I have aerial fiber optic cable only. Can I use this cable underground because I have excess aerial cable but I have no underground cable?
In short, is aerial fiber optic cable insulated enough to be used under ground?
You should never do something like you intend. OSP (Outside Plant) cabling is a specialty that many cable installers do not do because there are some serious life/safety implications. For example, grounding and bonding. You need an electrician to make sure that the OSP cable is properly grounded and bonded, and has proper lightning protection. Also, underground cable needs to be gel-filled, loose-tube cable, and armored if it directly buried. It must be buried at least 24", or below the frost line, to the top of the cable or conduit whichever is deeper.
OSP cabling is something that you should really leave to professionals because you can expose yourself to serious civil and possibly criminal problems in the case of some type of disaster, e.g. a fire.