搭建了长腔“8”字型掺铒光纤激光器，并对产生的谐波锁模方波脉冲进行了实验研究.结果表明，该脉冲具有光滑的宽带光谱，示波器上显示为方波脉冲，但自相关迹证实其为类噪声脉冲，即为类噪声方波脉冲; 通过调节偏振控制器和泵浦功率等激光器腔内参量，获得了高达5阶的谐波锁模类噪声方波脉冲; 该类噪声方波脉冲并非可以无限增大脉冲能量，而是在一定条件下产生脉冲分裂，出现谐波锁模方波脉冲现象.

The long cavity "8" shaped erbium-doped fiber laser to produce a square wave harmonic mode-locked pulses were studied experimentally. This type has a smooth broadband pulse spectrum shown as a square wave pulse on the oscilloscope, but confirmed that the autocorrelation trace of pulse noise categories, namely noise-square wave pulse. Experiment by adjusting the laser cavity parameters, such as polarization controller and pump power, gets up to 5th order harmonic mode-locked noise-square wave pulse. Experimental results show that the noise-square-wave pulses generated in the fiber laser is not infinitely increasing the pulse energy, but under certain conditions will produce a pulse division, square wave pulse harmonic mode locking phenomenon.