A fiber modal adapter for upgrading 850 nm multimode fiber links to 1310 nm single-mode transmission

Abstract We propose a simple and compact adapter using specially designed modal conditioning single-mode fiber for fundamental mode transmission through multimode fiber. The modal conditioning single-mode fiber has a mode field diameter at 1310 nm roughly matching that of the fundamental mode of the 50-μm core multimode fibers. The fiber is designed for integration in a compact adapter due to its low fiber cutoff wavelength. The adapters are attached to both the input and output ends of the multimode fiber to form a link suitable for single-mode transmission. The detailed characteristics of the link such as insertion loss and multi-path interference are measured. Using the adapters, we demonstrate error-free transmission over 1-km multimode fiber using a 100G CWDM4 transceiver, which carries 4 × 25 Gb/s transmission at four wavelengths around 1310 nm. The proposed SMF adapter not only enables newly deployed multimode fiber to be future proof for higher data rate SM transmission, but also offers an upgrade solution for legacy OM2 installations which otherwise cannot support higher data rate and in some cases are very costly to replace.