Operating Fiber Loop Converters Over Multimode Fiber

Fiber Loop Converters are sometimes required to operate over multimode fiber because an existing span of installed multimode fiber may already be in place between two points requiring FLC transmission. The FLCs were designed for use over singlemode fiber, and if there is a choice, singlemode fiber should be installed. However, FLC operation over multimode fiber is possible and, in fact, is a functioning application with several customers. LAN applications over short distances have been successful. The following aspects of this application require attention | Application Note 1206 E Operating Fiber Loop Converters Over Multimode Fiber Fiber Loop Converters are sometimes required to operate over multimode fiber because an existing span of installed multimode fiber may already be in place between two points requiring FLC transmission. The FLCs were designed for use over singlemode fiber and if there is a choice singlemode fiber should be installed. However FLC operation over multimode fiber is possible and in fact is a functioning application with several customers. LAN applications over short distances have been successful. The following aspects of this application require attention. Launch Conditions A 10 meter 33 singlemode jumper with a physical finish on the connector endfaces should be installed in the FLC transmitter. This singlemode jumper can then be connected to the multimode fiber in the span. To prevent higher order modes from being launched directly into the multimode fiber a minimum of 10 meters 33 of singlemode fiber is required out of the transmitter. The multimode fiber can terminate directly into the FLC s receiver at the other end of the span. Connections in the Span Ideally the only connection in the span will be the junction from singlemode to multimode. If fiber joining is required anywhere else in the span fusion splicing is recommended. Because the connectors in a multimode span are not required to be in physical contact at the fiber endfaces Fresnel reflections and alignment mismatches can degrade performance to an unacceptable level. If connectors are in the span they should be of singlemode quality with physically contacting radius-polished fiber endfaces. Multimode SMA and biconic fiber connectors are unacceptable. D4 SC FC and ST connectors can be used if the endface polish and the concentricity tolerances are singlemode quality. The number of connectors should be kept to the absolute minimum. Optical Budget Multimode fiber has higher loss per distance properties than singlemode fiber. Tradi-