Optical coherent transmitter on a silicon chip
Embodiments described herein may be related to apparatuses, processes, and techniques related to fully integrated optical coherent modulators on a silicon chip. These coherent modulators may be used to enable transmitters, receivers, transceivers, tunable lasers and other optical or electro-optical devices to be integrated on a silicon chip. In embodiments, the optical coherent modulators may be based on differential microring modulators that may be nested in a Mach-Zehnder Interferometer (MZI) configuration. Embodiments may also be directed to a miniaturized and fully integrated coherent modulators, which can enable terabit per second (Tbps) transceivers in a small form factor based on coherent modulation on a silicon chip. Other embodiments may be described and/or claimed.
1. An apparatus, comprising:
a tunable laser to output a light beam; and
a coherent modulator coupled to the tunable laser to modulate the light beam, wherein the tunable laser and the coherent modulator are integrated on a silicon photonics chip, and the coherent modulator comprises:
an input waveguide coupled to the tunable laser;
first and second arms coupled to the input waveguide;
a first microring modulator coupled to the first arm and comprising first and second respective coupling segments and a respective thermal phase shifter between the first and second respective coupling segments; and
a second microring modulator coupled to the second arm and comprising first and second respective coupling segments and a respective thermal phase shifter between the first and second respective coupling segments; wherein the input waveguide is a first input waveguide, and the apparatus further comprises:
a second input waveguide coupled to the tunable laser;
third and fourth arms coupled to the second input waveguide;
a third microring modulator coupled to the third arm and comprising first and second respective coupling segments and a respective thermal phase shifter between the first and second respective coupling segments; and
a fourth microring modulator coupled to the fourth arm and comprising first and second respective coupling segments and a respective thermal phase shifter between the first and second respective coupling segments.
2. The apparatus of claim 1 , further including an optical receiver coupled to the tunable laser, wherein an output of the tunable laser is split into a first waveguide that serves as an input to the coherent modulator and a second waveguide that serves as a local oscillator (LO) optical signal for the optical receiver.
3. The apparatus of claim 1 , wherein the silicon photonics chip is a hybrid III-V/Si photonics chip.
4. The apparatus of claim 1 , wherein the tunable laser is tuned using thermo-optic tuning.
5. The apparatus of claim 1 , wherein the first and second microring modulators are nested in a Mach-Zehnder Interferometer (MZI) configuration.
6. The apparatus of claim 1 , wherein the coherent modulator comprises an I/Q modulator.
7. The apparatus of claim 1 , further comprising a tunable coupler between the modulator and an input bus waveguide.
8. The apparatus of claim 1 , wherein the coherent modulator is a dual polarization coherent modulator.
9. A method for coherent optical transmission, the method comprising:
receiving, by a coherent modulator, an optical signal from a tunable laser co-disposed with the coherent modulator on a silicon photonics chip, wherein the coherent modulator includes a differential microring modulator;
mixing I and Q signals of the optical signal to generate pre-chirp I and Q input signals, respectively, for the coherent modulator;
modulating, by the coherent modulator, the pre-chirp I and Q input signals to produce a modulated optical signal; and
transmitting the modulated optical signal.
10. The method of claim 9 , further comprising tuning the tunable laser using thermo-optic tuning.
11. The method of claim 10 , wherein the coherent modulator is a resonator-based coherent modulator with each I or Q modulator using a differential Mach-Zehnder Interferometer (MZI) architecture.
12. The method of claim 11 , wherein the differential MZI architecture uses microring modulators in each arm.
13. The method of claim 9 , wherein the mixing includes adding a chirp of opposite sign to the I and Q signals of the optical signal.
14. A system, comprising:
a tunable laser to output a light beam;
an optical transmitter comprising a coherent modulator, wherein the coherent modulator comprises differential microring modulators and is coupled to the tunable laser to modulate the light beam; and
a chirp pre-correction I/Q equalizer to reduce a chirp of the coherent modulator, wherein the tunable laser and the optical transmitter are integrated on a silicon photonics chip, wherein coefficients of the chirp pre-correction I/Q equalizer are based on parameters of the differential microring modulators.
15. The system of claim 14 , further comprising an optical waveguide coupled with an optical output of the optical transmitter to transmit the modulated light beam, wherein the optical waveguide comprises at least one of an optical fiber or a silicon waveguide.
16. The system of claim 14 , wherein the differential microring modulators are nested in a Mach-Zehnder Interferometer (MZI) configuration.
17. The system of claim 14 , wherein the coherent modulator comprises an I/Q modulator.
18. The system of claim 14 , wherein the coherent modulator is a dual polarization coherent modulator.