---
title: "NCCL ↔ Optical Correlation"
method: GET
path: "/api/nccl/correlation"
tags: ["NCCL"]
---

# NCCL ↔ Optical Correlation

`GET /api/nccl/correlation`

## Request

- Base URL: `https://api.fiber.ac` (the document declares no server; this is the origin it was published from)
- URL: `https://api.fiber.ac/api/nccl/correlation`
- Auth: none declared

Correlate low-bandwidth NCCL events with optical telemetry anomalies on the GPU-node's upstream port. For each low-bw event, fetches ±30s optical samples and flags whether rx_power/temperature/FEC were anomalous. Produces the 'NCCL drop ↔ optical root cause' evidence that closes the loop between GPU performance and the physical layer — Hikari's flagship IR story.

## Query parameters

- `minutes` integer
- `low_bw_threshold` number: GB/s threshold below which event is considered slow (static mode)
- `mode` string: static = fixed 50/5 GB/s; dynamic = per-(node,event_type) EMA - 2σ (Spectrum-X NetInspector style, W13)

## Response `200`

Correlations with per-event optical window and hit rate

- unknown

## Other responses

- `422`: Validation Error

---

[API](https://skmtc.dev/fiber-ac/apis/fiber-api.md) · [All operations](https://skmtc.dev/fiber-ac/apis/fiber-api/llms.txt) · [OpenAPI document](https://skmtc.dev/fiber-ac/apis/fiber-api/revisions/58267250d793?raw)