Optical waveguides – With disengagable mechanical connector – Optical fiber/optical fiber cable termination structure
Reexamination Certificate
2002-02-08
2003-07-29
Feild, Lynn (Department: 2839)
Optical waveguides
With disengagable mechanical connector
Optical fiber/optical fiber cable termination structure
Reexamination Certificate
active
06599030
ABSTRACT:
FIELD OF THE INVENTION
The present invention relates generally to methods for manufacturing fiber optic connectors. More particularly, the present invention relates to methods for polishing fiber optic connectors to improve the performance characteristics of the connectors.
BACKGROUND OF THE INVENTION
Fiber optic connectors are used to terminate the ends of fiber optic cables. There are many different fiber optic connector types. Example types of fiber optic connectors include FC-type, SC-type, ST-type and D
4
-type.
FIG. 1
shows a typical connector
10
. A ferrule
12
is located inside the connector
10
. The ferrule
12
is a relatively long, thin cylinder preferably made of a material such as ceramic. Other materials such as metal or plastic can also be used to make the ferrule
12
. The ferrule
12
defines a central opening
14
sized to receive a fiber
16
of a given cladding diameter. An epoxy is typically placed into the opening
14
prior to inserting the fiber
16
to hold the fiber
16
in place. The ferrule
12
functions to align and center the fiber
16
, as well as to protect it from damage.
Referring still to
FIG. 1
, the ferrule
12
is supported within a connector body
18
typically made of a material such as metal or plastic. The connector body
18
is typically bonded to fiber optic cable
20
(e.g., the cable
20
can include a reinforcing layer made of a material such as Kevlar that is affixed to the connector
18
). A strain relief boot
22
protects the junction between the connector
18
and the cable
20
.
Two connectors are preferably interconnected through the use of an adapter
24
. Adapter
24
includes a sleeve
26
sized to receive the ferrules of the connectors desired to be connected. For example, ferrule
12
of connector
10
is inserted into a first end
28
of the sleeve
26
, while a ferrule (not shown) of a connector desired to be connected to the connector
10
is inserted into a second end
30
of the sleeve
26
. As so inserted, the ends of the ferrules abut one another within the sleeve
26
such that their corresponding fibers are held in alignment with one another.
Parameters for evaluating the performance of a connector include insertion loss and return loss. Insertion loss is the measurement of the amount of power that is transferred through a coupling from an input fiber to an output fiber. Return loss is the measurement of the amount of power that is reflected back into the input fiber.
If the back reflection is too great (minimum return loss), it can interfere with the operation of the light source (particularly in single mode systems). Therefore, it is important to minimize the back reflection. For instance, a single mode interconnection with flat end finish can have a return loss of 11 dB which means the return loss is 11 dB down from the incident energy. In other words, if 500 microwatts of energy reaches the fiber end, 40 microwatts would be reflected back. By assuring fiber to fiber contact (eliminating air between the fibers), the return loss can be lowered to over 30 dB which means 500 microwatts would reflect only 0.5 microwatts. The return loss can be even further lowered by polishing the ends of the ferrules to have a rounded polish instead of a flat finish. By round polishing the ends of ferrules, the telecommunications industry has been able to consistent meet the minimum specification of 50 to 55 decibels.
FIG. 2
is a block diagram showing the steps of a convention ferrule polishing technique for providing a rounded ferrule tip. During a first polishing step
70
, a hackle of the fiber and residue epoxy are removed from the ferrule tip typically by a hand-sanding process. After the hackle and epoxy have been removed, the tip of the ferrule is machine polished using two or more polishing films (e.g., of varying coarseness) so as to more precisely form an apex and radius into the tip of the ferrule (see step
72
). Next, the tip of the ferrule is machine polished with a final polish film as indicated by step
74
. During the polishing process, an index layer is formed at the tip of the fiber within the ferrule. The index layer has undesirable optical properties. Thus, at final step
76
, the tip of the ferrule is polished with a cerium oxide film causing the fiber to be recessed slightly into the ferrule a distance sufficient to remove the index layer.
SUMMARY OF THE INVENTION
One aspect of the present invention relates to a fiber optic connector polishing method that yields connectors having improved operating parameters.
A variety of advantages of the invention will be set forth in part in the description that follows, and in part will be apparent from the description, or may be learned by practicing the invention. It is to be understood that both the foregoing general description and the following detailed description are exemplary and explanatory only and are not restrictive of the invention as claimed.
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patent: 4743084 (1988-05-01), Manning
patent: 5461689 (1995-10-01), Matsuoka et al.
patent: 5465314 (1995-11-01), Jie et al.
patent: 5559916 (1996-09-01), Terao et al.
patent: 5631986 (1997-05-01), Frey et al.
patent: 5966485 (1999-10-01), Luther et al.
patent: 6120359 (2000-09-01), Ohno et al.
patent: 6142676 (2000-11-01), Lu
patent: 6157863 (2000-12-01), Chandler et al.
patent: 6276842 (2001-08-01), Xu et al.
“ADC Fiber Optic Technical Seminar,”ADC Telecommunication, Inc., First Edition, Issue 2, pp. 6.1-6.50 (Mar. 1997).
“ADC FasTerm™ Multimode LX.5 Connector Installation Instructions,”ADC Telecommunications, Inc., Issue 1, pp. 1-25 (Jun. 1999).
“ADC FasTerm™ Multimode LX.5 Connector Installation Instructions,”ADC Telecommunication, Inc., Issue 1, pp. 1-27 (Mar. 2001).
“ADC FasTerm™ Multimode LX.5 Connector Installation Instructions,”ADC Telecommunications, Inc., Issue 2, pp. 1-25 (Apr. 2001).
“Assembly Instructions for LC™ Fiber Optic Behind-The-Wall (BTW) Connectors,”Lucent Technologies, Bell Labs Innovations, Issue 3, pp. 1-35 (Jul. 1999).
“Figs. 1 and 2 and the Background of the present application relating to admitted prior art” 4 pages (Filed Feb. 8, 2002).
ADC Telecommunications Inc.
Feild Lynn
Hyeon Hae Moon
Merchant & Gould P.C.
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