Yu-Ting Hsueh

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.

Advanced System Technologies and Field Demonstration for In-Building Optical-Wireless Network With Integrated Broadband Services

This work describes a concept of a hierarchical radio-over-fiber (RoF) network architecture that provides both intra- and inter-network connectivity for end user wireline and wireless terminals with high-bandwidth, in-building access applications. An intelligent gateway router (IGR) is proposed as a unified platform to accommodate multi-gigabit, millimeter-wave services at 60-GHz band as well as being backward compatible with all current wireless access technologies such as WiFi and WiMAX. In addition, we further present an advanced multi-band optical carrier generation technique that can simultaneously deliver independent 60-GHz mm-wave, 2.4-GHz WiFi, and 5.8-GHz WiMAX signals efficiently carried over the same wavelength, and is suitable for the proposed IGR. Finally, we report, for the first time to our knowledge, a campus-wide field trial demonstration of RoF system transmitting uncompressed 270-Mbps standard definition (SD) and 1.485-Gbps high definition (HD) real-time video contents carried by 2.4-GHz radio and 60-GHz millimeter wave signals, respectively, between two on-campus research buildings distanced over 2.5-km standard single mode fiber (SMF-28) through the Georgia Institute of Technologys (GT) fiber network.

Multiband Signal Generation and Dispersion-Tolerant Transmission Based on Photonic Frequency Tripling Technology for 60-GHz Radio-Over-Fiber Systems

We designed and experimentally demonstrated an efficient photonic frequency-tripling technology for 60-GHz radio-over-fiber systems to simultaneously realize millimeter-wave (mm-wave), microwave, and baseband signal generation. The technique utilizes vestigial sideband filtering in combination with optical carrier suppression to generate novel alternate subcarrier modulation for high tolerance of fiber dispersion. Experimental verification of the proposed scheme is presented with generation and error-free transmission of 2.1-Gb/s data on the 63-GHz mm-wave and 21-GHz microwave carriers over 50-km single-mode fiber (SMF-28) without dispersion compensation. The power penalty for both signals is less than 1.0 dB.

A Novel Bidirectional 60-GHz Radio-Over-Fiber Scheme With Multiband Signal Generation Using a Single Intensity Modulator

We experimentally demonstrated a novel radio-over-fiber system to simultaneously generate dispersion-tolerant multiband downstream signals, including millimeter-wave, microwave, and baseband signals, based on multicarrier modulation in an intensity modulator and a subsequent optical filter. The uplink connection is realized by remodulation of downlink optical carrier and by baseband detection in the central office. The high-dispersion tolerance comes from the subcarrier cross-selection with only one data-bearing tone before signal beating in the receiver. The power penalty of 1.4 dB for 60-GHz carrier and negligible degradation for baseband and upstream are achieved for 2.5-Gb/s signal after 50-km single-mode fiber (SMF-28) and 4-m air link transmission. The theoretical analysis is also provided to obtain the optimal operation point.

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.

Multiband 60-GHz Wireless Over Fiber Access System With High Dispersion Tolerance Using Frequency Tripling Technique

A new optical millimeter-wave generation scheme to triple the beating frequency based on subcarrier multiplexing in combination with single sideband technique is proposed, capable of high tolerance of fiber chromatic dispersion. The proposed scheme can be applied to two types of multiband 60-GHz wireless over fiber access systems: one with widely separated bands including millimeter-wave, microwave and baseband and the other one with multiple 60-GHz sub-bands. Experimental verification of the proposed system with widely separated bands is presented with the generation and error-free transmission of 2.1-Gb/s data on the 63-GHz mm-wave and 21-GHz microwave carriers over 50-km single-mode fiber (SMF-28) without dispersion compensation. The power penalties caused by 50-km fiber transmission for both signals are both less than 1.0 dB at BER of 10-9 Meanwhile, simultaneous generation and transmission of multiple services at 60-GHz sub-bands are also introduced. The experimental results demonstrate the successful delivery of the 1-Gbps data carried by 60-GHz millimeter-wave both over 50-km SMF-28 and wireless distance of 6-m without any dispersion compensation. The optical receiver sensitivity of the transmission with two sub-bands degrades by 2 dB compared with the single band 60-GHz signal, and the power penalty from 50-km SMF-28 transmission is 0.8 dB at BER of 10-9. From the theoretical analysis and experimental demonstrations of the two multiband systems, it is concluded that the proposed millimeter-wave generation scheme indeed increase the transmission distance for the system with 60-GHz signal, which normally having SMF transmission distance of few tens of kilometers, by utilizing optical and electrical components with low-bandwidth requirements.

60 GHz millimeter-wave gigabit wireless services over long-reach passive optical network using remote signal regeneration and upconversion

This study proposed and experimentally demonstrated a cost-efficient scheme that can deliver 60 GHz millimeter-wave (mm-wave) multi-gigabit wireless services over 125 km long-reach passive optical networks (PONs) without any dispersion compensation. By introducing a remote local exchange (LE) stage with robust signal regeneration and all-optical upconversion functionalities, the proposed long-reach optical-wireless access network can easily accommodate over 128 users with 2.5 Gb/s shared bandwidth as well as shifting the capital expenditure of multiple hybrid optical network units (ONUs) toward single LE headend. Experimental verification shows that the power penalties for wireless and wired services are 1.8 dB and 0.4 dB at 10(-9) BER after 125 km optical fiber transmission.

Optical Millimeter-Wave Generation and Transmission Without Carrier Suppression for Single- and Multi-Band Wireless Over Fiber Applications

A new optical millimeter-wave generation scheme to double the beating frequency without suppressing the carrier by taking advantages of the out-of-phase property between sidebands of a phase-modulated optical carrier is proposed for the first time. Theoretical analysis shows that the generated 60 GHz optical millimeter-wave (mm-wave) can tolerant ±0.016 nm wavelength drifting with filter bandwidth ranging from 70 to 100 GHz to sustain first to second harmonic suppression ratio of 18 dB. The doubled frequency is continuously tunable from 60 to 90 GHz within 100 GHz filter bandwidth with RF power variation of less than 2 dB. In addition, simultaneously generating and transmitting multi-band signal: millimeter-wave band, microwave band, and baseband leveraging the same concept is also proposed. Error-free transmission of 2.5 Gb/s wireless baseband signals carried by the generated 60 GHz mm-wave is successfully demonstrated in both single- and multi-band network environments over a combined optical fiber and wireless distance with a proper equivalent isotropically radiated power of about 20 dBm for in-building access. Moreover, dispersion effect on the generated frequency-doubled optical mm-wave is analyzed by experimentally comparing the link performance of both single mode fiber (SMF-28) and dispersion-shifted fiber cases. It is concluded that for single-band service delivery, the proposed scheme is immune to the interference from the dispersion-induced, redundant 1st harmonics; however, to deliver multi-band services, launching lightwave at zero-dispersion wavelength over SMF-28 is highly recommended to mitigate inter-band interference.

Inter-Channel Crosstalk Cancellation for Nyquist-WDM Superchannel Applications

Superchannel WDM systems employ narrow channel spacing to achieve high spectral efficiency and increase channel capacity. Additionally, these systems attempt to avoid inter-channel interference (ICI) and inter-symbol interference (ISI), by creating and maintaining both spectral and temporal orthogonality. This in turn imposes a strong requirement on the spectral amplitude and phase of the received signals. For Nyquist-WDM systems, the temporal shapes are Nyquist pulses, requiring uniform spectral density with flat phase. In practice, these requirements are only partially achieved, resulting in non-ideal Nyquist systems with inter-channel interference (ICI). We propose and demonstrate two joint ICI cancellation methods based on our new “super receiver” architecture, which jointly detects and demodulates multiple subchannels simultaneously. The maximum a posteriori (MAP) algorithm is most readily implemented for systems with channel spacing equal to the baud rate, and the adaptive linear equalizer is effective for all channel spacings. Simulation results show that both joint ICI cancellation schemes outperform conventional linear equalization, approaching the performance of an isolated single channel.

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.