Transmitting information by laser

摘要

This invention concerns an arrangement for transmitting information by means of a laser 6 and a glass fibre cable 7. The arrangement comprises a control means for automatic adjustment of the laser operating point, including a photosensor 10 supplied with a reference light beam 9 diverted from the laser output and a control device 12 which compares the photosensor output with a reference value 15 and, by adjustment of a current source 16 determining the laser operating point, adjusts the value of the photosensor current to that of the reference value 15. In order to test the accuracy of the control means, the arrangement includes a simulator 20 representing an accurate electrical equivalent of the optical path between the laser 6 and the photosensor 10. Selector switches S1 and S2, normally in the positions indicated by the solid lines, may be switched over to their other positions so as to substitute the simulator 20 for the laser 6 and photosensor 10.