Patent ID: 9614639
Date: 2017-04-04
CPC Classifications: H04B,H04J

Claim:
1. An optical communication apparatus, comprising: a first modulator, which is configured to receive and modulate a first optical signal at a first frequency corresponding to a first tone, the first modulator outputting a modulated first optical signal; a second modulator, which is configured to receive and modulate a second optical signal at a second frequency corresponding to a second tone, the second modulator outputting a modulated second optical signal, the first and second tones being different; a waveguide configured to receive the modulated first and second optical signals, the modulated first and second optical signals carrying data at a bit rate, the modulated first optical signal being polarized to have a first polarization and the modulated second optical signal being polarized to have a second polarization, the modulated first optical signal having a wavelength and the modulated second optical signal having said wavelength, the bit rate, as measured in Hz, being greater than the first and second frequencies, as measured in Hz; an optical tap coupled to the waveguide, the optical tap being configured to supply a portion of the modulated first optical signal and a portion of the modulated second optical signal; a photodiode configured to receive first and second optical signal portions and generate first and second electrical signals, the first electrical signal including a first spectral component associated with the first tone and a second spectral component based on the second tone; a processor circuit configured to receive the first electrical signal and the second electrical signal and generate a control signal based on the first and second spectral components, such that a power level associated with the modulated first optical signal is adjusted by a first variable optical attenuator in response to the control signal, wherein the control signal is a first control signal and the power level is a first power level, the processor circuit further being configured to generate a second control signal based on the first and second spectral components, such that a second power level associated with the second optical signal is adjusted by a second variable optical attenuator in response to the second control signal; the first variable optical attenuator being coupled to the processor circuit, the first variable optical attenuator receiving first continuous wave (CW) light and supplying attenuated first light as the first optical signal to the first modulator, such that the first variable optical attenuator is configured to adjust the first power level based on the first tone; and the second variable optical attenuator being coupled to the processor circuit, the second variable optical attenuator receiving second CW light and supplying attenuated second light as the second optical signal to the second modulator, such that the second variable optical attenuator configured to adjust the second power level based on the second tone.