Radio-over-fiber AM-to-FM upconversion using an optically injected semiconductor laser

A radio-over-fiber system uses light to carry a microwave subcarrier on optical fibers. The microwave is usually frequency modulated for wireless broadcasting. A conventional optical communication system usually operates at the baseband with amplitude modulation. The interface of the two systems thus needs an upconversion from the baseband to the microwave band with AM-to-FM transformation. An all-optical solution employing an optically injected semiconductor laser is investigated. The laser is operated in a dynamic state, where its intensity oscillates at a microwave frequency that varies with the injection strength. When the injection carries AM data, the microwave is frequency modulated accordingly. We demonstrate optical conversion from an OC-12 622-Mbps AM baseband signal to the corresponding FM microwave signal. The microwave is centered at 15.90 GHz. A bit-error rate of less than 10(-9) is measured.     

Optical beat interference-tolerant 60-km WDM/SCM-PON link based on reflective-SOA using amplified spontaneous emission and wavelength conversion

An optical beat interference (OBI)-resistant 60-km wavelength division multiplexed/subcarrier multiplexing-passive optical network (WDM/SCM-PON) is proposed. This scheme disperses OBI-noises using broadband amplified spontaneous emission (ASE)-light as an optical source for optical network unit. An uplink transmission is executed using a cross gain modulated light by ASE source with data in a local exchange. Error free transmissions of up and downlink are experimentally accomplished after 60-km optical transmission. The impact of Rayleigh backscattering noise on 100-Mb/s uplink signal is also investigated.     

Bidirectional colorless wired and wireless WDM-PON with improved dispersion tolerance for radio over fiber

We propose and demonstrate a bidirectional transmission, hybrid wired and wireless access network based on subcarrier modulation (SCM) techniques. The scheme simultaneously enables the dispersion-tolerant transmission of millimeter (mm)-wave signals for use in wireless access networks, downstream baseband signals for optical wired access networks, and optical continuous-wave (CW) carriers for use in upstream data remodulations. Error-free transmissions through a 25-km length of single mode fiber (SMF) for both the downstream baseband and the remodulated upstream signals are confirmed by bit-error-rate (BER) measurements. The dispersion tolerance of the radio-over-fiber (RoF) signal is assessed using numerical simulations.     

The influence of fiber dispersion on the code form of the optical mm-wave signal generated by single sideband intensity-modulation

We have theoretically investigated the transmission performance of the optical mm-wave generation by using an external modulator based on single sideband (SSB) intensity modulation. Though the SSB millimeter (mm)-wave can immune the fading effect, the baseband signals with a high bit rate are degraded greatly after transmission along fiber. The main reason is that the fiber dispersion causes the time shift of the code edges; therefore the maximum transmission distance of the baseband signals is limited. The experimental and simulation results agree well with our theoretical analysis. We also propose a novel scheme to extend the transmission distance. In this novel scheme, the data signals are modulated only onto one of the two optical carriers; hence the shift of the code edges in the down-converted signals after transmission is eliminated.     

Bidirectional WDM-PON architecture using a reflective filter and cyclic AWG

We proposed and demonstrated a bidirectional SCM-WDM PON using a reflective filter and cyclic AWG where up/downlink data could be provided using a single optical source. In the proposed scheme, the signal for downstream was modulated by a single CW laser diode and remodulated in the optical network unit as an upstream, the proposed WDM-PON scheme can offer the SCM signal for broadcasting service. In this paper, 1 Gb/s signals both for up- and downstream were demonstrated in 10 km bidirectional optical fiber link.     

All-fiber incoherent frequency-to-time mapping method for microwave signal generation with baseband transmission and multicasting support

We present a proof-of-principle experiment for achieving simultaneous distribution of baseband radio-frequency data and up-conversion with broadcasting support over a passive optical network. The technique is based on an incoherent frequency-to-time mapping method for pulse shaping. Specifically, we synthesize the spectral density function of sliced ASE noise from an EDFA with a periodic Mach–Zehnder fiber interferometer optical filter. By using external intensity modulation combined with propagation in an optical fiber, after photodetection, the resultant averaged temporal pulse profile resembles the shape of the incoherent source. The photodetected signal contains both the baseband data and an up-frequency converted copy with central wavelength for the microwave carrier into the ultra-wideband range and tuning capability by selection of the fiber length.     

基于综合光学调制技术的光纤无线双向通信系统设计

提出并研究了一种使用单光源的光纤无线双向传输系统.该系统只需在中心站配置一个可调谐激光器,以产生频率恒定的激光光源,通过综合光学调制（频率调制、强度调制）技术将基带信号调制到光载波上,最终形成60 GHz毫米波下行信号|同时,相同的光载波在基站被重用,作为上行链路传输光源.系统结合光载波重用技术和综合调制技术特点,合理利用资源,基站结构更为简化.仿真结果表明,该系统可以将速率达2.5 Gbit/s的数据在单模光纤中双向传输20 km,功率代价小于0.5 dB,相对已有的技术方案,该传输系统在传输功率、传输距离、传输性能方面具有明显优势.     

A long-reach WDM passive optical network enabling broadcasting service with centralized light source

We propose a long-reach wavelength-division-multiplexed (WDM) passive optical network (PON) to provide conventional point-to-point (P2P) data and downstream broadcasting service simultaneously by superimposing, for each WDM channel, the differential-phase-shift-keying (DPSK) broadcasting signal with the subcarrier multiplexing (SCM) modulated downstream P2P signal, at the optical line terminal (OLT). In the optical network units (ONUs), by re-modulating part of the downstream signal with a reflective semiconductor optical amplifier (RSOA), we realize color-less ONUs for upstream data transmission. The proposed scheme is numerically verified with a 5 Gb/s downstream P2P signal and broadcasting services, as well as 2.5 Gb/s upstream data through a 60 km bidirectional fiber link. In particular, the influence of the downstream lightwave's optical carrier–subcarrier ratio (OCSR) on the system performance is also investigated.     

一种改进的双边带调制产生光毫米波的方案

提出了应用于光纤无线通信系统中一种改进的双边带调制产生光毫米波方案。在中心站采用强度调制将射频信号调制到光载波上产生一个双边带信号,滤掉中心载波后,利用光交叉复用器把双边带信号的上下边带模分开,将数据速率为2.5Gbit/s的基带信号调制到下边带模后,再与未调信号耦合后产生光毫米波,然后通过单模光纤传输至基站,在基站经过光电转换后产生电毫米波信号。从理论上对该毫米波的色散特性进行了分析,发现毫米波的接收功率不会周期的衰减。同时通过实验研究表明,下行链路信号通过光纤能传输50km而不需要色散补偿,功率代价小于1dBm。因此,该方法产生的光毫米波能有效克服光纤色散引起的信号时延而导致的基带信号退化,适合于远距离传输。     

Multi-functional fibre-optic microwave links

The multi-functionality of microwave links based on remote heterodyne detection of signals from a dual-frequency laser transmitter is discussed and experimentally demonstrated in this paper. Typically, direct detection in conjunction with optical intensity modulation is used to implement fibre-optic microwave links. The resulting links are inherently transparent and mainly used for signal transmission. As opposed to direct detection links, remote heterodyne detection links can directly perform functionalities such as modulation, frequency conversion, and transparent signal recovery in addition to signal transmission. All three functionalities are presented and experimentally demonstrated with a remote heterodyne detection link based on a dual-frequency laser transmitter with two offset phase locked semiconductor lasers. In the modulating link a 1Gbit/s baseband signal is QPSK modulated onto a 9GHz RF carrier. The frequency converting link demonstrates up-conversion of a 100Mbit/s PSK signal from a 2GHz carrier to a 9GHz carrier with penalty-free transmission over 25km of optical fibre. Finally, the transparent signal recovering link transmits a standard FM video 7.6GHz radio-link signal over 25km of optical fibre without measurable distortion.     

Cost-effective and dispersion-tolerant cascade modulation for millimeter-wave-over-fiber applications

In millimeter-wave-over-fiber (MWoF) feeder systems, the received millimeter-wave signals at the remote antennas (RAs) can suffer from signal fading by chromatic dispersion of optical fiber. This can be substantially mitigated by Mach-Zehnder modulator (MZM) based photonic up-conversion technique. In this technique, the data signals at intermediate frequency (IF) are frequency up-converted to millimeter-wave frequency by an MZM biased at its transmission null point. However, this scheme requires a costly, high-speed MZM, which will hinder the widespread of this technique for cost-sensitive MWoF applications. Hence, we propose and demonstrate a cost-effective way of reducing the cost of MWoF optical transmitters based on photonic up-conversion technique. We employ a dual wavelength source composed of a directly modulated laser and a polarimetric filter. This source is used to generate a millimeter-wave tone signal and to frequency up-convert the IF data signals to millimeter-wave frequency. The dual wavelength source is also shared with numerous RAs for further cost reduction. Our experimental demonstration performed with 30 Msymbol/s 16-quadrature amplitude modulation signals shows that we can transmit the 20 GHz millimeter-wave signals over 25 km standard single-mode fiber without any transmission penalty.     

Control packet signaling mechanism using electronic code division multiple access for packet-based networks

We propose and experimentally demonstrate the feasibility of a control packet signaling technique using electronic code division multiple access for a wavelength division multiplexing packet-based network, whereby each wavelength channel is assigned a unique electronic code based label on a radio frequency subcarrier. Such a technique allows each wavelength channel to be electronically identified without requiring the use of a WDM demultiplexer. We experimentally demonstrate this technique with two wavelength channels each with 1.25 Gb/s baseband payload data and 10 Mb/s header coded onto an electronic code at 160 Mb/s. A performance study of the electronic code division multiple access based control signaling scheme in a wavelength division multiplexed packet-based access network is also performed in terms of the required power budget to monitor the electronic code division multiple access control signals in the presence of several sources of noise for error-free transmission of both payload data and electronic code division multiple access based control signals. It is shown that the modulation depth of each signal impacts the amount of required optical tap power. As the modulation depth of the electronic code division multiple access based control signal is increased, the required optical tap power is reduced. However, this increases the bit-error-rate for the payload data. Therefore, there lies a maximum and a minimum of the required tap optical power for the successful recovery of both signals. The lower bound of this range is usually determined by the successful recovery of electronic code division multiple access based control signal while the upper bound is determined by the successful recovery of payload data. The required optical tap power is analyzed for different transmission bit rates of the payload data for various receiver architecture scenarios without an optical amplifier at the receiver. The scalability analyses were repeated with an optical amplifier placed in the receiver terminal of the network. The resulting optical tap power that is required for the successful monitoring of the electronic code division multiple access based control signals are compared with that of the case without the amplifier.     

Full-duplex radio-over-fiber system based on a modified single-side band modulation

A full-duplex radio-over-fiber system based on a modified single-sideband using external modulator is proposed and demonstrated. At the central station, a CW lightwave is intensity-modulated by a RF signal to generate a DSB signal. After the central carrier and the two first-order sidebands are separated by a FBG, the central carrier is modulated with a baseband data at 2.5 Gbit/s. Then, it is recombined with the un-modulated first-order sidebands to generate optical millimeter-wave by an optical coupler with a certain coupling coefficient and transmitted to the base station over single-mode fiber. The central carrier and one of the first-order sidebands are beaten to generate the mm-wave when they are detected by an optical receiver. Another first sideband is reused as carrier for uplink connection. The dispersion performance of the generated mm-wave is theoretically analyzed; one can see that the effect of dispersion and requirement of the optical power are reduced. The PIN-PD can avoid working in a high-DC saturation range which may distort the RF components and depress the responsibility of the detector. The stimulant results show that the system can reduce the effect of dispersion effectively, and immune the fading effect and the walking-off signals. It is suitable for a long distance transmission.     

Alternative Wired and 60-GHz Wireless Full Duplex Access Based on a Polarization Orthogonal Dual-Tone Optical Millimeter-Wave Signal

Abstract

A novel full duplex fiber wireless link providing alternative wired and 60-GHz wireless access is proposed based on a polarization orthogonal dual-tone optical millimeter-wave signal. In a hybrid optical network unit, the downlink optical signal can be decomposed as a single-sideband optical millimeter-wave signal (baseband optical signal) for wireless (wired) access by a polarization controller and polarization beam splitter. The uplink optical carrier abstracted from the downlink optical signal makes the hybrid optical network unit free from the optical source. The simulation results show that both downlinks and uplinks for either wired or wireless access can maintain quite good performance over 60 km of fiber.     

一种基于相干检测的双向输出信号频率可选的光纤无线系统

提出了一种单光源、双向输出信号频率可选的光纤无线系统,该系统在单光源条件下,利用相干检测技术、数字信号处理技术,结合并行相位调制器以及波长选择开关结构,在上下行链路实现基带信号、多个毫米波信号输出.仿真验证表明,针对20Gbit/s 16-QAM调制信号,经30km光纤传输,系统下行输出信号频率实现0~60GHz可选,其传输最小矢量误差为6.53%(0GHz)~7.61%(60GHz);上行输出信号频率实现0~120GHz可选,其传输最小矢量误差为6.89%(0GHz)~8.30%(120GHz).理论分析和仿真结果表明,该系统双向链路均可实现频率可选的信号输出,且双向传输具有较好的性能表现.     

基于FPGA的PPM调制可见光图像传输系统

利用FPGA(field-programmable gate array, 现场可编程门阵列)为主控芯片，实现了5 Mbit/s的2-PPM(pulse position modulation, 脉冲位置调制)调制可见光图像传输系统。整个系统分为发射端与接收端两大模块，全部由FPGA实现。将处理好的图片信号由上位机通过串口发送到FPGA中，经过调制转换为2-PPM信号，并设计了信号传输数据帧格式，然后调制到红光LED(light emitting diode)上并发送出来；在接收端，根据数据帧格式完成了数据信号的同步和解调，并将解调后恢复的图像在液晶屏上显示出来。实验证明该系统可以实现可见光图像信号的传输。     

Optical millimeter-wave generation and transmission system for 1.25 Gbit/s downstream link using a gain switched laser

In this paper, we propose a novel and cost effective system for optical millimeter-wave (mm-wave) generation and transmission of downstream data based on a gain switched laser (GSL). The GSL produces an optical comb spectrum that can be appropriately filtered to generate two optical sidebands spaced by more than 4 times the repetition rate of the GSL. These sidebands are modulated by baseband data and then transmitted via optical fiber to the remote antenna unit (RAU). At the RAU, the two sidebands are heterodyned using a photodetector to generate the electrical modulated mm-wave signal, before demodulation using self mixing. We demonstrate the distribution of 1.25 Gbit/s data OOK modulated onto a 60 GHz carrier, similar to that used in the IEEE 802.15.3c draft standard, over fiber lengths up to 62 km.     

Gigabit-converged wired and wireless networks for simultaneous multi-services transmission

A novel architecture of converged radio-over-fiber(RoF) and wavelength division multiplexed passive optical network(WDM-PON) system,namely RoF-WDM-PON,is demonstrated.20-GHz 1-Gb/s radio frequency(RF) signals and 1-Gb/s baseband(BB) signals are simultaneously generated and transmitted using optical carrier suppression(OCS) modulation techniques.The proposed scheme is compatible with the conventional RoF and PON system.25-km single-mode fiber(SMF) transmission is successfully achieved.     

一种新型基于并行光传输的HDMI线缆的研制

 介绍了一款基于并行光纤通信技术的高清视频信号(high-definition multimedia interface, HDMI）传输线缆的研制技术方案。这种新型HDMI线缆采用垂直腔面发射激光器(vertical cavity surface emitting laser, VCSEL）阵列作为发射端,光电探测器（photodiode, PD）阵列作为接收端,两者之间采用多模光纤阵列互连,通过将电信号转变为光信号传输解决了铜缆损耗对电信号传输速率和传输距离的限制。与铜缆HDMI线相比,这种新型HDMI线能够以4信道×3.4Gbps的传输速率实现长达300m的传输距离,为当前高清视频信号和下一代超高清视频信号远距离传输提供了可行的技术方案。     

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.