Active bidirectional mode-locked lasers and applications to accurate measurements in navigation systems
In various embodiments, systems and methods can be structured to provide efficient active bidirectional mode-locked lasers, which can be used as intracavity phase interferometer (IPI) sensors. Stable bidirectional mode-locking can be achieved by a combination of a passive mechanism, a passively driven active mechanism, and a beat note detection system. Such systems can be used in guidance, navigation, and control systems, where attitude control of a vehicle relies on accurate measurements of its position and motion. In various embodiments, a detection system can be based on an all fiber intracavity phase interferometer (IPI) active laser capable of delivering accurate simultaneous measurements of all three degrees of rotation and position in a single, compact, cost effective unit. A variation of the same system can include a linear cavity laser for accurate measurements of acceleration without the use of any inertial masses. Additional apparatus, systems, and methods are disclosed.
1. A method comprising:
operating a mode-locked laser arranged as an intracavity phase interferometer to simultaneously measure rotation and position relative to a reference magnetic field, the mode-locked laser including a laser, a modulation controller coupled to the laser, the modulation controller arranged to modulate loss in the laser, and a detection unit coupled to the laser, the detection unit structured to detect differences in counter-propagating optical signals in the laser and to provide a control signal to the modulation controller.
2. The method of claim 1 , wherein the method includes making attitude measurements for a vehicle.
3. The method of claim 1 , wherein the method includes measuring acceleration by operating a linear laser, arranged as the laser in the mode-locked laser, without use of an inertial mass.
4. The method of claim 1 , wherein the method includes operating the mode-locked laser using a magnetic detection unit by applying a control signal to a Pockels cell arranged in the magnetic detection unit in-line with a fiber loop of the mode-locked laser.
5. A system comprising:
a laser;
a modulation controller coupled to the laser, the modulation controller arranged to modulate loss in the laser; and
a detection unit coupled to the laser, the detection unit structured to detect differences in counter-propagating optical signals in the laser and to provide a control signal to the modulation controller.
6. The system of claim 5 , wherein the modulation controller is arranged to modulate loss in the laser based on an oscillation rate of the laser.
7. The system of claim 5 , wherein the modulation controller includes a pair of modulators structured to be biased for no transmission in an absence of a controlling pulse.
8. The system of claim 5 , wherein the laser includes a fiber ring laser.
9. The system of claim 8 , wherein the system includes a magnetic detector disposed in-line with fiber of the fiber ring laser.
10. The system of claim 8 , wherein the magnetic detector includes a Pockels cell.
11. The system of claim 8 , wherein the fiber ring laser includes an erbium-doped fiber to provide a gain medium.
12. The system of claim 8 , wherein the fiber ring laser, the modulation controller, and the detection unit are arranged as an intracavity phase interferometer.
13. The system of claim 12 , wherein the fiber ring laser, the modulation controller, and the detection unit are arranged to simultaneously measure rotation and position relative to a reference magnetic field.
14. The system of claim 12 , wherein the fiber ring laser, the modulation controller, and the detection unit are arranged in a navigation system of a vehicle.
15. The system of claim 12 , wherein the fiber ring laser includes a fiber loop encircled around an area inside the vehicle.
16. The system of claim 5 , wherein the laser includes a linear laser.
17. The system of claim 16 , wherein the system includes an accelerometer constructed from the linear laser without use of an inertial mass.
18. The system of claim 5 , wherein the modulation controller includes an electronic feedback including a piezoelectric actuator coupled to a beat note detector.
19. The system of claim 5 , wherein the modulation controller includes an electronic feedback including drivers to control a pair of amplitude modulators coupled to a fiber loop of the laser.