The effect of laser chirping on lightwave system performance

Directly modulated semiconductor lasers exhibit a dynamic wavelength shift (chirping) arising from gain-induced variations of the laser refractive index. The effect of laser chirping on the performance of multi-Gb/s lightwave systems operating at a wavelength of 1550 nm is investigated. Models suitable for computer-aided analysis are used to describe the dynamic response of the laser and the propagation of chirped optical pulses through a step-index single-mode optical fibre. A truncated pulse train, Gauss quadrature rule method is used to evaluate the average bit error rate of the receiver. This permits pattern effects in the transmitted optical waveform due to the laser dynamics and nonlinear optical power transmission properties of optical fibers to be included in the system model. The influence that modulation and device parameters have on the receiver sensitivity is assessed.<>