Shu-Hao Fan

A Novel Lightwave Centralized Bidirectional Hybrid Access Network: Seamless Integration of RoF With WDM-OFDM-PON

We experimentally demonstrated a novel lightwave centralized hybrid bidirectional access network for integration of wavelength-division-multiplexing orthogonal frequency-division multiplexing passive optical network (WDM-OFDM-PON) with radio-over-fiber systems employing multiwavelength generation and the carrier-reuse technique. In this proposed architecture, one of the main impairments of bidirectional transmission over single fiber link, Rayleigh backscattering, can be reduced, because of different frequencies for downlinks and uplinks. In the wired transmission over 25-km single-mode fiber (SMF-28), power penalties are less than 0.5 dB for both 11.29-Gb/s OFDM-16 quadrature amplitude modulation (16QAM) downlink and 5.65-Gb/s OFDM quadrature phase-shift keying (QPSK) uplink. Moreover, successful access network transmissions have been demonstrated since the error vector magnitude (EVM) measurements for worldwide interoperability for microwave access (WiMAX) 17.28-Mb/s OFDM-64QAM downstream and 11.52-Mb/s OFDM-16QAM upstream are always under the thresholds of IEEE 802.16e.

A Fast and Efficient Frequency Offset Correction Technique for Coherent Optical Orthogonal Frequency Division Multiplexing

A wide-range frequency offset correction is an essential function in the coherent-detection optical (CO) orthogonal frequency division multiplexing (OFDM) system. However, unlike conventional radio-frequency OFDM systems, the frequency offsets of CO systems come from the laser instability and bring much higher randomness and uncertainty between the local oscillation source and the incoming signal. Therefore, it is difficult to achieve low complexity and high precision for the frequency offset estimation at the same time. To fulfill the requirement of the CO-OFDM transmission system, we propose a novel algorithm using sample-shifted training symbols for the fast acquisition of the frequency offset in the CO-OFDM system. Based on the characteristics of optical coherency and the CO-OFDM symbol interval, the dynamic tracking of the frequency offset variation can also be simplified by using the OFDM pilot subcarriers.

Efficient Delivery of Integrated Wired and Wireless Services in UDWDM-RoF-PON Coherent Access Network

A high-capacity coherent ultradense wavelength-division multiplexing passive optical network integrated with a 60-GHz radio-over-fiber system has been designed and experimentally demonstrated for the first time. In this proposed architecture, millimeter-wave signal generation is achieved by coherent technology, in place of the optical carrier suppression technique, which requires modulators with large bandwidth and precise optical interleavers. The system fully exploits advantages of coherent access networks to provide both multigigabit wired and wireless access services with high spectral and power efficiencies. Successful wireless transmission of multichannel 3.3-Gb/s quadrature phase-shift keying signals with 10-GHz channel spacing over 50-km single-mode fiber (SMF-28) has been achieved.

Simultaneous Transmission of Wireless and Wireline Services Using a Single 60-GHz Radio-Over-Fiber Channel by Coherent Subcarrier Modulation

We proposed and experimentally demonstrated a novel hybrid subcarrier modulation (H-SCM) technique to generate a spectral-efficient 60-GHz optical millimeter-wave (mm-wave) that carries independent 2.5-Gb/s wireless and 10-Gb/s wireline signals using intensity and phase modulation, respectively. The frequency beating components of the 60-GHz channel due to interleaved and imbalanced optical path in H-SCM are numerically analyzed and experimentally measured in terms of timing jitter and amplitude fluctuation. The generated 60-GHz optical mm-wave signal using H-SCM with phase noise variance of about 0.5 is demonstrated in a radio-over-fiber testbed propagating through a combined distance of 25-km fiber and 4-m free space. The power penalties for the received wireless and wireline signals are 1 and 0.2 dB at 10-9 bit-error rate, respectively.

Efficient Optical Millimeter-Wave Generation Using a Frequency-Tripling Fabry–Pérot Laser With Sideband Injection and Synchronization

We propose and demonstrate a low-cost 40-GHz optical millimeter-wave (mm-wave) generation scheme constructed by the utilization of a frequency-tripling directly modulated Fabry-Pérot (FP) laser. The scheme requires neither a strong optical injection power nor an additional optical filter to select the desired optical sidebands. Error-free transmission of the generated 40.2-GHz optical mm-wave carrying 2.5-Gb/s signal over a 20-km standard single-mode fiber (SSMF) has been experimentally demonstrated. In addition, a performance comparison with the conventional case of an injection-locked FP laser directly driven with a 40.2-GHz RF signal is also simulated, which shows that the presented scheme with highly reduced bandwidth requirement is suitable for mm-wave radio-over-fiber (RoF) systems.

Generation and transmission of multiband and multi-gigabit 60-GHz MMW signals in an RoF system with frequency quintupling technique.

We propose and experimentally demonstrate a cost-effective radio-over-fiber (RoF) system to simultaneously generate and transmit multiband and multi-gigabit 60-GHz millimeter wave (MMW) signals using frequency quintupling technique. Multiband signals at 56-GHz and 60-GHz are realized with two cascaded single-drive Mach-Zehnder modulators (MZMs), where phase control is not required. Furthermore, only low-frequency (≤12GHz) optical and electrical devices are used in the central station (CS), which enable a cost-effective system. At the user-terminal, two-stage down-conversions are employed by envelope detection (ED) and intermediate frequency (IF) mixing, eliminating expensive high-speed synthesizer and critical phase control components. Error-free performances are achieved for the multiband MMW signals after 50-km single-mode fiber (SMF) and 10-ft wireless link transmissions.

Generation of Multiband Signals in a Bidirectional Wireless Over Fiber System With High Scalability Using Heterodyne Mixing Technique

We propose and experimentally demonstrate a bidirectional radio over fiber system to simultaneously generate and transmit downstream multiband signals and upstream data. To the best of our knowledge, this is the first time that the multiband signals, including baseband, 24-GHz microwave (MW), and 42- and 60-GHz millimeter-wave (MMW) signals, are realized through multicarrier generation and heterodyne mixing techniques. The frequencies of the MW and MMW signals are continuously tunable, thus high scalability can be achieved. In the base station, part of the continuous wave light is used as an optical carrier for upstream data, which is transmitted back to the central station though the same fiber. Error-free performances are achieved for all the signals after 25-km single-mode fiber and 5 ft air link transmission for wireless data.

A novel radio-over-fiber system using the xy-MIMO wireless technique for enhanced radio spectral efficiency

By combining two different system technologies of optical polarization division multiplexing and wireless multiple-input, multiple-output spatial multiplexing, we have successfully demonstrated 2-Gb/s or 5-Gb/s wireless signal transmission over a 60-GHz wireless channel with a doubled spectral efficiency.

Next-generation E-health communication infrastructure using converged super-broadband optical and wireless access system

Delivering affordable high-quality E-health care services requires effective telecommunication and multimedia technologies in conjunction with medical expertise. In this paper, we propose and demonstrate a telecommunication and networking architecture for implementing next generation Telemedicine and Telehealth systems. Our integrated optical-wireless based network provides super broadband, ultra low-latency connectivity for voice, video, image and data across various telemedicine modalities to facilitate real-time and near real-time communication of remote health care information.

Compact polymeric four-wavelength multiplexers based on cascaded step-size MMI for 1G/10G hybrid TDM-PON applications

A novel polymeric four-wavelength multiplexer based on a new design concept of cascaded step-size multimode interferometer (CSS-MMI) is first presented. It can be fabricated by using planar lightwave circuit (PLC) technology and is highly compatible with both current 1-Gbps and future 10Gbps optical transceivers for applications in next generation 1-Gbps and 10-Gbps coexisting time-division-multiplexed passive optical network (TDM PON). By combining two types of proposed CSS-MMI 1??2 wavelength splitters, a compact 1.5cm-long four wavelength multiplexer is realized without requiring complicated design and tedious calculation. In addition, the upstream wavelength channel at 1310 nm has 0.18 dB low insertion loss and three downstream wavelength channels at 1490 nm, 1550 nm and 1590 nm exhibit insertion losses of 1.21 dB, 1.34 dB and 1.02 dB, respectively, with their extinction ratios ranging from 11.71 dB to 32.07 dB.