Panda type elliptical core few-mode fiber

Abstract

Mode division multiplexing together with multiple-input multiple-output digital signal processing (MIMO-DSP) has the potential for fulfilling future ever-increasing transmission capacity demand. However, for the mitigation of severe mode coupling, the cost and computation complexity of MIMO-DSP become prohibitive with the growing numbers of guided modes arising in the traditional circular core few-mode fiber. We design, fabricate, and characterize panda type elliptical core few-mode fiber (PE-FMF) supporting six eigenmodes of LP01x, LP01y, LP11ax, LP11ay, LP11bx, and LP11by independent transmission. Such PE-FMF, with both low refractive index difference of 0.006 between the core and the cladding and low ellipticity of 1.449, can alleviate the trade-off between the eigenmode numbers and the desirable mode spacing occurring in traditional elliptical-core FMF design. The numerical results indicate that the minimal mode spacing among six eigenmodes is above 1.95 × 10-4 over the whole C + L band. The maintaining capability of both mode intensity profile and polarization is experimentally verified, when the PE-FMF is under a twisting rate range from 0 to 1.57 rad/m. During the fiber twisting, the mode intensity profile can be maintained and the polarization extinction ratio of individual eigenmode is above 20 dB over 50 m PE-FMF.