Fundamental mode transmission around 1310-nm over OM1 and OM2 multimode fibers enabled by a universal fiber modal adapter

Recently there has been an interest in upgrading legacy multimode fibers such as 50 μm OM2 fiber to higher data rates through single mode transmission. A fiber modal adapter hosting a modal conditioning single-mode fiber (MCSMF) has been demonstrated as one robust solution to convert OM2 links into single mode transmission links for higher data rate transmission. Legacy multimode fibers also include OM1 fiber which has higher index contrast between the core and cladding and a larger core of 62.5 μm diameter. In this paper, we conduct a study to understand the MCSMF mode field diameter and connector offset tolerance requirements for OM1 fiber, which affect the transmission performance of single mode transmission. We find that despite very different refractive index profiles between OM1 and OM2 fibers, the fiber modal adapter concept is still applicable to OM1 and only one modal conditioning single-mode fiber design is needed to accommodate the needs for both fiber types. The detailed tolerances to the mode field diameter mismatch and the connector offset are numerically studied. The transfer functions for 1000-m of OM1 and OM2 with the adapters are measured, which show very high modal bandwidths at tens of GHz in contrast to very low modal bandwidths without the adapters. Transmission at 25 Gb/s using a 25G LR transceiver, 100 Gb/s using a 100G CWDM transceiver, and 400 Gb/s using a 400G LR transceiver are demonstrated with error free performance and open eye diagrams over 1000-m of OM1 and OM2. We find that the approach of using MCSMF can support fundamental mode transmission up to 100 Gb/s over this distance without obvious limitations.