Reflective SOA-Based Bidirectional WDM-PON Sharing Optical Source for Up/Downlink Data and Broadcasting Transmission

We proposed and experimentally demonstrated the reflective semiconductor optical amplifier (RSOA)-based wavelength-division-multiplexed passive optical network (WDM-PON) scheme where not only up/downlink data services but also broadcasting service could be provided using a single optical source. In the proposed scheme, the digital signal and subcarrier multiplexing (SCM) signal for downstream were simultaneously modulated by a single distributed feedback laser diode and RSOA in optical network unit remodulated downstream source as an upstream. Without performance deterioration of digital signals both in up- and downstream, the proposed WDM-PON scheme can stably offer the SCM signal for broadcasting service. In the experiment, 1-Gb/s digital signals both for up- and downstream and 20-Mb/s SCM signal at 2.2 GHz for broadcasting were demonstrated in 10-km bidirectional link     

A self-seeded reflective SOA-based optical network unit for optical beat interference robust WDM/SCM-PON link

We have proposed and experimentally demonstrated a novel optical source configuration that uses a self-seeded reflective semiconductor optical amplifier (RSOA) as an optical network unit (ONU) in a wavelength division multiplexed/subcarrier multiplexing (SCM)-passive optical network (PON). A fiber Bragg grating (FBG) was used to obtain a single longitudinal mode of the RSOA. The proposed ONU configuration is simple, cost-effective, and effective regardless of wavelength allocation. Additionally, it would be robust for optical beat interference (OBI) noise. As the ONU is composed only of an RSOA and FBG, the self-seeded RSOA, due to the strong self-injection caused by the reflection of the FBG, has a broad optical spectrum. A self-homodyne apparatus method was performed in order to demonstrate the robustness of the self-seeded RSOA in OBI. To confirm the validity of the proposed scheme, a 16-quadrature amplitude modulation transmission experiment was performed in a 10-, 20-km optical access link with an SCM frequency of 1 GHz. An error vector magnitude of less than 4% for 2 Msps was successfully obtained through the transmission experiment.     

Wavelength-Tunable Laser for Signal Remodulation in WDM Access Networks Using DPSK Downlink and OOK Uplink

In this investigation, a simple wavelength-tunable laser based on a Fabry–PÉrot laser diode (FP-LD) and an erbium-doped fiber amplifier to serve as a downlink signal in a colorless wavelength-division-multiplexed passive optical network (PON) is proposed and experimentally demonstrated. The tuning range of the proposed laser is between 1529.48 and 1560.72 nm, and the output performance of proposed laser is discussed. Colorless operation is implemented by using an FP-LD and a reflective semiconductor optical amplifier in each optical network unit for uplink signal remodulation, respectively. In addition, error-free data signal remodulation using 10-Gb/s downlink differential phase-shift keying and 2.5-Gb/s uplink on–off keying is achieved in a 25-km reach PON.      

1.25-Gb/s bidirectional colorless WDM-PON based on RSOA using subcarrier detection and optical carrier suppression

A new architecture for bidirectional gigabit colorless wavelength division multiplexed-passive optical network system based on a reflective semiconductor optical amplifier is proposed. It uses techniques of both optical carrier suppression and subcarrier multiplexing. There is no impact of a downlink signal on an uplink one due to the wavelength reuse because a light from a single optical source is divided into two parts for uplink and downlink transmissions. One is modulated by a downlink signal and the other, which is transformed into two sidebands with a suppressed optical carrier, is utilized for an uplink transmission. An uplink data is recovered by subcarrier multiplexing technique. 1.25-Gb/s error-free transmissions of both uplink and downlink are demonstrated experimentally.     

Efficient Transmission Scheme for AWG-Based DWDM Millimeter-Wave Fiber-Radio Systems

We propose and demonstrate an upstream transmission scheme using a semiconductor optical amplifier (SOA) for arrayed waveguide grating (AWG)-based dense wavelength-division-multiplexed (DWDM) millimeter-wave fiber-radio systems and show improved link performance. In our scheme, unused optical carriers from the cyclic AWG in the downlink (DL) are tapped for uplink (UL) transmission. An SOA in conjunction with the AWG simultaneously amplifies the DL RF subcarriers and UL optical carrier, thus improving carrier-to-sideband ratio in the DL while also yielding an improved power budget for the UL. Our experimental results show that the proposed scheme can be a practical solution for future bidirectional wavelength interleaved DWDM transmission systems     

Bidirectional hybrid OFDM based Wireless-over-fiber transport system using reflective semiconductor amplifier and polarization multiplexing technique

In this paper, a bidirectional hybrid OFDM based Wireless-over-fiber architecture has been investigated and demonstrated to transmit 10 Gbps as well as 6.25 Gbps OFDM data for downlink transmission and 5 Gbps as well as 2.5 Gbps OFDM data for uplink transmission over 50-km single mode fiber (SMF) employing polarization multiplexing technique (POLMUX) at optical line terminal (OLT) and optical network unit (ONU). The POLMUX technique is exercised by polarization beam splitters and polarization beam combiners. Mach-Zehnder modulator and RSOA have been used for modulation at OLT and ONU respectively. Transmission performances are observed by constellation diagrams, EVM and BER values. For 10 Gbps, 6.25 Gbps down-link signal and 5 Gbps, 2.5 Gbps up-link signal the power penalty of 3 dBm, 2.3 dBm and 4 dBm, 3.2 dBm at a BER of 10⁻⁹ between back-to-back and over 50-km SMF plus 10-m and 5-m wireless link, are observed respectively. For 32-QAM < 10.5% EVM and for 16-QAM < 13% EVM are recorded. Our architecture is a prominent alternative, not only due to its have potential of both optical and wireless technology but also it is offers a powerful platform to communicate high data rates and support various type of future unforeseen applications and services.     

1.25 Gbit/s millimetre-wave band wired/wireless radio-over-fibre system based on RSOA using injection-locking effect

A new architecture for a millimetre-wave band radio-over-fibre system is proposed. Both optical carrier suppression and injection locking effect are used to simultaneously generate a 1.25 Gbit/s wired signal and a 63 GHz wireless one. Error-free transmissions (bit error rate of 10^-11) of downlink and uplink data are achieved to verify the proposed scheme. No impact of a downlink data transmission on an uplink one owing to the wavelength reuse is observed. It is checked that there is only the 2 dB power penalty of the uplink owing to the Rayleigh backscattering noise.     

A simple bidirectional hybrid optical link for alternatively providing wired and wireless accesses based on an optical phase modulator

A simple bidirectional hybrid optical link based on an optical phase modulator (OPM) is proposed to alternatively provide wired and wireless accesses. At the optical line terminal, only an OPM along with an optical band-pass filter is employed to generate the data-bearing four-tone downlink optical signal. At the hybrid optical network unit (HONU), both the downlink wired and wireless access electrical signals are simply generated based on the direct detection. Meanwhile, since the optical carrier for the uplink can be abstracted from the downlink, the HONU is free from the light source. To demonstrate the feasibility of our proposed scheme, a proof-of-concept bidirectional hybrid optical access link based on the OptiSystem platform is built. The simulation results indicate that after 30-km-long standard single-mode fiber transmission, the proposed bidirectional hybrid optical link still maintains good performance.     

Extended-reach WDM-PON based on CW supercontinuum light source for colorless FP-LD based OLT and RSOA-based ONUs

We investigate the benefits of using our proposed continuous-wave supercontinuum (CW SC) as a broadband wavelength-locking source for the implementation of extended-reach, colorless, wavelength division-multiplexed passive optical networks (WDM-PONs). More specifically, first, an extended reach WDM-PON architecture based on both the CW SC and our devised C-/L-band beam combiner is proposed, in which the optical line terminal (OLT) is based on Fabry–Pérot laser diodes (FP-LDs), whereas the optical network units (ONUs) are reflective semiconductor optical amplifiers (RSOAs). Second, a theoretical investigation on the maximum reach achievable with the proposed architecture is carried out considering Rayleigh backscattering noise and injection power limits. Only upstream signal performance is compared for the following four cases: (1) superluminescent diode (SLD) broadband source and FP-LD ONU, (2) SLD and RSOA, (3) CW SC and FP-LD, and (4) CW SC and RSOA. The combination of a CW SC injection source and RSOA-based ONUs is found to allow for the longest distance coverage. Finally, the feasibility of the proposed architecture is experimentally analyzed over a 60-km transmission fiber at 622 Mbit/s.     

A routing algorithm for reducing optical loss in photonic Networks-on-Chip

Driven by increase in automation, smart homes play an important role in today’s human life. This paper presents a new model for smart home technologies based on multi-device bidirectional visible light communication (VLC). For multiple devices and users, orthogonal code-based wavelength division (color beams) full-duplexed bidirectional VLC link is proposed. The color beams from RGB LEDs are utilized to transmit data and synchronize multi-device transmission. To enhance the performance of the proposed model, receiver diversity is also employed. Performance evaluation reveals that the proposed VLC-based model for smart homes is efficient with superior BER performance in a typical smart home environment except for the far corners. The maximum achievable data rate for each user up to four users is found to be 24 Mbps at both uplink and downlink transmissions.     

一种基于光载波抑制的ROF双工系统

为克服远距离光纤传输系统中色散效应的影响,研究了一种基于光载波抑制的单工ROF(光纤无线电)系统,并提出改进的双工ROF系统传输方案。在中心站,采用20GHz的射频信号将下行链路信号耦合至光载波抑制频段处,通过单模光纤传输50km至基站,并重复利用未调制边带传输上行链路信号。通过仿真得到的系统光谱图和误码率曲线表明:加入上行链路信号传输后,下行链路的光纤能量损耗降低,上、下行链路同时具有较好的抗色散能力。     

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 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.     

基于FBG和偏振复用的8倍频全双工RoF系统

为简化光载无线通信系统(RoF)中心站(CS)和基站(BS)结构,提出了一种基于光纤布拉格光栅(FBG)和偏振复用技术的8倍频全双工RoF系统方案。通过设置马赫-曾德尔调制器(MZM)偏置电压和射频驱动信号幅度保留部分主载波与偶数阶边带,再利用FBG将主载波与偶数阶边带分离。结合偏振复用技术将主载波和偶数阶边带复用到X和Y两个偏振方向上,其中抑制载波偶数阶边带用于下行链路数据传输,而主载波在BS站作为上行链路载波使用。理论推导了实现机理并进行了实验验证,结果表明当使用10 GHz射频驱动时可实现稳定的80 GHz光载毫米波信号,传输20 km后下行链路和上行链路功率代价仅为0.1和0.07 dB,表现出了较好的系统性能。     

基于双向中继和网络编码的NOMA网络性能分析

针对实际场景中存在的具有上下行双向传输任务的通信系统,本文提出了一种双向中继协作非正交多址接入(NOMA, non-orthogonal multiple access)传输方案,基于解码转发(DF, Decode and Forward)协议研究信号的上行和下行双向传输技术,与现有NOMA方案不同,本方案为近端用户分配较大的功率,利用网络编码(NC, network coding)原理在两个时隙内实现基站和用户之间的双向信息交换。进一步考虑不完美信道状态信息(CSI, Channel State Information)条件,分析系统的传输性能并推导了系统中断概率以及遍历和速率闭合表达式。仿真结果表明,在完美CSI和不完美CSI条件下,相比于现有文献所提方案、单向中继(OWR,One-Way Relay)和正交多址(OMA, Orthogonal Multiple Access)网络,本文所提方案有效降低了系统的传输中断概率,提高了系统的遍历和速率以及系统吞吐量。      

Utilization of self-injection Fabry–Perot laser diode for long-reach WDM-PON

In this investigation we propose and demonstrate a wavelength widely tunable laser source employing a self-injected Fabry–Perot laser diode (FP-LD) for long-reach wavelength-division-multiplexed passive optical network (WDM-PON). By using a tunable bandpass filter and an optical circulator inside the gain cavity, a stable and single-longitudinal-mode (SLM) laser output is achieved. Besides, the proposed laser sources are directly modulated at 2.5 Gb/s for both downlink and uplink transmissions of 85 km single mode fiber (SMF) in PON without dispersion compensation.     

Full-Duplex Radio-Over-Fiber System Using Phase-Modulated Downlink and Intensity-Modulated Uplink

We propose and demonstrate a full-duplex radio- over-fiber system employing a phase-modulated downlink and an intensity-modulated uplink over a single optical carrier. Each downlink and uplink is encoded with 200-Mb/s 16-quadrature amplitude modulation and a 100-Mb/s quadrature phase-shift keying signal carried in the 6-GHz band, respectively. The demonstration results show that the constraints on modulation index of the downlink signal as well as power budget of uplink signal can be relaxed thanks to the constant intensity of the phase-modulated downlink signal. The results also show the good error vector magnitude performance in both downlink and uplink signals after transmission over a 25-km fiber link. The effect of phase modulation to intensity modulation conversion of the downlink signal is also measured and evaluated for the scalability of the proposed technique.      

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.     

A novel duplex WDM-PON with DPSK modulated downstream and re-modulation of the downlink signal for OOK upstream

We experimentally demonstrate and analyze a 10 Gbit/s full duplex wavelength division multiplexing passive optical network (WDM-PON) system. A non-return-to-zero differential phase shift keying (NRZ-DPSK) modulation technique is first utilized for downlink direction, and then the downlink signal is re-modulated for the uplink direction using intensity modulation technique of on-off keying (OOK) with a data rate of 10 Gbit/s per channel. An effective colorless WDM-PON full duplex transmission system is achieved for the data rate of 10 Gbit/s per channel with a channel spacing of 60 GHz over the distance of 25 km with low power penalty.     

A full-duplex radio-over-fiber system based on optical carrier suppression and reuse

We have experimentally demonstrated a full-duplex radio-over-fiber system using a single light source at central station (CS). Optical carrier suppression modulation scheme was employed to generate 40-GHz optical millimeter wave and up-convert the baseband signal simultaneously at CS for downlink transmission while the same optical carrier was reused at base station for uplink connection. The bidirectional full-duplex 2.5-Gb/s data was successfully transmitted over 40-km standard single-mode fiber (SMF-28) for both upstream and downstream channels with less than 2-dB power penalty. This system shows simple cost-efficient configuration and good performance over long-distance delivery.