The Improved Optical Heterodyne Scheme for RoF Systems Based on Optical Carrier Suppression and Optical Injection Locking Techniques

摘要

Abstract In this paper, we proposed an improved optical heterodyne scheme based on optical carrier suppression (OCS) and optical injection locking techniques (OIL) for prospective applications in radio-over-fiber (RoF) systems to generate high-quality millimeter waves. In our scheme, the 60-Ghz millimeter wave signal is generated by heterodyning the outputs of two vertical cavity surface emitting lasers (VCSELs) that are optically injection locked by the two modulation sidebands provided by a 30-GHz externally modulated master tunable laser with suppressed center wavelength. The combined OCS and OIL heterodyne method are not only able to eliminate the phase noise caused by the instability of laser frequencies, but also can further suppress the center wavelength, thus improving the heterodyne performance. We evaluate the transmission quality of the proposed RoF system from the center station to base stations through simulation, and results prove our proposed OCS-OIL-heterodyne scheme to have error-free propagation within a distance of 40 km, better than the OCS-heterodyne scheme.