Performance of traveling-wave electroabsorption modulators depending on microwave properties of waveguides calculated using the FDTD method

We present a method to analyze electrical and optical characteristics of traveling-wave electroabsorption modulators (TW-EAMs) using the finite-difference time-domain method. We consider the interaction between electromagnetic fields and optical powers in waveguides in time domain to model electrical and optical behaviors of TW-EAMs. The effects of microwave properties of waveguides on modulation response and output optical power of TW-EAMs are analyzed by the proposed method. The characteristic impedance of TW-EAMs is more important than microwave index to obtain large modulation bandwidth of TW-EAMs when impedance matching techniques are not used. However, effective refractive index match between microwave and lightwave becomes important as the waveguide length increases. The microwave property closely related to the extinction ratio of output optical powers is the microwave loss. When impedance match is achieved by low-impedance termination, the velocity matching between microwave and lightwave becomes important.     

复信号处理及其在电力线载波通信中的应用

电力线载波通信系统通常应用正交调制有效地抵消带外和带内干扰信号以实现单边带调制,应用多进制正交幅度调制(M-QAM)实现高速数据传输,将正交调制作为复信号来研究可以简化对通信系统的分析和设计.文中介绍了复信号的定义、实调制与复调制、用复低通信号表示带通信号、单边带复调制与解调,以及数字单边带韦瓦复调制在数字化载波机中的应用.     

Highly Stable 160-Gb/s OTDM Technologies Based on Integrated MUX/DEMUX and Drift-Free PLL-Type Clock Recovery

This paper reports 160-Gb/s optical time-division-multiplexed (OTDM) technologies including an all-optical integrated multiplexer (MUX) providing all-channel independent modulation, an all-optical integrated demultiplexer (DEMUX) that offers all-channel simultaneous demultiplexing, and a drift-free phase-locked-loop (PLL)-type clock recovery circuit for ultrahigh-speed OTDM signals. We present the configuration of each technology and the results of experiments on those technologies. Highly stable operation is successfully demonstrated by using a MUX based on periodically-poled lithium niobate (PPLN) hybrid integrated planer lightwave circuit (PLC), a DEMUX based on semiconductor optical amplifier hybrid integrated PLC, and clock recovery circuit based on a PLL with an optical phase modulator and a PPLN waveguide     

基于直接数字频率合成技术的数字调制实现

通过对直接数字合成技术DDS工作原理的分析，结合具体的DDS芯片AD9850，详细介绍了包括FM，FSK，PSK等多种数字调制方法的实现。结果表明，数字调制具有分辨率高、全数字化可编程、相位噪声低等特点。利用多路选择器连接调制信号和载波信号，可以实现多种调制信号的任意切换。     

Nonlinear Distortion in a Silicon Microring-Based Electro-Optic Modulator for Analog Optical Links

We analyze silicon microring modulators for analog signal generation, in terms of harmonic and intermodulation distortions. Free carrier plasma dispersion effect in silicon, Lorentzian-shaped resonance profile, and cavity photon lifetime are identified as the sources of modulation nonlinearity. Simulations show that the silicon microring modulators exhibit good modulation index and carrier-to-distortion ratio (CDR). For the generation of 10-GHz suboctave analog signals, a high optical-modulation-index of up to 46%, a CDR of 57 dB, and a spurious free dynamic range of 96 dB can be obtained. In fiber transmission, the microring-generated signal CDR can be improved by 10 dB due to the interaction between frequency chirp and chromatic dispersion.      

多台电力电子变压器云-边脉宽调制同步控制策略

为提升多台电力电子变压器(Power Electronic Transformer)的高频开关谐波协同控制能力,需实现高精度、高可靠的脉宽调试同步控制。本文提出一种基于“云-边”双重信息的多PET脉宽调制同步策略：在通讯系统正常运行时,PET利用“云”端发送的同步信号实现高精度的脉宽调试同步;当通讯系统故障时,PET可利用“边”端计算结果实现高可靠的脉宽调制同步。因硬件要求低,该策略易于应用。实验证明,该策略能兼顾脉宽调制同步的精度与可靠性,保证高频率开关谐波协同控制。     

High-capacity undersea long-haul systems

This paper reviews technologies and techniques that have been used in deployed long-haul wavelength division multiplexing (WDM) systems and emerging technologies that could be used for the next generation of cost-reduced systems. The overview of current generation technologies starts with a discussion of modulation formats, focusing on the superior properties of the chirped return to zero on-off shift keying (CRZ-OOK) modulation format. The use of 10-Gb/s CRZ-OOK modulation format together with advanced fiber types, more powerful forward error correction (FEC), and broadband erbium-doped fiber amplifiers resulted in the deployment of dense WDM systems with capacities per fiber in terabits per second range and trans-Pacific reach. Demand for the systems with large design capacity led to further development of broadband optical amplifiers. Laboratory demonstrations successfully expanded transmission into the full C-band and later in the C and L transmission bands. The current market conditions dictate the need for reducing the first cost of an installed system rather than reaching record capacity per fiber. Reducing first cost can be achieved by reducing the amount of optical amplifiers in the cable by utilizing an excess performance margin provided by available RZ-OOK technology. Further improvements would be possible if more powerful FEC and modulation formats with better receiver sensitivity are used. For example, the RZ differential phase-shift keying (RZ-DPSK) modulation format with 3-dB better receiver sensitivity and better nonlinear tolerance to large amounts of accumulated dispersion is a very promising technology. This paper will review long-haul transmission results using RZ-DPSK and will compare the transmission properties of RZ-DPSK signals versus RZ-OOK signals. Due to superior receiver sensitivity, the RZ-DPSK modulation format can be an enabling technology for 40-Gb/s per channel transoceanic transmission.     

High-Speed OTDM and WDM Networks Using Traveling-Wave Electroabsorption Modulators

We describe the design and performance of a number of elements based on traveling-wave electroabsorption modulators (TW-EAMs) in optical time-division-multiplexing (OTDM) and wavelength-division-multiplexing (WDM) networks. The incorporation of traveling-wave (TW) electrode design into electroabsorption modulators (EAMs) relieves the resistance-capacitance (RC ) bandwidth limitation common to lumped components, enabling higher operation speed without shortening the device. As a result, high-speed operation can be combined with essential modulator characteristics such as modulation efficiency and extinction ratio. While significant modulation bandwidth has been achieved, a lesser known aspect is that the TW electrode also provides an extra dimension for improving and enabling functionalities beyond broadband modulation. This new dimension originates from the distributed effect of the TW design and its interactions with distinctive EAM properties. This paper reviews such developments in recent years with specific applications for optical signal processing in OTDM and WDM networks. The covered functionalities include various optical gating operations for OTDM, regenerative wavelength conversions for WDM, and clock recovery     

远动通道FSK信号载频检测方法的研究及其应用

为了实现对基于 FSK(频移键控 )调制方式的远动信道的监控 ,必须首先准确检测 FSK信号的载波频率。 FSK信号的频谱成分比较复杂 ,包含基带信号引入的连续谱和载波信号引入的离散谱两部分 ,传统的信号处理方法难以准确测量。针对以上特点 ,提出了一种新的非线性变换——时域拼接变换 ,通过对 FSK信号的分割和重新组合 ,消除了两个载波信号之间的相关性 ,抑制了基带信号对功率谱的影响 ,将离散谱从功率谱中分离 ,并结合现代功率谱估计方法 ,实现了对信号载波频率的高精度测量。计算机仿真与实验证明 ,该方法是一种有效的 FSK载波频率测量方法     

Reduced model to describe SPM-limited fiber transmission indispersion-managed lightwave systems

A reduced model to describe self-phase modulation (SPM)-limited fiber transmission in dispersion-managed lightwave systems is presented. By introducing a new figure of merit, the maximum transmission distance versus optical power can be determined without any numerical simulation. Together with simplified models for other nonlinear fiber effects, a useful set of design rules for a first-order performance estimation of wavelength-division multiplexed (WDM) systems is established     

Continuous-phase frequency-shift keying with external modulation

A high-speed external modulation scheme for optical continuous-phase frequency-shift keying (CPFSK) is presented. In external frequency-shift keying (FSK) modulation using single-sideband modulation technology, an optical upper/lower sideband (USB/LSB) component with respect to a carrier frequency is selectively generated. However, the FSK-modulated signal has phase discontinuities at the timings of frequency shifts. To overcome the problem, we propose a synchronous control technique that enables continuous phase modulation. In the external CPFSK modulation, the USB/LSB is allowed to shift to the other state when their phases coincide with each other. It is shown that CPFSK with a zero-to-peak frequency deviation of 0.5/spl times/(bit rate) is achieved with this synchronous control. Occupant bandwidth is less than half that of the externally modulated incoherent FSK with phase discontinuities. At a modulation speed of 10 Gb/s, higher order sidelobes are highly suppressed by more than 20 dB at the 20-GHz offset, comparing to a conventional binary phase-shift keying (BPSK). By the use of a Mach-Zehnder interferometer with balanced photodetection, receiver sensitivity is 3-dB greater than that of an on-off keying, as well as a BPSK. In this paper, we report on the experimental demonstration of CPFSK modulation/demodulation. A six-channel wavelength-division-multiplexed, 10-Gb/s CPFSK modulation/demodulation was successfully demonstrated.     

FSK通信体制DSP实现技术

FSK通信体制具有调频信号容易产生,系统设备相对简单,而且抗干扰能力优秀的特点.本设计利用高速的数字信号处理芯片来实现FSK通信体制,提高了通信的效率和实时性.     

基于循环生成对抗网络的增强罗兰信号生成

在信号生成算法中,需要大量标记信号样本用于网络训练,但通常携带电文信息标记的信号难以批量获取。针对此问题本文提出一种基于循环生成对抗网络和迁移学习的方法,实现了无需大量信号及对应电文作为标记的增强罗兰信号生成,并使用迁移学习在少量实测信号情况下快速生成。循环生成对抗网络的结构包括两个生成器和两个判别器,利用无需一一对应的增强罗兰信号和电文数据集,使生成器学习到两个数据集之间的相互转换关系,实现输入电文数据可以生成与之相对应的增强罗兰信号,并且针对增强罗兰信号的特性,使用一维卷积、残差网络、自注意力机制对网络模型进行改进。实验证实,生成信号与实测数据的均方误差为0.015 3,平均皮尔逊相关系数为0.984 3,且所含电文信息准确率为99.02%。本文在PSK、ASK、FSK数据集上验证了算法,实验结果表明生成的信号满足预期,为未知参数的信号调制和解调提供一种新的思路。     

Subharmonic synchronous mode-locking of a monolithic semiconductorlaser operating at millimeter-wave frequencies

Optical pulse trains at millimeter-wave frequencies are generated by subharmonic synchronous mode-locking of a monolithic distributed Bragg reflector semiconductor laser, by which an initially passively mode-locked semiconductor laser is stabilized by injecting optical pulses at subharmonic frequencies of its resonant frequency. The stabilized pulse trains are characterized in terms of phase noise, timing jitter, locking range and modulation depth under various injection conditions including injected signal power levels, pulsewidths, and subharmonic numbers. It is also shown that subharmonic synchronous mode-locking can provide pulse trains with a very low level of phase noise (⩽-86 dBc/Hz @ 10 kHz offset), reasonably wide locking ranges (4-20 MHz) and low levels of amplitude modulation (96%-99%). Such pulse characteristics are compared with those achieved by the subharmonic hybrid mode-locking scheme, where stabilization is realized by injecting electrical signals at subharmonic frequencies of the laser's resonant frequency. It is shown that subharmonic hybrid mode-locking is only effective at low subharmonic numbers (2-6), while subharmonic synchronous mode-locking can be realized with much larger subharmonic numbers. It is also revealed from the comparison that while subharmonic hybrid mode-locking scheme is simple and cost-effective approach for the generation of high-frequency signals from semiconductor lasers, subharmonic synchronous mode-locking scheme can offer pulse trains using very low-frequency driving electronics with superior performance such as larger locking ranges, and lower levels of phase noise and amplitude modulation     

An asynchronous pulse width modulator for DC-DC buck converter

This paper presents an asynchronous pulse width modulation (APWM) approach for the analysis of a new class of the switched mode power supply (SMPS). The proposed APWM significantly simplified the mathematical analysis by utilizing a binary comparator (BAPWM) and a distinctive delay cell instead of hysteretic comparator. By this way, the mathematical analysis can be extended to study the behavior of high-order self-oscillating modulators in terms of key parameters such as the harmonic distortion and the stability. The performance of the proposed BAPWM is deeply analyzed for different orders of loop filters (here up to third order) in both time and frequency domain. To verify the effectiveness of the proposed analytical derivations, the BAPWMs are employed in a classic synchronous DC-DC buck converter and its closed loop performance, in terms of stability, has been investigated. Then the converter is designed and simulated in 130-nm CMOS technology to convert input voltage of 5 to 3.3 V with maximum load current of 1 A, using Spectre simulator. From the post-layout simulation results, the peak efficiency conversion efficiency for 3.3 V output voltage is higher than 89%.     

Optical Signal Processing by Phase Modulation and Subsequent Spectral Filtering Aiming at Applications to Ultrafast Optical Communication Systems

This paper describes optical signal processing based on optical phase modulation and subsequent optical filtering, which is applicable to 160-Gb/s optical time-division multiplexed (OTDM) subsystems. Ultrafast phase modulation of an optical signal is done by self-phase modulation (SPM) and cross-phase modulation (XPM) when an optical pulse passes through a nonlinear optical fiber. Such phase modulation induces the spectral shift of the optical signal. Various types of optical signal processing are realized simply by filtering out the spectral-shifted component. Using SPM-based pulse reshaping in a 500-m-long silica-based highly nonlinear fiber (HNLF), we demonstrate highly stable generation of a 10-GHz 2-ps optical pulse train tunable over the entire C band. A phase-locked loop (PLL) can suppress the slow phase drift of the output pulse train induced by fluctuations of the nonlinear fiber length, enabling the application of the pulse generator to a 160-Gb/s OTDM transmitter. Based on XPM in a 2-m-long photonic crystal fiber, optical time-division demultiplexing of 160-Gb/s optical signals is demonstrated. The long-term stability is drastically improved as compared with the device composed of a conventional silica-based HNLF, because the short fiber length reduces the phase fluctuation between the signal and control pulses. Instead of nonlinear fibers, an electrooptic modulator such as a (LN) modulator also performs the phase modulation in a more practical manner. We propose and demonstrate an optoelectronic time-division demultiplexing scheme for a 160-Gb/s OTDM signal, which consists of an LN phase modulator driven by a 40-GHz electrical clock and an optical bandpass filter (BPF). We also demonstrate base-clock recovery from a 160-Gb/s optical signal with an optoelectronic PLL. The phase comparator is simply composed of an LN phase modulator and an optical BPF, ensuring the stable and reliable operation in the 160-Gb/s receiver.     

超声传感器调制特性及收发电路研究

本文分析了广泛应用于无线通信中的频率键控调制(FSK)及幅值键控调制(ASK)技术的基本概念及调制原理,针对收发分体式超声波传感器T40-16及R40-16,设计并实现了超声波调制发射与解调接收电路,在此基础上进行了超声波FSK及ASK调制特性的实验研究.实验结果表明:可以对超声波信号进行FSK调制发射,调制、解调电路易于实现且调制与解调效果好;对超声波信号进行ASK调制发射时存在"余振"现象,可以通过调整加在超声波发射传感器两端的激励信号的占空比而进行改善.     

Benefit of SPM-based all-optical reshaper in receiver for long-haul DWDM transmission systems

The effectiveness of a self-phase modulation (SPM)-based all-optical reshaper with optically time-division-demultiplexing receiver was experimentally investigated using 42.7-Gb/s carrier-suppressed return-to-zero (CS-RZ) signals. We have confirmed that this scheme is quite effective to suppress the waveform degradation due to optical signal bandlimitation. We have demonstrated 80% spectral efficiency without using polarization demultiplexing by using the all-optical reshaper. We have also demonstrated 50-GHz-spaced 55/spl times/42.7 Gb/s signals transmission over 2500 km, using an optically bandlimited CS-RZ signal and the SPM-based all-optical reshaper in receiver without using polarization demultiplexing. A Q-factor improvement of about 1.5 dB was obtained by using the all-optical reshaper.     

Long-distance QKD transmission using single-sideband detection scheme With WDM synchronization

We report a long-distance, polarization insensitive, quantum key distribution scheme using single-sideband (SSB) detection. The method uses an amplitude modulation to transmit photon in sidebands. The system acts as a fainted laser diode whose information quantum state is encoded in the phase difference between the main peak and its sidebands. Using the dispersion properties of the fiber, the relative phase between interacting quantum states can be reliably controlled by sending a reference signal over the physical link that transmits the quantum signal. Therefore, photon detection can be performed very accurately over long distances. Stability of the synchronization technique with respect to optical path variation is also discussed. The reconciliation process uses a LAN connection as public channel. Experiments were carried out in the C-band telecom window (1550 nm), over a 40-km standard single-mode fiber spool as well as over a 10-km deployed fiber.     

数字调制参数校准仿真研究

表征信号调制质量的数字调制参数是数字通信系统的主要技术指标,数字调制参数校准可以保证通信设备的质量。为给通信装备数字调制参数校准工作提供技术支持,本文总结研究了数字调制参数校准的基本方法,在建立数字调制参数校准仿真通用模块的基础上,进行了QPSK与FSK数字调制参数校准方法研究,并通过仿真及试验证实了两种方法的有效性。通过校准仿真,大大减少了校准方法研究过程中的硬件损耗、降低了研究成本。