Zones in IEC 61300‐3‐35 are defined as shown on this picture.

enter image description here

However the optical signal is transmitted by the Zone A - Core.

Light is transmitted and retained in the “CORE” of the optical fiber by total internal reflection.

I do not understand, why there is any limit imposed on defects in Zone D (Contact zone) at all - can it by any means have any real impact on the signal transmission?

Like on this picture of a very dirty old & scratched connector, but no defects within zones A+B and still working.

Really bad connector

The limit is defined as Defects - none > 10μm. Or may be that no defects in Zone A+B means that the picture is not taken properly (there seems to be some noise in background)

1 Answer 1


Not all defects are negative. Any protruding defect, or loose contaminant particle, can prevent contact (holding the connector faces apart), scratch the mating connector, or in the case of a loose particle (such as one created by scratching the mating connector) scratch the core.

  • I have found out, that 0 defects in zone A are just errors of the measurement procedure, so all the zones are probably equally scratched, but it is difficult to evaluate such a damaged connector as the one on the picture. Commented Nov 16, 2016 at 7:53

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