Junwen Zhang

A 400G optical wireless integration delivery system.

We experimentally demonstrate a record 400G optical wireless integration system simultaneously delivering 2 × 112 Gb/s two-channel polarization-division-multiplexing 16-ary quadrature amplitude modulation (PDM-16QAM) signal at 37.5 GHz wireless carrier and 2 × 108 Gb/s two-channel PDM quadrature phase shift keying (PDM-QPSK) signal at 100 GHz wireless carrier, adopting two millimeter-wave (mm-wave) frequency bands, two orthogonal antenna polarizations, multiple-input multiple-output (MIMO), photonic mm-wave generation and advanced digital signal processing (DSP). In the case of no fiber transmission, the bit error ratios (BERs) for both the 112 Gb/s PDM-16QAM signal after 1.5 m wireless delivery at 37.5 GHz and the 108 Gb/s PDM-QPSK signal after 0.7 m wireless delivery at 100 GHz are below the pre-forward-error-correction (pre-FEC) threshold of 3.8 × 10(-3). To our knowledge, this is the first demonstration of a 400G optical wireless integration system in mm-wave frequency bands and also a capacity record of wireless delivery.

Fiber-Wireless-Fiber Link for 100-Gb/s PDM-QPSK Signal Transmission at W-Band

We propose and experimentally demonstrate a W-band seamlessly-integrated fiber-wireless-fiber system enabled by photonic millimeter-wave generation and demodulation techniques, in which up to 109.6-Gb/s polarization division multiplexing quadrature phase shift keying signal can be first transmitted over 80-km single-mode fiber-28 (SMF-28), then delivered over a 2-m 2 × 2 multiple-input multiple-output wireless link at 95 GHz and finally transmitted over another 80-km SMF-28 with a bit-error ratio less than the third-generation forward-error-correction limitation of 2 × 102. The proposed fiber-wireless-fiber integration system has throughput comparable with that of fiber-optic communication and is suited to emergency back-up communications.

11 × 5 × 9.3Gb/s WDM-CAP-PON based on optical single-side band multi-level multi-band carrier-less amplitude and phase modulation with direct detection

We propose and demonstrate a novel WDM-CAP-PON based on optical single-side band (OSSB) multi-level multi-band carrier-less amplitude and phase modulation (MM-CAP). To enable high-speed transmission with simplified optical network unit (ONU)-side digital signal processing, 4-level 5 sub-bands CAP-16 is used here, which is generated by the digital to analogue converter (DAC). Optical single-side band (OSSB) technology is applied to extend the transmission distance against the spectrum fading effect. As a proof of concept, the experiment successfully demonstrates 11 WDM channels, 55 sub-bands, for 55 users with 9.3-Gb/s per user (after removing 7% overhead for forward error correction (FEC)) in the downstream over 40-km SMF.

W-Band 8QAM Vector Signal Generation by MZM-Based Photonic Frequency Octupling

We propose a novel scheme for photonic multiamplitude quadrature-amplitude-modulation (QAM) vector signal generation at microwave/millimeter-wave bands enabled by Mach-Zehnder modulator (MZM)-based adaptive photonic frequency multiplication. In order to attain an electrical millimeter-wave vector signal displaying multiamplitude QAM modulation, such as 8QAM, after square-law photodiode detection, the driving radio-frequency (RF) signal, carrying multiamplitude QAM transmitter data, should be both amplitude- and phase-precoded before used to drive the MZM. We experimentally demonstrate 8QAM vector signal generation at W-band adopting photonic frequency octupling (×8) enabled by our proposed scheme. The MZM is driven by a 12-GHz precoded RF signal carrying 1-GBaud 8QAM transmitter data. The generated 1-GBaud 8QAM vector signal at W-band is air transmitted over 2-m distance. To the best of our knowledge, it is the first time to realize the generation and reception of multiamplitude QAM vector signal by one external modulator at W-band.

Enhanced performance of visible light communication employing 512-QAM N-SC-FDE and DD-LMS

In this paper, a novel hybrid time-frequency adaptive equalization algorithm based on a combination of frequency domain equalization (FDE) and decision-directed least mean square (DD-LMS) is proposed and experimentally demonstrated in a Nyquist single carrier visible light communication (VLC) system. Adopting this scheme, as well with 512-ary quadrature amplitude modulation (512-QAM) and wavelength multiplexing division (WDM), an aggregate data rate of 4.22-Gb/s is successfully achieved employing a single commercially available red-green-blue (RGB) light emitting diode (LED) with low bandwidth. The measured Q-factors for 3 wavelength channels are all above the Q-limit. To the best of our knowledge, this is the highest data rate ever achieved by employing a commercially available RGB-LED.

Generation of Coherent and Frequency-Locked Multi-Carriers Using Cascaded Phase Modulators for 10 Tb/s Optical Transmission System

The generation of coherent and frequency-locked optical multi-carriers by using cascaded phase modulators and recirculating frequency shifter (RFS) based on an erbium doped fiber amplifier (EDFA) loop has been investigated theoretically and experimentally for a multi-terabit optical orthogonal frequency division multiplexing (OFDM) superchannel transmission. The phase and amplitude relationship between RF driving signals of two cascaded phase modulators and the impact of EDFA gain are analyzed. Experimental results are in good agreement with the theoretical analysis. The 112 coherent and frequency-locked subcarriers obtained after tilt filtering exhibit a tone-to-noise ratio of larger than 26 dB, a power fluctuation of less than 5 dB, and a frequency spacing of 25 GHz giving a 22.6 nm-wide optical OFDM signal spectrum. By using this method, we have successfully generated a 10-Tbit/s (112 × 100 Gbit/s) single optical OFDM polarization-division-multiplexing QPSK (PDM-QPSK) superchannel with an optical signal to noise ratio per OFDM subchannel greater than 20 dB at 0.1 nm bandwidth, and it has been transmitted over a 640-km SMF-28 and EDFA-only link with BER less than 2 × 10-3.

Multi-Modulus Blind Equalizations for Coherent Quadrature Duobinary Spectrum Shaped PM-QPSK Digital Signal Processing

A novel digital signal processing (DSP) scheme for quadrature duobinary (QDB) spectrum shaped polarization multiplexed quadrature phase shift keying (PM-QPSK) based on multi-modulus blind equalizations (MMBE) is proposed and demonstrated with both simulation and experimental results. The key algorithms for this novel digital signal processing scheme include the cascaded multi-modulus algorithm (CMMA) for blind polarization de-multiplexing, multi-modulus QPSK partitioning frequency offset estimation (FOE) and two stage carrier phase recovery (CPR) with maximum likelihood phase estimation. The final signal is detected by maximum-likelihood sequence detection (MLSD) for data BER measurement. It shows that CMMA have better frequency response performance compared with CMA for noise compression. The performances of FOE and CPR are also investigated with different spectrum shaping bandwidth, group size and laser linewidth. Finally, the feasibility of the proposed digital signal processing scheme is demonstrated by the experiment of 112 Gb/s QDB spectrum shaped PM-QPSK signal with a 25 GHz bandwidth waveshaper for Nyquist WDM channels.

QAM Vector Signal Generation by Optical Carrier Suppression and Precoding Techniques

We numerically and experimentally investigate and compare photonic constant- and multi-amplitude quadrature-amplitude-modulation (QAM) vector signal generation at radio frequency (RF) bands enabled by a Mach-Zehnder modulator (MZM)-based optical carrier suppression (OCS) modulation. In order to attain an electrical vector RF signal displaying multi-amplitude QAM modulation, such as 8 QAM and 16 QAM, after square-law photodiode detection, the driving RF signal carrying multiamplitude QAM transmitter data, should be both amplitude- and phase-precoded before used to drive the MZM. However, for constant-amplitude QAM modulation, such as quadrature-phase-shift-keying (QPSK), only phase precoding is needed. We experimentally demonstrate 1-GBd vector signal generation at 12 GHz enabled by an MZM-based OSC modulation, adopting QPSK, 8 QAM, and 16 QAM modulation, respectively. We also experimentally compare the bit error rate performance of the three different vector signals, and the QPSK case is the best, while the 16 QAM case is the worst.

432-Gb/s PDM-16QAM signal wireless delivery at W-band using optical and antenna polarization multiplexing

We have experimentally demonstrated 432-Gb/s PDM-16QAM modulated W-band wireless signal delivery adopting optical and antenna polarization multiplexing with a SE of 11.4b/s/Hz. The BER after 2-m 4×4 MIMO wireless delivery can be less than FEC threshold of 3.8×10-3.

Transmission of 8 × 480-Gb/s super-Nyquist-filtering 9-QAM-like signal at 100 GHz-grid over 5000-km SMF-28 and twenty-five 100 GHz-grid ROADMs

We experimentally demonstrate a highly filtering-tolerant multi-modulus equalization (MMEQ) process for very aggressively spectrum-shaped 9-ary quadrature-amplitude-modulation (9-QAM)-like polarization division multiplexing quadrature phase shift keying (PDM-QPSK) signal to achieve 400-Gb/s wavelength-division-multiplexing (WDM) channels on the 100-GHz grid for ultra-long-haul reach and high tolerance of the filter narrowing effect caused by reconfigurable optical add-drop multiplexers (ROADMs). We successfully transmitted 8 channels 480-Gb/s super-Nyquist (channel occupancy much less than signal baud rate) WDM signals at 100-GHz grid over 25 × 200 km conventional single-mode fiber-28 (SMF-28) with post Raman amplification and 25 ROADMs at a net spectral efficiency (SE) of 4b/s/Hz, after excluding the 20% soft-decision forward-error-correction (FEC) overhead. The system performance is significantly enhanced by the MMEQ based on 9-QAM-like constellations compared to the conventional 4 point QPSK constellation. A record transmission distance over conventional SMF-28 with a large number of ROADMs is firstly reported on the 400-Gb/s channels at 100-GHz grid.