本文从理论上,并通过试验研究了光纤连接点的模式噪声。引用能见度这一概念,导出了计算模式噪声功率、噪声带宽和非线性失真的简单公式。此外,还分析了多模工作下LD的模式噪声。将这些理论上的研究成果应用于高比特率数字系统和以直接脉冲调制的模拟系统。业已表明,在高比特率数字系统中3dB连接损耗可使有效信噪比限制到22dB;在模拟系统中,采用频率100倍于基带信号带宽的叠加脉冲调制,可使信噪比改善20dB以上。 This paper theoretically and experimentally studies the mode noise at the fiber optic connection point. By referring to the concept of visibility, a simple formula for calculating mode noise power, noise bandwidth and nonlinear distortion is derived. In addition, the mode noise of LD under multi-mode operation is also analyzed. These theoretical findings are applied to high bit rate digital systems and analog systems with direct pulse modulation. It has been shown that 3dB connection loss in high bit rate digital systems can limit the effective signal-to-noise ratio to 22 dB; in analogue systems, the superimposed pulse modulation with a frequency of 100 times the baseband signal bandwidth improves the signal to noise ratio by more than 20 dB.