Patent ID: 7196840

Claim:
An amplitude balanced (AB) optical amplifier, comprising: an optical preamplifier; and a gain/loss variation modification device (VMD) in optical communication with said preamplifier, wherein said optical preamplifier has a gain profile adapted to amplify a wavelength division multiplexed optical signal comprising a plurality of wavelength channels in which at least one of said plurality of wavelength channels includes a multilevel encoded signal to produce an amplified optical signal having a gain variation across said plurality of wavelength channels, and wherein said gain/loss variation modification device is constructed to modify said amplified optical signal across said plurality of wavelength channels, said gain/loss modification device having a gain/loss profile substantially complementary to said gain variation of said optical preamplifier so as to at least partially cancel said gain variation introduced by said optical preamplifier, wherein said at least one of said plurality of wavelength channels includes a hybrid signal comprising at least one multilevel signal and at least one on-off-keyed signal.