Object
This test applies to continuously water-blocked optical fiber cables. The purpose is to evaluate the cable’s ability to prevent water migration along a specified length.

Compliance shall be verified using one of the two following methods, as specified in the detail specification:

• Method F5A – tests for water migration between the outer interstices of the optical core and the outer sheath.
• Method F5B – tests for water migration across the entire cross-section of cables designed with water-blocking features.

Method F5B
A cable sample at least 1 m longer than the test length (not exceeding 3 m) shall be prepared. A watertight seal shall be applied to one end of the sample to enable a 1 m water head to be maintained.
Note – For armored cables where the armor is not designed to be water-blocked, the armor may be removed before applying the seal.

Procedure
Unless otherwise specified, the sample shall be supported horizontally, and a 1 m water head shall be applied for 24 hours at a temperature of (20 ± 5) °C.
A water-soluble fluorescent dye or another suitable coloring agent may be used to detect any water seepage. Care should be taken to select a dye that does not react with any cable components.

Requirements
No water shall be detected at the unsealed end of the sample. When a fluorescent dye is used, examination may be carried out under ultraviolet light.
Note – The above procedure represents a basic compliance test. For routine testing, shorter samples and reduced test durations may be used.