Coherent Ultra Matched (M+) Large Mode Area (LMA) active double clad fibers are ideal for high power fiber lasers and amplifiers used in defense, industrial, and medical applications. These fibers feature a 20 micron diameter core and 400 micron diameter clad size with a low NA (0.065) core. These M+ fibers represent the next generation of matched fibers. They are matched with ultra-high precision to their passive 20/400 LMA M+ counterparts to ensure excellent splice compatibility and low loss. As with all Coherent standard LMA fibers, these fibers are proof tested to 100 kpsi, an industry requirement for long term reliability. The M+ fibers are specified to the tightest specifications including the MFD, and use NuCOATFA coating technology ensuring excellent preservation of beam quality and extending operating life at the high power levels demanded by today’s industrial fiber laser applications. These ultra matched fibers are available in non-PM (LMA) and PM (PLMA) versions.