Ming-Fang Huang

Key Technologies of WDM-PON for Future Converged Optical Broadband Access Networks [Invited]

The wavelength-division-multiplexed passive optical network (WDM-PON) is considered to be the next evolutionary solution for a simplified and future-proofed access system that can accommodate exponential traffic growth and bandwidth-hungry new applications. WDM-PON mitigates the complicated time-sharing and power budget issues in time-division-multiplexed PON (TDM-PON) by providing virtual point-to-point optical connectivity to multiple end users through a dedicated pair of wavelengths. There are a few hurdles to overcome before WDM-PON sees widespread deployment. Several key enabling technologies for converged WDM-PON systems are demonstrated, including the techniques for longer reach, higher data rate, and higher spectral efficiency. The cost-efficient architectures are designed for single-source systems and resilient protection for traffic restoration. We also develop the integrated schemes with radio-over-fiber (RoF)-based optical-wireless access systems to serve both fixed and mobile users in the converged optical platform.

101.7-Tb/s (370×294-Gb/s) PDM-128QAM-OFDM transmission over 3×55-km SSMF using pilot-based phase noise mitigation

Record capacity transmission of 101.7-Tb/s (370×294-Gb/s) is performed over 3×55 km SSMF using PDM-128QAM-OFDM modulation and pilot-based phase noise mitigation. Achieved spectral efficiency of 11 bits/s/Hz is the highest reported to date for WDM transmission.

Centralized Lightwave WDM-PON Employing 16-QAM Intensity Modulated OFDM Downstream and OOK Modulated Upstream Signals

We have proposed and experimentally demonstrated a novel architecture for orthogonal frequency-division- multiplexing (OFDM) wavelength-division-multiplexing passive optical network with centralized lightwave. In this architecture, 16 quadrature amplitude modulation intensity-modulated OFDM signals at 10 Gb/s are utilized for downstream transmission. A wavelength-reuse scheme is employed to carry the upstream data to reduce the cost at optical network unit. By using one intensity modulator, the downstream signal is remodulated for upstream on-off keying (OOK) data at 2.5 Gb/s based on its return-to-zero shape waveform. We have also studied the fading effect caused by double-sideband (DSB) downstream signals. Measurement results show that 2.5-dB power penalty is caused by the fading effect. The fading effect can be removed when the DSB OFDM downstream signals are converted to single sideband (SSB) after vestigial filtering. The power penalty is negligible for both SSB OFDM downstream and the remodulated OOK upstream signals after over 25-km standard single-mode-fiber transmission. Index

Cost-Effective Optical Millimeter Technologies and Field Demonstrations for Very High Throughput Wireless-Over-Fiber Access Systems

The broadband penetration and continuing growth of Internet traffic among residential and business customers are driving the migration of todays end users network access from cable to optical fiber and superbroadband wireless systems The integration of optical and wireless systems operating at much higher carrier frequencies in the millimeter-wave (mm-wave) range is considered to be one of the most promising solutions for increasing the existing capacity and mobility, as well as decreasing the costs in next-generation optical access networks. In this paper, several key enabling technologies for very high throughput wireless-over-fiber networks are reviewed, including photonic mm-wave generation based on external modulation or nonlinear effects, spectrum-efficient multicarrier orthogonal frequency-division multiplexing and single-carrier multilevel signal modulation. We also demonstrated some applications in wireless-over-fiber trials using these enabling techniques. The results show that the integrated systems are practical solutions to offer very high throughput wireless to end users in optically enabled wireless access networks.

A Novel Scheme to Generate Single-Sideband Millimeter-Wave Signals by Using Low-Frequency Local Oscillator Signal

We have proposed and experimentally demonstrated a novel scheme to generate optical millimeter-wave (mm-wave) signals by using single-sideband modulation with low-frequency local oscillator (LO) signals. In this architecture, by incorporating the proper dc bias of the modulator in central office, the optical mm-wave carriers are generated with two times frequency of the LO signal while largely reducing the bandwidth requirement of the modulator. We quantify the optical carrier-to-sideband ratio (CSR) of downstream transmission in this radio-over-fiber (ROF) link and establish that the performance of the ROF system can be significantly improved when the optical signals are transmitted at CSR equal to 0 dB.

64-Tb/s, 8 b/s/Hz, PDM-36QAM Transmission Over 320 km Using Both Pre- and Post-Transmission Digital Signal Processing

We report the successful transmission of 64 Tb/s capacity (640 ×107 Gb/s with 12.5 GHz channel spacing) over 320 km reach utilizing 8-THz of spectrum in the C+L -bands at a net spectral efficiency of 8 bit/s/Hz. Such a result is accomplished by the use of raised-cosine pulse-shaped PDM-36QAM modulation, intradyne detection, both pre- and post-transmission digital equalization, and ultra-large-area fiber. We discuss in detail the digital modulation technology and signal processing algorithms used in the experiment, including a new two-stage, blind frequency-search-based frequency-offset estimation algorithm and a more computationally efficient carrier-phase recovery algorithm.

High Capacity/Spectral Efficiency 101.7-Tb/s WDM Transmission Using PDM-128QAM-OFDM Over 165-km SSMF Within C- and L-Bands

We experimentally demonstrate 101.7-Tb/s transmission over 355 km spans of standard single-mode fiber (SSMF) at a net spectral efficiency of 11 b/s/Hz. A total of 370 dense wavelength-division multiplexed (DWDM) channels spanning the optical C- and L-bands spaced at 25 GHz were used. Each 25-GHz channel were subdivided into four subbands, with each subband carrying a 73.5-Gb/s orthogonal frequency-division multiplexed (OFDM) signal modulated with polarization-division-multiplexing (PDM) 128-ary quadrature amplitude modulation (QAM) at each modulated subcarrier. This experiment was enabled by digital signal processing (DSP) pre-equalization of transmitter impairments, all Raman amplification, heterodyne coherent detection, and DSP postequalization of the channel and receiver impairments, including pilot-based phase noise compensation.

1.05Pb/s Transmission with 109b/s/Hz Spectral Efficiency using Hybrid Single- and Few-Mode Cores

We demonstrated 1.05-Pb/s transmission over 3km of multicore fiber with spectral efficiency of 109b/s/Hz, using twelve single-mode cores carrying DP-32QAM-OFDM signals and two few-mode cores carrying DP-QPSK in their LP01 and two LP11 modes.

Transmission of 32-Tb/s Capacity Over 580 km Using RZ-Shaped PDM-8QAM Modulation Format and Cascaded Multimodulus Blind Equalization Algorithm

In this paper, we propose a novel synthesizing method for high-speed 8-ary quadratic-amplitude modulation (QAM) optical signal generation using commercial optical modulators with binary electrical driving signals. Using this method, we successfully generated 114-Gb/s pulse-duration modulation (PDM)-8QAM optical signals. Intradyne detection of PDM-8QAM optical signals with robust blind polarization demultiplexing has been demonstrated by using a new cascaded multimodulus equalization algorithm. With return-to-zero-shaped PDM-8QAM modulation and the proposed blind polarization demultiplexing algorithm, we demonstrate transmission of a record 32-Tb/s fiber capacity (320 × 114 Gb/s) over 580 km of ultralow-loss single-mode fiber-28 fiber by utilizing C+L-band erbium-doped fiber-amplifier-only optical amplification and single-ended coherent detection technique at an information spectral efficiency of 4.0 bit/s·Hz.

Polarization Insensitive Wavelength Conversion for 4×112Gbit/s Polarization Multiplexing RZ-QPSK Signals

In this paper, polarization-insensitive wavelength conversion based on orthogonal-pumps and four-wave mixing in HNLF is experimentally demonstrated for high-speed 112-Gb/s PolMux-RZ-QPSK transmission with digital coherent detection. The conversion performance of the proposed scheme is investigated for both single- and four-channel input signals, with the achieved post-conversion OSNR for the two cases shown to be 30 and 20 dB, respectively. Moreover, it is shown that the OSNR of the converted single-channel signal can be maintained above 25 dB even if the wavelength spacing between the original and converted signals is larger than 25 nm. Finally, the BER of 4x112-Gb/s PolMux-RZQPSK converted signals after 1 km HNLF transmission is measured to be below 1x10(-4). The optimum OSNR and launched HNLF power are also investigated.