Effect of lower and upper parabolic dips in refractive index profile on performance of coaxial fiber Raman gain amplifier
01 Mar 2016-Optical Engineering (International Society for Optics and Photonics)-Vol. 55, Iss: 3, pp 036103-036103
TL;DR: In this paper, the effect of practically possible upper and lower parabolic dips in the refractive index profile of the inner core of the coaxial fiber Raman gain amplifier is reported using matrix method for single pump.
Abstract: An investigation on the effect of practically possible upper and lower parabolic dips in the refractive index profile of the inner core of the coaxial fiber Raman gain amplifier is reported using matrix method for single pump. It is seen that for lower parabolic dip, the tolerable limits of dip parameters correspond to dip depth of 0.25% and dip width of 25% of the respective parameters for ideal step index profile case and agree with the earlier predicted linear dip. However, for upper parabolic dip, one gets higher gain and better flatness at these limits. Even up to 1% of the dip depth for 25% of dip width or 75% of dip width for 0.25% of the dip depth or 0.5% of dip depth and 50% of dip width, one can expect performance as good as that of the ideal one. However, since system designers will be aimed to produce ideal profile, our recommendation is to keep tolerable limits within 0.25% of dip depth and 25% of dip width of respective parameters. But one can accept profile with upper parabolic dip if there is deviation within the above relaxation limits for such dip.
References
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TL;DR: Simulations show that broadband Raman amplification, with +/- 0.1-dB gain ripple, is achievable over a 31-nm bandwidth (1504-1535 nm) by use of a single pump, and the device is proposed as a lossless dispersion-compensating module wherein lossless operation is achieved byuse of inherently gain-flattened Raman amplified.
Abstract: We report here a broadband, lossless, dispersion-compensating asymmetrical twin-core fiber design with flat-gain Raman amplification that uses a single pump Simulations show that broadband Raman amplification, with +/- 01-dB gain ripple, is achievable over a 31-nm bandwidth (1504-1535 nm) by use of a single pump Amplifier characteristics have been modeled, with the effects of wavelength-dependent splice and background attenuation loss taken into account The fiber also has a high negative-dispersion coefficient [-230 to -330 ps/(km nm)] over the operating wavelength range and, hence, only 125 km of this fiber can compensate for an accumulated dispersion of 240 km of standard transmission fiber The device is thus proposed as a lossless dispersion-compensating module wherein lossless operation is achieved by use of inherently gain-flattened Raman amplification
12 citations
"Effect of lower and upper parabolic..." refers methods in this paper
...Also, large negative dispersion is crucial for flattening of total link dispersion in FRGA throughout operating region and it can be obtained using this fiber structure.(4,18) Various investigations have already been carried out to obtain gain performances and dispersion coefficient of FRGA....
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TL;DR: In this paper, the total dispersion in single mode parabolic-index fibers is computed from the exact numerical solution of the scalar wave equation in the presence and absence of ripples in refractive index profile.
9 citations
TL;DR: In this article, 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.
Abstract: 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.
8 citations
"Effect of lower and upper parabolic..." refers background or methods in this paper
...Very recently, such studies of linear dip (LD)(5) and ripples(6) are reported where tolerable limits of the imperfection parameters are predicted on the basis of matrix method in the context of coaxial FRGA refractive index structure.(7) Moreover, in coaxial structure, when the individual modes of the inner and outer cores are phase matched, complete exchange of power is possible....
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...However, with proper choice of pump wavelength below PMW, one can obtain a flat gain spectrum as a small effective area that results due to tight modal confinement.(4,5,7) In FRGA, the study on effect of dip depth and dip width for LD in RIP is published currently showing how they affect the PMW, effective Raman gain coefficient, and dispersion coefficient, accordingly....
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TL;DR: The group velocity difference between pump pulses is obtained which imposes the upper limit of pulse repetition rate beyond which pump-to-pump interaction occurs and will improve the noise performance of TDM Raman amplifier.
Abstract: We report the gain properties of the multi-wavelength pulsed Raman pump. Group velocity difference between pump pulses imposes an upper limit to the pulse repetition rate beyond which pump-to-pump interaction occurs. Pump-to-pump interaction effect can be severe especially when pump instantaneous power is high due to small duty cycle. Nevertheless, bigger duty cycle imposes much lower limit to the pulse repetition rate. High repetition rate and bigger duty cycle are required to improve the amplifier noise figure. Therefore, optimized level of duty cycle and pulse repetition rate is required. In addition, shorter pump wavelength separation helps to increase the upper limit of pulse repetition rate. Ultimately this will improve the noise performance of TDM Raman amplifier.
7 citations
TL;DR: In this paper, the effect of linear dip 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 was studied and reported.
5 citations