Search

【Objective】With the continuous emergence of information-based bandwidth-consuming services such as 5th Generation Mobile Communication Technology (5G), the Internet of Things, and cloud computing, people’s demand for high-speed information transmission has increased dramatically. However, due to the inherent nonlinear effects, the transmission capacity of single-mode optical fiber has approached the Shannon limit, and it will no longer be able to meet people’s needs for ultra-high-speed and large-capacity transmission. Solving the transmission capacity problem has become a top priority. In order to solve the needs of large-capacity communication systems and long-distance high-speed transmission problems, we have built a two-mode single-channel C-band Few Mode Fiber (FMF) transmission system.【Methods】At the transmitting end, an arbitrary waveform generator is used to convert the digital signal into an electrical signal and drive the In-phase and Quadrature (IQ) modulator to modulate the optical carrier. The modulated signal is transmitted simultaneously using two multiplexing technologies: Mode Division Multiplexing (MDM) and Polarization Division Multiplexing (PDM). In order to achieve long-distance transmission of dual-mode signals of 1 000 km, we construct a dual-circulation loop system. Each time the signal passes through the loop, it will pass through a 50 km FMF. After being transmitted to the target distance, the coupler outputs the signal to the demultiplexing module, and the coherent optical receiver performs homodyne detection on the demultiplexed modulated signal. Finally, the transmitted signal is stored in an oscilloscope for offline Digital Signal Processing (DSP). The signal is sequentially subjected to frequency domain dispersion compensation, downsampling, clock recovery, and least mean square algorithm to restore the original signal.【Results】It was found that within the range of Optical Signal-to-Noise Ratio (OSNR) of each channel in the experiment, the Bit Error Rate (BER) under low Signal to Noise Ratio (SNR) is close to the theoretical channel result. Under high SNR condition, the BER is 1×10-2, which is 2.5 dB away from the theoretical value. We test the BER of LP11a and LP11b modes at Back-To-Back (BTB) and 250, 500, 750 and 1 000 km transmission cases respectively. The BER at all distances are lower than the Low-Density Parity-Check (LDPC) soft decision threshold with 28% redundancy (5.2×10-2 Soft Decision - Forward Error Correction (SD-FEC)). The BER after 1 000 km transmission in the two modes are 1.7×10-2 and 1.8×10-2 respectively, and the total net transmission rate is 400 Gbit/s.【Conclusion】This article demonstrates the transmission of a 32 Gbaud MDM-PDM-16 Quadrature Amplitude Modulation (QAM) C-band signal in a 1 000 km two-mode single-channel FMF system. At the receiving end, the advanced Multiple Input Multiple Output (MIMO)-DSP algorithm is used for channel equalization, and the obtained two-mode BER of 1.7×10-2 and 1.8×10-2 are both lower than the LDPC SD-FEC threshold with 28% redundancy. The result reachs a domestic record of 400 Gbit/s net transmission rate based on FMF transmission, and highlight the potential of FMF in large-capacity long-distance transmission.

To address the high-cost issue of twin single sideband quadrature phase shift keying (Twin-SSB-QPSK) signals in optical transmission, a optical fiber communication system was proposed, in which a single photodetector (PD) was employed at the receiver to directly detect the Twin-SSB-QPSK signals. At the receiver end, optical bandpass filter (OBPF) was not required to separate the two optical single sideband signals of the Twin-SSB-QPSK signal. Instead, the heterodyne effect of direct detection was utilized, allowing a single PD to directly detect the coherent superposition of the twin two optical single sideband QPSK signals, resulting in a single 16-ary quadrature amplitude modulation (16QAM) signal. Simulations demonstrated that two 56 Gbit/s QPSK signals were combined into a single 112 Gbit/s 16QAM signal and then compared with the traditional single 16QAM signal transmission scheme. The simulation results indicate that the proposed scheme does not introduce additional power penalties while reducing the system device requirements and deployment costs.

Copyright of Study on Optical Communications / Guangtongxin Yanjiu is the property of Study on Optical Communications Editorial Office and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

With the increasing use of optical fiber communication technology in the Industrial Internet of Things, cryptographic algorithms play a crucial role in ensuring the security of data transmission in embedded device environments.The SM4 packet cipher algorithm, developed independently in our country, is widely applied to wireless LAN and Internet of Things data encryption.However, the software-based encryption and decryption processes are relatively slow, which hampers their application in scenarios requiring high real-time performance, especially for embedded devices.To address this issue, a high-performance and secure optical fiber communication system was designed based on the FPGA platform and the SM4 algorithm.The FPGA was used to implement the MAC layer interface for SM4 algorithm encryption and decryption, as well as data transmission.Besides, an optimization scheme for the hardware implementation architecture of the SM4 algorithm was proposed.The critical path was shortened by employing a pipeline method, thereby improving the system clock frequency.Additionally, parallel processing of S-box transformation was accelerated to enable efficient data replacement.To reduce data reading delays, a dual-cache processing method was combined to facilitate easier processing of cache data and significantly reduce packet loss rates.This scheme greatly enhanced system data throughput.Experimental results demonstrate that compared to similar designs, the throughput of the SM4 algorithm encryption and decryption module in this scheme reaches up to 25.6 Gbit/s, with minimal differences in resource consumption.Due to limitations imposed by the 10-gigabit SFP+ optical module, the throughput of the entire optical fiber communication system reaches 9.4 Gbit/s.For 128-bit data, the average encryption speed is 0.47 μs/bit and the average decryption speed is 0.28 μs/bit, which can be applied to a variety of secure communication scenarios in the internet of things.

To meet the growing demand for communication capacity, new multi-carrier fiber optical communication technology has become the focus of scientific researchers' attention. The paper reviews the development process of traditional Orthogonal Frequency Division Multiplexing (OFDM) in the field of fiber optical communication in the past 20 years and summarizes the relevant research on Filter Bank Multi Carrier (FBMC) and Universal Filter Multi Carrier (UFMC) in recent years. Since 2016, many scholars at home and abroad have focused on the drawbacks of OFDM in optical communication, such as high out-of-band leakage, reliance on Cyclic Prefixes (CP), high Peak-to-Average Power Ratio (PAPR) values, and high system synchronization requirements. They have been researching new multi-carrier systems as a breakthrough point. FBMC optical communication has the characteristics of the lowest sidelobe power and high spectral efficiency, but due to the use of Offset Quadrature Amplitude Modulation (OQAM), the corresponding Digital Signal Processing (DSP) algorithm needs to be redesigned or virtual part interference. UFMC optical communication has a strong tolerance for time synchronization deviation, and it is insensitive to frequency offset. Moreover, it can reuse the DSP algorithms of OFDM. However, there are also issues such as how to further suppress out-of-band power and reduce computational complexity. Finally, based on the current research status, he paper proposes research directions and suggestions for the demands of the next-generation fiber optical communication system. [ABSTRACT FROM AUTHOR]

The deep integration of optical fiber communications and high-capacity high-frequency wireless communications is the core technology base of future The 6th Generation Networks(6G). It holds significant importance in building typical 6G scenarios such as "immersive communications, ubiquitous connectivity, and communications Artificial Intelligence (AI) integration". This paper introduces mainstream technologies and their implementation for optimizing the architecture and improving the spectral efficiency of fiber-wireless integrated transmission systems. We summarize some of the progress made by our team in these areas. First of all, facing the large-capacity demand for a new generation of immersive communications, we propose a novel architecture for seamless "fiber-wireless-fiber" integrated transmission system with the use of commercial Digital Coherent Optics(DCO). We firstly realize the photonics-assisted 100/200/400 GbE real-time THz wireless transmission, achieving a maximum line rate of 2X240. 558 Gbit/s. Secondly, for application scenarios with wide coverage and flexible deployment, Digital Sub Carrier Multiplexing (DSCM) technology was introduced into the optical fiber wireless converged access system. Our team designs and constructs a coherent Passive Optical Networks (PON) that supports up to 32 channel of fixed broadband access and 32 channel of W-band millimeter-wave wireless access. This coherent PON can reach the rate of 100 Gbit/s and is capable of flexible rate adjustments, facilitating subsequent iterative upgrades. Finally, in response to the demand for communication AI integration, our team proposes a likelihood-aware Vector-Quantization (VQ) Variational Auto Encoder (VAE) based on AI technology for end-to-end optimization of fiber-wireless integrated communication systems. Without the need for tera-hertz power amplifiers, we successfully demonstrate the wireless transmission of Dual-Polarization (DP) terahertz signal at a net rate of 366. 4 Gbit/s over 6.5 m 2 X 2 Multiple Input Multiple Output (MIMO) wireless link and 20 km Standard Single Mode Fiber (SSMF) link. The aforementioned technologies exhibit tremendous potential in typical future 6G scenarios. Besides, we briefly introduce our work in these areas, and provide an outlook on beyond 100 Gbit/s fiber-wireless integrated transmission technology from the perspectives of high capacity, long distance, integration and intelligentization. [ABSTRACT FROM AUTHOR]

Copyright of Chinese Journal of Network & Information Security is the property of Beijing Xintong Media Co., Ltd. and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

With the growth of network traffic, communication services have higher and higher requirements on the performance of Dense Wavelength Division Multiplexing (DWDM). In order to improve the transmission efficiency, the transmission spectrum gradually expands to the C+L band transmission, and Super C Band transmission emerges as the times require. In order to solve this problem, this paper proposes an Erbium-Doped Fiber Amplifier (EDFA) structure for Super C Band transmission. Based on the Giles model, the characteristics of the EDFA in Super C Band are analyzed. A multi-stage pumping mechanism is used to design an EDFA that amplify in the Super C Band range. The results show that the EDFA can achieve a flat gain of 26 dB and an output power of 16.7 dBm when the light is incident at -9.3 dBm. The noise figure is less than 5 dB, and the ripple is less than 0.1 dB. And according to the requirement, when the incident light is in the range of -15～-3.5 dBm, the adjustable gain of 7～26 dB can be achieved by adjusting the pump power and the value of Variable Optical Attenuator (VOA). The EDFA can be used in the area of 5G transmission, optical fiber communication between data centers, etc.

Copyright of Journal of Chongqing University of Posts & Telecommunications (Natural Science Edition) is the property of Chongqing University of Posts & Telecommunications and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Copyright of Industrial Minerals & Processing / Huagong Kuangwu yu Jiagong is the property of Industrial Minerals & Processing Editorial Office and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Copyright of Study on Optical Communications / Guangtongxin Yanjiu is the property of Study on Optical Communications Editorial Office and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

The optical transmission system based on all-band is considered to be one of the methods to effectively improve the transmission capacity of optical communication. In addition of the C and L bands, the using of other bands for transmission can fully tap the transmission potential of the existing optical fiber network and solve the bottleneck problem of large capacity communication network. The realization of its key technologies and systems is conducive to promoting the industrialization process of related technologies, which has broad economic benefits. This paper analyzes and discusses the current research status of multi-band optical transmission technology. And then as the focus, the performance difference of S、C and L band is studied by experiments. Based on the devices designed for C and L bands, the experiment of 40 km transmission system covering on S、C and L band is completed by using Polarization Division Multiplexed 16 Quadrature Amplitude Modulation (PDM-16QAM) modulation format, and the transmission capacity can reach 122.4 Tbit/s. The multi-band transmission capability of G. 652.D optical fiber is verified, which provicles an experimental basis for further research on multi-band optical transmission technology.

The optical transmission system based on all-band is considered to be one of the methods to effectively improve the transmission capacity of optical communication. In addition of the C and L bands, the using of other bands for transmission can fully tap the transmission potential of the existing optical fiber network and solve the bottleneck problem of large capacity communication network. The realization of its key technologies and systems is conducive to promoting the industrialization process of related technologies, which has broad economic benefits. This paper analyzes and discusses the current research status of multi-band optical transmission technology. And then as the focus, the performance difference of S、C and L band is studied by experiments. Based on the devices designed for C and L bands, the experiment of 40 km transmission system covering on S、C and L band is completed by using Polarization Division Multiplexed 16 Quadrature Amplitude Modulation (PDM-16QAM) modulation format, and the transmission capacity can reach 122.4 Tbit/s. The multi-band transmission capability of G. 652.D optical fiber is verified, which provicles an experimental basis for further research on multi-band optical transmission technology.

Copyright of Study on Optical Communications / Guangtongxin Yanjiu is the property of Study on Optical Communications Editorial Office and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Copyright of Study on Optical Communications / Guangtongxin Yanjiu is the property of Study on Optical Communications Editorial Office and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Copyright of Study on Optical Communications / Guangtongxin Yanjiu is the property of Study on Optical Communications Editorial Office and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

In the process of anti-interception of information, due to the weak control ability of data nodes, data is easily lost and information security is not high. An anti-interception method of optical fiber communication physical layer based on chaotic mapping is studied. The existence of the intercepted signal is determined by optical fiber signal detection and identification, and the ciphertext matrix is constructed based on the chaotic map encrypted image. The physical layer communication code is jointly transmitted to realize the information exchange between the receiver side and the transmitter side. We establish the anti-interception model of the communication physical layer to achieve the goal of anti-interception of the optical fiber communication physical layer. In the constructure of optical fiber communication network, a set of images with practical significance are selected as test samples. The proposed method and the traditional method are used for comparison. The experimental results show that the image data can be fully encrypted based on the proposed method. It has strong anti-interception performance, and the data information in the image can be retained in the image transmission, However, the traditional method loses 15 groups and 12 groups respectively, indicating that the proposed method has better performances.

Copyright of Experimental Technology & Management is the property of Experimental Technology & Management Editorial Office and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Copyright of Study on Optical Communications / Guangtongxin Yanjiu is the property of Study on Optical Communications Editorial Office and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Copyright of Study on Optical Communications / Guangtongxin Yanjiu is the property of Study on Optical Communications Editorial Office and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Spatial division multiplexing based on the multi-core fiber has been believed as a promising and effective way to overcome the foreseeable capacity crunch of single mode fiber transmission. Fan-in Fan-out (FIFO) technology for multi-core fiber is the key to realize multi-core fiber space division multiplexing system, which can realize the optical coupling function from single multi-core fiber to multiple single core fiber. In this paper, we summarize the methods of multi-core fiber FIFO devices in the past decade, which includes fused type, fiber bundle type, free space type and three-dimensional integrated waveguide type. The fabrication methods and performance of several types of devices are analyzed and compared. Finally, the technology direction which can be widely used in the future is prospected.

The development of optical fiber communication system was reviewed and the demand and possible solutions of optical fiber communication technology in the next 20 years were introduced by reviewing the development of optical fiber communication system in the past 20 years and the current research status of “ultra-high speed,ultra-large capacity and ultra-long distance” optical fiber communication system.

Copyright of Journal of Chongqing University of Posts & Telecommunications (Natural Science Edition) is the property of Chongqing University of Posts & Telecommunications and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Copyright of Chinese Journal of Liquid Crystal & Displays is the property of Chinese Journal of Liquid Crystal & Displays and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Copyright of Study on Optical Communications / Guangtongxin Yanjiu is the property of Study on Optical Communications Editorial Office and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Copyright of Journal of Dalian Polytechnic University is the property of Journal of Dalian Polytechnic University Editorial Department and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Copyright of Ordnance Industry Automation is the property of Editorial Board for Ordnance Industry Automation and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

According to the teaching mode of optical fiber communication experiment course, the experiment is just only conducted by using the experimental box. We presented to use software to construct a simulation experiment platform. The simulation platform used the Matlab visual user interface and was designed by the experimental teachers and students together. Result shows that the design of the simulation platform has achieved good effects in the experiment teaching reform, which enables students to better understand the performance parameters of optical fiber communication, optical fiber correlation characteristics and the use of optical fiber communication devices. It has also stimulated the students' learning interest and improved the teaching quality. [ABSTRACT FROM AUTHOR]

The evolution of optical fiber communication technology is driven by the ceaseless growth of capacity demand of Internet.Space division multiplexing (SDM) based on multi-core fiber,few-mode fiber,few-mode multi-core fibers and orbital angular momentum has become the focus of academy and industry.Key technologies and latest research progress were reviewed,including novel fiber design,spatial mode conversion,spatial channel de/multiplexing and optical amplification.Based on the comparison and analysis of four kinds of SDM technologies,their bottlenecks and potential future application were also discussed.

The development of optical fiber communication system was reviewed and the demand and possible solutions of optical fiber communication technology in the next 20 years were introduced by reviewing the development of optical fiber communication system in the past 20 years and the current research status of "ultra-high speed, ultra- large capacity and ultra-long distance" optical fiber communication system. [ABSTRACT FROM AUTHOR]

The rapid progress of optical fiber communication makes it become the key technology for the information society.The active and passive optoelectronic devices are the foundation of the optical communication.The progress and development trend of the key active optoelectronic devices were reviewed,including DFB laser,photonic integrated circuit,980 nm high power laser for EDFA pumping,compound semiconductor photodetector and Si-based long wavelength photodetector.

2016 is the 50th anniversary of Charles K Kao's proposing using optical fiber communication,the article was written to commemorate the review,in particular,the development review of China's optical fiber communication.Zhao zisen was one of the founders of Chinese optical fiber communication,the development of China's optical fiber communication was reviewed and the successful experiences and failure were absorbed.

Optical fiber communication system is one of the core supporting systems of the modern internet age.Firstly,major recent technological advances in optical fiber communication system were summarized.Then,the driving forces for its future development in the emerging cloud era,the future challenges and opportunities that it faced were analyzed.With the consideration of these challenges and opportunities,the future evolution paths in key areas such as optical fiber communication system overall network architectures,core network technologies,metro network technologies,access network technologiesand novel software-defined optical transport network technologies in the upcoming cloud erawere described,aiming to support future generations of internet,data center interconnect,internet of things and 5G mobile network,as well as the smart home and smart city initiativesmore effectively.

The development history of the optical fiber communication，internet，mobile communication and internet of things were reviewed. The features，typical system performances and key technologies of above systems and networks were analyzed. Based on these，the 5th generation of mobile internet was brought forward with the backgrounds，features，key performance indicators and candidate technologies. Parts of key technologies for supporting the 5th generation of mobile internet were analyzed in detai1. The future research directions of above technologies were also discussed. Finally，the related standard activities for the 5th generation of mobile internet were introduced.

The video optical transmitter and receiver experimental module reproduce a practical engineering equipment completely, and is used in the field of video fiber monitoring for the course of the optical fiber communication. Through developing the experimental teaching equipment which is based on the open video optical transmitter and video optical receiver, we put forward to guarantee the design experiment hours by the combination of curriculum design and experimental teaching, establish the college students' innovation team to help the teachers to open and manage the laboratory auxiliarily relying on the professional laboratory, establish the process experiment assessment system which is oriented by ability, adopt the ”1+1+3” teaching team model to guarantee the effect of experiment teaching by the whole process and progressive type. The practice proves that this experimental equipment and method are helpful for the students to master the software and hardware design methods of the optical fiber communication engineering instruments, there are also helpful for the students to cultivate the ability of designing and engineering practice, improve the students "ability of application and innovation, and has achieved remarkable teaching effect. [ABSTRACT FROM AUTHOR]

Copyright of Control Theory & Applications / Kongzhi Lilun Yu Yinyong is the property of Editorial Department of Control Theory & Applications and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

The femtosecond soliton for future large capacity and large data of optical fiber communication has become an important research direction, this paper established a soliton formation model when the standard single-mode fiber has wave collapse under noise environment. Analyzing results show that for pulses which is more than 200 ps, wave modulation instability mechanism can lead to disintegration of noise amplification even low noise power. When the pulse is shorter than 20 ps, a large number of soliton wave disintegrations appear due to the collapse of the pulse and pulse spectrum broadening. Between them the pulse wave collapse is mainly due to a lot of soliton pulses. The results of the pulse modulation have certain theoretical and practical significance to overcome fiber loss and nonlinearity. [ABSTRACT FROM AUTHOR]

A novel pre-coding scheme for modified optical duobinary signals was proposed.It could be applied to trans-mit high speed data rate signals（≥ 10Gbit/s）.Through analyzing the process of coding and decoding,It was demon-strated that modified optical duobinary signals have capability in reduction of pulse-to-pulse interaction,and could be di-rectly measured through a conventional binary intensity modulation direct detection（IM-DD） receiver.Two modified op-tical duobinary signals’ formats were simulated to generate.Simulation results show that MD-NRZ and MD-RZ signals’ formats can avoid the eye diagrams’ distortion for long-distance transmission,if the dispersion can be compensated in each amplifier span.Moreover,the MD-RZ signal has lower BER than the MD-NRZ signal after long-distance commu-nication.

A comprehensive design and a teaching method for communication experiment were developed in this paper based on wavelength division multiplexing (WDM) optical fiber transportation. The designed communication experimental equipment was combined by the ones used in other courses such as principle communication, optical fiber communication' program-controlled switching etc.' where the modules of signal generator and processing were distributed in different experimental instruments, the signals can be transferred via the WDM channels in optical fiber. The results indicate the integrated experiments can facilitate students to comprehensively understand the communication technology' to improve practical skills and to effectively grasp the key concepts in limited time. In addition' the designed experimental system will contribute to adjust the experimental items and to reform the theoretical teaching without extra fees. [ABSTRACT FROM AUTHOR]

Based on the SLA （service level agreement） in access network, the inherent deficiencies of two classical DBA algorithms: IPACT and Cyclic DBA in EPON to support multi-user types were analyzed. Two new Ethernet control frames: grant frame and request frame were introduced and a novel DBA algorithm supporting multi-user types SLA in EPON system: HPFCT （hierarchy polling with fixed cycle time） was proposed. The theoretical analysis and simulation results show that this algorithm meets the standard of various user types: satisfied delay and delay jitter performance of high priority services, and stable buffer size of all sorts of services. At the same time, HPFCT solves the downstream bandwidth waste problem of conventional algorithms.

The use of wavelength division multiplexing technology in the field of optical communication, greatly improved the transmission capacity and rate of system, realized the large capacity optical fiber transmission. Through the analysis of the principle of the WDM technology, the paper grasps the main performance parameters of the WDM. According to the design principle of the experimental circuit, the paper also combined with the design of the optical fiber communication transmiision transmitter and receiver circuit, designed and realized WDM in experiments in optical fiber communication. [ABSTRACT FROM AUTHOR]