Optical waveguides – With optical coupler – Input/output coupler
Reexamination Certificate
2001-03-13
2003-03-11
Healy, Brian (Department: 2874)
Optical waveguides
With optical coupler
Input/output coupler
C385S135000, C385S136000, C385S137000, C385S147000, C430S290000
Reexamination Certificate
active
06532327
ABSTRACT:
FIELD OF THE INVENTION
The invention relates to a process and equipment for conveniently handling a filament in the form of an optical fiber during multiple processing operations that may be at least partially automated. More particularly the invention relates to compact handling of optical fibers during manufacturing operations to include Bragg gratings in at least a portion of their length via a series of manufacturing operations including mechanical stripping, acid stripping, Bragg grating writing, and optical fiber recoating and testing.
BACKGROUND OF THE INVENTION
Glass has been used for centuries as a material of choice in a variety of scientific and domestic applications. From the early use of prismatic glass for separating light into its component colors, glass has been widely used in optical devices that control or adjust the properties of light beams. A recent and rapidly expanding application of the light modifying properties of glass structures involves the drawing of fine filaments of highly purified glass, more commonly referred to as optical fibers, that direct light signals between light transmitting and receiving locations.
During the late 1970s utilities began using optical fiber installations for internal communication, and by the early 1980s, a number of small optical fiber networks were installed. The use of such networks has been growing ever since to replace existing coaxial cable systems. Advantages provided by optical fiber communications networks include lower cost, the use of fewer signal repeaters to correct for signal distortion, and a higher signal carrying capacity than coaxial cable networks.
The capacity of fiber optic systems continues to increase. In 1980, the first systems could transmit 45 megabits per second. Current systems transmit up to 5 gigabits per second. So extensive is the modern use of optical fiber networks that fiber optic networks have essentially replaced all transcontinental copper cable networks and entirely new networks are being created continually. One prediction claims that every continent in the World will become part of a global fiber optic network.
A fiber optic system includes three main parts of transmit circuitry and light source, light detector and receiver circuitry, and fiber. The transmit circuitry converts electronic signals to modulate a light source that generates light signals for transmission. Connection from the light source to a length of optical fiber facilitates transmission of light signals for distances covered by the optical fiber. Attachment of light detector and receiver circuitry at the terminal end of a fiber produces a communication link. The use of multiple communication links provides extended networks of transmitters and receivers.
Interconnection of fiber optic networks requires high precision devices in the form of optical connectors that join optical fibers to peripheral equipment and other optical fibers while maintaining adequate signal strength. In operation an optical connector centers the small fiber so that the light gathering core lies directly over and in alignment with a light transmitting source or another fiber. Sections of optical fiber may also be spliced together using mechanical splicing or fusion splicing techniques.
Special features may be built into selected, relatively short lengths of optical fibers to be spliced into fiber optic networks. A fiber Bragg grating represents a light-modifying feature that may be introduced or written into an optical fiber by simple exposure to ultraviolet light. The ability to write such gratings leads to a variety of devices. For example, Bragg gratings may be applied in telecommunications systems to control the wavelength of laser light, to introduce dispersion compensation, and, in the form of long period gratings, to modify the gain of optical fiber amplifiers. Fiber optic applications of fiber Bragg gratings, outside of telecommunications, include spectroscopy and remote sensing.
The process of introducing special features such as Bragg gratings into an optical fiber may include a number of steps requiring handling of relatively short lengths of optical fiber during a series of manufacturing operations. An optical fiber typically requires removal of protective coatings before changing the physical characteristics of the fiber to include a Bragg grating. After writing a Bragg grating, the fiber may be annealed and recoated.
Little has been revealed about the automation of processes to alter the characteristics of a fiber to provide it with a refractive index grating. Some evidence exists of individual processing steps but not of a type that may be readily incorporated in an automated sequence. Fiber loading for example is described in U.S. Pat. No. 5,988,556. This patent refers to automated winding of a continuous length of fiber from a fiber supply onto first and second sections of a shipping spool. The winder comprises a first device that collects a first portion of a continuous length of fiber and winds it onto the first section of the spool, and a second device for winding a second portion of the continuous fiber onto the second section of the spool. There is no evidence to show that the spooled fiber has a use other than as a shipping package. U.S. Pat. No. 6,027,062 describes an automated winder including fiber supply and collecting devices that move a fiber to a threading device that automatically threads the fiber onto a spool. This is similar to the goal of U.S. Pat. No. 4,511,095 to form of a coil of fiber wound onto a bobbin or similar structure.
The use of stackable cassettes for handling and organizing optical fibers is well known, particularly for storage of lengths of spliced fibers. Cassettes typically comprise shallow dish-shaped holders and enclosures for containment of loosely coiled optical fibers. Loose optical fiber coils do not have the same compact structure as spooled optical fibers. An intermediate form of coiled fiber, described in U.S. Pat. No. 5,894,540, may be produced using an assembly for holding a length of filamentary material in a wrapped configuration with a minimum bend radius. The filament or fiber may be wrapped around spools attached to a support plate. Adjustment of the spacing between spools removes slack from the fiber wrapped around them. Fiber cassettes and related fiber holding assemblies place loose fiber in a tidy condition for storage, usually following interconnection of lengths of optical fiber. U.S. Pat. No. 6,088,503 confirms the use of optical fiber cassettes as holders of optical fibers before, during and after splicing. The patent describes a clamping tool designed to align and hold a pair of fiber ends in preparation for optical fiber splicing.
Cassettes and related fiber organizing assemblies provide tidy storage for optical fibers around connected and spliced sections of optical fiber. There appears to be no evidence of such storage containers used for processing organized lengths of optical fiber during the manufacture of optical fiber devices. One manufacturing process requires the removal of protective buffers and coatings to reveal the bare surface of an optical fiber. Several processes are known for removing protective layers, such as buffers and coatings, from the surface of optical fibers. They include mechanical stripping, chemical stripping and thermal stripping.
Mechanical stripping of optical fibers and related coated filaments requires careful positioning of sharp tempered metal blades to expose a bare surface portion of a fiber without cutting or scratching or otherwise physically damaging the fiber surface. Known methods of mechanical stripping relate to cutting blade design and how a coating may be removed from the surface of a fiber. The predominant use of mechanical stripping involves the removal of protective layers from the ends of optical fibers, insulated wires and related filaments, prior to joining the filament ends together. U.S. Pat. No. 4,434,554 describes an optical fiber stripping device including a flat base having a number of fiber receiving cha
Cowher John Thomas
Cronk Bryon James
Dower William Vogel
Gates Brian John
Gatica Anthony William
3M Innovative Properties Company
Ball Alan
Healy Brian
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