Low distortion high bandwidth adaptive transmission line for integrated photonics applications
A transmission line and method for implementing includes a plurality of segments forming an electrical path and a continuous optical path passing through the segments. Discrete inductors are formed between and connect adjacent segments. The inductors are formed in a plurality of metal layers of an integrated circuit to balance capacitance of an optical modulator which includes the transmission line to achieve a characteristic impedance for the transmission line.
1. A method for implementing a broadband transmission line, comprising:
balancing capacitance of an optical modulator of a broadband transmission line to achieve a characteristic impedance for the transmission line by connecting a discrete inductor between adjacent segments of the transmission line; and
tuning a control circuit to match velocity between an electrical signal and an optical signal traveling in the transmission line.
2. The method as recited in claim 1 , further comprising forming the inductor in a plurality of metal layers of an integrated circuit to reduce series resistance and increase inductance.
3. The method as recited in claim 1 , wherein tuning includes inserting an optical delay line in an optical path.
4. The method as recited in claim 1 , wherein tuning includes comparing phases of the electrical signal and of the optical signal using a delay locked loop.
5. The method as recited in claim 1 , wherein tuning includes adjusting a varactor coupled to a segment capacitance.
6. The method as recited in claim 1 , wherein the optical signal in an optical path is monitored using an optical tap circuit.
7. The method as recited in claim 1 , further comprising contacting an optical waveguide with one or more discrete inductors that are smaller in length than a total modulator length to achieve periodic loading by active loading elements of the transmission line.
8. The method as recited in claim 4 , wherein comparing phases of the electrical signal and of the optical signal includes comparing electrical edge and optical edge arrival times using a phase detector.
9. The method as recited in claim 8 , wherein using the phase detector includes filtering an output of the phase detector with a loop filter, which filters the electrical signal and the optical signal and controls a plurality of varactors to ensure matching delays.
10. A method for implementing a broadband transmission line, comprising:
balancing capacitance of an optical modulator of a broadband transmission line to achieve a characteristic impedance for the transmission line by connecting a discrete inductor between adjacent segments of the transmission line such that a number of discrete inductor-capacitor segments is small enough to keep the segments' physical dimensions below a wavelength of an electrical signal traveling down the transmission line; and
tuning a control circuit to match velocity between an electrical signal and an optical signal traveling in the transmission line.
11. The method as recited in claim 10 , further comprising forming the inductors in a plurality of metal layers of an integrated circuit to reduce series resistance and increase inductance.
12. The method as recited in claim 10 , wherein tuning includes inserting an optical delay line in an optical path.
13. The method as recited in claim 10 , wherein tuning includes comparing phases of the electrical signal and of the optical signal using a delay locked loop.
14. The method as recited in claim 13 , wherein comparing phases of the electrical signal and of the optical signal includes comparing electrical edge and optical edge arrival times using a phase detector.
15. The method as recited in claim 14 , wherein using the phase detector includes filtering an output of the phase detector with a loop filter, which filters the electrical signal and the optical signal and controls a plurality of varactors to ensure matching delays.
16. The method as recited in claim 10 , wherein tuning includes adjusting a varactor coupled to a segment capacitance.
17. The method as recited in claim 10 , wherein the optical signal in an optical path is monitored using an optical tap circuit.
18. The method as recited in claim 10 , further comprising contacting an optical waveguide with one or more discrete inductors that are smaller in length than a total modulator length to achieve periodic loading by active loading elements of the transmission line.