approximately 80 km along the fiber route allows the length of a connection to be extended to over 3,000 km. As shown below, EDFAs are used on both paths to boost the signal.

DWDM solution for 3000 km

Supported Optics for Arista 7500E Series

All Arista 10G SFP+ transceivers, with the exception of LRM, are supported on the Arista 7500E SFP+ ports.

Interface Type SFP+ ports
10GBASE-CR 0.5m-5m
10GBASE-AOC 3m-30m
10GBASE-SRL 100m (OM3) / 150m (OM4)
SFP-10G-SR 300m (OM3) /400m (OM4)
SFP-10G-LRL 1km
SFP-10G-LR 10km
SFP-10G-ER 40km
10GBASE-DWDM 80km
SFP-10G-ZR100 100km
100Mb TX, 1GbE SX/LX/TX Yes

The 40G QSFP+ transceivers and cables allow for 4x10G mode support with the use of fiber breakout cables, MTP to LC cassettes, or QSFP to SFP+ cables. See the below table for details on the latest supported 40G transceivers.

Interface Type QSFP+ ports
40GBASE-CR4 0.5m-5m
40GBASE-AOC 3m-100m
QSFP-40G-UNIV 150m (OM3) / 150m (OM4), 500m (SM)
QSFP-40G-SRBD 100m (OM3) /150m (OM4)
QSFP-40G-SR4 100m (OM3) / 150m (OM4)
QSFP-40G-XSR4 300m (OM3) / 400m (OM4)
QSFP-40G-PLRL4 1km (1km 4x10G LR/LRL)
QSFP-40G-PLR4 10km (10km 4x10G LR/LRL)
QSFP-40G-LRL4 1km
QSFP-40G-LR4 10km
QSFP-40G-ER4 40km

100G QSFP28 and CFP2 Optics

Interface Type 100G CFP2 Ports 100G QSFP Ports
100GBASE-XSR10 300m OM3 / 400m OM4 Parallel MMF
100GBASE-SR4 100m OM3 / 150m OM4 Parallel MMF
100GBASE-LR4 10km SM Duplex 10km SM Duplex
100GBASE-LRL4 2km SM Duplex
100GBASE-ER4 40km SM Duplex
100GBASE-CWDM4 2km SM duplex
100GBASE-PSM4 500m SM Parallel
100GBASE-AOC 3m to 30m
100GBASE-CR4 1m to 3m
Conclusion

Arista 7500E DWDM solution works in conjunction with passive Optical Mux/Demux devices and in-line amplifiers to support additional bandwidth and extended reaches. Arista 7500E DWDM solution can directly reach up to 80 km without requiring in-line amplification, which is ideal for metro applications. With an Optical Signal to Noise ratio (OSNR) of 11.6dB, it can be used effectively for point to point long-haul applications up to 3,000kms with in-line amplifiers and multiplexers.

How to Choose QSFP28 Optics for 100GbE Deployment

How to Choose QSFP28 Optics for 100GbE Deployment

As we know, QSFP28 is considered to be the mainstream form factor in today’s 100GbE optics market. There are many products with QSFP28 form factor include QSFP28 DAC (Direct Attach Copper) cables, QSFP28 AOCs (Active Optical Cables) and QSFP28 transceivers with various interface options, like SR4, LR4, PSM4, CWDM4, etc. Among these QSFP28 products, which one is the best for your data center 100GbE deployment? The selection of the most suitable 100G QSFP28 product depends on a few factors. The most basic factors may be the transmission distance you may want to reach and cable types you plan to use.

100G-distance

Copper DAC Used Inside Racks: 1-5 m

QSFP28 passive DAC products include QSFP28 to QSFP28 DACs and QSFP28 to 4x SFP28 DACs are ideal to use for reaches within 5 m, providing a very cost-effective I/O solution for 100GbE connectivity. In stead of discrete components, QSFP28 DACs offers a complete cable assembly for short distance connectivity in a cost-effective manner. If your 100GbE deployment is within 5m intra racks, the QSFP28 DAC is ideal for you.

Multimode Fiber Use Between Switches: 5-100 m

For 100GbE cabling with multimode fiber between switches, there are two options. One is to use QSFP28 AOC which is the best fit for 3-20 meters. And the other option is to use QSFP28 SR4 transceiver with 12-fiber MTP OM3/OM4 cable. QSFP28 SR4 with 12-fiber OM4 MTP fiber cable can support reaches up to 100 m. If you want to use multimode fiber for connectivity, you could choose either QSFP28 AOC or QSFP28 SR4 transceiver with 12-fiber MTP cable. This depends on your reaches and cost consideration.

Single-Mode Fiber Use Between Switches: >100 m-2 km

Reaches over 100 m but less than 2 km are usually called mid-reaches. For most large data center operators, a 100GbE solution which can satisfy the mid-reach connectivity in a cost-effective way is their sweet-spot. PSM4 QSFP28 and CWDM4/CLR4 QSFP28 (view difference between CWDM4 & CLR4) transceivers which can respectively support up to 500 m over 12-fiber MTP single-mode fiber cable and 2 km over duplex LC single-mode fiber cable are recommended here. For more details about PSM4 and CWDM4 in 100G Ethernet, you can visit the previous post by clicking here.

Single-Mode Fiber for Long Span: ≤10km

For very long span 100GbE deployment, such as connectivity between two building, mostly up to 10 km, QSFP28-100G-LR4 with duplex LC single-mode fiber cable is the preferred option defined by IEEE. But now, cost of QSFP28 LR4 is still very high.

Summary

After reading the above content, do you know what is best for you now? FS.COM offers a full series of QSFP28 products and professional service for you which helps you with your worry on 100G QSFP28 optics selection. For more information, please visit www.fs.com or contact sales@fs.com.

Related Article: 100G CFP AND QSFP28 MODULES’ FUNCTIONAL MODE COMPARISON