Font Size: a A A

Research On Optoelectronic Oscillator And Its Applications In Radio Over Fiber System

Posted on:2014-03-09Degree:DoctorType:Dissertation
Country:ChinaCandidate:B YangFull Text:PDF
GTID:1268330425981378Subject:Physical Electronics
Abstract/Summary:PDF Full Text Request
Microwave oscillators are widely used as microwave signal source, clocks in high-speed communication and frequency standards in signal detection. Microwave oscillators are critical components in radio frequency applications such as communication system, navigation, radar, instruments, and electronic countermeasures. Based on electro-optical feedback technique and photonic energy storage mechanism, optoelectronic oscillators (OEOs) convert light energy to microwave signal and overcome the limitation of traditional microwave oscillator in phase noise performance. With the ability of generating low phase noise high frequency signals in both electrical and optical domain, the OEOs have wide applications in many important areas, especially for the microwave/millimeter-wave systems.The study in related theory and key technology of the novel OEO is of scientific significance and great theoretical value.In this dissertation, the novel OEO and its application in RoF are studied. At first, the operation principle of OEO is analyzed and several modifications of the classical theoretical model are proposed. Then, the generation of mm-wave signals and realization of wideband frequency-tunable OEOs are studied. Several novel schemes and key technologies are proposed and validated by experiments. At last, photonic microwave up-conversion of vector signals based on a single optoelectronic oscillator for radio over fiber (RoF) system is proposed and demonstrated; a mm-wave RoF system scheme is proposed and demonstrated for the broadband and ubiquitous access network in the near future. The major innovations and contributions are as follows:1. The operation principle of OEO is analyzed. After analyzing the classical theoretical model of OEO, two main modifications to the model are proposed and demonstrated. The first one is that the oscillation power of OEO may be limited by the gain saturation of microwave amplifier. The second one is that the close-in phase noise of OEO will be increased by the frequency dependent flicker noise. 2. By using the nonlinearity of the Mach-Zehnder Modulator (MZM), generation of mm-wave signal is achieved. At first, a frequency-doubling OEO based on a dual electrode MZM (DEMZM) is proposed and demonstrated. The approach features high stability, simple structure and high signal quality. To further increase the frequency multiply times, a frequency-sextupling OEO based on a DPMZM is proposed and validated by simulation. At last, photonic generation of60GHz mm-wave by frequency quadrupling based on a mode-locking SOA fiber ring laser with a low modulation depth MZM is proposed, the frequency-multiplying efficiency can be improved.3. Based on the study on frequency-tunable mechanism of OEO, several novel wideband frequency-tunable OEOs are proposed and the flexible tuning mechanisms of the OEO are improved. At first, a frequency-tunable OEO based on stimulated Brillouin scattering (SBS) and carrier phase-shifted double sideband (CPS-DSB) modulation is proposed and demonstrated. The scheme achieves frequency-doubling and frequency tunability simultaneously for an OEO. However, the phase noise performance of OEO is limited by the Brillouin noise. Therefore, another wideband frequency-tunable OEO based on a narrowband phase-shifted FBG and wavelength tuning of laser is proposed. With assistance of an optical single sideband modulator, the PSFBG with a narrow transmission peak acts like an equivalent high-Q microwave filter to select the oscillation frequency. Frequency tunability of the OEO can be simply realized by tuning the wavelength of a laser source. An X band optoelectronic oscillating signal with frequency tunable at wide range from8.4to11.8GHz is generated. The approach features simple structure, high tuning speed and may realize a tunable range of dozens of GHz. To eliminate the expensive tunable laser, the third scheme is proposed. Based on a dispersion-induced microwave photonic filter (MPF), a GHz tunable range and voltage-controlled OEO is achieved. In this proposal, only a wavelength-fixed laser is required and the frequency tunability is realized by an electricity-friendly method. Besides, due to its short loop structure, it may find potential to integrate the discrete components of the proposed OEO into a chip.4. Photonic microwave up-conversion of vector signals based on a single optoelectronic oscillator with dispersion compensation for RoF system is proposed and demonstrated. The OEO incorporating DPMZM simultaneously works as a high-quality local oscillator (LO) and a broadband mixer to directly frequency up-converts vector signals. The common two-stage modulation in RoF system is avoided. Besides, the dispersion-induced power fading for up-conversion signal can be compensated by properly setting one DC bias of the DPMZM. The proposed approach combines the function of low phase noise microwave generation and vector signal modulation, develops the application of OEO. In the end, a simple and effective bidirectional mm-wave RoF system scenario for access network is proposed and demonstrated, involving the key technologies such as mm-wave generation, base station simplify, dispersion compensation, bidirectional transmission and so on.
Keywords/Search Tags:Optoelectronic oscillator, radio over fiber, phase noise, widebandtunability, frequency-multiply, microwave photonic filter, fiber dispersion
PDF Full Text Request
Related items