Driven by AI and big data applications like ChatGPT, the global computational scale is experiencing rapid growth. This growth places higher demands on data center infrastructure such as GPUs, servers, and switches, particularly in terms of data transmission rates and latency requirements. In the context of multi-threaded parallel computing, any network congestion or packet loss in a switching link can lead to I/O delays. Therefore, there is a need for high-bandwidth, high-speed switches/optical modules, and communication links that can match this demand.
As a significant part of the industry chain, the support capacity of multimode optical fiber for single-channel 100G transmission distance is also a focal point of industry attention. We've observed that Cisco, in collaboration with partner Corning, recently published a joint technical white paper on the Cisco official website. This paper introduces a new type of high-speed multimode optical fiber optimized for single-channel 100G VCSEL transmission – the HDR OM3 fiber and HDR OM4 fiber. According to the white paper, these two new types of multimode optical fiber, compared to traditional standard OM3 and OM4 fibers, optimize the effective modal bandwidth of the fiber. They support single-channel 100G VCSEL optical modules at transmission distances of 80 meters and 100 meters. They also support Terabit BiDi MSA (e.g., 800GSR4.2, 1.6TSR8.2) dual-wavelength transceivers, achieving longer transmission distances than standard OM3/OM4 fibers at wavelengths of 850nm and 910nm.
HDR OM3 fiber defines a minimum EMB value of 2890 MHz·km at 850nm, which falls within the range of OM3 fiber EMB (2000 MHz·km to 4700 MHz·km), with a higher proportion of OM3 fibers meeting the requirements of HDR OM3. This aids in building a scalable, cost-effective ecosystem for VCSEL lasers/multimode optical fibers. HDR OM3 fiber supports a transmission distance of 80 meters at a single-channel 100G rate, meeting the requirements of most multimode fiber scenarios. Compared to using OM4 fibers, it can reduce the overall cost of multimode connection solutions.
The article also points out that HDR OM3/OM4 fibers define bandwidth indicators for 910nm. They support the use of dual-wavelength transceivers at 850nm and 910nm in the Terabit BiDi MSA, achieving transmission distances of 80 meters and 100 meters, respectively. This represents an improvement of 77% and 43% over standard OM3/OM4 fibers. Additionally, the transmission distance of HDR OM4 reaches the level of OM5 (100 meters) in supporting Terabit BiDi transceivers.