IEC 61753-111-09:2021 contains the minimum tests, test severities and measurement requirements which a sealed fibre optic closure need to meet in order to be categorised as meeting the IEC standard for category S - Subterannean, as defined in Table A.15 of IEC 61753‑1:2018. This first edition cancels and replaces IEC 61753-111-9 published in 2009. This edition constitutes a technical revision. This edition includes the following significant technical changes with respect to IEC 61753‑111‑9:

1. terms and definitions updated according to IEC 61753-1:2018 and IEC 61756-1:2019;
2. detailed test severities added for UV light and fungus resistance tests of materials;
3. test severities updated according to IEC 61753-1:2018;
4. laboratory test conditions harmonized with IEC 61300-1 to +23 °C ± 5 °C, unless otherwise specified;
5. addition of B-657 fibre types with minimum bending radius of stored fibres according to IEC 61756-1:2019;
6. vibration sealing test changed to 10 Hz, 3 mm amplitude and 1 000 000 cycles;
7. reduced loads added in cable retention test for small diameter cables and tubes;
8. reduced loads for cable axial compression test for small diameter cables and tubes;
9. duration of the cycles in torsion and bending test added;
10. free fall test removed (is covered now by the optical shock test);
11. assembly and disassembly test duration reduced to 5 cycles
12. resistance to solvents and contaminating fluids: changed duration of immersion in diesel to 1 h and 24 h drying time and removed immersion in kerosene;
13. duration of the change of temperature reduced to 12 cycles.