A monodirectional FBG Reflector is defined as the FBG based device that maintain all the transmitting values in line with the given datasheet only when the 1650nm signal direction is “FORWARD” one.
A bidirectional FBG reflector is defined as the FBG based device that maintain all the transmitting values inline with the given datasheet when the 1650nm signal is on the “FORWARD” on “BACKWARD” sides.
For bothe device all over the Passband Wavelength the device must be in line with datasheet over both signal sides (“FORWARD” and BACKWARD”).