Compensating power depletion due to stimulated Raman scattering in high-power delivery fiber via spectral inversion revisited in a view of experimental implementation

Peng Dong

doi:10.24297/jap.v14i1.7157

Abstract

Broadband spectral inversion was proved theoretically to be an effective method to compensate power depletion due to stimulated Raman scattering in high-power delivery fiber. A critical difficulty in implementing the method in experiment is to realize broadband spectral inversion of incoherent light as Raman Stokes waves are incoherent due to their origin from spontaneous emission noise. Broadband spectral inversion of incoherent light is investigated experimentally in this article. A beam from an amplified spontaneous emission (ASE) light source is used as an approximated Raman Stokes waves in the experiment. ASE Spectrum of width of 10.5nm is inverted via four-wave mixing in a highly nonlinear dispersion-shifted fiber in efficiency of -10dB without significant spectrum deformation. A theoretical model for four-wave mixing of ASE incoherent light is established, and based on which the limitation in more broadband spectral inversion of ASE incoherent light is analyzed.

Highlights

Raman scattering is a third-order nonlinear effect in which the signal is scattered into the Stokes waves at downshifted frequencies
As Raman Stokes waves are from spontaneous emission noise, the broadband spectral inversion should be performed on incoherent light
In our work reported in Ref. 19, without making a close examination on the feature of four-wave mixing (FWM) between coherent pump light and amplified spontaneous emission (ASE) incoherent signal channels, we adopted the above coupled wave equations (4.1) ~ (4.4) and the theoretical results agree well with the experimental results

Summary

Introduction

Raman scattering is a third-order nonlinear effect in which the signal is scattered into the Stokes waves at downshifted frequencies. A spontaneous Raman scattering becomes stimulated at a threshold value (which is about 600mW for a typical single-mode fiber at a communication wavelength of 1.55μm[1]) and the signal rapidly transfers its power to the Stokes waves. The occurrence of stimulated Raman scattering (SRS) has been a crucial limiting factor for fibers to deliver such a high power from the high power fiber lasers or amplifiers to the application fields mentioned above. Our group proposed a method for compensating power depletion due to SRS in high-power delivery fiber via broadband spectral inversion[9]. This method was proved theoretically to be promising. As Raman Stokes waves are from spontaneous emission noise, the broadband spectral inversion should be performed on incoherent light

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Results

Conclusion