The propagation characteristics of doped fiber amplifier have, already, been analyzed using simple coupled-mode analysis (CMA), which steers the interests to apply this simple theory to study the amplification performance of fiber Raman gain amplifier (FRGA). But such study is yet to be done for FRGA. In this paper, a premier report based on CMA is presented to analyze and predict the performance of FRGA for first time, as per our knowledge, using coaxial structure consisting of step-index profiles in both inner and outer cores in terms of effective area, Raman gain coefficient, and effective Raman gain coefficient. In our investigation, we use single pump to compute and compare our results with the results obtained by involved matrix method and a fairly excellent match over a wide region of frequency shift is reported. © 2015 Taylor & Francis.

S PRAMANIK

S SARKAR

University of Calcutta (informally known as Calcutta University or CU) is a collegiate public state university located in Kolkata, West Bengal, India.&nbsp;Within India it is recognized as a &quot;Five-Star University&quot; and accredited &quot;A&quot; Grade by National Assessment and Accreditation Council.

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The University of Calcutta has secured the Fifth position among the Universities of India in the prestigious &quot;Indian University Ranking 2019&quot; list, released by the NIRF of the Ministry of Human Resource Development, Government of India.

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It was established on 24 January 1857, and was one of the first institutions in Asia to be established as a multidisciplinary and Western-style university. Its alumni and faculty include several heads of state, heads of government, social reformers, prominent artists, only academy award winner and Dirac medal winner in India, many Fellows of the Royal Society and five Nobel laureates as of 2019 which is highest in South Asia.

University Of Calcutta

Fiber Raman gain amplifier performance study using simple coupled-mode analysis

Journal of Modern Optics

The fiber tip based hyperbolic microlens coupling efficiency of circular core trapezoidal index single mode fiber and a laser diode is theoretically studied. The corresponding analytical expressions are formulated considering ABCD matrix for hyperbolic microlens following paraxial approximation and also Gaussian field distributions are considered for both the source and the fiber. Here, we study for two different light-emitting wavelengths of practical importance for such fibers. Then, we construct simple empirical formulations to find out the optimum back focal length as function of normalized frequency and aspect ratio of such fibers for optimal excitation of fiber. These handy relations should guide system designer in designing hyperbolic microlens directly on the tip of such fiber carrying the information signal with no need of dependence on rigorous methods to estimate the optimum back focal length. © 2016 Elsevier GmbH

Optik

Coupling of a laser diode to single mode circular core trapezoidal index fiber via hyperbolic microlens on the fiber tip and construction of empirical relations to determine the optimum back focal length

We have studied and reported the effect of practically possible linear dips in the inner core of a coaxial fiber Raman gain amplifier having step index inner and outer cores in the structure on the amplifier performance. In this work, we have used single pump wavelength of 1.465 μm. A variation of dip depth beyond 0.25% of maximum refractive index and that of dip width beyond 25% of the inner core radius deteriorate the gain performance of characteristics of this amplifier significantly along with an appreciable shift of phase matching wavelength. Within these limits, the amplifier resembles closely the behavior of an ideal one. These prescribed limits of dip depth and dip width are also valid limits above which there will be valid ground in their effect to modulate Raman gain performance and dispersion. The present study should find wide attention of system designers. © 2014 Published by Elsevier B.V.

Optics Communications

Effect of dip in refractive index profile on fiber Raman gain amplifier performance

The Chebyshev method is very well known for its simplicity as an approximate analytical formalism to study propagation characteristics of single mode fibers with linear optical media. The method is inapplicable in the context of nonlinear fiber for deeply involved multiplication of various power coefficients. In this article, we propose and develop a simple iterative method based on Chebyshev technique to investigate propagation characteristics of single mode nonlinear fibers and show that our results match with available rigorous results reliably. © 2014 Wiley Periodicals, Inc.

Microwave and Optical Technology Letters

A simple and effective method to analyze the propagation characteristics of nonlinear single mode fiber using Chebyshev method

We vary the core gap radius, the distance between two concentric cores of a single mode Fiber Raman Amplifier (FRA), having a step profile. Based on well known scalar analysis, we study crucially the effects of this variation on the performance characteristics of FRA for the first time. For practically important frequency shift bands of 20-700 cm-1, our interesting observation is that the values of core gap radii in a certain higher range show better flattening of effective Raman gain in comparison to those in lower range with single pump; side by side, a larger negative coefficient of dispersion is achieved in the operating range of wavelength with the increase of core gap radius. These promising criteria should attract the attention of system designers engaged in fabrication of FRA. © 2013 Published by Elsevier B.V.

Effect of variation of core gap radius on the performance of dual concentric core Raman fiber amplifier

A comparative study on fiber Raman gain amplifier performance for coaxial fiber structure having trapezoidal index profile with dispersion shifted criteria in inner core is presented to search for the suitable refractive index profile where single pump wavelength is used. The upper base and lower base of the trapezoidal profile with their ratio, known as aspect ratio, are adjusted to obtain the same phase matching condition for different core radii. The gain performance is analyzed for various core radii. The entire analysis reported for the first time shows that depending upon the fiber parameters the step profiles in the inner core structure perform as the most suitable candidate with a high tolerance for near step profiles. © 2012 Elsevier Ltd.

Journal	Data powered by TypesetJournal of Modern Optics
Publisher	Data powered by TypesetTaylor and Francis Ltd.
ISSN	0950-0340