Patent ID: 6081323
Filing Date: 2000-06-27
Classification: H04B

Abstract:
An apparatus for measuring a spectral dependence of a Raman gain coefficient, comprising:a controllable optical source for producing optical pulse trains having a plurality of nominally square-shaped optical pulses of controllable temporal pulse width, repetition rate, and optical power, over a pulse width range, and means for launching said optical pulse trains into a fiber under measurement such that said optical pulse trains excite the fiber under measurement producing Raman scattered light;a spectrometer for measuring an optical spectral power density of the Raman scattered light exiting the fiber under measurement over a spectral range of interest; anda device measurement controller having:a means for causing said controllable optical source to launch into the fiber under measurement a plurality of said optical pulse trains having constant average power and a plurality of temporal pulse widths over said pulse width range, each of said optical pulse trains having a plurality of pulses, each having constant temporal pulse width and constant peak power;a means for determining a power level of said optical spectral power density of the Raman scattered light exiting the fiber under measurement for long temporal pulse widths of said plurality of pulses and a rate of change of said optical spectral power density of the Raman scattered light exiting the fiber under measurement, for short pulses as a function of pulse width, for said plurality of pulses over said spectral range of interest from said optical spectral power density of said spectrometer; andmeans for calculating the spectral dependence of the Raman gain coefficient from said power level of said optical spectral power density of the Raman scattered light exiting the fiber under measurement for long temporal pulse widths of said plurality of pulses, said rate of change of said optical spectral power density of the Raman scattered light exiting the fiber under measurement, for short pulses as a function of said plurality of pulses, and said optical spectral power density of the Raman scattered light exiting the fiber under measurement, over said spectral range of interest.