Like terahertz wave few years ago, the spectral domain of long infrared between 20 and 40 µm is still not so much investigated, mainly in the reason of the absence of source and materials available. However some projects like SOFIA (``Stratospheric Observatory For Infrared Astronomy'') developed at NASA, have demonstrated that measurements in this wavelength range can provide important informations inaccessible at lower wavelength. As an example, essential data have been obtained concerning comet leg by taking advantage of a higher ratio between wavelength and dust grain size that decreases the diffusion. We note also that the coming of quantum cascade laser operating near room temperature at wavelength beyond 20 µm is going to facilitate the development of applications in this spectral range. Globally, apart from diamond, there is only a few of transparent materials in long infrared, excepting maybe glasses containing tellurium and germanium. Therefore optical systems working in this spectral range are constrained to used reflective optics that gives unwanted complexity and size. The improvement of such system through the use of transmissive optics needs the production of new materials possessing adapted physical properties: transparency, sensitivity to environment (water, temperature, ...) and so on. The objective of this project is the realization of glasses transparent in the partialy transmitting atmospheric window located in the long infrared between 24 and 30 µm, even up to 40 µm. The main component will be tellurium that is well known to produce glasses transparent beyond 20 µm, associated with heavy atoms to lower the vibrationnal frequency of inter-atomic bond. Moreover, our previous results tend to indicate that the dimensionality of the atomic structure is an important criterion to obtain transparency window at long wavelength. This aspect will be integrated in the design of the glass composition. The glass synthesis will be done by two different routes: conventional melt and quench technique in sealed tube and mecano-synthesys associated with compaction by hot pressing or Spark plasma sintering (SPS). This new way represents a innovative aspect because it should be possible to extend the vitreous domain. Several stoechiometry will be evaluated in order to proceed to comparative analysis of the properties. The strategy developed to reach the goal of the project, is centered around the understanding of the structure of the glass network. Several technique will be used: Raman and Mössbauer spectroscopies, terahertz spectroscopy (in transmission and/or reflection geometry), neutron diffraction, high energy X-ray diffraction. The results will be completed and interpreted by ab initio calculations according to density functional theory (DFT), Empirical Potential Structure Refinement (EPSR) and Reverse Monte-Carlo (RMC). The evaluation of macroscopic properties of transmission, refractive index, etc ... will be confronted to structural studies in order to orient the stoechiometry of new synthesis.