Compact wavelength-independent wavelength-locker for absolute wavelength stability of a laser diode

• US 6,385,217 B1
• Filed: 02/16/1999
• Issued: 05/07/2002
• Est. Priority Date: 02/16/1999
• Status: Expired due to Term

• Current Assignee: RPX Clearinghouse LLC (RPX Corporation)
• Original Assignee: Qtera Corporation (Nortel Networks Corporation)
• Inventors: Diner, Fahri, Singh, Harmeet
• Primary Examiner(s): Ip, Paul
• Assistant Examiner(s): Ruiz, Delma R. Flores
• Application Number:
  US09/250,879
• Time in Patent Office: 1,176 Days
• Field of Search: 372/20, 372/96
• US Class Current: 372/20
• CPC Class Codes: H01S 5/0687 Stabilising the frequency of the laser

Abstract

A wavelength independent wave-locker arrangement is used to control the output wavelength of a laser diode. In the wave-locker arrangement, a narrow-band power splitter is responsive to the reception of a portion of an optical output signal from the laser diode for splitting the received optical signal into first and second coupler optical output signals, respectively. First and second photodetectors are coupled to receive the first and second coupler optical output signals, respectively, and generate respective corresponding first and second electrical output signals. A control unit is responsive to the reception of the first and second electrical output signals from the first and second photodetectors for generating predetermined control signals to the laser diode for maintaining the wavelength of the laser diode at a predetermined constant value.

Claims

1. An improved wavelength-independent wave-locker arrangement for controlling the output wavelength of a laser diode based upon a portion of an optical output signal from the laser diode, the improvement comprising:

a narrow-band power splitter responsive to the reception of the portion of the optical output signal from the laser diode for splitting the received optical signal into first and second split optical output signals, respectively;

first and second photodetectors responsive to the reception of the first and second split optical output signals, respectively, for generating respective corresponding first and second electrical output signals; and

a control unit responsive to the reception of the first and second electrical output signals from the first and second photodetectors, respectively, for generating control signals for the laser diode for maintaining the wavelength of the laser diode at a predetermined value.

2. The improved wave-locker arrangement of claim 1 wherein the narrow-band power splitter is formed from first and second optical fibers.

3. The improved wave-locker arrangement of claim 1 wherein the narrow-band power splitter is formed from first and second planar waveguides.

4. The improved wave-locker arrangement of claim 3 wherein the first and second planar waveguides comprise passive waveguides for making the narrow-band power splitter tunable.

5. The improved wave-locker arrangement of claim 3 wherein the first and second planar waveguides comprise active waveguides for making the narrow-band power splitter tunable.

6. The improved wave-locker arrangement of claim 1 wherein the narrow-band power splitter is a Mach-Zehnder interferometer comprising:

a first fused tapered optical coupler including first and second input couplings and first and second output couplings, the first fused tapered optical coupler being coupled to receive the portion of the optical output signal from the laser diode at the first input coupling, and to provide first and second coupler optical signals to the first and second output couplings, respectively; and

a second fused tapered optical coupler including third and fourth input couplings and third and fourth output couplings, the second fused tapered optical coupler being coupled to receive the first and second coupler optical signals from the first and second output couplings of the first fused tapered optical coupler at the third and fourth input couplings, respectively, and provide third and fourth coupler optical signals having complementary waveforms at the third and fourth output couplings, respectively.

7. The improved wave-locker arrangement of claim 1 wherein the narrow-band power splitter comprises a fused tapered coupler having first and second optical waveguides that are fused together and stretched to provide a predetermined length and shape, the first and second optical waveguides having first and second output paths, respectively, the first optical waveguide being coupled to receive the portion of the optical output signal from the laser diode and to provide first and second coupler optical output signals at the first and second output paths, respectively, which have waveforms that are complementary to each other.

8. The improved wave-locker arrangement of claim 1 further comprising:

an optical power tap coupled between an output of the laser diode and an input of the narrow-band power splitter, the optical power tap being responsive to an optical output signal from the laser diode for splitting the optical output signal from the laser diode into first and second portions, wherein the first portion is provided as an optical output signal from the improved wave-locker arrangement, and wherein the second portion is provided to the input of the narrow-band power splitter as the portion of the optical output signal from the laser diode.

9. The improved wave-locker arrangement of claim 1 wherein the control unit is responsive to the first and second electrical output signals from the first and second photodetectors for dynamically maintaining only the wavelength of the laser diode at a constant value.

10. The improved wave-locker arrangement of claim 1 wherein the control unit is responsive to the first and second electrical output signals from the first and second photodetectors for dynamically controlling both the wavelength and the power of the laser diode so that the wavelength of the laser diode is maintained at a constant value.

26. The improved wave-locker arrangement of claim 1 wherein the first and second photodetectors are directly coupled to the first and second split optical output signals, respectively, provided by the narrow-band power splitter.

27. The improved wave-locker arrangement of claim 1 wherein the narrow-band power splitter is an interferometer that is configured to generate the first and second split optical output signals so that the first and second split optical output signals have complementary shapes.

11. An improved wavelength-independent wave-locker arrangement for controlling the output wavelength of a laser diode, the improvement comprising:

an optical power tap responsive to an optical output signal from the laser diode for splitting the optical output signal into first and second output optical signal portions, wherein the first output optical signal portion is provided as an optical output signal from the improved wave-locker arrangement;

a narrow-band power splitter responsive to the reception of the second output optical signal portion from the optical power tap for splitting the second output optical signal portion into first and second split optical output signals;

first and second photodetectors responsive to the direct reception of the first and second split optical output signals, respectively, for generating respective corresponding first and second electrical output signals; and

a control unit responsive to the reception of the first and second electrical output signals from the first and second photodetectors, respectively, for generating control signals for the laser diode for maintaining the wavelength of the laser diode at a predetermined constant value.

12. The improved wave-locker arrangement of claim 11 wherein the narrow-band power splitter is formed from first and second optical fibers.

13. The improved wave-locker arrangement of claim 11 wherein the narrow-band power splitter is formed from first and second planar waveguides.

14. The improved wave-locker arrangement of claim 13 wherein the first and second planar waveguides comprise passive waveguides for making the narrow-band power splitter tunable.

15. The improved wave-locker arrangement of claim 13 wherein the first and second planar waveguides comprise active waveguides for making the narrow-band power splitter tunable.

16. The improved wave-locker arrangement of claim 11 wherein the narrow-band power splitter is a Mach-Zehnder interferometer comprising:

a first fused tapered optical coupler including first and second input couplings and first and second output couplings, the first fused tapered optical coupler being coupled to receive the second output optical signal portion from the optical power tap at the first input coupling, and to provide first and second coupler optical signals to the first and second output couplings, respectively; and

a second fused tapered optical coupler including third and fourth input couplings and third and fourth output couplings, the second fused tapered optical coupler being coupled to receive the first and second coupler optical signals from the first and second output couplings of the first fused tapered optical coupler at the third and fourth input couplings, respectively, and provide third and fourth coupler optical signals having complementary waveforms at the third and fourth output couplings, respectively.

17. The improved wave-locker arrangement of claim 11 wherein the narrow-band power splitter comprises a fused tapered coupler having first and second optical waveguides that are fused together and stretched to provide a predetermined length and shape, the first and second optical waveguides having first and second output paths, respectively, the first optical waveguide being coupled to receive the second output optical signal portion from the optical power tap and to provide first and second coupler optical output signals at the first and second output paths, respectively, which have waveforms that are complementary to each other.

18. The improved wave-locker arrangement of claim 11 wherein the control unit is responsive to the first and second electrical output signals from the first and second photodetectors for dynamically maintaining only the wavelength of the laser diode at a constant value.

19. The improved wave-locker arrangement of claim 11 wherein the control unit is responsive to the first and second electrical output signals from the first and second photodetectors for dynamically controlling both the wavelength and the power of the laser diode so that the wavelength of the laser diode is maintained at a constant value.

28. The improved wave-locker arrangement of claim 11, wherein the narrow-band power splitter is an interferometer that is configured to generate the first and second split optical output signals so that the first and second split optical output signals have complementary shapes.

20. An improved method of controlling the output wavelength of a laser diode in a wavelength-independent wave-locker arrangement comprising the steps of:

(a) splitting a portion of an optical signal from the laser diode received at an input of a narrow-band power splitter into first and second split optical output signals;

(b) receiving the first and second split optical output signals from step (a) directly in first and second photodetectors, respectively, and generating therefrom respective first and second electrical output signals in the first and second photodetectors, respectively; and

(c) generating control signals in a control unit for transmission to the laser diode in response to the reception by the control unit of the first and second electrical output signals from the first and second photodetectors, respectively, generated in step (b) for maintaining the wavelength of the laser diode at a predetermined value.

21. The improved method of claim 20 wherein in performing step (a), the narrow-band power splitter is a Mach-Zehnder interferometer and step (a) comprises the substeps of:

(a1) receiving the portion of the optical signal from the laser diode at a first input coupling of a first fused tapered coupler and for splitting the received portion of the optical signal from the laser diode into first and second coupler optical signals that are provided at first and second output couplings, respectively, of the first fused tapered coupler; and

(a2) receiving the first and second coupler optical signals from the first and second output couplings, respectively, of the first fused tapered coupler generated in step (a1) at respective third and fourth input couplings of a second fused tapered coupler, and generating third and fourth coupler optical signals having complementary waveforms at third and fourth output couplings, respectively, of the second fused tapered coupler.

22. The improved method of claim 20 wherein in performing step (a), the narrow-band power splitter comprises a fused tapered coupler having first and second optical waveguides that are fused together and stretched to provide a predetermined length and shape, the first and second optical waveguides having first and second input ports and output parts, respectively, and step (a) comprises the substeps of:

(a1) receiving the portion of the optical signal from the laser diode at a first input port of the first optical waveguide; and

(a2) generating first and second coupler optical output signals having waveforms that are complementary to each other in the first and second optical waveguides at the first and second output ports, respectively.

23. The improved method of claim 20 wherein prior to performing step (a), performing the step of:

(d) receiving an optical output signal from the laser diode in an optical power tap and splitting the optical output signal from the laser diode into first and second portions;

(e) transmitting the first portion from step (d) as an optical output signal from the wave-locker arrangement; and

(f) concurrently transmitting the second portion from step (d) to the input of the narrow-band power splitter.

24. The improved method of claim 20 wherein in performing step (c), generating control signals in the control unit for transmission to the laser diode for dynamically controlling only the wavelength of the laser diode so that the wavelength is maintained at a constant value.

25. The improved method of claim 20 wherein in performing step (c), generating control signals in the control unit for dynamically controlling both the wavelength and the power of the laser diode so that the wavelength of the laser diode is maintained at a constant value.

29. The improved method of claim 20 wherein the narrow-band power splitter is an interferometer that is configured to generate the first and second split optical output signals so that the first and second split optical output signals have complementary shapes.