最新刊期
      卷 ， 期 4 ， 1991
      • He Shan
        Issue 4, Pages: 1-14(1991) DOI: 10.13756/j.gtxyj.1991.04.001
        摘要：This paper discusses on bit insertion coding in digital optical fiber communication systems. The expression of spectral density of mBlH code is deduced. The effects of bit insertion on the spectra of coded sequence are analysed with different mark rates of the inserting bits. The relation between mBlH and mBlC codes is scrutinised.  
          
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      • Chang Shiqiang
        Issue 4, Pages: 15-23(1991) DOI: 10.13756/j.gtxyj.1991.04.002
        摘要：Local centralized supervisory system is a new development in recent years in optical communication centralized supervisory system research by Wuhan Research Institute of Posts and Telecommunications,and is being widely adopted in digital optical communication network in China. This local centralized supervisory system forms the basis for future national centralized supervisory system.This paper introduces the architecture, specifi cation,five basis supervisory modes, principal performance and operation menu for such supervisory system.  
          
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      • Wu Jinliang Bai Chongen
        Issue 4, Pages: 24-33(1991) DOI: 10.13756/j.gtxyj.1991.04.003
        摘要：In this paper, an alternative way is used as equivalent current method by which a nonideal fiber can be viewed as an ideal fiber in the presence of polarization currents giving rise to electromagnetic fields,and the loss of a fiber is considered to be caused by quasi-guided modes excited by polarization currents. The concept of quasi-guided mode is applied in equivalent current method to calculate the loss of a single mode fiber caused by mode conversion. It is an alterna tive method of coupled mode theory without any concerning of mode coupling, but is mathematically simpler and physically more intuitive than the coupled mode theory.  
          
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      • Yang Xinming
        Issue 4, Pages: 34-37(1991) DOI: 10.13756/j.gtxyj.1991.04.004
        摘要：λ/4-shifted grating for DFB lasers has been successfully fabricated by the method of positive and negative photoresist. In this paper, the principle and fabrication process are described in detail, and the results and the quality evaluation are presented. The corrugation periods were about 4600A The quarter-wave phase shift transition width of the gratings were less than 3μm.  
          
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      • Jiang Chen
        Issue 4, Pages: 38-60(1991) DOI: 10.13756/j.gtxyj.1991.04.005
        摘要：This paper discusses calculation and measurement of crosstalk noise index Rn of regenerators, theoretical formulas are obtained and they are testified by experiment. The degree of approximation of two CCITT empirical formulas about Rn is explained by theory.The mutualrelation between the results of Germany’s PRT—1 （as well as Italy’s）measurement and Rn have been given.  
          
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      • Issue 4, Pages: 61-66(1991)
        摘要：<正> 16kbit/s带后滤波器的自适应预测编码系统的研究本文对16kbit/s语音压缩编码进行了研究,构成了带后滤波器的自适应预测编码系统（APC—PF）。1.预测语音信号的统计特性表明:在其相邻样值之间存在很大的相关性。因此,可以用n时刻以前的若干样值的线性组合来预测n时刻的语音样值。即  
          
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      • Issue 4, Pages: 67(1991) DOI: 10.13756/j.gtxyj.1991.04.006
        摘要：<正> 在光纤通信系统中,光纤活动连接器对设备的维护和测试是不可缺少的部件。目前,国内外光纤活动连接器可以分为两类:螺旋耦合型和非螺旋耦合型。国内研制较多的是螺旋耦合型,比设典型的是FC型。武汉邮电科学研究院器件所研制的DPC—1型直插式活动连接器是非螺旋耦合型。下面作简单介绍。1.主要组成DPC—1型直插式连接器主要由定位机构（套筒）、插针体、导向机构、锁定机构四个  
          
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      • Issue 4, Pages: 68(1991)
          
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