TECHNIQUE FOR MEASUREMENT OF THE RAMAN GAIN COEFFICIENT IN OPTICAL FIBERS

We demonstrate a simple, novel technique for measurement of the Raman gain spectrum in optical fibers. We measure the stimulated Raman scatt ered power generated by a square pulse as a function of its pulse widt h. Because of fiber dispersion, increasing the pulse width increases t he interaction length of the pump and Stokes pulses and leads to a hig her Stokes power. The dependence of growth rate of Stokes power on pul se width gives the Raman ganin coefficient. Our technique does not req uire calibration against a standard or absolute measurements of the St okes signal. We show that gain values obtained with this technique agr ee well with direct pump-probe measurements. (C) 1996 Optical Society of America.