SEQH CAPITAL RESEARCH - TEAR SHEET
THE RAMAN GAP - HOLLOW-CORE FIBER DOES NOT KILL EDFAs, BUT IT DOES CHANGE WHAT AMPLIFIERS ARE WORTH
WHAT THIS REPORT ARGUES
The report corrects a growing market misconception around hollow-core fiber: Microsoft, Corning, and Heraeus announced their outsourced manufacturing ramp on September 23, 2025, not in July 2026.
More importantly, hollow-core fiber does not make erbium-doped fiber amplifiers obsolete. The amplifier mechanism that genuinely loses its role inside a hollow span is distributed Raman gain, while solid-core EDFA modules can still be spliced into the network at amplification sites.
Core thesis
Hollow-core fiber guides more than 99 percent of optical power through air rather than solid glass, producing lower attenuation, far lower dispersion, and a three-to-four-order-of-magnitude reduction in nonlinearity versus conventional solid-core fiber.
Those advantages make hollow-core fiber important for AI networking, especially where low latency, high launch power, and long-distance optical transport matter.
But the report’s key point is that the transition should not be interpreted as an imminent replacement cycle for all optical amplifiers. It is a multi-year qualification and ecosystem transition, not a near-term revenue reset.
What hollow-core changes
Microsoft’s DNANF hollow-core fiber has demonstrated record attenuation of about 0.091 dB/km at 1550nm, below the commonly cited Rayleigh-scattering floor for standard solid silica fiber.
The same architecture offers materially lower dispersion, a group index closer to air than glass, and roughly 30 to 33 percent lower latency than conventional single-mode fiber.
Lower nonlinearity gives network designers more headroom for higher per-channel launch power, which can increase the value of high-power booster amplifiers over time.
Microsoft has stated that its hollow-core fiber can deliver up to 47 percent faster data transmission, and more than 1,280 kilometers of hollow-core fiber had reportedly been deployed in Azure by mid-2026.
The Raman distinction
An EDFA works by amplifying light inside a discrete section of erbium-doped solid silica fiber. That module can remain intact and can be connected to a hollow-core span through standard optical interfaces.
Distributed Raman amplification is different. It requires the pump and signal to overlap inside the silica transmission fiber itself, which becomes largely impossible when the optical mode travels through an air-filled hollow core.
This makes Raman gain the true structural casualty of hollow-core fiber, not the broader EDFA product category.
The report identifies hybrid Raman-EDFA products as the most directly exposed amplifier line, because part of their value proposition comes from the incremental reach delivered by distributed Raman gain in conventional solid-core spans.
Why the timeline matters
Hollow-core technology is advancing quickly, but it is still early from a standards and qualification perspective. No formal ITU-T recommendation yet exists for hollow-core fiber.
Connector, splice, amplifier-control, gain-flattening, transceiver, and test-equipment vendors all need to qualify against a different loss curve, different dispersion profile, and different field-installation economics.
The report estimates a full hollow-core-specific equipment refresh at three to five-plus years, based on standards timing, Telcordia GR-468 reliability qualification, and comparable optical-component commercialization cycles.
The economics reinforce that timing: hollow-core splices are estimated near $150 each versus roughly $15 for standard single-mode splices, while hollow-core connectors are estimated near $200 versus around $10 for standard connectors.
Lumentum read-through
Lumentum is the more amplifier-levered of the two names, with more than 200,000 Lumentum-designed EDFAs deployed in commercial networks and a broad portfolio spanning Raman amplifiers, EDFAs, hybrid Raman/EDFA systems, high-power EDFAs, L-band amplifiers, and compact amplifier arrays.
Its current growth cycle is primarily tied to pump-laser and multi-rail C+L demand, not hollow-core fiber. Management has guided to a fourfold increase in pump-laser shipments, a tripling of pump revenue over three years, and a fivefold rise in pump output.
Lumentum does sell a product called Hollow-Core Anti-Resonant Fiber, but the report classifies it as a false positive for telecom exposure. It is designed for high-power laser delivery, spectroscopy, sensing, and medical applications, with loss below 50 dB/km, roughly 500 times higher than telecom-grade hollow-core fiber.
The report finds no disclosed Lumentum roadmap, filing language, or earnings-call discussion linking telecom hollow-core fiber to its amplifier business.
Coherent read-through
Coherent has direct exposure to the same multi-rail amplifier refresh through its variable-gain EDFAs, fixed-gain EDFAs, arrayed EDFAs, pump lasers, ROADM line cards, and hybrid Raman-EDFA products.
Its Hybrid Raman-EDFA, which combines Raman and EDFA gain for ultra-long-haul and flex-spectrum systems, is identified as the narrowest direct product exposure if hollow-core deployment reduces demand for distributed Raman contribution.
At the same time, Coherent is positioned for the opportunity side of the transition: higher-power booster amplifiers, C+L systems, dynamic gain equalizers, and multi-rail amplification architectures.
Coherent launched a four-rail, 1RU in-line amplifier platform in March 2026 and expects initial multi-rail revenue in the first half of calendar 2027, with management sizing the multi-rail opportunity at more than $2 billion by 2030.
The report also flags an unconfirmed forward signal from a September 2026 industry session in which Coherent reportedly identified hollow-core and multicore fiber as next-generation technology areas and hinted at possible future announcements.
The refresh cycle actually underway
The report’s main practical conclusion is that the current refresh is multi-rail C+L amplification, driven by higher wavelength counts, channel density, scale-across AI networking, and greater demand for amplifier capacity.
Both Lumentum and Coherent have already launched or sampled products aimed at this cycle, including multi-rail channel monitors, C+L tunable lasers, wavelength-selective switches, dynamic gain equalizers, high-power pump lasers, and multi-rail in-line amplifier cards.
This demand exists regardless of whether a customer deploys solid-core or hollow-core fiber. Hollow-core is an adjacent future technology shift, not the core explanation for today’s amplifier spending.
Bottom line
The cleanest framing is that hollow-core fiber changes the physics of the span, not the relevance of optical amplification itself.
EDFAs remain part of the deployed answer, while distributed Raman gain becomes less useful inside a hollow-core link.
Coherent faces a modest Raman-specific product risk but also has a potential high-power-booster opportunity. Lumentum has stronger existing amplifier and pump-laser scale, but no confirmed telecom hollow-core positioning.
The near-term revenue catalyst is the multi-rail C+L refresh. A true hollow-core-specific component cycle is likely years away, pending standards, qualification, connector economics, deployment scale, and confirmed vendor roadmaps.
What readers get in the full PDF
Upgrade to access the full report, including:
The corrected Microsoft, Corning, and Heraeus announcement timeline, including what was actually disclosed and what remains undisclosed.
A detailed physics comparison of hollow-core versus solid-core fiber, covering attenuation, latency, dispersion, nonlinearity, splice economics, and connector costs.
The full analysis of why Raman gain disappears while EDFAs remain deployable, including the mechanics of hybrid-span architectures.
Product-level exposure maps for Lumentum and Coherent, including Raman/EDFA hybrids, high-power booster EDFAs, pump lasers, specialty fiber, and multi-rail systems.
A complete qualification and standards calendar, including ITU-T status, GR-468 timing, and the catalysts that would signal a real hollow-core component refresh.
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