Segmented modulator for high-speed opto-electronics

• US 20030235359A1
• Filed: 06/20/2002
• Published: 12/25/2003
• Est. Priority Date: 06/20/2002
• Status: Active Grant

• Current Assignee: Qorvo US, Inc. (Qorvo, Inc.)
• Original Assignee: TriQuint Technology Holding Co (Qorvo, Inc.)
• Inventors: Mason, Thomas Gordon Beck, Freund, Joseph Michael, Lentz, Charles William, Geary, John Michael, Walters, Frank Stephen
• Granted Patent: US 6,990,256 B2
• Time in Patent Office: Days
• US Class Current: 385/2
• CPC Class Codes: G02F 1/015 based on semiconductor elements having potential barriers, e.g. having a PN or PIN junction G02F1/03 takes precedence
• CPC Class Codes: G02F 1/0157 using electro-absorption effects, e.g. Franz-Keldysh [FK] effect or quantum confined stark effect [QCSE]
• CPC Class Codes: G02F 1/0356 controlled by a high-frequency electromagnetic wave component in an electric waveguide structure
• CPC Class Codes: G02F 2201/16 series; tandem

Abstract

An optical modulator includes first and second modulator segments. The first and second modulator segments form an optical signal path for an optical signal. The optical modulator also includes an electrical signal path capable of receiving and carrying a modulation signal, which is applied to the optical signal at the first and second modulation segments to generate a modulated optical signal. An inductive element may be disposed between electrical inputs to the first and second modulator segments. The optical modulator may be an electro-absorption modulator (EAM). The inductive element may be an inductor or a transmission line segment.

Claims

1. An optical modulator suitable for application in a transmitter, said optical modulator comprising:

a first modulator segment;

a second modulator segment, said first and second modulator segments comprising an optical signal path for an optical signal; and

an electrical signal path capable of receiving and carrying a modulation signal,

wherein the modulation signal is applied to the optical signal at said first and second modulation segments to generate a modulated optical signal.

2. The optical modulator according to claim 1, wherein the first and second modulator segments comprise segments of an electro-absorption modulator (EAM).

3. The optical modulator according to claim 1, said optical modulator capable of operating as a transmission line, wherein propagation velocity on the transmission line substantially matches an optical velocity on the optical signal path.

4. The optical modulator according to claim 1, wherein the electrical signal path comprises an inductive element disposed between the first and second modulator segments.

5. The optical modulator according to claim 4, wherein the inductive element comprises a transmission line segment having a first characteristic impedance, said first characteristic impedance being higher than a characteristic impedance of a transmission line comprising the first modulator segment, the second modulator segment and the inductive element.

6. The optical modulator according to claim 4, wherein the inductive element comprises an inductor.

7. The optical modulator according to claim 4, wherein the inductive element comprises a transmission line segment having a first propagation velocity, said first propagation velocity being higher than a propagation velocity of a transmission line comprising the first modulator segment, the second modulator segment and the inductive element.

8. The optical modulator according to claim 4, wherein the electrical signal path further comprises at least one inductive element at an input of the first modulator segment, and at least one inductive element at an output of the second modulator segment.

9. The optical modulator according to claim 1, wherein the distance between the first and second modulator segments is greater than at least one of the length of the first modulator segment and the length of the second modulator segment.

10. The optical modulator according to claim 5, wherein the length of a portion of the electrical signal path between the first and second modulator segments is greater than at least one of the length of the first modulator segment and the length of the second modulator segment.

11. The optical modulator according to claim 10, wherein the length of said portion of the electrical signal path between the first and second modulator segments is lengthened by meandering the transmission line segment.

12. The optical modulator according to claim 10, wherein the length of said portion of the electrical signal path between the first and the second modulator segments is determined to substantially match a propagation delay of the modulation signal on said portion of the electrical signal path between said modulator segments to the propagation delay of the optical signal on the optical signal path between said modulator segments.

13. The optical modulator according to claim 4, further comprising a resistive element in series with the inductive element, wherein the resistive element is capable of impedance matching.

14. The optical modulator according to claim 3, wherein the optical modulator is mounted on a submount selected from a group consisting of silicon (Si), aluminum nitride (AlN), alumina and beryllium oxide (BeO).

15. The optical modulator according to claim 14, wherein the optical modulator is implemented on a chip, and wherein the transmission line is formed partly on the optical modulator chip and partly on the submount.

16. The optical modulator according to claim 15, wherein a substrate of the optical modulator chip forms a ground plane for the transmission line.

17. The optical modulator according to claim 15, wherein the submount has formed thereon at least two ground planes and a center trace between them, wherein said at least two ground planes and the center trace form a coplanar waveguide.

18. The optical modulator according to claim 1, wherein a center-to-center distance between the first and second modulator segments is substantially less than the wavelength corresponding to an expected maximum frequency during operation.

19. The optical modulator according to claim 18, wherein the center-to-center distance is approximately (1/2π

)th of said wavelength corresponding to the expected maximum frequency.

20. A transmitter comprising:

an optical source capable of generating an optical signal;

an optical modulator capable of receiving the optical signal and a modulation signal, applying the modulation signal to the optical signal to generate a modulated optical signal; and

a data modulator capable of receiving the modulated optical signal and a data signal, and applying the data signal to the modulated optical signal to generate an optical data signal,

wherein at least one of the optical modulator and the data modulator comprises;

a first modulator segment; and

a second modulator segment, said first and second modulator segments comprising an optical signal path for the optical signal or the modulated optical signal, respectively,

wherein the modulation signal or the data signal is applied, respectively, to the optical signal or the modulated optical signal at said first and second modulation segments to generate the modulated optical signal or the optical data signal, respectively.

21. An optical transmission system comprising:

a transmitter capable of generating and transmitting an optical data signal;

a transmission medium over which the optical data signal can be transmitted; and

a receiver capable of receiving the optical data signal,

wherein the transmitter comprises an optical modulator comprising;

a first modulator segment; and

a second modulator segment, said first and second modulator segments comprising an optical signal path for an optical signal,

wherein the modulation signal is applied to the optical signal at said first and second modulation segments to generate the optical data signal.

22. A method of improving a frequency characteristic of an optical modulator comprising;

dividing the optical modulator into a plurality of modulator segments; and

disposing an inductive element between electrical inputs of at least two of the modulator segments.

23. The method according to claim 22, further comprising disposing a semiconductor optical amplifier (SOA) between at least two of the modulator segments, wherein the SOA is capable of boosting the optical signal between the first and second modulator segments.

24. The method according to claim 22, wherein disposing the inductive element comprises elongating the inductive element by shaping it into a non-straight pattern,

whereby a propagation delay of an electrical signal between said at least two of the modulator segments is substantially matched to the propagation delay of the optical signal.