JP2009103669A - Optical fiber inspection device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an optical fiber inspection device at a low cost which can easily measure loss at one end of the optical fiber. <P>SOLUTION: The optical fiber inspection device A includes: an optical branching/coupling unit 1 connected to the one end of the optical fiber B to be measured; a light source 2 and a light receiving unit 3 connected to the optical branching/coupling unit 1; and a measurement unit 4 for measuring an output voltage of the light receiving unit 3. The optical branching/coupling unit 1 has three terminals: a first terminal 1a is an input terminal connected to the light source 2, a second terminal 1b is an output terminal connected to the light receiving unit 3, and a third terminal 1c is connected to the optical fiber B to be measured, wherein light input from the first terminal 1a is output via the third terminal 1c to the optical fiber B to be measured; the light input from the optical fiber B to be measured via the third terminal 1c is output to the light receiving unit 3 connected to the second terminal 1b; and the light source 2 has a control unit 2c for maintaining emitting light power at a constant level. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention relates to an optical fiber inspection apparatus for measuring optical loss of an optical fiber line using an optical pulse tester.

  Conventionally, as a method for measuring the loss of an optical fiber, a method in which only an optical fiber is installed and an optical connector is temporarily attached to measure the loss is measured. Specifically, a light source is connected to one end of the installed optical fiber, and an optical power meter is installed at the other end for measurement.

  As another measurement method, there is an optical time-domain reflectometer (OTDR) method. In this method, the loss state of the optical wiring system can be measured from one end. Measures backscattered light (scattered light that propagates strongly in the direction opposite to the direction of propagation caused by scattering factors in the optical fiber) generated by propagating a short light pulse from one end of the optical fiber and propagating through the optical fiber over time. Then, the loss of the optical wiring system is measured from the change in the level.

And as shown by Unexamined-Japanese-Patent No. 2003-222573 (patent document 1), the optical fiber test | inspection apparatus using the OTDR method is known. This invention discloses a method for measuring the loss of wiring by measuring the reflected light from a light reflector installed at one end of an optical fiber. In this invention, an optical pulse tester and an optical switch are combined, and the reference and the system to be measured are switched by the optical switch, thereby reducing the influence of the Fresnel reflected light and improving the measurement accuracy.
JP 2003-222573 A

  However, in the conventional example in which a light source is connected to one end of the optical fiber and an optical power meter is installed at the other end, for example, in order to measure the loss of the optical fiber wired to the dwelling unit, it is separated A light source and an optical power meter are placed at each place, and a person who operates these devices is required at each place, and measurement must be performed while keeping in contact with each other. In addition, as shown in FIG. 4, in apartments and the like, a self-operated PT board 100, which is a wiring board called MDF (main distribution frame), is installed at the place where outside wiring is introduced into the apartment, and from there to the residential building An optical fiber B which is an internal wiring is laid. In this case, the measurement is performed by installing the light source 2 at the position of the self-supporting PT panel 100 and connecting the optical power meter 102 via the optical outlet 101 to the end of the optical fiber B of each dwelling unit. In this case, measurement is performed by moving the optical power meter 102 to the optical outlet 101 of each dwelling unit, which is a factor that takes time for measurement.

  The conventional example using the OTDR method is a device combining an optical pulse tester and an optical switch, which is a very complicated and expensive inspection device.

  The present invention has been invented in view of the above-described background art, and an object of the present invention is to provide an inexpensive optical fiber inspection apparatus that can easily perform loss measurement at one end of an optical fiber. It is.

  In order to solve the above problem, in the invention according to claim 1 of the present application, an optical branching coupler connected to one end of the optical fiber to be measured, a light source and a light receiving unit connected to the optical branching coupler, And an optical branching coupler having three terminals, the first terminal being an input terminal connected to the light source, and the second terminal being a light receiving part. The third terminal is connected to the optical fiber to be measured, the light input from the first terminal is output from the third terminal to the optical fiber to be measured, and the optical fiber to be measured The light input through the third terminal is output to the light receiving unit connected to the second terminal, and the light source has a control unit that makes the light power emitted constant. It is a feature.

  The invention according to claim 2 of the present application is characterized in that, in the optical fiber inspection apparatus according to claim 1, both ends of the optical fiber to be measured are subjected to SPC polishing or AdPC polishing.

  In the invention according to claim 2 of the present application, in the optical fiber inspection apparatus according to claim 1 or 2, the measurement unit sets and stores a threshold value in advance, and compares the measurement result of the output voltage of the light receiving unit with the threshold value. It is characterized by being.

  In the optical fiber inspection device according to the first aspect of the present invention, an optical branching coupler connected to one end of the optical fiber to be measured, a light source and a light receiving unit connected to the optical branching coupler, and an output voltage of the light receiving unit And a measurement unit for measuring the light, so that light input and output can be detected at one end of the optical fiber to be measured. As a result, the loss can be measured at one end of the optical fiber to be measured, so that a simple loss measurement can be performed. Furthermore, the optical branching coupler has three terminals, the first terminal is an input terminal connected to the light source, and the second terminal is an output terminal connected to the light receiving unit. The third terminal is connected to the optical fiber to be measured, and the light input from the first terminal is output from the third terminal to the optical fiber to be measured and input from the optical fiber to be measured through the third terminal. Output light to the light receiving unit connected to the second terminal, and since the light source has a control unit that makes the light power emitted constant, the light power emitted by the light source is measured. This eliminates the need for a device to be used and simplifies the configuration of the optical branching coupler, thereby reducing the cost.

  In the optical fiber inspection apparatus according to the second aspect of the present invention, in particular, since both ends of the optical fiber to be measured are SPC polished or AdPC polished, the refractive index of the optical fiber to be measured can be set to a predetermined value. . As a result, the error of loss can be reduced, and the measurement accuracy of loss can be ensured.

  In the optical fiber inspection apparatus according to the third aspect of the present invention, in particular, the measurement unit sets and stores a threshold value in advance, and compares the measurement result of the output voltage of the light receiving unit with the threshold value. It is possible to easily determine whether or not the loss is satisfied.

  1 to 3 show an optical fiber inspection apparatus according to an embodiment of the present invention. The optical fiber inspection apparatus A measures the output branching coupler 1 connected to one end of the optical fiber B to be measured, the light source 2 and the light receiving unit 3 connected to the optical branching coupler 1, and the output voltage of the light receiving unit 3. The optical branching coupler 1 has three terminals, the first terminal 1a is an input terminal connected to the light source 2, and the second terminal 1b receives light. The third terminal 1c is connected to the measured optical fiber B, and the light input from the first terminal 1a is transferred from the third terminal 1c to the measured optical fiber B. The light output from the optical fiber B to be measured via the third terminal 1c is output to the light receiving unit 3 connected to the second terminal 1b. It has the control part 2c which makes it constant. Further, both ends B1 and B2 of the optical fiber B to be measured are subjected to SPC polishing or AdPC polishing. The measurement unit 4 sets and stores a threshold value in advance, and compares the measurement result of the output voltage of the light receiving unit 3 with the threshold value.

  Hereinafter, the optical fiber inspection apparatus of this embodiment will be described in more detail. As shown in FIG. 1, the optical fiber inspection apparatus A according to this embodiment includes an optical branching coupler 1, a light source 2, a light receiving unit 3, a measuring unit 4, and a notification unit 5.

  Optical connectors Ba1 and Ba2 are disposed at both ends of the optical fiber B to be measured, and both ends B1 and B2 of the optical fiber B to be measured are SPC (Super Physical Contact) polishing, which is a polishing in which a high refractive index portion is removed. Alternatively, AdPC (Advanced Physical contact) polishing is performed.

  The optical branching coupler 1 has three terminals 1a, 1b, and 1c. The first terminal 1a is connected to the light source 2 and is an input terminal for inputting light emitted from the light source 2. The second terminal 1 b is an output terminal that is connected to the light receiving unit 3 and outputs light input to the optical branching coupler 1 from the optical fiber B to be measured. The third terminal 1c is connected to the optical connector Ba1 at one end of the optical fiber B to be measured.

  Here, the optical branching coupler 1 outputs the light input from the first terminal 1a to the optical fiber B to be measured from the optical connector Ba1 via the third terminal 1c. Furthermore, the light output from the optical connector Ba1 is input from the third terminal 1c and output to the light receiving unit 3 through the second terminal 1b.

  The optical waveguide of the optical branching coupler 1 is composed of a PLC (planer lightwave circuit) made of polymer or quartz, even if the optical fiber is fused into a Y shape. Also good.

  The light source 2 includes a light emitting unit 2a, a light source light receiving unit 2b, and a control unit 2c. The light emitting unit 2 emits light to be input to the measured optical fiber B in order to perform loss measurement. is there. The light source light receiving unit 2b is disposed in the vicinity of the light emitting unit 2a and receives light emitted from the light emitting unit 2a. The control unit 2c acquires the value of the optical power received from the light receiving unit 2b, and controls the light emitting state of the light emitting unit 2a to be constant based on the acquired value. The controller 2c can be configured by an APC (Auto Power Control) circuit. As a result, it is possible to reduce the cost of equipment by reducing the number of optical components.

  The light receiving unit 3 includes a light receiving element 3a and a current-voltage conversion amplifier 3b. The light receiving element 3 a receives light output from the optical fiber B to be measured that is output via the second terminal 1 b of the optical branching coupler 1. When the light-receiving element 3a receives light, the current-voltage conversion amplifier 3b converts the output of the light-receiving element 3a into current-voltage, amplifies it, and outputs it to the measuring unit 4.

  The measuring unit 4 calculates the loss of the measured optical fiber B using the value of the output voltage acquired from the light receiving unit 3. The measurement unit 4 can set and store a loss threshold value in advance, and the loss of the measured optical fiber B satisfies a predetermined value by comparing the threshold value with the calculated loss value. Whether or not the optical fiber B to be measured can be easily confirmed.

  Further, the notification unit 5 is connected to the measurement unit 4. The notification unit 5 can acquire a loss value of the measured optical fiber B measured by the measurement unit 4 or a comparison result with a set threshold value, and can notify the user of the result. Here, the notification unit 5 may display a loss value or a comparison result with a threshold value using a liquid crystal display, an LED, or the like, or may notify by voice. Furthermore, the alerting | reporting part 5 can also display the comparison result with the value of a loss and a threshold value in time series continuously.

  Next, a method for measuring the loss of the optical fiber B to be measured will be described. When the light source 2 is connected to the optical connector Ba1 at one end of the measured optical fiber B via the optical branching coupler 1, the light emitted from the light source 2 propagates to the optical connector Ba2 at the other end of the measured optical fiber. As shown in FIG. 2, reflection occurs at the boundary surface of the refractive index called Fresnel reflection at the end B2 of the optical fiber B to be measured, and the light returns to the light source 2 side. The transmitted light is attenuated by the loss in the measured optical fiber B (including the connection portion such as the optical fiber and its bend, fused portion, mechanical splice, connector, etc.) on the return and return.

The Fresnel reflection is a reflection that always occurs at the boundary surface of the refractive index. When the refractive index of the optical fiber B to be measured is n0 and the refractive index of air is n1,
Fresnel reflection R = | (n0−n1) / (n0 + n1) | ²
It is represented by For example, when the measured optical fiber B is a quartz optical fiber, the refractive index of the quartz optical fiber is n0 = 1.45 and the Fresnel reflection R is 0.0337 (= -14.72 dB).

The loss measurement in this embodiment is performed using this reflected light. As shown in FIG. 3, the optical power incident on the optical fiber B to be measured is P0 (dBm), the loss of the optical fiber B to be measured is P1 (dB), and the reflection at the end face of the optical connector Ba2 is Pr (dB). Then, the returned optical power P0 ′ is
P0 ′ (dBm) = P0 (dBm) + 2 × P1 (dB) + Pr (dB)
It is represented by

  Here, when the incident power P0 and the returned power P0 'are measured, the reflection Pr is determined by the difference in refractive index between the optical fiber B to be measured and air, so that the loss P1 of the optical fiber to be measured can be obtained. Thus, the loss of the measured optical fiber B can be measured from one end of the measured optical fiber B using this method.

  The reflectivities of the end faces B1 and B2 of the measured optical fiber B are determined by the difference between the refractive index n0 of the measured optical fiber B and the refractive index n1 of air. Although the refractive index n1 of air hardly changes, the refractive index n0 of the end faces B1 and B2 of the optical fiber B to be measured changes depending on the end face polishing method. For example, in PC polishing, the end faces B1 and B2 of the optical fiber B to be measured are polished with diamond particles, etc., and the refractive index n0 of the slight thickness of the end faces B1 and B2 of the optical fiber B to be measured is caused by stress during polishing. Cause a rise. This value reaches 1.54, which is considerably larger than the refractive index of 1.45 of general quartz. The reflection loss due to this refractive index is shown in Table 1.

  Calibration of the measuring unit 4 is performed at n = 1.45. If the refractive index of the end face B2 of the optical fiber B to be measured is 1.57, more light than expected is returned from the optical fiber B to be measured. Therefore, the loss causes an error of 1.64 dB (14.72-13.08). This error is considered large when the loss of the measured optical fiber B is assumed to be about 4 dB.

  Here, when polishing (AdPC: Advanced Physical contact or SPC: Super Physical contact) is performed on the end face B2 of the optical fiber B to be measured, the refractive index is about 1.47. It is considered from Table 1 that an error of 0.31 dB (14.72-14.41) is generated. If this is the case, it is considered acceptable for measuring a loss generally referred to as an assumed loss of 4 dB in the building. Therefore, in the measurement by this method, if SPC polishing or AdPC polishing is used as the polishing of the end faces B1 and B2 of the optical fiber B to be measured, it can be determined that it can be used without any problem.

  In the measurement unit 4, first, the value Vm1 of the output voltage from the light receiving unit 3 in a state where the optical fiber B to be measured is not connected is calculated and stored. Next, the value Vm2 of the output voltage from the light receiving unit 3 with the measured optical fiber B connected is calculated, and the loss of the measured optical fiber B is calculated. Here, the loss can be calculated using an expression represented by L = −1 / 2 × 10 · log (Vm2 / Vm1).

  Therefore, the optical branching coupler 1 connected to one end of the optical fiber B to be measured, the light source 2 and the light receiving unit 3 connected to the optical branching coupler 1, and the measuring unit 4 for measuring the output voltage of the light receiving unit 3. Therefore, light input and output detection can be performed at one end of the optical fiber B to be measured. As a result, the loss can be measured at one end of the optical fiber B to be measured, so that a simple loss measurement can be performed. Further, the optical branching coupler 1 has three terminals, the first terminal 1 a is an input terminal connected to the light source 2, and the second terminal 1 b is an output terminal connected to the light receiving unit 3. Yes, the third terminal 1c is connected to the optical fiber B to be measured, and the light input from the first terminal 1a is output to the optical fiber B to be measured from the third terminal 1c. 3 is output to the light receiving unit 3 connected to the second terminal 1b, and the light source 2 has a control unit 2c that makes the light power emitted constant. Therefore, an apparatus for measuring the optical power emitted from the light source 2 is not required, and the configuration of the optical branching coupler 1 can be simplified, so that the cost can be reduced.

  Further, since both ends B1 and B2 of the measured optical fiber B are SPC polished or AdPC polished, the refractive index of the measured optical fiber B can be set to a predetermined value. As a result, the error of loss can be reduced, and the measurement accuracy of loss can be ensured.

  Further, the measurement unit 4 sets and stores a threshold value in advance, and compares the measurement result of the output voltage of the light receiving unit 3 with the threshold value. Therefore, it is easy to determine whether or not a preset loss is satisfied. can do.

1 is a system configuration diagram of an optical fiber inspection apparatus according to an embodiment of the present invention. It is explanatory drawing about the Fresnel reflection of the end surface of the to-be-measured optical fiber in the same optical fiber test | inspection apparatus. It is explanatory drawing of the measuring method in the same optical fiber test | inspection apparatus. It is a system block diagram in the optical fiber test | inspection apparatus of a prior art example.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Optical branch coupler 1a 1st terminal 1b 2nd terminal 1c 3rd terminal 2 Light source 2b Light source light-receiving part 2c Control part 3 Light-receiving part 4 Measuring part A Optical fiber inspection apparatus B Optical fiber to be measured B1, B2 End face of optical fiber

Claims (3)

  An optical branching coupler connected to one end of the optical fiber to be measured, a light source and a light receiving unit connected to the optical branching coupler, and a measurement unit for measuring the output voltage of the light receiving unit, It has three terminals, the first terminal is an input terminal connected to the light source, the second terminal is an output terminal connected to the light receiving section, and the third terminal is a device under test Connected to the optical fiber, the light input from the first terminal is output to the optical fiber under measurement from the third terminal, and the light input via the third terminal from the optical fiber under measurement is supplied to the second terminal An optical fiber inspection apparatus that outputs to a connected light receiving unit, and the light source has a control unit that keeps the light power emitted constant.   2. An optical fiber inspection apparatus according to claim 1, wherein both ends of the optical fiber to be measured are subjected to SPC polishing or AdPC polishing.   3. The optical fiber inspection apparatus according to claim 1, wherein the measurement unit sets and stores a threshold value in advance, and compares the measurement result of the output voltage of the light receiving unit with the threshold value.

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