High power optical adapter

Details High power optical adapter High power optical adapter

2000-04-27

2002-10-29

Patel, Tulsidas (Department: 2839)

Optical waveguides

With disengagable mechanical connector

Structure surrounding optical fiber-to-fiber connection

Reexamination Certificate

active

06471417

ABSTRACT:

FIELD OF THE INVENTION
This invention relates generally to a method and system for use in optical fiber technology. More particularly, this invention relates to a method and system for providing a high power optical adapter.
BACKGROUND OF THE INVENTION
In fiber optical transmission systems, high power optical signals are being broadly employed to increase their transmission capacity over a greater distance. However, those of ordinary skill in the art now encounter technical problems and limitations as the optical signals are transmitted through the fiber optic system with higher power.
FIGS. 1A and 1B
illustrate a specific example of such technical problem in a fiber optical transmission system where optical connectors are commonly employed to provide low loss coupling of optical fibers. A standard single-mode optical fiber
15
is commonly connected to a standard optical connector
20
. Each connector
20
has a ferrule
25
to surround and support the optical fiber
15
and to extend from the front end of the connector
20
to form a mating optical-fiber extension
30
. A mating sleeve
40
has two mating inlet
35
to receive the optical-fiber extension
30
such that two segments of optical fiber can now closely engage to each other with accurately end-surface-to-end-surface alignment for optical signal transmission. Referring to
FIG. 1B
where two end surfaces
45
of two optical fibers
15
are mated with the mating sleeve
40
to engage to each other at an interface surface
50
.
When the optical connectors are connected and disconnected in the process of carrying out the system tests, the end surfaces
45
of the fiber of the optical connectors are often contaminated from dirt, debris, grease and other contaminants. Damages often occur to the connectors
20
with the contaminants now deposited on the end-surfaces
45
of the optical connectors. Under the conditions of signal transmission of optical signals with higher power, the optically non-transmissive contaminants absorb the optical energy and become heated up by the optical signals. The heated contaminants continuously scorch, pit and finally damage the fiber end surfaces of the optical connectors. At the end, the optical connectors
20
lose the optical transmission function thus generates a problem for the entire optical signal transmission system. Due to the facts that the contaminants are very small particles and the end surfaces
45
of the connectors have very small surface areas, the problems caused by the contaminated end-surfaces in the connectors cannot be easily resolved by applying cleaning processes.
Specifically, the most popular optical connectors employed in fiber optical signal transmission systems are connectors for connecting standard single mode fibers having a mode filed diameter (MFD) of about 10 um at 1550 nm wavelength. Due to the small MFD, a very high power density is presented in transmitting the optical signals because the smaller the cross sectional area the higher the power density. Furthermore, due to the small MFD and high power density, the problems of heat generation as a result of contaminant deposit on the end surfaces
45
of the fiber connectors
20
are becoming more serious. With increased power of the signals transmitted in the optical fiber signal transmission system, the thermal damage problems becomes even more serious and an urgent demand now exists to resolve this difficulties as soon as possible.
Many efforts have been devoted to address this problem in attempt to reduce the damaging effects arising from deposit of the contaminants on the end surfaces. One approach is to reduce the power density of the optical signals at the end surfaces of the connector fiber. At these end surfaces, an operation is often carried out to connect or disconnect for system testing and other types of system reconfigurations. Most likely, the contaminants are deposited on the end surfaces. By increasing the surface area of the end surfaces will reduce the thermal damage problems as the power density is decreased with the increase of the surface area. Reduction in power density will also proportionally reduce the energy absorption and results in a lower level of heat generation. Hence, by enlarging the MFD of the optical fiber would therefore lead to a reduced power density and consequently lower level of heat generation due to optical energy absorption.
In the U.S. Pat. No. 5,594,825, special optical connectors are disclosed as that shown in
FIGS. 2A and 2B
. In the patented optical connectors, Kawasake et al. employ the thermal expand core (TEC) fibers which have special configuration near the end of the fiber where the surface areas are enlarged as that shown FIG.
3
B. In order to reduce the unwanted effects of the connectors associated with high power density, the optical connector ferrule
25
′ is specially shaped to adopt the TEC fibers. By replacing the standard single mode fibers with the TEC fibers
15
′, the end surface areas
45
′ are significantly enlarged because the MFD of the TEC fibers
15
′ are typically 2-3 times larger than that of the standard single mode fibers, The area of the end surfaces
45
′ is enlarged four to nine times. The power density of the optical signals is proportionally reduced to a lower level at the end surfaces
45
′ of the TEC fibers
15
′ than that at the end surfaces
45
of the standard single mode fibers
15
. The thermal problems caused by contaminant heating thus become less serious at the end surfaces
45
′ of the TEC fibers
15
′ than that at the end surfaces
45
of the standard single mode fibers
15
. Thus, the risks of connector damage caused by overheating at the fiber end surfaces
45
′ of the optical connectors are substantially reduced.
Even though the special optical connectors
20
′ utilizing TEC fibers
15
′ can function properly and the damages caused by overheating in the connectors due to contaminant deposit are reduced, practical application of these types of connectors generates additional difficulties and inconveniences. For the purpose of employing the special TEC optical connectors
20
′ on the existing fiber optic signal transmission systems, the installed standard optical connectors
20
has to be cut off from the single mode fibers
15
of the fiber optical transmission systems. Then, the special optical connectors
20
′ must be spliced into the single mode fibers
15
of the fiber optical transmission systems. Due to the facts that the special optical connectors
20
′ are not compatible with the standard optical connectors
20
, this kind of fiber cutting and splicing need to be repeated many times during the system test and thus is very time-consuming. These additional cutting and splicing processes may also lead to further reliability or signal transmission problems if these cutting and splicing processes are not performed according to certain system specification. Practical difficulties thus arise from significant increase in production cost by implementing TEC fiber connector
20
′ for providing a high-power fiber optical signal transmission systems.
Therefore, a need still exists in the art of design and manufacturing fiber-optic signal-transmission system to provide new configuration and method of manufacture the signal transmission system to overcome the difficulties discussed above. Specifically, high power optical adapters that are readily compatible with the existing fiber optical connector that can be provided at a relatively economical production cost at large quantity would be most desirable. It is also necessary to provide more flexibility and convenience of assembling and disassembling for system tests and reconfiguration such that these tasks can be more easily performed.
SUMMARY OF THE PRESENT INVENTION
It is therefore an object of the present invention to provide a new and low-cost configuration for interconnecting optical fibers suitable for high power transmission without the inconveniences of repetit

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