Multi-wavelength laser usable for WDM applications and interferometric sensors

• US 6,389,044 B1
• Filed: 05/31/2000
• Issued: 05/14/2002
• Est. Priority Date: 07/02/1999
• Status: Expired due to Fees

• Current Assignee: Corning Incorporated
• Original Assignee: Corning Incorporated
• Inventors: Smith, James A.
• Primary Examiner(s): Ip, Paul
• Assistant Examiner(s): ZAHN, JEFFREY N
• Application Number:
  US09/583,242
• Time in Patent Office: 713 Days
• Field of Search: 372/23, 372/97, 372/6, 372/20
• US Class Current: 372/23
• CPC Class Codes: H04B 10/506 Multiwavelength transmitters
• CPC Class Codes: H04B 10/572 Wavelength control

Abstract

A multi-wavelength laser (10) includes an optical loop (20) having a single optical cavity that supports a plurality of longitudinal modes, wherein the optical loop has a common gain medium (25) to supply the necessary optical gain to provide for a plurality of lasing longitudinal modes at a plurality of lasing wavelengths. A wavelength selector (30) is insertable into the optical loop within the optical path for selecting at least one lasing longitudinal mode (35) from the plurality of longitudinal modes. Although not exclusively, the multi-wavelength laser (10) is usable for WDM interferometric sensing (240).

Claims

1. A method for laser synthesizing a plurality of different wavelengths, the method comprising the steps of:

providing a laser having a common gain medium in a resonant path for receiving and exiting a pump energy and having a continuity between a plurality of reflectors having a common reflector for supporting a plurality of optical wavelengths pumped by the pump energy that share the common reflector

selecting at least one optical wavelength from the plurality of optical wavelengths between one of the plurality of reflectors and the common reflector; and

referencing said at least one optical wavelength to an internal or external reference source.

2. A method of claim 1 wherein the step of referencing includes optical interferometric sensing for the measurement of dynamic displacements.

3. A multi-wavelength laser comprising:

a resonant path that receives and exits a pump energy and having a continuity between a plurality of reflectors for resonating a plurality of longitudinal modes for multiple lasing oscillations, wherein the resonant path has a common reflector out of the plurality of reflectors and a common gain medium to supply the necessary optical gain and pump energy to provide for a plurality of lasing longitudinal modes at a plurality of lasing wavelengths that share the common reflector; and

a wavelength selector that is insertable into the resonant path between one of the plurality of reflectors and the common reflector for selecting at least one lasing longitudinal mode from the plurality of longitudinal modes.

4. The multi-wavelength laser of claim 3 wherein the resonant path comprises a Fabry-Perot laser cavity having an erbium doped fiber as the common gain medium for supporting broadband wavelength amplification of the plurality of lasing wavelengths between the plurality of reflectors, comprising at least one of the group comprising a grating and a mirror.

5. The multi-wavelength laser of claim 3 wherein the resonant path comprises a ring laser cavity having an erbium doped fiber as the common gain medium between the plurality of reflectors formed by an optical continuity requirement of optical electromagnetic fields within the ring laser cavity.

6. The multi-wavelength laser of claim 3, wherein the wavelength selector comprises a WDM to select at least one desired lasing wavelength from the plurality of lasing longitudinal modes.

7. The multi-wavelength laser of claim 6, wherein the wavelength selector further comprises a VOA to control the amplitude of at least one desired lasing wavelength from the plurality of lasing longitudinal modes.

8. The multi-wavelength laser of claim 3, wherein the wavelength selector comprises an LCX to control the desired lasing wavelengths and amplitudes from the plurality of longitudinal modes.

9. A multi-wavelength laser comprising:

a resonant path bounded by a plurality of reflectors that supports a plurality of longitudinal modes for multiple lasing oscillations, wherein the resonant path has a common reflector out of the plurality of reflectors and a common gain spectrum to supply the necessary optical gain to provide for a plurality of lasing longitudinal modes at a plurality of lasing wavelengths that share the common reflector;

a combiner having an output port, a first input port and a second input port, wherein the first input port receives a pump energy, the output port is coupled to the common reflector for forming a first end of the common gain medium of the resonant path, and the second input port is coupled into another portion of the resonant path for the combiner to combine the pump energy with the plurality of lasing longitudinal modes and each mode being capable of lasing at a respective lasing wavelength when pumped by the pump energy, whereby lasing light is emittable from respective each one of the lasing longitudinal modes;

a wavelength selector that is insertable into the resonant path between one of the plurality of reflectors and the common reflector for selecting at least one lasing longitudinal mode from the plurality of longitudinal modes; and

a wavelength separator coupled to another one of the plurality of reflectors to form a second end of the common gain medium for providing a first port outside of the resonant path and a second port for the plurality of longitudinal modes to loop back into the resonant path.

10. The multi-wavelength laser of claim 9, wherein the combiner comprises a first wavelength division multiplexor (WDM).

11. The multi-wavelength laser of claim 10, wherein the resonant path comprises a Fabry-Perot laser cavity having a plurality of sub-cavities, apportioned upon the common gain spectrum by the wavelength selector, between the common reflector comprising a mirror and the plurality of reflectors comprising reflective Bragg gratings.

12. The multi-wavelength laser of claim 11, wherein the wavelength selector comprises.

a second WDM for apportioning the gain spectrum of the common gain spectrum into the plurality of sub-cavities;

a plurality of Variable Optical Attenuators (VOAs) each disposed in at least one of the plurality of sub-cavities for providing amplitude control for the respective lasing wavelengths;

the plurality of reflective Bragg gratings disposed at the end of each of the plurality of sub-cavities for determining the laser linewidth and center wavelength of the respective lasing wavelengths; and

a plurality of Thermoelectric Controllers (TECs) for adjusting the temperature of the plurality of reflective Bragg gratings for changing the optical path length of each of the sub-cavities for determining the center wavelength of the respective lasing wavelength.

13. The multi-wavelength laser of claim 12 further comprising a heterodyne interferometer for actively tuning the respective laser wavelengths based on the feedback received from monitoring the leakage light transmitted through each of the plurality of reflective Bragg gratings.

14. The multi-wavelength laser of claim 13 wherein the heterodyne interferometer comprises:

a reference laser emitting at a specified wavelength λ

₀ for precisely determining the center wavelength of the first sub-cavity at λ

₁;

a mixing coupler for mixing light from the reference laser and the first sub-cavity for providing a mixed light output;

a photodiode monitors the intensity fluctuations of the mixed light output from the mixing coupler;

a demodulation controller for amplitude modulating the intensity fluctuations of the mixed light output for providing a frequency difference between λ

₀ and λ

₁ and stabilizing the frequency difference at a predetermined constant by adjusting the temperature of the respective TEC associated with the respective reflective Bragg grating for tuning the center wavelength of the first sub-cavity at λ

₁; and

a plurality of cascading couplers and a plurality of duplicated sets comprising the photodiode and the demodulation controller for tuning the center wavelength of a sub-cavity with reference to a previous tuned sub-cavity.

15. The multi-wavelength laser of claim 11, wherein the resonant path further comprising an output coupler having a first input port, a first output port and a second output port, the first output port providing an exit path for the multi-wavelength laser output having the plurality of lasing wavelengths and the second output port coupling back to the first input port providing a loop back into the resonant path.

16. The multi-wavelength laser of claim 12, wherein the wavelength separator comprises a third WDM having the first port terminated for proving an exit path for the pump energy and the second port coupled to the mirror for the plurality of longitudinal modes to loop back into the Fabry-Perot laser cavity.

17. The multi-wavelength laser of claim 9, wherein the wavelength separator comprises an output coupler having a coupling port, the first port outside of the resonant path, and the second port, wherein the first port disposed outside of the resonant path provides an exit path for the multi-wavelength laser output having the plurality of lasing wavelengths and the second port coupling back to the coupling port provides for the plurality of longitudinal modes to loop back into the resonant path.

18. The multi-wavelength laser of claim 17, wherein the wavelength selector comprises an LCX coupled to the coupling port of the output coupler to control the plurality of lasing wavelengths and amplitudes of the multi-wavelength laser output.

19. The multi-wavelength laser of claim 10, wherein the resonant path comprises a Fabry-Perot laser cavity having a plurality of sub-cavities, apportioned upon the common gain spectrum by the wavelength selector, between the common reflector comprising a first mirror and another one of the plurality of reflectors comprising a second mirror.

20. The multi-wavelength laser of claim 19, wherein the wavelength selector comprises:

an output coupler having a coupling port, the first port outside of the resonant path, and the second port, wherein the first port disposed outside of the resonant path provides an exit path for the multi-wavelength laser output having the plurality of lasing wavelengths and the second port coupling back to the coupling port provides for the plurality of longitudinal modes to loop back into the Fabry-Perot laser cavity; and

an LCX coupled to the coupling port of the output coupler to control the plurality of lasing wavelengths and amplitudes of the multi-wavelength laser output.