As discussed in the previous chapters, it is essential to create an interference pattern (or inscribe the Bragg grating) formed by UV interfering beams to create permanent RI changes in the core of an optical fiber. It may seem simple, but achieving this goal will require some changes and adaptations in the user’s laboratory facilities. Common FBG setups irradiate optical fibers from the side, which is the arrangement featured here.
This chapter does not present the mathematical models and procedures required to design and fabricate FBGs; they will be addressed in Chapter 5. Considering this, there are two major writing (or inscribing, both expressions will be used interchangeably throughout the book) techniques that can be described in advance because there are some differences between them in terms of the optical devices and planning. Section 4.2 discusses the relevant equipment and best practices when implementing a FBG inscription laboratory.