"Water blocking compound. A water blocking agent is applied to the cable core (stranded buffer tubes) to prevent water migration along the calbe to prevent potential crushing forces due to freezing water. The water blocking compound can be either a water swellable powder, tape, or yarn, or if could be a water blocking gel."
http://books.google.com/books?id=D0PBG53PQlUC&pg=PT330

": Water-blocking options for cable coreX=No water-blocking; J= Water-blocking gel in tubes; JD=Water-blocking gelin tubes+ dry water-blocking in cable core interstices; JJ= Water-blocking gel intubes and cable core intersticesJ: Water-blocking options or cables with more than one jacketX=No water-blocking; J=Water-blocking gel between jackets; D=Dry water-blocking between cable jackets;K: Strength member optionsA=Aramid yarn; AG=Aramid yarn and fiber glass yarn; G=Fiber glass yarn"
http://www.caledonian-cables.co.uk/Zipped/Fiber/39-44.pdf

This Indoor/Outdoor cable is designed for general outdoor applications, yet it can be used indoors without the 50 feet restrictions imposed upon loose tube cables, or non-UL approved cable. It is composed of 6 900um tight buffered fibers, water blocking aramid fiber strength members and a black color OFNP Plenum rated PVC jacket.
http://www.fiberoptics4sale.com/page/FOFS/CTGY/Fiber_Optic_I...