Optical generation and distribution of millimeter-wave signals and optical up-conversion for radio-over-fiber applications.

摘要

This thesis presents a theoretical and experimental study of two techniques used in radio-over-fiber applications. The first technique is concerned with the optical generation and distribution of microwave and millimeter-wave signals. The second is concerned with the optical up-conversion of an electrical subcarrier signal from a low-frequency band to the millimeter-wave band.;The thesis consists of two parts: In the first, three approaches to generating frequency-tunable, high spectral-purity microwave and millimeter-wave signals in the optical domain are proposed and experimentally demonstrated. These approaches are based on external optical modulation using an optical intensity modulator or an optical phase modulator. The key advantage of these approaches is that high spectral purity, frequency-tunable microwave and millimeter-wave signals can be generated using a simple configuration with no tunable optical filter. In addition, optical carrier recovery at a radio-over-fiber base station is also experimentally demonstrated. A detailed theoretical study on the spectral purity of the optically generated and distributed microwave or millimeter-wave signals based on external optical modulation techniques is also conducted. These theoretical results are verified by experiments.;In the second part of the thesis, an approach to optically up-converting an electrical subcarrier signal from a low-frequency band to a millimeter-wave band is proposed. In this approach, two phase-correlated optical waves, which are separated by a frequency difference in the millimeter-wave frequency band, are directly modulated by an electrical subcarrier using an optical intensity modulator. Theoretical analysis shows that the information carried by the low-frequency electrical subcarrier is up-converted to a subcarrier in the millimeter-wave band. Transmission of BPSK and QPSK signals is conducted to validate the proposed approach. In addition, nonlinearities caused by the optical intensity modulator in realizing optical up-conversion are analyzed and discussed. Harmonic distortions and inter-modulation distortions are also analyzed. One-tone and two-tone measurements are performed to validate the analysis.