Linearization of radio-over-fiber systems by using two lasers with different wavelengths

A linearization technique using two lasers with different wavelengths is further studied to improve output signal and suppress second and third order nonlinearities in radio-over-fiber (RoF) systems simultaneously, if an optical device or a subsystem generates nonlinear distortion and also has wavelength dependent transmission characteristic. In this paper, for an RoF system using an EAM that has wavelength dependent transmission, it is found that the optimum suppression of second order nonlinearity can be achieved by adjusting the power ratio of the two lasers. Compared to using single laser at 1552.6 nm, 1.6 dB improvement of signal power, 23 dB suppression of second order nonlinearity, and 2.1 dB suppression of third order nonlinearity are obtained experimentally. More than 11.5 dB improvement of spurious free dynamic range, 3 dB improvement of input power at 1 dB compression (P_1dB), and 4 dB improvement of output P_1dB are achieved.