Deploy 100 Gigabit Ethernet Network With QSFP28

February 8, 2017

Over the past few years, the 100 Gigabit Ethernet technology has become mature, interoperable with broad vendor support, and has been applied in the many networks. Major network suppliers like Cisco, Juniper and Brocade have already provided 100G optics such as 100G optical modules and switches. A variety of standards-based 100G optical transceivers enable network operators to have several choices for media and distances. What 100G optical modules are available, QSFP28, CFP? How they differ from each other? Here is everything you need to know.

Different Types of 100G Optical Transceivers

100G optical transceivers have a number of form factors, such as CFP/CFP2/CFP4, CXP and QSFP28. The letter “C” in CFP/CFP2/CFP4 and CXP stands for 100, as used in “centum.” As for QSFP28 standard, the “Q” is for “Quad”. And the electrical interface for 100G can handle up to 28Gbps, thus being given the name of QSFP28. Just as the 40G QSFP+ is implemented using four 10-Gbps lanes, the 100G QSFP28 transceiver is implemented with four 25-Gbps lanes. Details of these 100G optical transceivers can be obtained in the table below.

Transceiver Types Interface Fiber Type Distance
CFP-SR10-100G MTP/MPO-24 MMF 150m
CFP-LR4-100G LC duplex SMF 10km
CFP-ER4-100G LC duplex SMF 40km
CFP2-LR4-100G LC duplex SMF 10km
CXP-SR4-100G LC duplex SMF 10km
CXP-SR4-100G MTP/MPO-24 MMF 100m(OM3); 150m(OM4)
QSFP-100G-SR4 MTP/MPO-12 MMF 100m
QSFP-100G-PSM4 MTP/MPO-12 SMF 500m
QSFP-100G-LR4 LC duplex SMF 10km
QSFP-100G-CWDM4 LC duplex SMF 2km

Will QSFP28 Be a Better Way to 100G?

Among all the 100G transceivers, QSFP28 is the most popular type on the market, which has been chosen as the core transceivers by most data centers.

100G qsfp28 lr4

More Advantages over Other 100G Optical Modules

Since the need for faceplate densities is increasing, the trend for high-speed 100G optical modules is smaller size, lower power dissipation and higher rate. From the table below, we can see QSFP28 enjoys more advantages than other 100G optical modules in several aspects such as higher port density, lower power consumption, and higher transmission capacity per lane.

Line Rates 12x12G or 10x12G 40/100G 40/100G 40/100G 40/100G 4x25-28G
Applications InfiniBand, Ethernet Ethernet, Sonet/SDH, OTN Ethernet, Sonet/SDH, OTN Ethernet, Sonet/SDH, OTN Ethernet, Sonet/SDH, OTN InfiniBand, Ethernet
Hot Pluggable Yes Yes Yes Yes Yes Yes
Dimensions (WxLxH, mm) 21x29 82x145x14 41x104x13 34.8x101.2x11.6 22.92x10 18x52x8.5
Electrical Interface 12xQDR Infiniband or CPPI CAUI, XLAUI, SFI-S, SFI-5.2 CAUI-4, CAUI CAUI-4, CAUI CPPI-4 CPPI-4
Max Power 6W 3-18W 3-18W N/D 1.5-6W 3.5W

Cost-effective Way for Upgrading from 25G to 100G

The emergence of QSFP28 has changed the 100G upgrading road from 10G→40G→100G to 10G→25G→100G. As it has been mentioned before, QSFP28 uses four 25G lanes to transmit signals, which is accordance with the 100G Ethernet standards. The 100G uplink is converged by only four 25G links. In addition, the 25G network has the same cabling structure as 10G network but larger network capacity. Thus the 100G road map with QSFP28 from 10G to 25G to 100G can largely simplify the cabling in data center and effectively decrease the cable density and the cost.

Also, by deploying 25G/100G, data center operators can upgrade to spine-and-leaf infrastructure for growing server/storage workloads. Compared with traditional three-layer topology, spine-leaf topology design only has two layers–the leaf layer and spine layer. The picture below displays a spine-leaf network constructed by 100G data center switches from FS.COM with N8500-32C serving as the spine switches and N8500-48B6C as the leaf switches. Every leaf switch is interconnected with every spine switch. This new topology allows all connections to run at the same speed, and the mesh of fiber links creates a high-capacity network resource that is shared with all attached devices.

spine-and-leaf infrastructure

100G Is Affordable Now. How About 200G and 400G?

It’s undeniable that the cost of 100G transceivers and switches are still higher than the common 10G or 40G optics as you see in many data centers. But don’t worry. 100G transceivers will continue to be more affordable, making the cost difference between 40G and 100G even small. On one hand, the cheap 100G silicon reaches production and the technology become mature. On the other hand, the adoption of widespread use of the 100G devices, and the vast increases in Internet traffic are core to change in the communications infrastructure markets. In fact, the prices for 100G optical modules have been dropping faster than 40G optical transceivers. An early report forecasted that expenditures on 100G optical modules would be under $3 per gigabit by the end of 2017. While the truth is that for some third-party suppliers like FS.COM, they can already provide QSFP28 at $199, even less than $3 per gigabit.

100 Gigabit Ethernet is the unstoppable trend for the future network and QSFP28 can provide a cost-effective way for upgrading to 100G. What about higher speed beyond 100G? Attentions from IT community have already been paid to 200G and 400G. To know more about 200G and 400G development, please read this article: Global Optical Transceiver Market: Striding to 200G and 400G.

Related Article: Decoding 100G QSFP28 Fiber Optic Transceiver

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