JP2001124658A - Testing system for branch light ray line and testing method for brunch light ray line - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a testing system for branch light ray line or the like capable of ensuring the dynamic range of a test at a low system cost and dis pensing with the temperature regulation of light branching and coupling unit. SOLUTION: A light branching and coupling unit 30 comprises a wave dividing part 31, seven 3dB couplers 321-327, and eight dielectric multilayer film filters F1-F8, which are connected to an SLT through a common light ray line 20 and connected to each ONU through branch light ray lines 401-408, respectively. Each dielectric multiplayer film filter Fn transmits communication lights λS 8-branched and outputted by the 3dB coupler 321-327, and allows at least the test light of the n-th wavelength λn of the eight test lights to be incident thereon to reflect test lights of wavelengths λn or more and transmits the other test lights.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a branch optical line test system for testing each of N (N.gtoreq.2) branch optical lines branched from a common optical line via an optical branch coupler by OTDR, and a branch light beam. Road test method.

[0002]

2. Description of the Related Art In an optical communication system, an optical line for transmitting communication light is an OTDR (optical time domain reflector).
eter). That is, test light having a wavelength different from the wavelength of the communication light is made incident from one side of the optical line, and the intensity of backscattered light generated when the test light propagates through the optical line is detected on the one side. Then, the optical path can be tested based on the detected temporal change of the backscattered light intensity.

On the other hand, one terminal device (SLT: Subscrib
2. Description of the Related Art There is known an optical communication system that simultaneously transmits communication light output from an ER Line Terminal (NER) to N terminal devices (ONUs: Optical Network Units). In this optical communication system, the communication light output from the SLT is transmitted to the optical branching coupler via one common optical line, and the communication light is N-branched by the optical branching coupler, and the branched communication light is transmitted. Light is simultaneously propagated to N ONUs. Even in such an optical communication system, a method has been proposed in which each of the branch optical lines from the optical branch coupler to each of the N ONUs is tested by OTDR.

For example, in a test system disclosed in Japanese Patent Laid-Open Publication No. Hei 6-21888, an N-wave test light for testing N optical branch lines is transmitted from an SLT to an optical branching coupler.
The test light transmitted through the test light line and propagated through each test light line is multiplexed / demultiplexed into the communication light propagated through each branch optical line. In this manner, the N branch optical lines are tested by the OTDR using test lights having different wavelengths.

In the test systems disclosed in JP-A-6-350530 and JP-A-8-110282, communication light and N-wave test light are transmitted from the SLT through one common optical line. The light is transmitted to the branch coupler, and all of the N-wave test light together with the communication light are branched into N in the optical branch coupler, and these are propagated to the respective branch optical lines. Then, an optical component is provided in the middle of each branch optical line extending from the optical branch coupler to the N ONUs, and the N-wave test light propagating through each branch optical line has a wavelength corresponding to the branch optical line. Only the test light is selectively transmitted or reflected by the optical component. In this manner, the OTD is performed using test light of different wavelengths for each of the N branched optical lines.
Test with R.

[0006]

However, the inventor of the present application has found that the above-mentioned conventional example has the following problems. That is, in the test system disclosed in JP-A-6-21888, the cost of the optical communication system will be reduced by using one common optical line for transmitting communication light from the SLT to the optical branching coupler. Despite this, the cost of this test system increases because N test light lines are used to transmit N-wave test light from the SLT to the optical branching coupler.

In the test systems disclosed in JP-A-6-350530 and JP-A-8-110282, all of the N-wave test light is N-branched in the optical branching coupler. The power of the test light of each wave propagating through each of the branch optical lines is reduced. Therefore, the dynamic range of the test is reduced. To increase the dynamic range of the test, it is conceivable to increase the power of the test light transmitted from the SLT, but this increases the cost of the test system.

In order to solve the above problems, Japanese Patent Application Laid-Open No.
It is conceivable to use the integrated optical waveguide circuit disclosed in Japanese Patent No. 98419 in an optical branching coupler. This integrated optical waveguide circuit uses an arrayed waveguide diffraction grating type multiplexer / demultiplexer (AWG: Ar).
The optical power splitter is a combination of a rayed waveguide guide and a star coupler type optical power splitter. The optical power splitter allows the communication light to be branched into N lights, and the AWG can split the N-wave test light. By using this integrated optical waveguide circuit in the optical branching coupler, the communication light and the N-wave test light can be transmitted from the SLT to the optical branching coupler through a common optical line. In this respect, the cost of the test system is reduced. cheap. Also, for each of the N branched optical lines,
The N-branched communication light and the test light having a wavelength corresponding to each of the branched optical lines can be propagated, and the dynamic range of the test can be secured.

Incidentally, the integrated optical waveguide circuit disclosed in Japanese Patent Application Laid-Open No. 7-98419 includes an AWG configuration in which the optical demultiplexing characteristic is sensitive to temperature. It is necessary to keep the optical demultiplexing characteristics constant. The optical branching coupler is often provided outdoors, and in this case, temperature control is indispensable. However, it is difficult for an optical branching coupler provided outdoors to secure a power supply for controlling the temperature. Further, an integrated optical waveguide circuit including an AWG configuration is expensive.

SUMMARY OF THE INVENTION The present invention has been made to solve the above problems, and has a low system cost, can secure a dynamic range of a test, and does not require temperature control of an optical branching coupler. It is an object to provide a road test system and a branch optical line test method.

[0011]

A branch optical line test system according to the present invention is characterized in that each of N (N ≧ 2) branch optical lines branched from a common optical line via an optical branch coupler is connected to each branch line. Different wavelengths λ _n (1 ≦ n ≦
This is a branch optical line test system that performs an OTDR test using N-wave test light of N). The optical branching coupler is (1) a demultiplexing unit that demultiplexes and outputs the communication light and the N-wave test light propagating through the common optical line, and (2) is demultiplexed by the demultiplexing unit. (3) a branching unit that branches the output communication light into N and outputs the communication light; and (3) transmits the communication light branched and output by the branching unit and transmits at least the n-th wavelength of the N-wave test light w. incident test light of lambda _n, the wavelength lambda _n or more test light and other dielectric multilayer film and transmits the other to reflect one of the test optical filter _{F n (1 ≦ n ≦ n} )
And These N dielectric multilayer filters F _n (1 ≦ n ≦ N) output the communication light branched and output by the branching unit to N branch optical lines, and also separate the communication light by the branching unit. The output N-wave test light is demultiplexed, and each test light is output to a corresponding one of the N-branch optical lines, and the N-wave propagated through each of the N-branch optical lines. And combining the backscattered light of the test light and outputting the combined light to the demultiplexing unit.

Also, the method for testing a branched optical line according to the present invention provides a method for testing an N-channel branched from a common optical line via an optical branching coupler.
A branch optical line test method for testing each of the (N ≧ 2) branch optical lines by OTDR using N-wave test light having a wavelength λ _n (1 ≦ n ≦ N) different from each other according to each branch optical line It is. Then, as the optical branching coupler, (1) a demultiplexing unit that demultiplexes and outputs the communication light and the N-wave test light propagating through the common optical line, and (2) is demultiplexed by the demultiplexing unit. And (3) transmitting the communication light that has been branched and output by the branching unit and transmits at least the n-th wavelength λ of the N-wave test light. _n
And a dielectric multilayer filter F _n (1 ≦ n ≦ N) that receives one of the test lights, reflects one of the test light having a wavelength of λ _n or more and the other test light, and transmits the other. Used. These N dielectric multilayer filters F _n (1
≦ n ≦ N), the communication light output after being branched into N by the branching unit is output to the N branched optical lines, and the N-wave test light that is branched and output by the branching unit is branched. Then, each test light is output to a corresponding one of the N branch optical lines, and the backscattered light of the N-wave test light propagating through each of the N branch optical lines is multiplexed and separated. Output to a wave section.

According to the branch optical line test system according to the present invention and the branch optical line test method according to the present invention,
The communication light and the N-wave test light propagate through the common optical line and reach the optical branching coupler. In this optical branching / coupling, the communication light and the N-wave test light are split by the splitter. Then, the communication light demultiplexed by the demultiplexing unit is converted into N by the branching unit.
It is branched and output to the corresponding branch optical of the N dielectric multilayer filter F N book branch optical via one of _n. The test light split by the splitter is N
Demultiplexed by number of the dielectric multilayer film filter F _n, is output to the corresponding branch optical out of the N-branch optical.
Additionally, the backscattered light of N wave test light having propagated through the respective N number of branched optical line is being multiplexed by the N dielectric multilayer filter F _n, outputted through the demultiplexer to the common beam path Is done. Each of the N branched optical lines is tested by the OTDR based on the time change of the backscattered light intensity.

In the branch optical line test system according to the present invention and the branch optical line test method according to the present invention,
The demultiplexing unit further demultiplexes the N-wave test light into two or more bands.
Each of the plurality of dielectric multilayer filters F _n (1 ≦ n ≦ N) reflects or transmits each test light in any band output by being split by the splitter.
In this case, the number of dielectric multilayer filters through which the test light passes in the optical branching coupler is reduced, so that the loss when the test light is split can be reduced.

[0015]

BRIEF DESCRIPTION OF THE DRAWINGS FIG.
The embodiment will be described in detail. Note that in the description of the drawings,
And the same elements are denoted by the same reference numerals, and duplicated descriptions are given.
Omitted. In the following, the number of branches N is assumed to be 8, and communication light
Wavelength of λ_SAnd the wavelength of each of the eight test light beams is λ₁~
λ₈And Communication light wavelength λ_S(For example, up to the 1310 nm band
Or 1550 nm band), the wavelength λ of the test light₁~ Λ₈(Example
For example, a wavelength in the range of 1600 nm to 1700 nm)
Is long, and the magnitude relationship between these wavelengths is λ_S<Λ ₁
<Λ_Two<Λ_Three<Λ_Four<Λ_Five<Λ₆<Λ₇<Λ₈ Described as
You.

(First Embodiment) First, a first embodiment of a branch optical line test system and a branch optical line test method according to the present invention will be described.
An embodiment will be described. FIG. 1 is a schematic configuration diagram of a branch optical line test system according to the first embodiment. The branch optical line test system according to the present embodiment includes one terminal device (SLT) 10, a common optical line 20, and an optical branching coupler 3.
0,8 beam splitter optical line 40 _{1-40 8} and 8 terminating device (ONU) and a 50 ₁ to 50 _8.

The SLT 10 has eight ONUs 50 ₁ to 50 _8.
A communication light having a wavelength λ _S is transmitted to each of the light sources, and a communication light source (not shown) for outputting the communication light is provided. The SLT 10 has eight branch optical lines 4.
As a component for performing testing by OTDR for 0 _{1-40 8} respectively, the control unit 11, a light source 12, a light directional coupler 13 and the light receiving unit 14. Control unit 11
Instructs the light source 12 to output the test light, inputs the electric signal output by the light receiving unit 14 after receiving the backscattered light, and based on the electric signal, the eight branch optical lines 40 _1. 40 ₈ to evaluate each. The light source 12 outputs eight test lights of wavelengths λ _{1 to} λ ₈ according to an instruction from the control unit 11. Optical directional coupler 13 outputs the test light lambda ₁ to [lambda] ₈ of 8 waves output from the light source 12 to the common beam path 20, the common optical path is also output communication light lambda _S from the communication light source Output to 20. The optical directional coupler 13 outputs the backscattered light arriving from the common optical line 20 to the light receiving unit 14. The light receiving unit 14 receives the backscattered light and outputs an electric signal corresponding to the intensity of the backscattered light.

The common optical line 20 has a light directivity of the SLT 10.
Communication light λ output from coupler 13 _SAnd 8 wave tests
Light λ₁~ Λ₈Is propagated to the optical branching coupler 30. Light branch
The coupler 30 transmits the communication light arriving via the common optical line 20.
λ_SAnd 8 test light λ₁~ Λ₈Enter And
The optical branching / coupling device 30 outputs the communication light λ_SBranch into 8
Divided communication light λ_STo eight branch optical lines 40₁~ 40₈So
Output to each. Further, the optical branching / coupling coupler 30 has eight waves.
Test light λ₁~ Λ₈Is divided into each test light λ_nThe branch optical line
40_n(1 ≦ n ≦ 8). Furthermore, optical branching coupling
The device 30 is provided with each branch optical line 40_nTest light λ_n
Are multiplexed and output to the common optical line 20.

The branch optical line 40 _n transmits the communication light λ _S and the test light λ _n output from the optical branch coupler 30 to the ONU 50 _n.
Propagate to The branch optical line 40 _n is propagating toward the light backscattered along the way generated test light lambda _n to the optical branching coupler 30. The ONU 50 _n receives the communication light λ _S propagating through the branch optical line 40 _n . Where O
The NU 50 _n receives the test light λ propagating through the branch optical line 40 _n.
The test light λn is reflected immediately before the receiving unit without receiving _n .

FIG. 2 is a configuration diagram of the optical branch coupler 30 of the branch optical line test system according to the second embodiment. The optical branching / coupling device 30 includes a demultiplexing unit 31 and seven 3 dB couplers 32.
_{1 to} 32 ₇ , and eight cascaded dielectric multilayer filters F _{1 to} F ₈ . The demultiplexing unit 31
The communication light λ _S propagating through the common optical line 20 and the eight test lights λ _{1 to} λ ₈ are demultiplexed and output. If this is realized by a dielectric multilayer filter, the communication The light λ _S is transmitted, and eight test lights λ _{1 to} λ ₈ are reflected.
The branching unit constituted by the _seven 3 dB couplers 32 _{1 to} 32 ₇ is used to transmit the communication light λ that is demultiplexed and output by the demultiplexing unit 31.
_S is branched into eight and output.

[0021] FIG. 3 is a diagram illustrating the transmission and reflection characteristics of the dielectric multilayer film filter F _n. Each dielectric multilayer film filter F _n, as well to transmit 8 branched communication light lambda _S, enters the test light of at least the n-th wavelength lambda _n of the eight waves test light, the wavelength lambda _n or Is reflected and the other test light is transmitted (1 ≦ n ≦ N).

FIG. 4 is a schematic diagram of the dielectric multilayer film filter F _n. As shown in this figure, each dielectric multilayer filter _Fn is fixed on a substrate 400. On the substrate 400, lenses 411 to 414 are fixed, and one ends of the optical fibers 421 to 424 are fixed. The lens 411 is an optical fiber 4
Collimate is incident on the dielectric multilayer film filter F _n test light outputted from the output end 21. Lens 412
Collimates is incident on the dielectric multilayer film filter F _n communication light output from the exit end of the optical fiber 422. Lens 413, is incident on the incident end of the optical fiber 424 collects the communication light reflected by the test light transmitted through the dielectric multilayer film filter F _n and a dielectric multilayer film filter F _n. Further, the lens 414 is provided with a dielectric multilayer filter F.
It condenses the test light reflected by the communication light and a dielectric multilayer film filter F _n transmitted through the _n is incident on the incident end of the optical fiber 424.

In the optical splitter / coupler 30 shown in FIG. 2, the dielectric multilayer filter F ₈ is connected to the first
Of the _eight test lights λ _{1 to} λ 8 arriving at
The ₁ to [lambda] ₇ is transmitted to the second side, the test light lambda ₈ is reflected to the first side, also, the communication light lambda _S from 3dB coupler 32 ₄ reaches the second side to the first side by transmitting, to output communication light lambda _S and the test light lambda ₈ to branch optical line 40 _8. The dielectric multilayer filter F ₇ is the first from the dielectric multilayer filter F ₈ .
Of the _seven test lights λ _{1 to} λ 7 arriving at the side of
The ₁ to [lambda] ₆ is transmitted to the second side, the test light lambda ₇ is reflected to the first side, also, the communication light lambda _S from 3dB coupler 32 ₄ reaches the second side to the first side by transmitting, to output communication light lambda _S and the test light lambda ₇ to the branch optical line 40 _7.

The same applies to the dielectric multilayer filters F _{6 to} F ₂ . The dielectric multilayer filter F ₁ is the test light lambda ₁ that has reached a dielectric multilayer film filter F ₂ on a first side of is reflected to the first side, and the second side of the 3dB coupler 32 ₇ communication light lambda _S reaching the by transmitting to the first side, and outputs the communication light lambda _S and the test light lambda ₁ to the branched optical line 40 _1.

Next, the operation of the branch optical line test system according to the present embodiment will be described, and the branch optical line test method according to the present embodiment will also be described. SL
Communication light lambda _S outputted from the T10, the common light path 20 propagates to reach the optical branching coupler 30, the optical branching coupler 30 8 is branched, eight branch optical line 40 _1-4
0 ₈ are output to each. For example, the communication light lambda _S which is branched output from the common optical line 20 to the branch optical line 40 _1, an optical branching coupler 30, passes through the branching portion 31, a 3dB coupler 32 _1, 32 ₃ and 32 ₇ turn after it is transmitted through the dielectric multilayer film filter F _1, is output to the branch optical line 40 _1. Further, for example, from the common optical line 20 to the branch optical line 40
_The communication light λ _S branched and output to ₇ is transmitted through the demultiplexing unit 31 in the optical branching / coupling coupler 30 and passes through the 3 dB couplers 32 ₁ and 32 _2.
And 32 ₄ through sequentially transmitted through the dielectric multilayer film filter F _7, are output to the branch optical line 40 _7. Then, each of the branched communication light λ _S propagates through the branch optical line 40 _n and turns ON.
Reached U50 _n, are received by ONUs 50 _n.

On the other hand, the eight test light beams λ _{1 to} λ 8 output from the light source 12 of the SLT ₁₀ propagate through the common optical line 20 and reach the optical branching / coupling device 30. It is a wave, the test light lambda _n is output to the branch optical line 40 _n. For example, test light lambda ₁ to be demultiplexed output from the common optical line 20 to the branch optical line 40 _1, an optical branching coupler 30, it is reflected by the demultiplexing unit 31, a dielectric multilayer film filter F ₈
It passes through to F ₂ in the order, is reflected by the dielectric multilayer film filter F _1, is output to the branch optical line 40 _1. Also, for example,
Test light lambda ₇ that is demultiplexed output from the common optical line 20 to the branch optical line 40 ₇ in the optical branching coupler 30, the demultiplexer 31
In the reflected, transmitted through the dielectric multilayer film filter F _8, is reflected by the dielectric multilayer film filter F _7, are output to the branch optical line 40 _7. Then, each of the split test lights λ _n is turned ON.
The light propagates through the branch optical path 40 _n toward U50 _n .

The test light λ _n is transmitted from the optical branching coupler 30 to the ONU
The backscattered light generated while propagating through the branch optical line 40 _n toward 50 _n returns to the SLT 10 via a path opposite to the propagation path of the test light λ _n , and is received by the light receiving unit 14. . Then, the control unit 11 of the SLT 10 obtains the time change of the backscattered light intensity, and tests the branch optical path 40 _n based on this.

As described above, the branched optical line according to the present embodiment
In the test system and the branch optical line test method, the SLT1
0 to the optical coupler 30_SAnd 8 wave tests
Light λ₁~ Λ₈To transmit only one common optical line 20
And the optical branching coupler 30 is manufactured at relatively low cost.
Dielectric filter F which can be made₁~ F₈Configured with
System cost is low. Light branching
Eight test lights λ in the combiner 30₁~ Λ₈Is split and the
Kiiko Line 40_nTest light λ to test_nIs the branch optical line 4
0_nOnly to propagate the dynamic range of the test.
It is possible to secure. Also, the optical branching coupler 30
8 test light λ₁~ Λ₈Transmission characteristics to separate
・ Dielectric multilayer film with relatively small temperature dependence of reflection characteristics
Filter F ₁~ F₈, The optical branching coupler 30
No temperature adjustment is required.

(Second Embodiment) Next, a second embodiment of the branch optical line test system and the branch optical line test method according to the present invention will be described.
An embodiment will be described. The schematic configuration of the branch optical line test system according to the present embodiment is the same as that shown in FIG. FIG. 5 is a configuration diagram of the optical branching coupler 30 of the branching optical line test system according to the second embodiment. Optical branch coupler 30 of the branch optical line test system according to the present embodiment
It is in that it has a place in the demultiplexing unit 31 demultiplexes unit 31 ₁ and 31 _2, different from the case of the first embodiment.

The demultiplexing unit 31 ₁ receives the test light lambda ₁ to [lambda] ₈ common beam path 20 communicating light propagating through the lambda _S and 8 waves, the communication light lambda _S and four-wave of the test light lambda ₁ ~ λ ₄ is transmitted, and the remaining four test lights λ _{5 to} λ ₈ are reflected. Demultiplexing section ₃₁₂ receives the test light lambda ₁ to [lambda] ₄ of the communication light lambda _S and four waves having passed through the branching unit 31 _1, is transmitted through the communication light lambda _S, the four-wave test light lambda ₁ ~ Λ ₄ is reflected. That is, the demultiplexing unit 31 ₁ and 31 ₂ is not a test light lambda ₁ to [lambda] ₈ of the common beam path 20 communicating light propagating through the lambda _S and 8 waves by demultiplexing, further, the eight waves test The light λ _{1 to} λ ₈ are four test light λ
_The light is split into two bands of _{1 to} λ ₄ and the remaining four test lights λ _{5 to} λ ₈ and output. These demultiplexers 31 ₁ and 31
_{2 is} also preferably realized by a dielectric multilayer filter.

The eight dielectric multilayer filters F _{1 to} F ₈ are:
The demultiplexing unit 31 ₁ and 31 ₂ corresponding to the two test light bands demultiplexed are divided into two sets. That is, four dielectric multilayer filter F ₅ to F _8, together with the test light lambda ₅ to [lambda] ₈ 4 waves reflected demultiplexed by the demultiplexing unit 31 _1, the communication light lambda _S and each test light And a branch optical line 40 ₅
And outputs it to the 40 _8. While the remaining four dielectric multilayer filter F ₁ to F ₄ is reflected by the demultiplexer 31 ₂ 4
Test light lambda ₁ to [lambda] ₄ of the wave as well as demultiplexing, and outputs the communication light lambda _S and the test light multiplexed by the branch optical 40 _{1-40 4.}

Next, the branch optical line test system according to this embodiment will be described.
The operation of the system was explained and
A method for testing a branched optical line according to an embodiment will be described. SL
Communication light λ output from T10_SSets the common optical line 20
The light propagates and reaches the optical branching coupler 30, and the optical branching coupler
The optical fiber 40 is divided into eight by the optical fiber 30 and the eight branched optical paths 40₁~ 4
0₈Output to each. For example, the common optical line 20
Branch optical line 40₁Communication light λ branched and output to_SIs the light
In the branch coupler 30, the branching unit 31₁And 31 _TwoIn order
Transmit, 3dB coupler 32₁, 32_ThreeAnd 32₇In order
Through the dielectric multilayer filter F₁Penetrates the rays
Road 40₁Output to Also, for example, the common optical line 20
Branch optical line 40₇Communication light λ branched and output to_SIs the light
In the branching coupler 30, the branching unit 31₁And 31_TwoIn order
3dB coupler 32₁, 32_TwoAnd 32_FourIn order
Through the dielectric multilayer filter F₇Transmitted through the split light
Track 40 ₇Output to And each of the branched communication light
λ_SIs a branch optical line 40_nAnd propagate the ONU50_nReach
And ONU50_nReceived at.

On the other hand, the eight test lights λ _{1 to} λ 8 output from the light source 12 of the SLT ₁₀ propagate through the common optical line 20 and reach the optical branching / coupling coupler 30, where the light is split. It is a wave, the test light lambda _n is output to the branch optical line 40 _n. For example, test light lambda ₁ to be demultiplexed output from the common optical line 20 to the branch optical line 40 _1, an optical branching coupler 30, it passes through the branching portion 31 ₁ is reflected by the demultiplexing unit _312, a dielectric transmitting through the body multilayer film filter F ₄ to F ₂ in the order, is reflected by the dielectric multilayer film filter F _1, is output to the branch optical line 40 _1. Further, for example, from the common optical line 20 to the branch optical line 4
The test light λ ₇ branched and output to O ₇ is reflected by the branching unit 31 ₁ in the optical branching coupler 30, passes through the dielectric multilayer filter F _8, and is reflected by the dielectric multilayer filter F ₇ . It is, is outputted to the branch optical line 40 _7. The demultiplexed test light λ _n is transmitted to the ONU 50 _n by the branch optical line 4.
Propagate 0 _n .

The test light λ _n is transmitted from the optical branching coupler 30 to the ONU
The backscattered light generated while propagating through the branch optical line 40 _n toward 50 _n returns to the SLT 10 via a path opposite to the propagation path of the test light λ _n , and is received by the light receiving unit 14. . Then, the control unit 11 of the SLT 10 obtains the time change of the backscattered light intensity, and tests the branch optical path 40 _n based on this.

The branch optical line test system and the branch optical line test method according to the present embodiment have the same effects as in the first embodiment, and also have the following effects.
That is, the maximum number of the dielectric multilayer filters through which the test light passes in the optical branching coupler 30 is 9 in the first embodiment.
On the other hand, in the present embodiment, it is 6. Therefore, in the present embodiment, it is possible to reduce the loss when the test light is split.

The present invention is not limited to the above embodiment, but can be variously modified. For example, in the above embodiments it was assumed longer towards the wavelength lambda ₁ to [lambda] ₈ of the test light from the wavelength lambda _S of communication light, but towards the wavelength lambda ₁ to [lambda] ₈ of the test light from the wavelength lambda _S of the communication light It may be short. In the latter case, a magnitude relationship lambda ₈ wavelengths lambda ₁ to [lambda] ₈ of the wavelength of communication light lambda _S and the test light _{<λ 7 <λ 6 <λ} 5 <λ 4 <λ 3 <λ 2 <λ 1 <
If λ _S , the configuration and operation are the same as those in the above embodiment. Further, the number N of branches of the communication light in the optical branching coupler is:
In the above embodiment, the number is 8, but the number is not limited to eight.

[0037]

As described above in detail, according to the present invention, the communication light and the N-wave test light propagate through the common optical line and reach the optical branching coupler. In this optical branching / coupling, the communication light and the N-wave test light are split by the splitter. The communication light demultiplexed by the demultiplexing unit is N divided by dividing section, N pieces of dielectric multilayer films corresponding branch optical out of the N-branch optical through one of the filters F _n Output to Further, the test light demultiplexed by the demultiplexing unit are demultiplexed by the N dielectric multilayer filter F _n, is output to the corresponding branch optical out of the N-branch optical. Additionally, the backscattered light of N wave test light having propagated through the respective N number of branched optical line is being multiplexed by the N dielectric multilayer filter F _n, outputted through the demultiplexer to the common beam path Is done. Each of the N branched optical lines is tested by the OTDR based on the time change of the backscattered light intensity.

As described above, according to the present invention, only one common optical line is used for transmitting the communication light and the N-wave test light to the optical branching / coupling device. The system is provided with N dielectric multilayer filters which can be manufactured at low cost, so that the system cost is low. An N-branch test light is demultiplexed in the optical branching coupler, and each test light for testing each of the N branch light lines propagates only through the corresponding branch light line, so that the test dynamic range is secured. Is possible. Further, in order to separate the N-wave test light in the optical branching coupler, a dielectric multilayer filter having relatively small temperature dependence of transmission characteristics and reflection characteristics is used. Is unnecessary.

The demultiplexing unit further demultiplexes the N-wave test light into two or more bands, and the N dielectric multilayer filters F _n (1
≦ n ≦ N) When each of the test lights in any band output after being demultiplexed by the demultiplexing unit is reflected or transmitted, the dielectric multilayer film filter through which the test light passes in the optical branching coupler. , The loss when the test light is split can be reduced.

[Brief description of the drawings]

FIG. 1 is a schematic configuration diagram of a branch optical line test system according to each of a first embodiment and a second embodiment.

FIG. 2 is a configuration diagram of an optical branch coupler of the branch optical line test system according to the first embodiment.

3 is a diagram illustrating the transmission and reflection characteristics of the dielectric multilayer film filter F _n.

4 is a schematic diagram of the dielectric multilayer film filter F _n.

FIG. 5 is a configuration diagram of an optical branch coupler of the branch optical line test system according to the second embodiment.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 10 ... SLT, 11 ... Control part, 12 ... Light source, 13 ... Light directional coupler, 14 ... Light receiving part, 20 ... Common optical line, 30 ...
Optical branching coupler, 31 _1, 31 ₂ ... demultiplexing unit, 32 ₁ ~
32 ₇ … 3 dB coupler, 40 ₁ to 40 ₈ … branch optical line, 5
0 ₁ to 50 ₈ : ONU, F _{1 to} F ₈ : Dielectric multilayer filter.

Claims (4)

[Claims] An N (N ≧ 2) branch optical line branched from a common optical line via an optical branch coupler is converted into a different wavelength λ _n (1 ≦ n ≦) according to each branch optical line. N)
A branch optical line test system for testing by OTDR using the N-wave test light, wherein the optical branching / coupling device separates the communication light propagating through the common optical line and the N-wave test light. A demultiplexing unit that outputs the communication light, and outputs the communication light demultiplexed by the demultiplexing unit.
A branching section for branching and outputting, and to reflect said communication light output is N branched by the branching unit, and the incident test light of at least the n-th wavelength lambda _n of the N-wave of the test beam And a dielectric multilayer filter F _n (1 ≦ n ≦) that reflects one of the test light having the wavelength λ _n or more and the other test light and transmits the other.
N) and N dielectric multilayer filters F _n (1 ≦ n ≦ N)
By the above, the communication light output after being branched into N by the branching unit is output to the N branched optical lines, and the N-wave test light branched and output by the branching unit is branched. Then, each test light is output to a corresponding one of the N branch optical lines, and the backscattered light of the N-wave test light propagating through each of the N branch optical lines is multiplexed. And outputting the result to the branching unit. 2. The demultiplexing unit further outputs the N-wave test light for two more times.
Each of the N dielectric multilayer filters F _n (1 ≦ n ≦ N) splits the test light of any one of the bands output by being split by the splitter. The branched optical line test system according to claim 1, wherein the system is configured to reflect or transmit light. 3. Each of N (N ≧ 2) branch optical lines branched from a common optical line via an optical branching coupler is converted into a different wavelength λ _n (1 ≦ n ≦) according to each branch optical line. N)
A method of testing a branch optical line using an N-wave test light by OTDR, wherein the optical branch coupler separates the communication light propagating through the common optical line and the N-wave test light. A demultiplexing unit that outputs the communication light, and outputs the communication light demultiplexed by the demultiplexing unit.
A branching section for branching and outputting, and to reflect said communication light output is N branched by the branching unit, and the incident test light of at least the n-th wavelength lambda _n of the N-wave of the test beam And a dielectric multilayer filter F _n (1 ≦ n ≦) that reflects one of the test light having the wavelength λ _n or more and the other test light and transmits the other.
N) and a filter having these N dielectric multilayer filters F _n (1 ≦ n ≦ N)
By the above, the communication light output after being branched into N by the branching unit is output to the N branched optical lines, and the N-wave test light branched and output by the branching unit is branched. Then, each test light is output to a corresponding one of the N branch optical lines, and the backscattered light of the N-wave test light propagating through each of the N branch optical lines is multiplexed. And outputting the result to the demultiplexing unit. 4. The N-wave test light is further demultiplexed into two or more bands by the demultiplexing unit, and each of the N dielectric multilayer filters F _n (1 ≦ n ≦ N) is used for the demultiplexing. 4. The method according to claim 3, wherein each test light in any band output by being split by the wave unit is reflected or transmitted. 5.