Bingyao Cao

DSP-Enabled Flexible ROADMs Without Optical Filters and O-E-O Conversions

Utilizing Hilbert-pair-based digital filtering, intensity modulation and passive optical coupling, optical filter- and O-E-O conversion-free ROADMs with excellent flexibility, colorlessness, gridlessness, contentionlessness, adaptability, and transparency to physical-layer network characteristics are proposed and evaluated, for the first time, which offer DSP-enabled dynamic add/drop operations at wavelength, subwavelength, and orthogonal subband levels. Extensive numerical simulations are undertaken to explore the operation characteristics of the proposed ROADMs in IMDD-based optical network nodes. It is shown that the add/drop operation performance is independent of the signals location in the digital filtering space. In addition, the results also indicate that the drop operation introduces negligible optical power penalties, while for the worst-case scenarios, optical power penalties induced by the add operation can be 3.5 dB. Furthermore, the impacts of key digital filter parameters and intensity modulation-associated drop RF signals on the ROADM add/drop performance are also investigated, based on which optimum ROADM design criteria are identified not only for effectively reducing the digital filter DSP complexity but also simultaneously improving the ROADM performance.

An Effective Sampling Frequency Offset Compensation Method for OFDMA-PON

A sampling frequency offset compensation method based on frequency domain correlation of long training symbols for OFDMA-PON is experimentally demonstrated which shows 100ppm of sampling frequency offset compensation capability under ROP of -4dBm.

A Symbol Synchronization Method Based on Gold Sequences for Real-time Upstream OFDMA-PON

A symbol synchronization method based on single carrier modulated Gold sequences for upstream OFDMA-PON is demonstrated which shows that precise synchronization can be realized and hardware logic resources requirements can be effectively released.

DSP-enabled reconfigurable and transparent spectral converters for converging optical and mobile fronthaul/backhaul networks

Dynamically reconfigurable and transparent signal spectral conversion is expected to play a vital role in seamlessly integrating traditional metropolitan optical networks and mobile fronthaul/backhaul networks. In this paper, a simple digital signal processing (DSP)-enabled spectral converter is proposed and extensively investigated, for the first time, which just utilizes a single standard dual-parallel Mach-Zehnder modulator (DP-MZM) driven by SDN-controllable RF signals and DC bias currents. As an important thrust of the paper, optimum operating conditions of the proposed converter are analytically identified, statistically examined and experimentally verified. Optimum operating condition-supported spectral converter performances in IMDD-based network nodes are explored both theoretically and experimentally in terms of frequency detuning range-dependent conversion efficiency, spectral conversion-induced OSNR/power penalty and transparency to input signal characteristics. The proposed spectral converter has unique advantages including low configuration complexity, strict transparency, SDN-controllable performance reconfigurability and flexibility, as well as negligible spectral conversion-induced latency.

Dual-drive Mach–Zehnder modulator-based reconfigurable and transparent spectral conversion for dense wavelength division multiplexing transmissions

Abstract. A digital signal process enabled dual-drive Mach–Zehnder modulator (DD-MZM)-based spectral converter is proposed and extensively investigated to realize dynamically reconfigurable and high transparent spectral conversion. As another important innovation point of the paper, to optimize the converter performance, the optimum operation conditions of the proposed converter are deduced, statistically simulated, and experimentally verified. The optimum conditions supported-converter performances are verified by detail numerical simulations and experiments in intensity-modulation and direct-detection-based network in terms of frequency detuning range-dependent conversion efficiency, strict operation transparency for user signal characteristics, impact of parasitic components on the conversion performance, as well as the converted component waveform are almost nondistortion. It is also found that the converter has the high robustness to the input signal power, optical signal-to-noise ratio variations, extinction ratio, and driving signal frequency.

Stage-Dependent DSP Operation Range Clipping-Induced Bit Resolution Reductions of Full Parallel 64-Point FFTs Incorporated in FPGA-Based Optical OFDM Receivers

The fast Fourier transform (FFT) is the fundamental algorithm at the heart of an optical OFDM (OOFDM) transceiver. The high digital signal processing (DSP) complexity has become one of the most significant obstacles to experimentally demonstrating real-time high-capacity OOFDM transceivers. In this paper, stage-dependent clipping of FFT DSP operation dynamic range is proposed and extensively explored, for the first time, based on which an improved stage-dependent minimum bit resolution map is numerically identified by taking into account the DSP operation dynamic range-clipping and precision of FFT DSP operations. The validity and high accuracy of the identified minimum bit resolution map is experimentally verified in 25 km SSMF OOFDM transmission systems based on intensity modulation and direct detection. Experimental results show that, compared to a previously reported FFT stage-dependent bit resolution map including the FFT DSP operation precision only, the improved minimum bit resolution map offers significant bit resolution reductions of up to 3-bits for full-parallel pipelined 64-point FFT architectures. As a direct result, an approximately 30% reduction in FPGA logic resource usage is achievable compared to the spiral FPGA design.

RSOA Intensity Modulator Frequency Chirp-Enhanced Optical OFDM PON Performance

A reflective semiconductor optical amplifier intensity modulator (RSOA-IM) frequency chirp considerably increases the system frequency response of an intensity-modulation and direct-detection (IMDD) PON system over the passband signal spectral region. Adaptive bit and power loading of optical OFDM (OOFDM) enables full use of the RSOA-IM frequency chirp-enhanced passband system frequency response characteristics. As a direct result, without requiring extra electrical and optical equalization schemes, an RSOA-IM with a 3-dB small-signal modulation bandwidth as low as 1 GHz can support 40 Gb/s OOFDM signal transmissions over 25 km SSMF IMDD PON systems free from optical amplification and chromatic dispersion compensation. This paper suggests that significantly relaxed requirements on both RSOA-IMs 3-dB small-signal modulation bandwidth and frequency chirp are feasible for achieving desired OOFDM transmission performances for next-generation PONs.

RSOA intensity modulator frequency chirp-enabled 40Gb/s over 25km IMDD PON systems

Adaptive bit and power loading of optical OFDM (OOFDM) enables full utilizations of RSOA intensity modulator (RSOA-IM) frequency chirps to significantly enhance system performances. 1GHz-RSOA-IMs can support 40Gb/s@25km OOFDM transmissions in simple IMDD PON systems.

Yb 3+ -doped Ultra-Short Pulse Fibre Laser with QPM based Nonlinearity Compensation

An ultra-short pulse fibre laser with QPM based nonlinearity compensation is proposed. Simulation results demonstrate that nonlinearity impairment caused by third-order Kerr effect can be effectively compensated with self-defocusing of cascaded second-order nonlinear in PPLN

An ONUs Requesting based Full-Range Dynamic Bandwidth Allocation for OFDMA-PON With SLA and CoS

An ONUs requesting based full-range dynamic bandwidth allocation for OFDMA-PON with SLA and CoS is proposed to enhance the QoS of the system with adaptive cycle time scheme more effectively.