Abstract:
An optical transmitter includes a modulator, a dispersion adjustment module, and an optical amplifier. The optical transmitter is configured to transmit optical pulses over a free-space optical communication channel. The modulator is configured to produce an optical carrier that is amplitude and/or phase modulated by data. The dispersion adjustment module is connected between the modulator and the amplifier and is configured to substantially change temporal widths of optical pulses received from the modulator by changing dispersions of the received optical pulses.
Abstract:
A free-space communication transceiver includes a telescope for transmitting and receiving laser beams, a tunable laser transmitter for generating a transmit laser beam modulated with data, a tunable optical receiver for processing a receive laser beam received from the telescope to recover data, and a tunable beamsplitter that directs the transmit laser beam to the telescope and directs the receive laser beam from the telescope to the optical receiver. Between the telescope and beamsplitter, the transmit and receive laser beams travel along a common optical axis as collinear collimated free-space beams. The transmit and receive laser beams operate at different wavelengths that can be interchanged, thereby support full-duplex operation. The beamsplitter employs a tunable etalon filter whose wavelength-dependent transmission characteristics are adjusted according to the transmit and receive wavelengths. Optionally, RF signals can additionally be couple to the common optical axis and transmitted and received by the telescope.
Abstract:
Optical signals emanating from the tip of an optical communication fiber can be converted, using a non-linear crystal, to signals (carrier waves) whose wavelength fall in the range of far infra-red to RF. These longer wavelength converted signals maintain the modulation of the original data. Dense fog is inherently opaque to near infra-red waves used in fiber optics communications and relatively transparent to these longer wavelengths. The modulated long wave radiation can, therefore, serve to transmit data from a fiber tip through free space under foggy (and possibly other) prevailing weather conditions. The original optical wave may be recovered by reconverting the received long wave radiation in a heterodyning process taken place in a non-linear crystal with continuous wave laser radiation of an appropriate wave length. Consequently, fiber optics communications networks can be inter-connected seamlessly through a far infra-red/RF free space link.
Abstract:
Die Erfindung betrifft eine Vorrichtung und eine Anlage zur Übertragung von optischen Daten zwischen Satelliten, die einen Laser-Oszillator (10) zur Erzeugung eines optischen Signals, einen Modulator (11) zur Modulierung des optischen Signals mit einer Dateninformation und eine Verstärkeranordnung, eine Kollimatoranordnung und eine Sendeeinrichtung zur Übertragung der Signale umfasst. Es ist vorgesehen, dass ein Vorverstärker (12) mit einer Leistungsteilerstufe (13) verbunden ist, der eine Parallelschaltung von wenigstens zwei jeweils in Reihe geschalteten Phasenstellern (14) und Hauptverstärkern (15), zur Verstärkung und Einstellung der optischen Signale, nachgeschaltet ist und die Hauptverstärker (15) über ein der Anzahl der Reihenschaltung entsprechendes Bündel (16) von optischen Wellenleitungen mit der entsprechenden anzahl der Kollimatoren (17) verbunden sind.
Abstract:
A system for remote optical communications includes a base station and a remote station. The remote station includes a retroreflector, a multiple quantum well modulator (MQW), and drive circuitry that drives the MQW. A base station transmitter sends an interrogating light beam to the MQW, which modulates the light beam based on the information in the electrical signal from the drive circuitry. The retroreflector reflects the modulated light beam to the base station for detection by a receiver.
Abstract:
A high speed optical receiver (fig. 1) for receiving a substantially diminished optical signal. An optical amplifier (6) amplifies the diminished optical signal at least at several db and an ultra narrow-band filter filters (8) the noise generated in the optical amplifier (6) to produce a filtered amplified optical signal which is detected by a fast response photo detector (10). In a preferred embodiment the optical amplifier is a semiconductor laser amplifier. In this embodiment a Faraday filter provides the ultra narrow-band filtering, virtually eliminating the noise produced by the amplifier. Transmitters are described for transmitting information at a wavelength tuned to the ultra narrow-band filters.
Abstract:
An FDMA/TDM satellite-based broadcast system is used to provide digital maps (120) and other type of data to users at remote locations. User selection of the desired data is achieved by monitoring the TDM downlink channels (30) of the broadcast system in accordance with a specific schedule or until a specific identification code is detected. The user terminals (22) are equipped with Global Positioning System receivers (84) which allow the position of the users to be determined. Based on the user position, the user terminal (22) are able to convert general data to location-specific data tailored to the need of the user. The general data may comprise a digital map covering a wide geographic area, and the location-specific data may comprise a map (120) covering a portion of the geographic region where the user is located.
Abstract:
An optical communication system that includes a data transmitter. The data transmitter includes at least one optical emission device configured to output light energy as an optical beam having an operating bandwidth; a beam dividing device arranged to receive and divide the operating bandwidth of the optical beam into bandwidth portions of plural communication bands; a focusing grating; and a digital mirror array having a plurality of digital mirrors. In an imaging mode, the optical communication system is configured to perform hyperspectral imaging by setting all of the plurality of digital mirrors to positions that transmit all wavelengths of a communication band among the plural communication bands to the focusing grating.
Abstract:
A high speed satellite-based laser communications system and method for communications between a satellite-based transmitter system and a ground-based receiver over a free space optical link. The satellite-based transmitter system includes an encoder to encode data, a polarization modulator to linearly polarize the encoded data, one or at least two transmitters to transmit the laser beam, and a quarter-wave optical wave plate to circularly polarize the signal to be transmitted. The ground-based receiver includes an automatic gain control to apply AGC to the received data before the polarizations are reversed and the data is decoded. The system enables an increased data throughput and reduces or eliminates the effects of signal fading.