Abstract: Methods and systems are described for free space optical communication. An example device may comprise an optical beam separator configured to separate a first optical path into a receiving (Rx) optical path for signals received from free space and a transmitting (Tx) optical path for signals being transmitted into free space. The example device may comprise at least one positioner coupled to one or more of the Rx optical path or the Tx optical path. The example device may comprise a controller configured to control the at least one positioner to adjust one or more of the Rx optical path or the Tx optical path to facilitate communication with a remote communication device via free space.

Abstract: The orbital states (position and/or time) for a constellation of space vehicles is determined as follows. The space vehicles measure PNT data, including range data determined based on FSO links between the space vehicles. The PNT data is transmitted from the space vehicles to two or more PNT controllers, which are a subset of the space vehicles that calculate the orbital state data for the constellation. This is a semi-distributed calculation. There is not a single controller that performs the calculations for all of the space vehicles in the constellation, and it is also not the case that each space vehicle performs its own calculations. Rather, each PNT controller services a sub-constellation of the space vehicles and determines the orbital state data for the space vehicles in the sub-constellation. The calculated orbital state data is transmitted from the PNT controllers to the space vehicles in the corresponding sub-constellations.

Abstract: Embodiments relate to a free space optical (FSO) communication terminal. The terminal includes an optical source and optics. The optical source can produce optical beams at different wavelengths. The optics direct optical beams in a direction towards a remote FSO communication terminal. A wavelength dependence of the optics results in a divergence of the optical beam that depends on a wavelength of the optical beam. A controller may control the wavelength of the optical beam produced by the optical source, thereby adjusting the divergence of the optical beam (e.g., according to an acquisition process or a tracking process).

Abstract: Exemplary embodiments described a transmission scheme for use in a bi-directional Free Space Optical (FSO) communication system. Each node locally stores a transmitted data block until and acknowledgement is received that it was properly decoded. In the event that a decode was unsuccessful, the data is retransmitted. The receiving node may then add the received signals to then attempt a decode on a combined signal. The system may also include dynamic controls such that the retransmitted signal may be optimized to improve the probability of a successful decode.

Abstract: A fast tracking module for use in free space optical communications includes a primary motion stage supporting receive optics, where the primary motion stage is configured to move the receive optic relative to an optical path.

Abstract: Exemplary embodiments described a transmission scheme for use in a bi-directional Free Space Optical (FSO) communication system. Each node locally stores a transmitted data block until and acknowledgement is received that it was properly decoded. In the event that a decode was unsuccessful, the data is retransmitted. The receiving node may then add the received signals to then attempt a decode on a combined signal. The system may also include dynamic controls such that the retransmitted signal may be optimized to improve the probability of a successful decode.

Abstract: Data is transmitted across an optical fiber communications system by splitting an incoming tributary into multiple low-speed data channels, modulating each of these into a stream of symbols (e.g., by using QAM modulation) and then frequency division multiplexing a number of symbol streams into a single high-speed channel to be transmitted across a fiber. The receiver reverses this process. In order to preserve the jitter tolerance for the overal system, reference clocks are used to remove unwanted jitter in the timing of the system.

Abstract: A frequency division multiplexing (FDM) node used in optical communications networks provides add-drop multiplexing (ADM) functionality between optical high-speed channels and electrical low-speed channels. The FDM node includes a high-speed system and an ADM crosspoint. The high-speed system converts between an optical high-speed channel and its constituent electrical low-speed channels through the use of frequency division multiplexing and preferably also QAM modulation. The ADM crosspoint couples incoming low-speed channels to outgoing low-speed channels, thus implementing the ADM functionality for the FDM node.

Abstract: A frequency division multiplexing (FDM) node used in optical communications networks provides add-drop multiplexing (ADM) functionality between optical high-speed channels and electrical low-speed channels. The FDM node includes a high-speed system and an ADM crosspoint. The high-speed system converts between an optical high-speed channel and its constituent electrical low-speed channels through the use of frequency division multiplexing and preferably also QAM modulation. The ADM crosspoint couples incoming low-speed channels to outgoing low-speed channels, thus implementing the ADM functionality for the FDM node.

Abstract: A frequency division multiplexing (FDM) node used in optical communications networks provides add-drop multiplexing (ADM) functionality between optical high-speed channels, and low-speed tributaries. The FDM node includes a high-speed system and an ADM crosspoint. The high-speed system converts between an optical high-speed channel and its constituent electrical, low-speed channels through the use of frequency division multiplexing. The ADM crosspoint couples any incoming low-speed channels and any incoming tributaries to any outgoing low-speed channels and tributaries, thus implementing the ADM functionality for the FDM node.

Abstract: In an optical communication network, a variable rate or non-uniform input rate signal is converted to a “pseudo” signal comprising a uniform or standard data rate for the optical communication system. At the receiver, the original non-uniform rate signal is recovered.

Abstract: Overhead information is transmitted from a first node to a second node in an optical fiber communications system using a separate frequency band. A control channel containing the overhead information is frequency division multiplexed with electrical low-speed channels to form an electrical high-speed channel, which is converted from electrical to optical form to form an optical high-speed channel. The optical high-speed channel is transmitted over the optical fiber to the second node. In one embodiment, the control channel has a narrow bandwidth and/or is located at lower frequencies than the electrical low-speed channels, thus making the control channel more robust to impairments in the optical fiber.