Page 76 - Fiber Bragg Gratings

Chapter 3

Fabrication of Bragg

Gratings

3.1 Methods for fiber Bragg grating
fabrication

This chapter reviews many of the schemes proposed for both holographic
and nonholographic grating inscription and considers some of the salient
features of the methods. This introduction excludes methods used for
internal grating writing, traditionally known as "Hill" gratings, for which
the reader is directed to other sources [1-12].
Fiber Bragg gratings, which operate at wavelengths other than near
the writing wavelength (non-Hill gratings), are fabricated by techniques
that broadly fall into two categories: those that are holographic [13] and
those that are noninterferometric, based on simple exposure to UV radia-
tion periodically along a piece of fiber [14]. The former techniques use a
beam splitter to divide a single input UV beam into two, interfering them
at the fiber; the latter depend on periodic exposure of a fiber to pulsed
sources or through a spatially periodic amplitude mask. There are several
laser sources that can be used, depending on the type of fiber used for
the grating, the type of grating, or the intended application. The sources
used for grating production are also discussed in this chapter.

3.1.1 The bulk interferometer
The method for the side writing of fiber gratings demonstrated by Meltz
et al. [15] is shown in Fig. 3.1. The interferometer is one encountered in

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