Linearity enhancement of uncooled DFB laser diode using opto-electrical predistortion method for radio-over-fiber systems

Abstract

We propose and demonstrate a pre-distortion method for reducing the third-order intermodulation distortion (IMD3) of the distributed-feedback laser diode. The pre-distortion scheme consists of two loops and uses two laser diodes (LD), a photodetector (PD), RF attenuators, RF combiners/dividers, and an RF amplifier. In our scheme, the error signal is generated by the slave LD through controlling the phase and attenuation adjustment in the inner loop and then drives the master LD to reduce nonlinear property in the outer loop. The experimental results show that the significant reduction of about 30 dB in the third-order intermodulation distortion (IMD3) is achieved at 2.4 GHz in the implemented system. For the broad frequency range from 1.97 GHz to 2.48 GHz (510 MHz), IMD3 is enhanced by more than 10 dB.