The Nyquist laser
The Nyquist laser
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DOI：
10.1364/optica.1.000015
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发表时间：
2014-07-22
期刊：
影响因子：
10.4
通讯作者：
Hirooka, Toshihiko
中科院分区：
文献类型：
--
作者：
Nakazawa, Masataka;Yoshida, Masato;Hirooka, Toshihiko
被定义为奈奎斯特滤波器的脉冲响应的奈奎斯特脉冲可以用于同时实现100%的数据速率和频谱效率（SE）。相干奈奎斯特光时分复用传输提高了SE，但光信噪比（OSNR）受到原始CW光束幅度的限制。为了进一步提高传输性能，在这里，我们描述了一种新的脉冲激光器，可以发出一个光学奈奎斯特脉冲序列的重复频率为40 GHz。奈奎斯特激光器是基于一个再生和谐波锁模铒光纤激光器，具有一个特殊的光谱滤波器，以产生一个奈奎斯特脉冲作为输出脉冲。脉冲宽度约为3 ps，振荡波长为1.55 μ m。奈奎斯特脉冲的光谱轮廓可以通过改变滤波器的光谱曲率来改变，其中滚降因子a在0和1之间。在激光腔内安装了法布里-珀罗标准具，选择自由光谱范围为40 GHz的纵模，从而抑制了再生锁模中的跳模现象。数值分析也被提出来解释从激光器的稳定的奈奎斯特脉冲的产生。奈奎斯特激光器不仅对直接产生高OSNR脉冲很重要，而且对科学进步也很重要，证明了与传统双曲正割和高斯脉冲形状显著不同的脉冲形状可以稳定地存在于腔中。(C)2014年美国光学学会
Nyquist pulses, which are defined as impulse responses of a Nyquist filter, can be used to simultaneously achieve an ultrahigh data rate and spectral efficiency (SE). Coherent Nyquist optical time-division multiplexing transmission increases SE, but the optical signal-to-noise ratio (OSNR) is limited by the amplitude of the original CW beam. To further improve transmission performance, here we describe a new pulsed laser that can emit an optical Nyquist pulse train at a repetition rate of 40 GHz. The Nyquist laser is based on a regeneratively and harmonically mode-locked erbium fiber laser that has a special spectral filter to generate a Nyquist pulse as the output pulse. The pulse width was approximately 3 ps, and the oscillation wavelength was 1.55 mu m. The spectral profile of the Nyquist pulse can be changed by changing the spectral curvature of the filter with a roll-off factor, a, between 0 and 1. A Fabry-Perot etalon was also installed in the laser cavity to select longitudinal modes with a free spectral range of 40 GHz, resulting in the suppression of the mode hopping in the regenerative mode locking. A numerical analysis is also presented to explain the generation of a stable Nyquist pulse from the laser. The Nyquist laser is important not only for the direct generation of high-OSNR pulses but also for scientific advances, proving that pulse shapes that differ significantly from the conventional hyperbolic-secant and Gaussian pulse shapes can exist stably in a cavity. (C) 2014 Optical Society of America