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NEC SDM Repeater (Petal 96-amp FIFO)

The Petal single-body 96-amp repeater is the subsea optical amplifier NEC engineered for Meta's Petal cable. It is the piece that reconciles Petal's multi-core-fiber capacity with the efficiency and reliability of single-core amplification — and the reason Petal can double capacity without a proportional power increase. (Source: sources/2026-09-21-meta-inside-petal-building-the-worlds-first-petabit-class-transoceanic-subsea-cable)

Why repeaters matter

A ~7,000 km transatlantic cable needs "about a hundred repeaters to amplify the digital signals along the length of the cable." Repeaters are powered from shore over the cable itself, so the amplifier design is fundamentally power-constrained (see concepts/submarine-cable) — more amplification means more power, and the system must stay inside existing power-feeding limits.

Fan-In/Fan-Out (FIFO)

Single-core fiber amplification is the most efficient and reliable option, but Petal's fiber is 2-core (systems/sumitomo-2c-zplus-ull-fiber). The repeater resolves this with a Fan-In/Fan-Out (FIFO) interface:

  1. Fan-Out — split each incoming 2-core fiber into two single-core fibers.
  2. Amplify — boost each single-core fiber using an SDM pump-sharing architecture (amplifier pump energy shared across the many single-core paths).
  3. Fan-In — recombine the single-core fibers back into 2-core fiber for onward transmission.

The result: Petal "retains the highest efficiency and reliability of single-core amplification" while carrying 2-core capacity. The 96 amps in one single-body repeater correspond to the 24 fiber pairs × 2 cores = 48-fiber-pair-equivalent paths amplified per direction.

Power: the load-bearing constraint

FIFO, "combined with highly efficient amplification and high-quality, low-loss fiber," lets Petal double capacity without a proportional increase to required power. Petal "will remain within existing power feeding equipment limits, rated up to 18 kV, which avoids triggering a requalification of the subsea ecosystem necessary at higher equipment voltages." Capacity-per-watt — not raw capacity — is the design's central trade-off.

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