A hybrid RF/laser radar (lidar) sensor that combines modern radar pulse-compression techniques with fiber-optic components has been developed at KU. Compared to conventional lidars, this sensor offers the eye-safe operation that is flexible and reliable without sacrificing range accuracy. Long-duration pulses that are intensity modulated with a RF chirp waveform enable the use of low power signals while delivering high pulse energy and cm-scale range resolution.

Lidar Block Diagram

In the above system diagram, the optical carrier from a laser is modulated by a RF chirp waveform through an electro-optic modulator. This intensity-modulated optical signal is split into two parts – one is amplified and transmitted via the telescope; the other is used as the local oscillator (LO) in a self-chirped homodyne receiver. The target echo picked up by the telescope is combined with the LO through a 3-dB optical coupler and detected by the balanced detector. Unlike conventional homodyne detection where LO is unmodulated, the LO in this system is modulated by the same chirp waveform. Therefore, the homodyne detection process automatically performs RF dechirping in the optics domain and greatly simplifies the required RF processing.