采用单个相位调制器产生毫米波

实验研究了采用单个相位调制器(PM)产生毫米波的方案。该方案采用电混频器将射频(RF)信号与基带信号混频后再利用相位调制器产生双边带调制(DSB)信号,经光纤传输到基站后用一个光交叉复用器(IL)分离一阶边带和中心载波,一阶边带经过光电(O/E)检测器拍频产生两倍频于射频频率的毫米波,而中心载波可以作为上行链路载波重新利用。理论分析了该毫米波的传输性能,研究发现由于色散导致两个一阶边带时延不同,码元的占空比会随着传输距离的增加而减小,将限制毫米波的最大传输距离;实验中采用频率为20 GHz射频信号产生频率为40 GHz的毫米波,速率为2.5 Gbit/s的非归零(NRZ)码作为下行链路数据,经过20 km色散光纤传输后下行链路的功率代价为0.2 dBm。     

A Novel Scheme for Seamless Integration of ROF With Centralized Lightwave OFDM-WDM-PON System

We have experimentally demonstrated a novel transmission system for seamless integration of ROF with centralized lightwave OFDM-WDM-PON based on an integrated external modulator. At the one of two arms of the integrated external modulator, the optical carrier suppression (OCS) is realized to generate 40–GHz optical millimeter-wave (mm-wave) and up-converted baseband data signal as wireless signal. In another arm of the integrated external modulator, 16 quadrature amplitude modulation intensity-modulated OFDM signals at 10 Gbit/s are used for downstream transmission as wired signal based on double sideband modulation. By using one intensity modulator (IM), the downstream RF OFDM signal is remodulated for upstream on–off keying (OOK) data at 2.5 Gbit/s because of its downstream RZ shape waveform. The 10-Gbit/s wired signal, 2.5-Gbit/s wireless signal, and 2.5-Gbit/s upstream signal have been transmitted over 20-km single mode fiber (SMF) successfully.      

IF signal transmission at 60 GHz-band using direct modulation of atwo-mode locked Fabry-Perot slave laser

We demonstrate the fiber transmission of an IF signal at 60 GHz-band using a two-mode injection-locked Fabry-Perot slave laser for fiber radio systems. The IF signal can be generated by the CW modulation of the slave laser without using an optical intensity-modulator. We confirm the fast response of the modulated slave laser and a 77 dB dynamic range for signal modulation against third-order distortion. The IF signals power deviation caused by fiber dispersion is also investigated     

Key technologies and system design for various radio over fiber applications

Key technologies and new system designs for various radio over fiber (RoF) applications are proposed and demonstrated. For ultrawideband (UWB) over fiber applications, several UWB pulses generation and distribution methods are carried out. Different kinds of UWB pulses are generated based on cross-polarization modulation methods. For millimeter-wave (mm-wave) wireless applications, a 32 GHz RoF system is demonstrated with microwave frequency sextupling by optical methods. After 20 km SMF transmission, the power penalty of 2.5 Gbit/s downlink service is less than 0.15 dB. It is also suitable to apply dense wavelength division multiplexing (DWDM) technology to RoF system to support numerous base stations (BSs).     

基于强度调制和布里渊效应的六倍频可调毫米波信号产生

提出了一种新型的基于马赫-曾德尔调制器(MZM)和布里渊效应实现六倍频可调毫米波信号输出的方法。在本方案中,先调节MZM的直流偏置,抑制偶数边带,留下奇数边带;经过大功率掺Er3+光纤放大器(EDFA)放大之后,使两个一阶边带的功率达到布里渊阈值之上,然后采用了25km的单模光纤(SMF)作为布里渊介质,滤除一阶边带,留下三阶边带;最后经过EDFA放大和光电探测器(PD)光电转换得到六倍频的毫米波信号。因为布里渊边带滤波是窄带滤波,与波长无关,故本系统可以实现波长无关的微波信号产生。     

Highly stabilized millimeter-wave generation by using fiber-opticfrequency-tunable comb generator

A novel optical generation and transport technique for millimeter-wave (mm-wave) signals by using the fiber-optic frequency-tunable comb generator having a discrete emission spectrum as the light source is proposed. 60 GHz mm-wave signal generation and transmission over a 108 km-long optical fiber link at λ=1560 nm is demonstrated. Excellent stability of both the frequency and amplitude of the mm-wave carrier is attained, so that the 3 dB linewidth is less than 0.3 kHz and the variance of the amplitude fluctuation is 0.07 dB. The advantages include tunability of the carrier frequency, handling ease, and no need for a high-speed external light modulator     

Fiber Dispersion Influence on Transmission of the Optical Millimeter-Waves Generated Using LN-MZM Intensity Modulation

We have theoretically investigated the transmission performance of the optical millimeter-waves (mm-waves) generated using intensity modulation via a Mach-Zehnder modulator, with the double and single sidebands (DSB and SSB) and optical carrier suppression (OCS) schemes. According to our theoretical analysis, fiber chromatic dispersion leads to fading effect and time shifting of the codes; therefore, signals are greatly degraded. Of all signals, DSB optical mm-wave suffers from both the fading effect and the time shifting of the codes. However, the optical mm-waves generated by SSB and OCS schemes are immune to the fading effect, while the time shifting of the codes limits their transmission distance. Experimental and simulation results confirm the theoretical analysis.     

基于单边带调制的直接探测光OFDM-RoF系统研究

研究基于单边带调制(SSB)的直接探测光正交频分复用-光载射频(OFDM-RoF)系统的性能。10Gbit/s的二进制数据信号经过QAM符号映射和OFDM调制后,与10GHz射频信号混频并驱动双电极LiNbO3马赫-曾德尔调制器(LN-MZM)产生SSB-OFDM信号,调制信号通过光纤传输至基站,进行直接探测转换为毫米波电信号后再无线发送到用户端。仿真结果证实,OFDMRoF系统在4QAM和16QAM两种调制格式下的EVM都满足FEC的要求。同时,理论分析并仿真验证存在一个最佳调制指数可以使信号传输性能达到最佳,并且最佳调制指数与光纤长度无关。     

New progress of mm-wave radio-over-fiber system based on OFM

This paper presents an overview on new progresses-of millimeter wave (mm-wave) radio-over-fiber (RoF) system based on mm-wave generation by optical frequency multiplication (OFM), including gen-eration of high-order optical side modes by optical modulation using dual-drive Mach-Zehnder modulator (DD-MZM) and enhancement of high-order optical side mode induced by selective amplification due to stimulated Brillouin scattering (SBS). The paper describes OFM by using DD-MZM in principle and verifies it in an experimental bidirectional 40GHz RoF system. SBS amplification enhances the generated information-bearing mm-wave in downlink and also helps in producing a pure reference mm-wave for radio frequency-intermediate frequency (RF-IF) down-conversion in uplink. These efforts pushed the OFM technology of mm-RoF systems to achieve more and more feasibility and cost-effectiveness.     

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.      

用IQ调制器产生载波抑制单边带信号的研究

载波抑制单边带调制是一种特殊的幅度调制形式,它将载波和另一个边带抑制,提高频带利用率,增加了光纤的传输容量。并可有效抑制色散,延长信号的传输距离。被广泛应用于长距离高频微波ROF系统中。文中详细分析了利用商用铌酸锂调制器产生载波抑制单边带信号的原理,并据此分析,搭建了试验系统,分别产生了±1阶(即长波方向和短波方向)的载波抑制单边带信号。     

Wired and single sideband wireless service based on a single optical modulator

In order to provide more flexible and convenient service for users in the hybrid transmission network,a novel system using a single optical modulator to provide wired and single side band (SSB) wireless signal was proposed.By combining the application of dual-polarization binary phase shift keying modulator (DP-BPSK),phase shifter and other devices,wired and SSB wireless signals were directly generated to suppress the walk-off effect caused by dispersion,and the effective transmission of 5 Gbit/s SSB wireless signal carried on 40 GHz millimeter wave and 10 Gbit/s wired signal over 65 km single-mode fiber (SMF) were successfully achieved.The experiments show that the application of polarization multiplexing technology and optical subcarrier multiplexing technology can make the signal have a greater improvement in transmission rate and performance,and play an important role in the future broadband communication network.     

Impact of Nonlinear Transfer Function and Imperfect Splitting Ratio of MZM on Optical Up-Conversion Employing Double Sideband With Carrier Suppression Modulation

Generation of optical millimeter-wave (mm-wave) signal using a Mach–Zehnder modulator (MZM) based on double-sideband (DSB), single-sideband (SSB), and double-sideband with carrier suppression (DSBCS) modulation schemes have been demonstrated for various applications, such as broadband wireless signals or optical up-conversion for wavelength-division-multiplexing (WDM) radio-over-fiber (RoF) network, wideband surveillance, spread spectrum, and software-defined radio. Among these schemes, DSBCS modulation offers the best receiver sensitivity, lowest spectral occupancy, the least stringent requirement of electrical bandwidth, and the smallest receiving power penalty after long transmission distance. Nonetheless, the inherent nonlinear E/O (electrical/optical) conversion response of a MZM is such that the signal quality of the optical mm-wave suffers. Fabrication tolerances make a balanced 50/50 splitting ratio of the MZM's y-splitter particularly difficult to achieve. As a result, imbalanced MZMs have a finite extinction ratio (ER) and degrade the optical carrier suppression ratio (OCSR) using DSBCS modulation. In this paper, the effect of the MZM nonlinearity and imbalanced y-splitter on optical mm-wave generation by DSBCS modulation is theoretically and experimentally investigated. A novel approach with better performance and greater cost-effectiveness than dual-electrode MZM (DD-MZM) is presented to realize a DSBCS modulation scheme based on a single-electrode MZM (SD-MZM).      

Transmission Performance of the Optical Millimeter-wave Up-conversion Link Using a Phase Modulator

Numerically analyzed is the transmission performance of the optical millimeter(mm)-wave generated by frequency up-conversion via a phase modulator along the dispersive fiber.60 GHz mm-wave sub-carrier(SC)signals can be obtained after fiber transmission,simultaneously,the phase-modulated signals can be converted to the intensity-modulated ones.The numerical results show that the optical mm-wave at fading loops has better performance,and the eye diagram still keeps open when optical mm-wave signal is transmit...     

Millimeter-wave broad-band fiber-wireless system incorporating baseband data transmission over fiber and remote LO delivery

We present the first demonstration of a millimeter-wave (mm-wave) broadband fiber-wireless system which incorporates baseband data transmission in both the downstream (622 Mb/s) and upstream (155 Mb/s) directions. The local oscillator (LO) required at the remote antenna base station for up- and downconversion to/from the mm-wave radio frequency (RF) is delivered remotely via a modulation scheme that is tolerant to the effects of fiber chromatic dispersion on the detected LO carrier power. The technique employs a single dual electrode modulator located at the central office (CO) and the data and an RF signal at a frequency equal to half the LO frequency, are applied simultaneously to the device. The modulation scheme was optimized as a function of the modulator operating conditions. Simultaneous bidirectional radio transmission in the mm-wave fiber-wireless network was implemented using specially designed mm-wave diplexers located at the base station (BS) and customer unit, and a single Ka-band printed antenna array at the BS operating simultaneously in transmit and receive mode. Error-free data transmission was demonstrated for both down(34.8 GHz) and uplinks (37.5 GHz) after 20 km of single-mode optical fiber and a bit error rate (BER) of 10/sup -6/ was achieved after the inclusion of a 2-m radio link.     

Novel full-duplex SSB WDM-RoF system with SLM technique for decreasing PAPR

A novel full-duplex single-sideband (SSB) wavelength division multiplexing radio over fiber (WDM-RoF) system with selected mapping (SLM) technique for decreasing peak-to-average power ratio (PAPR) is proposed in this paper. At the central office (CO), the generated SSB signal carrying 10 Gbit/s 16-ary quadrature amplitude modulation orthogonal frequency division multiplexing (16QAM-OFDM) downstream signal with SLM technique is sent to the base station, and 60 GHz SSB optical signal carrying 10 Gbit/s 16QAM-OFDM upstream signal is sent back to CO utilizing the wavelength-reuse technology. Simulation results show the proposed method for PAPR reduction can effectively improve the sensitivity of receiver, and the power penalty of the 16QAM-OFDM downlink (uplink) signal is about 2 dB (3 dB) at BER of 1×10-3 after 42 km standard single-mode fiber (SSMF) transmission.     

60-GHz-band full-duplex radio-on-fiber system using two-RF-portelectroabsorption transceiver

A full-duplex radio-on-fiber system using a newly developed 60-GHz-band optical transceiver is investigated. We fabricated a 60-GHz-band two-radio-frequency (RF)-port electroabsorption transceiver (EAT) module, which is the first developed 60-GHz-band optical transceiver in the world. The EAT module has individual RF input and output ports, each with impedance-matching circuits that enhance modulation and detection efficiencies near 60 GHz. A radio-on-fiber testbed adopting the EAT has an advantage that a base station becomes the simplest configuration, which basically consists of only the 60-GHz-band EAT. Using the radio-on-fiber testbed, the simultaneous transmission of 59.6-GHz (downlink) and 60.0-GHz (uplink) signals with data of 156 Mb/s is experimentally demonstrated     

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 scheme to implement duplex 60-GHz radio-over-fiber link with 20-GHz double-sideband optical millimeter-wave transmitted along the fiber

A duplex radio-over-fiber (RoF) link with a novel scheme to generate 60-GHz millimeter (mm)-wave using 20 GHz double sideband (DSB) optical mm-wave with signal carried only by its optical carrier is investigated. In the RoF downlink, the modulation frequency to generate the DSB optical mm-wave is reduced greatly. The theoretical analysis and numerical simulation show that this scheme cannot only eliminate the code form distortion caused by the time shifting of the sidebands, but also reduce the influence of the fading effect as the DSB optical mm-wave signal is transmitted along the fiber. Based on the scheme, the duplex RoF link with the frequency up- (down-) conversion of the down- (up-) link mm-wave signal is built and the uplink transmission performance is analyzed theoretically.     

Dispersion-Tolerant Millimeter-Wave Photonic Link Using Polarization-Dependent Modulation

A novel technique to modulate one carrier in a dual-carrier millimeter-wave (mm-wave) photonic system is presented and experimentally evaluated. The technique utilizes the polarization dependence of an optical phase modulator and the properties of optical heterodyning and is demonstrated for both amplitude- and phase-modulated mm-wave signal outputs. Experimental verification of the technique is presented with transmission of up to 2.5-Gb/s nonreturn-to-zero data, multilevel quadratic-amplitude modulation, and IEEE 802.11a WLAN data signals on a 40-GHz carrier over optical fiber and wireless transmission. The tolerance for fiber dispersion is investigated, and penalty-free transmission over 44 km is verified. The linearity of the system is evaluated by measuring the spurious-free dynamic range. [All rights reserved Elsevier].