Based on a silicon platform, we design and fabricate a four-mode division (de)multiplexer for chip-scale optical data transmission in the 2 μm waveband for the first time, to the best of our knowledge. The (de)multiplexer is composed of three tapered directional couplers for both mode multiplexing and demultiplexing processes. In the experiment, the average crosstalk for four channels is measured to be less than $18\mathrm{dB}$ over a wide wavelength range (70 nm) from 1950 to 2020 nm, and the insertion losses are also assessed. Moreover, we further demonstrate stable 5 Gbit/s direct modulation data transmission through the fabricated silicon photonic devices with non-return-to-zero on–off keying signals. The experimental results show clear eye diagrams, and the penalties at a bit error rate of $3.8\times {10}^3$ are all less than 2.5 dB after on-chip data transmission. The obtained results indicate that the presented silicon four-mode division multiplexer in the mid-infrared wavelength band might be a promising candidate facilitating chip-scale high-speed optical interconnects.