Photonic generation of power-efficient FCC-compliant ultra-wideband waveforms using semiconductor optical amplifier (SOA):theoretical analysis and experiment verification

We theoretically design a power-efficient ultra-wideband pulse generator by combining three monocycle pulses with different weights. We also experimentally demonstrate a feasible scheme to generate such power-efficient ultra-wideband waveforms using cross-phase modulation in a single semiconductor optical amplifier. The designed ultra-wideband pulse fully satisfies the requirements for the spectral mask specified by the Federal Communications Commission with high power efficiency. In the experiment, a power-efficient ultra-wideband waveform with a pulse duration of 310 ps is achieved, and the power efficiency is greatly improved compared with that of a single nlonocycle pulse or a mixture of two monoeycles.

Semiconductor Optical Amplifier (SOA)-Fiber Ring Laser and Its Application to Stress Sensing

We have developed a novel optical fiber ring laser using a semiconductor optical amplifier (SOA) as the gain medium, and taking advantage of polarization anisotropy of its gain. The frequency difference of the bi-directional laser is controlled by birefringence which is introduced in the ring laser cavity. The beat frequency generated by combining two counter-propagating oscillations is proportional to the birefringence, the fiber ring laser of the present study is, therefore, applicable to the fiber sensor. The sensing signal is obtained in a frequency domain with the material which causes the retardation change by a physical phenomenon to be measured. For the application to stress sensing, the present laser was investigated with a photoelastic material.

基于SOA光纤环形激光器的分布式声传感系统

为了降低传统分布式声学传感器(DAS)系统复杂度并提高信噪比(SNR),提出了一种基于半导体光放大器的光纤环形激光器(SOA-FRL)的DAS系统。该系统用SOA-FRL取代了传统的DAS系统中的窄线宽激光器和脉冲调制器,实现了高稳定的光脉冲输出;采用双脉冲外差探测方法,实现了精确的声信号探测和声源定位。实验结果表明:在频率为1 kHz、幅值为1.14 rad的声信号作用下,所提系统的解调SNR高达38.25 dB,空间分辨率为12 m。

Towards 640 Gbit/s wavelength conversion based on nonlinear polarization rotation in a semiconductor optical amplifier

Taking into account ultra-fast carrier dynamics, this paper models 640 Gbit/s wavelength conversion scheme based on nonlinear polarization rotation （NPR） in a single semiconductor optical amplifier （SOA） and investigates the performance of this kind of wavelength conversion scheme in detail. In this model, two carrier temperature equations are introduced to substitute two energy density equations, which reduce the complexity of calculation in comparison with the previous model. The temporary gain and phase shift dynamics induced by ultra-short optical pulses are numerically simulated and the simulated results are qualitatively in good agreement with reported experimental results. Simulated results show that non-inverted and inverted 640 Gbit/s wavelength conversions based on NPR are achieved with clear open eye diagrams. To further investigate the performance of the non-inverted wavelength conversion scheme, the dependence of output extinction ratio （ER） on some key parameters used in simulation is illustrated. Furthermore, simulated analyses show that high performance non-inverted wavelength conversion based on NPR can be achieved by using a red-shifted filtering scheme.

Quantum-dot Semiconductor Optical Amplifiers in State Space Model

A state space model(SSM) is derived for quantum-dot semiconductor optical amplifiers(QD-SOAs).Rate equations of QD-SOA are formulated in the form of state update equations,where average occupation probabilities along QD-SOA cavity are considered as state variables of the system.Simulations show that SSM calculates QD-SOA′s static and dynamic characteristics with high accuracy.

Semiconductor Optical Amplifier and Gain Chip Used in Wavelength Tunable Lasers

The design concept of semiconductor optical amplifier(SOA)and gain chip used in wavelength tunable lasers(TL)is discussed in this paper.The design concept is similar to that of a conventional SOA or a laser;however,there are a few different points.An SOA in front of the tunable laser should be polarization dependent and has low optical confinement factor.To obtain wide gain bandwidth at the threshold current,the gain chip used in the tunable laser cavity should be something between SOA and fixed-wavelength laser design,while the fixed-wavelength laser has high optical confinement factor.Detailed discussion is given with basic equations and some simulation results on saturation power of the SOA and gain bandwidth of gain chip are shown.

Photonic multi-shape UWB pulse generation using a semiconductor optical amplifier-based nonlinear optical loop mirror

We propose and demonstrate a scheme to implement photonic multi-shape ultra-wideband（UWB） signal generation using a semiconductor optical amplifier（SOA） based nonlinear optical loop mirror（NOLM）.By employing the cross phase modulation（XPM） effect,cross gain modulation（XGM）,or both,multi-shape UWB waveforms are generated including monocycle,doublet,triplet,and quadruplet pulses.Both the shapes and polarities of the generated pulses are flexible to adjust,which may be very useful in UWB pulse shape modulation and pulse polarity modulation.

Analytic approach to the small-signal frequency response of saturated semiconductor optical amplifiers using multisection model

An analytic solution derived by multisection model to the small-signal frequency response （SSFR） of wavelength conversion based on cross-gain modulation （XGM） in semiconductor optical amplifiers （SOAs） is presented. The result contains details that can affect the characteristics of SSFR significantly more than previous ones.

Semiconductor optical amplifier used as regenerator for degraded differential phase-shift keying signals

Phase and amplitude regeneration are necessary for degraded differential phase-shift keying communication sys- tems. This paper proposes a regenerator based on semiconductor optical amplifier for differential phase-shift keying signals. The key regeneration mechanism is theoretically analysed. The effectiveness of semiconductor optical amplifier based regenerator is demonstrated by comparing the bit error rate and eye diagrams before and after regeneration for 40-Cbit/s differential phase-shift keying 1080-km transmission systems. The results show that regeneration effects are very well. Bit error rate is tess than 10-12 with the regenerator.

All-optical XNOR and AND gates simultaneously realized in a single semiconductor optical amplifier with improved dynamics

All-optical XNOR and AND logic gates using four-wave mixing （FWM） and cross-gain modulation （XGM） in a single semiconductor optical amplifier （SOA） with improved dynamics are simultaneously realized. By numerical simulation, the effects of the input optical wave powers and injection current on the critical factors of the logic gate performances, such as the ON-OFF contrast ratio, the power-output level of the logic ＇1＇, and the difference between power outputs of the logic ＇1＇, are investigated in detail. In addition, the effect of the counter-propagating CW pump on the gain recovery is analysed.

All-optical error-bit amplitude monitor based on NOT and AND gates in cascaded semiconductor optical amplifiers

This paper proposes and simulates a novel all-optical error-bit amplitude monitor based on cross-gain modulation and four-wave mixing in cascaded semiconductor optical amplifiers （SOAs）, which function as logic NOT and logic AND, respectively. The proposed scheme is successfully simulated for 40 Gb/s return-to-zero （RZ） signal with different duty cycles. In the first stage, the SOA is followed by a detuning filter to accelerate the gain recovery as well as improve the extinction ratio. A clock probe signal is used to avoid the edge pulse-pairs in the output waveform. Among these RZ formats, 33% RZ format is preferred to obtain the largest eye opening. The normalized error amplitude, defined as error bit amplitude over the standard mark amplitude, has a dynamic range from 0.1 to 0.65 for all RZ formats. The simulations show small input power dynamic range because of the nonlinear gain variation in the first stage. This scheme is competent for nonreturn-to-zero format at 10Gb/s as well.

Optimization of regenerator based on semiconductor optical amplifier for degraded differential phase shift keying signal

Real time phase regeneration is necessary for degraded phase modulation format optical communication systems. A regenerator based on the discrimitive gain effect of a semiconductor optical amplifier was proposed in recent years. In this paper, for this type of regenerator, its optimal working condition is found by solving the dynamic equations which describe the variance of the optical field and carrier density in the semiconductor optical amplifier by the finite difference method. The results show that the optimal improvement of signal Q factor can reach more than 2.2 dB.

Reconfigurable all-optical dual-directional half-subtractor for high-speed differential phase shift keying signal based on semiconductor optical amplifiers

All-optical digital logic elementary circuits are the building blocks of many important computational operations in future high-speed all-optical networks and computing systems. Multifunetional and reconfigurable logic units are essential in this respect. Employing the demodulation properties of delay interferometers for input differential phase shift keying signals and the gain saturation effect in two parallel semiconductor optical amplifiers, a novel design of 40 Cbit/s reconfigurable all-optical dual-directional half-subtractor is proposed and demonstrated. All output logic results show that the scheme achieves over 11=dB extinction ratio, clear and wide open eye diagram, as well as low polarization dependence （〈 1 dB）, without using any additional input light beam. The scheme may provide a promising candidate for future ultrafast all-optical signal processing applications.

A High Efficiency Wavelength Conversion Scheme Based on Four Wave Minxing in a Semiconductor Optical Amplifier

A new approach of all optical wavelength converter based on four wave mixing (FWM) in a semiconductor optical amplifier (SOA) with the conjugate wave reflected by a fiber Bragg grating (FBG) and then amplified by the SOA is reported. By adjusting the pump power, the conversion efficiency could be improved 7～10dB with signal to background noise ratio (SBR) deteriorated 1～2dB, compared with traditional single pump four wave mixing.

10-Gb/s Transmission in WDM PON Employing Reflective Semiconductor Optical Amplifier and Fibre Bragg Grating Equaliser

We propose a 10-Gb/s WavelengthDivision-Multiplexed Passive Optical Network(WDM-PON) scheme with upstream transmission employing Reflective Semiconductor Optical Amplifier(RSOA) and Fibre Bragg Grating(FBG) optical equaliser.Transmissions of10-Gb/s non return-to-zero signals using a 1.2-GHz RSOA and FBG optical equaliser with different setups are demonstrated.Significant performance improvement and 40-km standard single mode fibre transmission are achieved using FBG optical equaliser and Remotely Pumped Erbium-Doped Fibre Amplifier(RP-EDFA),where they are used to equalise the output of the band-limited RSOA and amplify the seed light and upstream signal,respectively.

Device Design and Characteristics for SOA-basedAll Optical Signal 2R Regeneration

A new scheme based on SOA-MZI for all-optical 2R regeneration is proposed. The characteristics of gain and switching window of this device are investigated in detail. Numerical simulation results indicate that the nonlinear gain compression, the time delay between the input optical signal and the width of the optical pulse are essential parameters for a good performance of all-optical 2R regeneration.

155 Mb/s-10 Gb/s combined FSK-IM/optical label-packet modulation signals 100 km transmission over standard single mode fiber using mid-span spectral inversion by four-wave mixing in an SOA

This paper introduces the mid-span spectral inversion by four-wave mixing in a commercially available semiconductor optical amplifier （SOA） with a length of about 1.5 mm to optical label switching network based on combined frequency shift keying （FSK）-intensiy modulation （IM）/optical label-packet modulation to overcome the dispersion limitation of fiber. The 155 Mb/s-10 Gb/s combined FSK/IM signal is experimentally transmitted over a 100 km standard single mode fiber. 10^-10 and 10^-9 BER （bit error ratio）, or even better, is achieved for the FSK label and IM packet, respectively. The -19 dB power conversion efficiency is obtained for -1 nm wavelength detuning.

光放大器原理及其发展

光通信系统的工作性能,除与光源有关外,还与其传输媒质有关。随着光纤技术的发展,通过追求光通信领域的远距离传输,诞生了光放大器,光放大器可以做到直接放大光信号,在通信领域有很大的应用价值。总结了光放大器的基本原理及其发展。首先介绍了光放大器的概念、分类和原理。然后分别对三类光放大器的关键技术进行了介绍,包括工作原理与性能方面,然后对各类光放大器的国内外现状进行了分析。最后,对光放大器未来的发展进行了展望。

全光时钟提取中利用SOA抑制低频噪音的实验研究

针对基于高精细度F-P滤波器的40 Gbps全光时钟提取得到的时钟中所含有的低频率噪音,提出了利用半导体光放大器对其进行抑制的方案.理论上,利用SOA的传输函数对其低频抑制作用进行了分析,并通过实验予以验证.在实验中,利用该方案得到了较高质量的40 GHz时钟,均方根抖动<1.4 p.

基于单端SOA波长转换器的消光比特性分析

对一种基于单端半导体光放大器(SOA)的交叉增益调制型 (XGM)全光波长转换器结构建立了动态理论模型,以这个模型为基础分析了抽运光功率、探测光功率、剩余反射率、转换波长转换间隔、注入电流对转换后探测光的输出消光比的影响。结果表明,利用单端SOA实现波长转换比普通SOA实现波长转换将获得更好的输出消光比特性。