Optical waveguides – Optical waveguide sensor
Reexamination Certificate
2002-12-06
2004-09-14
Palmer, Phan T. H. (Department: 2874)
Optical waveguides
Optical waveguide sensor
C385S094000, C385S128000
Reexamination Certificate
active
06792169
ABSTRACT:
FIELD OF THE INVENTION
The present invention relates generally to sensors based on optical fibers, and more particularly to active and passive sensors utilizing chiral fiber elements.
BACKGROUND OF THE INVENTION
In recent years, passive sensors based on fiber optic elements have found increased use in various industrial and commercial applications. Fiber optic sensors typically utilize a fiber Bragg grating element having predefined stop band gap (reflection band) characteristics centered around a pre-defined wavelength range. A broadband emission source or a continuously tunable laser emit radiation toward the fiber Bragg grating element over a broad range of wavelengths, while a photodetector detects wavelengths reflected by the reflection band. Changes in pressure or temperature (depending on the sensor configuration) cause the reflection band to shift. Thus, because the photodetector monitors the shifts in the wavelengths reflected or transmitted through the fiber Bragg grating, the fiber optic sensor, depending on its configuration, can detect changes in pressure or temperature.
The above description refers to previously known passive sensors. Attempts have been made to design an active sensor based on a fiber Bragg grating. An active sensor requires optically pumping a fiber Bragg grating doped with optically excitable material to produce lasing at a predefined wavelength and then detecting shifts in the wavelength due to temperature or pressure. The advantage of an active sensor is that a broadband (or a continuously tunable) emission source is not required. However, due to the nature of previously known fiber Bragg gratings, a fiber Bragg grating would need to be of significant length (e.g. at least approximately 15 meters) in order to produce lasing, making an active sensor impractical.
Finally, both types of previously known fiber optic sensors suffer from a number of drawbacks. Fiber Bragg gratings are typically manufactured through irradiating, with UV light, an optical fiber made from a UV-sensitive material through a pre-designed phase mask. Another prior-art approach to manufacturing fiber Bragg gratings involves irradiating a UV-sensitive optical fiber with two interfering UV laser beams. In both approaches, the resulting fiber Bragg gratings have two significant disadvantages. First, the requirement that the optical fiber be UV-sensitive limits the application of the prior art sensors in that the sensors cannot be used in an environment in which exposure to UV radiation may occur. Second, the UV-sensitive fiber requirement limits the choice of materials used in fabricating the fiber Bragg gratings. In addition, while previously known fiber Bragg gratings are sensitive to shifts in temperature and pressure, they are not sensitive to axial twisting. Finally, the previously known fiber Bragg gratings are relatively expensive and difficult to manufacture.
It would thus be desirable to provide an optical fiber based sensor that can be used in locations exposed to UV radiation. It would further be desirable to provide an optical fiber based sensor that can be fabricated from any material suitable for optical fibers. It would additionally be desirable to provide an optical fiber based sensor that is responsive to axial twisting. It would also be desirable to provide an active optical fiber based sensor that is small and practical to use. It would further be desirable to provide an optical fiber bases sensor that is easy and inexpensive to manufacture.
REFERENCES:
patent: 3976356 (1976-08-01), Jenkins
patent: 4099835 (1978-07-01), French et al.
patent: 4227771 (1980-10-01), Nolan
patent: 4468091 (1984-08-01), Schmadel et al.
patent: 4949038 (1990-08-01), Birch et al.
patent: 5452394 (1995-09-01), Huang
Genack Azriel Zelig
Kopp Victor Il'ich
Chiral Photonics, Inc.
Doan Jennifer
Etkin, Esq. Edward
Palmer Phan T. H.
LandOfFree
Chiral fiber sensor apparatus and method does not yet have a rating. At this time, there are no reviews or comments for this patent.
If you have personal experience with Chiral fiber sensor apparatus and method, we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Chiral fiber sensor apparatus and method will most certainly appreciate the feedback.
Profile ID: LFUS-PAI-O-3192288