Enhancing 25G Fiber Optic Communication with Advanced FEC Techniques

Posted on Jan 26, 2024 by

What Is Forward Error Correction?

FEC, short for Forward Error Correction, is a technology used for detecting and correcting errors in data transmission. Simply put, it allows the receiving end to correct errors in the transmission without the need to resend data. To fully leverage the capabilities of FEC, however, it is essential to understand its principles and application scenarios correctly.

FEC works by adding redundant information to the data. During transmission, the sending end includes extra bits to enable the receiving end to detect and correct any errors upon receiving the data. This preventive approach can significantly improve the reliability of a network.

25G Modules

Why Do 25G Modules Need FEC?

As cloud computing, streaming video, and social networking drive an explosive increase in internet traffic, optical networking is stepping up to exceed 100 Gbps data transmission rates. However, 25Gbps remains a fundamental backbone for high-speed Ethernet and internal data center interconnects, striking a balance between cost-efficiency, power consumption, and technological maturity. Despite being less affected by challenges such as dispersion and noise compared to higher rates, effective solutions are still required to maintain data integrity for 25G transfers.

In optical transmission practices, particularly at 25Gbps, noise can adversely impact an optical receiver's ability to decode information accurately, resulting in errors in data transmission. These issues underscore the necessity for wide bandwidth optical receiver filters to accommodate faster signals, simultaneously allowing more noise to pass through. Herein lies the importance of Forward Error Correction (FEC) technology. FEC works by adding extra error-correcting codes to correct errors that occur during transmission. Although it cannot correct all types of errors, properly configured FEC allows network operators to achieve higher transmission rates while maintaining targeted Bit Error Ratios (BERs), and to do so using more cost-effective optical components.

More specifically, FEC technology for 25G modules helps to reduce design complexity and costs, as it lessens the extreme performance demands on optical components. This ensures that 25G modules are suitable not just for current infrastructures but also display the potential to scale to high-performance networks. In capacity-dense environments, these modules ensure signal quality and system stability are not compromised when scaling up link capacities, thanks to FEC.

Therefore, FEC technology tailored to 25G modules is crucial for preserving data integrity and reliability, increasing overall network efficiency, and reducing long-term operational costs. It ensures that systems maintain a low Bit Error Ratio even under suboptimal transmission conditions, thereby achieving stable and efficient optical transmission.

25G Modules

FEC Matching & Mismatching

The introduction of the 10/25G SFP28 transceiver garnered positive attention. It provides more FEC options for the host switch, router, or server NIC, and its superior optical performance enables support for useful reaches even with weaker FEC algorithms. One often overlooked aspect in system design is the importance of matching FEC types on both ends of a link. Failure to ensure compatibility on both ends may lead to incorrect functionality of the link.

FEC Matching Scenario

All devices, including hosts, switches, transceivers, use the same FEC type.

Example: Both switches use RS-FEC (Reed-Solomon Forward Error Correction).

Communication is smooth because all devices can understand and handle the same types of redundancy and error correction mechanisms.

Data transmission is more reliable because potential transmission errors can be detected and corrected by the end-to-end system.

25G Modules

FEC Mismatching Scenario

Devices use different FEC types or some do not support the FEC type used by others.

Example: One switch uses RS-FEC, while the other uses FC-FEC (Fire Code Forward Error Correction).

Communication can be problematic because mismatched FEC types prevent devices from correctly handling errors.

Data transmission may be unreliable, leading to performance degradation or link failure.

Solutions to Fix FEC Mismatch

  • Ensuring all devices use the same FEC type.

  • Using transceivers or devices capable of supporting multiple FEC types to provide flexibility and compatibility, such as 10/25G CSR (Compatibility Short Reach).

FEC Types Supported by FS 25G Modules

FS offers 25G modules and 10/25G modules, some of which support both RS-FEC and FC-FEC. This dual support ensures that these modules can be flexibly deployed in varied networking environments to meet different error correction requirements.

RS-FEC is highly effective at correcting burst errors and has become a standard for high-speed communication to improve the reliability of data transmission. On the other hand, FC-FEC might be used in scenarios where it is preferred due to legacy system requirements or specific network architecture decisions.

With compatibility for both types of FEC, FS 25G modules provide robust error correction capabilities, allowing for seamless integration with existing network infrastructure and enhancing the overall data integrity and link stability.


In conclusion, Forward Error Correction (FEC) stands as a fundamental technology for ensuring high-reliability data transmission in fiber optic networks. Implementing correct FEC matching across devices is critical for maintaining data integrity and optimizing network performance. FS 25G modules, with their support for both RS-FEC and FC-FEC, offer the versatility needed to accommodate diverse network environments and requirements. By enabling seamless error correction across different system architectures, these modules represent an integral solution for future-proofing network infrastructure, ensuring that it can handle not only current demands but also adapt readily to future technological advancements and traffic growth.

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