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The New Darling of HPC Data Center — 100G QSFP28 CLR4 Optical Module

With the advent of 5G era and the rapid development of AI industry, HPC data centers supporting intelligent algorithms and in-depth learning will be more applied to the business field. For data center interconnection, the research and development of optical transceiver modules applied in HPC scenario has to be paid attention by practitioners. As a global optical interconnection design innovator, the Gigalight company recently launched such a HPC optical transceiver module — 100G QSFP28 CLR4.

The Background of the Birth of 100G CLR4

The 100G QSFP28 CWDM4 transceiver is currently the most widely used optical module in data centers, such as Facebook, Alibaba and Tencent, as the preferred option for optical interconnection within 500m to 2km distances. Due to the low cost of CWDM4 lasers and Mux/Demux devices, the 100G CWDM4 solution is more competitive in 2km transmission scenario than 100GABSE-LR4 solution. However, the application of CWDM4 in the field of HPC is often stretched, because HPC data centers not only need optical modules to meet the requirements of large bandwidth, but also the characteristics of low delay and strict signal transmission quality. Then the CLR4 Alliance arises at the historic moment.

Facebook Data Center 100G QSFP28 CWDM4 Module
100G QSFP28 CWDM4 Used in Facebook Data Center

The 100G CLR4 MSA is a 100G standard developed by the 100G CLR4 Alliance. Enterprise organizations including Altera, Fujitsu, Macom, Neophotonics, Oclaro and so on have joined the 100G CLR4 Alliance. According to the 100G CLR4 Alliance led by Intel and Arista Network, the 100G QSFP28 CLR4 optical module is very suitable for connecting the super-large data center with a span of 100m to 2km.

Members of 100G CLR4 Alliance
Members of 100G CLR4 Alliance

Why Is 100G QSFP28 CLR4 More Suitable for HPC?

In data communication, in order to prevent external signal interference and protect the signal from changing, multiple error correction codes should be set up. In the process of decoding, digital signals are very sensitive to error signals. If there is any error code, it can not be decoded. The Forward Error Correction (FEC) function can effectively reduce the bit error rate of digital signal and improve the reliability of signal transmission. It is noteworthy that the optical module itself does not have FEC function. FEC is only for the equipment side, not for the module side.

In fact, there is little difference between 100G QSFP28 CWDM4 and 100G QSFP28 CLR4. Detailed parameters can be referred to the following table. However, unlike 100G QSFP28 CWDM4, 100G QSFP28 CLR4 can be used in both FEC-enabled and FEC-disabled links with greater flexibility. In terms of signal transmission quality, we can see from the table below that the BER of CLR4 is only 1E-12 without FEC, which is much lower than that of 100G QSFP28 CWDM4 with FEC. In addition, the sensitivity and other parameters of CLR4 also have good performance. This means that the CLR4 module is more suitable for HPC data center interconnection than CWDM4.

The Comparison Between 100G QSFP28 CWDM4 and 100G QSFP28 CLR4
The Comparison Between 100G QSFP28 CWDM4 and 100G QSFP28 CLR4


Within the range of 500m to 2km in the data center, the 100G CLR4 solution is more flexible, and its signal transmission capability is more excellent. It is more suitable for HPC and high frequency trading applications.

Gigalight 100G QSFP28 CLR4 Optical Transceiver
Gigalight 100G QSFP28 CLR4 Optical Transceiver

Based on the market demand of HPC data center, the Gigalight 100G QSFP28 CLR4 optical transceiver module uses self-developed optical engine and integrates four uncooled CWDM DFB lasers, photo-detectors, CDR circuit and miniaturized AWG chip. Its typical power consumption is less than 3.5W at the commercial operating temperature range (0–70℃), which meets the requirements of HPC data center in terms of high quality and high reliability. For HPC data center interconnection, Gigalight will also introduce 100G QSFP28 SR4 optical transceiver module with higher operating temperature range (0–85℃). For details, please check the official website (gigalight.com).

This is an original article wrote by Gigalight. If reproduced, please indicate the source: https://www.gigalight.com/community/the-new-darling-of-hpc-data-center-100g-qsfp28-clr4-optical-module/

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