Free-space optical (FSO) wireless transmission, including optical communications, remote-sensing, power beaming, etc., can be enhanced by replacing conventional laser sources that operate in the infrared portion of the optical spectrum with ultra-short pulsed laser (USPL) sources having peak pulse powers of one kWatt or greater and pulse lengths of less than one picosecond. Specifically, it has been observed that under these conditions the attenuation of an USPL beam having the same average optical power as a conventional laser in a lossy medium, such as the atmosphere, is substantially less than the attenuation of a conventional laser beam having a lower peak pulse power and/or a longer pulse width. The superior system performance when using an USPL can be translated into an increased distance between a laser source in a transmitter and a photodetector in receiver and/or a higher reliability of system operation in inclement weather conditions.

A communication device includes a nested modulator composed of sub modulators and a phase shifter. The nested modulator is controlled by: modulating a double pulse by phase and intensity modulation according to transmission information, wherein the double pulse thus modulated is transmitted to another communication device; controlling bias voltages applied respectively to the sub modulators so that a first error rate on the intensity modulation is minimized; and controlling a bias voltage applied to the phase shifter so that a second error rate on the phase modulation is minimized.

An optical system includes a first modulator configured to: receive first input light, modulate an amplitude of the first input light with a first data signal, modulate a phase of the first input light with a first marker signal, and output to an optical element, as first modulated light, the first input light modulated with the first data signal and the first marker signal. The optical system includes a second modulator configured to: receive second input light, modulate an amplitude of the second input light with a second data signal, modulate a phase of the second input light with a second marker signal, and output to the optical element, as second modulated light, the second input light modulated with the second data signal and the second marker signal. The second marker signal includes a complementary version of the first marker signal.