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SBS. Below this threshold power, only spontaneous scattering emission is oscillating in the resonator. As shown in Figure 3, the SBS power increases as the BP power increases and starts to saturate at around 9 dBm due to the power transfer to the higher order Stokes. With NZ-DSF (20 km), the threshold power is lowest due to the smallest core size. Therefore, the third order Stokes as well as anti-Stokes are observed as shown in Figure 2. Although the second order Stokes light is prevented from oscillating in the cavity, its power is sufficient enough to generate the backscattered light in counter clockwise direction which oscillates in the ring cavity to produce the third order Stokes. The anti-Stokes is achieved due to the four wave mixing process in the ring cavity. Inset of Figure 3 shows the peak power characteristic of the BFL against the BP power for two different lengths of NZ-DSF. As shown in the figure, the BP threshold for SBS is higher with the use of the shorter gain medium length (10 km). There is also no abrupt change from spontaneous scattering to the stimulated scattering due to insufficient interaction length in the gain medium. This also shows that the lower threshold can be achieved by the DCF if the longer length is used. The output of the BFL is observed to be stable at room temperature with only minor fluctuations observed coinciding with large temperature variances. The BFL has a very narrow linewidth and low relative intensity noise as well as frequency noise which make it suitable for sensing applications. CONCLUSIONS