Fiber-optic microcellular communication system using frequency modulated LD and optical discriminator and its nonlinear distortion suppression

This paper discusses the transmission quality in the fiber optic microcellular communication system using a directly modulated laser diode and optical frequency discriminator. A new theoretical approach is used to describe the interaction between the nonlinearities of the directly frequency modulated laser diode and optical frequency discriminator, and the carrier to noise plus distortion ratio is theoretically analyzed. The results show that the receiver sensitivity can be improved by 3 dB using a Mach-Zehnder type frequency discriminator and balanced mixing photodetector. Furthermore, it is clarified that 3rd order intermodulation distortion is effectively suppressed due to the interaction between the laser diode and discriminator nonlinearities. This feature can be applied to adaptive post-distortion nonlinear compensation in the radio-over-fiber FM link