Under the constraint of fixed pulse distortion, REMZI optical architecture has the highest bandwidth-delay product when compared to SCISSOR and CROW. In the nonlinear regime, nonlinear response fails to improve with increasing number of resonators, but inter-pulse interaction decreases.
We study pulse propagation in the slow-light regime with positive and negative group delays in auto-regressive moving average (ARMA) filters, including the ring-enhanced Mach-Zehnder interferometer (REMZI) and side-coupled integrated spaced sequence of resonators (SCISSOR) optical architectures. Both architectures are optimized to maximize the delay-bandwidth product for a fixed output pulse-distortion level. In the negative-group-delay regime, absorption is incorporated in the rings. The REMZI architecture has the highest delay-bandwidth product in both the positive and negative-group-delay regimes due to greater efficiency in incorporating filter phase within the passband. We also explore the effects of pulse shape in the lossy regime and the limitations it poses in the amount of pulse advancement that is usable for practical applications.
Under the constraint of fixed pulse distortion, we study the bandwidth-delay product and nonlinear phase shift performance of coupled-resonator slow-light waveguides with designs that produce maximally-flat transmission and maximally-flat group delay responses. Even though improvement in bandwidth-delay product can be obtained with increasing number of resonators, the nonlinear response fails to improve beyond a certain number of resonators due to the increased filter bandwidth necessary to maintain a fixed pulse distortion. However, as expected, the nonlinear response improves with resonator finesse and degrades with resonator loss.
Slow light has been proposed as a potential solution to all-optically tunable delay line. However, a slow-light element may degrade data quality in an optical communication system while decreasing group velocity of optical pulses. In this paper, pattern dependence of signal distortion is identified as a main reason for data degradation, which is caused by narrow-band amplitude and phase responses of the slow-light elements. We define figure of merit involving pulse delay and data degradation to optimize slow-light devices. It is shown that the pattern dependence can be reduced by detuning slow-light devices away from the signal carrier frequency, which allows using narrow-band slow-light techniques to increase normalized delay up to 0.8, withQimprovement of 2 dB.