No, outside plant is not "category" rated at all. It is basically the same as CAT nothing. It was never designed to meet the current criteria of inside cable manufacturing standards. Hell, even the sheer distances that OSP cables run goes against all TIA/EIA standards for categorized cables.

There are some category-rated outside plant cables available now for smaller jobs, but they won't ever become widespread in use.

Outside plant cables rely upon extremely compact construction to conserve space in ducts, manholes and vaults. Tighter twists=larger outside cable diameter. OSP cable outside dimensions are tightly followed amongst manufacturers. This standard is to ensure duct fill and splicing equipment standardization. The reason your 25 pair cables were different diameters had to do with the CAT3 cable having more twists per-pair, per inch, thus a larger cable core.

These cables are completely different animals. Sure, they carry communications circuits and may use the same pair coloring code, but that's where the similarities end. Actually, there haven't been many changes in the design and construction of outside plant cables since the late 1960's!

There aren't really any voice applications where category 1 can't be used except maybe for ISDN stations or very long digital station cable runs.

As for the category question, the first I heard of it was from our rep at Anixter in 1986. I called to order some cable and he advised me then that I would soon have a choice of category 1,2,3 or 4. There was no talk of 5 at the time, but once it arrived on the scene, category 4 pretty much fell by the wayside.

Ed Vaughn, MBSWWYPBX