28-GHz Wireless Carrier Heterodyned From Orthogonally Polarized Tri-Color Laser Diode for Fading-Free Long-Reach MMWoF

A 28-GHz millimeter-wave (MMW) carrier optically heterodyned from an orthogonally polarized tri-color (3λ-⊥-SCM) transmitter, which exhibits single-carrier modulation (SCM) to suppress the dispersion induced fading distortion after long-reach transmission, is demonstrated for building up the long-reach MMW-over-fiber with a distance of 75 km. The SCM-based encoding is obtained by seeding the tri-color master into slave colorless laser diode, which only supports TE-mode feedback with a polarized suppression ratio over 40 dB. After resuming back to the SCM tri-color optical carrier with orthogonal polarization (3λ-⊥-SCM), its delivered data can suppress the intensity noise induced by beating between adjacent modes such that the single-to-noise (SNR) can be improved by 2 dB. Comparing with the traditional parallel polarized multi-carrier modulation (MCM) based tri-color optical carrier (3λ-//-MCM), the orthogonally polarized tri-color optical carrier with SCM (3λ-⊥-SCM) can deliver 64 quadrature amplitude modulation orthogonal frequency-division multiplexing (QAM OFDM) data with its maximal encoding a bandwidth of 8.3 GHz (50 Gbit/s), which provides the error vector magnitude (EVM) of 8.8%, the SNR of 21.2 dB and the bit error rate of 3.5 × 10
^-3
after passing through a 75-km-long single-mode fiber. To perform the MMW wireless access network (WAN) link after 75-km fiber wired transmission, the heterodyned 28-GHz MMW carrier is obtained from the orthogonally polarized SCM tri-color optical carrier (3λ-⊥-SCM) with its peak power improved by 29 dB (from -50 to -31 dBm) and CNR enhanced by 17 dB (from 32 to 49 dB), as compared to those of the parallel polarized MCM tri-color case (3λ-//-MCM). After wireless transmission for 10-m with horn-antenna pair in free space, the maximal encoding bandwidth of the 16-QAM OFDM delivered by the orthogonally polarized SCM tri-color optical carrier (3λ-⊥-SCM) is 4.5 GHz (with 18 Gbit/s capacity).