Estimation of signal noise induced by multimode optical fibers

Optical systems involving multimode fibers generally suffer from increased noise. The noise is present whenever nonuniform optical surfaces follow the multimode fiber, unless the fiber and the conditions of the input radiation are perfectly stable. We have demonstrated fiber mode noise in an optical spectrum analyzer measurement, and developed a simple algorithm to predict the amplitude of this noise, based on the transmission properties of the nonuniform optical surfaces. The algorithm can be useful in estimating the overall signal-to-noise ratio in optical systems; it is particularly useful for designing spectroscopic sensors.