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.

100G Single-Mode Modules for Short Distance Transmission

As bandwidth demand continues to grow, network service providers are looking at 100G Ethernet network to accommodate the constant traffic surge. This new technology translates into greater speeds and a possible network infrastructure upgrade to compensate for various challenges that do not apply to slower networks, such as 10G, or 40G. 100G Ethernet provides high-speed connectivity while protecting current network infrastructures that requires broad expertise and wide-range testing to qualify the state of the fiber, perform fiber characterization and assess the integrity of data transmission over long-haul and ultra-long-haul networks. In response to 100 Gigabit Ethernet, many famous telecommunication companies, like Cisco, have delivered industry-leading, standards-compliant, 100G pluggable transceiver modules, such as single-mode QSFP-100G-LR4 for the transmission distance up to 10 km and multimode QSFP-100G-SR4 for the transmission up to 100 m. How about single-mode 100G modules for the transmission distance less than 2 km? Today, we’re going to introduce two 100G interfaces over single-mode fiber for short distance transmission: 100GBase CWDM4 and 100GBase PSM4.

The Development History of 100GBase CWDM4 and 100GBase PSM4

The IEEE standardized a cost-effective 100m solution known as “SR4”. Beyond 100m, there is only the “LR4” standard, which is targeted to achieve 10km. Customers, particularly hyperscale data centers are looking for solutions up to 2 km. To response, in 2014, a new industry group CWDM4(coarse wavelength division multiplexed 4x25G multi-source agreement) MSA which is consisted of Avago Technologies, Finisar Corp, JDSU, Oclaro, and Sumitomo Electric, announced the formation of an industry consortisum dedicated to defining specifications and promoting adoption of interoperable 2km 100 interfaces over duplex single-mode fiber, which smooths the process of getting to 100Gb Ethernet.

Like the development history of 100GBase-CWDM4, in order to fill the requirement of low-cost 100G connections at reaches of 500 m in applications that fall in between the IEEE standardized multi-wavelength 10-km 100GBase-LR4 single-mode approach and its multimode-fiber based 100GBase-SR10 short reach specification, six technology vendors aim to promote the creation and adoption of parallel single-mode 4-lane (PSM4) approach to 100G in the data center.

Main Features of 100GBase-CWDM4 and 100GBase-PSM4

100GBase-CWDM4: 100GBase CWDM4 module comply with the requirement of CWDM4 MSA. It is a 100G optical module using CWDM (coarse wavelength division multiplexing) technology with 4 lanes of 25Gbps optically multiplexed onto demultiplexed from a standard duplex G.652 single-mode LC or SC fiber for the link length from 2 meters to at least 2 kilometers. Transceiver modules compliant to CWDM4 MSA specification use a color code to indicate the application. The color code can be on a module bail latch, pull lab, or other visible feature of the module when installed in a system The image below shows the working principle of 100GBase-CWDM4.

100GBase-PSM4: 100GBase-PSM4 is a parallel module which provides increased port density, offering four independent transmit and receive channels, and each channel operates at 25Gbps, resulting in an aggregate data rate of 100Gbps for optical communication applications. It can support the link length up to 500 m over single-mode MPO or MTP fiber. The working principle of 100GBase-PSM4 is shown below.

Which One Is More Cost Effective?

From an optical transceiver module structure viewpoint, PSM4 can be more cost effective, this comes in two reasons: One is that it uses a single uncooled CW laser which splits its output power into four integrated silicon modulators, the other is that its array-fiber coupling to an MTP connectors is relatively simple.

However, from an infrastructure viewpoint, PSM4 would be more expensive when the link distance is long, mainly due to the fact that PSM4 uses 8 optical single-mode fibers, while CWDM4 uses only 2 optical single-mode fibers.

When take these two factors into considerations, a total cost comparison can be qualitatively shown in the figure below. As can be seen in the figure, PSM4 starts with a lower cost due to its lower transceiver cost, but as the link distance increases, its total cost climbs up very fast due to the fact that it uses 8 optical fibers. Besides, if deploying PSM4 modules, the entire optical fiber infrastructure within a data center, including patch panels, has to be changed to accommodate MTP connectors and regular single-mode fiber cables. In addition, cleaning MTP connector is not a straightforward task.

Conclusion

With the requirement for longer distances and higher data transmission speed increases, 100GBase-CWDM4 and 100GBase PSM4 which provide lower-cost, lower power option for what can be referred to as medium-reach distances that is future-proof for the next generations of data transmission speeds. FS.COM offers compatible 100GBase-CWDM4 and 100GBase-PSM4 for many brands at affordable price. You can choose the right one according to your need.