Optics: measuring and testing – For optical fiber or waveguide inspection
Reexamination Certificate
2001-01-29
2003-07-08
Nguyen, Tu T. (Department: 2877)
Optics: measuring and testing
For optical fiber or waveguide inspection
Reexamination Certificate
active
06590642
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to an inspection apparatus for inspecting a fiber having optical connectors, which apparatus measures the return loss and insertion loss of a fiber having optical connectors.
Fibers having optical connectors have been used in considerably broad fields, such as the field of optical transmission systems and the field of optical device measurement. In order to improve production efficiency, a process of manufacturing a fiber having optical connectors is demanded to measure a return loss and an insertion loss, which are basic characteristics of an optical connector, without involvement of intricate operations and within a short period of time.
A related-art method of measuring a return loss of an optical connector will be described by reference to FIG.
5
. As shown in
FIG. 5
, a fiber inspection system
200
having an optical connector for use with the related-art return loss measurement method comprises a light source
1
; an optical branch coupler
2
; a first optical sensor
3
; a refractive index matching material
6
; a master optical connector
7
; and an optical terminator
20
. Optical connectors are provided on both ends of a measured optical fiber
5
. In the following description, an optical connector provided on one end of the optical fiber
5
and connected to the master optical connector
7
, is called a first optical connector
8
, and an optical connector provided on the other end of the optical fiber
5
is called a second optical connector
9
.
Conventionally, when the return loss of an optical fiber having connectors is measured, the light source
1
is connected to a first terminal
2
a
of the optical branch coupler
2
, and the first optical sensor
3
is connected to a second terminal
2
b
of the optical branch coupler
2
. The master optical connector
7
is connected to a third terminal
2
c
of the optical branch coupler
2
, and the optical terminator
20
is connected to a fourth terminal
2
d
of the optical branch coupler
2
. Fresnel reflection arising at the master optical connector
7
is received by the first optical sensor
3
, and the power of the thus-received light is taken as a reference.
The first optical connector
8
of the measured optical fiber
5
is connected to the master optical connector
7
, and the second optical connector
9
of the measured optical fiber
5
is terminated with the refractive index matching material
6
. With such an arrangement, light reflected from the measured optical fiber
5
is received by the first optical sensor
3
. A difference between the power of the thus-received light and the reference is computed, thereby computing a return loss.
A related-art method of measuring insertion loss of an optical connector will now be described by reference to FIG.
6
B. As shown in
FIG. 6B
, an inspection system
201
for inspecting an optical fiber having connectors and for use with a related-art method of measuring an insertion loss of a connector comprises a light source
1
; a master optical connector
7
; and an optical sensor
21
. A measured fiber
5
is provided with an optical connectors
8
and
9
in the same manner as the measured fiber
5
shown in FIG.
5
.
Conventionally, when an insertion loss of an optical fiber having connectors is measured, an output of the light source
1
is connected to an input of the optical fiber, in the same manner as in an inspection system
201
′ for inspecting a fiber having optical connectors shown in FIG.
6
A. Light output from the master optical connector
7
is received by an optical sensor
21
, and the power of the thus-received light Pc is taken as a reference value. In the same manner as in an inspection system
201
for inspecting a fiber having optical connectors shown in
FIG. 6B
, the measured optical fiber
5
is connected to the master optical connector
7
, and light output from the master optical connector
7
is received by an optical sensor
21
. A difference between the power Py of the light received by the optical sensor
21
in this case and the reference value Pc is taken as an insertion loss of the connector.
A related-art expression for computing an insertion loss of a connector is expressed as Eq. (1).
IL=−
10 log(
Pc/Py
)+10 log &agr; (1)
where &agr; represents the transmissivity of an optical fiber.
According to the related-art technique, the return loss of the measured optical fiber
5
and the insertion loss of the same are measured separately through use of different measurement systems. Hence, the measured optical fiber
5
must be reconnected for changing the measurement item. A result of measurement corresponds to measure value of the entire system, including both the measured optical fiber
5
and the optical connectors, thereby rendering vague in a decision as to whether or not processed optical connectors are non-defective.
SUMMARY OF THE INVENTION
The present invention is aimed at improving inspection efficiency during a process of manufacturing a fiber having optical connectors, by means of measuring a return loss and an insertion loss, which are basic characteristics of an optical connector, without reconnection of an optical fiber to be measured.
In order to solve the drawbacks, a first aspect of the present invention provides an inspection apparatus for inspecting an optical fiber having two optical connectors at both ends thereof, comprising:
an optical branch coupler (for example, an optical branch coupler
2
shown in
FIG. 1
) having a first to four input/output terminal (for example, a first terminal
2
a
, a second terminal
2
b
, a third terminal
2
c
, and a fourth terminal
2
d
, which are shown in FIG.
1
), the optical branch coupler branching and outputting light to third and fourth terminals when the first or second terminal is taken as an input terminal, the optical branch coupler branching and outputting light to the first and second terminals when the third or fourth terminal is taken as an input terminal;
a light source (for example, a light source
1
shown in
FIG. 1
) connected to the first terminal of the optical branch coupler;
a first optical sensor (for example, a first optical sensor
3
shown in
FIG. 1
) connected to the second terminal of the optical branch coupler;
a second optical sensor (for example, a second optical sensor
4
shown in
FIG. 1
) connected to the fourth terminal of the optical branch coupler;
a master optical connector (for example, a master optical connector
7
shown in
FIG. 1
) connected to the third terminal of the optical branch coupler; and
a measurement unit (for example, a measurement unit
10
shown in FIG.
2
),
wherein Fresnel reflection occurs in a state where the master optical connector is released, power of the Fresnel reflection received by the first optical sensor is defined as a first reference;
the measurement unit measures an insertion loss based on the first reference and power of light received by the first optical sensor when one of two optical couplers of the optical fiber is connected to the master optical connector and the other thereof is released; and
when one of two optical couplers of the optical fiber is connected to the master optical connector and the other thereof is terminated, the measurement unit measures a return loss based on power of light received by the first optical sensor and power of light emitted from the light source and received by the second optical sensor.
According to a first aspect of the present invention, the light source is connected to the first terminal of the optical branch coupler having four input/output terminals; the first optical sensor is connected to the second terminal of the same; the master optical connector is connected to the third terminal of the same; and the second optical connector is connected to the fourth terminal of the same. Fresnel reflection occurs in a state where the master optical connector is released, and power of the Fresnel reflection received by the first optical sensor is d
Ando Electric Co. Ltd.
Fish & Richardson P.C.
Nguyen Tu T.
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