The signal of wavelength then outputs to port 3, where it is dropped. A second signal with wavelength arrives at the port 4 of the second circulator (whose ports are numbered 4,5, 6 to avoid confusion). This added signal proceeds to port 5, reflected by Bragg grating and re-enters port 5 as an input. The signal, along with is output at port 6.
Bidirectional OADM using Optical Circulators and FBG
We can design a bidirectional OADM using two four port circulators and wavelength selective fiber gratings.
then outputs to port 3, where it is dropped. A second signal with wavelength 
arrives at the port 4 of the second circulator (whose ports are numbered 4,5, 6 to avoid confusion). This added signal proceeds to port 5, reflected by Bragg grating and re-enters port 5 as an input. The signal, along with 
is output at port 6.![\includegraphics[height=4in]{wdm11.eps}](../../Fig/math-images/math_clip_image039.gif)
