Optical modulator having reduced bandwidth requirements and method of operation thereof
View Patent ↗An optical modulator is overdriven to increase its nonlinearity and therefore improve its response as it pertains to differential phase shift keyed (DPSK) transmission and a method of operating the same. In one embodiment, the MZM includes an MZM drive circuit coupled to the electrodes and configured to deliver to the electrode a DPSK drive signal bearing digital data and having a voltage that exceeds a normal drive voltage of the MZM by at least about 20%.
1. A method of driving a Mach-Zehnder modulator (MZM) having first and second waveguide arms coupled at ends thereof and electrodes associated therewith, said method comprising:
delivering to said electrodes a differential phase shift keyed (DPSK) drive signal bearing digital data at a rate at least twice a bandwidth of said MZM, and having a voltage controlling each waveguide arm of said MZM set at a level that exceeds a halfwave voltage, V π , of said MZM by at least 5%.
2. The method as recited in claim 1 wherein said voltage exceeds said V π of said MZM by at least 15%.
3. The method as recited in claim 1 wherein said voltage exceeds said V π of said MZM by at least 30%.
4. The method as recited in claim 1 wherein a power penalty of said MZM at said data rate is substantially minimized.
5. The method as recited in claim 1 wherein said MZM produces a differential quadrature phase shift keyed (DQPSK) optical pulsetrain.
6. The method as recited in claim 1 wherein said MZM operates at about a 40 GB/s rate.
7. The method as recited in claim 1 wherein said MZM has a bandwidth that is at most 40% of said rate of said digital data.
8. An optical communication system comprising:
a Mach-Zehnder Modulator (MZM) having first and second waveguide arms coupled at ends thereof and electrodes associated therewith; and
an MZM drive circuit coupled to said electrodes and configured to deliver to said electrodes a differential phase shift keyed (DPSK) drive signal bearing digital data at a bit rate at least twice a nominal bandwidth of said MZM, wherein a voltage controlling each waveguide arm of said MZM is set at a level that substantially minimizes a power penalty at said bit rate.
9. The optical communication system as recited in claim 8 , wherein said controlling voltage exceeds a halfwave voltage, V π , of said MZM.
10. The optical communication system as recited in claim 8 , wherein said nominal bandwidth is less than about 35% of said bit rate.
11. The optical communication system as recited in claim 8 , wherein said MZM is configured to produce a differential quadrature phase shift keyed (DQPSK) optical pulsetrain.
12. The optical communication system as recited in claim 8 , wherein said MZM operates at about a 40 GB/s rate.
13. A method of operating a Mach-Zehnder Modulator (MZM) comprising the steps of:
modulating a voltage that controls a phase shift in waveguide arms of said MZM at a modulation rate at least twice a nominal bandwidth of said MZM; and
selecting a level of said voltage to substantially minimize a power penalty at said modulation rate.
14. The method as recited in claim 13 , wherein said nominal bandwidth is less than about 35% of said rate.
15. The method as recited in claim 13 , wherein modulating said voltage produces a differential quadrature phase shift keyed (DQPSK) optical pulsetrain.
16. The method as recited in claim 13 , wherein said MZM operates at about a 40 GB/s rate.
17. The method as recited in claim 13 , wherein said voltage level is greater than a halfwave voltage, V π , of said MZM.
18. The method as recited in claim 17 wherein said voltage exceeds said V π by at least 30%.