JP3392310B2 - Optical line test method and optical line test system - Google Patents

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a test method and a test system for an optical fiber line branched by using an optical branch circuit such as an optical coupler and an optical splitter.

[0002]

2. Description of the Related Art FIG. 3 shows an example of an optical fiber line network branched by using an optical branch circuit such as an optical splitter or an optical coupler.
In this case, one optical fiber line 40 is branched into the optical branch lines 41 to 44 by the 1 × 4 optical splitter 10. Reference numeral 30 is a transmission device on the user side.

In the figure, a center device is installed on the left side, and a single-core bidirectional transmission system is adopted in which a signal from the left side to the right side is a down signal and a signal from the right side to the left side is an up signal. Downstream signals are time-division multiplexed (encrypted) by the center device, and the address and capacity of each user-side transmission device are specified at a specific position of this multiplex signal frame, and each transmission device reads its own information. Is able to.

When a failure such as breakage occurs in the optical fiber line, a method for specifying the location is to measure the backscattered light and the reflected waveform by an optical pulse test (hereinafter referred to as OTDR).
And) is often used.

In order to monitor a plurality of optical fiber line networks by an optical pulse test, as shown in FIG.
Terminals 123, 124, -at the final stage of the optical splitter 10
-, And the respective optical branch paths 41, 42, --- connected to them
Between-and directional couplers 61, 62,-, respectively.
It has been proposed to interpose − (Japanese Patent Laid-Open No. 7-27).
944).

As for the optical directional coupler 61, for example, the optical pulse test apparatus 50 is connected to the vacant terminal 611 so that the optical branch 41 can be tested without being affected by the optical branches 42 to 44. Can be monitored. An optical switch 52 selects one branch path from four. Further, the optical communication between the optical fiber line 40 and the optical branch line 41 is performed without any trouble even if the optical directional coupler 61 is interposed. The same applies to the other optical directional couplers 62, 63, ---.

The optical directional couplers 61, 62, --- include:
A 2x2 (4 terminals) optical fiber type coupler (3 dB coupler) that is easy to manufacture is used, and one terminal is not used. That is, in the case of the optical directional coupler 61, the terminal 612 is connected to the terminal 123 of the optical fiber coupler 12,
The optical branch 41 is connected to the terminal 614. The terminal 613 is not used by being subjected to antireflection treatment. Then, the optical monitoring path 71 is connected to the terminal 611 so that the optical pulse test apparatus can be easily connected.

[0008]

As described above, the directional coupler 61 and the like often use a 2 × 2 optical fiber type coupler which is inexpensive and easy to manufacture. Therefore, the terminals 613 and the like are not used. However, recently, in order to make the optical line network more economical, an optical line monitoring system with a lower cost and a simple structure is required.

[0009]

In an optical pulse test method for performing an optical pulse test on an optical line, two or more sets of optical lines are selected from a plurality of optical lines, and each optical line forming a selected set. Is connected to the emission end of the optical coupler, from one of the incident end of the optical coupler, emits a test optical pulse to the set of optical lines, at the user side end of the optical line, and
Optical filters inserted at different distances from the optical coupler
The reflected waves of the test optical pulse from the optical coupler are combined by the optical coupler, so that the pair of optical lines are simultaneously tested for optical pulse.

Further, in an optical pulse test system for performing an optical pulse test on a plurality of optical lines, the optical line test system comprises an optical splitter for branching communication light 1: N, and an incident end at each emission end of the optical splitter. M optical couplers, one of which is connected to each other, and P connected to each emission end of the optical coupler.
Book optical line and the user side end of the optical line , and
For the optical line connected to one optical coupler,
An optical filter is inserted at a position where the distance from the coupler is different, and the other incident end of the optical coupler is connected to the optical pulse testing device side.

[Principle] As an example, only the optical branch paths 41A and 41B are schematically shown in the upper part of each diagram of FIG. 1, and the OTDR waveform of the optical pulse emitted from the optical pulse tester is also shown in the lower part. Immediately before the transmission device 30, which is the end of the optical branch paths 41A and 41B on the user side, the normal optical filter 41 is provided.
A termination cable 412 having 0 is connected by a connector 414. The present invention relates to this optical filter 4
Utilizes 10 strong light reflections. The optical filter 410
Is a dielectric multilayer filter that passes the wavelength of the communication light but reflects the wavelength of the optical pulse test light.

As shown in FIG. 1A, in the case of only the optical branch 41A, the peak A'due to the reflected light appears at a portion corresponding to the optical filter 410 of the OTDR waveform.

Further, as shown in FIG. 1B, the optical branch 41
Even in the case of only B, the peak B ′ appears at a position corresponding to the optical filter 410.

Then, as shown in FIG. 1C, the optical branching path 4
In the case of both 1A and B, the reflected lights are combined, and the combined reflected wave is monitored by an optical pulse tester, but peaks A ′ and B ′ appear at two points corresponding to each optical filter 410. This is a state in which the distance to the transmission device is different and there is no accident.

As shown in FIG. 1D, X of the optical branch 41A
If, for example, a break occurs at a point, a waveform abnormality X ′ appears in a considerable portion of the OTDR waveform, and at the same time, A ′ disappears,
Only B '. With this, the optical branch path 41A in which the failure has occurred can be identified. That is, depending on the distance to the waveform peak,
The optical branch can be specified.

[0016]

BEST MODE FOR CARRYING OUT THE INVENTION As shown in FIG. 2, a splitter 10 splits a multiplexed communication light entering from an entrance end 40 into four. The four output ends of the splitter 10 are connected to the four optical couplers (61, --64) in the next stage. For example, the output end 123 of the splitter 10 is connected to the input end 612 of the optical coupler 61.
Connect to. Next, the output ends of these optical couplers are connected to eight optical lines (41A, 41B --- 44A, 44B), but a set of two optical lines satisfying a predetermined condition is selected from a plurality of optical lines. Then, this one set is connected to the emission end of one optical coupler. The other input end of the optical coupler, for example (61
1) is connected to the optical pulse test apparatus via the optical switch 52. As the optical coupler, for example, a wavelength-independent quartz substrate waveguide type is used.

The present invention can simultaneously monitor not only two lines but also four lines and eight lines.

That is, the number of branches (N) of the optical splitter,
The number of optical couplers (M) and the number of optical fiber lines to be measured (P) are not limited (N, M, P are natural numbers).

[0019]

Since the pulse test of a plurality of branch circuits (optical lines) can be performed simultaneously, the structure of the test line network is simplified.

[Brief description of drawings]

FIG. 1 is an explanatory diagram showing the principle of the present invention.

FIG. 2 is an explanatory diagram of an embodiment of the present invention.

FIG. 3 is an explanatory diagram of a branch line using a splitter.

FIG. 4 is an explanatory diagram of a conventional technique.

[Explanation of symbols]

10 Optical splitter 30 User side transmission device 40 optical fiber line 41, 42, 43, 44 Optical branch 410 Optical filter 412 termination cable 414 connector 50 OTDR (optical pulse tester) 52 Optical switch 61,62,63,64 Directional coupler 71, 72, 73, 74 Optical monitoring path

─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Masato Kuroiwa 3-19-2 Nishishinjuku, Shinjuku-ku, Tokyo Nihon Telegraph and Telephone Corporation (56) Reference JP-A-5-322696 (JP, A) Kaihei 4-19534 (JP, A) JP-A-8-271375 (JP, A) JP-A-7-27944 (JP, A) (58) Fields investigated (Int.Cl. ⁷ , DB name) G01M 11 / 00-11/08

Claims (2)

(57) [Claims] 1. An optical pulse test method for performing an optical pulse test on an optical line, wherein a set of two or more optical lines is selected from a plurality of optical lines, and each of the optical lines constituting the selected set is described above. Connected to the output end of the optical coupler, from one of the input end of the optical coupler, to emit a test optical pulse to the set of optical lines, the user side end of the optical line
And at different distances from the optical coupler.
The reflected wave of the test light pulse from the optical filter ,
A method for testing an optical line, characterized in that an optical pulse test is simultaneously performed on the one set of optical lines by combining the optical lines by the optical coupler. 2. An optical pulse test system for performing an optical pulse test on a plurality of optical lines, the optical line test system comprising:
An optical splitter for branching communication light 1: N, M optical couplers having one incident end connected to each emission end of the optical splitter, and P optical couplers connected to each emission end of the optical coupler. The optical line and the user side end of the optical line , and in the same optical coupler
For the connected optical line, the distance from the optical coupler
An optical line test system having an optical filter inserted at a position where the distance is different , wherein the other of the incident ends of the optical coupler is connected to the optical pulse test apparatus side.