IEC 60794-1-211-2021 pdf Optical fibre cables – Part 1-211: Generic specification – Basic optical cable test procedures – Environmental test methods – Sheath shrinkage, method F11

4.2 Sample A 2 m length of cable shall be cut from the end of the cable and discarded in order to avoid end effects. The test sample lengths shall be cut from the adjoining cable. Five test samples of the length specified in the detail specification shall be cut from the cable. – For test samples of a nominal 1 m length, cut 1 050 mm ± 5 mm. – For test samples of a nominal length of 150 mm, cut 160 mm ± 5 mm. 4.3 Apparatus A horizontal surface where the test samples are placed that permit free movement of the sheath. For example, talc, paper or paper dusted with talc on the surface permits free movement of the sheath. A temperature chamber of appropriate size and a temperature sensing device. The temperature chamber shall be able to accommodate the test samples and maintain the specified temperature within ±3 °C. A length measuring device of sufficient length with a minimum resolution of 1 mm for a sample with a nominal 1 m length, or 0,15 mm for a sample with a nominal 150 mm length. 4.4 Procedure The cable on the supply reel, or alternatively the cable coil, shall be conditioned for 24 h at ambient temperature before cutting the test samples. Two marks separated by the distance of the nominal test length per the detail specification (e.g. 1 000 mm, 150 mm), with a deviation not greater than ±1 mm, shall be applied to each test sample, as shown in Figure 1. Alternatively, the sample ends may be cut to the measurement length, L , using a razor knife. 1 This alternative is best suitable for a short sample length of 150 mm. Two marks longitudinally to the cable axis shall be applied to both ends of each test sample to indicate the measurement points, as shown in Figure 2.
The test samples are placed horizontally on a surface located in the temperature chamber in such a manner as to permit free movement of the sheath. When space allows, the samples should be placed into the chamber in a straight configuration. If the samples need to be coiled, the test samples shall be coiled with a radius of not less than 150 mm still allowing free movement of the sheath. The cable samples shall be temperature cycled in accordance to IEC 60794-1-22, method F1. The parameters specified in the detail specification shall be used. For more information on cable shrinkage characterisation and guidance, see IEC TR 62959.