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.

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.

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.

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.

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.

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.

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.

Real-Time Upstream Services Demonstration in Orthogonal Frequency Division Multiplexing- Passive Optical Network System

In recent years,dual-homed topologies have appeared in data centers in order to offer higher aggregate bandwidth by using multiple paths simultaneously.Multipath TCP(MPTCP) has been proposed as a replacement for TCP in those topologies as it can efficiently offer improved throughput and better fairness.However,we have found that MPTCP has a problem in terms of incast collapse where the receiver suffers a drastic goodput drop when it simultaneously requests data over multiple servers.In this paper,we investigate why the goodput collapses even if MPTCP is able to actively relieve hot spots.In order to address the problem,we propose an equally-weighted congestion control algorithm for MPTCP,namely EW-MPTCP,without need for centralized control,additional infrastructure and a hardware upgrade.In our scheme,in addition to the coupled congestion control performed on each subflow of an MPTCP connection,we allow each subflow to perform an additional congestion control operation by weighting the congestion window in reverse proportion to the number of servers.The goal is to mitigate incast collapse by allowing multiple MPTCP subflows to compete fairly with a single-TCP flow at the shared bottleneck.The simulation results show that our solution mitigates the incast problem and noticeably improves goodput in data centers.

Fluorinated polymer with high thermal stability for fabrication of 32-channel arrayed waveguide grating multiplexer on silicon

A cross-linkable fluorinated poly (ether ether ketone) (FPEEK) was synthesized for the fabrication of arrayed waveguide grating (AWG) multiplexer. The results of thermal gravimetric analysis (TGA) and near-infrared absorption spectrum show that the materials have high thermal stability and high optical transparency in the infrared communication region. The refractive index of FPEEK can be controlled easily by changing the fluorine content of the materials. The 32-channel AWG multiplexer is fabricated using the FPEEK and oxygen reactive ion etching technology. The AWG multiplexer exhibits that the insertion loss is from 12.8 to 17.8 dB and the channel crosstalk is less than-20 dB. The wavelength channel spacing and the center wavelength are 0.8nm and 1548nm, respectively.

基于光开关阵列的灵活TWDM-PON系统研究

为了满足接入网日益增长的业务流量需求,解决当前因架构固定、资源维度有限而导致的不同无源光网络之间波长无法灵活分配的的问题,提出了一种将发射固定波长的激光器与光开关阵列组合的时分波分混合复用无源光网络结构。在这种新的系统结构中,下行波长资源被集中化处理,采用在局端配置光开关阵列的方法实现波长在不同网络之间的灵活调度,降低系统总体成本的同时能够用来解决负载平衡、流量“潮汐效应”、网络资源利用率低下等问题。通过理论分析和仿真实验验证了系统的可行性,得出该结构与传统无源光网络的兼容性、波长资源的共享性、系统低成本以及节能的特点。结果表明,在没有色散补偿的情况下,信号可以覆盖30 km的传输距离,同时服务512个用户。该研究可以为典型应用场景下的无源光网络部署提供参考。

基于外部气相沉积的S+C+L波段低色散斜率大有效面积非零色散位移光纤的设计与制备

针对现有光纤无法满足宽带光密集波分复用系统传输和S+C+L波段粗波分复用的要求,设计了一种具有中心凹陷的三角形芯+环形的折射率剖面,利用外部气相沉积工艺制备了一种非零色散位移光纤,并通过调整第一芯层的相对折射率和第二芯层与第一芯层的半径比,探究了其对光纤衰减、色散斜率和有效面积等参数的影响。研究发现,当第一芯层的相对折射率逐渐增大且第二芯层与第一芯层半径比逐渐减小时,零色散波长和有效面积逐渐减小。当第一芯层的相对折射率在0.52%~0.53%,芯层半径比在2.6~2.7时,光纤的有效面积接近70μm^(2),零色散波长在1420 nm附近,在1550 nm波段的色散系数大于8 ps·nm^(-1)·km^(-1),色散斜率为0.059 ps·nm^(-2)·km^(-1),可以较好地抑制传输过程中光非线性效应,满足长途干线网与城域网的使用要求。

WDM技术在医院院间互联的应用

近年来,随着各大医院新院区的建设,医院对院间网络互联的带宽、运营成本、灵活可扩展性和自主可控性等提出了较高要求。然而,传统的运营商专线或祼纤无法满足带宽需求和成本控制等多方面要求。结合重庆医科大学附属儿童医院(以下简称“重医儿童医院”)两江院区和渝中院区的院间互联传输建设实践,深入探讨使用波分复用(Wavelength Division Multiplexing,WDM)技术在院间传输网络的建设思路和重点环节,以期为医院同行提供借鉴与参考。

基于多窗口识别的多波长光信号峰值实时检测系统

波分复用(Wavelength Division Multiplexing,WDM)作为光纤通信系统的核心技术之一,为多个波长光信号的复用和传输提供了强有力的解决方案,对复用光信号的解复用和识别是WDM系统需解决的重要问题之一。文中研制了一种针对多波长光信号峰值的实时检测系统,用于实时检测多波长光信号的峰值功率。首先,设计并研制了光纤法布里-珀罗可调谐滤波器(FFP-TF)的驱动控制器和微弱光信号探测器,分别控制FFP-TF的驱动电压使其滤出特定波长的光信号和对滤出光信号的功率进行实时探测;其次,对于光电探测器中实时探测的光信号功率,设计了一种基于多窗口识别的峰值检测方法,使用三个针对波形不同位置的数据筛选窗口,根据实时检测数据来识别波形的变化趋势从而得到峰值强度与位置,进而计算出对应的光信号峰值强度。实验结果显示,所研制的实时检测系统实现了对多波长光信号的实时检测以及峰值的识别,光信号检测强度范围为0~-60 dBm,识别速度较快,对于准周期或周期的多波长光信号的识别具有良好的识别效果。

一种远距离射频光纤传输性能补偿优化方案

远距离射频光纤传输具有轻量化、低传输损耗、抗电磁干扰能力强等优势,已广泛应用于很多领域。为解决远距离射频光纤传输信号谐波高、动态范围小等问题,提出一种性能补偿优化方案。该方案可以有效解决底噪升高、信号相位偏移、幅相特性改变等问题,具有一定的应用价值。

高速铁路5G网络覆盖方案的对比研究

随着高铁技术的迅猛发展,乘客对网络舒适性和连接速度的要求不断提高,尤其是对高铁、隧道等特殊应用环境。通过深入研究5G网络在高速铁路通信中的应用,探讨不同覆盖方案的基本原理与特点,包括微基站技术、波分复用技术、重叠覆盖技术及智能天线技术。在对比分析不同方案的基础上,突出覆盖范围、数据传输速度、可靠性与连通性方面的差异。深入讨论选择最佳覆盖方案和实施5G网络的关键步骤与挑战,包括基础设施规划、设备选择与配置、网络部署以及面临的成本和技术挑战,为高速铁路5G网络的未来发展提供实质性的指导和启示。

Optical multiplexing techniques and their marriage for on-chip and optical fiber communication:a review

Herein,an attention-grabbing and up-to-date review related to major multiplexing techniques is presented which in-cludes wavelength division multiplexing(WDM),polarization division multiplexing(PDM),space division multiplexing(SDM),mode division multiplexing(MDM)and orbital angular momentum multiplexing(OAMM).Multiplexing is a mech-anism by which multiple signals are combined into a shared channel used to showcase the maximum capacity of the op-tical links.However,it is critical to develop hybrid multiplexing methods to allow enhanced channel numbers.In this re-view,we have also included hybrid multiplexing techniques such as WDM-PDM,WDM-MDM and PDM-MDM.It is prob-able to attain N×M channels by utilizing N wavelengths and M guided-modes by simply utilizing hybrid WDM-MDM(de)multiplexers.To the best of our knowledge,this review paper is one of its kind which has highlighted the most prom-inent and recent signs of progress in multiplexing techniques in one place.

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.