对我国下一代网络技术的若干战略思考

通信网和互联网都是由传输和交换两部分组成,目前传输已经完成了由电到光的革命性的转变,但交换仍然是电的交换。根据分布式网络的设计理念,本文提出了新型的分布式波分、纤分复用光路交换的信息流量极大的下一代网络结构。它将从结构上解决网络的安全问题。

S-band gain flattened distributed fiber Raman amplifier with chirped fiber bragg grating filter

S-band gain flattened distributed fiber Raman amplifier with a bandwidth from 1 488 nm to 1 541 nm （53 nm in width） ,an averaged gain of 10 dB and a gain ripple of ±0.6 dB is obtained successfully, in which a single-wavelength high power fiber Raman laser with wavelength of 1 427.2 nm is used as the pump and the chirped fiber Bragg grating is used as the gain flattening filter. Besides,filter wavelength division multiplexer（FWDM） is used as the multi-signal multiplexer and 1 427 nm/1 505 nm coarse wavelength division multiplexer（OWDM） is used as the pump-signal coupler. The gain media are G652 fiber of 50 km in length and dispersion compensation fiber（DOF） of 5 km in length. Moreover, the location arrangements of different type of fibers and the effect caused by gain flattening filter as well as their solutions are discussed in detail. It is very significant to extend the range of optical fiber communication band and increase the capacity of fiber communication especially for ultra-long haul and ultra-high capacity communication system.

Performance Analysis of Medium Access Control Protocol for IEEE 802.11g-over-Fiber Networks

This paper investigates the Medium Access Control(MAC)protocol performance in the IEEE 802.11g-over-fiber network for different payloads and fiber lengths using Direct Sequence Spread Spectrum-Orthogonal Frequency Division Multiplexing(DSSSOFDM)and Extended Rate PhysicalsOrthogonal Frequency Division Multiplexing(ERP-OFDM)physical layers using basic access mode,Request to Send/Clear to Send(RTS/CTS)and CTS-to-self mechanisms.The results show that IEEE 802.11g-over-fiber network employing the ERP-OFDM physical layer is much more efficient than that employing the DSSS-OFDM physical layer,with regards to both throughput and delay.For a given maximum throughput/minimum delay,the tradeoff among the access mechanism,the fiber length,and the payload size must be considered.Our quantified results give a selection basis for the operators to quickly select suitable IEEE 802.11g physical layers and the different access mechanisms,and accurately predict the data throughput and delay given the specific parameters.

Two-function light source in a FBG multi-point sensing system

In this paper,a two-function light source is recommended. It can both amplify the light power and demodulate the wave-length signal. Its output power is 1000 times as high as traditional broadband light source(BBS) and it can demodulate the signal by scanning wavelength in 30 nm of bandwidth range in the situation of 1550 nm central wavelength. This kind of light source effectively solves the problem of light energy supply in more-point measurement of FBG and simplifies the structure of sensing measurement.

Differentiating QoS and Un-conflicting Channel-times lot Allocation Algorithm in WDM

A new effective and reliabl e channel-timeslot allocation algorithm has been proposed, which is applied in WD M optical networks using fiber as their media to allocate the operational reques t. This new algorithm can differentiate the priority of all requests and avoid c onflict and collision in the process of distributing channel and timeslot for th e data waiting for transmission. The method in calculating the best wavelength c hannel and the best timeslot number is simply given. The algorithm is carried o ut in a math language. On the basis of the experiment results, the performance a nd feasibility of the algorithm are analyzed, which prove that the allocation me thod can reach the requirements of an algorithm both in space complexity and tim e complexity .

Transmission Characteristics of Sagnac Loop with Fiber Bragg Grating

A transmission filter composed of a Sagnac loop and a fiber Bragg grating is studied in detail. It is found that the transmission spectrum of this filter is the splitting of the reflection spectrum of the fiber Bragg gratings. The filter can behave as a multiple-passband filter when the fiber Bragg grating is strong and as a single-band filter when the fiber Bragg grating is weak. Very narrow transmission filters can be Obtained in this way.

Design and Realization of Uniform Fiber Bragg Grating Used in Dense Wavelength Division Multiplexing Systems

Relation of optical properties in a uniform fiber Bragg grating(FBG) with its grating parameters and the laser beam engraving conditions is analyzed. The principle and method for designing the uniform FBG used in dense wavelength division multiplexing(DWDM) system is given. By adopting the double exposure technique, with a uniform phase mask and Gaussian laser beam, the uniform FBG used in DWDM system is designed and engraved, whose bandwidth of the main reflection band is about 0.4 nm and 0.7 nm at -5 dB and -25 dB respectively.

Special Apodized Fiber Bragg Grating for Flat-top Band-pass Reflectivity Filter

The characteristics of special apodized fiber Bragg grating (FBG) in flat-top pass-band as reflectivity filter are presented. This special apodized FBG was designed by the particle swarm optimization algorithm. Compared with conventional apodized FBG, the special apodized FBG presented was more robust in the flat-top pass-band characteristic even if the strength of grating is very week. This technology is very interesting in designing the filter for wavelength division multiplexing system.

Influence of EDFA's Characteristics on Performance of All Optical Network

The characteristic of EDFA in WDM system is analyzed. The simulation system based on the architecture of the China Information Network (CAINONET) is introduced, and the influence of noise figure, gain unflatness and output power of EDFA on the BER performance and scale of network is investigated. Moreover, the influence of noise figure is studied with different crosstalk . Meanwhile, it is indicated that it is important to apply the "node isolation principle" in the optical network. The research results can provide the valuable reference for the practical construction of all optical network .

Performance Analysis of Optical Transmission Based on Seven Cores Fiber

This essay designed a kind of new seven-core fiber with lower crosstalk and loss, and made space division multiplexing transmission experiment based on this seven-core fiber. It is known that crosstalk has the most serious influence in multicore fiber transmission process. Before the experiment, the affecting factors of fiber crosstalk were analyzed through simulation, such as core space, bending radius, and fiber length. Combined with the simulation analysis, the design scheme of multicore fiber with low crosstalk was obtained. Before the fiber design, various factors of influence crosstalk such as the core- to-core distance, bending radius, fiber length and so on. Based on the simulation analysis, conclusion has made on the design scheme of multi-core optimal fiber with low crosstalk. The space division multiplexing and wavelength division multiplexing technology, was adopted to conduct seven-core optical fiber transmission of 58.7kin.The crosstalk of adjacent core was suppressed to as low as 45dB / km, the attenuation of inner core was 0.24dB/ km, the outer cores＇ 0.32dB/km. Different bit error rate （BER） performances were also studied under different conditions, through reasonably designing the system to reduce the error rate, improve the performance of the system, and realize long distance and large capacity transmission with fiber.

Optimization of Apodized Chirped Fiber BraggGrating for Dispersion Compensation

Multiwavelength chirped fiber Bragg grating (MCFBG) is a more valuable approach to chromatic dispersion compensation. And adjusting the structure of FBG will optimize the performance of dispersion compensator in 8×10 Gb/s DWDM network, which is proved by simulating calculation.

Analysis of Optical Signal Transmission Characteristics in AWG Multi/Demultiplexer with Electromagnetic Field Theory

Based on the electromagnetic field theory, the optical signal transmission characteristics in input/output waveguides, slab waveguides and arrayed waveguides of the arrayed waveguide grating (AWG) multi/demultiplexer are analyzed. The relationship between the physical parameters such as geometry sizes and relative refractive index in AWG multi/demultiplexer and the optical signal transmission characteristics are discussed. This theoretical study can be used for optimizing the design and improving the performance of the AWG multi/demultiplexer.

Mean Field Method with Different Dispersion Maps for WDM Systems

Using mean field method proposed in Ref. [4], the 40 Gb/s multi ― channelWDM optical fiber transmission systems with different dispersion maps are simulated. By this method,the computation time can be greatly reduced since following only the full time evolution of alimited number of channels while treating the other channels as continuous wave. But sincedispersion plays an important role in the process of FWM and XPM, different dispersion maps willaffect the application of the method. The dependence of the method on dispersion maps isinvestigated. The results not only confirm the mean field method, but also give useful approach forsystem design.

Numerical analysis of intermodal delay in few-mode fibers for mode division multiplexing in optical fiber communication systems

In order to achieve higher spectral efficiency, mode division multiplexing (MDM) in few-mode fibers is a new research area. The idea faces lots of technical issues including intermodal delay and mode coupling which limit the achievable length of the system. This paper is designated to complete the analysis of intermodal delay in step-index few-mode fibers. We analyze numerically all the parameters of fiber, which could impact intermodal delay in few-mode fibers and identify the conditions which can increase the number of multiplex modes without significant increase in maximum intermodal delay.

Rectangular optical filter based on high-order silicon microring resonators

The rectangular optical filter is one of the most important optical switching components in the dense wavelength divi- sion multiplexing （DWDM） fiber-optic communication system and the intelligent optical network. The integrated high- order silicon microring resonator （MRR） is one of the best candidates to achieve rectangular filtering spectrum re- sponse. In general, the spectrum response rectangular degree of the single MRR is very low, so it cannot be used in the DWDM system. Using the high-order MRRs, the bandwidth of flat-top pass band, the out-of-band rejection degree and the roll-off coefficient of the edge will be improved obviously. In this paper, a rectangular optical filter based on high- order MRRs with uniform couplers is presented and demonstrated. Using 15 coupled race-track MRRs with 10 pm in radius, the 3 dB flat-top pass band of 2 nm, the out-of-band rejection ratio of 30 dB and the rising and falling edges of 48 dB/nm can be realized successfully.

A full-duplex optical access system with hybrid 64/16/4QAM-OFDM downlink

A full-duplex optical passive access scheme is proposed and verified by simulation, in which hybrid 64/16/4-quadrature amplitude modulation(64/16/4QAM) orthogonal frequency division multiplexing(OFDM) optical signal is for downstream transmission and non-return-to-zero(NRZ) optical signal is for upstream transmission. In view of the transmitting and receiving process for downlink optical signal, in-phase/quadrature-phase(I/Q) modulation based on Mach-Zehnder modulator(MZM) and homodyne coherent detection technology are employed, respectively. The simulation results show that the bit error ratio(BER) less than hardware decision forward error correction(HD-FEC) threshold is successfully obtained over transmission path with 20-km-long standard single mode fiber(SSMF) for hybrid downlink modulation OFDM optical signal. In addition, by dividing the system bandwidth into several subchannels consisting of some continuous subcarriers, it is convenient for users to select different channels depending on requirements of communication.