Low Noise Optically Pre-amplified Lightwave Receivers and Other Applications of Fiber Optic Parametric Amplifiers

Abstract : Optical amplifiers are key elements in many types of optical systems including optical fiber communication links and laser-based radars. Some of the most important aspects of such amplifiers are their noise performance, optical bandwidth, and power efficiency. During this year, we propose to both extend previous work and initiate new activities. Our work on broadband FOPAs recently resulted in a world record optical bandwidth of over 80 nm (the pump wavelength separation was 103 nm) with 40 dB of gain. We will try to extend this further by extending the wavelength separation of the two pump lasers of the FOPA. To date, our results were limited essentially only by our practical laboratory limitations and not by the inherent properties of the highly nonlinear fiber that provides the gain medium. We now expect to be able to increase the pump separation to 150 nm and beyond and then the internal fiber parameters, such as fourth-order dispersion, zero-dispersion wavelength variation along the fiber, PMD, and certainly stimulated Raman scattering will emerge as limiting factors for the possible gain bandwidth. We may possibly evaluate such a very broadband amplifier as a gain medium in a very widely tunable laser by incorporating it in a cavity with external mirrors. A natural extension of our work on saturation of FOPAs is to investigate its intensity regeneration features, perhaps in particular in the context of phase modulated signals. We will further expand our work to implement phase-sensitive FOPAs. While such amplifiers have intriguing properties, in particular a quantum-limited noise figure of 0 dB, their implementation is very challenging. We will approach this with a so-called non-interferometric approach by using three different optically phase controlled waves of very high coherence at the input stage.