Page 297 - Fiber Bragg Gratings

274 Chapter 6 Fiber Grating Band-pass Filters

Figure 6.38: The polarization dividing band-pass filter in operation. The
dashed arrows indicate the direction of propagation. The circles with arrows
indicate the circularity of the polarization (after Ref [72]) PBS is a polarizing
beam splitter. A/4 PC is a quarter-wave polarization controller.

reflected polarization is routed to the output port of the coupler, reconsti-
tuting the original polarization, but is rotated by 77/2.
The experimental arrangement using a cascade of four chirped grat-
ings with two polarizing beam splitter band-pass filters (PBS-BPFs) is
shown in Fig 6.39. The quarter-wave plates are simply a few turns of
fiber in a polarization controller [70]. In this dispersion-compensating

Figure 6.39: Dispersion compensation with four cascaded 8-mm-long, 12-nm
bandwidth-chirped gratings and two PDBPF. The two polarization splitting band-
pass filters shown here have been cascaded to enhance the dispersive effect of
the chirped gratings [71,72].