Multicore optical fibers could be next-gen PON solution

The number of optical fibers needed for access networks using passive optical network (PON) architectures is increasing demand for high-density fiber cables. An interesting solution to this congestion could be multicore fibers from OFS Laboratories (Somerset, NJ). With an outer-glass cladding diameter of 130 μm (slightly larger than conventional 125-μm-cladding-diameter communications fiber), a fiber containing seven individual cores has successfully transmitted seven upstream 1310 nm and seven downstream 1490 nm signals at 2.5 Gbit/s, each over distances of 11.3 km.

Designed for singlemode operation, the fiber has seven 8-μm-diameter fiber cores arranged in a 38 μm core-to-core pitch hexagonal array. The 130 μm clad fiber is acrylate-coated to a final outside diameter of 250 μm. Attenuation for the center core is 0.39/0.30 dB/km at 1310/1490 nm, and average attenuation for the six outer cores is 0.41/0.53 dB/km at 1310/1490 nm. Maximum crosstalk—an extremely important parameter for data transmission—is less than -38/-24 dB at 1310/1490 nm, more than adequate to meet PON requirements. To couple the multicore fiber to seven individual fibers, a special tapered multicore-fiber connector was developed by tapering and fusing the fibers to a dimension that matches the multicore fiber structure, achieving average splice loss values of 0.10 dB, comparable to conventional singlecore fibers. Contact Benyuan Zhu at [email protected].