A hybrid wireless optical and radio frequency (RF) communication link utilizes parallel free-space optical and RF paths for transmitting data and control and status information. The optical link provides the primary path for the data, and the RF link provides a concurrent or backup path for the network data, as well as a reliable and primary path for the control and status information. When atmospheric conditions degrade the optical link to the point at which optical data transmission fails, the hybrid communication link switches to the RF link to maintain availability of data communications. The switch may occur automatically, based on an assessment of the quality of the optical signal communicated through the optical path.

Hybrid wireless optical and radio frequency communication link

Optical signals are received from a free-space link by directing received light onto a plurality of microlenses and then directing light received through each of the microlenses into a respective single mode optical fiber (SMF). Light beams from the SMFs are combined into a single light beam in one SMF. The single light beam is amplified with a multi-wavelength fiber amplifier and attenuated with a variable optical attenuator. The power gain of the multi-wavelength fiber amplifier and the attenuation of the variable optical attenuator are controlled. The single light beam is directed into a fiber optic communication system that is optically coupled to the variable optical attenuator.

Terrestrial optical communication network of integrated fiber and free-space links which requires no electro-optical conversion between links

An optical multiplexer and demultiplexer for dense wavelength division multiplexed ('DWDM') fiber optic communication systems is disclosed. As a multiplexer, the device functions to spatially combine the optical signals from several laser sources (each of which is a different wavelength) and launch the spatially combined laser beams into a single optical fiber. As a demultiplexer, the device functions to spatially separate the different wavelengths of a wavelength division multiplexed optical link and launch each of the different wavelengths into a different optical fiber. In either embodiment, the device includes both bulk optic and integrated optic components. The spatial separation or spatial combination of laser beams of different wavelength is achieved with the use of bulk diffraction gratings. Also, bulk optical components are used to collimate and shape (or steer) the free space propagating laser beams to enable efficient coupling of light into single mode optical fibers, or integrated optic waveguides, and to reduce optical cross talk. Polarizing beamsplitters orient the polarization direction of the light to enable maximum diffraction efficiency by the gratings and to reduce the polarization dependent loss. Further, the end faces of optical fibers and integrated optic waveguides are angle polished to reduce back reflection and thereby reduce noise caused by feedback to the laser source. Preferably, the diffraction grating and focusing optics are specified to permit multiplexing and demultiplexing of laser wavelengths separated by 0.4 nanometers (nm) in the 1550 nm wavelength band. The preferred field of view of the optics permit multiplexing and demultiplexing of up to 32-48 wavelength channels separated by 0.4 nanometers in the 1550 nm wavelength band. Although examples of performance are provided for the 1550 nm optical wavelength band, the device components can be designed for use at other wavelength bands, e.g., the optical fiber low absorption loss band at μ∩ 1310 nm.

Multiplexer and demultiplexer for single mode optical fiber communication links

The instant invention relates to a method and an arrangement for optical information transmission via satellites by means of broadband optical modulation and reception technology. As a rule, the arrangement is realized in optical satellite terminals, which have optical units, a laser unit, control and supply as well as monitoring units. In the exemplary embodiment, these terminals are designed for a data rate of 1.5 Gbit/s and a transmission distance of more than 1,200 km, while having a weight of less than 8 kg.

Method and arrangement for optical information transmission via satellites

Erbium doped fiber amplifiers (ERDAs) optically couple optical signals between free-space and fiber optic links of a terrestrial optical communication network. The optical gain of transmitting and receiving ERDAs is controlled to achieve good optical signal communication. Control occurs in response to signals received at the transmitting and receiving ends of the links. Control, status and management information may be communicated optically between link head stations. The physical position of transceivers at opposite ends of the link optical signal paths is also controlled.

Method and apparatus for free-space optical communication without eletro-optical conversion

A laser communication system adapted for use in a satellite communication system. The satellite carries a laser communication system. The laser communication system includes a plurality of active and passive optical elements packaged in a monolithic, or single block, structure for interfacing between a focusing beam director of the satellite and laser transmitters/receivers of the laser communication system. Laser energy is directed between the beam director and the transmitters/receivers by the active and active optical elements, such laser energy passing through the monolithic structure solely as collimated light. In this way, relay elements, such as diffractive optics and focusing lenses, and there concomitant alignment requirements, are eliminated from the monolithic structure.

Robert T. Carlson

Papers

Laser satellite communication system