Two-core fiber-based mode converter and mode demultiplexer

Abstract

Multicore fibers and few-mode fibers are potential candidates for achieving high-capacity space division multiplexing and mode division multiplexing (MDM) systems. Mode converters are an essential part of any MDM for effectively launching light into the desired mode. Fiber-based mode converters will be more useful than bulk converters because of their compatibility and ease of use. In this contribution, a two-core fiber-based mode converter design is proposed that can effectively convert the fundamental LP01 mode into the LP11 mode by mode coupling. This device can also be used as a demultiplexer in the reverse operation. Such a mode converter can be fabricated by heating a piece of two-core fiber with the thermally diffused core technique. This leads to the diffusion of dopants into the cladding, resulting in an expanded core giving power coupling between the cores. The conversion efficiency of this converter is −0.5  dB at the optimum value. This all-fiber mode converter ensures an extinction ratio of more than 30 dB over 45 nm wavelength, which covers the entire C band. The robustness of the proposed design is analyzed by evaluating the effect of changes in design parameters on the conversion efficiency and extinction ratios.