英国电信局在实验室外首次演示了利用光缆的相干传输。试验是在剑桥、贝德福和圣内奥之间的标准光纤上进行的,采用了长外腔激光器作发送器和本地振荡器。在欧洲光通信会议上介绍了一些有关现场试验的详情并展出了一些所用的元器件。相干传输在实验室内已达到了令人满意的程度,它与普通的直接检测系统相比,灵敏度较高、波长选择性较好,对单根光纤上多信道的波分复用特别具有吸引力。然而,以前的一些实验所要求的精密控制只有在实验室中才能做到。英国电信局使用安装在电缆架上的系统通过标准单模光纤来传输信号,该系统泵先是作为商业传输系统而敷设的。长外腔激光器能把1mW以上的1550nm光耦合进光纤,在线宽为100kHz以下时,可以连续调 The British Telecommunications Bureau demonstrated for the first time outside the lab the coherent transmission using optical fiber cables. The experiment was conducted on standard fiber between Cambridge, Bedford and Saint-Honore using a long-cavity laser as a transmitter and a local oscillator. Some details about the field tests were presented at the European Optical Communications Conference and some of the components used were shown. Coherent transmission has reached a satisfactory level in the laboratory, it is compared with ordinary direct detection system, high sensitivity, better wavelength selectivity, especially for multi-channel wavelength division multiplexing on a single optical fiber to attract force. However, the precise controls required by previous experiments are only available in the laboratory. BT uses the system installed on the cable carrier to transmit signals over standard single-mode fiber, which was first deployed as a commercial transmission system. Long external cavity lasers can couple more than 1mW of 1550nm light into an optical fiber and can be continuously modulated when the linewidth is below 100kHz