Tunable And Stability Of Optoelectronic Oscillator

Compared with the traditional microwave oscillation, optoelectronic oscillator(OEO) using optical modulator and low loss characteristics converts the continuous light to frequency stability, high spectral purity, ground microwave signal phase-noisy microwave signal. Since OEO has so many advantages. it’s widely applied nowadays. This paper mainly studies OEO. and presents a tunable OEO based on phase modulator and vertical-cavity surface occurs lasers in order to obtain the microwave signal of high quality and high spectral; At the same time, for better studying the signal generated by OEO. the model makes a detailed analysis of its spectrum stability.(1) This thesis analyses the working principle, structure and performance of OEO. and introduces the currently used OEO structure and performance, lastly compares the advantages and disadvantages of various ways of generating microwave signal. Studies shows that the stability of spectrum and phase noise have an effect on the microwave signal generated by OEO.(2) A kind of tunable OEO based on cascaded phase modulator and Vertical-Cavity Surface Emitting Laser(VCSEL) is presented, and a detailed theoretical analysis and numerical simulation are carried out. We use a phase modulator to implement phase modulation by inputting the feedback modulated optical signal into the VCSEL. which is kind of like a phase-shifter. In the case of micro signals, if one side band of the modulated signal is located beyond the side-mode frequency of VCSEL. it will be phase shifted, which will break the balance between the two side bands, and consequently finish the transform from phase modulation to forced modulation and generate the optical signal. The oscillators with this kind of structure are mostly featured with its narrow-band phase shifter based on VCSEL. The narrow-band phase shifter can shift one one-order side band of modulated signal with180degree, transforming from phase modulation to forced modulation. Meanwhile, the change of the driving current of VCSEL occurs the change of the location of the VCSEL’s side-mode frequency, which implements the tunable output of the oscillator with the range up to40G Hz.(3) A system model is established for the stability of the OEO frequency, and the OEO nonlinear dvnamics are studied. We firstly analvze the function of several instruments in the system structure and the theoretical realizability of the stably oscillating within time and frequency domain and the resulting stable microwave signal. Then we use a method of nonlinear dynamics to study the determining characteristics of the ultrapure optical oscillator. However we find out that the nonlinear characteristics still impact on the variety of microwave envelope, thus causing the non-stability of the oscillator bandwidth. Developing from an all micro-integration mode, we using multiple time slicing to form a delay differential equation to denote the various slow changing of microwaves. Finally, the corresponding fixed solutions are found, and the stability of amplitude and phase of feedback gain function have been studied in detail. We are sure about that this is a kind of bifurcation particular. Especially we can prove that when the gain is greater than a threshold value, the generated microwave signal becomes unstable.