Patent ID: 9246597
Filing Date: 2016-01-26
CPC Classification: H04B

Claim Text:
1. An apparatus, comprising: a trellis coding modulation (TCM) encoder circuit configured to output first and second encoded data in response to first data; a first driver circuit configured to supply first drive signals in response to the first and second encoded data; a first modulator configured to supply a first modulated optical signal having a first wavelength in response to the first drive signals; a second drive circuit configured to receive second and third data and supply second drive signals in response to the second and third data; a second modulator configured to output a second modulated optical signal in response to the second drive signals, the second modulated optical signal having a second wavelength different than the first wavelength; and an optical amplifier configured to be coupled to an optical communication link, the optical amplifier having a gain spectrum, such that a first spectral range within the gain spectrum has an associated first gain and a tail of the gain spectrum, which is a second spectral range within the gain spectrum, has an associated second gain, the first gain being greater than the second gain, such that the first wavelength of the first optical signal is within the first spectral range and the second wavelength of the second optical signal is within the tail of the gain spectrum, wherein the first modulated optical signal is modulated in accordance with a QPSK modulation format and the second modulated optical signal is modulated in accordance with a TCM-QPSK modulation format, such that the second modulated optical signal is a QPSK modulated optical signal that carries TCM encoded information.