Low-insertion-loss femtosecond laser-inscribed three-dimensional high-density mux/demux devices

Recently, transmitting diverse signals in different cores of a multicore fiber (MCF) has greatly improved the communication capacity of a single fiber. In such an MCF-based communication system, mux/demux devices with broad bandwidth are of great significance. In this work, we design and fabricate a 19-channel mux/demux device based on femtosecond laser direct writing. The fabricated mux/demux device possesses an average insertion loss of 0.88 dB and intercore crosstalk of no more than − 29.1 dB. Moreover, the fabricated mux/demux device features a broad bandwidth across the C+L band. Such a mux/demux device enables low-loss 19-core fiber (de)multiplexing over the whole C+L band, showing a convincing potential value in wavelength-space division multiplexing applications. In addition, a 19-core fiber fan-in/fan-out system is also established based on a pair of mux/demux devices in this work.