Quantum efficiency - In a photodiode, the ratio of the primary carriers (electron-hole pairs) created to incident photons. A quantum efficiency of 70% means 7 out of 10 incident photons creates a carrier.
Rayleigh scattering - The scattering of light that results from small inhomogeneities in material density or composition. This causes losses in optical power. The losses vary with the 4th power of wavelength. This scattering sets a theoretical lower limit to the attenuation of a propagating lightwave as a function of wavelength. This varies from 10 dB/km at 0.5 microns to 1 dB/km at 0.95 microns.
RAYTELA® - Plastic, fiber optic cable manufactured by Toray Industries.
RB - Rhodamine B dopant.
Receiver - In the context of a fiber optic cable based communications link it is an electronic package, which converts optical signals to electrical signals.
Receiver sensitivity - The minimum acceptable value of average received power at the fiber optic cable receiver point, R, in order to achieve a BER of 10-12. It takes into account power penalties caused by the use of a transmitter with worst-case values of extinction ratio, jitter, pulse rise and fall times, optical return loss at the transmitter point, S, receiver connector degradations and measurement tolerances. The receiver sensitivity does not include penalties associated with dispersion, jitter or reflections from the optical path. These effects are specified separately in the allocation of maximum optical path penalty. Sensitivity takes into account worst-case operating and end-of life conditions. In the case of digital signals the optical power is usually quoted in
Reflectance - Light that is reflected back along the path of transmission, from either the coupling region, the connector or the terminated fiber optic cable.
Reflection - The abrupt change in direction of light as it travels from one material to a dissimilar material. Some of the reflected power gets transmitted back to the source.
Refraction - The bending of a beam of light at an interface between 2 dissimilar media or a medium whose refractive index is a continuous function of position (i.e. a graded index medium).
Refractive Index - The ratio of the velocity of light in a vacuum to its velocity in the medium. It is a synonym of index of refraction. Its symbol in 'n.'
Regenerative repeater - A repeater designed for digital transmission that both amplifies and reshapes the signal. Sometimes called regenerator.
Repeater - An optoelectronic device that amplifies or boosts a signal. Basically, it returns a signal to its original strength.
Responsivity - The ratio of a photodetector's electrical output to its optical input in Amperes/Watt.
Return loss - Same as reflectance.
Return reflection - Reflected optical energy that propagates backward to the source in a fiber optic cable.
Return reflection loss - The attenuation of reflected light. High return loss is desirable, especially in single-mode fiber optic cables.
Ring network - A network topology in which terminals are connected in a point to point serial fashion in an unbroken circular configuration. Frequently used with a token passing access protocol.
Rise time - The time required for the leading edge of a pulse to rise from 10% to 90% of its amplitude. The time required for a component to produce such a result. Turn on time. Sometimes measured between the 20% and 80% points.
Riser - Application for indoor cables that pass between floors. It is normally a vertical shaft or space.
RX - Receiver.
RZ - Signaling code.
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