基于啁啾光纤布拉格光栅的宽谱光单边带调制方法

Broadband optical single sideband modulation based on chirped fiber Bragg grating

提出一种基于啁啾光纤布拉格光栅(CFBG)的宽谱光单边带(OSSB)调制实现方法。光双边带(ODSB)调制信号经过同一CFBG两个相反方向的反射,利用偏振控制器(PC)实现两个方向偏振态的正交。这种双反射CFBG(DR-CFBG)结构可以滤出光载波与其中一个边带实现OSSB调制,同时消除了反射谱内的色散,避免了滤波引起的相位畸变。利用实验制作的线性CFBG搭建了DR-CFBG,实验数据仿真结果表明,本文方法可以实现宽谱基带信号与加载数据信息射频信号的OSSB调制,结果表明传输距离大于6km时,40Gb/s NRZ信号OSSB调制传输有明显优势;加载2.5Gb/s的NRZ信号,OSSB调制传输50km,误码率为10-9时,20GHz射频为载波的功率代价比10GHz低3dB,比40GHz低1.2dB。改进CFBG的边沿斜率可以更好地抑制边带残留,提高OSSB调制信号的传输性能。

Broadband optical single sideband （OSSB） modulation is obtained based on the double-reflected chirped fiber Bragg grating （DR-CFBG） structure. This is achieved by launching orthogonally polarized optical double sideband （ODSB） modulation signals in both directions into the CFBG with the help of circulators and polarization controllers,which avoids the crosstalk between the double-reflected signals. An OSSB modulation system based on the fabricated CFBG is set up. This structure filters out optical carrier and one sideband while cancels dispersion, which avoids the phase distortion obtained by filtering. For the transmission over 6 km,the proposed scheme is superior to the ODSB modulated 40 Gbit/s non- return-to zero （NRZ） signal transmission. When 2.5 Gbit/s NRZ data located at different radio frequen- cy （RF） carriers,after 50 km transmission distance,20 GHz RF carrier power penalty is 3 dB lower than that of 10 GHz RF carrier and 1.2 dB lower than that of 40 GHz RF carrier. The proposed sturcture ex- tends transmission distance greatly compared with traditional ODSB modulation. The transmission per- formance of the proposed structure can be improved by decreasing FBG fabrication error and increasing the slope of CFBG reflective spectrum edge.