Page 437 - Fiber Bragg Gratings

414 Chapter 9 Measurement and Characterization of Gratings

Figure 9.5: A uniform amplitude profile grating compared with a Gaussian
amplitude profile grating.

reflection is not spread over a larger bandwidth, and so the effective
length is longer. (See Fig. 9.6.)
The maximum reflectivity can be calculated by measuring the trans-
mission dip T d in dBs. The translation from the measured dip to the
reflectivity is

Figure 9.6: Comparison of chirp induced in a strong grating due to the ampli-
tude profile of the writing beam and a Gaussian profile apodized grating with
the same parameters. The FWFZ bandwidth is approximately the same, but the
slope on the long wavelength side is different, as well as the structure on the
short wavelength side.