Optical waveguides – Optical fiber waveguide with cladding
Reexamination Certificate
1999-07-30
2002-01-29
Sanghavi, Hemang (Department: 2874)
Optical waveguides
Optical fiber waveguide with cladding
C385S125000, C385S126000, C385S117000, C606S015000, C606S016000, C606S021000, C604S020000, C604S021000
Reexamination Certificate
active
06343174
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The invention relates generally to medical optical fiber laser systems requiring fluid delivery, and more specifically to laser delivery fibers that incorporate fluid delivery channels within the fiber.
2. Invention Disclosure Statement
Laser systems can operate as beneficial and effective medical instruments. They allow specific treatment to be administered with minimal invasiveness. Medical laser systems frequently require cooling or irrigation at the distal (output) end of the optical fiber, as well as the site of laser power delivery. Presently, this requires additional channels outside the optical fiber to deliver the fluid. However, irrigation doesn't reach the treatment site as effectively as desired if it is delivered proximally but not directly to the area of laser power treatment. Similarly, hollow optical fibers may be used. With these fibers, the laser power is delivered through a central hollow core. If hollow optical fibers are used, a gaseous medium can also be passed through the fiber's hollow center along with the laser energy. However, hollow optical fibers are typically limited to CO
2
laser delivery and therefore to certain wavelength and physical effects caused by this radiation. For instance, the gaseous medium employed cannot absorb light at the same wavelength as the laser because it might then interfere with delivery of the laser energy.
Medical laser delivery systems employing external irrigating or cooling channels often require the insertion of a catheter into the body through which interchangeable components are inserted. This system generally necessitates a large entry hole to accommodate a large bore catheter to serve as a channel for all the components. Use of this system inevitably increases the surgery time, simply by the fact that the operator must remove and insert varying components into the catheter sheath. A sampling of such inventions is provided below.
U.S. Pat. No. 5,203,780 describes a device for venting laser smoke plumes generated by laser treatment of body tissues. The smoke is directed away from the treatment site through a venting space surrounding the optical fiber; driven by an external vacuum. The device however, involves placing a catheter containing an insertion needle into the treatment site, removing the needle component, and then placing in the desired optical lasing device. By necessity, the bore of the catheter must be larger than that of the treatment fiber resulting in the need for a larger entry hole. In addition, for this particular invention, the space between the wall of the catheter and the optical fiber serves as a conduit for the vacuum to draw smoke from the site. The presence of that space requires that the bore of the catheter be even larger. A typical example of this type of device can be seen in FIG.
1
. There, optical fiber
2
is passed through catheter
1
while catheter distal end
3
is inserted into tissue
4
. The entry hole has to be larger than the bore of fiber
2
to accommodate distal end of the catheter
3
. Should device
100
function also to deliver or remove fluid from the treatment site, then catheter bore and insertion hole will be even greater in order to allow a passageway around fiber
2
and into catheter
1
. Two additional factors of a typical device would increase the bore size of catheter
1
. First, to prevent the collapse of catheter
1
if a vacuum were applied to device
100
would require thicker walls and hence a greater bore. Second, to prevent movement of optical fiber
2
inside catheter
1
and to maintain a uniform passage space around optical fiber
2
, there must be ribbing
5
within catheter
1
to prevent kinking or twisting of optical fiber
2
.
U.S. Pat. No. 4,707,073 describes a non-medical system for the delivery of a high power laser through an optical fiber for use in cutting, drilling, or welding metal where the fiber (and subsequently the work material) is cooled by gas passed coaxially over it. This is achieved through an outer tube surrounding the fiber into which gas is injected. The gas travels along the outer length of the fiber and is emitted out onto the work surface. The system however, provides only a broad exposure of the coolant to the surface receiving the laser energy. The cooling effect is therefore unfocused and non-specific. Applications requiring a more directed coolant would need a specific, and controlled delivery. Further, by having an external coolant-delivery component, it increases the overall diameter of the delivery fiber which in turn decreases the fiber's flexibility and makes use of the device more cumbersome.
U.S. Pat. No. 4,764,194 describes a process for the production of optical fibers wherein a hollow channel comprises the core, surrounded by a layer of cladding material. Hollow optical fibers have been employed in situations where they are needed to carry a wavelength that is difficult to transmit through a solid core optical fiber. For example, utilizing a hollow optical fiber when transmitting a mid-infrared laser. However, wavelengths in the ultraviolet, visible and near-visible IR regions are better transmitted through a solid core fiber, such as a silica fiber. Therefore, the advantages of using a hollow core fiber are highly restricted to certain wavelength transmissions. For most applications, a hollow optical fiber would perform poorly in comparison to a solid counterpart. It would be advantageous to have a system that employs a solid fiber to deliver the energy. The present proposed invention includes a solid laser delivery optical fiber.
U.S. Pat. No. 5,471,553 describes a method for the preparation of light-guide fibers containing a central hollow area surrounded by a peripheral resin layer containing a multiple arrangement of cores. The multicore hollow optical fiber can be used as a compact light guide for devices inserted in its hollow channel (i.e. an endoscope, a laser, an optical fiber, etc.). The hollow channel does not deliver any cooling media nor do the multicore fibers function for anything more than a light-guide. The device then increases the treatment time by requiring the insertion of various implements through the channel.
Further, the hollow fiber described is constructed out of plastic, whereas the present invention calls for fabrication of the fibers out of silica glass. Plastic and glass are very different materials as are the fibers that they comprise. For example, production conditions such as the softening temperature are distinct. Therefore, the use of a plastic optical fiber for instance, precludes any application requiring a glass optical fiber instead.
The present invention describes a device and method to overcome the abovementioned limitations by providing a system that incorporates fluid delivery channels within a solid core optical fiber.
OBJECT AND SUMMARY OF THE INVENTION
It is an aim of the present invention to describe a method and device to deliver a fluid (gas, pure liquid, suspension, emulsion, or solution) through an optical fiber that has at least one core section guiding the laser radiation as well as fluid delivery channel or channels within the fiber to provide a conduit for the medium to be delivered to the treatment site at or close to its distal end.
It is another aim of the present invention to place fluid delivery channel or channels within the cladding layer of the optical fiber.
It is a further aim of the present invention to place fluid delivery channel or channels within the core of the optical fiber in which case, the laser energy may be coupled to the delivery system through a suitable ring mode coupler.
It is also an aim of the present invention to place an independent cladding layer, separate from the cladding of the fiber, encompassing any delivery channels within the core to prevent evanescent waves from interfering with delivery of the laser power.
Still another aim of the present invention is to pass fluids through the delivery channels to irrigate or cool the site of laser delivery
B J Associates
CeramOptec Industries Inc.
Sanghavi Hemang
Skutnik Bolesh J.
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