JPH11295569A - Optical transmission line and optical transmission line formation method - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide the optical transmission of small skewness generated among plural multiple optical fibers and to accelerate a speed at the time of data transmission, that is a communication speed, by providing respective multi- channel waveguides with a length adjusted based on a transmission time difference among the multi-channel waveguides in the optical transmission line for performing optical parallel transmission by the plural multi-channel waveguides. SOLUTION: A phase difference among the multiple (12-core, for instance) optical fibers F1...F4 is detected (S3). Thus, the transmission time difference among the multiple optical fibers F1...F4 whose reference is the optical fiber of a 12th core of the multiple optical fiber F4 is calculated (S4). Based on the calculated transmission time difference, conversion to the transmission time difference for which the optical fiber of the 12th core of the multiple optical fiber F4 is the same reference is performed (S5). Based on the transmission time difference, the length to be adjusted of the respective multiple optical fibers F1...F4 is obtained (S7). Then, based on the calculated cutting length, the respective multiple optical fibers F1...F4 are cut (S8).

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an optical transmission line constituted by a plurality of multi-core optical fibers and an optical transmission line forming method, and more particularly to a method for performing optical parallel transmission using a plurality of multi-core optical fibers. The present invention relates to an optical transmission path and an optical transmission path forming method suitable for use.

[0002]

2. Description of the Related Art As is well known, data processed by a central processing unit of a computer, a so-called CPU or the like, has zero data.
Or, it is handled in a state converted into a bit represented by 1. In recent years, with the performance enhancement of the CPU,
The number of bits processed by the CPU has been increased from 8 bits to 16 bits, 32 bits, and further to 64 bits.

Conventionally, when transmitting this kind of data,
The data composed of a plurality of bits is once serially rearranged in the order of each bit, and then transmitted using one communication line. When receiving the transmitted data, the bits converted to serial data are restored to the original state by parallelizing the data again.

[0004] The above-mentioned bit conversion operation performed at the time of communication is performed using an IC having a predetermined function, so that cost reduction and size reduction have been achieved and high reliability has been obtained. However, the IC used for this bit conversion operation needs to have a function of processing speed of (communication speed × number of bits), but with the recent increase in the communication speed and the increase in the number of bits of data, the IC has been rapidly advanced. Thus, it has become impossible to reduce the cost of an IC that supports high-speed processing.

Therefore, a method of communicating data in a parallel state (multi-bit) has been studied, a communication speed of 1 giga Hz or more is required, and it is less expensive than a metal wire.
Optical fibers have come to be used because modulation and demodulation with few errors are possible. Generally, as this kind of optical fiber, in order to make it easy to handle the optical fiber, a multi-core optical fiber composed of a plurality of optical fiber strands, for example, a plurality of optical fiber strands are arranged in parallel and in a line to collectively. Coated, and integrated into a tape shape,
A so-called optical fiber ribbon is widely used.

In the data communication method using the optical fiber ribbon, data transmission and reception can be performed simultaneously by allocating one optical fiber for each bit constituting data. . In this case, a slight time difference, so-called skew, occurs in the transmission time of the data transmitted by the plurality of optical fiber wires.

When the skew is large, the transmission speed of the entire data cannot be increased because the transmission of a certain bit has been completed but the transmission of the other bits has not been completed. Therefore, various researches and developments have been conducted to minimize the skew between the optical fibers constituting the optical fiber ribbon.

As a result, by selecting the same kind of optical fiber as the optical fiber and adjusting the tension for feeding the fiber in the tape forming step, it is possible to obtain an optical fiber ribbon with a reduced skew. became. Therefore, if the optical fiber is in the optical fiber ribbon, the installation location is the same, so that the stress and the amount of bending are almost equal, and since the manufacturing conditions are uniform, a considerable signal delay occurs between the optical fibers. It wasn't a big problem.

[0009]

However, the conventional optical transmission line and the optical transmission line forming method as described above include:
The following problems exist. Conventionally provided low skew optical fiber tape cores are obtained by unifying a plurality of optical fiber wires into one, that is, each optical fiber is integrated as a tape, and optical connectors are provided at both ends of the tape. It is assumed that the transmission time of the optical fiber in the tape hardly changes even if it is attached.

As for these optical fiber tape cores and optical connectors, up to 12 cores are standardized and provided, but those with more cores are not mass-produced. On the other hand, CPUs generally process 32-bit to 64-bit data.

Therefore, when data is transmitted by this CPU, for example, three or more 12-core tapes are used for a 32-bit signal and 12-core tapes are used for a 64-bit signal as a signal transmission path.
Six or more core tapes are required. In this case, since the conditions for placing each tape are slightly different, it has been necessary to adjust the tape length so that the skew between these tapes is reduced.

SUMMARY OF THE INVENTION The present invention has been made in view of the above points, and has as its object to provide an optical transmission line and an optical transmission line forming method with small skew generated between a plurality of multicore optical fibers. I do.

[0013]

In order to achieve the above object, the present invention employs the following constitution. The optical transmission line according to claim 1, wherein the optical transmission line performs optical parallel transmission by a plurality of multi-line waveguides, wherein each of the multi-line waveguides is adjusted based on a transmission time difference between the multi-line waveguides. It is characterized by having a predetermined length.

Therefore, in the optical transmission line of the present invention, since the length of each multi-line waveguide is adjusted based on the transmission time difference between the multi-line waveguides, optical parallel transmission is performed using this optical transmission line. When this is done, it is possible to adjust the transmission time difference that occurs between the multi-line waveguides. As the multi-line waveguide, various configurations such as a multi-core optical fiber such as an optical fiber tape or a substrate waveguide corresponding to a multi-line can be adopted.

According to a second aspect of the present invention, there is provided a method of forming an optical transmission line using a plurality of multi-core optical fibers, the method comprising: detecting a transmission time difference between the multi-core optical fibers; The length of each of the multi-core optical fibers is adjusted based on the detected transmission time difference.

Therefore, in the optical transmission line forming method of the present invention,
The length can be adjusted for each of the multiple optical fibers based on the transmission time difference.

According to a third aspect of the present invention, in the optical transmission line forming method of the second aspect, the transmission time difference between the multi-core optical fibers is a transmission time difference generated for each of the multi-core optical fibers. After the detection, the transmission time difference is calculated based on the average value of the maximum value and the minimum value of the detected transmission time difference.

Therefore, in the optical transmission line forming method of the present invention,
The transmission time difference between each multi-core optical fiber is calculated based on the average value of the maximum value and the minimum value of the transmission time difference detected for each multi-core optical fiber. Between transmission time differences can be minimized.

[0019]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of an optical transmission line and an optical transmission line forming method according to the present invention will be described below with reference to FIGS. Here, for example, an example in which the optical transmission path is an optical cable and the multi-core optical fiber is an optical fiber tape will be described.

In FIG. 2, reference numeral 1 denotes an optical transmission line (optical cable). The optical transmission line 1 protects and assembles a plurality (four in the figure) of multi-core optical fibers (optical fiber tape cores) F, and includes an outer jacket 2 and a plastic contained in the outer jacket 2. And a pair of tension members 4 and 4 that bear the tension applied to the optical transmission path 1. The multi-core optical fiber F is a kind of multi-line waveguide.

The slot 3 is formed with a slot groove 5 having a rectangular cross section in the longitudinal direction thereof. In the slot groove 5, four multi-core optical fibers F are arranged in a stacked state. Therefore, the physical and mechanical conditions applied to each multi-core optical fiber F ... F in the slot 3 are as follows:
They are set almost equal. Each multi-core optical fiber F is 1
Two optical fibers (not shown) are arranged in parallel and in a line, coated collectively, and integrated in a tape shape, which is referred to as a 12-core fiber ribbon. Also,
These multi-core optical fibers F are adjusted in length based on the transmission time difference between the multi-core optical fibers F.

Here, a skew measurement system for measuring the transmission time difference between the multi-core optical fibers F, that is, the skew, by the phase method will be described. This skew measurement system is shown in FIG.
As shown in (1), a measuring device 6 that modulates the frequency freely and outputs it as an electric signal, such as a network analyzer
An E / O converter 7 for converting an electric signal output from the measuring device into an optical signal; and a fan-out cord (multi-core single core) connected to the multi-core optical fiber F via the MT connectors 8 and 8. Conversion selectors 9 and 10, a fiber selector 11 for switching the optical signal converted by the E / O converter 7 to the branch line of the fan-out code 9, and a fiber selector for switching the branch line of the fan-out code 10. An O / E converter 13 for converting an optical signal output through the fiber selector 12 into an electric signal, and a control unit 14 using a computer or the like.

The E / O converter 7 is connected to the fiber selector 11 via the optical single-fiber connector 15, and the O / E converter
The converter 13 is connected to the fiber selector 12 via a single optical fiber connector 16. Fiber selector 11,
Reference numeral 12 indicates that the internal fiber can be exchanged.
(Single mode) and MM (Multi mode) can be measured accurately. Therefore, the configuration is such that the connection loss due to the core diameter difference can be minimized. The control unit 14 performs all controls of the skew measurement system, such as frequency setting of the measurement device 6, switching instruction of the fiber selectors 11 and 12, phase measurement, calculation of transmission time difference, and the like.

Next, a method for adjusting the length of each multi-core optical fiber F based on the transmission time difference between the multi-core optical fibers F... F will be described with reference to the flowchart shown in FIG. Here, four multi-core optical fibers are referred to as F1.
4 will be described. First, fan-out codes 9 and 10
The transmission time difference is measured for each line of the fan-out codes 9 and 10 in order to eliminate the influence of the transmission time difference of the transmission line.

That is, in FIG. 3, the fan-out cords 9 and 10 are short-circuited by directly connecting the MT connectors 8 and 8 without connecting the multi-core optical fiber F. Then, the controller 14 sets the frequency, and outputs a signal of this frequency from the measuring device 6. The output signal is converted from an electric signal to an optical signal in the E / O converter 7 and input to the fiber selector 11 via the optical single-fiber connector 15.

At this time, the fiber selectors 11 and 12
Are previously set by the control unit 14 to the fan-out codes 9 and 10.
Are switched so that the predetermined line is selected.
Therefore, the optical signal input to the fiber selector 11 is output from the fiber selector 12 to the O / E converter 13 via the optical single-fiber connector 16 after passing through predetermined lines of the fan-out codes 9 and 10. Here, the light signal is converted into an electric signal.

After the converted signal is output to the measuring device 6, its phase θC01 is measured by the control unit 14. Similarly, by switching the fiber selectors 11 and 12 by operating the control unit 14, the lines of the fan-out codes 9 and 10 are sequentially measured, and the phases θC01 to θC12 of the signals passing through each line are detected.

Next, as shown in FIG. 3, the multi-core optical fiber F1 is connected to the fan-out cords 9, 10 by the MT connectors 8, 8. Then, according to the same procedure as described above, the phase θF10
1 to detect the phase θF112.

Here, the influence of the phase of the fan-out codes 9, 10 corresponding to the phase of the optical fiber of the multi-core optical fiber F1 is eliminated, and the phase θF1 of the multi-core optical fiber F1 itself is eliminated.
T is calculated by the following equation. Phase θF1Tn = Phase θF1n−Phase θCn (n: 01 to 12) (1) According to the above equation, the phase θF1T01 of the multicore optical fiber F1 is obtained.
When the phase θF1T12 is calculated, for example, the phase θF1
The phase difference PθF1 based on T12 is obtained by the following equation. Phase difference PθF1n = Phase θF1Tn−Phase θF1T12 (n: 01 to 12) (2) (The phase difference PθF112 of the twelfth center is naturally zero.)

Similarly, for the multi-core optical fibers F2 to F4, the phases θF201 to θF201 to
While detecting the phase θF212, the phase θF301 to the phase θF312, and the phase θF401 to the phase θF412,
The phases of the multi-core optical fibers F2... F4 themselves are calculated by the equation (1), and the phases θF1T01 to θF4T12 are obtained.

Then, for each of the multi-core optical fibers F2... F4, the phase difference PθF201 to the phase difference PθF212, the phase difference P
θF301 to phase difference PθF312 and phase difference PθF4
01 to calculate the phase difference PθF412. Thus, the phase difference between the optical fibers is detected for each of the multi-core optical fibers (step S1).

Here, the frequency output from the measuring device 6 is represented by f
Then, the relationship between the phase difference Pθ and the transmission time difference T is
It is expressed by the following equation. T = (Pθ / 360) × (1 / f), (−180 ° ≦ Pθ ≦ 180 °) (3) In equation (3), for each of the multi-core optical fibers F1... F4 calculated in step S1 By substituting the phase difference, the transmission time difference for each of the multi-core optical fibers F1... F4 is calculated (step S2). The frequency f depends on the performance of the measuring device. , 10-3000
It can measure up to MHz.

Subsequently, as shown in FIG. 4, the transmission time difference between the multi-core optical fibers F1 to F4 is measured. Here first,
It is verified whether the lengths of these multi-core optical fibers F1 to F4 are within the measurable range. Multi-core optical fiber F1 ... F4
The relationship between the length error D, the transmission time difference T, and the refractive index N is expressed by the following equation. D = T × (C / N) (C: speed of light) (4)

Then, the frequency f = 10 MHz and C = 30
If 0000 km / s and N = 1.465, equation (3)
And from equation (4), -10.24m ≦ D ≦ 10.24m
And the length of the multi-core optical fibers F1... F4 is 20.5 m.
These phase differences can be measured if they are suppressed within the error range of Since the error of a general length measuring instrument is about 50 cm, it can be confirmed that the error is within the measuring range.

In FIG. 4, reference numerals 17 and 18
Is a conversion code. The conversion cord 17 is connected at one end to the fan-out cord 9 by the MT connector 8 and at the other end to the multi-core optical fibers F1 to F4 by the MT connectors 19a to 19d. The MT connectors 19a... 19d and the multi-core optical fibers F1... F4 are respectively connected by three cores, for example, the fourth core, the eighth core and the twelfth core.

Similarly, the conversion cord 18 is connected at one end to the fan-out cord 10 by the MT connector 8 and at the other end to the multi-core optical fibers F1... F4 by the MT connectors 20a. The MT connectors 20a... 20d and the multi-core optical fibers F1... F4 are respectively connected by three cores, for example, the fourth core, the eighth core, and the twelfth core.

In this state, by operating the control unit 14 to switch the fiber selectors 11 and 12, the phases θF104, θF108, θF112,
Phase θF204, θF208, θF212, phase θF3
04, θF308, θF312 and phase θF404,
.theta.F408 and .theta.F412 are detected, and the phases of the multi-core optical fibers F1...
The phase θF1T04 to the phase θF4T12 are obtained.

Here, it is confirmed that the relative relationship between the phases θF1T04 to θF4T12 matches the relative relationship between the phases detected one by one in advance. Then, based on the obtained phase θF4T12, that is, the phase of the twelfth optical fiber of the multicore optical fiber F4,
Phase difference PθF1 between phase θF1T04 to phase θF4T12
04 to detect the phase difference PθF412. Thereby, the phase difference between the multi-core optical fibers F1 to F4 is detected (step S3).

Then, by substituting the phase difference between the multi-core optical fibers F1 to F4 detected in step S3 into the above equation (3), the twelfth optical fiber of the multi-core optical fiber F4 is used as a reference. The transmission time difference between the multi-core optical fibers F1 to F4 is calculated (step S4).

Subsequently, all of the transmission time differences for each of the multi-core optical fibers F1... F4 calculated in step S2 are multiplied based on the transmission time differences between the multi-core optical fibers F1. The optical fiber of the twelfth core of the core optical fiber F4 is converted into a transmission time difference with the same reference (step S5).

Next, the length of each of the multi-core optical fibers F1... F4 to be adjusted is determined based on the transmission time difference converted on the same basis. First, an average value of the maximum value and the minimum value of the transmission time difference is calculated for each of the multi-core optical fibers F1 to F4 (step S6).

Here, when the average value of each multi-core optical fiber Fn (n = 1 to 4) calculated in step S6 is Sn, and the multi-core optical fiber F4 is a reference fiber having the shortest length. The cut length L for minimizing the transmission time difference between two multi-core optical fibers is obtained by the following equation. L = (Sn−S4) × (C / N) (5)

Therefore, by sequentially substituting the average values S1 to S4 of the transmission time differences in the multi-core optical fibers F1 to F4 into the equation (5), the cut lengths L1 to L4 of the multi-core optical fibers F1 to F4 are determined. It is calculated (step S7). (L4
Is naturally zero. )

The multi-core optical fibers F1... F4 are cut based on the cut lengths L1... L4 calculated in step S7 (step S8), so that the multi-core optical fibers F1. Its length will be adjusted to minimize skew.

<Embodiment> Here, the multi-core optical fibers F1.
Are adjusted in length according to the above procedure. First, as shown in FIG. 5, the frequency f output from the measuring device 6 is set to 2000 MHz, and the first
The transmission time difference based on the second optical fiber, that is, the skew was determined. As shown in FIG.
The skew between the tape 4 was about 30 ps at the maximum.

Next, as shown in FIG.
MHz, 30MHz, 100MHz, and tape 1
切断 Cutting lengths L1 to L4 were calculated for each tape 4. And
FIG. 7 shows the result of cutting the tapes 1 to 4 based on the results and measuring the skew again. As shown in this figure, the skew between the tapes 1 to 4 was reduced to a maximum of 14.4 ps even when the frequency f was changed variously.

In the optical transmission line and the optical transmission line forming method according to the present embodiment, even when an optical transmission line is formed by using a plurality of multi-core optical fibers and optical parallel transmission is performed on this optical transmission line, each of the optical transmission lines is formed in advance. Since the length of the multi-core optical fiber is adjusted by cutting, the transmission time difference generated between the multi-core optical fibers can be reduced.

Also, when adjusting the length of each multi-core optical fiber according to the transmission time difference, it is based on the average value of the maximum value and the minimum value of the transmission time difference generated in each multi-core optical fiber. In addition, the fluctuation width of the transmission time difference between the adjusted multi-core optical fibers can be minimized. Therefore, if the optical transmission line according to the present invention is used, the speed at the time of data transmission can be increased because the transmission time difference is short.

In the above embodiment, a multi-core optical fiber is arranged in a slot groove to form a cable as an optical transmission line. However, the present invention is not limited to this. Or a multi-core optical fiber may be provided in a loose tube. Further, the optical transmission path includes a body, a connecting portion between optical wiring boards arranged in a housing, and the like.

Although the optical transmission line has a configuration having four multi-core optical fibers, the number is not limited as long as the number is plural. In the above-described embodiment, the reference of the phase difference is set to the twelfth fiber for convenience, but is not limited to this. Further, the configuration is such that three cores of the multi-core optical fiber are connected by the conversion cord, but the configuration is not limited to this configuration as long as at least one core is connected.

[0051]

As described above, in the optical transmission line according to the first aspect, in an optical transmission line in which optical parallel transmission is performed by a plurality of multi-line waveguides, the length of each multi-line waveguide is multi-line. The configuration is adjusted based on the transmission time difference between the waveguides. Thus, in this optical transmission line, even when performing optical parallel transmission, the transmission time difference between multi-core optical fibers, which is a multi-line waveguide, is short, so that the data transmission speed, that is, the communication speed, can be increased. The effect that it can be obtained is obtained.

According to a second aspect of the present invention, in the method for forming an optical transmission line using a plurality of multi-core optical fibers, the method comprises the steps of: detecting a transmission time difference between the multi-core optical fibers;
The length of each multi-core optical fiber is adjusted based on the transmission time difference. As a result, in this optical transmission line forming method, an optical transmission line with a short transmission time difference between multi-core optical fibers can be formed even when performing optical parallel transmission, so that the communication speed during communication can be increased. Can be

According to a third aspect of the present invention, in the optical transmission line forming method, the transmission time difference between the multi-core optical fibers is determined by detecting the transmission time difference generated for each multi-core optical fiber, and then detecting the maximum value and the minimum value of the transmission time difference. Is calculated based on the average value of As a result, in this optical transmission line forming method, even when performing optical parallel transmission, an optical transmission line with a minimum transmission time difference between multi-core optical fibers can be formed, so that the communication speed during communication can be increased. can get.

[Brief description of the drawings]

FIG. 1 is a diagram illustrating an embodiment of the present invention, and is a flowchart illustrating a method of adjusting the length of a multi-core optical fiber based on a transmission time difference between the multi-core optical fibers.

FIG. 2 is a view showing an embodiment of the present invention, and is an external perspective view of an optical transmission line having a plurality of multi-core optical fibers whose length is adjusted based on a transmission time difference.

FIG. 3 is a diagram illustrating an embodiment of the present invention, and is a schematic configuration diagram illustrating a skew measurement system.

FIG. 4 is a diagram illustrating an embodiment of the present invention, and is a schematic configuration diagram illustrating a skew measurement system.

FIG. 5 is a diagram showing the embodiment of the present invention, and is a table showing skew before length adjustment.

FIG. 6 is a table showing a tape cutting length calculated by the optical transmission path forming method of the present invention.

FIG. 7 is a table showing skew in the optical transmission line of the present invention.

[Explanation of symbols]

1: optical transmission line (optical cable), F, F1,..., F4: multi-core optical fiber (optical fiber ribbon).

 ──────────────────────────────────────────────────続 き Continuing on the front page (72) Inventor Tsutomu Watanabe 1440 Mutsuzaki, Sakura City, Chiba Prefecture Inside Fujikura Sakura Factory (72) Inventor Nobuaki Matsuura 3-19-2 Nishishinjuku, Shinjuku-ku, Tokyo Nippon Telegraph and Telephone Nippon Telegraph and Telephone Co., Ltd. (72) Inventor Yasuhiro Ando

Claims (3)

[Claims] An optical transmission line (1) in which optical parallel transmission is performed by a plurality of multi-line waveguides (F1 to F4), wherein each of the multi-line waveguides has a transmission time difference between the multi-line waveguides. An optical transmission line having a length adjusted on the basis of: 2. A method for forming an optical transmission line using a plurality of multi-core optical fibers, comprising: detecting a transmission time difference between the multi-core optical fibers; and detecting the transmission time difference based on the detected transmission time difference. An optical transmission line forming method, comprising adjusting the length of a multi-core optical fiber. 3. The optical transmission line forming method according to claim 2, wherein the transmission time difference between the multi-core optical fibers is determined by detecting the transmission time difference generated for each of the multi-core optical fibers. An optical transmission line forming method, wherein the optical transmission line forming method is calculated based on an average value of the maximum value and the minimum value.