We are developing a coupled opto-electronic oscillator. The scheme combines the the short optical pulse generation from a mode locked laser and opto-electronic oscillator. The coupled device is capable to generating low jitter high speed optical pulses and, at the same time, producing ultra-low phase noise microwave signal at 10 Ghz and higher.

There has been a great deal of interest in low time-jitter high-repetition-rate pulse generation. The interest stems mainly from fiber-based high-data-rate communications and optical ultra-fast analog-to-digital conversion applications [1]. In these applications, the timing jitter of pulsed signals can be a limiting factor for obtainable communication speed or sampling rate. Recently, actively mode-locked erbium-doped lasers (EDFL) have been demonstrated to be able to generate stable short pulses at 10 GHz and higher [2-4]. This kind of devices is particularly attractive not only because of the all-fiber approach, but also because of its compactness and environmental stability. In an actively mode-locked laser, the pulse-to-pulse jitter is ultimately limited by the phase noise of the mode-locking microwave source (typically electronic frequency synthesizers). On the other hand, opto-electronic oscillators (OEO) using fiber delay lines have been shown capable of generating microwave frequency with extremely low phase noise [5]. Therefore, one can take advantage of the low phase noise of an OEO for ultra-low jitter pulse generation. In this paper, we will describe the development of a new low-jitter pulse generator by combing the two technologies. In this approach, the optical oscillator (mode-locked EDFL) and the microwave oscillator (OEO) are coupled through a common Mach-Zehnder (MZ) modulator as an integrated pulse generator, thus named coupled opto-electronic oscillator (COEO) [6]. More...