Design, characterization and performance evaluation of few-mode EDFA system with propagation up to six modes
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Design, characterization and performance evaluation of few‑mode EDFA system with propagation up to six modes Taban Qayoom1 · Gausia Qazi1 · Hakim Najeeb‑ud‑din1 Received: 11 April 2020 / Accepted: 18 September 2020 © Springer Science+Business Media, LLC, part of Springer Nature 2020
Abstract Modal gain equalized system for six mode-erbium doped fiber amplifier (6M-EDFA) is designed and analyzed. For the ease in calculation an appropriate pump combination of P21 modes required for reduction in differential mode linearly polarized L P01, LP31 and L gain (DMGλ) is mathematically obtained from extended Giles model. An optimized centre depressed erbium ion profile is also obtained separately. The optimum simplified unidirectional pump combination at 980 nm is then used to excite centre depressed erbium ion profile to achieve considerable reduction in DMGλ. The mathematical analysis is further corroborated with simulation results. The 6M-EDFA system designed provided a minimum DMGλ of 4.41 dB in six mode group and DMGλ of 1.37 dB in five mode group. At smaller values of pump power, a mean gain of about 24.364 dB is achieved at 1550 nm and at lower input signal power of -7 dBm per mode. Gain spectrum is observed to be completely flat over C band for all six modes. Further investigation on evolution of amplified spontaneous emission (ASE) is reported for 6M-EDFA for the first time with new performance metric namely ASE ratio to indicate the deviation of noise between six modes. The ASE ratio of about 2.387 is obtained indicating that the designed system is reasonably immune to noise effects. The influence of non ideal high concentration effects is also investigated on the designed system. The DMGλ values are observed to monotonically increase with length and concentration and decrease with wavelength and input signal powers. Keywords ASE ratio · Doping profiles · Erbium doped profile · Modal gain equalization · Overlap factors · SDM amplifiers
1 Introduction The past few years have shown a growing interest across the scientific community for Space Division Multiplexing (SDM) as one of the means for increasing transmission rates in optical fibers (Richardson et al. 2013; Digonnet 2001; Le Cocq et al. 2012a, 2013). The non-linearity of refractive index puts an upper limit to the increase in launched power * Taban Qayoom [email protected]; [email protected] 1
Department of Electronics and Communication Engineering, National Institute of Technology, Srinagar, Srinagar 190006, India
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(Digonnet 2001). To obtain system capacity with high bit rates, SDM as one of the possible solution based on Few Mode Fibers (FMFs) has been extensively studied (Ryf et al. 2011; Zhu et al. 2011). In order to address the need for optical amplification in long-haul communication systems different Few Mode (FM-EDFAs) along with FMFs and Multi-Core Fibers (MCFs) have been investigated and proposed (Richardson et al. 2013; Le Cocq et al. 2012a; Kang et al. 20
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