Title :
Optimum Design for RF-to-Optical Up-Converter in Coherent Optical OFDM Systems
Author :
Tang, Yan ; Shieh, William ; Yi, Xingwen ; Evans, Rob
Author_Institution :
Dept. of Electr. & Electron. Eng., Univ. of Melbourne, Vic.
fDate :
4/1/2007 12:00:00 AM
Abstract :
In this letter, we conduct analysis on the optimum design for RF-to-optical up-converter in coherent optical OFDM systems using an optical I/Q modulator. We first derive closed-form expressions for the nonlinearity in the optical I/Q modulator, represented by two-tone intermodulation products as a function of the bias point and modulation index. Additionally, we perform a numerical simulation to identify Q-penalty and the excess modulation insertion loss under various transmitter conditions. We find that in contrast to the direct-detected system, the optimal modulator bias point for the coherent system is pi, where the Q-penalty and excess loss are minimized
Keywords :
OFDM modulation; intermodulation; optical fibre communication; optical losses; optical modulation; optical transmitters; Q-penalty; closed-form expressions; coherent optical systems; direct-detected system; modulation insertion loss; optical frequency division multiplexing; optical modulator; optical nonlinearity; optical transmitter; radiofrequency-to-optical upconverter; two-tone intermodulation products; OFDM modulation; Optical design; Optical losses; Optical modulation; Optical receivers; Optical sensors; Optical transmitters; RF signals; Radio frequency; Signal processing; Coherent communications; nonlinearity; optical modulator; orthogonal frequency-division multiplexing (OFDM);
Journal_Title :
Photonics Technology Letters, IEEE
DOI :
10.1109/LPT.2007.893582