This paper describes an advanced multimode-fiber-link model that was used to aid the development of Telecommunication Industry Association standard specifications for a next-generation 50m-core laser-optimized multimode fiber. The multimode-link model takes into account the interactions of the laser, the transmitter optical subassembly, and the fiber, as well as effects of connections and the receiver preamplifier. We present models for each of these components. Based on these models, we also develop an efficient and simple formalism for the calculation of the fiber transfer function and the signal at the link output in any link configuration. We demonstrate how the model may be used to develop specifications on transmitters and fibers that guarantee any desired level of performance.

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Local acoustoelasticity in poly(methyl methacrylate) by Brillouin scattering J. Appl. Phys. 54, 5456 (1983); 10.1063/1.332729 Brillouin scattering near the lowtemperature glass transitions of polymethyl methacrylate Brillouin scattering of laser light has been used to measure the frequency of hypersonic sound waves in the range of 10 10 Hz in PMMA as a function of temperature through the glass-transition region. A discontinuity in the temperature coefficient of sound velocity is observed at the glass-transition temperature; this is explained as a consequence of a corresponding discontinuity in the temperature coefficient of the specific volume (thermal expansion coefficient). The ratio of the light scattered by isothermal density fluctuations to that scattered by adiabatic density fluctuations was also measured. This ratio was large and did not change appreciably near the glass-transition temperature. The value of the Landau-Placzek ratio is approximately what one would expect from previously observed ultrasonic-velocity-dispersion data as a function of temperature well above the glass-transition temperature. Both the velocity and intensity ratio data indicate that no velocity-dispersion effects are present for the hypersonic sound waves up to temperatures 35 0 above the glass-transition temperature. These results also indicate that the glass transition is not a classical secondorder phase transition.

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