KEYWORDS: Orthogonal frequency division multiplexing, Distortion, Radio over Fiber, Modulation, Modulators, Mathematical modeling, Signal to noise ratio, Nonlinear optics, Radio optics, Interference (communication)
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.
KEYWORDS: Frequency combs, Modulators, Modulation, Optical filters, Signal to noise ratio, Optical amplifiers, Spectrum analysis, Frequency modulation, Signal attenuation, Bessel functions
The performance of the optical frequency comb generation based on the re-circulating frequency shifter has been
analyzed and demonstrated in this paper. We have theoretically analyzed the condition for flatness of the optical
frequency comb and the relative intensity noise influence. And the resulting performance analysis has been confirmed by
a successfully generated 16 comb lines, which are stable and flat with spacing 12.5 GHz.
KEYWORDS: Modulation, Orthogonal frequency division multiplexing, Modulators, Signal to noise ratio, Radio over Fiber, Extremely high frequency, Distortion, Signal processing, Antennas, Composites
This paper introduces a new bidirectional mmRoF system based on optical frequency multiplication (OFM) scheme
using dual drive Mach-Zehnder Modulator (DD-MZM) and OFDM modulation. The emphasis is put on the optimization
of optical modulation index to the MZ intensity modulator for OFDM signal with high PAR which imposes a limitation
on the system bit error rate (BER) performance due to the nonlinearity of the MZ modulator. The theoretic analysis on
carrier to composite triple beat ratio is performed. The extension to system BER for QAM format is presented and the
experimental proof is given in a 40 GHz mmRoF system.
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