title: Intermodulation and harmonic distortion in slow light Microwave Photonic phase shifters based on Coherent Population Oscillations in SOAs.
abstract: We theoretically and experimentally evaluate the propagation, generation and amplification of signal, harmonic and intermodulation distortion terms inside a Semiconductor Optical Amplifier (SOA) under Coherent Population Oscillation (CPO) regime. For that purpose, we present a general optical field model, valid for any arbitrarily-spaced radiofrequency tones, which is necessary to correctly describe the operation of CPO based slow light Microwave Photonic phase shifters which comprise an electrooptic modulator and a SOA followed by an optical filter and supplements another recently published for true time delay operation based on the propagation of optical intensities. The phase shifter performance has been evaluated in terms of the nonlinear distortion up to 3rd order, for a modulating signal constituted of two tones, in function of the electrooptic modulator input RF power and the SOA input optical power, obtaining a very good agreement between theoretical and experimental results. A complete theoretical spectral analysis is also presented which shows that under small signal operation conditions, the 3rd order intermodulation products at 2Ω1 + Ω2 and 2Ω2 + Ω1 experience a power dip/phase transition characteristic of the fundamental tones phase shifting operation.
authors.affiliation: ITEAM Research Institute, Universidad Politécnica de Valencia, 46022 Valencia, Spain. ivgames@iteam.upv.es
authors.forename: Ivana
authors.initials: I
authors.lastname: Gasulla
authors.forename: Juan
authors.initials: J
authors.lastname: Sancho
authors.forename: José
authors.initials: J
authors.lastname: Capmany
authors.forename: Juan
authors.initials: J
authors.lastname: Lloret
authors.forename: Salvador
authors.initials: S
authors.lastname: Sales
mesh_terms: D000669:Amplifiers, Electronic; D016477:Artifacts; D003198:Computer Simulation; D017076:Computer-Aided Design; D004867:Equipment Design; D019544:Equipment Failure Analysis; D008872:Microwaves; D008962:Models, Theoretical; D055096:Optical Devices; D009991:Oscillometry / Q000295:instrumentation*; D017785:Photons; D012666:Semiconductors