"JOURNAL OF RADIO ELECTRONICS" (Zhurnal Radioelektroniki ISSN 1684-1719, N 8, 2018

contents of issue      DOI  10.30898/1684-1719.2018.8.12     full text in Russian (pdf)  

Mathematical simulation and experimental comparison of direct and reverse pumping in a Raman amplifier for lidar applications


V. I. Grigorievsky

Fryazino Branch of Kotelnikov Institute of Radioengineering and Electronics of Russian Academy of Sciences, Vvedensky Sq.1, Fryazino Moscow region 141190, Russia


The paper is received on July 28, 2018


Abstract. In this work a study of the characteristics of the output radiation of a Raman fiber amplifier at a wavelength of 1650 nm when comparing direct and reverse pumping performed at a wavelength of 1540 nm was carried out. The amplifier is designed for lidar measurements of methane concentration in the Earth's atmosphere. A model calculation of the output power was used on the basis of exact equations for the propagation of pumping in the fiber in the forward and backward directions. Also we made a direct experiment comparing both pump types with a power of 3.5 W in a fiber with a length of 1500 m. The study showed the advantage of reverse pumping in Raman amplifiers in the wavelength range of ~ 1650 nm both in terms of output power, as well as in spectral purity of the output signal, which is especially valuable for lidar applications. A qualitative explanation of this effect consists in a more efficient use of pumping: with small input signals, together with low pumping at the initial length of the active fiber and at high pumping, together with a large signal on a finite length of fiber. The filtration of the pumping residuals is also better in this case. When the pumping is propagated back with a small input signal, the noise characteristics of the output signal are better, the spectrum is cleaner, the filtration of the pumping remains is better. With large input signals, the difference in output power for both types of pumping decreases: if for small signals this difference is 2-3 times, then for large signals ~ 1.5 times. This is also understandable, since large input signals with direct pumping efficiently remove the inversion on the initial portion of the fiber, that is, the pumping is used more fully.   

Keywords: lidar, Raman amplifier, laser, pumping


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For citation:
V. I. Grigorievsky. Mathematical simulation and experimental comparison of direct and reverse pumping in a Raman amplifier for lidar applications. Zhurnal Radioelektroniki - Journal of Radio Electronics. 2018. No. 8. Available at http://jre.cplire.ru/jre/aug18/12/text.pdf

DOI  10.30898/1684-1719.2018.8.12