Method and apparatus for monitoring and controlling a photonic switch using phase sweeping

Patent metadata

Field	Value
Publication number	US-10209537-B2
Application number	US-201615261486-A
Country	US
Kind code	B2
Filing date	Sep 9, 2016
Priority date	Sep 9, 2016
Publication date	Feb 19, 2019
Grant date	Feb 19, 2019

Abstract

A method and apparatus for monitoring and feedback control of a photonic switch such as 2×2 Mach-Zehnder Interferometer switch. Optical signals at an input and an output of the switch are monitored via optical taps. A sinusoidal time-varying phase shift is applied to one of the monitoring signals. An optical combiner then combines the monitoring signals. A photodetector monitors output of the optical combiner to provide a feedback signal. The amplitude of the feedback signal due to the time-varying phase shift increases with the amount of input signal present in the output signal. When the input signal is to be routed to the output (e.g. for a bar state), a controller manipulates the switch to maximize feedback signal amplitude. When the input signal is to be routed to a different output (e.g. for a cross state), the controller manipulates the switch to minimize feedback signal amplitude.

First claim

We claim:

1. An apparatus for controlling a photonic switch for controllably routing optical signals, the photonic switch having a first coupler optically coupled to at least first and second optical inputs, a phase shifter section optically coupled to the first coupler, and a second coupler optically coupled to the phase shifter section and providing optical signals to at least first and second optical outputs, the apparatus comprising:
a first optical tap located at the first optical input of the photonic switch prior to the first coupler, the first optical tap providing a first monitoring signal indicative of a signal present at the first optical input;
a second optical tap located at the first optical output of the photonic switch after the second coupler, the second optical tap providing a second monitoring signal indicative of a signal present at the first optical output;
a first phase shifter configured to apply a time-varying phase shift between the first monitoring signal and the second monitoring signal;
an optical combiner configured to combine the first monitoring signal and the second monitoring signal subsequent to application of the time-varying phase shift;
a photodetector configured to provide a feedback signal indicative of power of light output by the optical combiner, the feedback signal having a characteristic indicative of a current state of the photonic switch; and
a controller configured to receive the feedback signal and to generate a control signal for controlling the photonic switch, the control signal generated based on a combination of the feedback signal and an input signal indicative of a desired state of the photonic switch.

2. The apparatus of claim 1 , wherein the photonic switch is a Mach-Zehnder Interferometer switch.

3. The apparatus of claim 1 , wherein the photonic switch is a 2×2 switch.

4. The apparatus of claim 1 , wherein a time variation of the phase shift is sinusoidal.

5. The apparatus of claim 1 , wherein the characteristic comprises an amplitude of the feedback signal at a frequency of a time variation of the phase shift.

6. The apparatus of claim 1 , wherein the characteristic comprises an amplitude of the feedback signal at an integer multiple of a frequency of a time variation of the phase shift.

7. The apparatus of claim 1 , wherein the phase shifter is a thermal phase shifter, a carrier injection phase shifter, a carrier depletion phase shifter, a quantum-confined Stark effect phase shifter, or a Franz-Keldish effect phase shifter.

8. The apparatus of claim 1 , further comprising:
a third optical tap located at the second optical input of the photonic switch, the third optical tap providing a third monitoring signal indicative of a signal present at the second optical input;
a fourth optical tap located at the second optical output of the photonic switch, the fourth optical tap providing a fourth monitoring signal indicative of a signal present at the second optical output;
a second phase shifter configured to apply a second time-varying phase shift between the third monitoring signal and the fourth monitoring signal;
a second optical combiner configured to combine the third monitoring signal and the fourth monitoring signal subsequent to application of the second time-varying phase shift; and
a second photodetector configured to provide a second feedback signal indicative of power of light output by the second optical combiner, the second feedback signal having a second characteristic indicative of the current state of the photonic switch.

9. A photonic switch comprising the apparatus of claim 8 .

10. The apparatus of claim 1 , wherein the time-varying phase shift is configured to vary at a frequency which is higher than a desired switching frequency of the photonic switch.

11. The apparatus of claim 1 , wherein, when the desired state corresponds to the signal present at the first optical input being routed to the first optical output, the controller is configured to adjust the control signals in order to maximize an amplitude of the feedback signal at a frequency of a time variation of the phase shift or at an integer multiple of the frequency.

12. The apparatus of claim 1 , wherein, when the desired state corresponds to the signal present at the first optical input differing from the signal present at the first optical output, the controller is configured to adjust the control signals in order to minimize an amplitude of the feedback signal at a frequency of a time variation of the phase shift or at an integer multiple of the frequency.

13. A photonic switch comprising the apparatus of claim 1 .

14. The apparatus of claim 1 , wherein the controller is configured to generate the control signal to cause the photonic switch to route the signal present at the first optical input to the first optical output in response to the desired state being a first desired state, and wherein the controller is configured to generate the control signal to cause the photonic switch to route the signal present at the first optical input to the second optical output in response to the desired state being a second desired state.

15. The apparatus of claim 1 , wherein the controller is configured to apply the control signal to the phase shifter section to drive the photonic switch to the desired state based on the feedback signal.

16. A method for monitoring a photonic switch for controllably routing optical signals, the photonic switch having a first coupler optically coupled to at least first and second optical inputs, a phase shifter section optically coupled to the first coupler, and a second coupler optically coupled to the phase shifter section and providing optical signals to at least first and second optical outputs, the method comprising:
generating a first monitoring signal indicative of a signal present at the first optical input of the photonic switch prior to the first coupler;
generating a second monitoring signal indicative of a signal present at the first optical output of the photonic switch after the second coupler;
applying, using a first phase shifter, a time-varying phase shift to between the first monitoring signal and the second monitoring signal;
combining, using an optical combiner, the first monitoring signal and the second monitoring signal subsequent to application of the time-varying phase shift;
generating a feedback signal indicative of power of light output by the optical combiner, the feedback signal having a characteristic indicative of a current state of the photonic switch; and
generating a control signal for controlling the photonic switch based on a combination of the feedback signal and an input signal indicative of a desired state of the photonic switch.

17. The method of claim 16 , wherein the photonic switch is a 2×2 Mach-Zehnder Interferometer switch.

18. The method of claim 16 , wherein time variation of the phase shift is sinusoidal.

19. The method claim 16 , wherein the phase shifter is a thermal phase shifter, a carrier injection phase shifter, a carrier depletion phase shifter, a quantum-confined Stark effect phase shifter, or a Franz-Keldish effect phase shifter.

20. The method of claim 16 , further comprising:
generating a third monitoring signal indicative of a signal present at the second optical input of the photonic switch;
generating a fourth monitoring signal indicative of a signal present at the second optical output of the photonic switch;
applying, using a second phase shifter, a second time-varying phase shift b

Assignees

• Chung Ray
• Lu Zeqin
• Jayatilleka Hasitha
• Al Taha Mohammed Wadah
• Shekhar Sudip
• Mirabbasi Shahriar
• Chrostowski Lukas
• Huawei Tech Canada Co Ltd

Inventors

• Chung Ray
• Lu Zeqin
• Jayatilleka Hasitha
• Al Taha Mohammed Wadah
• Shekhar Sudip
• Mirabbasi Shahriar
• Chrostowski Lukas

Classifications

• G02F2201/58

  Arrangements comprising a monitoring photodetector · CPC title

• G02F1/3137 Primary

  with intersecting or branching waveguides, e.g. X-switches and Y-junctions · CPC title

• G02F1/3136

  of interferometric switch type · CPC title

• G02F1/3132

  of directional coupler type · CPC title

• G02F1/0123 Primary

  Circuits for the control or stabilisation of the bias voltage, e.g. automatic bias control [ABC] feedback loops · CPC title