Simultaneous Spatial and Spectral Transparency in Ultralong Fiber Lasers

We demonstrate that ultralong Raman lasers can be used to generate a transmission medium with simultaneous transparency over the spatial and the spectral domains. Numerical calculations show this cross-domain transparency to be preserved when the medium is used for transmitting high-intensity signals, which makes ultralong lasers an ideal experimental test bed for the study of multifrequency nonlinear interactions in optical fiber waveguides. Full spatiospectral transparency is experimentally obtained over a $20\mathrm{nm}\times 20\mathrm{km}$ window.

Figure 1

(a) Typical URFL cavity. SMF is “standard single mode fiber.” (b) Schematic representation of our OTDR setup.

Figure 2

Numerical signal power excursion in the spectral-spatial plane for a 20 km link. The wavelength range is 20 nm.

Figure 3

Experimental signal power excursion in the spectral-spatial plane for a 20 km link. The wavelength range is 20 nm.

Figure 4

Evolution of the power excursion (left panel) and $\delta P$ parameter (right panel) vs cavity length for 0 dBm total signal power. Triangles, 20 nm bandwidth; circles, 10 nm bandwidth.