External Alarm Cable

Hi all, just ordered a GJD curtain PIR detector for my driveway post and I need to run a cable to it. I only need about 15m of external cable but most places only sell it in 100m reels at about £30+ so much of it would be wasted. I do have some external CAT6 cable so I'm wondering if this would do the job? Or am I better off buying specific alarm cable ? Also, I am running around the perimeter and will bury the cable so what is the best ducting to put it in? It won't be in an area that gets dug up or anything so don't think it needs to be particularly deep and I'd struggle to get it deep anyhow. Does the whole length need to be in ducting such as when I'm running it down the wall from my house and then up the drive post ?

Any help much appreciated

Andy

Or what about this and not use any ducting............

https://connectec.uk/security/intru...ial-6-core-alarm-cable-black?variant_id=11293

20mm black conduit couple of end boxes a couple of elbows and some connectors ...