JPH06232817A - Optical fiber transmitter and testing method for the same - Google Patents

Abstract

PURPOSE:To detect the fault point of an optical fiber line and to discriminate the optical fiber line by providing a reflective wavelength filter set to reflect mutually different wavelengths at respective subscriber optical transmitters. CONSTITUTION:Subscriber optical transmitters 5-1 to 5-5 are provided with reflective wavelength filters 54-1 to 54-5 for respectively reflecting test signal beams from a station side optical transmitter 1 to the direction of an optical star coupler 3. These wavelength filters 54-1 to 54-5 are set to reflect the mutually different wavelengths at the respective devices 5-1 to 5-5. Therefore, since the wavelength allocated to every subscriber optical transmitter is returned as reflected light, even when any fault is generated at any subscriber side optical fiber line, that optical fiber line can be specified from the station side. Further, when the leaked light of reflected light returned from the devices 5-1 to 5-5 is received by bending subscriber side optical fiber lines 4-1 to 4-5 even at the set temperature, the subscriber transmitter to which the subscriber optical fiber line is connected can be distinguished.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention is used in a passive optical network type optical fiber transmission apparatus for transmitting signal light through an optical star coupler. In particular, it relates to detection of a fault point in an optical fiber line and identification of the optical fiber line.

[0002]

2. Description of the Related Art FIG. 14 is a block diagram showing a conventional example of a passive optical network type optical fiber transmission device.

In a passive optical network type optical fiber transmission device, an N port to 1 port optical star coupler is arranged in the middle of an optical fiber transmission line, and the N port side and the 1 port side are connected via this optical star coupler. Is an optical transmission device that optically transmits a signal to and from. In the example shown in FIG. 14, the station side optical transmission device 1 and a plurality of (five in this example) subscriber optical transmission devices 5-1 to 5-5 are the station side optical fiber lines 2 and 1 to 5 optical lines. It is connected via the star coupler 3 and subscriber optical fiber lines 4-1 to 4-5.

In such an optical fiber transmission device, an OTDR (Optical Time) is used in order to identify the position of the optical fiber line when a failure occurs in the optical fiber line, particularly when a disconnection occurs.
A test method called Domain Reflectmetry) is used. This test method sends a test pulse light from the station side to the subscriber side, receives the backscattered light in the optical fiber at the station side, and determines the time until the backscattered light returns from the station to the optical fiber line. The distance to the obstacle point is determined.

For this OTDR test, in the conventional example device shown in FIG. 14, in addition to the optical transmitter / receiver 11 for signal transmission, wavelength division multiplexing (WDM: WDM:
A Wavelength Division Multiplexing filter 12 is provided. Further, in the subscriber optical transmission devices 5-1 to 5-5,
Each of them has a wavelength division multiplexing filter 51 and a reflection mirror 53 in addition to the optical transceiver 52. The wavelength division multiplexing filters 12 and 51 are for multiplexing and separating the wavelength for signal transmission and the wavelength for OTDR test,
Here, a wavelength of 1.3 μm is used for signal transmission and a wavelength of 1.6 μm is used for the OTDR test.

At the time of the OTDR test, the OTDR measuring device 6 is connected to the optical transmission device 1 on the station side, and its output light is sent to the subscriber side via the wavelength division multiplexing filter 12. The OTDR measuring device 6 also measures the backscattered light from the subscriber side via the wavelength division multiplexing filter 12. Subscriber optical transmission device 5
In -1 to 5-5, the test signal light is separated by the wavelength division multiplexing filter 51, reflected by the reflection mirror 53, and returned to the station side optical transmission device 1 again.

15 and 16 show examples of backscattered light measured by the OTDR measuring device 6. FIG. 15 shows the station side optical fiber line 2 and the subscriber optical fiber lines 4-1 to 4-1.
No failure occurs in any of -5, and FIG. 16 shows a case where any one of the subscriber optical fiber lines 4-1 to 4-5 is disconnected midway. In these figures,
The vertical axis represents the reflected light power, and the horizontal axis represents the distance (distance obtained by the delay time) with reference to an appropriate point in the station.

When there is no fault in the subscriber optical fiber lines 4-1 to 4-5, a step of the reflected light power is observed at the position of the optical star coupler 3, and the subscriber optical transmission devices 5-1 to 5-5.
The reflected light from the reflecting mirror 53 is observed corresponding to each distance of 5. On the other hand, in the case where one of the subscribers has an intermediate disconnection, no backscattered light is observed in the optical fiber from the location of the intermediate disconnection to the subsequent subscribers. Therefore, it can be seen that there is a step in the reflected light power at the disconnection obstacle point, and the disconnection occurs here.

FIG. 17 shows an example of use of the conventional example shown in FIG. In this example, a plurality of station side optical transmission devices 1-1 are installed in the station.
1-n are provided, each of which communicates with a plurality of subscriber optical transmission devices. The plurality of station side optical fiber lines 2-1 to 2-n between the station side optical transmission devices 1-1 to 1-n and the corresponding optical star couplers 3-1 to 3-n are all or plural. , Bundled as an optical fiber cable 21.

In such a configuration, for example, at the time of installation, it is necessary to identify one station side optical fiber line in the optical fiber cable 21 near the ports of the optical star couplers 3-1 to 3-n. There is. At that time, the test signal light of 1.6 μm is transmitted from the station, and each of the station-side optical fiber lines 2-1 to 2-n is bent to receive the leaked light to distinguish it from other optical fiber lines. You can For example, the signal light transmitter 7 generates a test signal light of 1.6 μm, which is transmitted through the station side optical transmission device 1-i (i is 1 to n) to the station side optical fiber line 2
-Send to i. At this time, the star couplers 3-1 to 3-3-
When the station side optical fiber lines 2-1 to 2-n are bent on the n side and the leaked light is received by the optical receiver 8, the station side optical fiber line 2-i can receive the test signal light, and the other station side. Since the leaked light cannot be received by the optical fiber line, the optical fiber line can be identified.

[0011]

However, in the conventional passive optical network type optical fiber transmission device, when there is a failure in the optical fiber line, for example, when the line is broken, a failure of the optical fiber line from the station occurs. Although the distance to the location can be known, it was not possible to identify which subscriber optical transmission device had an optical transmission line fault.

When a plurality of station side optical fiber lines are bundled, the station side optical fiber lines can be individually identified, but the same test signal light is transmitted to the optical fiber lines connected to the same optical star coupler. Since it was distributed, it was not possible to identify optical fiber lines connected to a plurality of subscriber optical transmission devices from the same optical star coupler.

The present invention solves such a problem, and when an optical fiber line connecting an optical star coupler and a subscriber optical transmission device has a failure, the optical fiber line is identified and a test is performed. It is an object of the present invention to provide a passive optical network type optical fiber transmission device capable of identifying the optical fiber line connecting the optical star coupler and each individual subscriber optical transmission device even when installed.

[0014]

The optical fiber transmission device of the present invention is added to a subscriber optical transmission device as a reflection means for reflecting the test signal light from the station side optical transmission device toward the optical star coupler. Each of the optical transmission devices includes a reflection type wavelength filter set to reflect different wavelengths.

[0015]

Since the wavelength assigned to each subscriber optical transmission device returns as reflected light, the optical fiber line can be specified from the station side regardless of which optical fiber line on the subscriber side has a fault. Also, at the time of installation, if the leaked light of the reflected light returning from the subscriber optical transmission device is bent by bending the subscriber optical fiber line, which subscriber optical transmission device is connected to which subscriber optical fiber line? Can be distinguished.

[0016]

1 is a block diagram showing a passive optical network type optical fiber transmission device according to an embodiment of the present invention. Here, a case where N = 5 will be described.

In this optical fiber transmission device, an optical star coupler 3 for optically connecting one port and a plurality of N ports to each other, and one end of the optical star coupler 3 is optically connected to the one port. The station side optical fiber line 2 connected,
N subscriber optical fiber lines 4-1 to 4 whose one ends are optically connected to N ports of the optical star coupler 3.
-5, a station side optical transmission device 1 optically connected to the other end of the station side optical fiber line 2, and a subscriber optical fiber line 4-1.
To 4-5, each of which has N subscriber optical transmission devices 5-1 to 5-5 optically connected to the other end thereof, and the subscriber optical transmission devices 5-1 to 5-5 respectively include The reflection type wavelength filters 54-1 to 54-5 that reflect the test signal light from the station side optical transmission device 1 toward the optical star coupler 3 are provided.

In the station side optical transmission apparatus 1, a wavelength division multiplexing filter 12 is provided in addition to the optical transmitter / receiver 11 for signal transmission, as in the conventional example. Subscriber optical transmission device 5-
In addition to the optical transmitter / receiver 52, a wavelength division multiplexing filter 51 is also provided in each of 1 to 5-5.

The feature of this embodiment is that the reflection type wavelength filters 54-1 to 54-5 reflect different wavelengths from each of the subscriber optical transmission devices 5-1 to 5-5. Is set to. That is, the subscriber optical transmission devices 5-1 to 5-5 have 1.61 μm, 1.
62 μm, 1.63 μm, 1.64 μm, 1.65 μm
Of each wavelength of the reflection type wavelength filter 54-1.
Has a reflection wavelength of 1.61 μm, and the reflection type wavelength filter 54-
The reflection wavelength of No. 2 is 1.62 μm, and similarly, the reflection wavelength of the reflection type wavelength filter 54-5 is set to 1.65 μm.

In this embodiment, at the time of the OTDR test, five OTDR measuring instruments 6- each of which carries out a test at each of the five wavelengths assigned to the subscriber optical transmission devices 5-1 to 5-5.
Using 1 to 6-5, measurement is performed in order. Further, in order to identify the subscriber optical fiber lines 4-1 to 4-5 at the time of installation, the signal optical transmitter 7- that generates five wavelengths assigned to the subscriber optical transmission devices 5-1 to 5-5, respectively. 1 to 7-5, and subscriber optical fiber lines 4-1 to 4 for a certain wavelength
-5 while measuring the leakage light in sequence, or while measuring the leakage light of a certain subscriber optical fiber line, the signal light transmitter 7-
1 to 7-5 are switched in order.

FIG. 2 shows an example of the structure of the reflection type wavelength filter. Here, a configuration in which only the wavelength of 1.63 μm is reflected is shown.

This reflection type wavelength filter is constructed as a grating mirror having a grating on its surface. 1.61 μm, 1.62 μm, 1.63 μm, 1.64 are applied to the light incident on the grating mirror.
If five light wavelength components of μm and 1.64 μm are included, only the light wavelength component of 1.63 μm is reflected to the incident side. The other light wavelength components do not return to the input side but are reflected in different directions.

3 to 7 show examples of OTDR measurement results when no failure has occurred. These measurement results are based on different wavelengths. At each wavelength, backscattered light from the subscriber optical fiber lines 4-1 to 4-5 is superposed and observed, and the reflection type wavelength filter 54- The reflected light from any one of 1 to 54-5 is observed.

8 to 12 show examples of OTDR measurement results when a disconnection fault occurs. In this case, no matter which wavelength is used, the level difference of the backscattered light level is observed as a step at the disconnection obstacle point. The distance from the position of this step to the disconnection failure point can be known. Also,
In the measurement results shown in FIGS. 8, 9, 11 and 12, respectively, the subscriber optical transmission devices 5-1, 5-2, 5-4 and 5 are shown.
One reflected light is observed at the wavelengths assigned to each of −5, but in the measurement result shown in FIG. 10, the reflected light for 1.63 μm assigned to the subscriber optical transmission device 5-3 is not observed. From this, 1.63 μm
It can be seen that the subscriber optical fiber line 4-3 assigned with is broken.

In the same manner, the subscriber optical fiber line 4-1
Even if there is a failure in any of ~ 4-5, the line can be identified and its position can be measured.

FIG. 13 shows an embodiment of a method of identifying a subscriber optical fiber line.

Here, as in the example shown in FIG. 17, a plurality of station side optical transmission devices 1-1 to 1-n are provided in the station,
Each communicates with five subscriber optical transmission devices. Station-side optical fiber line 2 between station-side optical transmission devices 1-1 to 1-n and corresponding optical star couplers 3-1 to 3-n
A plurality of -1 to 2-n or all of them are bundled as the optical fiber cable 21.

In such a structure, at the time of installation, the individual station side optical fiber lines 2-1 to 2-n of the optical fiber cable 21 are identified in the same manner as in the conventional example. Further, in this embodiment, the subscriber optical fiber line can be identified. That is, the subscriber optical fiber line to be identified is bent, the reflected light from the subscriber optical transmission device connected to the subscriber optical fiber line is monitored by the optical receiver 8, and the signal light is transmitted on the station side. 1.61 μm, 1.62 μm, 1.63 μm, 1.64 by transmitters 7-1 to 7-5
Five test signal lights of μm and 1.64 μm are sequentially generated and transmitted to the subscriber side. At this time, by distinguishing at which wavelength the signal light is reflected, it is possible to identify which subscriber optical transmission device the subscriber optical fiber line is connected to.

[0029]

As described above, according to the optical fiber transmission device of the present invention, not only the distance from the station to the fault point can be known even when there is a failure in the subscriber line optical fiber line, but also the subscriber line. At the place where the optical fiber line is installed, it is possible to identify which subscriber optical transmission device the line is connected to. Therefore, there is an effect that the installation work and the maintenance work are facilitated.

[Brief description of drawings]

FIG. 1 is a block configuration diagram showing a passive optical network type optical fiber transmission device according to an embodiment of the present invention.

FIG. 2 is a diagram showing a configuration example of a reflective wavelength filter.

FIG. 3 is a diagram showing an example of an OTDR measurement result by a 1.61 μm test signal light when no failure occurs.

FIG. 4 is a diagram showing an example of an OTDR measurement result by a 1.62 μm test signal light when no failure occurs.

FIG. 5 is a diagram showing an example of OTDR measurement results by a 1.63 μm test signal light when no failure occurs.

FIG. 6 is a diagram showing an example of OTDR measurement results using a 1.64 μm test signal light when no failure has occurred.

FIG. 7 is a diagram showing an example of an OTDR measurement result by a 1.65 μm test signal light when no failure occurs.

FIG. 8 is a diagram showing an example of OTDR measurement results by a 1.61 μm test signal light when there is a disconnection fault.

FIG. 9 is a diagram showing an example of an OTDR measurement result by a 1.62 μm test signal light when there is a disconnection fault.

FIG. 10 is a diagram showing an example of OTDR measurement results using a 1.63 μm test signal light when there is a disconnection fault.

FIG. 11 is a diagram showing an example of an OTDR measurement result by a 1.64 μm test signal light when there is a disconnection fault.

FIG. 12 is a diagram showing an example of an OTDR measurement result by a 1.65 μm test signal light when there is a disconnection fault.

FIG. 13 is a diagram showing an embodiment of a method of identifying a subscriber optical fiber line.

FIG. 14 is a block diagram showing a conventional example of a passive optical network type optical fiber transmission device.

FIG. 15 is a diagram showing an example of OTDR measurement results when no failure has occurred.

FIG. 16 is a diagram showing an example of OTDR measurement results when one subscriber optical fiber line has a disconnection fault.

FIG. 17 is a diagram showing an example of use of the conventional example shown in FIG.

[Explanation of Codes] 1 station side optical transmission device 2 station side optical fiber line 3 optical star coupler 4-1 to 4-5 subscriber optical fiber line 5-1 to 5-5 subscriber optical transmission device 6, 6-1 6-5 OTDR measuring instrument 7, 7-1 to 7-5 Signal light transmitter 11, 52 Optical transmitter / receiver 12, 51 Wavelength division multiplexing filter 53 Reflecting mirror 54-1 to 54-5 Reflective wavelength filter

Claims (3)

[Claims] 1. An optical star coupler for optically connecting one port and a plurality of N ports to each other, and a station-side light whose one end is optically connected to the one port of the optical star coupler. A fiber line, N subscriber optical fiber lines each of which has one end optically connected to the plurality N of ports of the optical star coupler, and an optical connection to the other end of the station side optical fiber line. A station-side optical transmission device and N subscriber optical transmission devices optically connected to the other ends of the subscriber optical fiber lines, respectively. In an optical fiber transmission device provided with a reflection means for reflecting the test signal light from the optical transmission device in the direction of the optical star coupler, the reflection means reflects different wavelengths in each of the subscriber optical transmission devices. Set up An optical fiber transmission device comprising a fixed reflection type wavelength filter. 2. A method for individually testing the N subscriber optical fiber lines in the optical fiber transmission device according to claim 1, wherein the subscriber optical transmission optically connected to the subscriber optical fiber line under test. The test signal light of a wavelength corresponding to the reflected wavelength of the equipment is transmitted from the station side optical transmission equipment, and the reflected light is measured by the station side optical transmission equipment to identify the subscriber optical fiber line under test. A method for testing an optical fiber transmission device, characterized by detecting the fault point. 3. The test method for identifying the N subscriber optical fiber lines in the optical fiber transmission device according to claim 1, wherein the subscriber optical transmission device connected to the subscriber optical fiber line to be identified An optical fiber transmission device characterized in that a test signal light having a wavelength corresponding to a reflection wavelength is transmitted from the station side optical transmission device, and reflected light from the subscriber optical transmission device is detected by the subscriber optical fiber line. Test method.