Fig. 1. Normalized absorption/emission spectra of Per (donor) and Rh 6 G (acceptor)^[37].

Fig. 2. Energy level system of co-doped Per-Rh 6 G system.

Fig. 3. Photos of (a) Per-Rh 6 G co-doped preforms and (b) fiber fabricated from preform A under UV (365 nm) excitation.

Fig. 4. Scheme of the measurement setup.

Fig. 5. Luminescence spectra of co-doped fiber fabricated from (a) preform A (Per/Rh6 G ratio 2.8), and (b) preform B (Per/Rh6 G ratio 1.5) viewed during short-length analysis.

Fig. 6. Energy transfer (Per-Rh6 G) efficiency ratio versus the fiber length.

Fig. 7. λmax shift of Per and Rh 6 G dye in fabricated fibers.

Fig. 8. Attenuation spectra of co-doped fabricated fibers A and B.

Fig. 9. Normalized emission spectra of co-doped fiber fabricated from preform A.

Fig. 10. Normalized emission spectra of co-doped fiber fabricated from preform B.

Fig. 11. FWHM of luminescence spectrum and λmax shift versus fiber length.