We propose a novel waveguide design of polarization-maintaining few mode fiber(PM-FMF) supporting ≥10non-degenerate modes, utilizing a central circular air hole and a circumjacent elliptical-ring core. The structure endows a new degree of freedom to adjust the birefringence of all the guided modes, including the fundamental polarization mode. Numerical simulations demonstrate that, by optimizing the air hole and elliptical-ring core,a PM-FMF supporting 10 distinctive polarization modes has been achieved, and the effective index difference Δn_(eff) between the adjacent guided modes could be kept larger than 1.32 × 10^(-4) over the whole C +L band. The proposed fiber structure can flexibly tailored to support an even larger number of modes in PM-FMF(14-mode PM-FMF has been demonstrated as an example), which can be readily applicable to a scalable mode division multiplexing system.
We experimentally demonstrate a real-time quasi-full-duplex 400G/300 G optical interconnection over 20 km multicore fibers(MCFs), using 10G-class transponders operated in the C-band. Optical delay interferometer(ODI)-based optical frequency equalization is applied to mitigate chirp and dispersion induced impairments,so that the tolerance to inter-symbol interference(ISI) can be enhanced, thus enabling 4 × 25 Gb∕s on-off keying(OOK) transmission per core over severely limited bandwidth channels. Real-time bit error ratio(BER) performances of the bidirectional 400 Gb/s transmission are measured without using extra digital signal processing(DSP) or electrical equalization, which ensures low complexity and less power consumption.
