Couplers for optical fibers

Details Couplers for optical fibers Couplers for optical fibers

1999-03-12

2001-01-16

Gorgos, Kathryn (Department: 1741)

Electrolysis: processes, compositions used therein, and methods

Electroforming or composition therefor

Roll, ring, or hollow body

C205S079000

Reexamination Certificate

active

06174424

ABSTRACT:

TABLE OF CONTENTS
STATEMENT REGARDING RELATED APPLICATIONS . . .
TECHNICAL FIELD . . .
BACKGROUND OF THE INVENTION . . .
LIGHT SCATTERING SPECTROSCOPY . . .
FLAT FACE, PARALLEL FIBER PROBES . . .
ATTEMPTS TO IMPROVE PROBE PERFORMANCE . . .
SUMMARY OF THE INVENTION . . .
BRIEF DESCRIPTION OF THE DRAWINGS . . .
DETAILED DESCRIPTION . . .
OPTICAL FIBERS IN GENERAL . . .
AN IMPROVED PROBE ASSEMBLY . . .
METHODS OF MANIPULATING LIGHT WITHIN A FIBER . . .
IMPROVED PROBE ASSEMBLY UTILIZING INTERNALLY REFLECTIVE SURFACES . . .
OPERATION OF AN EXEMPLARY PROBE ASSEMBLY . . .
PERFORMANCE OF AN EXEMPLARY PROBE ASSEMBLY . . .
COMPLEX SURFACES . . .
ADDITIONAL ASPECTS OF THE PROBE ASSEMBLY FILTERING MECHANISMS . . .
ADDITIONAL ASPECTS OF THE PROBE ASSEMBLY INSTRUMENT INTERFACE . . .
ALTERNATIVE EMBODIMENTS FIBER GEOMETRY . . .
SEPARATE ELEMENTS . . .
RELATED EMBODIMENT ALSO UTILIZING INTERNALLY REFLECTIVE SURFACES . . .
GRADIENT REFRACTIVE INDEX EMBODIMENT . . .
REFRACTIVE END PIECES APPLIED TO THE PROBE TIP . . .
PROBES EMPLOYING LIGHT MANIPULATION BETWEEN ADJOINING FIBER SEGMENTS . . .
SEPARATE METHODOLOGY . . .
A SINGLE FIBER EMBODIMENT . . .
DELIVERING AND COLLECTING LIGHT ALONG A COMMON AXIS . . .
DELIVERING AND COLLECTING LIGHT THROUGH A COMMON APERTURE . . .
FIBER OPTIC LIGHT MANIPULATION APPARATUS YIELDING SIDE VIEWING AND SIDE DELIVERY . . .
IMPROVED FILTERING TECHNIQUES FOR OPTICAL FIBERS . . .
THE FILTER APPLICATION PROCESS . . .
TOOLING . . .
FILTER DESIGN . . .
FIBER COUPLING . . .
SPECIAL CASES . . .
IMPROVED COLLECTION AND FILTERING OPTICS FOR CONFOCAL PROBES . . .
IMPROVED FILTERING . . .
AMPLIFIED RESPONSE . . .
SUMMARY OF THE DETAILED DESCRIPTION . . .
CLAIMS . . .
TECHNICAL FIELD
This invention relates generally to optical fibers, and more particularly to optical fiber probes that use manipulated delivery and reception regions to improve sensitivity to specific light-matter interactions.
BACKGROUND OF THE INVENTION
In recent years, the use of optical fibers has become increasingly widespread in a variety of applications. Optical fiber probes have been found to be especially useful for analyzing materials by employing various types of light-scattering spectroscopy.
Optical fibers offer numerous advantages over other types of source/detection equipment. In short, the fiber provides a light conduit so that the source-generating hardware and the recording apparatus are stationed independently of the subject under investigation and the point of analysis. Thus, analyses are conducted remotely in otherwise inaccessible locations. Previously unattainable information is acquired in situ, often in real time. This capability is sought in numerous industrial, environmental, and biomedical applications. The laboratory is moved on line in the industrial realm, to the field in the environmental sector, and in vivo in the biotechnical arena. Additionally, hardware and measurements are more robust, quicker, less intrusive, more rugged, less costly, and many other advantages are realized.
LIGHT SCATTERING SPECTROSCOPY
While transmission spectroscopy analyzes light passing through a substance, light-scattering spectroscopy entails illumination of a measure and and analyzing light that is scattered at angles relative to the incident source. The photon-matter interactions of the scattering events may be either elastic or inelastic. In an inelastic event, a photon's energy (wavelength) changes as a result of the light-matter interaction. In an elastic event, a photon's energy (wavelength) does not change. Absorption, the phenomena in which a fraction of photons are entirely absorbed, also plays a role in light-scattering spectroscopies. Raman, diffuse, reflectance, and fluorescence spectroscopies are of particular interest as they relate to vibrational and nonvibrational photogenic responses of a material.
The Raman effect describes a subtle light-matter interaction. Minute fractions of light illuminating a substance are Raman-scattered in random directions. Raman-scattered light is color shifted from the incident beam (usually a laser). The color (frequency) shifts are highly specific as they relate to molecular bond vibrations inducing molecular polarizability changes. Raman spectroscopy is a powerful technique for chemical analysis and monitoring. The resulting low light levels require sophisticated, expensive instrumentation and technical complexity. Suitable technology and products for on-line analysis of processes and environmental contaminants are just becoming available.
Specular reflectance relates to a surface's mirror-like aspects. Diffuse reflectance relates to light that is elastically scattered from a surface of material at diffuse angles relative to the incident team. For example, a projector screen diffusely reflects light while a glossy, new waxed car has a high specular component. Diffuse reflectance spectroscopy is important for chemical analysis as well as measuring visual perception. Among other things, it is based on particulate-scattering and absorption events.
Fluorescence relates to substances which absorb light at one wavelength then re-emit it at a longer wavelength as a result of electronic transitions. As an example, a “highlighter” felt-tip marker appears to “glow” green as it absorbs blue and ultraviolet light then emits it as green. Fluorescence provides a powerful technique for chemical monitoring.
Raman spectroscopy is a well-established laboratory technique and is generally recognized as having enormous potential for on-line monitoring and sensing. With the advent of stable lasers, cheap computing power, efficient detectors, and other new technological advancements, Raman spectroscopy is primed for widespread industrial monitoring deployment. In addition to process control monitoring, it will be utilized in specialized monitoring and sensing devices ranging from neuroimaging to environmental monitoring, to in vitro and in vivo medical testing.
Raman spectroscopy involves energizing a sample with a high-power, narrow-wavelength energy source, such as a laser. The laser photons induce low intensity light emissions as wavelengths shift from the laser's. The Raman effect is an elastic scattering of photons The emitted Raman light is collected and analyzed with a specialized instrument.
The spectral positions (colors) of the shifts provide fingerprints of the chemicals in the sample. Thus, Raman spectroscopy provides a means for chemical identification. The intensity of the shift (the spectral peak height) correlates to chemical concentration. Thus, a properly calibrated instrument provides chemical content and concentration. In practicality, Raman spectroscopy is technically complex and requires sophisticated, expensive instrumentation.
Raman spectroscopy is well suited to aqueous-based media without sample preparation. From this standpoint, it is an ideal tool for process control medical testing and environmental applications. Thus, Raman spectroscopy has great potential for real-time monitoring and is being vigorously pursued.
The basic concept for a probe-based, on-line Raman instrument is simple. Laser light is directed down an optical fiber to a remote probe. The laser light exits the fiber and illuminates the sample medium. Another fiber picks up the Raman-emitted light and returns it to the instrument for analysis.
In practicality, the engineering challenges for a robust physical probe implementation are substantial. In addition to the optical performance expected by laboratory instruments, a probe must be hardened to withstand extreme physical and chemical conditions. Optical characteristics must also remain constant as dynamic conditions change.
Optical aspects of probe engineering require particular design finesse. The Raman effect involves very weak signals. Raman emissions may be one trillionth as intense as the exciting radiation. Subsequently, the probe must be incredibly efficient in collecting and transmitting Raman-emitted light. And, the signal must not be corrupted by extraneous influences. As an example of the sensitivity,

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