Intermodulation distortions are generated by Mach-Zehnder modulators when they are driven by signals with certain bandwidth in microwave (MW) and millimeter-wave (MMW) radio-over-fiber (ROF) links. The optical spectral structure of the distorted optical signal is investigated. A strategy to improve the dynamic range of MW and MMW ROF links directly in the optical domain is proposed and experimentally demonstrated. Based on optical spectrum processing, the third-order intermodulation distortions (IMD3s) of the generated signals are suppressed. A 107.2dB∙Hz2/3 spurious-free dynamic range (SFDR) of the MW/MMW ROF link is obtained, which is improved more than 20dB. A 16QAM signal is transmitted in the system and the error vector magnitude (EVM) is measured with and without the proposed technique. The influence of the nonlinearity of modulators on EVM is almost completely eliminated.
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