Abstract: A photoreceiver for frequency-modulated optical signals. The photoreceiver is formed of a semiconductor laser of the FABRY-PEROT type, wherein one of the faces thereof which receives a frequency modulated light beam is given an antireflection treatment. The voltage at the laser terminals is also tapped. Such a device finds particular application to optical telecommunication systems.

Abstract: Said medium is a halide glass (2, 8, 12, 20) containing uranium ions at least partly in the form U.sup.3+ and having, at least at one point of a region of the near infrared between 2.2 and 3.4 micrometers, an optical attenuation not exceeding 0.01 cm.sup.-1. For the production thereof, preparation takes place of a halide glass containing uranium ions, at least partly in the form U.sup.4+ and/or U.sup.5+, and having at least at this point the aforementioned attenuation. The glass is exposed to ionizing radiation able to produce trivalent uranium ions from the uranium ions of the prepared glass. Application to the production of optical guides, whereof the guiding parts are formed from such a medium.