Step index profile coming out as the best choice for the inner core in fiber Raman gain amplifier under fixed phase matching condition

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.

► Trapezoidal index profile is considered in the inner core of the coaxial Raman gain fiber for various aspect ratios for fixed phase matching condition.
► A comparative study is carried out using single pump only.
► The effect of fiber parameters on the Raman gain performance is analyzed.
► The step index profile shows better performance.