Wide bandwidth source for high resolution ranging

An erbium-doped fiber ring laser with a 1 km-long resonator cavity is presented as an instantaneous wideband source for high-resolution lidar and radar. This signal source has a high bandwidth and a uniform spectrum, desirable qualities for high performance correlation-based ranging. A microwave bandwidth photodetector is used to convert the optical signal to an electrical signal with 4 GHz of bandwidth, whose spectral flatness is seen to be +/- 2 dB.