Reflectometer, this is an amazing piece of equipment. I do I&M and it's a fantastic tool. Not sure which port to use in fdt, use vfl, put on comfortable shoes and go to the other end. I do not think so. Not only can I choose the longest fiber, but also the fiber with the lowest loss. recipe for success. I had a problem with my original device. YEDEMC friends solved my problem promptly with free direct return and brand new device. Completely satisfied. Thank you!