JPS6212885B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a method for measuring optical fiber connection loss that can be used, for example, on utility poles or in manholes in optical communication networks.

[Prior art]

As optical communication using optical fiber cables is put into practical use, there is a growing need to connect optical fibers in installed optical fiber cables in manholes or on utility poles. In such connection work, the usual method is to perform the connection while measuring the connection loss. Conventionally, for this purpose, a configuration as shown in FIG. 1 has been adopted. That is, a light source 1, optical fibers 2A and 2B to be connected, and a light receiver 3 are used. Unlike the installation location (a) of the light source, the connection location (b) of the optical fiber, and the installation location (c) of the light receiver 3, these locations are usually separated by several hundred meters or more. In recent years, taking advantage of the small diameter and light weight of optical fiber cables, as the length of cable installation has increased, these locations have become more and more
The distance between b and c tends to be longer.

Conventionally, to measure splice loss with such a configuration, first, as shown in Figure 2a, the light from light source 1 is passed through optical fiber 2A, and the optical power emitted from optical fiber 2A at the splicing location B is measured. _Q1
(dBm) is measured by the optical receiver 3. Next, as shown in FIG. 2b, at the connection location RO, the optical fiber 2A,
After connecting optical fiber 2B, the optical power Q ₂ (dBm) emitted from optical fiber 2B is measured at location C.
Here, the loss per unit length of optical fiber 2B α _B
(dB/Km) has been measured in advance, and the length l (m) of the optical fiber 2B is known. The connection loss at this time is found as Q ₁ −Q ₂ −α _B ·l/1000 (dB).

As explained above, in order to measure splice loss using the conventional method, the light source installation location A, the connection location B,
The photoreceiver installation locations C and C were far apart from each other. For this reason, there is a drawback that a large number of personnel are required to work on the construction, leading to an increase in construction costs. Another disadvantage is that it is difficult to monopolize three locations (A, B, and C) at the same time in areas with heavy traffic, making it difficult to carry out construction work. Furthermore, in this conventional method, it was necessary to measure the loss of the optical fiber 2A.

[Summary of the invention]

This invention bends an optical fiber, irradiates the bent portion with light to allow light to enter the optical fiber, and performs a temporary connection process and a main connection process,
It is characterized by measuring the leakage optical power from the optical fiber connection part in these two connection steps,
The purpose is to make it possible to measure the splice loss of optical fibers at the location where they are connected, thereby reducing the cost of splicing and simplifying the method of splicing.

〔Example〕

FIG. 3 shows the configuration of the measuring method of the present invention. In this invention, a light source 1 is provided at a connection location RO, and a light receiver 3 is provided at this location RO.

In the method for measuring splice loss according to the present invention, as shown in FIG. is incident. The bent portion 2Aa is formed at the connection location B, and is located several meters away from the connection end of the optical fiber 2A. This length may not be very long depending on the environment of the connection location, but if possible it is 2m.
The above is preferable. In addition, this bent portion 2Aa is fixed during the following steps to connect the light source 1 and the optical fiber 2.
The coupling efficiency with A should not change. light source 1
As semiconductor lasers, gas lasers, white lamps,
A xenon lamp or the like may be used, and continuous light or pulsed light may be used.

The coupling efficiency between the light source 1 and the optical fiber 2A becomes extremely small when the optical fiber 2A is doubled over. If the optical fiber 2A is coated with a colored coating, the coupling efficiency will be further reduced. As a result of an experiment by bending a coated optical fiber within its allowable bending radius,
Coupling of about -40dB was possible. Although this value depends on the geometric shape of the light source 1 and the bent portion 2Aa, the coating material, the coating color, etc., this level of coupling can be expected.

The optical receiver 3 measures the optical output P ₁ from the connecting end of the optical fiber 2A.

After that, as shown in FIG. 4b, the optical fiber 2A is
and 2B (temporary connection process), and measure the power _P2 of the light leaking from the temporary connection. This measurement can be carried out correctly, for example, by moving the receiver 3 along the axis of the optical fiber. Figure 4a,
The light receivers 3 used for each measurement in b may be the same or different. In FIG. 4b, the direction in which the light receiver 3 is moved is indicated by an arrow A-A'.

Next, as shown in FIG. 4c, the optical fiber 2B is cut into a short length BS and a long length BL near the temporary connection part. In the figure, the optical fiber 2B is cut at a distance αm from the temporary connection, but this α is about 1 to 2 m. After this disconnection, the optical power output is emitted from the end face of the short optical fiber BS in the above temporarily connected state.
Measure _P3 . If the optical fiber 2B is initially lm, the length of the long optical fiber BL to be finally connected by this cutting becomes (l-α)m.

After measuring P ₃ , as shown in Fig. 4d, the temporary connection is cut, and the optical fiber 2A and the optical fiber 2B (l-α)m, that is, the long optical fiber
Connect to BL again (main connection process). After that, as shown in Figure 4e, the power of the leaking light from the connection part is
P ₄ is measured by the same method as shown in Figure 4b.

Through the above operations, the connection loss L of this connection is determined as follows.

L=-10 log ₁₀ (1-KP ₄ /P ₁ ) (dB) (1). K is a value that depends on the distance between the light receiver 3 and the optical fibers 2A, 2B, etc. Connection loss of temporary connection
L' is also L'=-10 log ₁₀ K(1-KP ₂ /P ₁ ) (dB) (2), but L' is also L'=-10 log ₁₀ (P ₃ /P ₁ ) (dB ) (3). Find K from equations (2) and (3), and use equation (1)
By substituting into , L becomes the following formula.

L=-10 log [1-( _P1 - _P3 ) _P4 / _{P1P2 ]}
(dB) (4) In order to increase the coupling efficiency between the light source 1 and the optical fiber 2A, the methods shown in FIGS. 5 and 6 can be considered. In FIGS. 3 and 4, the bent portion 2Aa is bent half a time, but as shown in FIG. 5, n times of wavy bending and as shown in FIG. 6, n times of coiled bending are possible. FIG. 5 shows wavy bending with n=3, and FIG. 6 shows coiled bending with n=2.

In addition, as a method for measuring the leakage light from the connection part with the optical receiver 3, in addition to moving the optical receiver 3 in the A-A' direction as shown in FIG. It is also possible to move the light receiver 3 in the BB' direction along a spiral with 2A and 2B as axes. Alternatively, as shown in FIG. 12, a plurality of light receivers 3 may be arranged along the optical fibers 2A, 2B near the connection portion, and the outputs of these light receivers 3 may be added. Furthermore, as shown in FIG. 13, these light receivers 3 may be arranged in a plurality of rows on the circumferential surface of the optical fiber, and the outputs of all these light receivers may be added.

Further, a splice loss measuring device based on the method of the present invention includes a bending jig, a light receiver, and a mechanism for moving the light receiver along the axis of the optical fiber as necessary. For example, as shown in FIG.
This is to make A move away. The coiled bending shown in FIG. 6 can be achieved, for example, by winding the optical fiber 2A around the cylinder 4. Also,
In order to achieve the wavy bending shown in FIG. 5, a plurality of cylinders 4A are arranged in parallel at equal intervals as shown in FIG.
4E, the optical fiber 2A is sequentially passed through the cylinder 4 in a zigzag manner and aligned with the circumferential surface of the cylinder. Alternatively, as shown in FIG. 10, by pressing the optical fiber 2A against a plate 6 having semi-cylindrical protrusions 5A to 5D arranged in parallel, it is possible to bend the optical fiber 2A in a wavy manner.
The mechanism for moving the light receiver 3 along the axis of the optical fiber can be realized by moving the light receiver with a motor or the like.

In the above explanation, a single optical fiber was used as an example.
However, even with a multi-core optical fiber as shown in Figure 11, it is possible to change the wavelength of the incident light at each bent part, to make light of different wavelengths enter each optical fiber, and to separate them using a filter at the light receiving part. Simultaneous measurement of splice loss is possible. Note that 7 in FIG. 11 is a coating. The measurement of the optical powers P ₁ , P ₂ , and P ₃ is not limited to the above order. For example, after measuring the optical power _P3 , the optical power _P1 may be measured when the optical fiber 2A and the optical fiber BS are separated, or after measuring the optical power _P3 , the optical power _P2 may be measured. good.

〔effect〕

As explained above, the method of the present invention involves bending an optical fiber, irradiating the bent portion with light to allow light to enter the optical fiber, performing a temporary connection process, and then temporarily connecting one optical fiber. Cut it into short pieces and long pieces from the point, then separate the short pieces,
The purpose is to make two connections, including the final connection of a long item, and measure the leakage from the optical fiber connection at each time, as well as the optical power from the end face of the short item in the tentatively connected state. Optical fiber splice loss can be measured on-site, which has the advantage of reducing the number of personnel required for construction and eliminating the need for communication to calculate splice loss, resulting in a significant reduction in construction costs and a significant reduction in construction work. It can be simplified.

[Brief explanation of the drawing]

Figure 1 is a configuration diagram for conventional connection loss measurement.
Figure 2 is a diagram showing the measurement order of the conventional splice loss measurement method, Figure 3 is a block diagram for the splice loss measurement method of the present invention, and Figure 4 is a diagram showing the measurement order of the splice loss measurement method of the present invention. 5 and 6 are respectively perspective views showing other examples of the bent portion of the optical fiber, FIG. 7 is a view showing other examples of the moving direction of the light receiver in measuring leakage light, and FIG. Figures 10 to 10 are perspective views showing an example of an optical fiber bending jig, Figure 11 is a perspective view showing a multi-core optical fiber, and Figure 12 is a measurement of leakage light from the fiber connection. FIG. 13 is a diagram showing a modification of FIG. 12. 1: Light source, 2: Optical fiber, 3: Light receiver, 4:
Cylinder, 6: projection plate, 7: covering.

Claims (1)

[Claims] 1. By bending the optical fiber A and irradiating the bent portion of the optical fiber A with light, the light enters the optical fiber A, and the optical power P ₁ emitted from the end face of the optical fiber A is determined. a first step of measuring; a second step of temporarily connecting the end face of the optical fiber A and the end face of the optical fiber B to be connected, and measuring the power _P2 of the light leaking from the temporary joint; In the temporarily connected state, the optical fiber B is cut into two pieces, a short BS and a long BL, near the temporary connection part,
A third step of measuring the optical power P ₃ emitted from the end face of the short optical fiber BS, and then separating the temporary connection between the optical fiber A and the short optical fiber BS, and connecting the optical fiber A and the long optical fiber again. A fourth step of making a main connection with the BL and measuring the power P ₄ of the leaking light from the main connection part,
The connection loss L (dB) between optical fiber A and long optical fiber BL is L=-10 log ₁₀ [1-(P ₁ -P ₃ )P ₄ /P
₁ P ₂ ] A method for measuring optical fiber connection loss calculated by the formula: