|With a 90 metre cable (keep in mind the maximum is 100 m) I'd recommend pulling a replacement if possible as compared to using a coupler. At 90 m, you're already experiencing some attenuation. Personally, I try to avoid cables in excess of 85 m because I've found when you start getting to 85 m in length, you can start experiencing problems due to attenuation.|
While a coupler shouldn't cause more, it certainly won't help the situation any. Just FYI, there's nothing wrong with using a coupler. They're basically just a very short piece of straight through cable with a female RJ45 port at each end. I've made them out of a short piece of cable and two keystone jacks when I didn't have a store-bought one and needed to extend and existing cable.
If you must, then give it a try but don't be too surprised if you experience some connectivity issues.
Definintely do not try making two crossovers out of the two pieces of cable.
It matters not how straight the gate,
How charged with punishments the scroll,
I am the master of my fate;
I am the captain of my soul.