Broadband spectrally flat and high power density light source for fiber sensing purposes

Abstract

We present a new kind of broadband continuous-wave source which outperforms any other broadband superluminescent or amplified spontaneous emission source both in terms of output spectral density and bandwidth. Our source covers the wavelength band of interest for fibre applications (from 1450 to 1625 nm) and has an output power of approximately 1.3 W. The source is obtained by pumping a conventional non-zero dispersion-shifted fibre with a continuous-wave Raman fibre laser tuned to the region of small anomalous dispersion of the fibre. The laser beam undergoes an extreme spectral broadening in the fibre. Our experimental results show clearly that the modulation instability (MI)-induced soliton fission is the key element leading to this spectral broadening. Modulation instability is seeded by fast intensity instabilities present in the laser output. We show that this source features good power stability and we believe that it might have very interesting applications in fibre sensing, for instance to avoid the need of amplification in the interrogation of remote Bragg gratings or to improve the resolution and dynamic range of optical coherence tomography setups.