Ultrahigh Capacity MMWoF Link Using 2-λ VCSEL Front-Haul Transmitter Encoded With Broadband Generalized FDM Data Stream

By employing a dual-wavelength (2-λ) vertical cavity surface emitting laser (VCSEL) directly encoded by novel quadrature amplitude modulation generalized frequency division multiplexing (QAM-GFDM) modulation schemes with optimized data capacity, a 28-GHz millimeter-wave-over-fiber (MMWoF) link is created for fusing the long-reach single-mode-fiber wired network and the beyond fifth generation (B5G) mobile wireless network without using any localized synthesizer and mixer at the remote receiver end. Detuning the
k
subcarrier to 2 optimizes the electrical-to-electrical 5-GHz 64-QAM-GFDM link with an error vector magnitude (EVM) of 3.04%, a signal-to-noise ratio (SNR) of 30.3 dB and a bit error ratio (BER) of 2.1×10
⁻¹³
. By using this condition to perform the long-reach 50-km optical transmission, the 5-GHz 64-QAM GFDM carried by the 2-λ VCSEL exhibits an SNR of 23.8 dB, an EVM of 6.47% and a BER of 2.2×10
⁻⁴
. By fixing the optimized
k
subcarriers, the maximal bandwidth and raw data rate of the 64-QAM-GFDM transmission can be achieved to 6.75 GHz and 40 Gbit/s, respectively. For the wireless transmission at the remote end, the photo-mixed MMW carrier at 28-GHz exhibits a peak power of −11.4 dBm and a carrier-to-noise ratio (CNR) of 45 dB. After performing the self-heterodyne down-conversion via power envelope detection, the receiving data amplitude is improved from 26.2 to 132 mV with adding a 3-dB attenuator for impedance matching. Under the 2-m wireless transmission via horn antenna pair, the maximal bandwidth and data rate of the received 4-QAM GFDM data respectively achieve 2 GHz and 4 Gbit/s.