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本文在长中继距离多模光纤传输系统实践基础上,从工程实际应用的角度进行分析和讨论,得出:对1.3μm波段的多模光纤,用LD光源、二、三次群PCM数字系统和PFM图象传输系统无中继距离将能够达到46km、42km和30km;用LED光源,二、三次群PCM数字系统无中继距离将能够达到26km、23km。以实际系统最终完成后实测数据为依据的推论计算方法以及推论得到的结果,不能做为系统设计原则,但却是设计长中继距离系统时的最好参考。
Based on the practice of multi-mode optical fiber transmission system with long trunk distance, this paper analyzes and discusses from the point of view of engineering application. It is concluded that for 1.3 m band multimode optical fiber, LD light source, second and third order PCM digital system and PFM image transmission system will be able to reach 46km, 42km and 30km without repeaters; with LED light source, the secondary and tertiary PCM digital systems will reach 26km and 23km without repeaters. The inference calculation method based on the measured data after the actual system is finally completed and the inference result can not be used as the system design principle, but it is the best reference when designing the long-distance relay system.