Spontaneous Raman scattering in SDM fibers

Spontaneous Raman scattering (SpRS) is a weak nonlinear effect particularly relevant to classical-quantum coexistence transmission and sensing applications. In classical transmission, the relevant Raman effect is stimulated Raman scattering (SRS), and recent studies have examined it in space-division multiplexing (SDM) fibers. An intrinsic relation between SpRS and SRS allows previous SRS results to inform SpRS models. In this work, we extend SpRS models derived for single-mode fibers (SMFs) to SDM fibers with multiple mode groups of degenerate modes, covering both Stokes and anti-Stokes bands. The proposed model is a useful, fiber-design-independent tool for evaluating scattered noise in optical links, and it is validated through experimental measurements in field-deployed multi-core fibers (MCFs) and multi-mode fiber (MMF), showing good agreement.