Amplitude balancing for multilevel signal transmission

An amplitude balanced (AB) optical amplifier, comprising:

• an optical preamplifier;
• a gain/loss variation modification device (VMD) in communication with said optical preamplifier;
• and
• an optical post-amplifier in communication with the gain/loss variation modification device, wherein
• said optical preamplifier is 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 a pre-amplified optical signal having a gain variation across said plurality of wavelength channels,
• said gain/loss variation modification device is constructed to modify said pre-amplified optical signal across said plurality of wavelength channels to at least partially cancel said gain variation to produce a modified optical signal, and
• said optical post-amplifier is adapted to amplify the modified optical signal to produce an output optical signal.

An amplitude balanced optical amplifying mechanism, comprising:

• a wavelength division demultiplexer;
• a plurality of optical amplifiers in communication with the wavelength division demultiplexer;
• and
• a wavelength division multiplexer in communication with the plurality of optical amplifiers, wherein
• said wavelength division demultiplexer is adapted to demultiplex an input optical signal with multiple wavelength channels into different wavelength groups, each of the which comprises a plurality of wavelength channels and carries at least one multilevel encoded signal,
• said plurality of optical amplifiers are adapted to amplify optical signals contained in wavelength channels of different wavelength groups to produce amplified signals, and
• said wavelength division multiplexer is adapted to multiplex the amplified signals from said plurality of optical amplifiers corresponding to different wavelength groups to produce an output optical signal.