Patch cords: structure and selection
The patch cord is the most replaced — and most abused — component in an optical link. Choosing the right connector, polish type and fiber grade avoids reflectance and loss problems that look like equipment faults.
- 1
Match the fiber standard
OS2 (G.652D) for standard single-mode, OM3/OM4 multimode inside buildings, G.657A2 bend-insensitive where cords run through tight ducts. Mixing G.657 patch cords into G.652 links is acceptable; the reverse can raise loss.
- 2
Connector polish
UPC for standard links, APC (green connector) for any RF-over-glass / PON link. Never mate UPC to APC — the air gap causes 25 dB+ return loss.
- 3
Check end-face grade before installing
Inspect with a scope (P-200 / P-2580). IEC 61300-3-35 Grade B for single-mode patch cords is the acceptance bar.
- 4
Bend radius and strain relief
Minimum bend radius 30 mm for G.652, 15 mm for G.657A2. Keep the boot crimp intact — a loose boot lets the fiber twist at the ferrule.
- 5
Insertion loss budget
Typical good cord: ≤0.3 dB per connector. If a link is 1 dB worse than calculated, swap the cords first before blaming the splicer or OTDR.
Field tips from TEKCN engineers
- Dust caps must stay on until the moment of connection — an exposed UPC ferrule collects oil and dust in minutes.
- Clean with one-click pens (FC-01) or lint-free wipes with IPA; never reuse a dry wipe.