Future revisions or new standards will likely increase this value. Each of these methods has its own advantages and disadvantages, as summarized in Table 1 . Measurement Technique Advantages Disadvantages Optical Continuous-Wave Reflectometry Tests can use inexpensive equipment and setup is easy. Calibration of equipment is easy. Power meters respond to all reflections and the characteristics of directional-couplers depend of the wavelength and mode of light transmissions.
Tests require a mandrel wrap, or similar termination, at the far end of a cable.
An OTDR accurately measures losses and lengths for long runs of fiber-optic cable. An OTDR cannot make measurements on short cable runs. An OTDR can take up to 30 s to make a series of measurements and calculate a result. The ORD technique provides better measurement accuracy compared to the OTDR method, specifically for shorter cables. Mandrel-free operation can be limited to a few meters.