A. M. Vengsarkar et al., ‘Long-period fiber-grating-based gain equalizers,’ Opt. Lett.,
vol.21, No.5, (1996), pp.336-338.


The example demonstrates a fiber grating filter used to equalize the gain of a fiber
amplifier. The LP01 fiber core mode is coupled to the LP08 cladding mode. A twograting
structure is present in the fiber. The gratings are uniform and have different

The main result is the transmission spectrum of the fiber grating filter. The spectrum
is very close to the inverted gain spectrum of the Erbium doped amplifier.
Consequently, gain flattening can be achieved by introduction of such a filter after the
amplifier section.

Optical Grating - Waveguide