**4. Conclusion**

262 Photonic Crystals – Introduction, Applications and Theory

**0.57nm 0.57nm (b)**

Fig. 8. Free-running spectrum of 49 cm of Bi-EDF and PCF.

Rayleigh scattering & Reflections

Fig. 9. Output spectrum of the proposed Bi-EDF and PCF based Brillouin fiber laser.

0.09 nm

Brillouin scattering

In summary, new configurations of BFL are proposed and demonstrated using a PCF in conjunction with uni- and bi-directionally pumped Bi-EDF. By employing PCF ring configuration, more than 13 lines are obtained at the maximum 1480 nm pump power of 135 mW as shown in Figure 5(c). The wavelength spacing of setups is nearly between to 0.08- 0.09 nm for the BEFL. The acceptable side mode suppression ratio (SMSR) are obtained in both configurations by 90/10 output coupler are approximately 26.9 dB and 12 dB, respectively. The side modes are mainly due to anti Stokes and additional Stokes of the BFL in the PCF. Despite of this, the 80/20 output coupler demonstrated the lowest cavity loss and the highest SBS in the peak power.

The BFL uses a ring cavity structure to generate Stokes and anti-Stokes via stimulated Brillouin scattering (SBS) and FWM processes. Hence, two nonlinear effects of SBS and FWM are extremely affective on ring fiber laser based PCF. The single- and multiwavelength BFL are stable at room temperature with only minor fluctuations observed coinciding with large temperature variances and also is compact due to the use of only 20 m long of PCF and short long of Bi-EDF.
