Novel mode converter based on hollow optical fiber for Gigabit LAN communication

A novel mode converter based on a hollow optical fiber is proposed to reduce the differential modal delay penalty in optical transmission over multimode fibers (MMFs). The device adiabatically converts a fundamental mode in a single-mode fiber to a ring-shaped mode in order to excite selectively a set of higher order modes with a similar group velocity in MMF, maintaining center-launching configuration. The mode converter is composed of serially concatenated concentric segments of a single-mode, hollow, and multimode optical fiber. For 2.5-Gb/s transmission over 500-m-long MMF using a laser diode transmitter, the proposed mode converter shows improvement in bit-error-rate performance at both wavelengths of 1.31 and 1.55 μm.