{"id":13248,"date":"2026-09-03T17:31:47","date_gmt":"2026-09-03T09:31:47","guid":{"rendered":"https:\/\/ascentoptics.com\/blog\/?p=13248"},"modified":"2026-09-03T17:31:47","modified_gmt":"2026-09-03T09:31:47","slug":"800g-sr8-transceiver","status":"publish","type":"post","link":"https:\/\/ascentoptics.com\/blog\/800g-sr8-transceiver\/","title":{"rendered":"800G SR8 Transceiver: Specs, Breakout & SR8 vs DR8 Guide"},"content":{"rendered":"

The 800G SR8 transceiver is a short-reach multimode optical module designed for high-bandwidth data center connectivity. As one of the short-reach options in the broader family of 800G optical transceivers<\/a>, SR8 uses approximately 850 nm VCSEL technology and PAM4 modulation, making it well suited for short-distance connections over multimode fiber.<\/p>\n

The module supports flexible breakout applications, allowing an 800G port to be split into two 400G or four 200G connections. Unlike the 800G DR8, which is designed for 500-meter single-mode transmission, the SR8 is specifically intended for short-reach interconnect scenarios, such as within a rack.<\/p>\n

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What Is an 800G SR8 Transceiver?<\/strong><\/h2>\n

An 800G SR8 transceiver<\/a> is a hot-pluggable optical module that transmits and receives data at 800 gigabits per second over multimode fiber. It uses eight parallel lanes of 100G PAM4 signaling, each driven by an 850 nm VCSEL laser, and connects through an MPO-16 or dual MPO-12 connector.<\/p>\n

That’s the definition in a single breath. The “SR” stands for short reach, and the “8” tells you the module uses eight optical lanes in parallel. That parallel structure is what lets SR8 hit 800G using low-cost multimode optics instead of the more expensive single-mode lasers that DR8 and FR8 require.<\/p>\n

Because SR8 runs on multimode fiber, it is the most economical 800G variant to build and operate. The tradeoff is distance. Multimode fiber supports shorter runs than single-mode, so SR8 is designed for the first 100 meters of the fabric rather than the spine.<\/p>\n

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\"800G<\/p>\n

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800GBASE-SR8 Standards and Architecture<\/strong><\/h3>\n

800GBASE-SR8 is an IEEE-defined Ethernet optical interface for 800G short-reach multimode connectivity. The electrical host interface and module management requirements are defined through the applicable IEEE specifications, MSA requirements, and CMIS implementation.<\/p>\n

Standards compliance improves interoperability, but successful deployment still depends on the switch platform, module coding, firmware, cage, and host-side compatibility.<\/p>\n

Under the hood, eight transmit lanes and eight receive lanes run in parallel. The 800G SR8 transceiver uses eight 100G-class PAM4 optical lanes operating around 850 nm. Each optical lane carries a 100G-class Ethernet signal, providing an aggregate 800G interface over multimode fiber. The optical engine pairs a VCSEL transmitter with a PIN receiver on each lane, all operating at 850 nm.<\/p>\n

Forward error correction (FEC) is an important part of high-speed Ethernet link design and is handled within the applicable host and Ethernet architecture. The exact FEC implementation depends on the Ethernet standard and system design rather than being a user-configurable feature of the optical module itself.<\/p>\n

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\"How<\/p>\n

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QSFP-DD vs OSFP Form Factors<\/strong><\/h3>\n

800G SR8 modules are available in both QSFP-DD<\/b><\/strong>\u00a0and OSFP<\/b><\/strong>\u00a0form factors, depending on the switch platform.<\/p>\n

QSFP-DD<\/u><\/a>\u00a0is the density play. It keeps the same width as earlier QSFP generations, so it packs more ports per line card and preserves backward compatibility. For SR8, whose ~14 W power draw stays well within QSFP-DD thermal limits, it is often the natural choice.<\/p>\n

QSFP-DD provides a compact form factor and high port density. Its mechanical ecosystem is compatible with earlier QSFP-family modules when supported by the host platform, making it attractive for networks that prioritize port density and platform flexibility.<\/p>\n

OSFP\u2002<\/u><\/a>is larger and purpose-built for higher power. It carries an integrated heat sink and handles 20 W and above comfortably. It is widely used in high-performance 800G platforms where higher module power and thermal dissipation need to be accommodated.\u00a0You will see OSFP SR8 in high-power or mixed-vendor environments where the platform already standardizes on OSFP cages.<\/p>\n

Neither form factor should be selected based on module size alone. The switch cage, supported module power, airflow, firmware, and validated transceiver list should all be checked before deployment.<\/p>\n

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800G SR8 Specifications at a Glance<\/strong><\/h2>\n

Here is the specification sheet network teams most often ask for.<\/p>\n

 <\/p>\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n
Parameter<\/b><\/strong><\/td>\n800G SR8 Specification<\/b><\/strong><\/td>\n<\/tr>\n
Data rate<\/td>\n800 Gbps aggregate (8 \u00d7 100G PAM4)<\/td>\n<\/tr>\n
Standard<\/td>\n800GBASE-SR8 (IEEE 802.3df)<\/td>\n<\/tr>\n
Wavelength<\/td>\n850 nm<\/td>\n<\/tr>\n
Optical source\/receiver<\/td>\nVCSEL transmitter, PIN receiver<\/td>\n<\/tr>\n
Fiber type<\/td>\nMultimode (OM3 \/ OM4 \/ OM5)<\/td>\n<\/tr>\n
Reach<\/td>\nup to 70 m on OM3, 100 m on OM4<\/td>\n<\/tr>\n
Connector<\/td>\nMPO-16 APC or dual MPO-12 APC<\/td>\n<\/tr>\n
Form factors<\/td>\nQSFP-DD and OSFP<\/td>\n<\/tr>\n
Power consumption<\/td>\n~12\u201314 W (DSP-based); ~4 W (LPO variant)<\/td>\n<\/tr>\n
Electrical interface<\/td>\n8 \u00d7 100GAUI-8 (IEEE 802.3ck)<\/td>\n<\/tr>\n
Management<\/td>\nCMIS digital diagnostics<\/td>\n<\/tr>\n
Operating temperature<\/td>\n0\u00b0C to 70\u00b0C (commercial)<\/td>\n<\/tr>\n<\/tbody>\n<\/table>\n

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Two numbers deserve a second look. First, reach: 100 m on OM4 is the headline, but if your plant still uses OM3, plan for roughly 60 m. Second, power: the standard DSP-based module runs 12 to 14 W, while the emerging\u00a0LPO<\/strong>\u00a0(linear pluggable optics) variant cuts that to around 4 W by removing the module-side DSP.<\/p>\n

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800G SR8 vs DR8 vs FR8: How to Choose<\/strong><\/h2>\n

This is the comparison most buyers actually need. All three are 800G-class parallel-optics solutions, but their optical architecture and implementation can vary. They differ in reach, fiber type, cost, and power.<\/p>\n

 <\/p>\n\n\n\n\n\n\n\n\n\n
Feature<\/b><\/strong><\/td>\n800G SR8<\/b><\/strong><\/td>\n800G DR8<\/b><\/strong><\/td>\n800G FR-class<\/b><\/strong><\/td>\n<\/tr>\n
Typical Reach<\/td>\nUp to 100 m<\/td>\nUp to 500 m<\/td>\nUp to 2 km<\/td>\n<\/tr>\n
Fiber<\/td>\nMMF<\/td>\nSMF<\/td>\nSMF<\/td>\n<\/tr>\n
Wavelength<\/td>\n~850 nm<\/td>\n~1310 nm<\/td>\n~1310 nm \/ CWDM<\/td>\n<\/tr>\n
Optical Interface<\/td>\nMPO-16 \/ dual MPO-12*<\/td>\nMPO-16 \/ dual MPO-12*<\/td>\nDepends on implementation<\/td>\n<\/tr>\n
Relative Cost<\/td>\nLow<\/td>\nMedium<\/td>\nHigher<\/td>\n<\/tr>\n
Typical Application<\/td>\nIn-rack \/ adjacent rack<\/td>\nIntra-data-center<\/td>\nLonger data center links<\/td>\n<\/tr>\n<\/tbody>\n<\/table>\n

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SR8<\/strong>\u00a0is the short-reach option. It uses multimode fiber, which keeps both the module and the cabling inexpensive, but caps out at 100 m. It’s the right call for top-of-rack, in-rack, and adjacent-rack links.<\/p>\n

DR8<\/strong><\/a>\u00a0is the AI fabric workhorse. It reaches 500 m over single-mode fiber using parallel optics and an MPO-16 connector, which covers nearly every intra-pod link in a data hall. If your runs exceed 100 m, DR8 is where you land.<\/p>\n

FR8<\/strong><\/a>\u00a0(often sold as 2\u00d7FR4) extends to 2 km using CWDM over single-mode fiber with a duplex LC connector. It’s the choice for campus and multi-building links, and it costs more per port for reach most in-rack designs don’t need.<\/p>\n

The selection rule is simple: match reach to your actual link lengths. SR8 is generally the most cost-effective option for short multimode links. DR8 and longer-reach solutions typically cost more because they use single-mode optics and support greater transmission distances. For short in-rack links, deploying a longer-reach module may therefore add cost without providing a practical benefit.<\/p>\n

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\"800G<\/p>\n

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800G SR8 Breakout and Migration Paths<\/strong><\/h2>\n

One of the most useful things about the 800G SR8 transceiver is its flexibility. Because it is eight independent 100G lanes, a single module can break out into several slower links.<\/p>\n