Novel schemes of optical power equalizer (OPE) and optical hard limiter (OHL) are presented, which base on quantum-dot
semiconductor optical amplifiers (QD-SOAs) and adopt a traveling-wave QD-SOA in each arm of Mach-Zehnder
interferometer (MZI). The function of power equalization and hard limitation can be realized respectively in a wide range
by setting the phase difference between two arms of Mach-Zehnder interferometer.