Dispersion compensator for frequency reshaped optical signals
View Patent ↗An optical transmitter is disclosed including an optical signal source generating a frequency modulated signal encoding data. An optical spectrum reshaper is positioned to receive the frequency modulated signal and converts the frequency modulated signal into a reshaped signal having increased amplitude modulation relative to the frequency modulated signal. A third-order dispersive element is positioned to receive the reshaped signal and is adapted to impose third-order dispersion on the reshaped signal to generate a compensated signal having third-order dispersion effective to compensate for second-order dispersion caused by an optical fiber positioned between the optical transmitter and a receiver.
1. An optical transmitter comprising:
a digital signal source configured to output a data signal;
an optical signal source coupled to the digital signal source and configured to output a frequency modulated signal encoding the data signal;
an optical spectrum reshaper positioned to receive the frequency modulated signal and adapted to convert the frequency modulated signal into a reshaped signal having increased amplitude modulation relative to the frequency modulated signal;
a third-order dispersive element positioned to receive the reshaped signal and adapted to impose third-order dispersion on the reshaped signal to generate a compensated signal; and
an optical fiber having a first end positioned to receive the compensated signal and a second end coupled to a receiver; and
wherein the third-order dispersive element imposes third-order dispersion effective to compensate for second-order dispersion caused by the optical fiber.
2. The optical transmitter of claim 1 , wherein the an optical spectrum reshaper is adapted to convert the frequency modulated signal into a reshaped signal having amplitude and frequency modulation, wherein a duty cycle of the amplitude modulation is greater than a duty cycle of the frequency modulation.
3. The optical transmitter of claim 1 , wherein the third-order dispersive element is a filter having a Gaussian profile and wherein the reshaped signal has a frequency profile positioned relative to the transmission function of the Gaussian profile such that the reshaped signal experiences third-order dispersion.
4. The optical transmitter of claim 1 , further comprising a second-order dispersive element having second-order dispersion having a sign opposite that of second-order dispersion in the optical fiber and positioned between the third-order dispersive element and the optical fiber.
5. The optical transmitter of claim 4 , wherein the second-order dispersive element comprises an all-pass filter.
6. The optical transmitter of claim 4 , wherein the second-order dispersive element comprises at least one ring resonator filter.
7. The optical transmitter of claim 4 , wherein the second-order dispersive element comprises two Gire-Tournois filters.
8. A method for transmitting data comprising:
modulating an optical signal source to generate a first signal having frequency modulation encoding a data signal;
transmitting the first signal through an optical spectrum reshaper to generate a second signal having amplitude and frequency modulated pulses encoding the data signal, the pulses having a center portion and leading and trailing portions, the leading and trailing portions having a lower frequency than the center portion;
transmitting the second signal through a third-order dispersive element to generate a third signal; and
transmitting the third signal through an optical fiber to a receiver, the third-order dispersive element imposing third-order dispersion effective to compensate for distortion caused by second-order dispersion of the optical fiber.
9. The method of claim 8 , wherein transmitting the second signal through a third-order dispersive element to generate a third signal comprises transmitting the second signal through an optical filter having a Gaussian profile, the second signal having a frequency profile positioned on the transmission function of the Gaussian profile such that the reshaped signal experiences third-order dispersion.
10. The method of claim 8 , further comprising transmitting the third signal through a second-order dispersive element having second-order dispersion having a sign opposite that of the optical fiber.
11. The method of claim 10 , wherein the second-order dispersive element comprises at least one of a ring resonator filter and a Gire-Tournois filter.
12. An optical transmitter comprising:
a digital signal source configured to output a data signal;
an optical signal source coupled to the digital signal source and configured to output a frequency modulated signal encoding the data signal;
an optical spectrum reshaper positioned to receive the frequency modulated signal and output a reshaped signal, the optical spectrum reshaper having a transmission function having a transmission edge overlapping a frequency modulation bandwidth of the frequency modulated signal; and
an optical filter having a transmission function having a portion overlapping the transmission edge that is effective to impose third-order dispersion on the reshaped signal.
13. The optical transmitter of claim 12 , further comprising an optical fiber having a first end positioned to receive the compensated signal and a second end coupled to a receiver; and wherein the optical filter imposes third-order dispersion effective to compensate for second-order dispersion caused by the optical fiber.
14. The optical transmitter of claim 13 , further comprising a second-order dispersive element having second-order dispersion having a sign opposite that of the optical fiber and positioned between the third-order dispersive element and the optical fiber.
15. The optical transmitter of claim 14 , wherein the second-order dispersive element comprises an all-pass filter.
16. The optical transmitter of claim 15 , wherein the second-order dispersive element comprises at least one of a ring resonator filter and a Gire-Tournois filter.
17. An optical transmitter comprising:
a digital signal source configured to output a data signal;
an optical signal source coupled to the digital signal source and configured to output a frequency modulated signal encoding the data signal;
an optical spectrum reshaper positioned to receive the frequency modulated signal and adapted to convert the frequency modulated signal into a reshaped signal having increased amplitude modulation relative to the frequency modulated signal;
a third-order dispersive element positioned to receive the reshaped signal and adapted to impose third-order dispersion on the reshaped signal to generate a compensated signal, the third-order dispersive element having a transmission function effective to substantially reverse third-order dispersion imposed by the optical spectrum reshaper.
18. The optical transmitter of claim 17 , wherein the third-order dispersive element has a Gaussian transmission profile and wherein the reshaped signal has a frequency bandwidth positioned on the Gaussian transmission profile such that the reshaped signal experiences third-order dispersion.
19. The optical transmitter of claim 17 , further comprising an optical fiber having a first end positioned to receive the compensated signal and a second end coupled to a receiver; and wherein the optical filter imposes third-order dispersion effective to compensate for second-order dispersion caused by the optical fiber.
20. The optical transmitter of claim 17 , further comprising a second-order dispersive element having second-order dispersion having a sign opposite that of the second-order dispersion in the optical fiber and positioned between the third-order dispersive element and the optical fiber.
21. The optical transmitter of claim 20 , wherein the second-order dispersive element comprises an all-pass filter.