OSP cable is effectively "CAT Zero". True, there are some manufacturers that make a CAT3 and CAT5 rated OSP cable, by adding the increased twist tightness, you are actually lengthening the copper pair.
People seem to be under the misconception that CAT5 or above is better. Perhaps in some cases, like typical indoor LAN wiring for data speed, but not in voice applications. I'm shooting from the hip here, but a thousand feet of standard OSP cable nets about 1,100 feet of copper conductor length. A thousand feet of CAT5 nets something closer to 1,500 feet of copper. So, you see by using a higher category rating, you are actually hindering the problem with distance, not helping it.
If you want to address this distance limitation professionally, you should consider sticking with standard OSP cable (PE39 or PE89 for example) and just use 22 gauge instead of 24 gauge.
