240 GHz active modelocked laser diode

A 240 GHz optical millimetre-wave (mm-wave) signal is generated by an active modelocked laser diode (MLLD) integrated with a high-mesa electroabsorption modulator. The linewidth of the generated signal is less than 10 Hz. A -11 dBm mm-wave signal at 240 GHz was also generated using the active MLLD and a uni-travelling-carrier photodiode.     

120-GHz-band millimeter-wave photonic wireless link for 10-Gb/s data transmission

A 120-GHz-band wireless link that uses millimeter-wave (MMW) photonic techniques was developed. The output power and noise characteristics of 120-GHz-band MMWs generated by converting a 125-GHz optical subcarrier signal were evaluated. It was then shown that the noise characteristics of the 125-GHz signal generated with these photonic technologies is sufficient for 10-Gb/s data transmission. We constructed a compact 120-GHz-band wireless link system, and evaluated its data transmission characteristics. This system achieved error-free transmission of OC-192 and 10-GbE signals over a distance of more than 200 m with a received power of below -30 dBm.     

Fiber-optic millimeter-wave downlink system using 60 GHz-bandexternal modulation

In this paper, a fiber-optic millimeter-wave (mm-wave) downlink system using 60 GHz-band external modulation is investigated. We prepare the fiber-optic 60 GHz-band mm-wave downlink testbed. It consists of an optical modulation section with a mm-wave signal generator, an optical single sideband (SSB) filter, a standard single-mode fiber (SMF), an optical detection section with a 60 GHz-band radio transmitter and a 60 GHz-band radio receiver. To modulate the laser output with 60 GHz-band mm-wave signals directly, a specially designed electro-absorption modulator with high-efficiency at around 60 GHz is used. The use of this modulator makes the simpler system configuration possible. Using the downlink testbed, the 5 m-long free-space propagation of subcarrier multiplexed 156 Mb/s-DPSK 60 GHz-band mm-wave signals recovered by optical direct detection is successfully demonstrated. The transmission of the mm-wave signals over 85 km-long standard SMF is also successfully demonstrated, using an optical SSB filtering technique to overcome the fiber dispersion. The BER of 10^-9 is achievable at the optical received power of -7.0 dBm     

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。     

Cancellation of the signal fading for 60 GHz subcarrier multiplexedoptical DSB signal transmission in nondispersion shifted fiber usingmidway optical phase conjugation

In millimeter-wave (mm-wave) optical double sideband (DSB) signal transmission systems, the received radio frequency (RF) power fades periodically because of the group velocity dispersion (GVD) and the self-phase modulation (SPM) of optical fibers. In this paper, cancellation of the signal fading by using midway optical phase conjugation in mm-wave subcarrier multiplexed (SCM) optical DSB signal is analyzed. Fading-free 60 GHz mm-wave optical DSB signal transmission over 100 km-long nondispersion shifted single-mode fiber at 1550 nm by using a semiconductor optical amplifier (SOA) optical phase conjugator (OPC) in the midway of optical link is experimentally demonstrated for the first time. Finally, the degradation factor of the OPC system is also discussed     

基于相位调制器产生光毫米波的全双工光纤无线通信系统

提出并实验研究了一种基于相位调制器产生光毫米波信号的全双工光纤无线通信(RoF)系统。在中心站采用相位调制器结合滤波的方法产生重复频率为40GHz的载波抑制双边带毫米波信号,利用交叉复用器分离开毫米波信号的上下边带,其中的一个边带强度调制数据速率为2.5Gbit/s的下行基带信号,另一个边带被发送到基站调制上行传输的基带数据。该系统抗色散效果好,在经过40km标准单模光纤上/下行传输数据速率2.5Gbit/s的基带信号后,双向的传输功率代价都小于0.5dBm。在光纤无线通信系统中采用相位调制器结合滤波的方法产生光毫米波,同时基于波长重用技术再生上行光载波信号,可以简化中心站和基站配置,节约系统成本。     

60 GHz OCS mm-wave generation for ROF system based on saturated parametric amplification effect in HNLF

A novel approach to generate 60 GHz optical carrier suppression (OCS) millimeter-wave (mm-wave) signal based on the saturated optical parametric amplification (OPA) effect in high non-linear fiber (HNLF) is investigated. In the proposed system, the OPA effect occurs when the signal and pump with 30 GHz frequency interval are set into the high non-linear fiber. By controlling the length of HNLF, OPA effect saturates, and the pump power is delivered in a large extent to the signal and idler light, so a 60 GHz OCS mm-wave is generated. The system does not need high-speed external modulator, high-frequency vibration source or narrow-band filter, which greatly reduces the cost and improves the stability of the radio over fiber (ROF) system. Results show that the 10 Gb/s downstream signal can be transmitted with negligible power penalty.     

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.      

Full-Duplex 60-GHz RoF System With Optical Local Oscillating Carrier Distribution Scheme Based on FWM Effect in SOA

A full-duplex 60-GHz radio-over-fiber (RoF) system using novel optical local oscillating (LO) carrier distribution scheme to reduce the system cost and realize centralized management is proposed and experimentally demonstrated. In the proposed scheme, the optical LO carriers for producing remote electrical LO signals at the base stations (BSs) are generated together with the downlink RoF carriers at the central station (CS) via four-wave-mixing effect in semiconductor optical amplifier, and are then distributed to the BSs along with the downlink RoF signals. By down-converting the 60-GHz-band uplink signal with the remotely produced 60-GHz LO signal and reusing the optical LO carriers as the uplink optical source, only a cost-effective intermediate frequency modulator is required at each BS to transmit the uplink signal, which will dramatically reduce the whole system budget due to a large amount of BSs. Moreover, the operating frequency of each BS can be controlled remotely at the CS end to realize centralized management and convenient reconfiguration. Using the proposed scheme, 622-Mb/s signals for both directions are successfully transmitted over a 20-km single-mode fiber link and a 50-cm wireless channel with less than 0.1- and 0.2-dB power penalty for downlink and uplink, respectively.      

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     

Efficient generation of guided millimeter-wave power by photomixing

A 70-GHz bandwidth commercial photodiode has been coupled to W-band waveguide and used as a photomixing source from 75 to 170 GHz. Maximum power conversion efficiency of 1.8% was obtained at 75 GHz, where an optical input of +10 dBm yielded a nonsaturated millimeter-wave (mm-wave) power of -7.5 dBm. Optimizing the photomixer backshort tuning at individual frequencies showed that the mm-wave power decreased with frequency to a level of -30 dBm at 170 GHz. Fixed tuning allowed the generation of power across the full waveguide band from 75 to 110 GHz, with a variation within 5 dB across the majority of the band     

一种基于OPM和FBG滤波器的新型双工ROF系统

提出了一种采用光相位调制器(OPM)和光纤布 拉格光栅(FBG)滤波器实现的双向光纤无线通信(ROF)系统。在中心站,系统采用OPM和FBG滤波器产生抑制一阶边带的多边带光信号 ,而2.5Gbit/s 的下行链路信号只调制在中心光载波上同时经过光纤进行传输。在基站,未被调制的边带信 号用来重新调 制上行链路信号。建立了产生光载毫米波的理论模型,分析了光纤色散导致的相位影响,并 通过仿真实验 验证了系统的可行性。结果显示,经过60km光纤传输后,上、下行 链路信号的眼图都清晰可见,上行链 路功率代价小于0.2dB,下行链路功率代价小于1.8dB,系统具有较好的抗色散能力。     

A 1320 nm experimental optical phase-locked loop

An experimental balanced optical second-order phase-locked loop constructed using 1320 nm diode laser pumped miniature Nd:YAG lasers is discussed. The loop is stable and has a phase error of less than 1.8° when the received signal power is -65 dBm or more. The phase error appears to be dominated by the lasers' frequency noise as long as the signal power is more than -60 dBm     

A radio-over-fiber system with photonic generated 16QAM OFDM signals and wavelength reuse for upstream data connection

We have experimentally demonstrated a wavelength reuse scheme for up-link connection in a radio-over-fiber (ROF) system with photonics generated 2.5 Gbit/s 16QAM OFDM signals. In this architecture, 2.5 Gbit/s 16QAM OFDM signals are carried by the optical millimeter-wave (mm-wave) carriers which are generated with four times frequency of the local oscillator (LO) signal. The power penalties for both down- and up-stream signal delivery over 20 km fiber are less than 1 dB.     

一种产生OCS-DPSK光载毫米波的光纤无线系统

提出了一种产生载波抑制-差分相移键控(OCS-DPSK)光载毫米波的光纤无线系统。建立了OCS-DPSK光载毫米波的产生和传输链路模型,分析了光纤色散的影响,并通过仿真实验验证了系统的可行性。实验结果表明,重复频率为30GHz的OCS-DPSK光载毫米波调制2.5Gb/s基带信号经80km光纤传输后,眼图清晰可见,功率代价为3.7dB。     

An Experimental 50 Mb/s Fiber Optic PCM Repeater

An experimental repeater for amplification and regeneration of 50 Mb/s fiber-optical pulses has been built and tested. For the receiver either Si p-i-n or avalanche photodiodes are used in conjunction with a high impedance FET input amplifier. The high voltage for the avalanche photodiode is generated internally and controlled by the received signal. This AGC circuit is capable of compensating for temperature changes of the avalanche gain over the range of-40 - +60degC. The optical transmitter consists of either a GaAs light emitting diode or a GaA1As laser diode coupled to optical fibers and directly modulated by a current driver with 30 percent electrical efficiency. For 10^-9error rate, the required average optical signal power for a pseudorandom signal is p-i-n diode: -41.5 dBm; avalanche diode: -56.6 dBm. The optical output power into a fiber with 1 percent index difference is LED: -17 dBm; GaAlAs laser: 0 dBm. The repeater power requirement is about 2 W.     

Loop-Back Optical Heterodyne Technique for 1.0-Gb/s Data Transmission Over 60-GHz Radio-On-Fiber Uplink

An optical-heterodyne-detection method for a 60-GHz radio-on-fiber uplink is proposed and verified in this paper. The main point of this proposal is that all the functions needed for the optical heterodyne detection, i.e., the local/carrier light sources, the automatic frequency control of these light sources, and a polarization-diversity-detection circuit, are consolidated in one transmitting-side module to realize a simple system configuration. This proposal realizes an adequate optical uplink budget with low-cost optical receivers that consist of just one IF-band photodetector and one envelope detector. A 1.0-Gb/s transmission experiment over 10 km of single-mode fiber, which represents access-network transmission, is demonstrated using a 61.0-GHz amplitude-shift-keying signal as a 60 GHz-band uplink signal. A BER of less than 10-9 was obtained at an uplink SSB signal power of -40 dBm regardless of the polarization state of the optical uplink signal, and no significant dispersion-induced degradation was noted.     

毫米波生成系统中估算偏振模色散引起功率损耗的新方法(英文)

提出了一种在基于光外差法毫米波生成系统中估算由偏振膜色散(PMD)引起的功率损耗的新方法。不同于之前的方法,此方法将在光纤中传输的光载波视为一个随机过程,计算出了其自相关函数,并利用帕斯瓦尔定理估算功率损耗。利用此方法估算出在单模光纤(SMF)中由PMD引起的功率损耗,计算结果与之前方法得出的结果相似,证明了此方法的正确性。最后,直观地给出60 GHz信号在3个不同传输距离下由PMD引起的功率损耗。     

Measurement of nonlinear distortion in photodiodes

The 2nd-order nonlinear distortion of avalanche photodiodes (TIXL-55, C-20817) was found to be less than ?60 dB for an incident average optical power of ?20 dBm modulated at a peak depth of 75%. p-i-n photodiodes (HP 5082-4207) were found to have 2nd-order-distortion levels below the noise level. A method using three independent optical signal sources was employed in the measurement.     

On Frequency-Doubled Optical Millimeter-Wave Generation Technique Without Carrier Suppression for In-Building Wireless Over Fiber Applications

A novel optical millimeter-wave (mm-wave) generation scheme based on double-sideband phase modulation (DSB-PM) to achieve frequency doubling without suppressing the carrier is proposed. Theoretical analysis shows that the generated 60-GHz optical mm-wave can tolerant ${pm}$ 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. In addition, error-free transmission of 60-GHz mm-wave at 2.5 Gb/s is experimentally demonstrated over a combined distance of 3-m wireless with 21-dBm equivalent isotropically radiated power, and 250-m fiber to best emulate an in-building network environment. Dispersion effect on the frequency-doubled PM optical mm-wave without carrier suppression is also analyzed and experimentally studied by comparing the link performance over single-mode fiber (SMF-28) and dispersion-shifted fiber (DSF), respectively.