This is a new single mode patch cable, straight out of the bag. The first thing I always do before I use a new cable is use my Fluke Networks fiber inspection camera to check out the end face of the fiber. A dust cap does not mean that the fiber is clean. Dust caps do a great job of making sure that any dust on the end face stays there. If you look carefully, you will notice that you can't see the fiber. That is because it is only 9 microns in diameter and is fully covered by the dust! Not only does this attenuate the signal, it can damage the connector when mated with another fiber. If you are connecting two fibers together, you need to be inspecting them first. If they are dirty, you need to clean them and re-inspect. Don't use the s-word (should) and say they should be clean because they are new.