2. Technical Background One function of an optical fiber splicer is to provide a consistent heating source for joining together optical fibers. One type of fusion splicer joins optical fibers together by melting the ends of the fibers together in a plasma field. The plasma field is initiated when high voltage is applied across two electrodes in the splicer. Typically, plasma fusion splicers use tungsten electrodes with pointed ends. The plasma arc initiates off the pointed ends of the tungsten electrodes, because the tip to tip gap is the path of lowest electrical resistance. The tungsten electrodes used in plasma fusion splicers age over time, resulting in fluctuations of the plasma heating intensity. Two factors influence the aging of the electrodes, the deposition of non-conducting volatiles released from the optical fibers when they are heated and the oxidation of the electrodes. Non-conducting volatiles, of which silica is an example, deposit on the electrode tips due to the operating temperature limitations of the tungsten electrodes.

To keep the tungsten from oxidizing, the electrodes are typically operated below 600°C, the oxidation temperature of tungsten in air. The plasma field itself, however, reaches temperatures greater than 2000°C resulting in the volatilization of

some fiber constituents. The relatively low electrode operating temperature permits volatiles generated in the melting of the fibers to deposit on the electrode. This deposit continues to build with use of the splicer. Eventually, the plasma field begins to "walk", i. e., the arc fires from different places on the electrode tip, or"flicker", i. e., the arc will fire off multiple areas on the electrode during a splice. Inconsistent arcing results in inconsistent plasma heating of the optical fibers and results in higher optical loss splices, lower production yields and increased maintenance cost.

SUMMARY OF THE INVENTION One aspect of the present invention relates to an electrode for use in optical fiber splicing. The electrode includes an electrically conductive core having a discharge end and an insulator. The insulator surrounds the electrically conductive core, and the operating temperature of the discharge end is greater than the deposition temperature of volatiles released during the splicing process.

Another aspect of the present invention relates to an electrode for use in optical fiber splicing. The electrode includes an insulator surrounding an electrically conductive core. The electrically conductive core has a discharge end from which the plasma field is initiated and sustained throughout the splice. The electrode also includes a base that electrically and mechanically connects the conducting core to a fusion splicer. The operating temperature of the discharge end is high enough to prevent the volatiles generated during the splicing process from depositing on the electrode.

The high performance electrode of the present invention results in a number of advantages over prior art electrodes. For example, the high performance electrode of the current invention has an operating temperature greater than the deposition temperature of volatiles generated during the splicing process. Thus, formation of deleterious deposits on the splicer electrode tips is significantly reduced. By reducing the amount of silica based deposit on the electrode tips, the splicer provides more consistent plasma heating.

Another advantage of the present invention is the repeatability of arc initiation of the electrode tip design over the traditional pointed electrodes. Surrounding the

electrode tip with an insulator ensures that the arc initiates from the same location over the life of the electrode.

Another advantage of the present invention is the ability of the electrode to initiate and sustain arcs at higher temperatures. Operating plasma fusion splicer electrodes at higher temperatures reduces the deleterious impact of silica based deposits with respect to arc walking and flickering.

Another advantage of the present invention is the reduction in volatiles deposited on the electrode improves the strength of the splice. During the splicing process, fragments of deposits can loosen from the electrodes and be transferred to the optical fibers via the plasma field. The impurities result in potential fracture initiation sites within the optical fibers resulting in lower mechanical strength splices.

Another advantage of the present invention is that no modifications to existing plasma fusion splicing machines are required.

Additional features and advantages of the invention will be set forth in the detailed description which follows, and in part will be readily apparent to those skilled in the art from that description or recognized by practicing the invention as described herein, including the detailed description which follows, the claims, as well as the appended drawings.

It is to be understood that both the foregoing general description and the following detailed description are merely exemplary of the invention, and are intended to provide an overview or framework for understanding the nature and character of the invention as it is claimed. The accompanying drawings are included to provide a further understanding of the invention, and are incorporated in and constitute a part of this specification. The drawings illustrate various embodiments of the invention, and together with the description serve to explain the principles and operation of the invention.

BRIEF DESCRIPTION OF THE DRAWINGS Figure 1 is a cross-sectional view of an electrode in which the present invention is embodied; Figure 2 is a cross-sectional view of an alternative electrode embodiment of the present invention;

Figure 3 is a cross-sectional view of an alternative electrode embodiment of the present invention.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Reference will now be made in detail to the present preferred embodiment of the invention, an example of which is illustrated in the accompanying drawing.

Wherever possible, the same reference numbers will be used throughout the drawing to refer to the same or like parts. An exemplary embodiment of the electrode of the present invention is shown in Figure 1, and is designated generally throughout by reference numeral 10.

In accordance with the invention, the present invention for a high performance electrode for the fusion splicing of optical fibers includes an electrically conducting core 12. The size of the conducting core 12 is chosen so that the discharge end 26 will operate above the deposition temperature range of volatiles generated during the splicing process, which begins at about 600°C for silica. Exemplary of this is a conducting wire, having a diameter of from. 008 inch to. 040 inch. An important consideration is that the discharge end 26 of the conducting core 12 may oxidize at this operating temperature. It is desirable that materials that do not oxidize or that oxidize slowly at these operating temperatures are used for the conducting core 12. Exemplary materials for the conductoring core 12 are carbon, carbon-graphite, iridium, platinum, platinum-rhodium alloys, rhodium and tungsten. The higher temperature conducting core material will arc at a higher temperature, reducing the impact of silica based deposits with respect to arc walking and flickering. The reduction in inconsistent arcing and therefore providing a more consistent plasma heating source results in lower loss optical splices.

An insulator 14 surrounds the conducting core 12. The discharge end 26 of the conducting core 12 may be recessed with in the insulator 14, flush with the surface 28, or extend beyond the surface 28.

The insulator 14 is a high temperature, low electrical conductivity material that keeps the arc contained to fire from only the discharge end 26. The present invention improves the stability of the electrode because the insulator 14 dictates that the conducting core 12 fires from the same location over the life of the electrode. The

insulator 14 may be configured to focus the plasma field to fire directly off of the discharge end 26. Exemplary materials for the insulator 14 include alumina, silicon carbide and zirconia. The conducting core 12 may be recessed into the insulator 14 to aid in focusing the arc, extend beyond the insulator 14 or be flush with the end of the insulator 14. The tip may be flat faced, as shown in Figure 1, conical, hemispherical, or a variety of other geometric shapes.

The insulator 14 is intended to mate as closely as possible to the conducting core 12. Figure 1 shows an electrode 10 having an insulator 14 with an inside diameter that is slightly larger than the conducting core 12 diameter. The outside diameter of the insulator 14 is chosen to allow installation of the electrode 10 in a fusion splicer.

Exemplary of this is an insulator 14 that is a sleeve having an inside diameter of about . 021 inch and an outside diameter of about. 050 inch for a conducting core 12 having a diameter of about. 020 inch. The insulator 14 may be a separate extruded sleeve, injection molded around the conducting core 12 or cast around the conducting core 12.

Figure 1 illustrates an embodiment of the present invention. A base 18 is made from an electrically conductive material, exemplary of which are tungsten, stainless steel and copper. The base 18 is sized to fit the electrode receptacle of a plasma fusion splicer and conducts electrical power provided by the fusion splicer to the conducting core 12. The base 18 has a receptacle 20 for engagement with a conducting core 12.

Exemplary of different receptacle 20 types are counter bores, stopped holes, through holes and threaded holes. The conducting core 12 is attached to the base 18 using silver soldered or another electrically conductive attachment means, exemplary of which are brazing, welding, a threaded interface or an interference fit. The conducting core 12 is made from carbon, iridium, platinum, rhodium, a platinum-rhodium alloy or tungsten. An insulator 14, in the form of an insulating sleeve, is positioned around the conducting core 12. Exemplary of insulators 14 are extruded insulating sleeves made from alumina, silcon carbide and zirconia. The insulator 14 is attached to the base 18 by a layer of adhesive putty 22. Exemplary of adhesive putties are ceramic cements, ceramic putties and refractory cements. The insulator 14 may be tapered, approximating the size and shape of traditional tungsten electrodes, in order to provide clearance for the plasma fusion splicer's fiber alignment optics. The flange 24 is a reference surface used in setting the position of the electrode 10 in a fusion splicer. The

discharge end 26 of the conducting core 12 may be recessed with in the insulating sleeve 14, flush with the surface 28, or extend beyond the surface 28.

Figure 2 illustrates an alternative embodiment of the electrode of the present invention in which the receptacle 20 is a through hole.

An alternative electrode embodiment of the present invention is illustrate is Figure 3. The conducting core 12 is made to closely resemble in size and shape a traditional pointed tungsten electrode. The conducting core 12 is made from carbon, iridium, platinum, rhodium, a platinum-rhodium alloy or tungsten. The insulator 14 is deposited onto the conducting core 12 using flame deposition techniques, exemplary of which is flame spraying a ceramic material. Exemplary materials for the insulator 14 are alumina, silicon carbide and zirconia. The insulator 14 leaves only the discharge end 26 uncovered. The discharge end is typically a 30 degree cone. The insulator 14 completely covers the discharge end 26 except for the exposed conical tip 34. The length of the exposed conical tip 34 is chosen to facilitate the splicing of a particular type of fiber. Typically, the exposed conical tip 34 has a base diameter a in the range from about. 008 inch to about. 040 inch. The insulator 14 extends a distance b along the conducting core 12 away from the base of the exposed conical tip 34. The distance b is chosen to prevent the arc from moving away from the exposed conical tip 34.

It will be apparent to those skilled in the art that various modifications and variations can be made to the present invention without departing from the spirit and scope of the invention. Thus, it is intended that the present invention covers the modifications and variations of this invention provided they come within the scope of the appended claims and their equivalents.