초록 ▼

An arrangement for secure two-way tactical laser communications between a submarine submerged in an ocean and an airborne platform. During an initital acquisition mode, the airborne transceiver sends a downlink pulse-modulated blue-green laser beam to the ocean surface and below using a predetermine

An arrangement for secure two-way tactical laser communications between a submarine submerged in an ocean and an airborne platform. During an initital acquisition mode, the airborne transceiver sends a downlink pulse-modulated blue-green laser beam to the ocean surface and below using a predetermined IFF code to identify the transceiver to the submarine. In the preferred embodiment the transmit optics spread the beam out into an elongated elliptically-shaped pattern to maximize coverage of the search area. When the downlink beam energy is within range of the submarine, an optical receiver on the submarine detects the beam, filters out the background light with a very narrow-band filter, and converts the light pulses to equivalent electrical pulse. A signal processor in the submarine receiver decodes the electrical pulses and verifies the IFF code to prevent the submarine from responding to a laser beam from an unfriendly source. If the IFF is verified, the submarine laser transceiver transmits a pulse-modulated uplink beam response at the same wavelength, but timed so that the light pulses are time interleaved with the downlink pulses. The uplink beam power is carefully controlled to the minimum power level required by the airborne receiver to recover the uplink beam. As soon as the airborne receiver verifies the uplink IFF code, communications being over the laser link for the duration of time that the airborne platform receiver is within range of the uplink beam. In one embodiment of this invention, both receivers employ a Cesium filled atomic resonance filter (ARF) to separate the blue-green beam from any background light.

대표청구항 ▼

A secure laser communication system providing two-way communications between a submerged platform in an ocean and an airborne platform travelling above the ocean, said communications system comprising: submerged transceiver means for transmitting an uplink beam comprising an uplink pulse-modulated l

A secure laser communication system providing two-way communications between a submerged platform in an ocean and an airborne platform travelling above the ocean, said communications system comprising: submerged transceiver means for transmitting an uplink beam comprising an uplink pulse-modulated laser beam and for receiving a downlink beam; airborne transceiver means for transmitting a downlink beam comprising a downlink pulse-modulated laser beam and for receiving said uplink beam, said airborne transceiver means having two operating modes: an acquisition mode during which the airborne platform searches for the location of the submerged platform, and a communicating mode during which communications occur between said airborne transceiver means and said submerged transceiver means, said airborne transceiver means comprising: first laser means for generating a first laser beam having a blue-green wavelength l1; first modulating means for pulse-modulating said first laser beam with encoded downlink information whereby to produce said downlink pulse-modulated laser beam, said downlink information comprising: (i) a predetermined downlink IFF code for use at least during said acquisition mode, and (ii) supervisory data; first optical transmitting means for transmitting said downlink pulse-modulated laser beam to said submerged transceiver means, said first optical transmitting means including means for controlling the divergence and pointing angle of said downlink beam, such that at least during said acquisition mode said downlink beam has an elongated elliptically-shaped cross-sectional pattern with a wide dimension transverse to the direction of travel of said platform and a narrow dimension parallel to the direction of travel of said platform, said submerged transceiver means having standby and communicating modes of operation corresponding to said acquisition and communicating modes of operation of said airborne transceiver means, respectively, said submerged transceiver means further comprising: first optical receiver means for receiving said downlink beam from said airborne transceiver means; first optical filter means for converting said downlink beam from said first optical receiver means into electrical pulses, said first optical filter means having a very narrow passband centered at the wavelength l1 and providing high attenuation to background radiation; first signal processing means for receiving and decoding said electrical pulses from said first optical filter means and for outputting said downlink information, said first signal processing means including means for verifying said predetermined downlink IFF code in said downlink information; second laser means for generating a second laser beam of wavelength l1 only in response to said verified downlink IFF code; second modulating means for pulse-modulating said second laser beam with encoded uplink information whereby to produce said uplink pulse-modulated laser beam, said uplink information including a predetermined uplink IFF code for use in responding to said encoded predetermined downlink IFF code; second optical transmitting means for transmitting said uplink pulse-modulated laser beam to said airborne transceiver means, said second optical transmitting means including means for varying the output energy in said uplink beam in response to said decoded supervisory data; said airborne transceiver means further comprising: second optical receiver means having a variable field of view for scanning a spatial area for detecting said uplink laser beam during said acquisition mode, and for receiving said uplink beam from a substantially stationary terrestial location during said communicating mode; second optical filter means for converting said received uplink beam from said second optical receiver means into electrical pulses, said second optical filter means including a first atomic resonant filter having a very narrow passband centered at the wavelength l1 and providing high attenuation to background radiation; and second signal processing means for receiving and decoding said electrical pulses from said second optical filter means, said second signal processing means including means for generating a correction signal related to the S/N of said received uplink beam, said correction signal being coupled to said second modulating means for encoding as part of said supervisory data.