A 32-channel 100 GHz wavelength division multiplexer by interleaving two silicon arrayed waveguide gratings

A 32-channel wavelength division multiplexer with 100 GHz spacing is designed and fabricated by interleaving two silicon arrayed waveguide gratings(AWGs).It has a parallel structure consisting of two silicon 16-channel AWGs with200 GHz spacing and a Mach-Zehnder interferometer(MZI)with 200 GHz free spectral range.The 16 channels of one silicon AWG are interleaved with those of the other AWG in spectrum,but with an identical spacing of 200 GHz.For the composed wavelength division multiplexer,the experiment results reveal 32 wavelength channels in C-band,a wavelength spacing of 100 GHz,and a channel crosstalk lower than-15 dB.

Performance of phase-matching quantum key distribution based on wavelength division multiplexing technology

Quantum key distribution(QKD) generates information-theoretical secure keys between two parties based on the physical laws of quantum mechanics. The phase-matching(PM) QKD protocol allows the key rate to break the quantum channel secret key capacity limit without quantum repeaters, and the security of the protocol is demonstrated by using equivalent entanglement. In this paper, the wavelength division multiplexing(WDM) technique is applied to the PM-QKD protocol considering the effect of crosstalk noise on the secret key rate. The performance of PM-QKD protocol based on WDM with the influence of adjacent classical channels and Raman scattering is analyzed by numerical simulations to maximize the total secret key rate of the QKD, providing a reference for future implementations of QKD based on WDM techniques.

Exploiting the Faster-Than-Nyquist Concept in Wavelength-Division Multiplexing Systems Using Duobinary Shaping

This paper begins with Nyquist wavelengthdivision multiplexing （WDM） and then introduces fasterthanNyquist. In fasterthanNyquist a certain amount of intersymbol interference （ISI） is accepted, which violates the fundamental principle of Nyquist WDM. This results in muchrelaxed transceiver bandwidth and simpler spectral design. However, in fasterthanNyquist, implementation complexity is shifted from the transmitter side to the receiver side. Therefore, successful application of fasterthanNyquist depends on innovation in the receiver structure. In this paper, we discuss the guidelines for implementing suboptimum, lowcomplexity receivers based on fasterthanNyquist. We suggest that duobinary shaping is a good technique for trading off achievable spectral efficiency, detection performance, and implementation complexity and might be preferable to Nyquist WDM. Experiments are conducted to verify robustness of the proposed technique.

Multi-functional optical fiber sensor system based on a dense wavelength division multiplexer

We propose a novel and efficient multi-functional optical fiber sensor system based on a dense wavelength division multiplexer(DWDM).This system consists of an optical fiber temperature sensor, an optical fiber strain sensor, and a 48-channel DWDM.This system can monitor temperature and strain changes at the same time.The ranges of these two sensors are from-20℃ to 100℃ and from-1000 με to 2000 με, respectively.The sensitivities of the temperature sensor and strain sensor are 0.03572 nm/℃ and 0.03808 nm/N, respectively.With the aid of a broadband source and spectrometer,different kinds and ranges of parameters in the environment can be monitored by using suitable sensors.

A new synchronization scheme based on time division multiplexing and wavelength division multiplexing technology for practical quantum key distribution system

Three clock synchronization schemes for a quantum key distribution system are compared experimentally through the outdoor fibre and the interaction physical model of the the clock signal and the the quantum signal in the quantum key distribution system is analysed to propose a new synchronization scheme based on time division multiplexing and wavelength division multiplexing technology to reduce quantum bits error rates under some transmission rate conditions, The proposed synchronization scheme can not only completely eliminate noise photons from the bright background light of the the clock signal, but also suppress the fibre nonlinear crosstalk.

Reference-frame-independent quantum key distribution of wavelength division multiplexing with multiple quantum channels

Reference-frame-independent quantum key distribution(RFI-QKD)can allow a quantum key distribution system to obtain the ideal key rate and transmission distance without reference system calibration,which has attracted much attention.Here,we propose an RFI-QKD protocol based on wavelength division multiplexing(WDM)considering finite-key analysis and crosstalk.The finite-key bound for RFI-QKD with decoy states is derived under the crosstalk of WDM.The resulting secret key rate of RFI-QKD,which is more rigorous,is obtained.Simulation results reveal that the secret key rate of RFI-QKD based on WDM is affected by the multiplexing channel number,as well as crosstalk between adjacent channels.

Performance Evaluation of Wavelength Division Multiplexing Photonic Analogue-to-Digital Converters for High-Resolution Radar Systems

The performance of the wavelength division multiplexing (WDM) photonic analogue-to-digital converter (ADC) used for digitization of high-resolution radar systems is evaluated numerically by using the peak signal-to-noise ratio (SNR) metric. Two different WDM photonic ADC architectures are considered for the digitization of radar signals with 5 GHz of bandwidth (spatial resolution of 3 cm), in order to provide a comprehensive study of the compromises present when deploying radar signals with high-resolution: 1) a four-channel architecture with each channel employing an ADC with 5 GSamples/s, and 2) an eight-channel architecture with each channel employing an ADC with 2.5 GSamples/s. For peak powers of the pulsed source between 10 and 20 dBm and a distance between the radar antenna and the sensing object of 2.4 meters, peak SNR levels between 29 and 39 dB are achieved with the eight-channel architecture, which shows higher peak SNR levels when compared with the four-channel architecture. For the eight-channel architecture and for the same peak powers of the pulsed source, peak SNR levels between 11 and 16 dB are obtained when the distance increases to 13.5 meters. With this evaluation using the peak SNR, it is possible to assess the performance limits when choosing a specific radar range, while keeping the same resolution.

Silicon-Based Mode Converter and Demultiplexer for Wavelength Division Multiplexing Transmission by Using Multimode Interference Couplers

We present a mode converter and demultiplexer structure for wavelength division multiplexing (WDM) transmission by employing multimode interference (MMI) on Silicon-on-Insulator (SOI) platform. The mode converter and demultiplexer have a compact size of less than 2.7 μm × 43.7 μm. Moreover, the crosstalk between neighboring wavelength channel within C band (1530 nm to 1570 nm) can be reduced by utilizing the tapered phase shifter cascaded with MMI. The simulated results indicate that this structure has a low insertion loss of less than 1 dB, a low crosstalk of better than ?15 dB and a relatively high fabrication tolerance of ~10 nm. Such structure may find many potential applications in silicon photonic integrated devices.

Multichannel Adaptive Polarization Mode Dispersion Compensation with One Compensator in Dense Wavelength Division Multiplexing Transmission Systems

A simple two-section polarization mode dispersion(PMD) compensator is proposed for multichannel PMD compensation, which can compensate two or even more channels simultaneously. Because of the statistical characteristics and the frequency-dependence of PMD, for current single mode fiber with moderate PMD, the probability that all channels are severely degraded at the same time is extremely small, which makes it possible to compensate a dense wavelength division multiplexing(DWDM) transmission system with moderate PMD using this compensator. It is shown that the outage probability of a 40×43 Gb/s DWDM transmission system using this compensator is decreased significantly from 3.6×10-3 to 3.6×10-5.

Research on Raman Crosstalk in Broadband Wavelength Division Multiplexed Systems

After a theoretical model is put forward on the base of accurate description of the Raman gain profile and the physical quantity, maximum Raman crosstalk(MRC), which quantificationally depicts the intensity of Raman crosstalk is defined. The influences of launch power, fiber effective core area, fiber nonlinear index, fiber length, channel number and channel interval on MRC are deduced. The result indicates that compared with low speed and narrowband optical fiber communication system, serious Raman crosstalk lies in high speed and broadband system, which impacts the performance of the system badly. The result is useful for forecasting Raman crosstalk in broadband and high speed optical fiber communication system.

Highly-sensitive NO,NO2,and NH3 measurements with an open-multipass cell based on mid-infrared wavelength modulation spectroscopy

A compact prototype based on mid-infrared wavelength modulation spectroscopy（WMS）is developed for the simul-taneous monitoring of NO,NO2,and NH3 in the urban area.Three quantum cascade lasers（QCLs）with central frequencies around 1900.0 cm^-1,1600.0 cm^-1,and 1103.4 cm^-1are used for NO,NO2,and NH3detections,respectively,by timedivision multiplex.An open-path multi-pass cell of 60-m optical path length is applied to the instrument for high sensitivity and reducing the response time to less than 1 s.The prototype achieves a sub-ppb detection limit for all the three target gases with an average time of about 100 s.The instrument is installed in the Jiangsu environmental monitoring center to conduct performance tests on ambient air.Continuous 24-hour measurements show good agreement with the results of a reference instrument based on the chemiluminescence technique.

Novel architecture of WDM/OCDMA-PON based on SSFBG and wavelength re-modulation technology

A novel architecture of wavelength-division multiplexing/optical code division multiplexing access-passive optical network （WDM/OCDMA-PON） based on superstructure fiber Bragg grating （SSFBG） and wavelength re-modulation technology is proposed. In this scheme, WDM is overlaid on OCDMA channel in a single network by virtue of a kind of SSFBC, and the total capacity of hybrid PON can be extended by regulating the transmission power reasonably. Re, modulation technology is also a good method to save wavelength-specific components at the optical network unit （ONU） and cost of wavelength management on the customer side. In simulation system, 1.25 Gb/s up/downstream data are transported with good performance. In addition the crosstalk penalties from adjacent wavelength channels （with the same OC） are found to be negligible in upstream and downstream transmissions.

A SYNTHETIC ALGORITHM FOR WAVELENGTH ROUTING IN OPTICAL NETWORK

After analyzing the merits and shortcomings of Fixed-Alternated Routing algorithm (FAR) and Least Loaded Routing algorithm (LLR),we propose one novel dynamic optical routing algorithm. Having considered the influences of path’s length and path’s congestion just like in FAR and LLR,we take into account the network resource status-amount of free wavelengths in the network. Proposed algorithm sets up connections on three possible paths according to amount of available free wave-lengths in the network,which effectively decreases the blocking probability. The National Science Foundation (NSF) network and mesh-torus network simulation results show that the performance of this algorithm is better than that of FAR and LLR.

ROUTING AND WAVELENGTH ASSIGNMENT ALGORITHMS BASED ON EQUIVALENT NETWORKS

In this paper, a Wavelength Division Multiplexing (WDM) network model based on the equivalent networks is described, and wavelength-dependent equivalent arc, equivalent networks, equivalent multicast tree and some other terms are presented. Based on this model and relevant Routing and Wavelength Assign- ment (RWA) strategy, a unicast RWA algorithm and a multicast RWA algorithm are presented. The wave- length-dependent equivalent arc expresses the schedule of local RWA and the equivalent network expresses the whole topology of WDM optical networks, so the two algorithms are of the flexibility in RWA and the optimi- zation of the whole problem. The theoretic analysis and simulation results show the two algorithms are of the stronger capability and the lower complexity than the other existing algorithms for RWA problem, and the complexity of the two algorithms are only related to the scale of the equivalent networks. Finally, we prove the two algorithms’ feasibility and the one-by-one corresponding relation between the equivalent multicast tree and original multicast tree, and point out the superiorities and drawbacks of the two algorithms respectively.

Hybrid WDM/TDM PON system employing an all-optical wavelength converter

A new hybrid WDM/TDM passive optical network （PON） implemented by using all-optical wavelength converters （AOWCs） is proposed. The AOWCs are based on the cross-gain modulation （XGM） effect of the semiconductor optical amplifier （SOA）. Moreover, the feasibility of this sys- tem is experimentally demonstrated by evaluating the impacts of the optical wavelength conversion, time domain waveforms, eye diagrams and bit-error-rate （BER） in AOWC. The results show that the proposal will be a promising solution for the next generation access networks.

Analysis of Center Wavelength Shift of VCSEL Light in AWG for WDM-PON Applications

Center wavelength shift of vertical cavity surface emitting laser light in arrayed waveguide gratings is verified with mathematical and experimental analysis.It is induced by the linearly increasing trend of optical power of vertical cavity surface emitting laser by bias current increase.It is retrieved effectively to the original center wavelength by simple correction method of compensation.This was done for application of vertical cavity surface emitting laser as a light source in optical line terminal of wavelength division multiplexing-passive optical network.

基于传统OM2光纤的大容量模分复用传输系统研究

基于传统多模光纤的模式资源,来构建多维复用超大容量光纤传输系统可以有效提升通信系统传输容量,满足急剧增长的数据业务需求.在本文中,我们联合波分复用、偏振复用和模分复用技术,基于传统OM2光纤实现了40个波长信道(1 535.04~1 566.31 nm)×2个模式信道(LP01和LP11b)的60 G波特偏分复用16阶正交幅度调制(Polarization Division Multiplexing 16-ary Quadrature Amplitude Modulation,PDM-16QAM)信号的短距模分复用相干光传输.整个模分复用链路由一对基于多平面光转换(Multi Plane Light Conversion,MPLC)的模式复用/解复用器和20 m OM2光纤构成.由于高模式隔离度的模式信道特性(<-20 dB),本系统无需相应数字信号处理算法进行模式解复用,而仅需2×2的多输入多输出(Multiple Input Multiple Output,MIMO)算法完成偏振解复用.在实验中,除了对系统关键参数,包括脉冲成型滤波器的滚降因子、削峰比及接收光功率进行了优化外,还引入了Volterra判决反馈均衡方案.该均衡方案不仅能够补偿调制器引入的非线性信号损伤,而且能够缓解前馈均衡方案导致的高频噪声增强问题.最终,实验结果显示所有80个信道的误码率皆低于20%软判决前向误码纠错(Soft Decision Forward Error Correction,SDFEC)阈值2.7×10-2,系统总容量达38.4 Tbit/s,表明基于多模光纤的模式复用相干光传输方案在未来超大容量短距光互联系统中具有应用潜力.

O波段硅基二氧化硅密集波分复用AWG设计及制备

O波段波分复用器是数据中心高速互连关键器件,采用相对折射率差为0.75%的硅基二氧化硅光波导材料,设计并制备了O波段48通道平顶型密集波分复用阵列波导光栅芯片,采用金属合金架固定阵列波导光栅芯片,金属螺杆随温度变化收缩或伸张,可补偿阵列波导光栅芯片响应谱波长随温度产生的飘移,实现-5℃到65℃温度范围内响应谱稳定输出,采用非归零和4电平信号两种调制方式进行高速信号传输。测试结果表明,封装后的阵列波导光栅的插入损耗在-5.31~-6.59 dB之间,通道间隔0.676 nm,1 dB、3 dB带宽分别为0.41 nm、0.55 nm,相邻串扰、非相邻串扰分别为29.4 dB、29.2 dB,偏振相关损耗小于0.67 dB,-5℃到65℃变温下中心波长漂移由7 pm/℃减小到0.6 pm/℃,26.56 Gbps非归零及53.12 Gbps 4电平信号调制传输眼图消光比分别大于5.5 dB和3.6 dB。

用于光交换的硅基二氧化硅AWGR的设计与研究(特邀)

【目的】以N×N矩阵形式构成的阵列波导光栅路由器(AWGR)具有光学并行和波长路由能力,能在不同信道上同时传输N路信号,具有扩展性好、延时低和频带宽等优势,结合可调谐光源能实现快速光交换,是下一代光交换数据中心网络的潜在技术方案之一。为了解决现有AWGR在实际应用中存在的串扰大、有额外耦合损耗、偏振敏感和损耗非均匀性大等问题,进一步扩大数据中心规模和提升数据交换速度,文章分别对4×4和12×12通道的AWGR进行了研究。【方法】文章通过仿真软件进行基本设计参数的计算,分析研究了AWGR设计流程,并采用光束传播法(BPM)进行了仿真模拟。同时,采用在平板波导和条形波导连接处加入锥形波导taper结构和增大输入、输出波导间距等方法进行了性能优化。【结果】仿真结果得到良好的性能参数:4×4 AWGR插入损耗为-0.714 dB,串扰为-35.556 dB,损耗非均匀性为1.907 dB;12×12 AWGR插入损耗为-0.294 dB,串扰为-36.019 dB,损耗非均匀性为3.428 dB。文章制作设计器件流片并进行了性能测试,结果表明:4×4 AWGR插入损耗为-2.586 dB,串扰为-29.473 dB,损耗非均匀性为1.921 dB;12×12 AWGR插入损耗为-3.692 dB,串扰为-23.874 dB,损耗非均匀性为3.873 dB。【结论】文章的研究在串扰和损耗非均匀性等方面进行了性能优化,为后续设计迭代和进一步提升性能参数积累了经验。

燃煤锅炉高温腐蚀气体激光在线监测设备研究

燃煤锅炉燃烧场的经济性、安全性和环保性对于智慧电厂建设具有重要意义。H2S和CO是燃煤锅炉燃烧场的两种主要高温腐蚀气体,它们不仅腐蚀锅炉近壁面,尾气对大气环境的危害也极其严重。基于近红外可调谐半导体激光吸收光谱技术,结合波长调制光谱技术和频分复用技术,研制了一款无人值守的燃煤锅炉主燃区的H_(2)S和CO气体浓度实时在线监测设备。仿真模拟了6335~6341 cm^(-1)范围内的气体吸收光谱,并选定1.5μm附近的近红外激光器作为激光光源。研制了一套耐高温耐腐蚀的Herriott型多光程池,使激光与气体相互作用的有效光程达15 m;开发了硬件电路及相应的固件程序,实现了H2S和CO吸收光谱信号的二次解调与浓度反演。线性度和Allan方差实验表明,其线性拟合相关系数分别为0.9998和0.9995,在73 s和53 s的积分时间下,H_(2)S和CO的最低检测极限分别为0.2×10^(-6) mol/mol和0.344×10^(-6) mol/mol。最后,将研制的设备在某300 MW电负荷的四角切圆燃煤锅炉主燃区燃烧气氛场进行应用示范,对水冷壁附近的H2S和CO进行同步测量。结果表明,锅炉中H2S和CO的浓度呈正相关,厌氧燃烧会导致两种气体的含量增加,造成对水冷壁的腐蚀。