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一、两项传统通信技术的回忆为了更好地说明近年广泛研究实验的多路光纤通信以及它们的发展过程,有必要简单地重温人们熟知的两项传统通信技术,即载波电话和外差收音机。1.多路载波电话载波电话是长途电话长期使用的一种重要技术。明线3路、12路,电缆60路,以至同轴电缆300路、1800路和国外10800路都是模拟通信,以电话路数计。它们利用载波遏止的单边带(SSB)、频分复用(FDM)制式,把模拟电话信号对预定频率的载波调幅,由带通滤波器选出单边带。各路载波频率相隔4kHz,组成12路、60路,以至线路上传输的多路群,用强负反馈的群放大器避免发生路际串话。
I. The Memory of Two Traditional Communication Technologies In order to better illustrate the extensive research and experimental multi-channel optical fiber communication and their development in recent years, it is necessary to simply review the two well-known traditional communication technologies, that is, carrier phone and heterodyne radio. 1. Multi-channel carrier phone Carrier phone is a long-term use of long-distance technology is an important technology. Ming Line 3 Road, 12 Road, 60 cable, as well as coaxial cable 300 Road, 1800 and 10800 are foreign analog communications to the number of telephone. They use Carrier Stops Single Sideband (SSB), Frequency Division Multiplexing (FDM) standard, the analog phone signal carrier amplitude modulation of a predetermined frequency, bandpass filter selected single sideband. Each carrier frequency separated by 4kHz, composed of 12 Road, 60 Road, and even the transmission of multi-channel group, with a strong negative feedback of the group amplifier to avoid inter-road cross.