We investigate the transmission performance of 28-Gb/s nonreturn-to-zero on-off keying (NRZ-OOK), duobinary, and four-level pulse amplitude modulation signals over different fiber lengths without any inline amplification or pre/ post-processing digital signal processing technique by utilizing an O-band 18G-class directly modulated laser (DML). By experiment, it is verified that negligible sensitivity penalty is introduced by DML chirp effect after fiber transmission, which is due to the extremely low dispersion of O-band wavelengths. Meanwhile, the results indicate that NRZ-OOK outperforms the other two formats in receiver sensitivity, and for 20-km transmission, a power budget of 25.5 dB is achieved without pre-amplification. According to the experimental results, O-band DML-based NRZ-OOK transmission is a cost-effective solution for future 100G-EPON.

A bandwidth-efficient and low-cost spectral-null-filling scheme simultaneously delivering a 56-Gbps 4-level pulse amplitude modulation (PAM-4) digital signal and a 10×400-MHz analog radio frequency (RF) signal on a single wavelength is demonstrated for high-capacity wired and wireless optical access networks. The data rate of the PAM-4 signal is consistent with the next-generation passive optical network (PON), and the PAM-4 signal inherently provides a spectral null at 28 GHz, which can be filled with the RF signal exactly at the 5G-specified millimeter wave (mmW) band. Since pulse shaping is not essential in this hybrid transmission system, a low-cost 2-bit digital-to-analog converter (DAC) is adopted for the PAM-4 signal generation. Volterra nonlinear equalizer is adopted to effectively eliminate the analog-to-digital crosstalk without reserving a frequency gap in between. The digital-analog hybrid signal is simultaneously transmitted over a 25-km standard single-mode fiber in telecom C-band and the impact of chromatic dispersion on the number of supported mmW bands is analyzed. In addition, three types of hybrid transmitters are experimentally demonstrated, among which the first-time proposed IQ-modulator-based hybrid transmitter shows the best performance.

Bandwidth-efficient 5G optical fronthaul interfaces, such as the Ethernet-based common public radio interface (eCPRI), with novel low layer split (LLS) are being actively investigated. Regarding the uplink eCPRI, the burdened wireless resource blocks (RBs) are delivered and the traffic aggregation is leveraged; therefore, the eCPRI traffic is highly dynamic depending on the time-varying mobile traffic load. This dynamic property will lower the average fiber link utilization and complicate the sizing of link bandwidth for the deployment of low-latency fronthaul. To tackle this issue, we propose a load-adaptive quantization resolution scheme that enables elastic fronthaul capacity. By adjusting the quantization resolution of the resource elements in RBs, the fronthaul link capacity, measured by the amount of bearable RBs, can be scaled to fit the mobile traffic load. Specifically, a full resolution is applied during low-load period, while for high-load case, to boost the link capacity, a stringent resolution is performed by removing the least significant quantization bits (LSQBs). Besides, to minimize the signal fidelity deterioration caused by the decline of resolution, the resolution redundancy is evaluated based on the detected wireless signal quality at central unit, and the location of LSQBs is fed back to the radio unit through the eCPRI control plane. With the enhanced link flexibility, the required fronthaul bandwidth can be significantly reduced, while the user experience is barely compromised. Based on our developed low-MAC and PHY-layer wireless system model following 3GPP specifications and the 25-Gb/λ experimental fiber transmission, the bandwidth of eCPRI user data can be saved by 40%.

In this letter, for the first time, we propose to employ the adaptive frequency-domain pre-equalization (FDPE) into an electro-absorption modulator laser (EML)-based optical self-interference cancellation (OSIC) system to suppress the time-varying multipath radio frequency (RF) self-interference (SI) signal, which is implemented for in-band full-duplex (IBFD) communication. Faced with time-varying multipath wireless channel, the OSIC system estimates multipath channel response using a least square estimation algorithm, and adjusts the coefficients of frequency-domain pre-equalizer adaptively to combat time-varying multipath SI. Based on the proposed FDPE-aided OSIC, the IBFD transmission of OFDM RF signals with time-varying multipath channel is demonstrated experimentally, achieving 30-dB OSIC depth over 1.22-GHz broad baseband.

Si is used to synthesize a Si@SiOC@Li₂Si₂O₅ (SSL) anode materials with high specific capacity and high initial coulombic efficiency.

For the future high-speed next-generation Ethernet Passive Optical Network (NG-EPON) system, the low-cost system could be kept by adopting low bandwidth devices. To compensate the signal distortion and improve the performance of high-speed bandwidth limited system, we propose a special feature vector construction to achieve a new equalizer scheme based on support vector machines (SVM) classifier. For the first time, we mathematically analyze the model of the bandwidth-limited optical transmission system and theoretically derive the linear separability of the proposed feature vector formed linear hyperplane in 100-Gb/s NG-EPON system. Furthermore, 4໗25-Gb/s non-return to zero (NRZ) and 2໗ 50-Gb/s four-level pulse amplitude modulation (PAM-4) per wavelength transmission experiments with 10-G class optics system are demonstrated to prove the feasibility of our scheme. Experimental results show that, for 25-Gb/s/λI NRZ transmission, compared to the decision feedback equalizer (DFE) and feed-forward equalizer (FFE), the receiver sensitivity achieved by our scheme can be improved by about 0.5-dB @BER=3.8e-3 with limited training sequence. For the 50-Gb/s/λI PAM-4 case, the SVM-based equalization method improves the receiver sensitivity for about 1-dB.