JPH0743573A - Installing method for small optical cable - Google Patents

Abstract

PURPOSE:To provide an installing method for a small optical cable by which the required number of expensive optical measuring instruments can be reduced, and work can be reduced, and the management of a remaining optical cable, a wiring network, the optical cable length of a draw line can be managed by a base station uniquely. CONSTITUTION:The small optical cable 10 wound across a drum 11 is retained by a retaining part 13, and an upper port is joined with the optical fiber of an aerial cable 7a with an aerial closure 6b (figure A). The small optical cable 7 is supplied from an optical cable housing part 11, and it is installed by extending (figure B). The cable is retained at the retaining part 14 of a draw destination 9, and required excessive length 15 is secured (figure C), and it is cut at a cutting point 16. During that time, measurement is continued by an OTDR method on a base station side. When bending affected on transmission loss, etc., occurs while installation work is being performed, the local step of an OTDR waveform due to the increment of loss occurs, and it can be detected, and also, cut length can be measured.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method of laying an optical cable used for optical communication.

[0002]

2. Description of the Related Art The conventional use of optical cables including optical fibers is usually used mainly for trunk lines such as relay systems of telecommunications carriers, and specialists lay down large optical cables with a large number of cores. For each installation, light was passed between both ends of the optical cable to check the integrity of the optical cable.

As another method for confirming the soundness of an optical cable, "Point of optical fiber technology 200" (published by the Telecommunications Association) p. As described in H.295, a method using an optical pulse tester is known. This method
It is possible to investigate the increase point of loss by making pulsed light incident on the optical fiber of the optical cable and measuring the backscattered light.
This is called the TDR method. Using this method, measurements have been performed for each of the installed large optical cables.

However, with the informationization of society in recent years, the end of the optical fiber communication network has greatly expanded to enterprises, and has come to be used in general households as well.
It has become necessary to lay a large number of small optical cables with a small number of fibers, such as withdrawing them to each customer.

On the other hand, since such a small-sized optical cable is small and lightweight, it is excellent in portability and various laying methods have been adopted.

In order to cope with such an increase in demand, a method of using the OTDR method for measuring backscattered light is used as a method for inspecting a failure of an optical communication network during a service period, "The 1992 Autumn Meeting of the Institute of Electronics, Information and Communication Engineers". Paper number B-642 "and the like.

However, if an attempt is made to measure a large amount of optical fibers by using the OTDR method, a large amount of optical devices for inspection, that is, a light source and a light receiver are required, and the inspection work is performed at each installation point. Therefore, there is a problem that it takes a long time to work and a large number of workers having a technique for performing such optical measurement are required.

Further, according to this method, even if the optical cable is broken during installation, is struck by the vehicle and breaks, or the optical transmission loss is locally increased due to the bending of a small radius, There is a problem in that waste is laid because the installation is advanced and the obstacle is not found until after the entire length of the optical cable has been laid. If the presence of obstacles is found after installation, adjust the installed optical cable,
It is necessary to perform work such as changing the route, which is very troublesome.

Further, in the recent small-sized optical cable, for example, the wiring in a building is about 100 m, and the cable from a telephone pole to each house is about 30 to 100 m, and the installation length is short. For this reason, in order to reduce the volume during transportation,
A laying method is used in which a long optical cable having a series of lengths is used, laying is performed from its upper opening, and the optical cable is cut when a required length is paid out. This laying method has a problem that the pay-out length of the optical cable must always be measured during paying out.

[0010]

SUMMARY OF THE INVENTION The present invention has been made in view of the above-mentioned circumstances, and it is possible to reduce the number of expensive optical measuring instruments required and to reduce the work, and to manage the residual line of the optical cable and the wiring network, It is an object of the present invention to provide a method for laying a small optical cable in which the length of the optical cable of the drop line can be centrally managed by the base station.

[0011]

According to a first aspect of the present invention, there is provided a method for laying a small-sized optical cable containing an optical fiber, wherein the optical fiber at the upper end of the small-sized optical cable housed in the optical-cable storing section. Is connected to the optical fiber in the optical cable of the base station side of the optical communication network, the light is incident on the optical cable from the base station side, the light is sent to the small optical cable, the backscattered light is measured, and the small optical cable It is characterized in that the condition of the optical fiber by the feeding and laying of the optical fiber is measured.

According to a second aspect of the present invention, in the method for laying a small optical cable containing two or more optical fibers, the two optical fibers are connected at the lower end of the small optical cable housed in the optical cable housing. Connecting the two optical fibers of the upper end of the small optical cable to the two optical fibers of the optical cable on the base station side of the optical communication network,
One of the two optical fibers in the optical cable from the base station side
It is characterized in that light is incident on one side and the amount of light emitted from the other side is measured to measure the condition of the optical fiber due to the feeding and laying of the small optical cable.

According to a third aspect of the present invention, in the method for laying a small optical cable according to the first or second aspect, a small-length optical cable having a continuous length is used, and the condition of the optical fiber is measured by feeding and laying the optical cable. Then, the small optical cable is cut, and in the invention according to claim 4, in the method for laying the small optical cable according to claim 1 or 2, during the laying of the small optical cable. The present invention is characterized in that laying and feeding are performed while measuring the presence or absence of abnormality during laying.

[0014]

According to the present invention, since the soundness of the optical cable can be measured by a small number of optical measuring instruments installed in the base station of the optical communication network, the number of optical devices can be reduced. Further, since the light measurement work is mainly performed in the base station, it can be automated, does not require a skilled worker, and can shorten the work time.

Furthermore, since the soundness of the optical cable laid during or immediately after the laying can be discriminated, the trouble point can be easily repaired. Particularly, when the trouble occurs, the laying of the optical cable is stopped or the trouble is solved. It can be removed. In addition, by measuring the backscattered light, the length of the laid optical cable can be measured, the used length of the small optical cable can be measured and the remaining length can be managed, and the length of the optical communication network can be managed.

[0016]

EXAMPLE FIG. 4 is a schematic view of an example of an optical wiring system. In the figure, 1 is a base station, 2 is an OTDR measuring device, 3a, 3b,
3c is a connection closure, 4a, 4b and 4c are wiring cables, 5a and 5b are electric poles, 6a and 6b are aerial closures,
7a and 7b are overhead optical cables, 8 is an optical drop line, and 9
Is the debit destination. From the base station 1, for example, through the wiring cables 4a, 4b, 4c, etc., which are connected by the connection closures 3a, 3b, 3c, etc. arranged underground, they are connected to the aerial closure 6a installed on the telephone pole 5a.
From the aerial closure 6a, the aerial optical cables 7a and 7b
Then, the electric poles 5b and so on are sequentially wired in the area where the subscriber exists. The aerial optical cables 7a, 7b and the like are wired by an appropriate method such as being supported by a support wire stretched between electric poles, but are connected to each other by an aerial closure 6b in an appropriate section, for example, in an electric pole 5b. . At the drop-off point, for example, in the overhead closure 6b, the optical fiber in the overhead optical cable 7a is connected to the two optical fibers in the optical drop line 8 which is one type of small optical cable, and is guided to the drop-off destination 9.

FIG. 1 is an explanatory view of an example of a method of laying a light drop line, and the portions corresponding to those in FIG. 4 are designated by the same reference numerals. In the figure, 5b is a utility pole, 6b is an aerial closure, 7
Reference numerals a and 7b are overhead optical cables, 9 is a drop destination, 10 is a small optical cable, 11 is an optical cable storage portion, 12 is a connector, 13 and 14 are detention portions, 15 is an extra length, and 16 is a cutting point.

FIG. 1A shows the first stage. First, the small-sized optical cable 10 is installed at an appropriate position in the detention section 1 of the electric pole 5b.
3, the upper port is guided to the aerial closure 6b, and the optical fiber therein is joined to the optical fiber in the aerial optical cable 7a by the connector 12. In this example, the length of the prepared small-sized optical cable 10 is 600 m including the length accommodated in the optical cable storage unit 11. In this example, a small drum is used as the optical cable housing 11.

FIG. 1B shows the second stage. Pull out the small optical cable 10 from the optical cable storage unit 11,
We will lay wires.

FIG. 1C shows the third stage. The small optical cable 10 is retained in the retracting portion 14 at an appropriate place such as the house of the destination 9 and the necessary extra length 1 for indoor retracting or the like
An appropriate length is pulled out from the optical cable storage 11 so as to secure the number 5.

FIG. 1D shows the fourth stage. When the required extra length is secured, the small-sized optical cable 10 is cut at the cutting point 16 on the optical cable housing 11 side.

In this way, the work of laying down the drop line using the small-sized optical cable is carried out. The operation and effect of the present invention for measuring the characteristics of the optical cable will be described by taking this drawing-down work as an example.

During the above-mentioned laying work, the OTDR measuring device 2 measures at the base station 1 continuously, at predetermined time intervals, or at an appropriate time according to the progress of the work.

FIG. 3 is an explanatory diagram of general measurement results by the OTDR method. The horizontal axis is the propagation time, which is a value corresponding to the distance. The vertical axis represents the received light power, which is usually displayed in logarithm. Point A is Fresnel reflected light. Up to the subsequent point B, the received light power is gradually reduced, but this inclined portion is due to the backscattered light of Rayleigh scattering, and the inclination corresponds to the optical loss. At point B, the slope is steep, but this portion is the connection portion, and the steep decrease corresponds to the connection loss. Up to the subsequent point C, there is an inclined portion due to the backscattered light of the above Rayleigh scattering. Point C is the cut end, and the Fresnel reflected light is measured. The distance corresponding to the propagation time to point C is the total length of the measured optical fiber.

Even in the work of laying the small optical cable described with reference to FIG. 1, if the optical cable is sound, the same measurement result as in FIG. 3 can be obtained. The measurement result in the first stage is shown in FIG. 2 (A), and the Fresnel generated at the optical fiber connection point in the connection closure at the points p, q, r from the base station located on the left side in the figure. While passing through the small peaks P, Q, and R due to the reflected light, the small peak S due to the Fresnel reflected light generated at the connection point between the optical fiber of the aerial optical cable and the optical fiber of the small optical cable in the aerial closure at the point s appears. The subsequent slope of the Rayleigh backscattered light, that is, the distance from the s point to the t point, corresponds to the length of the small optical cable prepared, and is 600 m in this example. A small peak T due to reflected light appears. In FIG. 2, the horizontal axis is not taken to have a length proportional to time, but each point is shown at an appropriate position for easy viewing of the figure.

From the second stage to the third stage, the small optical cable is pulled out from the optical cable housing, but since the length of the small optical cable does not change, the measured OTDR
As for the waveform, the state of FIG. 2A is held.

On the other hand, when the curve bends the transmission loss, for example, when it is bent at a corner of a house pillar,
A local step difference of the OTDR waveform occurs due to the increase in loss.
U in FIG. 2B indicates a local increase in loss. Therefore, it is possible to detect in the base station whether or not there is an abnormality at the time of installation and where the position of the abnormality is on the small optical cable. In such a case, by reporting this result to the construction site, it is possible to quickly repair or recover the abnormal point.

FIG. 2C shows an OTDR waveform when the small optical cable is cut after the required extra length is taken in the fourth stage. At the cutting point position v, a small peak V due to Fresnel reflected light appears. Since the distance between s and v is known, the laying length of the small optical cable can be detected. Further, from this result, the amount of the small-sized optical cable remaining in the optical cable housing can be known from the difference in the distance between st and sv.

It can be used when two or more optical fibers are accommodated in a small optical cable. For example,
In the case of the optical drop line described in FIG. 1, the two optical fibers on the lower mouth side of the small optical cable housed in the small optical cable housing are connected, and one optical fiber on the upper mouth side of these two fibers is connected. The light input end is used, and the other optical fiber is used as the light output end. Then, in the base station of the optical fiber in the wired optical cable connected to each optical fiber, the light source and the light receiver are respectively joined, light is passed through this series of optical fiber loops, and the optical transmission loss is measured. Due to the increase in the optical transmission loss during the laying, it is possible to detect the occurrence of the failure or the abnormality of the small optical cable during the laying.

[0030]

As is apparent from the above description, according to the present invention, the required number of expensive optical measuring instruments can be reduced and the work can be reduced. In addition, the management of remaining optical cable lines, the wiring network and the optical drop-off can be achieved. There is an effect that the length of the optical cable of the line can be centrally managed by the base station, and it is effective when used in a terminal optical communication system such as an optical subscriber system.

[Brief description of drawings]

FIG. 1 is an explanatory diagram of an example of a method of laying a light drop line.

FIG. 2 is an explanatory diagram showing an example of a measurement result in the method for laying a light drop line according to the present invention.

FIG. 3 is an explanatory diagram of general measurement results by the OTDR method.

FIG. 4 is a schematic view of an example of an optical wiring system.

[Explanation of symbols]

 1 Base Station 2 OTDR Measuring Equipment 3a, 3b, 3c Connection Closures 4a, 4b, 4c Wiring Cables 5a, 5b Utility Pole 6a, 6b Aerial Closure 7a, 7b Aerial Optical Cable 8 Optical Drop Line 9 Drop Point 10 Small Optical Cable 11 Optical Cable Storage 12 Connector 13,14 Resting part 15 Extra length 16 Cutting point

Claims (4)

[Claims] 1. A method of laying a small-sized optical cable containing an optical fiber, wherein an optical fiber at an upper end of the small-sized optical cable housed in an optical cable housing is connected to an optical fiber in an optical cable at a base station side of an optical communication network, Light is incident on the optical cable from the base station side, is sent to the small optical cable, the backscattered light is measured, and the condition of the optical fiber due to feeding and laying of the small optical cable is measured. Optical cable laying method. 2. A method of laying a small-sized optical cable containing two or more optical fibers, wherein two optical fibers are connected to each other through a lower opening of the small-sized optical cable housed in an optical-cable housing, The optical fiber of the two cores is the optical fiber of the optical cable of the base station side of the optical communication network.
The optical fibers are connected to the cores respectively, light is made incident on one of the two optical fibers of the optical cable from the base station side, and the amount of light emitted from the other is measured, and the optical fibers are drawn out and laid by the small optical cable. A method of laying a small optical cable, characterized by measuring the situation of. 3. The small optical cable according to claim 1 or 2, wherein a small-length optical cable having a continuous length is used, and the small optical cable is cut after measuring the condition of the optical fiber by feeding and laying the optical cable. How to lay a small optical cable. 4. The method for laying a small optical cable according to claim 1, wherein the laying and feeding are performed while measuring the presence or absence of abnormality during laying of the small optical cable.