Decoding Four types of 100G QSFP28 Transceiver

With the development of IP-based multimedia service, especially video service, network traffic has been continuously rising. As a result, 40G and 100G have emerged as the key technologies capable of supporting the growth in network bandwidth. After a lengthy period of hype, 40G technologies have finally widely been deployed. And now it is 100G’s turn. While 100G networking may seem excessive to many right now, there are many industries where that 100G speeds are quickly becoming necessary. This post will introduce four QSFP28 transceiver types that are commonly used in 100G data center.

QSFP-100G-SR4

QSFP-100G-SR4 or 100GBase-SR4 QSFP28 optical transceiver is a full duplex, photonic-integrated 100G module, which uses 4 fibers for transmit and 4 for receive, with each lane supporting 25Gbp, providing an aggregated data rate of 100Ggps as shown below on up to 70m of OM3 MMF and to 100m of OM4 MMF. Like 40GBase-SR4, 100Gbase-SR4 uses a MPO 12 cable with 4 strand for transmit and 4 for receive, allowing for existing 40GBase-SR4 fiber assemblies to be reused when higher performance is needed. This interface standard has been introduced alongside the 100G QSFP28 offerings now, arriving on the market in order to make any 40GbE to 100GbE upgrade as seamless as possible.

QSFP-100G-LR4

QSFP-100G-LR or 100GBase-LR4 QSFP28 is another 100G standard, which focuses on longer data transmission up to 10km over single-mode fiber. Like 40GBase-LR4, the 100GBase-LR4 is also a multilane optic. However, each lane’s data rate is increased to 25Gbps. It has duplex LC interface and uses WDM technologies to achieve 100G dual-way transmission over four different wavelengths around 1310nm that can be seen in the image below.

QSFP-100G-PSM4

Targeted to service the need on a parallel single-mode infrastructure, QSFP28 PSM4 module is a low cost solution to long reach data center interconnect. It uses four parallel fibers (lanes) operating in each direction, with each lane carrying a 25G optical transmission as shown below. Interfaced with MPO connector, it can support distance up to 500 meters over single-mode fiber, which covers a wide rage of applications in data center.

QSFP-100G-CWDM4

Backed by the CWDM4 MSA Group, QSFP28 CWDM4 is a 100G interface that address data communication links up to 2km in the data center. The CWDM4 architecture employs 4 lanes of 25Gbps using CWDM technology to transport 100G optical traffic across duplex LC single-mode fiber. Compared to 100GBase-LR4, CWDM4 is an alternative for long transmission distance in data center. The working principle can be seen in the following image.

Summary

100G Ethernet is no longer a fantasy, and it is on the way. QSFP28 is a key to the 100G deployment. In the part above, we have introduced four types QSFP28 modules widely used in 100G network. All of these modules that have been tested and are 100% compatible can be purchased in FS.COM. If you have any related requirement, kindly visit FS.COM.

Why Should We Choose SMF for Future-Proof Data Center Cabling?

When choosing fiber optic cable, users will always be in a delimma: single-mode or multimode, which one should we choose? Although multimode is cheaper in price, many facts indicate that single-mode cabling is better for future-proof data center cabling.

MMF: A Penny Wise but A Pound Foolish

Price is always the first factor that customers will take into consideration when purchasing products. Generally, the SMF itself is cheaper than MMF fiber ($1.10/meter vs. $3.70/meter for 24-strand OS2 vs. OM3 in FS.COM, and if you use SMF with LC interface and MMF with MTP interface for 40/100G, the price difference between SMF and MMF will be much great, 1M LC fiber cable vs. OM3 MTP fiber cable is $2.8 vs. $38 ), but the optics we should use with SMF vs. MMF are usually a bit more expensive. Take FS.COM as an example, SMF SFP vs. MMF SFP is $7 vs. $6, SMF vs. MMF SFP+ is $34 vs. $16, and with the increase of data rates, the price gap between SMF and MMF optics will be widen. We can get more detailed information from the table below.

From the price comparison between SMF and MMF cabling. You did save an amount of money to install MMF cabling, but you should consider the data rates that the MMF can support. In fact, in most cases, currently deployed MMF cabling is unable to support higher speeds over the same distance as lower-speed signals as shown in the table below since its cabling support for higher bit rates is limited by its large core size. As data traffic grows and interconnectivity speeds increase, the distance between connections must decrease, so the operators will be forced to constrain either the physical size of the data center or the connection speed between its nodes, which is unacceptable for most growing data centers. Besides, higher transmit rates will appear to meet more bandwidth requirements, IT managers will face with replacing an obsolete fiber plant, which will cause unexpected cabling costs.

SMF Serves as an Alternative

Unlimited Bandwidth and Longer Distance: Unlike MMF, SMF cabling deployment support unlimited bandwidth, all but eliminating the capacity bottleneck. With unconstrained headroom, operators can safely settle into a network architecture with server interconnects that will scale with the data center. Many large data center operators, like Google and Microsoft have consciously adopted an SFM fiber cabling strategy in order to remove the network connectivity and speed constraints of a MMF plant.

Decreasing Cost: While using SMF cabling has historically been more expensive than using MMF, technologies advances have fundamentally changed the pricing structure. For example, price difference between 100G SMF and MMF optics is great, normally $2800 vs. $400, but there are newly designed 100G SMF optics, like QSFP28 PSM4 and QSFP28 CWDM4 as shown below, which is ideal for use for large data center. As the development of technology, the price for SMF cabling will continue decreasing.

Consistency: Single-mode cabling is used for external data center communication. By extending SMF into the data center, operators can leverage a consistent cable plant throughout the data center. Standardizing on a single cable plant will drive down sparing costs and reduce operational overhead.

Summary

Choosing SMF or MMF is forcing operators to choose between today and tomorrow. Although MMF provides tempting lower prices, it is not a long-term available solution. Operators should take the advantage of SMF’s limitless traffic carrying capacity and signal reach without incurring unnecessary cost overhead.