Patent ID: 8188418

Claim:
A dual-mode detection system switchable between a direct detection mode and a coherent detection mode, the receiver comprising: a photo detector; a local oscillator laser configured to generate a local oscillator beam; an optical subsystem configured to mix a signal beam with the local oscillator beam to produce a combined beam and direct the combined beam to the photo detector or direct the signal beam to the photo detector without mixing; and a controller configured to switch the system between the direct and coherent detection modes, wherein, in the coherent detection mode, the controller is configured to operate the photo detector in a low gain mode and to control the optical subsystem to mix the signal beam with the local oscillator beam to produce the combined beam and direct the combined beam to the photo detector, and wherein, in the direct detection mode, the controller is configured to operate the photo detector in a high gain mode and to control the optical subsystem to direct the signal beam to the photo detector without mixing.