Proc. SPIE. 8309, Optical Transmission Systems, Subsystems, and Technologies IX
KEYWORDS: Mathematical modeling, Signal to noise ratio, Radio optics, Modulation, Interference (communication), Radio over Fiber, Distortion, Modulators, Nonlinear optics, Orthogonal frequency division multiplexing
This paper is concerned with the effect of the nonlinearity of an MZM (Mach-Zehnder modulator) on optical OFDM
signal distortion. The optical OFDM signal output from the MZM is expressed as a Taylor series including third-order
and fifth-order nonlinear distortion terms, by which we can easily establish a mathematical model of the optical OFDM
signals in different formats and rates. According to the model, we can get the EVM at the optimized point. Moreover, the
proposed theoretical model is proved in good agreement with experiment results of the RoF (Radio over Fiber) system.
The influence of higher-order harmonics produced in modulator on flat and stable optical comb generation based on recirculating
frequency shifter (RFS) for all-optical OFDM is analyzed and demonstrated in this paper. We also
theoretically analyze the condition for flatness of the optical frequency comb. The resulting theoretical analysis is
confirmed by a 16 comb lines and 12.5 GHz spacing RFS generation system. The results demonstrate that flat and stable
optical comb generation based on RFS can be a useful solution for multi-wavelength source in all-optical OFDM.
In this paper, a numerical investigation on the nonlinear distortion of OFDM (Orthogonal Frequency Division
Multiplexed) signals caused by RSOA (Reflective Semiconductor Optical Amplifier) as an intensity modulator in
OFDM-PON system is undertaken. Based on curve fitting approach a fourth order polynomial is, for the first time, used
to present the nonlinear gain of RSOA. The expression of in-band and adjacent-band noise due to nonlinear distortion is
then derived. Besides, the EVM of system versus input signal power is simulated by VPItransmissionmaker7.6, the
results indicate the nonlinear effects-induced degradation of transmission performance depends highly on the third order
term of nonlinear distortion power, and the optimum input signal power is provided to improve the transmission
performance. Finally, it's worth mentioning that the quantified analysis method is applicable for the nonlinearity analysis
of any RSOA-Based OFDM-PON system.