Abstract: A laser communication system for an aircraft has optical head units, separate laser transmitting unit, laser receiving unit, optical fiber for each optical head unit, optical switching device for coupling an optical head unit and a separate laser transmitting unit, and a central control unit, the optical head units connected to the optical switching device through the optical fiber, the optical head units having an optical axis, parallel to which light is emitted or received, and an optical pointing mechanism for adjusting the respective optical axis. The separate laser transmitting unit has a laser. The control unit connects to the optical switching device, laser transmitting unit, laser receiving unit and optical head unit to control a laser based data communication through coupling an optical head unit, which is in a free line of sight to a target outside the aircraft, to the laser transmitting unit and to modulate operation of the laser transmitting unit for emitting a signal.

Abstract: To improve liquid level gauging inside liquid tanks, especially cryogenic liquid tanks, an apparatus and method for determining the liquid level are provided. A light source emits outgoing light rays that are back reflected or scattered by the tank wall of the liquid tank. The back reflected or scattered incoming light rays are received by a light conducting device, which conducts the incoming light rays towards a sensor device. The sensor device has optical sensors coupled to the light conducting device such that there is a one-two-one relationship between each optical sensor and a specific tank wall portion. Due to the change in the amount of light that is received by the optical sensor after the outgoing light rays were refracted by the liquid surface, the liquid level determining device is capable of determining the liquid level.

Abstract: In order to improve free space optical communications, an optical communication terminal includes a laser source, a photo detecting apparatus and an optical input/output assembly. These components are controlled by a control logic. In order to have the optical communication terminal to be self-compatible, the optical input/output assembly selectively routes the outgoing beam and incoming beam depending on their respective beam polarization. To this end, the optical input/output assembly may include a polarizing beam splitter together with a quarter-wave plate.

Abstract: A laser communication system for an aircraft has optical head units, separate laser transmitting unit, laser receiving unit, optical fiber for each optical head unit, optical switching device for coupling an optical head unit and a separate laser transmitting unit, and a central control unit, the optical head units connected to the optical switching device through the optical fiber, the optical head units having an optical axis, parallel to which light is emitted or received, and an optical pointing mechanism for adjusting the respective optical axis. The separate laser transmitting unit has a laser. The control unit connects to the optical switching device, laser transmitting unit, laser receiving unit and optical head unit to control a laser based data communication through coupling an optical head unit, which is in a free line of sight to a target outside the aircraft, to the laser transmitting unit and to modulate operation of the laser transmitting unit for emitting a signal.