This is a discussion of indoor-rated communications cable in wet conditions. The comments here apply to both copper communications cables, and to fiber optic cables.
Indoor-rated communications cable is constructed to operate in dry conditions. Where wet conditions exist (or may plausibly be expected to exist at a future date) industry codes and standards require the installation of outside plant (OSP) or indoor/outdoor rated cables. When indoor-rated cable becomes wet, the cable should be considered to be permanently damaged, and any such cable should be removed from the site and replaced. Wet cable cannot be dried out. Water permeates the jacket material and permanently affects the data transmission characteristics of the cable.
Water damage to fiber optic cables results in high attenuation, and degradation of the data signal. In copper cables, the initial indication of water damage is also high attenuation, but the cable quickly degrades further, resulting in eventual Near-end Cross-talk (NEXT) and Return Loss (RL) failures, rendering the cable completely useless for data communications.
This discussion applies to copper cables with any of the following jacket markings: CMX, CMG, CM, CMR, CMP, FT1, FT4, or FT6, and to fiber optic cables with any of the following jacket markings: OFC, OFCG, OFN, OFNG, OFCR, OFNR, OFCP, OFNP, FT4, or FT6.