1.1 ,This guide covers the key parameters that determine the dynamic performance of an optical radiation transmitting fiber waveguide (see Note 1). For the purpose of this guide, optical radiation is electromagnetic radiation of wavelengths from about 200 to about 5000 nm (correspondingly, frequencies of 50 ,000 cm^−,1 to 2000 cm^−,1, and photon energies of 6 eV to 0.25 eV).