JPH04116441A - Testing method of optical branch path - Google Patents

Abstract

PURPOSE:To enable measurement without lowering the transmission characteristic and requiring many photosignals of different wavelengths by a method wherein a photosignal for testing purpose is switched by an optical switch, and supplied to only one of a plurality of branching optical fibers at the same time. CONSTITUTION:A photosignal H for testing purpose from an optical pulse tester 1a reaches an optical switch 12 through a transmission optical fiber 11. The connection between the fiber 11 and an optical fiber wiring FB1-FB3 is switched so that the photosignal H is supplied to only one of the branching optical fibers 41-43 at the same time. A transmission photosignal S is guided from a transmission device 10 to the branching optical fiber (for example, 4-1) to which the photosignal H is supplied. As a result, backward scattering lights are generated from the photosignals H, S. However, only a backward scattering light B of the photosignal H is detected by the tester 1a through a wavelength selective optical multiplexer/demultiplexer filter 13 (for example 13-1), and the transmission characteristic of the optical fiber 4 (e.g., 4-1) is measured. Accordingly, the transmission characteristic of each branching optical fiber 41-43 can be measured without attenuation of the photosignal H while the favorable dynamic range is maintained.

Description

DETAILED DESCRIPTION OF THE INVENTION (Field of Industrial Application) The present invention relates to a method for testing a branched optical line, which allows the transmission characteristics of each optical fiber constituting the branched optical line to be individually measured.

(Prior art) In recent years, a branching optical line has been proposed in the optical line of a subscriber system, in which one main optical fiber is connected to multiple branching optical fibers via an optical multiplexer/demultiplexer, and has not been put into practical use. It is served to.

Normally, in such a branch optical line, the terminals of branching optical fibers branched into a plurality of branches are connected to the subscriber's home. Therefore, when testing the transmission characteristics of such optical lines, it is necessary to use test equipment installed only at the terminal on the main optical fiber side before branching, such as optical pulse testing, installed in the telecommunications company's office building. It is desirable to be able to perform the test using a device, etc.

However, since the optical fiber is branched in the middle, if the test was carried out using the normal method, the test optical signal transmitted from the station would also be split and supplied to multiple optical fibers. Therefore, it is not possible to individually measure the transmission characteristics of a plurality of branching optical fibers.

In view of these circumstances, a measurement method as shown in Fig. 2 has been proposed (reference document: Japanese Patent Laid-Open No. 2-141.
Publication No. 641).

In FIG. 2, reference numeral 1 denotes an optical pulse tester, each having a different wavelength λ1. λ2. λ3 test optical signal h11 h2
r h3... is sent. 2 is one unbranched main optical fiber of the branch optical line, 3 is an optical multiplexer/demultiplexer,
4-1, 4-2, 4-3 are branching optical fibers of the branching optical line, which connect the main optical fiber 2 and the branching optical fibers 4-1, 4-2, 4-3 via the optical demultiplexer 3. is connected. Optical filters 5-1, 5-2, and 5-3 are disposed on the branching optical fibers 4-1, 4-2, and 4-3, respectively.

The optical filter 5-1 transmits only the test optical signal h1 having the wavelength λ1 and the transmission optical signal having the wavelength (λS). Further, the optical filter 5-2 transmits only the test optical signal h2 having the wavelength λ2 and the transmission optical signal having a predetermined wavelength (λ,), and the optical filter 5-3 transmits the test optical signal h3 having the wavelength λ3 and the transmission optical signal h2 having the wavelength λ3. Only a transmission optical signal of a predetermined wavelength (λ3) is transmitted.

In such a configuration, the test optical signal 6' h 1 + h 2 + 1 with different wavelengths is
13 into the main optical fiber 2, and the combined light is split by the optical multiplexer/demultiplexer 3 and guided to each branching optical fiber.
By supplying only one test optical signal 111 + h2 + h3 to each of the branching optical fibers 4-1, 4-2, and 4-3 using the optical filter 5 (H5-2H53), Yomitsushin-shishih,,h
2. h3 wavelength and branching optical fiber 4-J.

4-2 and 4-3 are associated with each other, and thereby each branching optical fiber 4. −． L, 4-2, 4-3
The transmission characteristics of each are measured individually.

(Problem to be Solved by the Invention) However, in the above conventional method, after the total number of test optical signals h+h2+h3 is divided into a plurality of parts by the optical multiplexer/demultiplexer 3, each Since it is supplied to the optical fiber,
Test optical signal h1 by division. b. The attenuation of 2h3 is significant, the dynamic range of the measurement system is greatly reduced, and optical lines with a large number of branches are not suitable for practical use.

Furthermore, in the above two methods, test optical signals with different wavelengths equal to the number of branched optical fibers are used + h21
h3 is required.

Also, depending on the purpose of the test, you may want to measure one optical fiber at multiple wavelengths, but in this case, you will need as many test optical signals as the product of the number of wavelengths to be measured and the number of branches. .

When the number of branches increases, it becomes necessary to install a huge number of lasers with different oscillation wavelengths in the test equipment. Further, when testing is performed without interrupting the transmission of the optical transmission signal, there is a drawback that the wavelength band that can be used as the optical transmission signal is significantly reduced.

The present invention was developed in view of the above circumstances, and its purpose is to improve the transmission characteristics of each optical fiber constituting a branched optical line without reducing the dynamic range of the measurement system due to branching. Another object of the present invention is to provide a method for testing a branched optical line that can be measured without requiring test optical signals of many different wavelengths.

(Means for Solving the Problem) In order to achieve the object stated in -1-, claim (1) provides the following:
Each branch optical line consists of a main optical fiber, a means having at least an optical demultiplexing function or an optical multiplexing function connected to the main optical fiber, and a plurality of branching optical fibers connected to the means. In a test method for branched optical lines in which transmission characteristics are measured by propagating a test optical signal through an optical fiber, the test optical signal is switched using an optical switch.
At the same time, the test optical signal was supplied to only one of the plurality of branching optical fibers.

Further, in claim (2), in the method for testing a branch optical line according to claim (1), the test optical signal is propagated through the main optical fiber through which the transmission optical signal is propagated; The test optical signal is transmitted in the vicinity of the optical fiber connection part,
It was taken out from the main optical fiber and supplied to the optical switch.

(Function) According to claim (1), the - test optical signal is subjected to a switching action by the optical switch. As a result, at the same time, the test optical signal is sent to one of the multiple branching optical fibers.
Only supplied to optical fiber.

In this way, the transmission characteristics of a plurality of optical fibers are individually measured.

According to claim (2), the test optical signal is propagated through the main optical fiber through which the transmission optical signal is propagated. The test optical signal propagating through the main optical fiber is taken out from the main optical fiber near the area where optical demultiplexing or optical multiplexing means, etc. are installed.
Supplied to the optical switch.

The test optical signal supplied to the optical switch is subjected to a switching action by the optical switch. As a result, the test signal is supplied to only one of the plurality of branching optical fibers at the same time.

In this way, the transmission characteristics of a plurality of optical fibers are individually measured.

(Embodiment) FIG. 1 is a block diagram showing a first embodiment of a test device to which the branched optical line testing method according to the present invention is applied, and the same components as in FIG. 2 showing the conventional example are as follows. Represented by the same symbol.

That is, 1a is an optical pulse tester which transmits a test optical signal H having a predetermined wavelength λ5. 2 is one unbranched main optical fiber of the branch optical line, 3 is an optical multiplexer/demultiplexer, 4-1
, 4-2, and 4-3 are branching optical fibers of the branching optical line, and the main optical fiber 2 and the branching optical fibers 4-1, 4-2, and 4-3 are connected via the optical multiplexer/demultiplexer 3. ing.

Reference numeral 10 denotes a transmission device that sends out a transmission optical signal S to the main optical fiber 2. Reference numeral 11 denotes a transmission optical fiber, and like the transmission device 10, the light was emitted from a remote optical pulse tester 1a. The test optical signal H with a predetermined wavelength λ□ is transmitted to the area near the branch point of the branch optical line, that is, to the vicinity where the optical multiplexer/demultiplexer 3 is installed, and the branch optical fibers 4-1, 4-2, 4-
8 is transmitted to the optical pulse tester 1a.

12 is an optical switch that connects a transmission optical fiber 11 and three optical fiber wirings FB1. FB2. Switch the connection with FB3. This switching technique is appropriately selected and applied, such as a manual switching technique or a sequential automatic switching technique at predetermined time intervals.

13-1.18-2.13-3 is a wavelength selective optical multiplexer/demultiplexer, which connects branching optical fibers 4-1, 4-2, and 4, respectively.
-3.

The optical multiplexer/demultiplexer 13-1 multiplexes the test optical signal H with the wavelength λ□ that has propagated through the optical fiber wiring FB1 and the transmission optical signal S with the wavelength λ5 that has passed through the optical multiplexer/demultiplexer 3 and outputs it for branching. While guiding the wave to the optical fiber 4-1, the branching optical fiber 4-
The light having a wavelength λ5 (transmission optical signal) propagated through the optical fiber 1 is guided to the optical multiplexer/demultiplexer 3, and the light having a wavelength λ1° (backscattered light) is guided to the optical fiber wiring FB□.

The optical multiplexer/demultiplexer 13-2 multiplexes the test optical signal H of wavelength λ1 propagated through the optical fiber wiring FB2 and the transmission optical signal S of wavelength λS via the optical multiplexer/demultiplexer 3, and outputs the signal for branching. While guiding the wave to the optical fiber 4-2, the branching optical fiber 4
-2, the light with the wavelength λ5 (transmission optical signal) is guided to the optical multiplexer/demultiplexer 3, and the light with the wavelength λ9 (backscattered light) is guided to the optical fiber wiring FB2.

Furthermore, the optical multiplexer/demultiplexer 13-3 includes an optical fiber wiring FB3.
The test optical signal H with the wavelength λ The light with the wavelength λS (transmission optical signal) propagated through the optical fiber 4-3 is guided to the optical multiplexer/demultiplexer 3, and the light with the wavelength λ (backscattered light) is guided to the optical fiber wiring FB3.

Next, a method for testing the branching optical fiber having the above configuration will be explained.

First, a test optical signal H is guided from the optical pulse tester 1a to the transmission optical fiber 11. Thereby, the test optical signal H reaches the optical switch 12 after propagating through the transmission optical fiber 11.

Here, the optical switch 12 causes the arriving test optical signal H to connect to the branching optical fibers 4-1 and 4-2 at the same time.
, 4-3, the transmission optical fiber 11 and each optical fiber wiring FB
Engineering, FB2. Switch the connection with FB3.

With this connection switching, for example, optical fiber wiring FB
, the test optical signal H is guided to the branching optical fiber 4-1 via a wavelength-selective optical multiplexer/demultiplexer.

In addition, the optical signal S for transmission that is emitted from the transmission device 10 and passed through the main optical fiber 2, the optical multiplexer/demultiplexer 3, and the wavelength selective optical multiplexer/demultiplexer 13-1 is guided to the branching optical fiber 4-1. be done.

As a result, backscattering based on the test optical signal H and the transmission optical signal S occurs in the branching optical fiber 4-1.

Of these backscattered lights, only the backscattered light B of the test optical signal H is transmitted again to the wavelength selective multiplexer/demultiplexer 13-1, the optical fiber wiring FB1, the optical switch 12, and the transmission optical fiber 1]. The light is received by the optical pulse tester 1a through the optical pulse tester 1a.

Based on this received backscattered light B, a branching optical fiber 4 is
-1 measurement of transmission characteristics.

Similarly, the transmission characteristics of the branching optical fibers 4-2 and 4-3 are also measured.

As explained above, according to the first embodiment, the test optical signal H is sent to the required branching optical fibers 4-1 and 4-2 by the optical switch 12 at specified time intervals.

4-3, there is no attenuation of the test optical signal due to splitting as in the conventional case, and the test optical signal is connected to the branch optical fibers 4-1 and 4 of the branch optical line while maintaining a good dynamic range.
．． -2, 4-3] transmission characteristics can be measured.

In addition, as for the number of test optical signals, it is not necessary to prepare as many as the product of the number of wavelengths to be tested and the number of branches, as in the past, but it is only necessary to prepare as many as the number of wavelengths to be measured regardless of the number of branches. Commonly, the configuration of the test equipment]

complication can be avoided.

FIG. 3 is a configuration diagram showing a second embodiment of a testing apparatus to which the branched optical line testing method according to the present invention is applied.

This second embodiment is different from the first embodiment described above in that the optical fiber 11 for transmitting the test optical signal H is omitted, and the test optical signal H is transmitted together with the transmission optical signal S through the main optical fiber 2. to the area near the branch point of the branch optical line, that is, to the vicinity where the optical multiplexer/demultiplexer 3 is installed, and
The backscattered light B is also guided to the optical pulse tester 1a via the main optical fiber 2.

For this reason, wavelength-selective optical multiplexers/demultiplexers 13-4 and 13-5 having the same functions as the wavelength-selective optical multiplexers/demultiplexers 13-1 to 13-3 are provided at both ends of the main optical fiber 2 to transmit Device 1
Transmission optical signal S by 0 and optical pulse tester] The test optical signal H by a is multiplexed by the wavelength-selective optical multiplexer/demultiplexer 13-4 and propagated through the main optical fiber 2. The wavelength-selective optical multiplexer/demultiplexer 13-5 immediately before splits the transmission optical signal S and the test optical signal H, and the divided transmission optical signal S is sent to the optical multiplexer/demultiplexer 3 and then the test optical signal H. The optical switch 1.
It is configured to supply to 2. Also, FB in Figure 3
, ~FB6 are optical fiber wirings.

In addition to the effects of the first embodiment, the second embodiment has advantages such as eliminating the need for complicated work such as laying a long transmission optical fiber.

Note that the above-described first and second embodiments can be easily applied to a branched optical line in which the line is branched in multiple stages. Specifically, a method similar to the method shown in the embodiment may be applied to the second and subsequent branch portions.

(Effect of the invention) As explained above, according to claim (1) or (2), the transmission characteristics of each optical fiber of the branch optical line are
without compromising the dynamic range of the measurement system, and
Measurement can be performed only with a measuring device installed at the terminal on the main optical fiber side.

Moreover, regardless of the number of branches, it is sufficient to prepare as many test wavelengths as the number of wavelengths to be measured, and it is possible to prevent the test apparatus from becoming complicated. Furthermore, even if the test is performed without interrupting the transmission of the optical transmission signal, the wavelength band that can be used for the optical transmission signal will not be significantly reduced.

Therefore, the present invention is an extremely effective method for testing transmission lines when a large number of optical lines are introduced into subscriber systems, which is expected to occur in the future, and can contribute to stable maintenance and operation of communication networks. .

[Brief explanation of drawings]

FIG. 1 is a configuration diagram showing a first embodiment of a testing device to which the branched optical line testing method according to the present invention is applied, FIG. 2 is an explanatory diagram of a conventional example, and FIG. 3 is a branched optical line according to the present invention. FIG. 2 is a configuration diagram showing a second embodiment of a test device to which the road test method is applied. In the figure, 1a... Optical pulse tester, 2... Main optical fiber, 3... Optical multiplexer/demultiplexer, 4-1, 4-2, 4-3
... Optical fiber for branching, 10... Transmission device, 11.
...Transmission optical fiber, 12...Optical switch, 13-
1 to 13-5...Wavelength selective optical multiplexer/demultiplexer.

Claims (2)

[Claims] (1) A branch consisting of one main optical fiber, a means having at least an optical demultiplexing function or an optical multiplexing function connected to the main optical fiber, and a plurality of branching optical fibers connected to the means In the test method for branched optical lines, in which the transmission characteristics are measured by propagating test optical signals to each optical fiber in the optical line, the test optical signals are switched by an optical switch, and the test optical signals are not transmitted at the same time. A method for testing a branching optical line, characterized in that the branching optical line is supplied to only one of the plurality of branching optical fibers. (2) In the branch optical line testing method according to claim (1), the test optical signal is propagated through the main optical fiber through which the transmission optical signal is propagated, and a region near the main optical fiber connection part of the means is provided. A method for testing a branch optical line, characterized in that the test optical signal is extracted from the main optical fiber and supplied to the optical switch.