Optical DSB-to-SSB Conversion and Photonic Microwave Amplification Using Stable Locking Dynamics of Semiconductor Lasers for Radio-over-Fiber Links

Abstract

For radio-over-fiber links optical double-sideband modulation (DSB) signals which are typically generated by the simplest scheme of direct or external modulations of optical carriers suffer from the microwave power fading effect due to the chromatic dispersion over optical fibers To mitigate such the unwanted effect single-sideband modulation (SSB) signals are preferred In this thesis a semiconductor laser at stable locking dynamics is used as a unit to convert DSB signals into SSB signals through the red-shifted cavity resonance To deeply realize the applied stable locking dynamics for further applications its characteristics in terms of operation conditions are detailedly investigated as well With the proposed scheme DSB signals can be converted into SSB signals with a sideband rejection ratio of up to 18 dB over a broad microwave frequency of 22 7 to 42 7 GHz which improves the maximum variation in microwave power from as large as 50 dB to 2 2 dB Particularly since the SSB feature is achieved by the enhancement of the lower modulation sideband instead of the suppression the modulation depth increases leading to the amplification in microwave power under the same optical power at the photodetector This can improve the detection sensitivity and the transmission distance The amplification of 18 dB is achieved over a broad microwave frequency from 12 GHz to more than 40 GHz The phase features of the microwaves including 3-dB linewidth and phase noise are mostly preserved The broad gain bandwidth of the modulation sidebands leads to the feasibility of data transmission in RoF links with the high data rate of the order of gigahertz Hence the detection sensitivity of the data after amplification is indeed improved with the amplified microwaves through the proposed scheme

Date of Award	2014 Aug 25
Original language	English
Supervisor	Sheng-Kwang Hwang (Supervisor)