Po-Tsung Shih

Ultra-High Data-Rate 60 GHz Radio-Over-Fiber Systems Employing Optical Frequency Multiplication and OFDM Formats

The increasing demand for wireless video-based interactive and multimedia data services explains why 60-GHz millimeter-wave wireless system is a promising candidate to provide multi-gigabit-per-second wireless services. While attempting to generate and transmit 60 GHz signals in a wireless system cost effectively and increase the spectral efficiency to facilitate multi-gigabit-per-second services, this work reviews three radio-over-fiber (RoF) systems based on optical frequency multiplication (up to 6 times) to reduce the bandwidth requirement of optical transmitters. Additionally, orthogonal frequency division multiplexing (OFDM) signals with multi-level modulation formats (16 QAM) are utilized to achieve an ultrahigh data rate of 28 Gbps within the 7-GHz license-free band and compensate for an uneven frequency response of 60-GHz RoF systems. Negligible power penalty following 25-km standard single mode fiber (SSMF) transmission is observed, capable of significantly extending the service range to various applications within a building or campus.

Optical Millimeter-Wave Signal Generation Via Frequency 12-Tupling

This work demonstrates the feasibility of optical millimeter-wave signal generation using frequency 12-tupling. Optical millimeter-wave signal with two sixth-order optical sidebands are generated using frequency quadrupling optical millimeter-wave generation along with optical four-wave-mixing. 210- and 120-GHz two-tone optical signals with optical carrier and undesired harmonic distortion suppression ratios of 20 and 30 dB are experimentally demonstrated. The proposed system provides an attractive method for millimeter-wave applications such as optical up-conversion in radio-over-fiber (RoF) communication systems at millimeter-wave band, phase-array antennas, optical sensors, radars, and tera-hertz applications.

A continuously tunable and filterless optical millimeter-wave generation via frequency octupling.

This work proposes a cost-effective, continuously tunable and filterless optical millimeter-wave (MMW) signal generation employing frequency octupling. Optical MMW signals with 30-dB undesired sideband suppression ratios can be obtained. Since no optical filtering is required, the proposed system can be readily implemented in wavelength-division-multiplexing (WDM) systems. V-band 60-GHz and W-band 80-GHz optical MMW signals are experimentally demonstrated. Because of the high undesired sideband suppression ratio, 60-GHz waveform with 50% duty cycle is observed. The single-sideband (SSB) phase noise of the generated 60-GHz signal is -73 dBc/Hz at 10 kHz. The proposed system is a viable solution for the future ultra-high frequency MMW applications up to 320 GHz using the external modulator with a limited bandwidth of 40 GHz.

Photonic vector signal generation at microwave/millimeter-wave bands employing an optical frequency quadrupling scheme

To the best of our knowledge, a novel photonic architecture to generate vector signals at microwave/millimeter-wave bands employing an optical frequency quadrupling technique based on an external dual-parallel modulator is proposed for the first time. A 312.5 MSym/s quadruple phase-shift keying signal at 25 GHz is experimentally demonstrated using properly precoding driving signal at 6.25 GHz, and optical power penalty is negligible following 50 km single-mode fiber transmission.

WDM up-conversion employing frequency quadrupling in optical modulator.

This work presents an optical up-conversion system with frequency quadrupling for wavelength-division-multiplexing (WDM) communication systems using a dual-parallel Mach-Zehnder modulator without optical filtering. Four-channel 1.25-Gb/s wired fiber-to-the-x (FTTx) and wireless radio-over-fiber (RoF) signals are generated and transmitted simultaneously. Moreover, the decline in receiver sensitivities due to Mach-Zehnder modulator bias drifts is also investigated. Receiver power penalties of the 20-GHz up-converted WDM signals and baseband (BB) FTTx signals are less than 1 dB when bias deviation voltage is less the 20% of the half-wave voltage. After transmission over a 50-km SSMF, the receiver power penalties of both the BB and 20-GHz RF OOK signals are less than 1 dB. Notably, 60-GHz optical up-conversion can be achieved using 15-GHz radio frequency (RF) components and equipment.

Simple 14-Gb/s Short-Range Radio-Over-Fiber System Employing a Single-Electrode MZM for 60-GHz Wireless Applications

This paper demonstrates the feasibility of a simple multigigabit-per-second (Gbps) radio-over-fiber (RoF) system employing multilevel orthogonal frequency-division-multiplexing (OFDM) signal modulation at 60 GHz and a single-electrode Mach-Zehnder modulator (MZM). In this paper, the impact of fiber chromatic dispersion and OFDM beat noise on the performance of the RoF system are investigated by theoretical analysis, VPI WDM-TransmissionMaker simulation and experimental demonstration. A 13.875-Gb/s QPSK OFDM signal occupying the full 7-GHz license-free band at 60 GHz with frequency multiplication for the RoF link is demonstrated. After 3 km of standard single-mode fiber transmission with no dispersion compensation, the power penalty is less than 3 dB.

Optical Millimeter-Wave Up-Conversion Employing Frequency Quadrupling Without Optical Filtering

This study presents two optical frequency quadrupling techniques for generating high-purity millimeter-wave signals with optical carrier suppression. To our best knowledge, this investigation demonstrates for the first time that a frequency quadrupling system requires only a single integrated Mach-Zehnder modulator without an optical narrowband filter to remove undesired optical sidebands. Since no optical filter is needed, fast frequency tuning is straightforward and this approach is particularly attractive for the optical up-conversion in the wavelength-division-multiplexing radio-over-fiber systems. This study provides both theoretical analysis and experimental demonstration. The generated optical millimeter-wave signals are of very high quality with optical carrier and undesired harmonic distortion suppression ratio of more than 36 dB.

28-Gb/s 16-QAM OFDM radio-over-fiber system within 7-GHz license-free band at 60 GHz employing all-optical up-conversion

A record 28-Gb/s 16-QAM OFDM system within 7-GHz license-free band at 60 GHz employing all-optical up-conversion with frequency quintupling is experimentally demonstrated. Negligible penalty is observed following 100-km SMF transmission without any dispersion compensation.

Full duplex 60-GHz RoF link employing tandem single sideband modulation scheme and high spectral efficiency modulation format.

This study proposes a full duplex 60-GHz band radio-over-fiber (RoF) link using a modified tandem single sideband (TSSB) modulation scheme with frequency doubling. Based on the modified TSSB modulation scheme, no dispersion induced fading is observed; high spectral efficiency vector signal can be utilized; and wavelength reuse can also be achieved. Both single carrier 8-QAM and QPSK-OFDM signals for down-link transmissions are experimentally demonstrated. After transmission of 50-km SSMF, no significant receiver power penalties are observed. Wavelength reuses with 1.25-Gb/s OOK using a reflective semiconductor optical amplifier (RSOA) for up-link transmission are also demonstrated. After transmission of 50-km SSMF, no significant receiver power penalties are also observed.

Photonic vector signal generation employing a novel optical direct-detection in-phase/quadrature-phase upconversion

This work demonstrates the feasibility of the generation of an RF direct-detection vector signal using optical in-phase/quadrature-phase (I/Q) upconversion. The advantage of the proposed transmitter is that no electrical mixer is needed to generate the RF signal. Therefore, I/Q data of RF signals are processed at baseband at the transmitter, which is independent of the carrier frequency of the generated RF signal. A 10 Gb/s 16 quadrature amplitude modulation signal is experimentally demonstrated. Following transmission over a 50 km single-mode fiber, the power penalty is negligible. Moreover, I/Q imbalance of the proposed transmitter is studied and compensated by digital signal processing, which is both numerically and experimentally verified.