Aspects of the disclosure relate generally to a circuit (100) for sustaining an radio frequency (RF) modulated optical signal. The circuit may comprise a self injection locking component (107) having a fiber optic delay line (130) over which a portion of the optical signal propagates. The circuit may also comprise a self phase locked loop component (109) having at least two fiber optic cables (120, 140) having different lengths and over which another portion of the optical signal propagates and a phase detector (150) coupled to the at least two fiber optic cables and configured to determine a phase difference between the signals propagating over one of the respective fiber optic cables. The circuit may further comprise a voltage controlled oscillator (110) configured to generate a stable oscillating signal in response to signals generated by each of the self injection locking and self phase locked loop components, the stable oscillating signal being configured to sustain the optical signal.