JPH0227824A - Test method for optical transmission system by segmenting fault - Google Patents

Abstract

PURPOSE:To segment a fault for an optical line and a transmitter simply and quickly by providing a reflecting section of an LD in a sender side equipment with respect to an LED oscillation component to an optical line termination section or a reception side transmitter so as to detect its reflected light. CONSTITUTION:A filter reflecting optical power of an LED oscillation component of the LD 1 in the sender side equipment 22 is formed to the optical line termination section 7 of the receiver side equipment 23 and the reflected light from the optical line termination section 7 is branched partly to a d-port side by an optical coupler 3 and detected by a photodetection module 4 for folded light detection. Then a current varying the current lighting the LD 1 is changed to check the bias current dependency of the reflectance from the optical line 6 thereby identifying the reflected light from the optical line termination section 7 and a Fresnel light from a broken point in the optical line 6. Thus, a fault segmentation between the optical line and the receiver side transmitter is attained remotely from the sender side equipment without manual intervention.

Description

[Detailed Description of the Invention] [Field of Industrial Application] The present invention relates to a method for testing the separation of optical lines and receiving side transmission equipment, and particularly relates to a simple and quick failure test method [Prior art] Failure occurrence in an optical transmission system. In order to dispatch repair supplies efficiently, it is necessary to first isolate and determine where the failure has occurred, since the repair methods and necessary repair tools are different for optical lines and transmission equipment. There is.

Conventionally, in order to isolate failures in optical transmission systems, personnel are dispatched to the transmitting side, the receiving side, and each point on the optical line to investigate how far the light travels to isolate the failure of the optical line and transmission equipment. The six-point method required more personnel and had complicated testing procedures, such as the need to communicate with each location, so there was a problem in that it took time to isolate a failure.

On the other hand, optical pulse testers are used to test optical lines, and are capable of detecting breaks in optical lines and increases in loss. Since the optical pulse test is a one-end measurement, it is conceivable that the failure isolation test can be performed more easily by using an optical pulse tester than the manual isolation method described above.

However, the phase separation resolution of current optical pulse testers is 10 m (dynamic range 20 dB), and it is difficult to accurately detect optical line failures near transmission equipment that often occur in the optical line section of optical transmission systems. Therefore, even if an optical pulse tester is used for a fault isolation test, it is not always possible to distinguish between the optical line and the transmission device in all cases.

In addition, in a wavelength division multiplexing optical transmission system, by preparing a test light source on one side of the transmission equipment and adding a reflection filter for the test light source to the optical multiplexer/demultiplexer of the other transmission equipment, it is possible to A test method for separating optical lines and transmission equipment has been proposed that performs folding tests (Reference [K
.

0kada et al v OFC' 85 e
(See TUQ301985J).

According to this method, it is possible to isolate the failure between the optical line including the optical multiplexer/demultiplexer of the receiving side transmission equipment and the transmission equipment after the optical multiplexer/demultiplexer, but it requires an extra light source for testing the optical line. This was a necessary and economical issue.

[Problems to be Solved by the Invention] As explained above, when a failure occurs in an optical transmission system, conventional means for isolating the failure between the optical line and the receiving side transmission equipment are difficult to solve due to their ease or economic efficiency. There were some implementation issues.

SUMMARY OF THE INVENTION In view of these conventional problems, it is an object of the present invention to provide a test method that can easily and quickly isolate failures in optical lines and transmission equipment using an economical configuration.

[Means to solve the problem]

According to the invention, the above-mentioned object is achieved by the means specified in the claims.

That is, the present invention provides an optical transmission system using an LD as a light source, in which an LED in the oscillation wavelength spectrum of the LD in the transmitting aS device is installed at the end of the optical line or at the receiving side transmission device.
An optical transmission system fault isolation test method in which a beam radiation part for the oscillation component is provided and the reflected light from the reflection part is detected, and in the above test method, the LD in the transmitting side device is operated with a current larger than the threshold current and a current smaller than the threshold current. The failure sign of an optical transmission system that emits light is a test method.

[For production]

The present invention reflects the optical power of the LED oscillation component in the oscillation wavelength spectrum of the LD installed on the transmitting side 111 by a reflection filter provided at the outer end of the optical path or in the receiving side transmission device, and detects the reflected power. This is used to isolate failures between the transmission line and the receiving side transmission equipment.

〔Example〕

The LD mode and the LED mode will be explained below before explaining the embodiments.

FIG. 1 is a diagram showing an example of measurement of the oscillation a-length spectrum of an LD, and the intensity is shown in logarithmic representation.

Figure 11(a) shows the LD mode in which the bias current II is larger than the threshold current It& (in this figure, I@
Figure 1(b) shows the oscillation wavelength spectrum in LED mode (=2.5 Itk) where In is smaller than Itk.
In the case of this figure, 1. = 173 (In)).

As shown in Figure 1, the optical power is the same as the LD! - mode concentrates on the wavelength region where the LD oscillation spectrum line exists (1.3 to 1.32μ theory),
In LED mode, it is widely distributed outside the 1°3-1.32μ plow area.

FIG. 2 is a diagram showing a first embodiment of the fault isolation method according to the present invention in an optical transmission system, in which 1 is an LD monoaire, 2 is a first electric switch, 3 is an optical coupler, and 4
is a light receiving module for loop detection, 5 is an optical code, and 6
7 represents an optical path, 7 represents an optical path termination, and 8 represents a light receiving module.

In FIG. 2, a signal t during normal mode operation such as a communication signal is applied to the A terminal in the transmitting side device 22, and a DC voltage vI+ for making the LD in the LD mozoer 1 emit light is applied to the B terminal. There is. The first electric switch 2 switches between the normal mode and the luminescence test mode.When the first electric switch 2 is connected to the a side, the LD in the LD module 1 is modulated with the LD mode communication signal, etc. , bll, it emits light continuously.

In FIG. 2, a filter that reflects the optical power of the LED oscillation component of the LD is formed at the optical line terminal part 7 of the receiving side device 23, and a part of the optical power received from the transmitting side is returned to the transmitting side. It will be done.

Then, the reflected light from the optical path terminal part 7 is partially branched to the d-boat side by the optical coupler 3, detected by the light-receiving monoaire 4 for folded light detection, and output from the CJI element. Note that the reflection filter is set so as not to reflect the main LD oscillation spectrum lines.

FIG. 3 is a diagram showing an example of the configuration of the optical path termination section 7 in FIG. FIG. 3(b) shows an example of terminating by combining an optical connector made as a filter and a normal optical connector.

In FIG. 3, 9 is an optical connector 7 errule, 10 is an optical 7 fiber wire, 11 is a coating, 12 is a reflection filter for the optical power of the LED oscillation component, 13 is an optical connector formed with a reflection filter, and 14 is a normal It is an optical connector, and 15 is an optical connector receptacle.

The configuration of the optical line termination shown in FIG. 3(b) is necessary to protect the reflection filter 12 when the connection between the transmission line termination W67 and the optical cord 5 in the receiving side transmission equipment in FIG. 2 is frequently changed. This configuration is advantageous in certain cases.

The optical line termination configuration shown in FIG. 3(b) can also be configured by inserting a reflection filter made on a glass substrate or the like between seven common optical connector rules.

Further, it is also possible to provide a configuration in which the reflection filter is not provided at the outer end of the optical path but is provided in the receiving side transmission device.

In this case, the reflection filter may be fabricated by vapor deposition on the end face of the optical fiber in the light receiving module or the lens system, or it may be included in the optical multiplexer/demultiplexer in the wavelength multiplex transmission system.

Since the first embodiment described above has such a configuration, if there is no failure in the optical path 6, the light sent out from the LD module 1 reaches the optical path termination section 7, and the transmitting side device The light-receiving module 4 for detecting folded light can detect the reflected light from the optical path terminal part 7 for the LED oscillation component. On the other hand, if there is a failure in the optical path 6, the light sent out from the LD mozer 1 will not reach the optical path terminal part 7, and the light receiving module 4 for detecting the folded light will not be able to detect the reflected light for the LED oscillation component. As described above, the testing method according to the present invention can isolate failures between the optical line and the receiving transmission device remotely from the transmitting device without human intervention.

On the other hand, as a failure of the optical path 6, a break point where 7-Renel reflection occurs may occur, and in this case, reflected light from the break point is also detected by the transmitting side device.

In the case of reflection from the break point, the 7-Renel reflection reflects the entire oscillation wavelength spectrum, so the reflectance remains unchanged even when the bias current is changed.

On the other hand, the reflection from the optical path terminal part 7 is the reflection of the LED oscillation component from which the LD oscillation wavelength region has been removed, and is 5! Since the wavelength spectrum changes as the bias current changes, the reflectance from the optical path terminal 7 changes as the bias current changes.

Therefore, in the first embodiment, by changing the current that causes the LD to emit light and examining the bias current dependence of the reflectance from the optical path 6 even when 7-Less reflection occurs in the optical path 6, it is possible to Road end f! The reflected light from the IS7 and the 7-Renel reflected light from the break point in the optical path 6 can be distinguished.

That is, if the reflectance from the optical path 6 changes with changes in the bias current of the LD, there is no failure in the optical path 6, but a failure in the transmission device on the receiving side. On the other hand, if the reflected light from the optical path 6 cannot be detected by the receiving device or the reflectance remains unchanged with respect to changes in the bias current of the LD, it is a failure of the optical path. In this manner, the test method according to the present invention allows failures to be isolated between the optical line and the receiving transmission device remotely from the transmitting Il device without human intervention.

#! Figure 14 shows an example of the transmittance characteristics of a reflection filter for an LD showing the oscillation wavelength spectrum characteristics shown in Figure 11, and Figure W&4 (@) shows the characteristics of a long wavelength transmission type (LWPF), and Figure 4 (b) indicates the characteristics of a short wave transmission type (SWPF).

As shown in FIG. 4, the reflection filter is designed to transmit the main oscillation wavelength range (1.3 to 1.32 μm) during communication.

The reflectance of the reflection filter shown in FIG. 4 is, for example, L at the oscillation wavelength range of the LED mode shown in FIG.
Approximately 2.5% for WPF, approximately 27% for 5WPF
It is. On the other hand, in the LD mode oscillation wavelength spectrum, the optical power ratio occupied by the LD oscillation spectrum line is extremely large, so the reflectance of the reflection filter becomes a negligible value. Note that the reflection filter may be a band pass filter (BPF) that transmits the wavelength region during LD mode oscillation.

FIG. 5 is a diagram showing a second embodiment of the present invention, in which 1 is L
D module, 2 is a first electric switch, 5 is an optical cord, 6 is an optical line, 7 is an optical line termination part, 8 is a light receiving module, 16 is a second electric switch, 17 is a load for folded light detection, 18 represents an amplifier.

In FIG. 5, the A terminal in the transmitting side device 24 receives a normal mode signal such as communication, and the B terminal receives the LD mode signal.
A DC voltage V@ is applied to the LD in the cell 1 for a light emission test. The first electric switch 2 switches between the normal mode and the light emission test mode.When the first electric switch 2 is connected to ALL, the LD in the LD module 1 is modulated with a communication signal, etc. When connected to blI, the signal in luminescence test mode changes 1R.
@Reru. The electric switch 16 of ll112 switches the LD in the LD module 1 between the light emitting mode and the light receiving mode in the light emitting test mode.

FIG. 6 shows the state associated with switching of the second electric switch 16! ! ! It is a time chart of transition.

In Figure WS6, when the second electrical switch 16 is connected to eIm, a bias current of 1. flow and emit light.

As in the case of the embodiment ll51, a part of the optical power incident on the optical line 6 in FIG. 5 is returned from the transmission line termination section 7 of the receiving side device 25 to the transmitting side. In the dark, where the optical power sent from the transmitting side returns to the transmitting side again, the electric switch 16 of $2 is connected to the d side, and the LD in the LD sled ale 1 is shifted to a non-biased light receiving mode. By doing this,
The power of the reflected light from the optical line termination section 7 is the LD module 1.
It is converted into a photocurrent I Pk in the opposite direction by the LD which is in the light receiving mode, and after being amplified by the amplifier 18 as the voltage of the folded light detection load 17, the voltage VR is output from the C* child.
is output as Time t2 in FIG. 6 is the round trip time of the optical path.

Since the second embodiment described above has such a configuration, the transmitting side LD can also function as a light receiving module for detecting reflected light.

Therefore, with a simple and economical configuration, it is possible to isolate failures between the optical line and the receiving side transmission equipment remotely from the transmitting side transmission Im without human intervention, as in the first embodiment.

71st! I is the photocurrent Ip with respect to the received light power when the LD having the characteristics shown in Fig. 1 is used in the light receiving mode.
It is a figure showing a change in -. From FIG. 7, the LD is -55
It can be seen that even power can be sufficiently identified by receiving light of dBm. Therefore, the fault isolation test method according to the $2 embodiment of the present invention sets the minimum light receiving power in the light receiving mode of the LD to -55 dBm, and calculates the oscillation wavelength spectrum of 5 WPF (Fig. 4 (b) )) is applicable to an optical line having an optical line loss of 9.7 dB when using the LWPF (FIG. 4(a)), and 4.5 dB when using the LWPF (Fig. 4(a)). Since the minimum light receiving power in the light receiving mode of the LD can be further improved by performing averaging processing, the present fault isolation method can also be applied to optical lines with large optical losses.

FIG. 8 is a diagram showing how to apply the fault isolation method according to the present invention to an optical transmission system that uses two different optical lines for each transmission direction.

In Fig. 8, 1 is LD monoyl, 5 is optical code,
Reference numeral 7 represents an optical line termination, 8 represents a light receiving monorail, 19 represents an optical switch, 20 represents a downward optical line, and 21 represents an upward optical line.

In FIG. 8, the LD module 1 of the center II device 26 is driven in the LED light emission test mode. When the optical switch 19 is in the through state, the LED light from the LD module 1 is input to the downlink optical path 20, and is connected to the downlink optical path 20 and the far side device 27 in the procedure explained in FIGS. 2 and 6. It becomes possible to isolate the failure.

On the other hand, when the optical switch 19 is in the cross state, the LED light from the LD module 1 is input to the upstream optical path 21, and similarly, it is possible to isolate the failure between the upstream optical path 21 and the remote location. becomes.

〔Effect of the invention〕

As explained above, the present invention performs a folding test of an optical line using the reflected light from the end of the optical line with respect to the LED oscillation component in the oscillation wavelength spectrum of the transmitting side LD. It has the advantage of being able to carry out isolation tests remotely and accurately.

Furthermore, since it is possible to use a communication LD as the transmitting LD and as a light receiving section for reflected light, the optical transmission system can have an economical and simple configuration that does not require additional optical components such as a light source for separation. It has the advantage of being able to perform separate tests on optical lines and transmission equipment remotely.

[Brief explanation of the drawing]

Fig. 1 is a diagram showing an example of measurement of the oscillation wavelength spectrum of an LD, Fig. 2 is a diagram showing an example of mi of the fault isolation method according to the present invention, and Fig. 3 is a diagram showing an example of the configuration of the optical path termination section. figure,
Fig. 4 is a diagram showing an example of the transmittance characteristic of a reflection filter, Fig. 5 is a diagram showing an example of the fault isolation method of tA2 according to the present invention, and Fig. 6 is a diagram showing an example of the transmittance characteristic of a reflection filter. Condition fi! Transfer time chart, Figure 7 is LD
Figure 8 shows the application of the fault isolation method according to the present invention to an optical transmission system that uses two different optical lines for each transmission direction. FIG. 1...LD module, 2.
...First electrical switch, 3...
... Optical coupler, 4 ... Light receiving module for folded light detection, 5 ......
Optical cord, 6... Optical line, 7...
・・・・Optical line terminal layer, 8 ・・・・Light receiving monorail, 9 ・・・Optical connector 7x rule,
10...Hikari 7 fiber wire, 11
・・・・・・Coating, 12 ・°. ...Reflection coefficient k for the optical power of the LED oscillation component
l-13... Optical connector with reflection filter 12 formed therein, 14... Ordinary optical connector, 15... Optical connector receptacle, 16...... Number 2 electric switch, 17...Prayer return light detection load, 18...Amplifier, 19.
・・・・・・Light switch, 20 ・・・・・・
Optical line for downlink, 21... Optical line for uplink, 22 24---...Transmission side! [, 23 receiving side device, center II device, far side iut

Claims (1)

[Claims] 1. In an optical transmission system using an LD as a light source, the LD in the transmitting device is connected to the optical line termination or the receiving transmission device.
1. A failure isolation test method for an optical transmission system, comprising: providing a reflecting section for an LED oscillation component in an oscillation wavelength spectrum; and detecting reflected light from the reflecting section. 2. The optical transmission system fault isolation test method according to claim 1, wherein the LD in the transmitting side device is caused to emit light with a current larger than a threshold current and a current smaller than the threshold current.