Next-Generation Multimode Fiber Technology

The IEEE 802.3cm standard for 400 Gb/s over multimode fiber makes cost-effective, shorter reach optics a reality for hyperscale and cloud data centers. Andy Jimenez, vice president of technology at Anixter, discusses the use cases and technical objectives in this video.

To learn more, read our TECHbrief on next-generation multimode fiber

Transcript: Next-Generation Multimode Fiber Technology

Hi, I’m Andy Jimenez.

The last decade has witnessed a shift in the enterprise data center market from the traditional owner-operated model towards off-premise colocation and cloud facilities, which has powered one of the greatest growth engines the tech industry has ever seen. Data center network infrastructure has evolved to support customer adoption of off-premise solutions, plus the explosion of devices connecting to the network. While data transmission speed is still king, low latency must also be a principal objective when designing a data center for high performance, flexibility, and scalability.

In many instances, single-mode fiber provides the optimal cabling solution for hyperscale and cloud data centers. With the publication of the IEEE 802.3bs standard in 2017, the IEEE standardized on 200 Gb/s and 400 Gb/s optical interconnects that can operate up to 10 km in distance, using single-mode fiber. The data rates and longer physical reach make single-mode fiber an attractive option for these types of facilities. However, there may be situations where cost-effective, shorter reach optics based on multimode fiber technology would be a better fit. Under this premise, the IEEE has established a new project to develop a 400 Gb/s standard called the IEEE 802.3cm, the “Standard for Physical Layer and Management Parameters for 400 Gb/s over Multimode Fiber.”

One of the primary use cases for multimode fiber is in the switch-to-switch connections of a leaf-spine network architecture. This architecture is favored in many hyperscale data centers, as it provides for very high data rate, low latency connections between servers. In this 2-layer architecture, the leaf switches located in top-of-rack, middle-of-row, or end-of-row physical configurations can be connected to the spine switches, using short reach optical modules operating over multimode fiber.

The IEEE 802.3 cm has technical objectives for 400 Gb/s operation over 8 pairs (BASE-16) of multimode fiber and 4 pairs (BASE-8) of multimode fiber, each with installed lengths of up to 100 m. The parallel solutions proposed in the IEEE 802.3cm will look to minimize the implementation costs by leveraging the lower cost VCSEL sources used with multimode fiber when compared to the longer wavelength single-mode optics.

Another benefit of the parallel fiber configuration is its ability to support individual duplex breakouts of the 400 Gig circuit, which improve the flexibility of the multimode fiber installation greatly.

There are exciting developments on the horizon for multimode fiber technology, but education is needed to determine the right solution based on the application environment. Learn more by reading our TECHbrief on and talking to an Anixter technology expert.