共查询到20条相似文献,搜索用时 15 毫秒
1.
Ye Zhang Hongwei Chen Zhijian Si Heng Ji Shizhong Xie 《Photonics Technology Letters, IEEE》2008,20(11):891-893
A novel fiber Bragg grating (FBG)-based en/decoder for the two-dimensional (2D) time-spreading wavelength-hopping optical coding is proposed. Compared with other 2D en/decoders, the proposed en/decoding for an optical code-division multiple-access (OCDMA) system uses a single phase-encoded FBG and coherent en/decoding. Furthermore, combined with reconstruction-equivalent-chirp technology, such en/decoders can be realized with a conventional simple fabrication setup. Experimental results of such en/decoders and the corresponding system test at a data rate of 5 Gb/s demonstrate that this kind of 2-D FBG-based en/decoders could improve the performances of OCDMA systems. 相似文献
2.
Xiang-Gen Xia 《Communications Letters, IEEE》2002,6(4):150-152
In this letter, we propose a differential en/decoding scheme for Alamouti's orthogonal space-time code using amplitude/phase-shift keying (STC-APSK) signals and two transmit antennas. It is compared with the differential en/decoding scheme using 16APSK and single transmit antenna. It is also compared with the differential en/decoding scheme for Alamouti's orthogonal space-time code using 16PSK (STC-16PSK) signals and two transmit antennas. We find that the performance of the differentially en/decoded STC-APSK with 4.5 b/s/Hz is significantly better than that of the differentially en/decoded 16APSK with 4 b/s/Hz, and is almost the same as that of the STC-16PSK with 4 b/s/Hz over Rayleigh flat fading channels 相似文献
3.
提出一种新型的基于AWGs波导的采用扩展双曲同余码/素数码(EHLC/PC)结构的二维编/解码方案,并进行了计算机模拟,得到了二维EHLC/PC码的解码相关输出结果.结果表明:AWGs编解码器实现了二维EHLC/PC码字的编码和相关解码;在相同码长、码重的情况下,EHLC/PC码容量较大,可以实现更多用户的接入.此外,利用AWGs编解码器易于实现OCDMA编解码器的集成化. 相似文献
4.
Tao Pu Yingxun Zhu Peng Chen Xiangfei Chen Lin Lu Rong Wang Yuquan Li Jilin Zheng 《Photonics Technology Letters, IEEE》2007,19(22):1807-1809
Optical code-division multiple-access (OCDMA) technology is attractive for optical broadband access network. It is very interesting to use the super-structure fiber-Bragg-grating-based en/decoders to construct a wavelength-division-multiplexing (WDM)-compatible OCDMA system. Based on the equivalent phase-shift technique, we have proposed a subsampled-Bragg-grating (S-SBG)-based en/decoder. Based on the proposed method, only a single uniform phase mask can be used to accommodate different WDM channels with relevant central wavelengths and spectrum width. Using the S-SBG-based en/decoder, we can make different WDM channels have similar as well as better encoding efficiency and correlation performance. S-SBG-based en/decoders with 127 chips for two different wavelength channels are fabricated and measured. The experiments indicate the advantages revealed by the theoretical simulation. 相似文献
5.
基于等效相移超结构光纤光栅编解码器的2.5 Gbit/s 60 km光码分多址传输实验 总被引:6,自引:2,他引:4
稳定的窄脉冲光源、高性能编解码器和具有旁瓣/噪声抑制功能的接收机是光码分多址(OCDMA)系统设计实现的3个关键模块。实验中利用增益开关脉冲光源,63位等效相移超结构布拉格光栅(EPS-SSFBG)相位编解码器和接收机门限调整技术实现了2.5 Gbit/s 60 km传输并得到了相应的误码曲线,系统在误码率(BER)等于10-9时的灵敏度为-22.5 dBm。实验结果表明,等效相移超结构布拉格光栅编解码器兼具高性能和可实现性,可用于实用化的光码分多址系统,而综合利用光域和电域的手段抑制旁瓣和噪声的影响是提高系统性能的重要手段。 相似文献
6.
Meng Yan Minyu Yao Hongming Zhang Li Xia Ye Zhang 《Photonics Technology Letters, IEEE》2008,20(10):788-790
A novel en/decoder for spectral phase-coded optical code-division multiple-access system based on amplitude sampled fiber Bragg grating (FBG) is proposed. Both equivalent chirp and equivalent phase shift are achieved by amplitude sampling. Compared with previous en/decoder based on step chirped FBG, it is easier to fabricate. The performance of the proposed en/decoder is verified by both numerical simulation and experimental demonstration. 相似文献
7.
基于扩展二次同余码/单重合序列(EQC/OCS),利用光纤布拉格光栅(FBG)和光纤延迟线作为编解码器,对二维非相干光码分多址(OCDMA)系统进行系统仿真。通过软件仿真,实现了4个用户的EQC/OCS码字的解码相关输出结果。结果表明,低成本的FBG编/解码器实现了EQC/OCS码字的编码和相关解码,提高了二维OCDMA系统容量。 相似文献
8.
Wan-De Weng Wen Pin Yang 《Industrial Electronics, IEEE Transactions on》2001,48(5):898-903
Digital television has become one of the most promising industries. The advanced television system is scheduled to totally replace the current television broadcasting system in the US. In this paper, we present the implementation and discussion of the trellis en/decoder in the grand alliance digital television system proposed by the Advanced Television System Committee (ATSC). In the paper, we use a relatively efficient way to realize the en/decoding circuit. The correctness of our design has also been demonstrated 相似文献
9.
《Photonics Technology Letters, IEEE》2009,21(24):1795-1797
10.
基于超结构光纤光栅的混沌序列OCDMA系统 总被引:1,自引:1,他引:0
提出了一种双极性编解码的光码多分址(OCDMA)系统,采用混沌序列作地址码,并使用超结构光纤布拉格光栅(SSFBG)作编/解码器。三阶Chebyshev映射能够产生具有良好相关性且适用于异步CDMA系统的双极性混沌序列,通过对三阶Chebyshev映射赋予一定初值,并进行反复迭代,得到一定长度的双极性混沌序列。根据地址码的特征,通过控制FBG的折射率分布形成SSFBG,利用SSFBG产生相应的双极性混沌序列作OCDMA系统的编/解码器。对系统性能进行了定量分析,在完全异步的情况下,推导了信噪比(SNR)与误码率(BER)的表达式。仿真分析了系统在不同码长下的BER随接入用户数的变化,并和使用Gold序列的情况进行了比较。结果表明,随着码长的增加,在接入用户数一定的情况下,系统具有较低的BER;由于混沌序列良好的自互相关性,相应的混沌序列OCDMA系统与使用Gold序列的系统相比具有较低的BER,并可以容纳更多的用户数。 相似文献
11.
12.
OCDMA over WDM PON-solution path to gigabit-symmetric FTTH 总被引:3,自引:0,他引:3
It will be revealed that a myth of deploying low bit-rate uplink fiber-to-the-home (FTTH) services while providing a high bit-rate downlink is wrong. Therefore, for the future broadband FTTH services, the focus should be on the capability to provide gigabit- or even multigigabits-per-second both in up- and downlinks, namely gigabit symmetric systems. Optical code-division multiple access (OCDMA) now deserves a revisit as a powerful alternative to time-division multiple access and wavelength-division multiple (WDM) access in FTTH systems. In this paper, the authors will first highlight the OCDMA systems. The system architecture and its operation principle, code design, optical en/decoding, using a long superstructured fiber Bragg grating (SSFBG) en/decoder, and its system performance will be described. Next, an OCDMA over WDM passive optical network (PON) as a solution for the gigabit-symmetric FTTH systems will be proposed. The system architecture and the WDM interchannel crosstalk will be studied. It will be shown that by taking advantage of reflection spectrum notches of the SSFBG en/decoder, the WDM interchannel crosstalk can be suppressed and can enable OCDMA over WDM PON to simultaneously provide multigigabit-per-second up- and downlinks to a large number of users. 相似文献
13.
给出了DS-OCDMA系统的各组成部分的数学模型,并对OCDMA系统中的相干噪声产生的基理进行了介绍,在充分考虑了光编解码器中光器件温度特性的基础上,分析了相干噪声的原因,并仿真了其对系统的影响。从对光、电编解码器的仿真结果可看出,当使用电编解码器实现OCDMA时,相干噪声的影响可大大降低,甚至完全避免。 相似文献
14.
15.
张军英 《微电子学与计算机》1993,(5):5-8,26
本文基于控制理论中的状态空间方法,提出了一种设计加密器和解密器的方法.加密器没计为—个非线性能观系统,这种加密器在同等的安全强度情况下,较之传统的移位寄存器式加密器没计容易,计算复杂度低,加解密速度快,结构灵活,易于实现.本文还讨论了提高这种加密器性能的基本途径,并举了几个说明性例子说明这种加密器及其设计方法的可行性. 相似文献
16.
光码分多址(OCDMA)系统中,编解码器的性能是影响系统整体性能的关键因素之一,而波长漂移会影响编解码的性能.在分析等效相移超结构光纤光栅(EPS-SSFBG)作为光码分多址相位编解码器的基础上,仿真研究了不同码字、不同码长、不同编码带宽、不同编码效率和不同折射率调制深度的编解码器对波长漂移的容忍度(WDT).仿真结果表明,光源与编解码器之问的波长漂移容忍度较大;若光源脉宽相对较宽,光源的中心波长偏移编解码器的中心波长一定值时,解码输出的自相关峰旁瓣比(P/W)反而提高;不同码字、不同编码效率、不同折射率调制深度都会不同程度地影响波长漂移容忍度. 相似文献
17.
The solvo-thermal technique is used for the synthesis of [Mn(en)3]Te4 (I).The crystal structure has been determined by single crystal X-ray diffraction techniques.The crystal belongs to the monoclinic, space group p21/c with unit cell:a=0.8461(1),b=1.5653(2), c=1.4269(2)nm, α=90°,β=91.37(1) (3)°, γ=90°,V=1.8893(4)nm3,and Z=4.The results show that the structure contains a linear chain Zintl anion,[Te4]2-and a complex cation,[Mn(en)3]2+. Optical studies have been performed on the powder sample of I, suggesting that the compound is a semiconductor with a band gap of 0.73eV. The semiconductor properties for MnQ2(Q=S,Se,Te) and [Mn(en)3]Te4 have been discussed by molecular orbital theory. 相似文献
18.
BaTiO3 semiconductors show a strong dependence on pressure of the electrical resistance. The impedance behaviour reveals this piezo resistance effect to be mainly localized in the grain boundary barriers which are also responsible for the anomalous increase of the resistance above the Curie temperature. The dependence of the resistance on both the temperature and the stress near the Curie point may be explained by the height of the potential barriers which is ferroelectrically controlled.
Résumé
Les semiconducteurs en TiO3Ba démontrent une forte dépendance da la résistance électrique en fonction de la pression. Le comportement de l'impédance démontre que cet effet piézo-résistif est surtout localisé dans les barrières de reobrds de grain qui sont aussi responsables de l'augmentation anormale de la résistance au-dessus de la température Curie. La dépendance de la résistance en fonction de la température et de l'effort près du point Curie peut être expliquée par la hauteur des barrières de potentiel qui est contrôlée ferroélectriquement. 相似文献
19.
LIGuo-qiang HEXiao-yun ZHONGHuai-zhen CHENZhen 《半导体光子学与技术》2004,10(4):256-259,277,281
The precursore Zn(en)2 S (en=ethylenediamine) were prepared via a solvothermal process from elemental sulfur and zinc using ethylenediamine as a solvent. Detailed characterizations of the infrared (IR) absorption spectrum, powder X-- ray diffraction (XRD) and thermogravimetric analysis (TG) confirmed two en coordinated with Zn^2 to form a complex cation. The morphological property was also characterized by transmission electron microscopy (TEM) and electron diffraction analysis (ED). Phase—pure hexagonal wurtzite ZnS products were obtained by annealing the precursor in nitrogen stream at about 900 ℃ Zn(en)2S showed a nanosize of about 30 nm, and ZnS of about 60 nm. The fluorescence spectra were also studied. PL results showed that Zn(en)2S excited a fluorescence at 452 nm. 相似文献
20.
We have developed the B2itTM printed circuit board, and presented a related paper entitled, A High-density substrate with buried bump interconnection technology, at the IMC meeting in April 1996. Since then, we have been applying this technology to a variety of boards, and report here, on the application of B2itTM to semiconductor packaging. The product has 0.1 to 0.2 diameter bumps (hereafter called fine bumps). To produce a multilayer high-density printed circuit board, we need to add conductive bumps to each layer over a base layer, which we call the en bloc laminating process. By repeating the en bloc laminating process multiple times, a multilayer stacked array can be fabricated. Signals can go down to internal layers directly from the surface pads via bumps, which is effective for a substrate such as a BGA type package. By using the B2itTM method, it is possible to omit the outerlayer plating process. This is a advantageous for fine line patterning, because the circuit can be patterned by etching the copper foil alone. We introduced two types of liquid photo resist process, one is the ED method, and the other is the liquid photo-resist process which uses a spin coater 相似文献