Inspect, clean and reinspect every fiber end face under IEC 61300-3-35:2022 before mating

Contaminated fiber end faces cause loss and reflections and can dirty equipment ports. The 2022 edition of IEC 61300-3-35 simplifies the workflow: clear the contact area, grade only the core and cladding, and let passing loss tests decide.

Source facts

Fluke Networks advises inspecting, cleaning and reinspecting fiber end faces before mating connectors, including the test reference cord connected to a tester. Contaminated end faces can cause signal loss and reflections and can transfer dirt to clean ports on network equipment.

In the third edition, IEC 61300-3-35:2022, Zone C (adhesive) and Zone D (contact) are removed from the pass/fail criteria. The standard recommends inspecting the entire contact area first and removing loose particles that could migrate to the core and cladding; particles that survive several cleaning attempts are treated as embedded and acceptable, and inspection then proceeds to Zones A and B, which keep pass/fail limits. MPO connectors follow the same approach across the whole ferrule.

The most notable change is that a connector cleaned of loose debris but failing inspection may still be used if it passes optical performance tests for insertion loss and return loss.

Applicability

Use this for single-fiber and multi-fiber MPO connectors on any fiber backbone, data center or camera network. Fluke notes that its inspection tools now grade against the 2022 edition, and that a failed inspection still appears on test results to aid later troubleshooting.

DSE recommendation

DSE recommends making inspect-clean-reinspect a required step, with saved images or tester results, every time a fiber connector is mated. Specify IEC 61300-3-35:2022 grading in installation contracts, inspect and clean test reference cords before every test session, clean MPO ferrules as a whole before grading individual fibers, and treat a failed inspection with passing loss results as acceptable only when the insertion-loss and return-loss evidence is recorded.

Verification

For a sample of new or changed links, check that the closeout package contains end-face results for both ends, the grading edition used, and Tier 1 loss results. Any connector accepted on optical performance after a failed inspection should show both records together.

Official reference

Fluke Networks — Easier Fiber End Face Inspections: Key Changes to IEC 61300-3-35. Reviewed October 18, 2026.