Widely tunable mode-locked laser diodes using optical disk filter

We present a scheme for generating high-repetition-rate mode-locked optical pulses within a wide wavelength-tuning range. This scheme utilizes an external-cavity laser configuration with a disk-shaped bandpass filter (disk filter), which is set in the external cavity. The disk filter can tune its transmission wavelength by rotating parallel to the external mirror. This simple wavelength-tuning scheme allows a short external cavity, which is necessary for generating high-repetition-rate optical pulses. This paper describes a preliminary experimental demonstration exhibiting 100%-modulated mode-locked pulses at 8 GHz in the 1535-1587-nm range     

采用两个级联外部调制器产生四倍频光载毫米波的光纤无线通信系统

研究了一种采用两个级联外部调制器基于光载波抑制原理产生四倍频毫米波的光纤无线通信(ROF)系统.在中心站利用电混频器产生副载波复用信号,通过第一个外部调制器产生两倍射频(RF)信号的光载毫米波信号,再通过第二个外部调制器产生四倍射频信号的光载毫米波.实验显示采用频率为10 GHz的射频信号源和2.5 Gbit/s的数据基带信号混频通过两个级联外部凋制器后产生毫米波的频率为40 GHz,并且在单模光纤中传输距离达20 km,功率代价小于2 dB.     

基于SOA的全光超宽带脉冲振幅调制方案

文章基于SOA(半导体光放大器)中的XGM(交叉增益调制)效应,提出一种实现全光UWB(超宽带)PAM(脉冲振幅调制)的方案.该方案只需要一个外部光源和一个SOA,结构简单,调制速率快.利用光通信系统软件OptiSystem对该方案进行仿真,分析了光源功率、SOA的注入电流和光源波长等系统参数对UWB PAM信号性能的...     

基于半导体光放大器的新型全光逻辑与门

为了实现基于半导体光放大器的全光逻辑与门,采用了在半导体光放大器构成的马赫-曾德尔干涉仪的基础上,注入外部连续光的方法。以半导体光放大器速率方程为基础,对设计方案进行了理论分析和仿真验证,取得了不同重复周期、不同脉冲宽度的光脉冲序列经过全光逻辑与门操作后的输出数据。结果表明,该方案能对传输速率为10Gbit/s或以下的信号进行正确与运算,同时,外光注入可以有效提高半导体光放大器信号处理速度。这一结果对基于半导体光放大器的全光逻辑的设计是有帮助的。     

Polarization-Insensitive All-Optical Upconversion for Seamless Integration Optical Core/Metro/Access Networks With ROF Systems Based on a Dual-Pump FWM Scheme

We have proposed and experimentally demonstrated a novel scheme to realize polarization-insensitive all-optical upconversion for single-channel or wavelength-division multiplexing signals. This scheme is based on the copolarized-pump four-wave mixing effect in nonlinear media. The copolarized pump is generated by using optical carrier suppression in an external intensity modulator; therefore, the two pumps are always parallel and phase locked. This scheme has some unique advantages for the integration between optical transport networks and radio-over-fiber systems, such as a polarization-insensitive, low-frequency bandwidth requirement for optical and electrical components, and high wavelength stability.      

Intrinsic optical bistability in `compensated' hetero-n-i-p-isuperlattices

A scheme for intrinsic optical bistability and switching in semiconductor heterostructures is proposed. The scheme does not require any external optical or electrical elements and possesses advantages of both the self-electrooptic effect device and doping superlattices. The switching properties of the proposed device are theoretically analyzed, and conditions for bistable operation are determined     

利用基带直调信号注入锁定半导体激光器产生全光上变频信号的研究

提出了一种将低速基带信号直调产生的宽谱信号,注入至用于上变频的分布反馈式半导体激光器(DFB-LD),利用调制信号光谱中的高阶分量对从激光器进行相位锁定,从而产生光学上变频信号的方法。对直调信号注入锁定DFB-LD产生光学上变频信号的机理进行了理论分析,完成了2.5Gb/s伪随机码基带信号通过直调并注入从激光器,分别产生了30,35,40GHz副载波频率的全光上变频信号的实验,并在时域和频域上,对上变频信号的特征进行了研究。该方案结构简单,无需高速外调制器及高频本振,具有集成潜力,理论上可产生更高载频(如60GHz),对目前的光-无线混合接入提供了一种可行的解决方案。     

Optically Injection-Locked 1.55-μ m VCSELs as Upstream Transmitters in WDM-PONs

The wavelength-division-multiplexed passive optical network is actively being developed to meet the ever-increasing bandwidth demands of end users in a cost-effective and future-proof manner. In this work, we propose a novel scheme that utilizes injection-locked 1.55-mum vertical-cavity surface-emitting lasers (VCSELs) for operation as low-cost, stable, directly modulated, and potentially uncooled upstream transmitters, whereby the injection-locking master source is furnished by modulated downstream signals. Our scheme eliminates the need for external injection-locking optical sources, external modulators, and wavelength stabilization circuitry. We show through experiments that the injection-locked VCSEL favors low injection powers and responds only strongly to the carrier but not the modulated data of the downstream signal, with good upstream transmission performance obtained over 25-km fiber     

Coherent optical frequency domain reflectometry usingphase-decorrelated reflected and reference lightwaves

We report a new scheme for coherent optical frequency domain reflectometry (C-OFDR) where the coherence length of the lightwaves does not limit the measureable fiber length. In this scheme, we use the beat spectrum which results when we mix reflected and reference lightwaves whose phases are not correlated. We demonstrated this scheme using a narrow-linewidth-lightwave source and an external electro-optical phase modulator. We measured Rayleigh backscattering and Fresnel reflections from a 30-Ion optical fiber, and achieved a spatial resolution of 5 m for two neighboring Fresnel reflectors located at the far end of the fiber. We estimated the expected spatial resolution and single-way dynamic range for our new scheme and show that it is capable of measuring long optical fibers with high-spatial resolution     

消除萨尼亚克光纤电流传感器振动干扰的光纤补偿环研究

与传统电磁式电流互感器相比,基于法拉第效应的光纤电流传感器有许多明显的优点,因而获得了广泛的研究。萨尼亚克(Sagnac)环形电流互感器是在干涉式光纤陀螺结构上发展起来的一种互感器结构。外界环境的振动因素是抑制Sagnac光纤电流互感器的最重要因素之一。为了消除振动对电流互感器测量结果的影响,给出了一种新型的光纤电流互感器免疫方案,其基本原理是增加外部闭环线圈来补偿所受振动影响。利用琼斯矩阵对此种光纤电流互感器结构进行了详细的理论分析。理论分析及实验结果均能证明此种方案可以完全消除电流互感器在实际环境中所受振动因素的不利影响。为高精度Sagnac干涉式光纤电流互感器的实现提供了可行的解决方法。     

Stabilisation of external optical feedback phase in a semiconductor laser

The linewidth of a semiconductor laser was reduced and held to much less than 1 MHz using a simple DC scheme for the stabilisation of the phase of external optical feedback. This scheme was based on the antisymmetric response to feedback phase at the two laser facets.     

双波长光纤光栅外腔半导体激光器中波长转换

提出了基于双波长光纤光栅外腔半导体激光器增益饱和效应的全光波长转换方案，特点是可将输入信号同时转换到激光器的2个波长上。在静态波长转换实验中，观察到了1554.8nm输入信号对激光器1531.5nm与1549.4nm波长输出功率的增益饱和作用。表明可实现输入信号到激光器的两个波长的同时转换。     

一种改进的光载波抑制产生光毫米波的方法

为了延长光毫米波的传输距离,提出了一种改进的光载波抑制产生光毫米波的方法。在中心站采用马赫-曾德尔调制器将射频信号调制到光载波上产生光载波抑制调制光信号,再将产生光信号的2个边带分离,将2.5Gbit/s数据信号调制到其中1个边带上,再与未调信号耦合后产生光毫米波并通过光纤传送至基站。在基站中通过光电转换器产生电毫米波。从理论上分析了这种光毫米波的传输特性并通过实验验证了光毫米波在光纤中可以传输40km。仿真和实验结果表明,这种方式产生的光毫米波具有很好的抗色散能力,延长了传输距离。     

Optical feedback phase stabilization of a semiconductor laser

The phase of optical feedback into a semiconductor laser was stabilized to maintain a minimum linewidth of 2 MHz. The scheme makes use of the linewidth information provided by a 1-MHz width external resonator. A further reduction in the laser linewidth to 300 kHz can be achieved and stabilized by using an external resonator with a narrower width.     

Optical frequency domain differential phase shift keying infemtosecond-pulse spectral modulation systems

We propose a novel scheme of differential phase shift keying (DPSK) in the optical frequency domain. We take advantage of the intrinsic coherence among spectral elements derived by spectrum slicing a femtosecond optical pulse, introducing differential phase modulation between adjacent spectral elements with a femtosecond-pulse shaper. Detection of the differential phase is achieved by a Mach-Zehnder (MZ) or Sagnac interferometric receiver without requirement of any external phase reference     

Highly flexible optical Nyquist pulses generation based on dual-parallel Mach–Zehnder modulator and intensity modulator

A new scheme for highly flexible optical Nyquist pulses generation is proposed by using a dual-parallel Mach–Zehnder modulator (DPMZM) and an intensity modulator (IM) without any external optical filter. The optical Nyquist pulses generator includes two stages. At the first stage, 2-, 3-, or 5-carrier light sources with two different frequency spacing are generated by utilizing a DPMZM. At the second stage, the light source used as seed light is then sent to IM, and two forms of optical frequency combs with spectral line flatness of less than 0.7 dB can be finally obtained by simply adjusting the DC bias and amplitude of radio frequency signal applied to IM. Ideal sinc-shaped Nyquist pulses are also generated in the time domain with bandwidth from 75 to 225 GHz and repetition rate from 40 to 80 ps. Simulation results show the high flexibility, effectiveness, and practicability of the proposed scheme, which can be applied to future high-capacity optical transmission systems.     

基于光纤光栅外腔半导体激光器增益饱和效应的全光波长转换实验研究

对基于光纤光栅外腔半导体激光器增益饱和效应的全光波长转换器的静态与动态特性进行了实验研究。为消除反馈光与转换信号输出光对光源的不利影响及提高光输入、输出信号耦合效率 ,提出了采用环形器进行信号耦合的光学结构。实验结果表明 ,转换器件具有高于 30nm的波长转换间隔 ,并可实现波长上、下转换。进行了15 5Mbit/s伪随机码调制信号的动态波长转换实验。     

Externally modulated mode-locked laser diodes for microwave transmission links

An externally modulated mode-locked laser diode is proposed to transmit high centre frequency, fractional bandwidth microwave signals over optical fibres. The authors demonstrate the feasibility of this scheme using an external Bragg cell to modulate (at 68.7 MHz) an actively mode-locked laser diode (mode-locked at 2.05 GHz).<>     

Experimental demonstration of CW light injection effect in upstream traffic TDM-PON

High capacity time-division-multiplexed passive optical network (TDM-PON) is an emerging fiber access network that deploys optical access lines between a carrier’s central office (CO) and a customer sites. In this investigation, we demonstrate and analyze the continuous wave (CW) upstream effect in TDM-PONs. Besides, we also propose and design a protection apparatus in each optical network unit (ONU) to avoid a CW upstream traffic in TDM-PONs due to sudden external environment change or ONU failure. When an upstream CW injection occurs in TDM access network, the protection scheme can stop the CW effect within a few ms to maintain the entire data traffic.     

基于直流光注入直调DFB-LD的可调光毫米波信号产生技术

提出了一种基于直流光注入直接调制分布反馈式半导体激光器(DFB-LD)的载波可调的光毫米波生成方案,利用直接调制DFB-LD的输出瞬态波长随驱动电流增大而蓝移的特点,将直流光注入至直调DFB-LD的0码波长附近注入锁定。锁定的直调激光器在1码时输出的蓝移波长与原注入波长相位相干,再通过光电探测器将拍频信号转换为调制的光毫米波信号。实验重点讨论了40GHz光毫米波的产生,同时完成了30、40、50和60GHz光毫米波的可调谐性实验。本文的方案结构简单,无需外调制器和微波本振,载波可调并可产生高至60GHz光毫米波信号,可作为光/无线混合接入中成本节省的光上变频方案。