Cross connects: a practical guide
What a cross connect is, how a circuit runs from cage to meet-me room, fibre and connector types, and how to trace and test one.
A cross connect is a physical cable that joins two customers, or a customer and a carrier, inside a colocation facility. It is the product colocation actually sells: not just space and power, but the ability to reach everyone else in the building without going out to the public internet.
How a circuit runs
The path is usually cage → patch panel → overhead or underfloor tray → meet-me room (MMR) → patch panel → carrier or customer equipment. Each end terminates on a documented panel position, and that pair of positions is the circuit's identity for its entire life.
Media and connectors
- Single mode (OS2, yellow jacket): long distance, used for most in-building and carrier handoffs.
- Multimode (OM3 aqua, OM4 aqua or violet, OM5 lime): short distance, cheaper optics, common inside a cage.
- LC: the small duplex connector you will handle most often.
- SC: larger, square, still common on older carrier panels.
- MPO/MTP: multi-fibre ribbon connector used for 40G, 100G and higher breakouts.
- Copper Cat6/6A: still used for lower speed handoffs and out-of-band management.
Installing one
- 1Read the order: media type, connector type, both panel positions, and the demarcation point.
- 2Verify both ends physically exist and are free before pulling anything.
- 3Route the cable along the designated tray, respecting bend radius and keeping fibre off sharp edges.
- 4Clean and inspect both endfaces, then seat the connectors with an audible click.
- 5Test: light level or loss measurement, and confirm the far end sees the link.
- 6Label both ends with the circuit identifier and update the records.
Tracing an existing circuit
When documentation and reality disagree, trust neither until you have proof. A visual fault locator pushes visible red light down the fibre so you can confirm the far end. An optical power meter tells you whether light is arriving and at what level. For copper, a toner and probe does the same job. Always confirm at both ends before you unplug anything — an unlabelled cable in a live cage is somebody's production traffic until proven otherwise.