Abstract: Embodiments of the present invention provide a switchable dual-mode detection system that can be electronically or optically switched between direct and coherent detection. The dual-mode detection system comprises a photo detector and one or more switching elements used in conjunction with the photo detector to electronically or optically switch the detection system between direct and coherent detection. The switching elements may include a switchable detector driver that selectively biases the photo detector into a low gain mode for coherent detection and a high gain mode for direct detection, and/or a switchable optical subsystem that selectively mixes a local oscillator beam with the input signal beam for coherent detection and not for direct detection, and/or an amplifier switch that selectively directs the output photo current of the photo detector to one of two amplifiers, where one of the amplifiers is optimized for direct detection and the other for coherent detection.