Q-factor-based level design for photonic ATM switches

A photonic ATM switch based on wavelength-division multiplexing will includ e several lossy passive devices, erbium-doped fiber amplifiers, and semicon ductor optical amplifiers (SOAs) in a cascade configuration for fast switch ing of ns order. Its lever diagram, which is very different from those of o ptical transmission links, has not been adequately studied. This paper inve stigates the concept of basing the level design of the photonic asynchronou s-transfer-mode (ATM) switch we are developing on its Q-factor. First, we d erive formulation of the Q-factor in a single PD and a dual-PD in a Manches ter-encoded signal, which has several merits in packet switching and that w e believe will become popular in photonic packet switches. Using this formu la, we show an example of the level-diagram design including the Q factor c alculation in an optical combiner and distributor section without SOA in ou r photonic ATM, switch. Next, we showed experimentally that the pattern eff ect in SOAs can be suppressed by using a Manchester-encoded signal. Finally we confirm that the allowable minimum level diagram in the switch can be b ased on a simple Q calculation and easy measurement of a bit error rate (BE R) in a back-to-back configuration when using a Manchester-encoded signal. These results show that basing the level design of photonic ATM switches on the Q factor is feasible when using a Manchester signals. This approach ca n be applied to various types of photonic packet switches.