Title :
Mitigation and Monitoring of the Impact of Extinction Ratio of IQ-Modulator on Nyquist M-QAM Signals
Author :
Inwoong Kim ; Vassilieva, Olga ; Palacharla, Paparao ; Sekiya, Motoyoshi
Author_Institution :
Dept. of Network Syst. Innovation Group, Fujitsu Labs. of America, Inc., Richardson, TX, USA
Abstract :
We present the analysis of the distortion of optical constellations, induced by IQ-modulator with finite extinction ratio, for NRZ and Nyquist M-QAM signals. We demonstrate that constellation points of NRZ 16-QAM signal shift nonlinearly, whereas constellation points of Nyquist 16-QAM experience linear shift, which is accompanied with appearance of residual carrier in the optical spectrum. Mitigation of this error in Nyquist M-QAM signal is achieved by simple bias adjustment based on monitoring of low-pass filtered RF power at the transmitter output.
Keywords :
low-pass filters; optical distortion; optical modulation; quadrature amplitude modulation; IQ-modulator; NRZ 16-QAM signal shift constellation points; Nyquist M-QAM signals; bias adjustment; error mitigation; extinction ratio mitigation; extinction ratio monitoring; low-pass filtered RF power; optical constellation distortion analysis; optical spectrum; residual carrier; transmitter output; Adaptive optics; Constellation diagram; Optical distortion; Optical filters; Optical pulse shaping; Optical transmitters; Radio frequency; M-ary quadrature amplitude modulation; Nyquist pulse shaping; extinction ratio; optical modulator;
Journal_Title :
Photonics Technology Letters, IEEE
DOI :
10.1109/LPT.2013.2291160
