Tbit/s Mid-IR Free-Space Optical Communications Enabled by Three-Dimensional Channel Multiplexing of Wavelength, Polarization, and Spatial Mode

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Abstract
We experimentally demonstrate a >Tbit/s mid-infrared (mid-IR) free-space optical (FSO) communication system by combining wavelength-division multiplexing (WDM), polarization-division multiplexing (PDM), and mode-division multiplexing (MDM). We transmit 16 multiplexed data channels simultaneously by employing 4 wavelengths at ∼3.4 μm, 2 polarizations, and 2 orbital angular momentum (OAM) modes with orders of ℓ = +1 and ℓ = +3. The channels are generated in the C-band at the transmitter and converted to mid-IR through difference frequency generation (DFG) nonlinear process. At the receiver, they are converted back to C-band through DFG and detected in the C-band. With each channel carrying a 32-Gbaud QPSK signal, a total data rate of 1.024 Tbit/s is achieved. Our experimental results show that (i) the channel crosstalk between different wavelengths, polarizations, and modes are less than -19 dB, -16 dB, and -15 dB, respectively, (ii) bit-error rates of all multiplexed channels can reach below the 20% forward error correction threshold, and (iii) there is <1-dB optical signal-to-noise ratio (OSNR) penalty induced by channel multiplexing in a single domain (WDM, PDM, or MDM alone), while the OSNR penalty increases to ∼2 dB when combining the three multiplexing schemes.
Funding Information
  • Airbus Institute for Engineering Research
  • Office of Naval Research (N0001420-1-2558)

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