Error-free all-optical wavelength conversion at 168 Gb/s, which is the highest repetition rate ever reported, has been achieved by using a Symmetric-Mach-Zehnder (SMZ)-type switch. Low-power-penalty 84-Gb/s operation is also demonstrated. The push-pull switching mechanism of the SMZ switch enables such ultrafast operation based on cross-phase modulation associated with the carrier depletion in a semiconductor optical amplifier. The configuration of the Delayed-Interference Signal-wavelength Converter, which is a simplified variant of the SMZ switch, is used in this experiment.
We propose a symmetric Mach-Zehnder-type all-optical switch which is based on the nonlinear refractive index change induced in semiconductors. Unlike most all-optical switches, the switch-off time, as well as the switch-on time, of this novel device is not limited by the usually slow carrier lifetime, allowing a very fast switching speed. Its switching characteristics are theoretically examined under various conditions. It is shown that the device offers a nearly square modulation characteristic that is suitable for most switching applications.
In a semiconductor optical amplifier (SOA) with copropagating optical pump pulses, the application of a nonlinear phase shift to optical signals provides the driving force for all-optical interferometric switching. We study, both analytically and experimentally, the dependencies of the nonlinear phase shift on the driving frequency (42-168 GHz) and on the SOA parameters. We have found that the nonlinear phase shift (⌬⌽ NL ) decreases with the driving frequency but that this decrease is only linear, i.e., ⌬⌽ NL ϰ f Ϫ1 . We have also found that the nonlinear phase shift in the SOA linearly increases with the injection current (I op ), i.e., ⌬⌽ NL ϰI op , even in this ultrahigh-frequency range.
A novel optical fiber is proposed that supports the lowest-order soliton despite the presence of optical loss. Groupvelocity dispersion of this fiber decreases with distance, in accord with soliton attenuation that is due to the inherent optical loss of the fiber.
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