Design Analysis of Optical Loop Memory

This paper describes the fiber optic loop buffer-based switch in which contention is resolved in the time and wavelength domain. In the loop buffer, tunable wavelength converters (TWCs) are placed in place of semiconductor optical amplifiers (SOAs) as in conventional loop buffer-based architectures. The placement of TWCs inside the buffer facilitate simultaneous read/write operation and dynamic re-allocation of wavelengths and improves the switch performance significantly. It is a well known fact that the re-circulating type buffer structure suffers from circulation limit (maximum revolutions that data can take in the buffer) due to the loss and noise accumulation in the switch. This paper presents a mathematical model to obtain a maximum number of allowed circulations of the data in loop buffer-based switch architecture. This model is derived for various configurations (transparent, noisy, and regenerative) of TWC. The detrimental effect of crosstalk and four wave mixing are shown, and the affect of dispersion on the maximum allowed bit rate is discussed. The minimum length of the loop is also evaluated. Finally, the bounded region is shown (bit rate versus number of wavelengths graph) where memory can work efficiently.