Ultra Pure Signal Generation using Simple Direct Modulation Optoelectronic Oscillator

Abstract

We present a theoretical and experimental analysis of the ultra pure signal generation using simple directly mod-ulation based Opto-Electronic Oscillator (DMOEO) at 2.4GHz carrier frequency. Directly modulated Semiconductor DFB laser is used in non-linear conversion of RF signal into optical signal rather than external intensity modulator. Laser diode is considered as a dimensionless nonlinear transfer function to drive the pump current of the oscillator. Pump current is the combination of laser bias current and feedback RF current that drives the oscillator. Theoretical analysis includes the different input noise parameters in calculating the final phase noise of the DMOEO. Same model is simulated and implemented in hardware with a 1550 nm DFB laser. Our simulation results are shown to be in good agreement with experimental measurements. At 2.41GHz carrier frequency the phase noise of the implemented OEO is coming out to be −109 dBc/Hz at 1kHz offset frequency.