Do You Know Enough About The 100GBASE LR4 Module?

Over the past few years, demand for 100GBASE LR4 optical modules has grown tremendously. More people are discovering great manufacturers of these modules such as QSFPTEK. Several trends have driven the exploding demand, including the rapid increase in the number of people working from home, increased video conferencing, video-on-demand services, and the development of 5G mobile networks. Several 100G modules exist with the 100G QSFP28 LR4 being quite popular.

This module has a lot going for it including its small size and power efficiency. In this article, we will describe the 100GBASE LR4 optical transceiver in great detail.

Defining The 100GBASE LR4

First things first, what is the 100GBASE LR4? This optical module, commonly referred to as simply the 100G LR4, is a small form-factor pluggable transceiver that operates in four-channel mode over a full-duplex connection. The QSFP28 LR4 transfers data long distances up to 10 kilometers. The optical module uses light in the 1295-1310nm wavelength.

This transceiver is a staple in large-scale data centers that require not only range but speed. The 100GbE QSFP28 transceiver complies with the IEEE 802.3ba standards.

100G QSFP28 LR4 module 

How Does The 100GBASE LR4 Operate?

This optical transceiver turns 4, 25Gbps signals into 4 LAN WDM light pulses then uses its multiplexer to combine them to one 100G channel for transmission over fiber cables. After the transmission is completed, the QSFP28 LR4 demultiplexes the 100G signal to four 25G optical signals and turns them into electrical signals that can be received by the connected device.

The 100G LR4 uses a single-mode fiber cable with an LC connector.

QSFP 100GBASE LR4 Connectivity Options

Many large data centers and enterprises have completed their transition from slower 10G and 40G connections. The 100G LR4 is a preferred option for these data-hungry applications because of its great balance between range and throughput.

100GBASE LR4 Device To Device Connection

Similar to the connections, it came to supersede, the 100GbE QSFP28 module is easy to set up for direct connection. All you need to make this connection are two 100G QSFP28 LR4 transceivers with LC duplex SMF fiber cables in between.

100GBASE LR4 Connection With Server Rack Mount Enclosure

If you want to create high port density using the 100gbase lr4, you can use breakout cables connected to rack-mount cable enclosures. The enclosures make it easier to create structured cabling solutions.

Comparing 100GBASE LR4 With 100G LR

The QSFP 100G LR4 specification has been around since 2010. Ther is a new connection standard simply called the 100G LR. Both these optical modules belong to the 100 Gbps family and both have a range of 10 kilometers over full-duplex cables. However, that’s about where the similarities end.

The “4” in LR4 means that the module uses four different wavelengths, one for each of the 25G channels. During this time, the CFP form-factor was also developed. The module worked by converting 10G signals from a switch to 25G-lane optical signals. This conversion was done in circuits within the optical module. The need for these additional circuits makes the CFP one of the largest optical modules on the market. It was, however, adopted by networks that needed 100G connections immediately for their uplinks.

The Advent of QSFP28

Many years later, data centers and other enterprises developed the need for 100G. They previously hadn’t jumped at the CFP modules but the technology has now matured to produce smaller modules they could work with. An example is the CPAK module from Cisco which was small because it didn’t need much-advanced functionality.

Manufacturing techniques had also improved greatly and now much smaller ICs could be made to do a lot more work. At this point, the qsfp28 form-factor was developed. It was smaller than the CPAK module and more widely compatible. The QSFP28 LR4 was exactly what the industry needed.

The QSFP28 module could use the forward error correcting algorithm that is housed in host devices. By using the forward error correction, modules could now work with poorer bit error rates. As a result, the modules didn’t require very high performance. Soon there was a proliferation of host devices that supported QSFP28 and the popularity of the form-factor could only increase from there.

Introducing The 100G LR

One of the newest entrants to the optical transceiver space is the 100G LR. This module can transmit the full 100 Gbps using a single wavelength of light. This is possible because of PAM4 modulation. However, because of the susceptibility of PAM4 to noise, the KP4 forward error correction was developed. This algorithm resides in the optical module, which is important if it is to be compatible with 100G QSFP28 LR4 platforms.

So, what’s the main difference between 100G LR and QSFP28 LR4? The LR without the 4 is a single-Lambda 100G module that only uses one channel for the entire 100Gbps. It will therefore offer easy migration to 400G networks. Its size should also be of similar size to the 100GBASE LR4 modules. It will therefore surpass the QSFP28 LR4 faceplate density.

How Does The 100G LR4 Differ From SR4?

The main difference between them is range. The 100GBASE-SR4 has a maximum range of 100 meters using OM4 fiber while the 100GBASE LR4 can transmit over 10km on OS2 fiber.

With the LR4, every cable carried four distinct signals at different wavelengths. They are mux-/ de-muxed for transmission. This transfer method means that an LR4 transceiver requires only 2 cables compared to the 8 required by the SR4.

100G QSFP28 SR4 module


The 100GBASE LR4 is an ideal choice for transferring data over long distances. Its use of optical multiplexing/demultiplexing reduces the number of physical cables required to transmit data, therefore, reducing cost and power consumption. To get a list of high-performance transceivers to buy, visit QSFPTEK. Their extensive experience manufacturing optical transceivers has put them at the forefront of compatible SFP manufacturing. Send them your orders and inquiries to today.

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