Wavelength-selective optical components used in WDM optical communication systems often exhibit a transfer function with amplitude and phase ripples. These ripples can lead to signal distortion and performance degradation. The pulse distortion induced by sinusoidal amplitude and phase response ripples is derived for Gaussian pulses, and concise results are presented for the power penalty in system performance. The analysis shows that the amplitude and phase response ripples have a similar impact on the transmitted signal, and the power penalty induced by these ripples depends on the chirp and pulse width of the transmitted signal. The combined effect of the characteristics of the transmitted signal and the ripple parameters on the system performance is discussed in detail. Numerical simulations show a good agreement with the theoretical analysis.
A technique is presented for measuring the optical phase transfer function of optoelectronic devices for stimulus frequencies from 100 MHz up to the modulation bandwidth of the device. Using high-resolution optical spectra and a novel instrument setup that makes use of RF signal processing to obtain the stimulus signals, the change in phase of an optical signal is obtained as a function of a time-varying electrical stimulus for electrical-to-optical devices or an optical stimulus for optical-to-optical devices. In the technique, the modulation frequency of the stimulus can be varied over a wide range (e.g., 100 MHz to 10 GHz for a 10 Gb/s device). Thus the proposed technique complements low-frequency and stepped measurements of the optical phase transfer function. The technique is demonstrated by considering the change in phase of the output signal from an electroabsorption modulator as a function of the applied voltage.
A model for a multiple quantum well electroabsorption modulator is developed based on measurements of the escape time of photogenerated carriers, the dependence of the fiber-to-fiber loss on the applied voltage, the dependence of the α-parameter of the modulated signal on the applied voltage, and the intensity modulation
frequency response. The accuracy and computational efficiency of the model in describing the intensity and phase modulation properties of optical signal make it suitable for computer simulations aimed at system design and performance evaluation.