100G QSFP28 PSM4 to Address 500m Links in Data Center

100G QSFP28 PSM4 optics is a type of 100G optical transceiver that provides a low-cost solution to long-reach data center optical interconnects. 100G PSM4 (parallel single-mode 4 lane) standard is mainly targeted to data centers that based on a parallel single-mode infrastructure for a link length of 500 m. Compared with the hot-selling 100GBASE-SR4 and 100GBASE-LR4 optics, 100G QSFP28 PSM4 recently wins the popularity among the overall users. This article will provide a complete specification of the 100G QSFP28 PSM4 transceiver and explain the reason why people would need QSFP28 PSM4.

QSFP28 module

QSFP28 PSM4—A Low-Cost but Long-Reach Solution

100G QSFP28 PSM4 is compliant with 100G PSM4 MSA standard, which defines a point-to-point 100 Gb/s link over eight parallel single-mode fibers (4 transmit and 4 receive) up to at least 500 m. PSM4 uses four identical lanes per direction. Each lane carries a 25G optical transmission. The 100G PSM4 standard is now available in QSFP28 and CFP4 form factor. Table 2 shows the diagram of the 100G QSFP28 PSM4 Specification. 100G PSM4 is a low-cost solution. Its cost structure is driven by the cost of the fiber and the high component count. FS.COM offers the Cisco compatible 100G QSFP28 PSM4 at US$750.00.

diagram of QSFP28 PSM4

As you can see in the above image, 100G QSFP28 PSM4 transceiver uses four parallel fibers (lanes) operating in each direction, with transmission distance up to 500 meters. The source of the QSFP28 PSM4 module is a single uncooled distributed feedback (DFB) laser operating at 1310 nm. It needs either a directly modulated DFB laser (DML) or an external modulator for each fiber. The 100GBASE-PSM4 transceiver usually needs the single-mode ribbon cable with an MTP/MPO connector.

Why Do We Need 100G QSFP28 PSM4?

100G PSM4 is the 100G standard that has been launched by multi-source agreement (MSA) to enable 500m links in data center optical interconnects. But as we all know, there are several popular 100G interfaces out there on the market, such as QSFP28 100GBASE-SR4, QSFP28 100GBASE-LR4, QSFP28 100GBASE-CWDM4, and CFP 100GBASE-LR4, etc. So with so many options, why do we still need 100G QSFP28 PSM4?

To better help you make up your mind, you need to figure out the following questions:

Q1: What are the net link budget differences between PSM4, SR4, LR4 and CWDM?
Table 3 displays the detailed information about these 100G standards.

4-wavelength CWDM multiplexer and demultiplexer No need Need No need Need
Connector MPO/MTP connector Two LC connectors MPO/MTP connector Two LC connectors
Reach 500 m 2 km 100 m 10 km

Note: the above diagram excludes the actual loss of each link (it is the ideal situation). In fact, WDM solution are at least 7 db worse link budget than PSM4. For a 2 km connectivity, a CWDM module will have to overcome about 10 db additional losses compared to PSM4. And the 100G LR4 optics at 10 km is 12 db higher total loss than PSM4.

Q2: What power targets are achievable for each, and by extension what form factors?
According to the IEEE data sheet, the WDM solutions cannot reasonably fit inside QSFP thermal envelop, while PSM4 can fit inside the QSFP thermal envelope. That means you would need the extra power for the WDM solution of your network. But if you use the QSFP PSM4, this won’t be a problem.

All in all, a 100G QSFP28 PSM4 transceiver with 500m max reach is a optional choice for customers. Because other 100G optics are either too short for practical application in data center or too long and costly. QSFP28 PSM4 modules are much less expensive than the 10 km, 100GBASE-LR4 module, and support longer distance than 100GBASE-SR4 QSFP28.


QSFP28 PSM4 is the lowest cost solution at under one forth the cost of either WDM alternatives. 100G QSFP28 PSM4 can support a link length of 500 m, which is sufficient for data center interconnect applications. 100G QSFP28 PSM4 also offers the simplest architecture, the most streamlined data path, higher reliability, an easy upgrade path to 100G Ethernet.

100G Direct and Breakout Cabling Solutions

With the emerging high-speed network standards and rapidly advancing technology, fiber optic network is driven to meet the growing demand for faster access to larger volumes of data. Although 10G/40G Ethernet becomes the mainstream of telecommunication market nowadays, organizations of all sizes still need to be prepared to integrate speeds of 100G and beyond. For data center networking, users can choose different solutions based on the different transmission distance need. In general, there are two kinds of 100G fiber optic solutions: direct cabling and breakout cabling. It is essential for users to understand the detailed information of each type of solution in order to select the one that meets their current and future connectivity needs.

How 100G Optics Develop

After the IEEE completing the certification of the first 100G standard for Ethernet networks, the transceiver industry launched a new type of form factors for 100G connectivity—CFP (“C” for 100, and FP for Form factor Pluggable). Compared to the most popular 40G QSFP, the size of CFP transceiver is huge. And most CFP implementations doubled the power consumption per bit. Furthermore, the price per bit increased by a factor of ten. These disadvantages becomes the main obstacles of the popularity of 100G CFP transceivers.

The next version of 100G form factors is the CFP2, CFP4, and the CPAK that are improved upon the CFP. But when compared to the popular 10G SFP+ and 40G QSFP+, none of these new members of the CFP family improved density, power consumption, or cost. Fugure 1 shows the size comparison between CFP2, CFP4 and QSFP28 modules.


Then here came the 100G QSFP28. The QSFP28 is the exact same footprint as the 40G QSFP+. The 100G QSFP28 is implemented with four 25-Gbps lanes, Just as the 40G QSFP+ is implemented using four 10-Gbps lanes. In all QSFP versions, both the electrical lanes and the optical lanes operate at the same speed, eliminating the costly gearbox found in CFP, CFP2, and the CPAK. The 100G QSFP28 makes it as easy to deploy 100G networks as 10G networks. When compared to any of the other alternatives, 100G QSFP28 increases density and decreases power and price per bit. That’s why it is fast becoming the universal data center form factor. The following part will move on to talk about the 100G optic cabling solutions.

100G Direct Cabling Solutions

QSFP28 transceiver utilizes either fiber or copper media to achieve 100GbE communication in each direction. This transceiver has 4 individual 25GbE lanes which can be used together to achieve 100GbE throughput or separately as 4 individual 25GbE connections (using 4 SFP28 modules).

For 100G short-reach direct cabling within 100m, 100GBASE-SR4 QSFP28 optical module and 100G QSFP28 cable are good choice. Just from the table list of FS.COM 100G optical modules and cables, we know that 100GBASE-SR4 QSFP28 modules can support up to 100 m on OM4 12 fiber multimode MTP cable. And 100G QSFP28 to QSFP28 direct attach copper cable can support up to 5m and 100G QSFP28 to QSFP28 active optical cable can support up to 10m. Figure 2 describes a 100G direct cabling with the use of QSFP28 to QSFP28 DAC and AOC cables.


For 100G long-haul direct cabling, like 10km, both 100GBASE-LR4 QSFP28 optical module and 100GBASE-LR4 CFP4 transceiver can support up to 10km on single-mode LC patch cables. For longer 100G direct cabling above 10km, the 100GBASE-ER4 CFP is the ideal choice as their transmission distances support up to 40 km.

100G Breakout Cabling Solutions

A breakout cable is a multi-strand cable, typically custom-made, which is divided into multiple duplex cables. For instance, a 40G breakout cable has four individual 10G duplex cables totaling eight strands, while a 100G breakout cable has 10 duplex cables and 20 strands. Figure 3 displays a simple 100G connectivity with 100GBASE-SR4 QSFP28 and QSFP28 to 4SFP28 breakout cables.


Between the 100G optical module and 25G optical modules, there always uses the breakout cables connected the two kinds of optical modules, and the common cable solutions are 100G QSFP28 to 4SFP28 Breakout AOC cables or 100G QSFP28 to 4x 25G SFP28 Breakout Direct Attach Passive Copper Cables.

The commonly used 100G breakout cabling solutions is 100G QSFP28 to 4SFP28 DAC. It’s easy to understand how this type of cable function. Just as the QSFP+ breakout cable, the 40GBASE-SR4 QSFP+ optical module at the one end can be connected to 4x10GBASE-SR SFP+ optical modules at the other end.


As IT infrastructures are planning to migrate to 100G data rate, network designers must carefully weigh alternative implementations of such links. With a variety of fibers already deployed, it is important to understand the interoperability of new optics with existing fibers. And for 100G deployment, you are supposed to understand the benefits and challenges of each type of the fiber optic solutions before taking an action. FS.COM’s 100G FHD series covers a full range of 100G optical transceivers and cables, like CFP, CFP2, CFP4, QSFP28, as well as 100G QSFP28 to QSFP28 DAC, 100G QSFP28 to 4SFP28 DAC. Besides the above products, 100G FHD Fiber Enclosures, 100G FHD MTP Modular Cassettes, 100G 160 Fiber 2U Panels and 100G CFP SR10 Cables are also provided. If you want to know more about our products, please contact us directly.

Stay For 40Gbps Network or Scale Up to 100G?

The evolution of bandwidth for data transmission is unstoppable. From the 10Mbps, 100Mbps Ethernet to the 10G or 40/100G Ethernet, telecom manufacturers keep promoting higher internet speed to facilitate people’s daily life. Now, bandwidth speeds of 1Gbps to 10Gbps Ethernet capacity are commonly utilized around the world. However, with the increase in data center and cloud computing technologies, the demand for bandwidth speeds of 40G to 100G Ethernet is growing steadily for carriers and other data consumers.

Just like the dilemma of whether to use the fiber optic cable for high performance or adopt copper cable for the low cost, these high-end data consumers also have the doubt about 40G and 100G. Should we upgrade our capacity to 40Gbps or skip 40Gbpsand migrate directly to 100Gbps Ethernet? This article will help to draw an answer to this dilemma from the aspects of market trend for required bandwidth, cost and performance.

Upgrade Straight to 100G

According to today’s market trend, the tendency is to skip 40Gbps. With demanding users peeling off multiple 10Gbps channels, the 40Gbps pipe becomes quickly utilized. Carriers scaling up to 100Gbps, allows greater flexibility for one’s network infrastructure utilizing multiplexing solutions to carve multiple bandwidth channels from a single pipe. On another scale, the same is true for the consumer market where capacity is increasing from 1Gbps to 10Gbps, skipping 2.5Gbps levels, due to the flexibility and scalability 10Gbps provides at a very similar cost. In many cases, carriers and consumers have decided to skip 40Gbps and acquire 100Gbps for the following reasons and benefits:

100G logo

  • Cost Efficiency—From a network equipment standpoint, often it may be more cost-efficient to upgrade a 10Gbps link to 100Gbps, versus 40Gbps. Essentially, if you should require 60Gbps or say even 80Gbps, additional cards would be needed to support the link in the chassis, whereas a customer may utilize only one card to achieve more than twice the bandwidth at 100Gbps. 100Gbps allows the network to operate within a smaller footprint of a data center, which in turn, reduces power consumption dissipating less heat and thus lower operational costs.
  • Lower Latency—100Gbps provides lower latency capabilities than 40Gbps; many carrier grade vendors are lowering latency on 100Gbps matching latency of traditional 10Gbps traffic.
  • Flexibility—Creates options to provide multiple variations of delivery with handoffs ranging from 10Gbps, 40Gbps or the full 100Gbps pipes.
  • Scalability—Although a customer may not utilize 100Gbps on day one, the ability is there to scale the network with no forklift upgrade at any point, future-proofing the solution well beyond capacity needs.

As consumer’s demands for higher bandwidth continues to rise, many equipment suppliers, who developed some of the first 100 Gigabit Ethernet Router Interfaces, are now working on developing 200Gbps, 400Gbps up to 1 Terabyte interfaces.

This article is not implying that there is no use for 40Gbqs bandwidth level technology. Instead, I suggest that many end consumers are looking to keep up with the acceleration of high bandwidth demands while maintaining the efficiency and technologies needed to support their network infrastructure requirements while reducing operating costs.

100G Optic Solutions

FS.COM 100G transceiver solution offers customers 100 Gigabit Ethernet connectivity options for data center networking, enterprise core aggregation, and service provider transport applications. Various of 100G transceivers including CXP, CFP, CFP2, CFP4 and QSFP28 are available for different applications. The following part will lists two cost-effective 100G solutions.

  • QSFP28 to QSFP28 Interconnection

The QSFP28 is the exact same footprint as the 40G QSFP+, but is implemented with four 25Gbps lanes. To interconnect a multimode QSFP28 link, a 12-fiber MPO/MTP patch cable is required, while for single-mode link (100GBASE-LR4 QSFP28), a duplex LC single-mode patch cable is required. The interconnection of QSFP28 multimode link is similar with the case of QSFP28-100G-SR4 see in the following figure.

100G solution

  • CXP/CFP to CXP/CFP Interconnection

FS.COM’s 24-fiber MPO/MTP assemblies are ideal for 100GBASE-SR10 CXP/CFP to CXP/CFP interconnection in data center, since it is implemented 10 lanes of 10 Gbps. Among the 24 fibers, only 20 fibers in the middle of the connector are used to transmit and receive at 10 Gbps and the 2 top and bottom fibers on the left and right are unused. The following picture shows the interconnection between two 100GBASE-SR10 CXP ports.

CFP to CFP Interconnection

FS.COM provides a full selection of 100G optics including CFP, CFP2, CFP4, QSFP28 (QSFP28-100G-SR4) and QSFP28 DAC cables just as listed above. All of our products are fully compatible with the original brand. In addition, our 100G transceivers offer significant advantages over existing solutions in terms of reduced power dissipation and increased density with the added benefit of pluggability for reduced first installed cost. If you have any requirement, you can send your request to us.