Noise theory of distributed optical amplifiers and its application to fiber amplifiers
Shinji Yamashita
Member
Research Center for Advanced Science and Technology (RCAST), The University of Tokyo, Tokyo, Japan 153
Shinji Yamashita: received a B.S. in Electrical Engineering and an M.S. in Electronic Engineering from the University of Tokyo in 1988 and 1990, respectively. He is now a Research Associate at the Research Center for Science and Technology (RCAST), University of Tokyo. His current interest is in coherent optical fiber communications and optical fiber amplifiers. He is a member of the Institute of Electronics, Information, and Communication Engineers (Japan).
Search for more papers by this authorTakanori Okoshi
Member
Research Center for Advanced Science and Technology (RCAST), The University of Tokyo, Tokyo, Japan 153
Takanori Okoshi: received a B.S., an M.S., and a Ph.D. in Electrical Engineering from the University of Tokyo in 1955, 1957, and 1960, respectively. In 1960 he was appointed Lecturer and in 1961 an Associate Professor in the Department of Electrical Engineering, University of Tokyo. From 1963 through 1964, he was on leave of absence from the University of Tokyo and joined Bell Laboratories, Inc., New Jersey (USA) where he engaged in research on electron guns. In January 1977 he became a Professor of Electronics at the University of Tokyo. In 1987 he was elected the Founding Director of the Research Center for Advanced Science and Technology (RCAST), a newly established interdisciplinary research institute of the University of Tokyo, where he is presently a Professor. At present, he is also a Vice President of URSI (International Union of Radio Science), and has been a Vice President of I.E.I.C.E. (Institute of Electronics, Information, and Communication Engineers), Japan, President of the Japanese Committee for URSI, and President of ITE (Institute of Television Engineers), Japan. His main interests are in optical fiber communications and measurements—particularly coherent optical fiber communications. He is the author of seventeen books, including four in English entitled: Three-Dimensional Imaging Techniques (Academic Press, 1976); Optical Fibers (Academic Press, 1982); Planar Circuits (Springer, 1984); and Coherent Optical Fiber Communications (KTK/Kluwer, 1988, with Dr. K. Kikuchi). He has received 21 awards from IEEE and six Japanese academic institutions, including the 1989 M. N. Liebmann Memorial Award of the IEEE.
Search for more papers by this authorShinji Yamashita
Member
Research Center for Advanced Science and Technology (RCAST), The University of Tokyo, Tokyo, Japan 153
Shinji Yamashita: received a B.S. in Electrical Engineering and an M.S. in Electronic Engineering from the University of Tokyo in 1988 and 1990, respectively. He is now a Research Associate at the Research Center for Science and Technology (RCAST), University of Tokyo. His current interest is in coherent optical fiber communications and optical fiber amplifiers. He is a member of the Institute of Electronics, Information, and Communication Engineers (Japan).
Search for more papers by this authorTakanori Okoshi
Member
Research Center for Advanced Science and Technology (RCAST), The University of Tokyo, Tokyo, Japan 153
Takanori Okoshi: received a B.S., an M.S., and a Ph.D. in Electrical Engineering from the University of Tokyo in 1955, 1957, and 1960, respectively. In 1960 he was appointed Lecturer and in 1961 an Associate Professor in the Department of Electrical Engineering, University of Tokyo. From 1963 through 1964, he was on leave of absence from the University of Tokyo and joined Bell Laboratories, Inc., New Jersey (USA) where he engaged in research on electron guns. In January 1977 he became a Professor of Electronics at the University of Tokyo. In 1987 he was elected the Founding Director of the Research Center for Advanced Science and Technology (RCAST), a newly established interdisciplinary research institute of the University of Tokyo, where he is presently a Professor. At present, he is also a Vice President of URSI (International Union of Radio Science), and has been a Vice President of I.E.I.C.E. (Institute of Electronics, Information, and Communication Engineers), Japan, President of the Japanese Committee for URSI, and President of ITE (Institute of Television Engineers), Japan. His main interests are in optical fiber communications and measurements—particularly coherent optical fiber communications. He is the author of seventeen books, including four in English entitled: Three-Dimensional Imaging Techniques (Academic Press, 1976); Optical Fibers (Academic Press, 1982); Planar Circuits (Springer, 1984); and Coherent Optical Fiber Communications (KTK/Kluwer, 1988, with Dr. K. Kikuchi). He has received 21 awards from IEEE and six Japanese academic institutions, including the 1989 M. N. Liebmann Memorial Award of the IEEE.
Search for more papers by this authorAbstract
Usually, noise characteristics of optical amplifiers are described by the theory of Shimoda, Takahashi, and Towns (STT theory). This theory deals only with lumped amplifiers whose noise parameters are spatially uniform. However, it is not the case with fiber amplifiers.
In this paper, first, a novel noise theory of three-dimensionally distributed amplifiers based on the STT theory is presented and the fundamental equations for calculations of the gain and noise characteristics of a fiber amplifier and systems with fiber amplifiers are obtained. Next, this noise theory is applied to a practical fiber amplifier and an example of the gain and noise characteristics is shown. The backward propagated spontaneous emission is shown to degrade the noise characteristics severely, and the total noise characteristics are shown to be better at 1.553 μm than at 1.530 μm.
Finally, a low erbium-doped fiber system whose gain is balanced with the background loss of the system fiber is analyzed as the system optimizing the signal-to-noise ratio. Nearly ideal characteristics are shown to be realized in this system with the bi-directional pumping.
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