Described are retroreflective marker devices, which encode information that can be read by optical sensors, such as LiDAR devices, and that do not detract from human safety. Also described are kits for retrofitting existing markers.

Described herein are ground based subsystems, and related methods, for use in transmitting an optical feeder uplink beam to a satellite that includes a multiple element antenna feed array and that is configured to accept the optical feeder uplink beam and in dependence thereon use the multiple element antenna feed array to produce and transmit a plurality of radio frequency (RF) service downlink beams to service terminals. Certain embodiments are related to a ground based beamformer (GBBF) for inclusion in a ground based subsystem, and methods for use therewith. Beneficially, embodiments described herein allow for flexible antenna beam forming for large signal bandwidth without the limitation associated with the available gateway uplink and downlink spectrum at RF frequencies. Also described herein are space based subsystems for use with such ground based subsystems.

A transmitter for an optical free-beam communication system includes two light transmitters for the optical transmission of a data signal using one single-sideband modulation, wherein each light transmitter emits a side of the band modulation so that a light signal arriving at a receiver corresponds to a double-sideband modulation.

It is impossible to prevent the deterioration of the coupling efficiency between received light and a single mode fiber, and difficult to achieve a higher transmission rate, with respect to a free space optical communication receiver; therefore, a free space optical receiver according to an exemplary aspect of the present invention includes light collecting means for collecting laser light having propagated through a free space transmission path; mode controlling means for separating the laser light collected by the light collecting means into a plurality of propagation mode beams depending on a wave-front fluctuation of the laser light and outputting the propagation mode beams; a plurality of single mode transmission media for guiding the plurality of propagation mode beams, respectively; and a plurality of light receiving means for receiving the plurality of propagation mode beams respectively through the plurality of single mode transmission media.

A coherent transceiver system includes a local oscillator (LO) light source to generate an LO optical signal. An adaptive fiber array is coupled to the LO light source to dephase the LO optical signal. A balanced detector is coupled to the adaptive fiber array to receive a dephased LO signal from the adaptive fiber array and an optical input signal and to generate a heterodyne signal. A controller receives the heterodyne signal and generates one or more control signals. The adaptive fiber array utilizes the control signals to dephase the LO optical signal.

In some embodiments, an optical communication system may include an optical source, a modulator, and a photoreceiver. The optical source may be configured to generate a beam comprising a series of light pulses each having a duration of less than 100 picoseconds. The photoreceiver may have a detection window duration of less than 1 nanosecond. When a first pulse travels through a variably refractive medium, photons in the first pulse may be refracted to travel along different ray paths to arrive at the photoreceiver according to a temporal distribution curve. A full width at half maximum (FWHM) value of the temporal distribution curve may be at least three times as large as a coherence time value of the first pulse, and the detection window of the photoreceiver may be at least six times as large as the FWHM value of the temporal distribution curve.

A reflected light identification (RLID) system uses light to communicate stored information across long distances with minimal interference. The RLID system may include a light source that directs an incident light signal to an RLID structure, which then transmits an encoded light signal to a sensor. The RLID system may include a passive RLID structure (i.e., a structure that does not include power source) such as an RLID reflection surface that includes layered reflective films that reflect the incident light signal back in multiple reflections that serially encodes data. The RLID system may also include an active RLID structure (i.e., a structure that includes power source) that uses energy harvesting to extract and accumulate power from an incident light signal, and then uses the harvested energy to transmit a return signal.

Parallel laser light beams are irradiated from different positions into a telescope. Beams of laser light are incident on a secondary minor attitude detection minor from different locations. Laser light detectors detect each beam of laser light reflected by the secondary minor attitude detection minor. A first attitude calculator determines an amount of attitude variation of a secondary minor based on a result detected by the laser light detectors. The laser light detectors detect each beam of the laser light reflected by the primary minor and the secondary minor after entering the telescope. A second attitude calculator determines an amount of attitude variation of the primary minor based on a result detected by the laser light detectors and the result detected by the laser light detectors.

It is difficult in a free space optical transmitter to transmit a beacon beam stably at low cost, and that it is impossible to maintain stable tracking; therefore, a free space optical transmitter according to an exemplary aspect of the present invention includes a laser beam transmitting means for transmitting a plurality of laser beams capable of interfering with each other and differing in one of an optical frequency and a time variation in a phase difference; and a wavefront control beam transmitting means for transmitting, to a free space, a plurality of wavefront control beams obtained by making each of the plurality of laser beams have a different wavefront.

Challenges of direct-to-Earth (DTE) laser communications (lasercom) between spacecraft in low-Earth orbit (LEO) or medium-Earth orbit (MEO) and ground terminals can include short duration transmission windows, long time gaps between the transmission windows, deleterious effects of atmospheric turbulence, and the inability to operate in cloudy weather. Direct-link optical communications systems described herein can have data rates that are high enough to empty high-capacity on-board buffer(s) (e.g., having a capacity of at least about 1 Tb to hundreds of Tb) of a spacecraft in a single pass lasting only tens of seconds to a few minutes (e.g., 1-15 minutes), and overprovisioning the buffer capacity accounts for variations in the latency between links. One or more distributed networks of compact optical ground terminals, connected via terrestrial data networks, receive and demodulate WDM optical data transmissions from a plurality of orbiting spacecraft (e.g., satellites).