EFFECT OF SIGNAL PULSE-SHAPE ON IN-LINE AMPLIFIER TRANSMISSION

This paper discusses the effect of the signal pulse waveform on in-lin e optical amplifier transmission. Under a simple assumption for pulse width evolution along the line, the theoretical expressions of the rec eived signal and noise levels are derived in terms of the initial sign al waveform and the receiver response. Numerical analysis of pulse pro pagation taking fiber dispersion and nonlinearity into account is also carried out to evaluate signal waveform degradation and signal-to-noi se ratio characteristics. The results of the theoretical analysis and those of the numerical analysis exhibit good agreement. The width and sharpness of the signal pulse launched from the transmitter are relate d, through the dispersion length and the nonlinear length, with the ey e opening penalty which is proportional to the square of the transmiss ion distance. It is also clarified that these quantities determine the proportionality coefficient of the square characteristics. Signal wav eform distortion changes not only the received signal level but also t he noise level, both of which affect the signal-to-noise ratio. A larg e width of the launched signal pulse alleviates signal waveform distor tion and therefore reduces signal-to-noise ratio degradation along the line, while a small pulse width is advantageous for the initial signa l-to-noise ratio which is determined by the back-to-back transmitter-r eceiver configuration. A duty factor of 0.6 to 1 is suitable for long- distance transmission at 10 Gbit/s for a fiber dispersion of -0.1 ps/k m/nm. (C) 1998 Scripta Technica.