Diverged-beam communications system

Abstract

An apparatus is provided that includes a modulator and an optical transmitter coupled to the modulator and configured to emit an optical beam that the modulator is configured to modulate with data. The optical transmitter may thereby be configured to emit the optical beam carrying the data and without artificial confinement for receipt by an optical receiver configured to detect and recover the data from the optical beam. The optical transmitter may be configured to emit the optical beam with a divergence angle greater than 0.1 degrees, and with a photonic efficiency of less than 0.05%. The photonic efficiency may relate a number of photons of the optical beam detectable by the optical receiver, to a number of photons of the optical beam emitted by the optical transmitter.

What is claimed is: 
     
         1 . An apparatus comprising:
 a demodulator; and   an optical receiver coupled to the demodulator and configured to detect an optical beam that carries data the demodulator is configured to recover, the optical receiver being configured to detect the optical beam emitted without artificial confinement from an optical transmitter configured to emit the optical beam modulated with the data,   wherein the optical receiver is configured to detect the optical beam emitted with a divergence angle greater than 0.1 degrees, and with a photonic efficiency of less than 0.05%, the photonic efficiency relating a number of photons of the optical beam detectable by the optical receiver, to a number of photons of the optical beam emitted by the optical transmitter.   
     
     
         2 . The apparatus of  claim 1 , wherein the optical receiver is configured to detect the optical beam at least in some instances in which the optical receiver does not have a line-of-sight to the optical transmitter. 
     
     
         3 . The apparatus of  claim 1  comprising an array of optical receivers including the optical receiver, or the optical receiver includes an array of detectors configured to detect the optical beam, and
 wherein optical receivers of the array of optical receivers or detectors of the array of detectors are configured to selectively activate and deactivate based on their orientation with respect to the optical transmitter. 
 
     
     
         4 . The apparatus of  claim 1 , wherein the optical beam includes an incident beam, and a reflected beam produced by reflection of the incident beam, the optical receiver in at least one instance being configured to preferentially detect the reflected beam, and avoid direct detection of the incident beam. 
     
     
         5 . The apparatus of  claim 1 , wherein the optical receiver includes an array of detectors configured to detect the optical beam, the array having a size larger than a spot size of the optical beam at the optical transmitter. 
     
     
         6 . The apparatus of  claim 5 , wherein the optical beam is spatially multiplexed to serve multiple optical receivers, the array of detectors being arranged in a pattern of detectors that corresponds to a pattern of emitters of the optical transmitter that are independently modulated. 
     
     
         7 . The apparatus of  claim 1  further comprising a wavelength-specific or wavelength-tunable filter to enable the optical receiver to detect the optical beam that is spectral multiplexed to serve multiple optical receivers. 
     
     
         8 . The apparatus of  claim 1 , wherein the optical receiver is configured to detect the optical beam with an adjustable focus to facilitate a match of the optical receiver to characteristics of the optical beam, the adjustable focus in at least one instance including focus of the optical receiver at some intermediate point between the optical transmitter and optical receiver. 
     
     
         9 . The apparatus of  claim 1  further configured to receive a heartbeat signal for orientation of the optical receiver and optical transmitter, the heartbeat signal being modulated to carry or indicate a location of the optical transmitter, or a signal to cause the optical receiver to return its location or an indication of its location to the optical transmitter. 
     
     
         10 . The apparatus of  claim 1 , wherein the optical receiver includes a camera configured to capture a portion of the optical beam, and electronics with which the camera is configured to communicate to drive coarse or fine steering based on the captured portion of the optical beam to at least partially orient the optical receiver and optical transmitter. 
     
     
         11 . The apparatus of  claim 1 , wherein the optical receiver includes a plurality of photodiodes positioned around a periphery of and that are shadowed by a limiting aperture of the optical receiver, the photodiodes being configured to detect relative powers of the optical beam, the optical receiver further including electronics with which the photodiodes are configured to communicate to drive coarse or fine steering based on the relative powers of the optical beam to at least partially orient the optical receiver and optical transmitter. 
     
     
         12 . The apparatus of  claim 1  further comprising a pointing system operable based on guidance provided by the optical receiver based on reception of a broad optical beam by a separate optical receiver or detector. 
     
     
         13 . The apparatus of  claim 1  further comprising one or more lenses of high-index material to increase an optical gain of the optical receiver. 
     
     
         14 . The apparatus of  claim 1 , wherein the optical receiver being configured to detect the optical beam includes being configured to detect the optical beam that is time division multiplexed. 
     
     
         15 . The apparatus of  claim 14 , wherein the optical receiver being configured to detect the optical beam that is time division multiplexed includes being configured to detect optical beams that are time division multiplexed and emitted from a plurality of optical transmitters. 
     
     
         16 . The apparatus of  claim 1  further configured to change a data rate or modulation of the optical beam based on a signal to noise ratio (SNR) or data integrity of the optical beam. 
     
     
         17 . The apparatus of  claim 1 , wherein the apparatus is embodied as a mobile device equipped with the demodulator and optical receiver. 
     
     
         18 . The apparatus of  claim 1  further configured to use forward error correction to control errors in the data recovered by the demodulator. 
     
     
         19 . The apparatus of  claim 1  further configured to select the optical transmitter based on communication with one or more optical transmitters, and wherein the optical receiver includes electronics to drive coarse or fine steering to at least partially orient the optical receiver and the optical transmitter so selected. 
     
     
         20 . The apparatus of  claim 1 , wherein the optical receiver includes an avalanche photodiode (APD) configured to detect the optical beam. 
     
     
         21 . The apparatus of  claim 1  further comprising pointing and tracking. 
     
     
         22 . The apparatus of  claim 21 , wherein the pointing and tracking includes a pan-and-tilt control. 
     
     
         23 . The apparatus of  claim 1 , wherein the optical receiver is configured to select the optical transmitter from a plurality of optical transmitters based on a characteristic of optical beams from the plurality of optical transmitters. 
     
     
         24 . The apparatus of  claim 1  further configured to decrypt the data recovered from the optical beam. 
     
     
         25 . A method comprising:
 detecting, by an optical receiver, an optical beam emitted without artificial confinement from an optical transmitter configured to emit the optical beam modulated with data; and   recovering the data from the optical beam so detected;   wherein the optical beam detected by the optical receiver has been emitted from the optical transmitter with a divergence angle greater than 0.1 degrees, and with a photonic efficiency of less than 0.05%, the photonic efficiency relating a number of photons of the optical beam detectable by the optical receiver, to a number of photons of the optical beam emitted by the optical transmitter.   
     
     
         26 . The method of  claim 25 , wherein detecting the optical beam includes detecting the optical beam by the optical receiver that does not have a line-of-sight to the optical transmitter. 
     
     
         27 . The method of  claim 25 , wherein detecting the optical beam includes detecting the optical beam by the optical receiver of an array of optical receivers including the optical receiver, or by the optical receiver including an array of detectors, and
 wherein the method further comprises selectively activating or deactivating the optical receivers of the array of optical receivers or detectors of the array of detectors on their orientation with respect to the optical transmitter.   
     
     
         28 . The method of  claim 25 , wherein the optical beam includes an incident beam, and a reflected beam produced by reflection of the incident beam, and detecting the optical beam includes preferentially detecting the reflected beam, and avoiding direct detection of the incident beam. 
     
     
         29 . The method of  claim 25 , wherein detecting the optical beam includes detecting the optical beam by the optical receiver including an array of detectors having a size larger than a spot size of the optical beam at the optical transmitter. 
     
     
         30 . The method of  claim 29 , wherein the optical beam is spatially multiplexed to serve multiple optical receivers, the array of detectors being arranged in a pattern of detectors that corresponds to a pattern of emitters of the optical transmitter that are independently modulated. 
     
     
         31 . The method of  claim 25 , wherein detecting the optical beam includes detecting the optical beam that is spectral multiplexed to serve multiple optical receivers, and the method further comprises wavelength-specific or wavelength-tunable filtering the optical beam to enable the optical receiver to detect the optical beam. 
     
     
         32 . The method of  claim 25 , wherein detecting the optical beam includes detecting the optical beam with an adjustable focus to facilitate a match of the optical receiver to characteristics of the optical beam, the adjustable focus including focus of the optical receiver at some intermediate point between the optical transmitter and optical receiver. 
     
     
         33 . The method of  claim 25  further comprising receiving a heartbeat signal for orientation of the optical receiver and optical transmitter, the heartbeat signal being modulated to carry or indicate a location of the optical transmitter, or a signal to cause the optical receiver to return its location or an indication of its location to the optical transmitter. 
     
     
         34 . The method of  claim 25  further comprising capturing a portion of the optical beamby a camera; and
 driving coarse or fine steering based on the captured portion of the optical beam to at least partially orient the optical receiver and optical transmitter. 
 
     
     
         35 . The method of  claim 25 , wherein the optical receiver includes a plurality of photodiodes positioned around a periphery of and that are shadowed by a limiting aperture of the optical receiver, and wherein the method further comprises:
 detecting relative powers of the optical beam by the photodiodes; and   driving coarse or fine steering based on the relative powers of the optical beam to at least partially orient the optical receiver and optical transmitter.   
     
     
         36 . The method of  claim 25  further comprising operating a pointing system based on guidance provided by the optical receiver based on reception of a broad optical beam by a separate optical receiver or detector. 
     
     
         37 . The method of  claim 25  further comprising one or more lenses of high-index material increasing an optical gain of the optical receiver. 
     
     
         38 . The method of  claim 25 , wherein detecting the optical beam includes detecting the optical beam that is time division multiplexed. 
     
     
         39 . The method of  claim 38 , wherein detecting the optical beam that is time division multiplexed includes detecting optical beams that are time division multiplexed and emitted from a plurality of optical transmitters. 
     
     
         40 . The method of  claim 25  further comprising changing a data rate or modulation of the optical beam based on a signal to noise ratio (SNR) or data integrity of the optical beam. 
     
     
         41 . The method of  claim 25 , wherein detecting the optical beam includes detecting the optical beam at a mobile device equipped with the optical receiver. 
     
     
         42 . The method of  claim 25  further comprising using forward error correction to control errors in the data recovered. 
     
     
         43 . The method of  claim 25  further comprising selecting the optical transmitter based on communication with one or more optical transmitters; and
 driving coarse or fine steering to at least partially orient the optical receiver and the optical transmitter so selected. 
 
     
     
         44 . The method of  claim 25 , wherein detecting the optical beam includes detecting the optical beam with an avalanche photodiode (APD). 
     
     
         45 . The method of  claim 25  further comprising pointing and tracking. 
     
     
         46 . The method of  claim 45 , wherein the pointing and tracking includes a pan-and-tilt control. 
     
     
         47 . The method of  claim 25  further comprising selecting the optical transmitter from a plurality of optical transmitters based on a characteristic of optical beams from the plurality of optical transmitters. 
     
     
         48 . The method of  claim 25  further comprising decrypting the data recovered from the optical beam.