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