Wavelength selective bending sensitive multi-ring fiber for suppressing stimulated Raman scattering

Stimulated Raman scattering (SRS) must be suppressed owing to its adverse effect on high-power fiber lasers. We propose a bending-sensitive multi-ring fiber composed of three parts: a core, multiple high-refractive-index rings, and a cladding. Appropriate bending of the fiber produces a high loss of the first-order Raman Stokes wavelength at 1114 nm and low loss of the signal wavelength at 1064 nm, thus enabling the signal light to be confined to the core while maintaining single-mode transmission. This principle relies on the resonant coupling between the core and ring modes. Numerical analysis indicated that the loss ratio of the fundamental mode could reach 2650.041 by optimizing the structural parameters. Moreover, when the three-ring fiber was subjected to a bending radius of 6 cm, a bend-induced loss of the Raman wavelength reached 11.315 dB/m, which effectively suppressed the first Stokes SRS generation.