RZ-DQPSK Signal Amplitude Regeneration Using a Semiconductor Optical Amplifier

An all-optical return-to-zero differential quadrature phase-shift keying (RZ-DQPSK) signal regeneration scheme is experimentally demonstrated. Thanks to the gain saturation effect, common quantum-well semiconductor optical amplifiers have the ability to regenerate the amplitude distorted RZ-DQPSK signal, so amplitude noise can be reduced while phase information will not be distorted. A significant eye-opening improvement and a negative power penalty of about 1 dB can be achieved for an 80 Gb/s RZ-DQPSK signal.