Performance of Combined TDM and HOD Raman Pumping Scheme in a Dispersion-Compensated Link
Date Issued
2007
Date
2007
Author(s)
Tung, Wai-Ling
DOI
en-US
Abstract
The ever-increasing demand for ultra high-capacity wavelength-division-multiplexed (WDM) fiber transmission systems pushes the existing technologies to their limits. New concepts are required which allow for a better tradeoff between the three limiting factors: accumulation of amplifier noise, chromatic dispersion, and impairments due to nonlinear effects.
In this thesis, the performance of Raman amplification with a newly proposed pumping scheme in a dispersion-compensated link will be studied. The study considers the three limiting factors and tries to achieve the best tradeoff among them.
The motivation of our study is as follows. There are many different types of optical amplifiers and among them, fiber Raman amplifiers (FRAs) have the advantage of flexible amplification wavelength band and flat gain profile. They are often used in the distributed form to improve the OSNR of a long fiber span. The pumping schemes of FRAs greatly affect their performance and attract many research interests in recently years. The pumping scheme that we are interested is a combined time-division-multiplexed (TDM) and high-order (HOD) pumping scheme. This scheme can reduce the undesired pump-pump interactions while maintaining low nonlinear degradation.
Previous studies of Raman pumping schemes mostly focused on a link with only one kind of fiber. However, this may not be true in current systems. For example, dispersion compensation is necessary in many systems, especially in long-haul systems, and the use of dispersion-compensating fibers (DCFs) is the most popular way to achieve dispersion compensation. The characteristics of DCFs are quite different from those of transmission fibers such as standard single-mode fibers (SSMFs). Therefore, the Raman amplification in a dispersion-compensated link consisting of SSMFs and DCFs will be very different from that in a link with only one kind of fiber.
In this thesis, FRAs’ characteristics with focus on their noise sources will be introduced. Different Raman pumping schemes and their advantages and disadvantages will also be discussed. For the combined pumping scheme under study, there are two possible ways to launch the HOD pump. For a dispersion-compensated link, there are a couple of possible ways to arrange the fibers. Among them, two of them will be considered – post-compensation and pre-compensation. The four configurations (two pumping directions × two fiber arrangements) will be demonstrated and analyzed. The two metrics used are equivalent noise figure (eNF) and Q‐factor.
The experimental results indicate that for a link consisting of an 70 km standard single‐mode fiber (SSMF) and an 11 km dispersion‐compensating fiber (DCF), the configuration of pre‐compensation and forward second‐order
pumping achieves the best tradeoff between noise figure degradation and nonlinear effects.
Subjects
拉曼放大器
雜訊指數
品質因數
Raman amplifier
Noise figure
Q-factor
Type
thesis
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