Common cathode laser driving circuit

• US 10,103,513 B1
• Filed: 06/23/2017
• Issued: 10/16/2018
• Est. Priority Date: 06/23/2017
• Status: Active Grant

• Current Assignee: Google LLC (Alphabet Inc.)
• Original Assignee: Google LLC (Alphabet Inc.)
• Inventors: Zhang, Tao, Du, Liang, Zhao, Xiangjun, Jiang, Changhong Joy, Lam, Cedric Fung, Yin, Shuang, Barratt, Adam Edwin Taylor
• Primary Examiner(s): Carter, Michael
• Application Number:
  US15/631,594
• Time in Patent Office: 480 Days
• CPC Class Codes: H01S 5/042 Electrical excitation ; Circuits therefor monolithically integrated laser drive components H01S5/0261
• CPC Class Codes: H01S 5/0428 for applying pulses to the laser
• CPC Class Codes: H01S 5/06256 with DBR-structure
• CPC Class Codes: H01S 5/068 Stabilisation of laser output parameters H01S5/0625 takes precedence
• CPC Class Codes: H01S 5/125 Distributed Bragg reflector [DBR] lasers
• CPC Class Codes: H01S 5/3013 AIIIBV compounds
• CPC Class Codes: H04B 10/2589 Bidirectional transmission
• CPC Class Codes: H04B 10/40 Transceivers
• CPC Class Codes: H04J 14/0265 Multiplex arrangements in bidirectional systems, e.g. interleaved allocation of wavelengths or allocation of wavelength groups
• CPC Class Codes: H04J 14/0282 WDM tree architectures

Abstract

A method for biasing a tunable laser during burst-on and burst-off states through a common-cathode laser driving circuit includes delivering a bias current to an anode of a gain-section diode having a shared substrate with the laser, and receiving a burst mode signal indicative of a burst-on state or a burst-off state. When the burst mode signal is indicative of the burst-off state, the method includes sinking a sink current away from the anode of the gain-section diode. The sink current is less than the bias current delivered to the anode of the gain-section diode. When the burst mode signal transitions to be indicative of the burst-on state from the burst-off state, the method includes ceasing the sinking of the sink current away from the anode of the gain-section diode, and delivering an overshoot current to the anode of the gain-section diode to accelerate heating of the gain-section diode.

Claims

1. A method comprising:

delivering, by a laser driving circuit, a bias current to an anode of a gain-section diode disposed on a shared substrate of a tunable laser;

receiving, at the laser driving circuit, a burst mode signal indicative of a burst-on state or a burst-off state;

receiving, at the laser driving circuit, a sink current adjustment from a sinking stage of the laser driving circuit, the sink current adjustment configured to adjust a sink current;

when the burst mode signal is indicative of the burst-off state;

sinking, by the laser driving circuit, the sink current away from the bias current at the anode of the gain-section diode, the sink current less than the bias current delivered to the anode of the gain-section diode; and

when the burst mode signal transitions to be indicative of the burst-on state from the burst-off state;

ceasing, by the laser driving circuit, the sinking of the sink current away from the bias current at the anode of the gain-section diode; and

delivering, by the laser driving circuit, an overshoot current to the anode of the gain-section diode to accelerate heating of the gain-section diode.

2. The method of claim 1, wherein when the burst mode signal is indicative of the burst-off state, the gain-section diode receives a diode current equal to the bias current minus the sink current.

3. The method of claim 1, wherein the sinking stage comprises a differential pair of first and second MOSFETs, each MOSFET connected to a burst mode signal source, the first MOSFET connected to a resistor, the resistor connected to a voltage source, the second MOSFET connected to an inductor connected to the anode of the gain-section diode.

4. The method of claim 3, wherein the first MOSFET is turned off and the second MOSFET is turned on to sink the sink current away from the anode of the gain-section diode when the burst mode signal is indicative of the burst-off state.

5. The method of claim 3, wherein the first MOSFET is turned on and the second MOSFET is turned off to cease the sinking of the sink current away from the anode of the gain-section diode when the burst mode signal is indicative of the burst-on state.

6. The method of claim 1, further comprising delivering, by the laser driving circuit, the overshoot current to the anode of the gain-section diode for a transition period of time after commencement of the burst-on state, the transition period of time less than a burst-on period of time corresponding to a duration of the burst-on state.

7. The method of claim 6, wherein the laser driving circuit comprises an accelerating heating stage capacitively coupled to the anode of the gain-section diode to deliver the overshoot current to the anode of the gain-section diode, the heating stage comprising a metal-oxide-semiconductor field-effect transistor (MOSFET) connected to a burst mode signal source and first and second resistors, a ratio of the first and second resistors proportional to a magnitude of the overshoot current.

8. The method of claim 1, further comprising, when the burst mode signal is indicative of the burst-on state, modulating, by the laser driving circuit, the laser by a capacitively coupled modulation stage of the laser driving circuit to the anode of the gain-section diode, resulting in an alternating current (AC) modulation current.

9. The method of claim 8, wherein the modulation stage comprises a differential pair of first and second MOSFETs, each MOSFET connected to a burst mode signal source and a data signal source, the first MOSFET connected to a first resistor, the first resistor connected to a voltage source, the second MOSFET connected by a capacitor to the anode of the gain-section diode.

10. The method of claim 9, wherein the second MOSFET is connected to a second resistor connected to a variable voltage source.

11. The method of claim 1, wherein the tunable laser comprises a multi-section tunable laser.

12. A common-cathode laser driving circuit comprising:

a voltage source configured to deliver a bias current to an anode of a gain-section diode disposed on a shared substrate of a tunable laser;

a sinking stage configured to receive a burst mode signal indicative of a burst-on state or a burst-off state, the sinking stage configured to;

when the burst mode signal is indicative of the burst-off state, sink a sink current away from the bias current at the anode of the gain-section diode, the sink current less than the bias current received by the anode of the gain-section diode; and

when the burst mode signal is indicative of the burst-on state, cease the sinking of the sink current away from the bias current at the anode of the gain-section diode;

an accelerating heating stage configured to deliver an overshoot current to the anode of the gain-section diode to accelerate heating of the gain-section diode when the burst mode signal is indicative of the burst-on state; and

a modulation stage capacitively coupled to the anode of the gain-section diode, the modulation stage configured to output an alternating current (AC) modulation current when the burst mode signal is indicative of the burst-on state.

13. The laser driving circuit of claim 12, wherein when the burst mode signal is indicative of the burst-off state, the gain-section diode receives a diode current equal to the bias current minus the sink current.

14. The laser driving circuit of claim 12, wherein the sinking stage comprises a differential pair of first and second MOSFETs, each MOSFET connected to a burst mode signal source, the first MOSFET connected to a resistor, the resistor connected to a voltage source, the second MOSFET connected to an inductor connected to the anode of the gain-section diode.

15. The laser driving circuit of claim 14, wherein the first MOSFET is turned off and the second MOSFET is turned on to sink the sink current away from the anode of the gain-section diode when the burst mode signal is indicative of the burst-off state.

16. The laser driving circuit of claim 14, wherein the first MOSFET is turned on and the second MOSFET is turned off to cease the sinking of the sink current away from the anode of the gain-section diode when the burst mode signal is indicative of the burst-on state.

17. The laser driving circuit of claim 12, wherein the heating stage delivers the overshoot current to the anode of the gain-section diode for a transition period of time after commencement of the burst-on state, the transition period of time less than a burst-on period of time corresponding to a duration of the burst-on state.

18. The laser driving circuit of claim 12, wherein the heating stage is capacitively coupled to the anode of the gain-section diode to deliver the overshoot current to the anode of the gain-section diode, the heating stage comprising a metal-oxide-semiconductor field-effect transistor (MOSFET) connected to a burst mode signal source and first and second resistors, a ratio of the first and second resistors proportional to a magnitude of the overshoot current.

19. The laser driving circuit of claim 12, wherein the modulation stage comprises a differential pair of first and second MOSFETs, each MOSFET connected to a burst mode signal source and a data signal source, the first MOSFET connected to a first resistor, the first resistor connected to a voltage source, the second MOSFET connected by a capacitor to the anode of the gain-section diode.

20. The laser driving circuit of claim 19, wherein the second MOSFET is connected to a second resistor connected to a variable voltage source.

21. The laser driving circuit of claim 12, wherein the tunable laser comprises a multi-section tunable laser.