**5. Conclusion**

In this chapter, two tuning processes for fiber Bragg gratings were presented: By mechanical stress on the fiber grating, or by changing its temperature.

In the first method, the optical fiber is more resistant to compression than to extension. The tuning range of the Bragg grating reflects this behavior, and therefore the Bragg grating must be produced with an initial central wavelength close to the upper tuning limit to increase the effective tuning wavelength span.

In the bending compression method, the material supporting the Bragg grating must be elastic enough to allow it to bend but must have the necessary rigidity to follow the curvature of the acrylic base. Therefore, silicone is not a suitable option for this tuning process, and other material with appropriate properties should be investigated.

The temperature tuning process achieved a poor tuning range (0.4 nm) compared to the mechanical tuning processes (19 nm), and it requires a permanent current source so that the Peltier cells can maintain the fiber grating temperature constant. The mechanical tuning system does not require the use of bulky and expensive current sources and maintains the desired tuning even if the electrical system is turned off. This is an additional advantage, which partially reduces electrical energy consumption. Furthermore, the spectral bandwidth (1, 3, and 10 dB) is maintained over a broad tuning range, but extreme bending or stretching of the fiber may chirp the Bragg grating and increase its spectral bandwidth.
