Optics: measuring and testing – For optical fiber or waveguide inspection
Reexamination Certificate
2000-04-13
2002-04-09
Font, Frank G. (Department: 2877)
Optics: measuring and testing
For optical fiber or waveguide inspection
C356S213000, C356S215000, C356S236000, C250S228000, C385S052000
Reexamination Certificate
active
06369883
ABSTRACT:
FIELD OF INVENTION
The present invention relates to optical fibers and more particularly, the present invention relates to an enhanced mass splice measurement system for testing a plurality of optical fiber splices and also the reliability of the splicer itself.
BACKGROUND OF INVENTION
In present wired telecommunications systems, fiber optic cables have become the standard transmission line through which large quantities of data can be transmitted in the form of infrared light. A standard fiber optic cable is made up of a plurality of individual fibers generally made from multi-component glass, quartz, synthetic resins and/or other material. The individual fibers are generally placed within a plurality of plastic and/or metal tubes. The plurality of plastic or metal tubes may be bundled together and further protected by outer and inner jackets made of metal, plastic, Kevlar, rubber and/or any combination thereof.
Like many other cables, due to manufacturing and/or practical limitations, only limited lengths of fiber optic cable can be placed on a single reel. Accordingly, the fiber optic cable may need to spliced together several times with other fiber optic cables to reach the desired destination. Splicing is accomplished by either fusing or melting two optical fibers together using a fiber optic splicer or, in the alternative, by using a mechanical connection to attach the individual fibers together. Although splicing is preferred, splicing the glass fibers together introduces losses as the light is reflected and/or possibly refracted at the splice points. Accordingly, it is desirable to determine the integrity of the splice and thus, the reliability of the splicer itself (i.e., which optical fiber splicers produce splices with minimum losses at the splice points). Although most modern splicers are able to estimate splice losses, but to accurately determine splicer reliability, actual or true loss is desirable.
FIGS. 1-3
illustrate conventional methods for determining the reliability of fiber optic splicers.
FIG. 1
illustrates a conventional method for measuring splice loss and determining splicer reliability utilizing Optical Time Domain Reflectometers (OTDR)
101
,
105
. As illustrated in
FIG. 1
, fiber optic cable
102
is spliced with fiber optic cable
104
at splice point
103
using any of the known mass fiber fusion splicers (not shown). In this example, both fiber optic cables are twelve (12) fiber ribbon cables. After the individual fibers are prepared (i.e., outer/inner protective jackets and/or buffer tubes are removed, individual fibers cleaned and cleaved, etc.), pigtails
107
,
108
are attached to the ends the individual optical fibers within the cables
102
and
104
, respectively. A pigtail can be, for example, a small section of a single optical fiber that includes an optical connector at one end, and can be connected to a single fiber in the cable via a fusion splice or a mechanical connection. After the pigtails
107
,
108
are connected to the cables
102
,
104
, respectively, the connectorized ends of the pigtails
107
,
108
are attached one at a time to the OTDR
101
. After the first pigtail is connected, the OTDR test on the cables
102
,
104
may begin. OTDR
101
launches a plurality of short high-powered light pulse into the optical fibers and receives back scattered and/or reflected light. The received light signal is displayed on an oscilloscope of the OTDR
101
indicating power loss as a function of the length of the fiber optic cable in a graph format. Accordingly, based on the information displayed OTDR's
101
oscilloscope, the distance of the entire fiber optic cable and light losses can be determined. After the test on the first optical fiber has been completed, the connected pigtail must be disconnected and the next pigtail is connected to the OTDR
101
to test the second optical fiber. Accordingly, to measure loss at the splice point
103
for individual fibers, each optical fiber must be attached to the OTDR via its respective pigtail and tested one at a time. Thus, for a twelve (12) fiber ribbon cable, the above described procedure must be performed twelve times causing this procedure to be highly time consuming. Since, OTDR measurements are direction dependent, it is desirable to perform an OTDR test from both ends of the spliced cable and then average the results to determine the reliability of the optical splicer. The above-described conventional method is disadvantageous because connecting each of the plurality pigtails one at a time to the OTDRs
101
and
105
and performing the OTDR test on each individual fiber from both sides is labor intensive and can be time prohibitive. In addition, loss measurements using OTDRs tend to be less accurate for very long fiber runs. Further, OTDRs commonly require minimum fiber lengths of 50 meters or more making small scale testing impractical. As a general rule, OTDRs tend to be less accurate than other systems using power meters and light sources.
FIG. 2
illustrates another conventional method for measuring the splice loss and determining splicer reliability. As illustrated in
FIG. 2
, OTDR
101
is connected to a 1:12 (i.e., for example, 1 input and 12 outputs) optical switch
201
. Using this method, pigtails
107
connected to fiber optical cable
102
are connected to the outputs of the optical switch
201
. Pigtails
108
connected to fiber optic cable
104
are connected to the outputs of 1:12 optical switch
202
. OTDR
105
is connected to the input side of the optical switch
202
. Under this method, once all the pigtail connectors are connected to their respective optical switch
201
,
202
, the OTDR test may begin. Once all the pigtails
107
,
108
are connected to the optical switches
201
,
202
respectively, the optical switches
201
,
202
are individually operated to complete the OTDR test on each of the optical fibers. In this example, the OTDR test can be performed on the individual fibers without having to manually attach and then remove each pigtail connector to the OTDRs
101
and
105
one at a time. While this method may be more time efficient in determining the losses at splice point
103
than the method as previously described in conjunction with
FIG. 1
, it suffers from other drawbacks. For example, the method as described with respect to
FIG. 2
is disadvantageous in that the introduction of the optical switches
201
,
202
, at both ends, causes additional reflections to be seen by the OTDR which results in inaccuracies.
FIG. 3
illustrates yet another conventional method for measuring splice losses and splicer reliability. As illustrated in
FIG. 3
, a laser
301
is connected to the output side of an 1:12 optical switch
302
. The pigtails
107
connected to the first ends of fiber optic cable
102
are connected to the output side of optical switch
302
. Similarly, pigtails
108
connected to the first ends of fiber optic cable
104
are connected to an input side of a 12:1 (i.e., for example, 12 inputs and 1 output) optical switch
303
. The output end of optical switch
303
is connected to a light meter
305
.
To determine true loss at splice point
103
and splicer reliability, using the method illustrated in
FIG. 3
, it is required that reference measurements be taken at splice points
103
for both cables
102
and
104
, prior to any splicing. A reference measurement for cable
102
may be taken by coupling a light meter (not shown) to the second ends of cable
102
(i.e., at splice point
103
). This method requires connecting or splicing pigtails (not shown) to the second ends of the optic cable
102
and further coupling each of the pigtail connectors to the optical switch. Reference measurements are taken by the light meter (not shown) at splice point
103
by cycling the optical switch to permit the transmission of light generated by laser
301
through each of the optical fibers. The laser
301
transmits light signal at a predetermined power level and the received power level is measured using a light meter. The abo
Amherst Holding Co.
Banner & Witcoff , Ltd.
Font Frank G.
Nguyen Sang H.
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