Design and Dynamics of Multiloop Optical Frequency Locked Loop

Next generation radar system desires frequency agile low phase noise local oscillator signal. A rapidly tunable multiloop optical frequency locked loop (OFLL) can provide such functionality. The OFLL employs a pair of electro-optic tunable microchip lasers that are heterodyned to produce a frequency agile microwave modulated optical subcarrier. A feedback through a multiloop fiber optic based microwave frequency discriminator assures low phase noise operation. This paper concerns design and optimization of stable, low phase noise OFLLs. This paper features a parametric study, followed by proof-of-concept experiments. Phase noise of -120 dBc/Hz at 10 KHz offset is achieved experimentally and conditions for obtaining a phase noise in excess of -130 dBc/Hz are discussed.