Wavelength stabilized laser light source

Details Wavelength stabilized laser light source Wavelength stabilized laser light source

1999-07-30

2001-06-12

Ullah, Akm E. (Department: 2874)

Optical waveguides

With optical coupler

Input/output coupler

Reexamination Certificate

active

06246816

ABSTRACT:

BACKGROUND OF THE INVENTION
Many sensors and communications devices require a laser light source with a stable wavelength over time and over a broad temperature and drive current range. Fiber optic sensors, for example, use a broad band optic fiber light source, which requires a laser diode to pump the optic fiber light source and generate amplified stimulated emission (ASE). A sensor such as a fiber optic gyroscope requires a centroid (or average) wavelength of the ASE to be stable in order for the scale factor to be stable. When the conditions of drive current and temperature for the pump laser diode change, the peak wavelength of the laser diode light output also changes. This, in turn, causes the centroid wavelength of the ASE of the lasing optic fiber to change. While it is possible to model a large part of the changes in the centroid wavelength of the ASE as a function of the drive conditions for the laser diode, not all variations can be accurately modeled. In order to achieve a high accuracy fiber optic sensor, it is preferred to reduce the amount of the change in the wavelength to be modeled. The peak wavelength of the pump laser diode also can change with age. Individual pump laser diodes are affected by age to different degrees. Age is very difficult to correct with modeling so that it is difficult to produce a high accuracy fiber optic sensor that maintains its accuracy over time.
SUMMARY OF THE INVENTION
The present invention comprises a wavelength stabilized laser light source having a lasing element for generating substantially polarized light, a polarization maintaining optic fiber segment coupled to the lasing element for conducting the light generated by the lasing element and a wavelength selective reflector coupled to the polarization maintaining optic fiber segment. The wavelength selective reflector reflects a portion of the light generated by the lasing element back to the lasing element. Another fiber optic segment coupled to the wavelength selective reflector conducts a second portion of the light away from the lasing element. The lasing element is preferably a laser diode and the wavelength selective reflector is preferably a Bragg grating that reflects from 5% to 40% of the light received from the first fiber optic segment. This combination results in a light source that produces a stable wavelength of laser light over a broad temperature range and over a broad range of drive currents. It is also stable over time as the lasing element ages. The wavelength stabilized laser light source can be augmented with a fluorescing optic fiber to produce a stabilized broad band light source. The present invention can be used for fiber optic sensors, in amplifiers, to supply a communications signal or for a number of other purposes.


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