最新刊期
      卷 ， 期 2 ， 1993
      • Issue 2, Pages: 2(1993)
        摘要：<正> 邮电部副部长杨贤足与部基建司司长郑通扬等于今年4月25日来到武汉邮电科学研究院检查工作。杨副部长一行重点检查了该院承担的622Mbit/s、565Mbit/s光通信系统等研究课题及“863”研究项目的进展情况。杨副部长一行来武汉邮电科学研究院之前,还视察了京汉广架空光缆工程武汉—长沙  
          
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      • Issue 2, Pages: 2(1993)
        摘要：<正> 今年4月24～26日在武汉邮电科学研究院召开了“八五”国家通信重点科技攻关项目执行情况汇报会。会议由邮电部科技司总工程师钱宗珏、副处长姜涌主持。国家科委、机电部、中科院、国家教委、邮电部等负责国家通信“八五”重点科技攻关项目的30个单位的60多位代表参加了会议。会上,承担项目的各个单位汇报了课题进展情况,交流了攻关经验。项目牵头单位按合同要求检查攻关计划,布署落实了下一步的任务。国家科委高技术司冯纪春处长、邮电  
          
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      • Yi Heqing
        Issue 2, Pages: 3-8(1993) DOI: 10.13756/j.gtxyj.1993.02.001
        摘要：In this paper.we describe the architecture of Beijing-Wuhan-Guangzhou aerial optical cable project, which is the 1st long distance primary optical cable communication trunk line built with complete China-made optocom products. The optical transmission system and the equipment used for this project is thereby, particularly given in detail.  
        关键词：Aerial optical cable trunk;optical transmission equipment;optical communication system   
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      • Deng Binglun
        Issue 2, Pages: 9-15(1993) DOI: 10.13756/j.gtxyj.1993.02.002
          
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      • Wu Jun
        Issue 2, Pages: 16-20(1993) DOI: 10.13756/j.gtxyj.1993.02.003
        摘要：In this paper,some software &. hardware methods for reset and protection of computer systems have been discussed. A general mode of main programme and a useful multiplex reset circuit are also given in this paper.  
        关键词：single-chip computer;reset;software;hardware   
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      • Yang Risheng A. Landers W. Renken
        Issue 2, Pages: 21-27(1993) DOI: 10.13756/j.gtxyj.1993.02.004
        摘要：Cut-off wavelength is a critical parameter for single-mode fibers. The primary purpose of specifying this quantity is to ensure that the cut-off wavelength of single-mode fiber systems is lower than the operating wavelength, thereby eliminating the possibility of modal noise problems. The cable cut-off wavelength is more relevant to the user because it represents a functional value of cut-off wavelength which can be used in system design. Cabling the fiber tends to shift the cut-off value to shorter wavelengths, therefore a conservative estimate of cable cut-off can be made by measuring un-cabled fiber in the cable cut-off configuration,as recommended by CCITT. 650[1].Fifty SIECOR single^mode fiber samples were measured for the cable cut-off wavelength and the fiber cut-off wavelength according to the above mentioned CCITT recommendation. In the cable cutoff measurements,the 20 m length of uncabled fiber to be deployed in an essentially straight condition was loosely wound on a standard measurement drum of 175 mm radius. The coiling of the fiber length in loops of relatively large radius simulates the cabling effect. To simulate the effects of a splice organizer, one loop of 40 mm radius within 1 m of each end was applied to each fiber end.The measurement results show a mean downward shift in the cut-off wavelength of about 110 nm. A mapping function was developed between the cable cut-off wavelength and the fiber cut-off wavelength. This mapping function can be used to confidently predict the cable cut-off wavelength from the measured fiber cut-off wavelength.As a worst case estimation,the SIECOR fibers will meet a maximum cable cut-off wavelength of 1260 nm, which is recommended by CCITT Recommendation G. 652[1] when the fiber cut-off wavelength is not greater than 1330 nm.  
        关键词：cable;cut-off wavelength;conservative estimate   
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      • He Yan
        Issue 2, Pages: 28-35(1993) DOI: 10.13756/j.gtxyj.1993.02.005
        摘要：The principle and design process of the Quadrature Mirror Filter （QMF） in 16 kbit/s SB—PC speech compression coding system are discussed. The hardware and software structures for implementing QMF to split band are also given in the paper.  
        关键词：SB-APC;speech compression coding;QMF   
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      • Wang He Li Qingdong
        Issue 2, Pages: 36-42(1993) DOI: 10.13756/j.gtxyj.1993.02.006
        摘要：This paper presents an usual design for STM鈥? frame Alignment as per CCITT proposals. An improved design scheme for the STM鈥? frame alignment by using error tolerance technique is analysed. Some practical technologies, such as using of one bit or two bits as error tolerance, possibility of using different lengths of frame alignment codes in the in-frame and out-of-frame status, and the optimum code pattern for frame alignment are also analysed.Finally, an optimum design scheme for the STM—4 frame alignment without much more additional physical difficulties, is proposed, the performance is much better than the specifications of CCITT recommendations.  
          
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      • Wang Jiayi Liu Rui
        Issue 2, Pages: 43-48(1993) DOI: 10.13756/j.gtxyj.1993.02.007
        摘要：Transmission of CATV with optical cables instead of electrical cables is the trend in the days to come. The main problems that we are taking notice of after electrical cables being replaced with optical cables are discussed. The concerned equation of Carrier-to-Noise Ratio （CNR） and the number of possibly achievable channels and PIN/FET’s parameters are found out and the concept of PIN/FET’s integrated evaluation parameter is put forward. Beside the selectable 3 signal combination results that produce no mutual modulation products in every VHF channel are programmed and calculated with computer.  
        关键词：CATV optical cable transmission;carrier-to-noise ratio;PIN/FET;intermodulation   
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      • Chen Zhihao
        Issue 2, Pages: 49-52(1993) DOI: 10.13756/j.gtxyj.1993.02.008
        摘要：Gaussian beam propagation through a parabolic GRIN lens is studied. It is shown that a simple model can be used to describe the object-image transformation of Gaussian beams through the lens when the object distance is lenger than the Rayleigh distance. Some design applications of this model are finally discussed.  
        关键词：graded index lens;Gaussian beam;optical fiber   
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      • Deng Ducai Wang Shubing et al.
        Issue 2, Pages: 53-58(1993) DOI: 10.13756/j.gtxyj.1993.02.009
        摘要：The results of the research on the technology for manufacturing of large-size preforms by using high-efficiency PCVD process have been described. The performance of the equipment used, the study on high deposition rate at 1 g/min and the preparation of large preforms are also included. The fiber length drawn from each preform has exceeded 20 km, with the minimum loss of 0.36 dB/ km at 1.31 μm and of 0.19 dB/km at 1.55 μm.  
        关键词：optical fiber;large-size preforms;PCVD process   
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      • Xu Yuanzhong et al.
        Issue 2, Pages: 59-62(1993) DOI: 10.13756/j.gtxyj.1993.02.010
        摘要：This paper discusses the return loss in air-space type fixed optical attenuator. Theoretically, we analyzed some influences over the return loss of this kind of attenuator, which are mainly caused by the refractive index discontinuity at the input boundary and the length of air space,and also, we have demonstrated by means of experiments.  
        关键词：optical fiber transmission;optical power;fixed optical attenuator;return loss   
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      • Liao Xianbing
        Issue 2, Pages: 63-65(1993) DOI: 10.13756/j.gtxyj.1993.02.011
        摘要：In this paper,the design considerations on noncooler laser transmitter at higher environmental temperature are introduced. The structural isolation of laser was performed to lower the leakage current. Then, temperature compensation for drive current and protective measures for driving circuit are provided.  
        关键词：laser;drive circuit;transmitter   
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