Patent ID: 6374000
Filing Date: 2002-04-16
Classification: G02F

Abstract:
A method of modulating light in a modulator circuit comprising a Mach-Zehnder modulator having at least one optical input and at least one optical output, the Mach-Zehnder modulator modulating light, which is fed to the input of the Mach-Zehnder modulator, in response to applied electrical modulation signals, the modulator circuit additionally comprising:a driver circuit for generating a driver signal with a logic â€œ1â€  and a logic â€œ0â€  in response to a data signal; a pilot tone generator for generating a pilot tone having a frequency essentially different from the frequency of the driver signal, the modulation signals being formed by the driver signal and the pilot tone; and a photoelectrical converter circuit for providing an electrical feedback signal in response to the optical output signal of the Mach-Zehnder modulator; characterized in that the photoelectrical converter circuit is connected to and generates a feedback signal for a feedback circuit which is also connected to the pilot tone generator, the feedback circuit being adapted, in response to the pilot tone signal fed from the pilot tone generator and the feedback signal fed from the photoelectrical converter circuit, to generate driver control signals for the driver circuit to regulate the driver signal fed to the Mach-Zehnder modulator.