JPH07209563A - Low-skew multiple optical fiber cable - Google Patents

Abstract

PURPOSE:To make skew low and equalize the length of each coated optical fiber by forming the optical fiber cable so that the length of the optical fiber cable is equal to the length of the optical path length of all coated optical fibers. CONSTITUTION:After coated optical fibers 1a and 2a which are equal in coated optical fiber length, but different in optical path length are divided equally into two, different coated optical fibers 1a and coated optical fibers 2a are connected to each other at connection points 4 by fusion splicing or through connectors, etc., to obtain their original length. Consequently, coated optical fibers 1A and 1B having desired length become equal in optical path length and also become equal in length. Further, at least one of the coated optical fibers 1a and 2a is cut and a coated optical fiber which is different in propagation speed from the coated optical fibers la and 2a is connected to obtain the low-skew multple optical fiber cable which has desired coated optical fiber length and is equal in length between the coated optical fibers.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a low skew multi-core optical fiber cable used for parallel transmission.

[0002]

2. Description of the Related Art In parallel transmission, when signals input simultaneously to respective cores of an optical fiber cable propagate in an optical fiber, and signals of the respective cores greatly vary in time on the output side,
Sampling at the receiver becomes difficult. As a result, the probability of occurrence of sampling error increases, the reliability of the system deteriorates, high-speed transmission is hindered, and the transmission distance is limited.

The fact that the signals input simultaneously to the plurality of optical fibers fluctuate temporally on the output side, that is, the difference in the transmission time of the plurality of optical fibers is called optical fiber skew.

In order to reduce the optical fiber skew, the optical fiber core wire 1 having a long transmission time as shown in FIG.
There is a method in which the optical fiber length is provided and the multi-core optical fiber cable is made to have a low skew by cutting the cable so that the transmission time becomes equal to that of the other optical fiber core wire 2.

Further, as described in JP-A-1-99335, by providing an optical switch and an optical delay means in the multi-fiber optical fiber cable, the skew is adjusted and reduced, and the multi-fiber optical fiber cable is lowered. There is also a method of skewing.

[0006]

SUMMARY OF THE INVENTION In the above prior art,
Since the optical fiber core wires are cut to make the optical path lengths uniform, the lengths of the optical fiber core wires are not equal. For this reason,
When the connector 3 and the like are attached to the terminal as shown in (3), extra length is generated, which causes problems in work and space.

Further, in the method described in Japanese Patent Laid-Open No. 1-99335, it is necessary to prepare an optical switch and an optical delay means, which complicates the transmission system.

In any of the above methods, measurement for skew adjustment is required, which is troublesome.

Further, the above problems may occur in a multi-core optical fiber cable having a structure in which tape fibers are laminated. That is, this type of multi-fiber optical fiber cable is, as shown in FIG.
6 and 7 are laminated and bundled with a common coating 8 to form a cable. When this multi-core optical fiber cable is wound on a bobbin at the time of manufacturing, a difference between the inner circumference and the outer circumference occurs. Figure 5
The situation where a multi-core optical fiber cable having a tape fiber laminated structure is wound around a bobbin 9 is shown. As is clear from this figure, the length a of the inner circumference tape fiber 5 and the length b of the outer circumference tape fiber 7 per unit length of the cable are different, which causes a skew.

The present invention has been made in view of the above problems, and it is a common object of the present invention to reduce the skew of a multi-fiber optical fiber cable without using other means such as an optical switch. . A first object of the present invention is to provide a low-skew multi-core optical fiber cable that enables the lengths of the respective cores to be equal. A second object of the present invention is to provide a low-skew multi-fiber optical fiber cable that can achieve the above-mentioned common object and the first object in a tape fiber laminated structure.

[0011]

[Means for Solving the Problems] The first means of the present invention provided to achieve the above-mentioned common purpose and the first object are:
An optical fiber cable is a low-skew multicore optical fiber cable formed so that the optical path length of all the optical fiber cores of the optical fiber cable is equal. Also,
The second means of the present invention provided to achieve the above second object is to provide N (N) tape fibers in the thin direction.
≧ 2) In an optical fiber cable having a laminated structure, the tape is cut at the center of the entire length of the optical fiber cable, and the i-th layer (1 ≦ i ≦ N) and (N ≦ N) in the tape fibers of both cable parts cut by the center are cut. It is a low-skew multi-fiber optical fiber cable in which the (-i + 1) layer is connected to each other.

[0012]

By the above first means, the length of each core and the optical path length become equal. Further, by the second means, the length of each layer tape fiber and the optical path length are equalized in the tape fiber laminated structure.

[0013]

FIG. 1 shows an embodiment of a low-skew multicore optical fiber cable embodied by the first means of the present invention. Since the same parts as those of the conventional one are designated by the same reference numerals, the description thereof is omitted. In this embodiment, all the optical fiber core wires 1A and 1B of the optical fiber cable are formed to have the same optical path length. By doing so, the length of each core wire 1A, 1B becomes equal to the optical path length, and each core wire 1A
It is possible to obtain a low-skew multi-core optical fiber cable that enables the lengths A and 1B to be equal. That is, the optical fiber cores 1a and 2a having the same length of each core but different optical path length are cut into two equal parts, and then the optical fiber core 1a and the optical fiber core 2a have a connection point 4. Optical fiber cores 1a, 2 which are different by fusing or connectors
a Connect the comrades and restore the original length. By doing so, the optical path lengths of the optical fiber core wires 1A and 1B having a desired length become equal, and a low-skew multicore optical fiber cable in which the core wires 1A and 1B have the same length can be realized.

In the above embodiment, as shown in FIG. 1, after cutting the optical fiber cores 1a and 2a,
Although they are crossed and connected and returned to the original length, at least one of the optical fiber core wires 1a and 2a is cut, and the optical fiber core wires different in propagation speed from the optical fiber core wires 1a and 2a are connected. Thus, it is possible to set the optical fiber core wire to a desired length, and to make a multi-core optical fiber cable in which each core wire has the same length and has a low skew.

Further, the example in which the two single-core optical fibers are the low-skew multi-core optical fiber cables has been described, but a plurality of single-core optical fibers or a plurality of multi-core optical fibers may be used. It is possible to adjust the cutting position and a low skew after cutting.

According to the present embodiment described above, it is possible to realize a low-skew multicore optical fiber cable in which the lengths of the respective cores are equal.

FIG. 3 shows an embodiment of a low-skew multicore optical fiber cable embodied by the second means of the present invention. The cable of this embodiment is shown in FIGS.
It has a tape fiber laminated structure as shown in (a). That is, a plurality of tape fibers 5, 6 and 7 are laminated in the thin direction and are bundled by a common coating 8.

In the multi-core optical fiber cable of this embodiment, however, a difference in inner and outer circumferences occurs due to the winding, and as shown in FIG. 6, the length a of the inner circumference tape fiber per unit length of cable is In order to prevent the length b of the outer peripheral fiber from being different, the optical fiber cable as shown in FIG. 3A is cut at a half position of the total length 2L, and as shown in FIG. A cable portion having an equal length L is formed. Then, by appropriately reversing one of the left and right cable portions, the i-th layer (1 ≦ i ≦ N, N ≧ 2) on one side and the (N−i + 1) -th layer are aligned with each other. They are designed to connect to each other. FIG. 3C shows the situation after connection. Since the example in the figure is an example of three lines, the lowermost layer (first layer) and the uppermost layer (Nth layer) of the stack are connected to each other so that the second layer and the N-1th layer are aligned. Then, the tape fibers are fused or connected by a connector or the like.

Here, considering the case where the multi-fiber optical fiber cable of this embodiment is wound on a bobbin as shown in FIG. 6, the lowermost layer tape fiber and the i-th layer fiber (1≤i≤) generated by one bobbin winding are considered. The difference ΔL between the lengths of N and N ≧ 2) is r, the radial distance from the center of the bobbin 9 to the lowermost layer tape fiber, and the radial distance from the i-th layer tape fiber to the (i + 1) -th layer tape fiber. When the width of the optical fiber cable is d and the width of the optical fiber cable is w, Expression 1 is obtained.

[0020]

[Equation 1]

Table 1 shows the relational numerical values of the equation 1 (r = 15).
0 mm).

[0022]

[Table 1]

As is clear from Table 1 and Equation 1, the difference ΔL in the tape fiber length is substantially proportional to the tape fiber No. i, and the width w of the optical fiber cable has a small effect. From this proportional relationship, when the present embodiment is applied to the cable as shown in FIG. 4, the skew caused by the structure of the optical fiber cable is canceled and the low skew optical fiber cable can be easily manufactured. Also, the cutting position deviation from the center of the optical fiber cable is x, and the difference in tape fiber length between the lowermost layer and the uppermost layer per unit length is Δ.
When this embodiment is applied to the optical fiber cable which is l,
The tape fiber length difference Δ per unit length is expressed by Equation 2.

[0024]

[Equation 2]

When the optical fiber cable is long and cannot be manufactured on the same circumference of the bobbin, the optimum position for cutting can be determined by considering the equations 1 and 2.

In this embodiment, the cable has 16 cores (8 cores x
As a result of using the two-layer optical fiber cable (100 m in total length), it was confirmed that the skew of 150 ps between the two tracers (the first core of the tape fiber) can be reduced to about 30 ps.

FIG. 7 shows an embodiment of what is called a slot type optical fiber cable. In this slot type optical fiber cable, in a slot 11 having a tension member 10 at the center, grooves 13 for accommodating tape fibers 12 stacked in the thin direction thereof are provided at a plurality of positions on the outer circumference, and the grooves are arranged in the longitudinal direction of the cable. It is formed in a spiral shape. 14 is a protective coating. Since the tape fiber 12 is spirally wound, a difference in inner and outer circumferences (twisting ratio) occurs between the lowermost layer and the uppermost layer of the groove, which causes skew.

Therefore, the present cable is cut at a position of half of the total length, and the lowermost layer of the laminated layers (first layer) which is not always in the same groove is cut.
Layer) and the uppermost layer (Nth layer), the second layer and the N-1th layer, ...
The tape fibers are connected by fusing or a connector so that Further, the connection portion is protected if necessary.

In this embodiment, 300 fibers (4 fibers × 5 layers × 15) are used.
As a result of using the grooved optical fiber cable (50 m in total length), the skew between the tracers of the first layer and the fifth layer tape fiber of about 440 ps could be reduced to about 50 ps.

It is not necessary to connect the tracers to each other when the i-th layer and the (N-i + 1) -th layer of the tape fiber are connected after cutting at a predetermined position.

[0031]

According to the low-skew multi-core optical fiber cable embodied by the first means of the present invention as described above, the optical fiber cable has the optical path length of all the optical fiber cores of the optical fiber cable. Since the lengths of the cores are made equal to each other, the lengths of the cores are equal to the optical path lengths, so that it is possible to obtain a low-skew multicore optical fiber cable in which the lengths of the cores can be equalized.

According to the low skew multi-core optical fiber cable embodied by the second means of the present invention, in the tape fiber laminated structure, the length of each tape fiber is equal to the optical path length, and each tape fiber is It is possible to obtain a low-skew multicore optical fiber cable by making the lengths of the cables equal.

In each of the first and second means, it is possible to reduce the skew of the multi-fiber optical fiber cable without using other means such as an optical switch.

[Brief description of drawings]

FIG. 1 is an explanatory view showing an embodiment by a first means of a low skew multi-core optical fiber cable of the present invention.

FIG. 2 is an explanatory diagram showing an example of a conventional low-skew multicore optical fiber cable.

FIG. 3 is an explanatory diagram showing a problem of the multi-core optical fiber cable shown in FIG.

FIG. 4 is an embodiment of the second means of the low skew multi-fiber optical fiber cable according to the present invention, in which (a) is an explanatory view before cutting, (b) is an explanatory view of a cutting condition, and (c) is Explanatory drawing of the connection situation after disconnection.

FIG. 5 is a cross-sectional view showing an example of an optical fiber cable having a tape fiber laminated structure.

6 is an explanatory view showing a problem of the optical fiber cable shown in FIG.

FIG. 7 shows an example of a slot type multi-fiber optical fiber cable,
(A) is a cross-sectional view and (b) is a side view.

[Explanation of symbols]

 1A, 1B Optical fiber core wire 5, 6, 7, 12 Tape fiber

Continuation of front page (51) Int.Cl. ⁶ Identification code Office reference number FI technical display location H04B 10/12

Claims (3)

[Claims] 1. A low-skew multi-core optical fiber cable in which the optical fiber skew of the difference in transmission time of a plurality of optical fiber core wires of the multi-fiber optical fiber cable is reduced, wherein the optical fiber cable is the optical fiber cable. A low-skew multicore optical fiber cable, characterized in that it is formed so that the optical path lengths of all the optical fiber cores are equal. 2. An optical fiber cable according to claim 1, wherein the optical fiber cable is formed by connecting at least one optical fiber core wire of the optical fiber cable to an optical fiber core wire having a different propagation speed of light. Fiber optic cable. 3. N tape tapes (N
≧ 2) In an optical fiber cable having a laminated structure, the tape is cut at the center of the entire length of the optical fiber cable, and the i-th layer (1 ≦ i ≦ N) and (N ≦ N) in the tape fibers of both cable parts cut by the center are cut. A low-skew multi-fiber optical fiber cable characterized in that it is connected to the (i + 1) layer.