Optical Design of an Optical Communications Terminal

In the second-mentioned transmitting channel (the one used for reference for fine pointing), the 980-nm laser beam would be made to propagate with the 1,550-nm beam through the singlemode optical fiber and the rest of the optical train until the two beams reach the DBS. At the DBS, a significant fraction of the 980-nm beam would be transmitted through relay optics to a retroreflector. The retroreflected 980-nm beam would be guided back to a second beam splitter, where the reflected fraction would be brought to focus at a focal plane (the fine-acquisition focal plane), the field of view of which would be 10 milliradians wide. Thus, steering by the FSM would change the location of the 980-nm-wavelength beam spot on this focal plane.

The fraction of the 980-nm beam transmitted through the DBS would propagate through the rest of the optical train and out of the telescope along with the 1,550-nm beam. If the telescope were to be deliberately mechanically aimed at an external corner-cube reflector, the reflected portion of the 980-nm would travel back into the telescope, through the DBS, and onto the fine-acquisition focal plane to a spot different from the reference spot mentioned in the previous paragraph.

Another portion of the returning 980- nm beam, constituting the beam in the third-mentioned transmitting channel, would impinge on the coarse-acquisition focal plane (that is, on the coarse-acquisition CCD). This arrangement would facilitate the calibration of co-boresightedness between the coarse-acquisition and fine-steering fields of view.

In the first-mentioned receiving channel, a portion of the 852-nm signal from the ground station would impinge on the coarse-acquisition focal plane, which would have a field of view 3° wide — wide enough to facilitate acquisition under most circumstances. In the second- mentioned receiving channel, a portion of the 852-nm signal would be guided to a focus on the fine-acquisition focal plane. The design would ensure that location of this focus would differ from that of the 980-nm beam. In the third-mentioned receiving channel, the beam splitter would divert a fraction of the received 852-nm beam to a detector that would extract any data signal conveyed as modulation of this beam.

This work was done by Abhijit Biswas, Norman Page, and Hamid Hemmati of Caltech for NASA’s Jet Propulsion Laboratory. For further information, access the Technical Support Package (TSP) free on-line at www.techbriefs.com/tsp under the Physical Sciences category. NPO-30537

This Brief includes a Technical Support Package (TSP).

Optical Design of an Optical Communications Terminal (reference NPO-30537) is currently available for download from the TSP library.

Download it now!

 

This Brief includes a Technical Support Package (TSP).

Optical Design of an Optical Communications Terminal (reference NPO-30537) is currently available for download from the TSP library.

Login first to download.