The BOLT-NL uses a "looped" method of measuring fiber length. This is accomplished by looping back two fibers at one end of the fiber run with a patch cord. The round trip time that the light takes to travel through the fibers is converted to length in kilometers, then divided by two to show the length of the fiber cable. There is no need to measure the length of all the fibers; the length measurement can be applied to all fibers in the cable. This method of length testing provides accurate measurements, and saves time and money.
Optical length testers save time by eliminating the need to measure fiber by the cable jacket. Fiber links may also go through multiple cross-connects or have splices in the middle, thereby making jacket markings invalid. Optical measurement of fiber produces accurate results without the need for jacket markings.
Optical measurement also saves time by eliminating the need to estimate the length of the fiber run with a measuring wheel. This method is especially troublesome and inaccurate in networks that traverse walls, are in a star topology, or contain riser cables.
The BOLT-NL measures fiber links of up to 25 kilometers, and is accurate to within ±2.5 meters. Pulsing mode allows for fiber location with fiber identifiers.