Method for generating an optimized return-to-zero pulse shape against aggressive optical filtering and an optical transmitter implementing the method

摘要

An optical transmitter comprises: first and second sets of optical in-phase and quadrature modulators; an integrable tunable laser assembly; a first polarization beam splitter that is configured to divide the continuous-waveform optical signal into a x-polarized tributary and a y-polarized tributary, each of the x-polarized tributary and the y-polarized tributary is modulated by one of the first and second sets of optical in-phase and quadrature modulators in accordance with the two respective input signals; a second polarization beam splitter that is configured to combine the modulated x-polarized tributary and the modulated y-polarized tributary into one optical signal; and an optical modulator that is configured to modulate the combined optical signal using a driving voltage, wherein the driving voltage has a bias point that is reduced by a predefined offset from a predefined reference voltage level.

主权项

1. A method of generating a signal having an optimized return-to-zero pulse shape using an optical transmitter, the optical transmitter including first and second sets of optical in-phase and quadrature modulators, an integrable tunable laser assembly, a first polarization beam splitter, a second polarization beam splitter, and an optical modulator having an input terminal and an output terminal, the method comprising:
generating a continuous-waveform optical signal using the integrable tunable laser assembly and dividing the continuous-waveform optical signal into an x-polarized tributary and a y-polarized tributary using the first polarization beam splitter; modulating the x-polarized tributary using the first set of optical in-phase and quadrature modulators in accordance with a pair of input signals applied to the first set of optical in-phase and quadrature modulators; modulating the y-polarized tributary using the second set of optical in-phase and quadrature modulators in accordance with a pair of input signals applied to the second set of optical in-phase and quadrature modulators; combining the modulated x-polarized tributary and the modulated y-polarized tributary into one optical signal using the second polarization beam splitter; applying a clock signal and a driving voltage to the optical modulator, wherein the driving voltage has a bias point at a predefined reference voltage level; modifying the driving voltage by reducing the bias point of the driving voltage from the predefined reference voltage level by a predefined offset; receiving the optical signal from the second polarization beam splitter at the input terminal of the optical modulator, wherein the optical signal includes the x-polarized tributary and the y-polarized tributary that is pulse-to-pulse aligned with the x-polarized tributary; modulating the optical signal using the modified driving voltage; and exporting the modulated optical signal at the output terminal of the optical modulator.