VR (Very Short Range): Transmission distance usually 0~100 meters, using multimode fiber for short data center connections. It converts electrical signals into optical signals and vice versa, enabling data transmission over optical fibers. The demand for 400G optics has been fueled by. Here are where different 400G module types tend to shine: Intra‑Rack & Top‑of‑Rack Interconnects: SR4 / SR8 / VR4 options are great for connecting servers, switches within same rack or adjacent racks due to low cost, low latency, high density. SR (Short Range): Up to 300 meters, using multimode fiber for. Quick summary: SR4 modules are short-reach, multimode solutions that use MPO/MTP ribbon connections and are optimized for cost-effective, dense data-center fabrics over OM3/OM4 MMF; DR4 modules are data-center reach, single-mode solutions (or single-mode MPO variants) that extend reach. As hyperscale data centers, AI clusters, cloud fabrics, and carrier networks migrate toward 400G-class architectures, the optical ecosystem supporting these high-capacity links has rapidly expanded. A wide range of optical standards—VR4, SR4, SR4. 2, SR8, DR4, FR4, LR4, LR8, ER4, ZR4—now coexist.
