Optical modulator having a plurality of modulator segments

• US 9,519,162 B2
• Filed: 10/09/2015
• Issued: 12/13/2016
• Est. Priority Date: 10/09/2014
• Status: Active Grant

• Current Assignee: Nokia Solutions and Networks US LLC (Nokia Corporation)
• Original Assignee: Coriant Advanced Technology, Llc (Infinera Corp.)
• Inventors: Ding, Ran, Baehr-Jones, Thomas Wetteland, Magill, Peter D., Hochberg, Michael J., Rylyakov, Alexander
• Primary Examiner(s): KIM, ELLEN E
• Application Number:
  US14/879,149
• Publication Number:
  US 20160103340A1
• Time in Patent Office: 431 Days
• Field of Search: 385/2, 385/3, 359/276, 359/237, 359/244, 359/245, 359/259, 359/315, 359/316
• US Class Current: 1/1
• CPC Class Codes: G02F 1/011 in optical waveguides, not otherwise provided for in this subclass
• CPC Class Codes: G02F 1/0121 Operation of devices; Circuit arrangements, not otherwise provided for in this subclass
• CPC Class Codes: G02F 1/025 in an optical waveguide structure G02F1/017, G02F1/2257 take precedence
• CPC Class Codes: G02F 1/035 in an optical waveguide structure
• CPC Class Codes: G02F 1/225 in an optical waveguide structure

Abstract

An optical modulator apparatus may include a plurality of segment drivers, each segment driver having a unique offset voltage and driving but a portion or a segment of an electro-optical modulator. A modulating electrical signal may be applied to the segment drivers via a plurality of electrical delays. Parameters of the segment drivers may be selected so as to approximate a pre-defined transfer function, which may include a linear or a non-linear transfer function.

Claims

1. A modulator apparatus comprising:

an optical path comprising an optical input port receiving an optical carrier wave, an optical output port outputting a modulated optical signal, and a succession of serially optically coupled optical modulator segments extending between the input and output optical ports modulating the optical carrier wave so as to obtain the modulated optical signal;

a plurality of segment drivers, wherein each segment driver has associated;

a low voltage V_low;

a high voltage V_high;

a unique offset voltage V_os; and

a threshold voltage V_th;

wherein each segment driver is electrically coupled to one of the succession of the modulator segments applies a driving voltage V_d thereto in response to a control voltage V_c, such that;

V_d=V_low when V_c<

V_os−

V_th;

V_d=V_high when V_c>

V_os+V_th; and

V_dvaries between V_low and V_high when V_c varies between V_os−

V_th and V_os+V_th;

an electrical input port receiving an electrical signal to be modulated onto the optical carrier wave to obtain the modulated optical signal;

a plurality of electrical connections between the electrical input port and each segment driver.

2. The modulator apparatus of claim 1, wherein each segment driver comprises a limiting amplifier having the corresponding low voltage V_low, the high voltage V_high, the unique offset voltage V_os, and the threshold voltage V_th.

3. The modulator apparatus of claim 2, wherein each electrical connection has a corresponding delay Δ

T_electrical between the electrical input port and each limiting amplifier; and

wherein the delays Δ

T_electrical are such that in operation, the application of the driving voltage V_d to individual optical modulator segments in the succession of optical modulator segments is substantially synchronized with propagation of the optical carrier wave therein.

4. The modulator apparatus of claim 1, further comprising a comparator module operationally coupled to the electrical input port and the plurality of segment drivers to provide individual control signals to the plurality of segment drivers when the control voltage V_c exceeds the offset voltages V_os of corresponding segment drivers of the plurality of segment drivers.

5. The modulator apparatus of claim 1, wherein the succession of serially optically coupled optical modulator segments comprises an optical waveguide and a succession of electrodes disposed along the optical waveguide and operationally coupled thereto.

6. The modulator apparatus of claim 1, wherein the plurality of electrical connections comprise a succession of serially electrically coupled electrical delay line segments,

wherein each progressive one of the succession of electrical delay line segments is electrically coupled to a segment driver of the plurality of segment drivers, and

wherein the segment driver is electrically coupled to a corresponding progressive one of the succession of optical modulator segments.

7. The modulator apparatus of claim 6, comprising more than eight optical modulator segments and more than eight segment drivers.

8. The modulator apparatus of claim 1, wherein the offset voltage V_os of each successive segment driver is greater than the offset voltage V_os of the immediately preceding segment driver, if any.

9. The modulator apparatus of claim 8, wherein the offset voltage V_os of each successive segment driver is greater than the offset voltage V_os of the immediately preceding segment driver, if any, by a same step voltage Δ

V_os.

10. The modulator apparatus of claim 1, wherein a slope of each segment driver, defined as (_{V high}−

V_low)/2V_th, is such that in operation, a degree of modulation of the modulated optical signal is substantially proportional to a magnitude of the electrical signal received at the electrical input port.

11. The modulator apparatus of claim 10, wherein the slope is less than 5.

12. The modulator apparatus of claim 1, wherein in operation, each segment driver has a delay Δ

T_amp between application of the control voltage V_c thereto and generation of the corresponding driving voltage V_d thereby, wherein the delays Δ

T_amp of at least two of the plurality of segment drivers are substantially different from one another.

13. The modulator apparatus of claim 1, wherein at least one of the low voltage V_low,the high voltage V_high, and the threshold voltage V.sub.th, of at least one segment driver of the plurality of segment drivers is substantially different from a corresponding one of the low voltage V_low, the high voltage V_high, and the threshold voltage V.sub.th of another segment driver of the plurality of segment drivers.

14. The modulator apparatus of claim 5, further comprising a silicon photonic chip comprising the optical waveguide.

15. The modulator apparatus of claim 14, wherein the silicon photonic chip comprises the plurality of segment drivers.

16. The modulator apparatus of claim 1, wherein the low voltage V_low, the high voltage V_high, and the threshold voltage V_th of each segment driver of the plurality of segment drivers are such that a degree of modulation of the modulated optical signal is a function of the electrical signal received by the electrical input port;

wherein the function is selected from the list consisting of quadratic, cubic, periodic, or an exponential function.

17. A method of modulating an optical carrier wave by an electrical signal, the method comprising:

propagating the optical carrier wave in a succession of serially optically coupled optical modulator segments; and

coupling the electrical signal to a plurality of segment drivers,

wherein each segment driver has associated;

a low voltage V_low;

a high voltage _high;

a unique offset voltage V_os; and

a threshold voltage V_th,

wherein each segment driver is electrically coupled to one of the succession of the modulator segments for applying a driving voltage V_d thereto in response to a control voltage V_c, such that;

V_d=V_low when V_c<

V_os−

V_th;

V_d=V_high when V_c>

V_os+V_th; and

V_d varies between V_low and V_high when V_c varies between V_os−

V_th and V_os+V_th.

18. The method of claim 17, wherein the electrical signal is coupled to an electrical input port, from which the electrical signal propagates to each segment driver via a plurality of electrical connections between an electrical input port and each segment driver;

wherein each electrical connection has a corresponding delay Δ

T_electrical between the electrical input port and each segment driver; and

wherein the delays Δ

T_electrical are such that the application of the driving voltage V_d to individual optical modulator segments in the succession of optical modulator segments is substantially synchronized with propagation of the optical carrier wave therein.

19. The method of claim 17, further comprising pre-selecting the offset voltage V_os of each successive segment driver to be greater than the offset voltage V_os of the immediately preceding segment driver, if any.

20. The method of claim 19, further comprising pre-selecting the low voltage V_low, the high voltage V_high, the offset voltage V_os, and the threshold voltage V_th of each segment driver of the plurality of segment drivers such that V_low of each successive segment driver is substantially equal to V_high of the immediately preceding segment driver, if any.

21. The method of claim 19, further comprising pre-selecting a slope of each segment driver, defined as (V_high−

V_low)/2V_th, so as to provide a degree of modulation of the optical carrier wave substantially proportional to a magnitude of the electrical signal received at the electrical input port.

22. A modulator apparatus comprising:

an optical path comprising an optical input port receiving an optical carrier wave, an optical output port outputting a modulated optical signal, and a plurality of serially optically coupled optical modulator segments extending between the input and output optical ports and modulating the optical carrier wave so as to obtain the modulated optical signal;

an electrical input port receiving an electrical signal to be modulated onto the optical carrier wave to obtain the modulated optical signal;

an analog to digital converter operationally coupled to the electrical input port, digitizing the electrical signal to provide a plurality of input digital signals;

a digital filter operationally coupled to the analog to digital converter, and receiving and digital filtering the plurality of input digital signals to provide a plurality of output digital signals, each of which for driving one of the plurality of optical modulator segments.

23. The modulator apparatus of claim 22, wherein the digital filter is configured to provide an amplitude pre-emphasis to lessen a non-linearity of modulation of the optical carrier wave by the electrical signal.

24. The modulator apparatus of claim 22, wherein the digital filter is configured to provide a pre-determined frequency response.

25. The modulator apparatus of claim 22, further comprising

a photodetector optically coupled to the optical output port to provide a feedback signal;

and

a controller operationally coupled to the photodetector and the digital filter to receive the feedback signal from the photodetector and provide a control signal to the digital filter in dependence on the feedback signal.