Free-space optical communications system with open loop transmitter control

An optical transmitter apparatus for use in transmitting optical signals to a remote receiver through the atmosphere, comprising:

• a laser source for data transmission having an optical output beam whose wavelength may be controlled;
• a beam splitting device for dividing the optical output beam from the laser source into a first beam that is transmitted to the remote receiver through the atmosphere and a second beam;
• an atmospheric spectral attenuation simulator having attenuation characteristics representative of the atmospheric attenuation of the first beam, the second beam being passed through the atmospheric spectral attenuation simulator;
• a local receiver for measuring the intensity of the second beam after the second beam has passed through the atmospheric spectral attenuation simulator;
• and
• processing circuitry for adjusting the wavelength of the laser source based on the measured intensity of the second optical beam as the second optical beam exits the atmospheric spectral attenuation simulator, so that atmospheric attenuation of the first optical beam is minimized.

An optical transmitter apparatus for use in transmitting optical signals to a remote receiver through the atmosphere, comprising:

• a laser source for data transmission having an optical output beam whose wavelength may be controlled;
• a beam splitting device for dividing the optical output beam from the laser source into a first beam that is transmitted to the remote receiver through the atmosphere and a second beam that is passed through a local optical path having attenuation characteristics representative of the atmospheric attenuation of the first beam;
• a local receiver for measuring the intensity of the second beam after the second beam has passed through the local optical path;
• and
• processing circuitry for adjusting the wavelength of the laser source based on the measured intensity of the second optical beam, so that atmospheric attenuation of the first optical beam is minimized, the processing circuitry including means for receiving weather data from a weather data source.

An optical transmitter apparatus for use in transmitting optical signals to a remote receiver through the atmosphere, comprising:

• a laser source for data transmission having an optical output beam whose wavelength may be controlled;
• a beam splitting device for dividing the optical output beam from the laser source into a first beam that is transmitted to the remote receiver through the atmosphere and a second beam that is passed through a local optical path having attenuation characteristics representative of the atmospheric attenuation of the first beam;
• a local receiver for measuring the intensity of the second beam after the second beam has passed through the local optical path;
• and
• processing circuitry for adjusting the wavelength of the laser source based on the measured intensity of the second optical beam, so that atmospheric attenuation of the first optical beam is minimized, the processing circuitry including means for calculating the expected attenuation of the first optical beam using visibility information.