JP3063337B2 - Active coupler and optical signal amplification method using the same - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an active coupler used in an optical data link system and an optical signal amplification method using the same.

[0002]

FIG. 13 is a schematic diagram showing an example of an optical data link system as a background art of the present invention. In this optical data link system, as shown in the figure, four terminals A to D are interconnected by a 4 × 4 channel star coupler SC. That is, the star coupler SC is provided with four input channels,
They are respectively connected to the transmission section TX _A ~TX _D terminal to D. Further, the output channel is provided four, are connected to the receiver unit RX _A to Rx _D terminal to D.

For this reason, when an optical signal PS is transmitted from a certain terminal, for example, a terminal A, the optical signal PS is not only received at each of the terminals BD but also received at the terminal A. can do.

FIG. 14 shows an example of a star coupler SC having the above function. As shown in the figure, in this star coupler SC, the mixing rod 1
A large number of plastic fibers 2 and 3 at both ends 1a and 1b
Are optically coupled. Therefore, when an optical signal related to predetermined information is input to one of the plastic fibers 2, the optical signal related to the information is branched and output from each plastic fiber 3. That is, in the star coupler SC, the plastic fiber 2 functions as an input channel, and the plastic fiber 3 functions as an output channel.

[0005]

By the way, in the above conventional example, the star coupler SC is formed by the mixing rod 1 and the plastic fibers 2 and 3 having different thermal expansion coefficients.
Therefore, when the ambient temperature of the star coupler SC changes, the characteristics of the star coupler SC change greatly. This is because the rate of expansion (or contraction) of the mixing rod 1 due to the change in the ambient temperature is different from that of the plastic fibers 2 and 3. Further, since the mixing rod 1 and the plastic fibers 2 and 3 are merely optically coupled, a large loss occurs at the coupling portion, and the star coupler S
When vibration is applied to C, there may be a problem that the plastic fibers 2 and 3 are shifted with respect to the mixing rod 1 and are shifted from the mixing rod 1. Further, when the distance between the terminals A to D is widened and long-distance optical communication is required, an intermediate amplifier must be further provided in a part of the optical data link system.

In view of the above situation, an active coupler shown in FIG. 15 has been proposed. In this 4 × 4 channel active coupler, photoelectric converters 5a, 5b, 5c and 5d are provided corresponding to the input channels. For example, when the optical signal PS from the terminal A is input to the photoelectric converter 5a, the light The signal PS is converted into an electric signal ES and supplied to the amplifier 6. After this electric signal ES is amplified by the amplifier 6, each of the photoelectric converters 7a, 7b,
7c and 7d, and are reconverted into an optical signal PS '.
Thus, the weak optical signal PS is amplified, and the amplified optical signal PS 'is output to each of the terminals A to D via each of the photoelectric converters 7a, 7b, 7c, 7d.

However, the active coupler (FIG. 15) configured as described above has the following problems.
That is, assuming that the number of channels is n, 2 · n photoelectric converters are required, and the cost of the active coupler increases. Further, if the power supply to the amplifier 6 is interrupted or the amplifier 6 itself breaks down, optical communication within the optical data link system cannot be performed, and there is a problem that reliability is lacking.

SUMMARY OF THE INVENTION An object of the present invention is to solve the above-mentioned problems and to provide an active coupler which has high reliability, enables long-distance communication, has low cost and low loss, and an optical signal amplification method using the same. The purpose is to provide.

[0009]

Means for Solving the Problems of claims 1 invention, in order to achieve the above object, in a two plug tic fiber
An optical branch portion formed by welding the intervening portions to each other; and a second optical branch portion extending from one end of the optical branch portion functioning as an input channel .
First and second input fiber ends, and first and second ends extending from the other ends of the optical branching portions functioning as output channels.
A plurality of optical elements comprising the second output fiber end ;
A 2 ⁿ × 2 ^n- channel star coupler section configured in combination, a signal extraction fiber end functioning as a signal extraction section of the output fiber end section of the star coupler section, and an amplification section of the input fiber end section The star coupler is connected to an amplified signal introduction fiber end functioning as a signal introduction, amplifies a signal from the signal extraction fiber end, and amplifies the amplified signal through the amplified signal introduction fiber end. And a signal amplifying unit for inputting to the unit , wherein the signal amplifying unit is operating
In this case, the optical signal is amplified to perform optical communication, while the signal
When the width unit is stopped, the light signal is amplified.
Optical communication without using

[0010] According to a second aspect of the invention, the star coupler unit, the light distribution ratio of the previous SL light branching part r: the optical element is a ^{(1-r), 2 n} × constructed by combining a plurality 2
^{An n-} channel star coupler unit, and the signal extraction fiber end is a fiber end that minimizes optical output when an optical signal is input to the amplified signal introduction fiber end of the output fiber end. .

According to a third aspect of the present invention, the active coupler of the second aspect satisfies an inequality represented by 0.5 ≦ r ≦ 0.518.

According to a fourth aspect of the present invention, the signal amplifying unit comprises: a first photoelectric converter for converting an optical signal from the end of the signal extracting fiber into an electric signal; and the first photoelectric converter with an arbitrary amplification factor. An amplifier circuit for amplifying an electric signal from the device and a second photoelectric converter for converting an amplified signal output from the amplifier circuit to an optical signal.

According to a fifth aspect of the present invention, there is provided an optical signal amplifying method using the active coupler according to the first aspect of the present invention. An optical signal is input to an arbitrary fiber end different from the above, and the optical signal is distributed and output to the output fiber end, and an optical signal is input to the amplified signal introducing fiber end of the output fiber end. Then, an optical signal is taken out from the end of the fiber where the optical output becomes minimum, and after amplifying the optical signal, the amplified optical signal is input to the end of the fiber for introducing an amplified signal, and the amplified light The signal is further distributed and output.

[0014]

According to the first aspect of the present invention, the signal from the signal extraction fiber end is amplified by the signal amplifying unit and then returned to the star coupler via the amplified signal introduction fiber end. At this time, if the signal amplification unit is
Amplifying the optical signal when performing optical communication
Optical communication becomes possible. Meanwhile, the power to the signal amplification unit
When the supply is stopped and the signal amplification unit is stopped
Optical communication without amplifying the optical signal,
Although the bell is low, optical communication itself is possible.

According to the second aspect of the present invention, the star coupler section is constituted by combining a plurality of optical elements having a light distribution ratio r: (1-r), and the signal extraction fiber end is an amplification section of the output fiber end. Since the optical output is minimized when an optical signal is input to the end of the signal introducing fiber, the optical signal can be output from each output fiber end most efficiently.

According to the third aspect of the present invention, since the active coupler of the second aspect satisfies the inequality represented by 0.5 ≦ r ≦ 0.518, the light intensity from the end of the output fiber is substantially reduced. Be even.

According to the fourth aspect of the present invention, the optical signal from the end of the signal extraction fiber is converted into an electric signal, further amplified by an amplifier circuit at an arbitrary amplification factor, and then converted again into an optical signal, and then converted into a star coupler. Returned to the department.

According to the fifth aspect of the present invention, an optical signal is input to an arbitrary fiber end of the input fiber end that is different from the amplified signal introduction fiber end, and is distributed and output to the output fiber end. . Further, when an optical signal is input to the amplified signal introducing fiber end of the output fiber end, an optical signal is extracted from the fiber end where the optical output is minimized, and after being amplified, the amplified optical signal is The signal is input to the end of the amplified signal introducing fiber. Therefore, not only the distributed optical signal but also the amplified optical signal is further distributed and output to the output fiber end, and the optical signal from each output fiber end is amplified.

[0019]

FIG. 1 is a diagram showing a first embodiment of the active coupler according to the present invention. The active coupler, as shown in the figure, and 2 ³ × 2 ^3-channel star coupler unit 10, and a signal amplifier unit 20. The star coupler unit 10 is formed as described below, and includes eight input fiber ends 11a to 11h functioning as input channels, eight output fiber ends 12a to 12h functioning as output channels, and one And an optical branching unit 13 for distributing the optical signal input to the end of the input fiber into eight optical signals and outputting the same to the output fiber ends 12a to 12h.

The signal amplifying unit 20 is composed of two photoelectric converters 21 and 23 and an amplifier 22. In the signal amplification unit 20, the photoelectric converter 21 is connected to the output fiber end 12h, the optical signal PH _h from the output fiber end 12h by the photoelectric converter 21 is converted into an electric signal, an amplifier 22 Is entered. The amplified electrical signal amplified by the amplifier 22 is supplied to the photoelectric converter 23, converted into an optical signal PH _m, via the input fiber end 11h light branching section 13
Is input to Thus, a positive feedback loop is formed by the output fiber end 12h, the signal amplification unit 20, and the input fiber end 11h.

Next, prior to the description of the operation of the active coupler, an example of a manufacturing procedure of the star coupler unit 10 will be described with reference to FIGS. 2 to 7 to clarify the features of the structure.

First, two plastic fibers F ₁ ,
The F ₂ parallel arranged as shown in FIG. Then, the intermediate portions (regions surrounded by dotted lines) of the plastic fibers F ₁ and F ₂ are welded to each other over a predetermined length L. As a welding method, for example, the present applicant has filed a prior application (Japanese Patent Application No. 2-17 / 1990).
No. 554) discloses an ultrasonic welding method.

[0023] Thus, as shown in FIG. 3, an optical branching part 15, while the plastic fibers F ₁ from the end, F ₂ in the longitudinal extending direction X fiber end 11a of the optical splitter 15, and 11b, the other end And fiber ends 16a, 16b extending in the direction X from. In the 2 × 2 channel star coupler 30 thus manufactured, for example, when an optical signal PH is input to the fiber end 11a, the optical signal PH is transmitted to the fiber end 16a facing the fiber end 11a.
The signals are branched and output from a and 16b at a distribution ratio of r: (1-r).

Next, the 2 × 2 manufactured as described above
The channel star couplers 30A and 30B are prepared, and the 2 × 2 channel star couplers 30A and 30B are arranged in parallel (FIG. 4). Then, the star couplers 30A, 30
The intermediate portions of the fiber ends 16a and 16d of B and the intermediate portions of the fiber ends 16b and 16c are welded to each other (FIG. 5). Thus, 2 ^two input fiber ends 11a serving as an input channel, 11b, 11c,
And 11d, 2 ² output fibers ends 17a which functions as an output ^{channel, 17b, 17c, 2 2 ×} 2 2 -channel star coupler 40 and a 17d is formed.

Further, the 2 ² produced as described above
A × 2 ^two- channel star coupler 40A, 40B is prepared, and the star couplers 40A, 40B are arranged in parallel (FIG. 6). The middle portions of the fiber ends 17a and 17f, the middle portions of the fiber ends 17b and 17e, the middle portions of the fiber ends 17c and 17h, and the middle portions of the fiber ends 17d and 17g. They are mutually welded (FIG. 7). Thus, the eight input fiber ends 11a to 11h and the eight output fiber ends 12a
To 12h and an optical branching unit 1 including 12 optical branching units 15
3 is formed.

Next, returning to FIG. 1, the operation of the active coupler will be described. Here, the input fiber end 1
1a, an optical signal PH is input to the output fiber ends 12a to 12a.
A case where an optical signal is output from 12g will be described.

The optical signal PH input to the input fiber end 11a is distributed by the optical splitter 13 at an appropriate distribution ratio, and then transmitted to the output fiber ends 12a to 12h. When the power supply to the amplifier 22 is stopped and the signal amplification unit 20 is not operating (hereinafter, referred to as “passive state”), the output fiber ends 12 a to 12 g
Is output as it is. On the other hand, when the signal amplifying unit 20 is operating (hereinafter, referred to as “active state”), the optical signal is amplified as described below and output from each of the output fiber ends 12a to 12g.

[0028] That is, a portion PH _h of input to the input fiber end 11a the optical signal PH is output fiber end 12
h. For the sake of convenience in the following description, the fiber end having the function of extracting a part of the input optical signal PH from the star coupler unit 10 as described above, that is, in this embodiment, the fiber end 12h is referred to as a “signal extraction fiber end”. Unit ". In the active state, the optical signal PH from the signal extraction fiber end 12h
_h is converted into an electric signal by the photoelectric converter 21 and further amplified by the amplifier 22. The amplified electrical signal is input to the photoelectric converter 23, is converted into an optical signal PH _m. Synchronous optical signal PH _m thus created is returned to the star coupler unit 10 further through the input fiber end 11h. Incidentally, it referred thus the amplified optical signal PH _m fiber end portion having a function of returning to the star coupler unit 10, i.e. the "amplified signal introducing fiber ends" the fiber ends 11h in this embodiment.

The optical signal PH _m each output fiber ends are distributed at an appropriate distribution ratio by the light branching portion 13 12A～12
h. Therefore, each output fiber end 12a
Optical signal output from the ~12g includes a signal output by distributing the optical signal PH, the sum of the signals output by distributing the synchronization optical signal PH _m, which is re-entered, the output level becomes higher .

Next, a specific example of an active coupler made of uncrosslinked polymethyl methacrylate-based plastic fiber will be shown, and its characteristics will be described.

The inventor of the present application formed each light splitting portion 15 by ultrasonic welding under the following conditions in order to manufacture the star coupler section 10 by ultrasonic welding. That is, the conditions are as follows: (pressing force) = 10 kgf (vibration frequency) = 15 kHz (vibration amplitude) = 40 μm (vibration application time) = 0.5 second (length of the light splitting section 15) L = 20 mm.

Then, using an optical power measurement system, the characteristics of the active coupler having the star coupler section 10 manufactured by the ultrasonic welding method were evaluated in the active state and the passive state, respectively. In particular,
Red light (light intensity P _I = 15.4 μW) having a wavelength of 660 nm emitted from the light source of the optical power measurement system is input to the input fiber end 11a of the star coupler unit 10 and emitted from the output fiber ends 12a to 12g. the light received directly is, the output value P _a to P _g of the output fiber ends 12a~12g were measured.

As a result, in the passive state, the output value P _a
~P _g each 1.32μW, 1.33μW, 1.28 μW,
1.30 μW, 1.20 μW, 1.35 μW, 1.50 μW.
The excess loss LS in this case is LS = −10 · log ((1.32 + 1.33 + 1.28 + 1.30 + 1.20 + 1.35 + 1.50) /15.4) = 2.19 (dB), and the average value of the insertion loss is 10.73. (dB).

[0034] On the other hand, in the active state, the output value P _a ~
P _g is 2.51 μW, 2.55 μW, 2.54 μW, 2.
The values were 47 μW, 2.34 μW, 2.55 μW, and 2.97 μW. The average value of the insertion loss was 7.82 (dB). At this time, the current consumption of the amplifier 22 was about 35 mA.

[0035] As described above, in the active coupler according to this embodiment, taking out a portion PH _h of the optical signal PH input to the star coupler unit 10, after amplifying, a star coupler portion its synchronous optical signal PH _m 10, the output level of the optical signal from the star coupler unit 10 increases, and long-distance optical communication becomes possible. Further, even when the power supply to the signal amplification unit 20 is stopped, the active coupler is in a passive state, and although its output level is lower than the output level in the active state, optical communication itself is possible.

The number of photoelectric converters required in this embodiment is always one, regardless of the number of channels. Therefore, the cost of the active coupler can be kept low. Further, the active coupler can be operated with low power consumption.

Further, according to this embodiment, since the star coupler section is constituted only by the plastic fiber, the coefficient of thermal expansion in each section of the star coupler section is uniform. Therefore, even if the temperature of the use environment of the active coupler changes, each part expands (or contracts) at the same rate. As a result, the characteristic change of the active coupler due to the temperature change is reduced. Further, since the light branching portions 13 of the star coupler portion 10 are all welded, a sufficient strength is obtained in the light branching portion 13 (15).

In the above embodiment, any one of the input fiber ends 11a to 11h (fiber end 11h in the embodiment) is used as an amplified signal introducing fiber end, and similarly, the output fiber end is used. Any one of the portions 12a to 12h (the fiber end 12h in the embodiment) was used as a signal extraction fiber end. However, from the viewpoint of energy efficiency, it is desirable that most of the optical signal returned to the end of the amplified signal introducing fiber is output from the end of the fiber other than the end of the fiber for taking out the signal. That is, when returning the optical signal PH _m to the fiber end portion for amplifying signals introduced, each output fiber ends 12a
It is preferable that the fiber end having the lowest output level of the signal output to 12h be the fiber end for signal extraction.

For example, consider the star coupler unit 10 (FIG. 7) formed as described above. As shown in FIG. 8, the energy value of the input fiber end 11h is 1
When the optical signal of 00 is input, when the distribution ratio of each optical branching unit 15 is 1: 1.4, each of the output fiber ends 12a to 12h
Output energy values are 14.4, 21.6, and 9.6, respectively.
, 14.4, 6.4, 9.6, 9.6, and 14.4, and the fiber end 12e is the smallest. Therefore, if the input fiber end 11h is an amplified signal introducing fiber end, it is preferable that the output fiber end 12e be a signal extraction fiber end correspondingly. The relationship between the distribution ratio and the light intensity from the end of each output fiber will be described in detail later. Therefore, the fibers 11h and 12e of the star coupler 10 manufactured as described above must be connected to the signal amplification unit 20. The characteristics of the active coupler formed by the method were verified. That is, red light (wavelength P _I = 26.4) having a wavelength of 660 nm emitted from the light source of the optical power measurement system.
μW) to the input fiber end 11 of the star coupler unit 10.
Input to a. On the other hand, the output fiber ends 12a, 12a
b, 12c, 12d, 12f, 12g, and directly receives light emitted from 12h, the output value _{P a, P b, P c} , P
_d, was measured P _f, P _g, the P _h, respectively.

[0040] As a result, in the passive state, the output value _{P a, P b, P c} , P d, P f, P g, P h , respectively
2.49μW, 3.42μW, 2.16μW, 2.61μW, 1.90μW,
1.69 μW and 2.36 μW. The excess loss LS in this case is LS = −10 · log ((2.49 + 3.42 + 2.16 + 2.61 + 1.90 + 1.69 + 2.36) /26.4) = 2.01 (dB), and the average value of the insertion loss is 10.46. (dB).

On the other hand, in the active state, the output values P _a ,
_{P b, P c, P d} , P f, P g, P h each 4.05μ
W, 5.20μW, 5.03μW, 5.59μW, 3.45μW, 3.86μ
W, 4.45 μW. The average insertion loss is 7.67
(dB). At this time, the current consumption of the amplifier 22 was about 35 mA.

The characteristics of another active coupler manufactured in the same manner were verified. That is, the red light of 660 nm wavelength emitted from the light source of the optical power measuring system (light intensity P _I =
26.4 μW) is input to the input fiber end 11 a of the star coupler unit 10. On the other hand, the output fiber ends 12a, 1
2b, 12c, 12d, 12f, 12g, and directly receives light emitted from 12h, the output value _{P a, P b, P c} ,
_{P d, P f, P g} , the P _h was measured, respectively.

[0043] As a result, in the passive state, the output value _{P a, P b, P c} , P d, P f, P g, P h , respectively
3.42μW, 2.49μW, 1.90μW, 2.36μW, 1.69μW,
2.16 μW and 2.61 μW. The excess loss LS in this case is LS = −10 · log ((3.42 + 2.49 + 1.90 + 2.36 + 1.69 + 2.16 + 2.61) /26.4) = 2.01 (dB), and the average value of the insertion loss is 10.46. (dB).

On the other hand, in the active state, the output values P _a ,
_{P b, P c, P d} , P f, P g, P h each 5.20μ
W, 4.05μW, 3.45μW, 4.45μW, 3.86μW, 5.59μ
W, 5.03 μW. The average insertion loss is 7.67
(dB). At this time, the current consumption of the amplifier 22 was about 35 mA.

Next, the relationship between the distribution ratio and the light intensity from the end of each output fiber will be discussed. Now, it is assumed that the distribution ratio of the optical branching unit 15 of the star coupler unit 10 in FIG.
Let us consider the case of inputting to a. In this case, if there is no excess loss, each of the output fiber ends 12a to 12a
The light intensity from 12h is, as shown in FIG.
^{3, (1-r) r} 2, (1-r) r 2, r (1-
r) ² , r (1-r) ² , (1-r) ³ , (1-r) r
² , r (1−r) ² . That is, it is understood that the output level of the output fiber end 12f is the lowest, and it is optimal to use this as the signal extraction fiber end.

Then, the optical signal from the signal extraction fiber end 12f is amplified to a light intensity of 1, and the amplified optical signal is returned to the amplified signal introduction fiber end (input fiber end) 11a. The optical signal is distributed by the star coupler unit 10, and the signal extraction fiber end 12f
Output fiber ends 12a to 12e, 12g, 12
h, the light intensities are r ³ , (1-r) r ² , and (1-
^{r) r 2, r (1} -r) 2, r (1-r) 2, (1-
^{r) r 2, r (1} -r) 2 of the optical signal is added, the output fiber end 12a to 12e, 12 g, the output level of 12h increases. Here, in the passive state and the active state, each output fiber end 12a to 12e, 1
The following table summarizes the intensities of the optical signals output from 2g and 12h.

[0047]

[Table 1]

In Table 1, "PORT" indicates the end of the fiber, and the upper part of each column indicates the light intensity in the passive state.
The light in the lower bracket indicates the light intensity in the active state. The symbols A to D mean A: r ³ B: (1-r) r ² C: r (1-r) ² D: (1-r) ³ . As described above, since r ≧ 0.5, the magnitude relation between these values is r ³ > (1-r) r ² > r (1-r) ² > (1-r) ³ , so that In the state, the maximum value of the light intensity is “A + A”, that is, r ³ + r ³ , while the minimum value is “C + D or D + C”, that is, r (1-r) ² + (1-r) ³ . Therefore, the maximum value of the light intensity ratio f (r) becomes ^{f (r) = (r 3} + r 3) / {r (1-r) 2 + (1-r) 3}. This light intensity ratio f (r) is a function of the value r, and the relationship between them is shown in FIG.

By the way, in the technical field (plastic fiber) of the present invention, when the output difference is within 1 dB, it is considered that the optical signal is evenly distributed by the active coupler. Therefore, in order to satisfy this condition, it is necessary to design so that the light intensity ratio f (r) satisfies 1 ≦ f (r) ≦ 1.2. That is, the value r
May be set to 0.5 ≦ r ≦ 0.518, that is, the distribution ratio of the light branching portion 15 may be set to 1: 1 to 1.07: 1.

The optical signal P from the star coupler 10 is
When the time from extraction of H _h to re-input to the star coupler unit 10 of the synchronous optical signal PH _m long, there is a pulse waveform of the optical signal output from the output fiber end is largely deformed. Therefore, it is desirable that the optical waveguide path of the positive feedback loop composed of the signal extraction fiber end, the signal amplification unit 20 and the amplified signal introduction fiber end be the shortest distance.

Incidentally, an optical receiving module (not shown) connected to each output fiber end and receiving an optical signal from each output fiber end has a dynamic range. The dynamic range refers to a range from a minimum level at which a receiving element provided in the optical receiving module can detect incident light to a maximum level before the element reaches saturation. Therefore, it is necessary to adjust the output level from the end of the output fiber within the dynamic range when designing the optical data link system or after constructing the system. In particular, there has been a long-awaited need for level adjustment after system construction, but none of the conventional examples satisfy such a demand. Therefore, the inventor of the present application has proposed the amplification unit 2 of the active coupler shown in FIG.
0 was constructed as follows, and an active coupler capable of satisfying the above demand was invented.

FIG. 11 is a block diagram showing an improved example of the signal amplifying unit. In this improved signal amplifying unit 20 ', as shown in FIG.
h and is connected, an optical signal PH _h from the fiber end 12h is converted into an electric signal.

The electric signal is input to an input limiting circuit 26.
And the voltage value is converted so as to take a value within a voltage range in which the voltage amplification amplifier 27 operates linearly. Subsequently, after the amplification process by the amplification amplifier 27 is performed, the signal is input to the drive circuit 28. In the driving circuit 28, current amplification is performed based on the input signal, drives the photoelectric conversion circuit 29 converts the electrical signal into an optical signal PH _m.

The signal amplification unit 20 'according to this improvement
Is configured as described above, and the amplification factor of the amplification amplifier 27 can be changed. Therefore, even after that before or incorporate incorporate active coupler system of varying the level of the optical signal PH _m optical signal output from the active coupler from unit 20 'by causing the amplification factor is changed in the amplifier 27 The output level can be easily adjusted.

In the above embodiment, the star coupler 1
Although an example using a 2 ³ × 2 ³ channel star coupler as 0 has been described, the present invention is not limited to this.
The 2 ² × 2 ^2- channel star coupler shown in FIG. 5 may be used. Further, nx formed by mutually welding the intermediate portions of n (n ≧ 3) plastic fibers over a predetermined length.
An n-channel type may be used. Further, as shown in FIG. 12, a plurality of plastic fibers F _{1 to} F ₈ are arranged in a branched manner from the upstream side (the left-hand side in the figure) to the downstream side (the right-hand side in the figure). A 2 × 8 channel star coupler welded in the part B may be used. Further, an 8 × 2 channel star coupler may be formed in the same manner as described above and used. In short,
By welding a plurality of plastic fibers to each other, m (m ≧ 2) input fiber ends functioning as input channels and n functioning as output channels
The star coupler unit 10 is constituted by an optical element having n (n ≧ 3) output fiber ends, or conversely, an optical element having n input fiber ends and m output fiber ends. I just need.

[0056]

According to the first and second aspects of the present invention, a signal extracting fiber end functioning as a signal extracting end of the output fiber end of the star coupler section and an amplified signal introducing end of the input fiber end are provided. After connecting the amplified signal introducing fiber end functioning as a signal amplifying unit and amplifying the optical signal from the signal extracting fiber end, the star coupler section through the amplified signal introducing fiber end. To be entered. At this time,
When the width unit is operating, the light signal is amplified to
By performing communication, long-distance optical communication becomes possible. On the other hand,
Power supply to the signal amplification unit
When the power is off, the optical signal is not amplified
Communication, the output level is reduced, but optical communication
It is possible. Further, regardless of the number of channels, necessary photoelectric converter for converting the one and, the electrical signal amplified for converting an optical signal into an electrical signal from said signal extraction fiber ends to the optical signal Therefore, the cost of the active coupler can be reduced.

According to the invention of claim 3, since the active coupler of claim 2 is configured to satisfy the inequality represented by 0.5 ≦ r ≦ 0.518,
The light intensity from the output fiber end can be made substantially uniform.

According to the fourth aspect of the present invention, the configuration is such that the amplification factor of the optical signal can be arbitrarily converted, so that the versatility of the active coupler is enhanced.

Further, according to the fifth aspect of the present invention, an optical signal is input to an arbitrary fiber end of the input fiber which is different from the amplified signal introducing fiber end, and the optical signal is input to the output fiber end. Along with distributing and outputting, when an optical signal is input to the amplified signal introducing fiber end of the output fiber end, an optical signal is taken out from the fiber end where the optical output is minimized, and the optical signal is amplified. Since the amplified optical signal is input to the end of the amplified signal introduction fiber and the amplified optical signal is further distributed and output to the output fiber end, the output level of the optical signal from the star coupler increases. The same effects as those of the first aspect can be obtained.

[Brief description of the drawings]

FIG. 1 is a diagram showing one embodiment of an active coupler according to the present invention.

FIG. 2 is a diagram illustrating a manufacturing procedure of a star coupler unit.

FIG. 3 is a diagram showing a procedure for manufacturing a star coupler unit.

FIG. 4 is a diagram showing a procedure for manufacturing a star coupler.

FIG. 5 is a diagram showing a manufacturing procedure of a star coupler.

FIG. 6 is a diagram illustrating a manufacturing procedure of a star coupler unit.

FIG. 7 is a diagram showing a manufacturing procedure of the star coupler.

FIG. 8 is a diagram schematically illustrating a light distribution state of a star coupler unit.

FIG. 9 is a diagram showing the relationship between the distribution ratio and the light intensity from each output fiber end.

FIG. 10 is a graph showing a relationship between a distribution ratio and a light intensity ratio.

FIG. 11 is a block diagram illustrating an improved example of a signal amplification unit.

FIG. 12 is a diagram showing a 2 × 8 channel star coupler.

FIG. 13 is a schematic diagram showing an example of a communication network as a background art of the present invention.

FIG. 14 is a diagram showing a conventional star coupler.

FIG. 15 is a diagram illustrating a proposed example of an active coupler.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 10 Star coupler part 11a-11h Input fiber end part 12a-12h Output fiber end part 15 Optical branching part 20 Signal amplification unit 21, 23 Photoelectric converter 22 Amplifier

──────────────────────────────────────────────────続 き Continued on the front page (58) Field surveyed (Int. Cl. ⁷ , DB name) H04B 10/00-10/28 H04J 14/00-14/08 H04L 12/28-12/44 G02F 1 / 29-7/00 G02B 6/28

Claims (5)

(57) [Claims] 1. An intermediate part of two plastic fibers is phased.
An optical branch portion welded to each other, and first and second optical branch portions extending from one ends of the optical branch portion functioning as input channels .
And a plurality of optical elements each including an input fiber end portion and a first and a second output fiber end portion extending from the other end of the optical branch portion functioning as an output channel.
A 2 ⁿ × 2 ^n- channel star coupler section, a signal extraction fiber end section that functions as a signal extraction section of the output fiber end section of the star coupler section, and an amplification section of the input fiber end section. The star coupler is connected to an amplified signal introduction fiber end functioning as a signal introduction, amplifies a signal from the signal extraction fiber end, and amplifies the amplified signal through the amplified signal introduction fiber end. and a signal amplifying unit for inputting the section, the optical signal when said signal amplifying unit is operating
While amplifying and performing optical communication, the signal amplification unit is stopped.
When stopped, optical communication is performed without amplifying the optical signal.
Cormorants active coupler, characterized in that. Wherein said star coupler unit, the light distribution ratio of the previous SL light branching part r: (1-r) of the optical element is a plurality combination 2 is configured by ⁿ × 2 ^n-channel star coupler 2. The signal output fiber end, wherein the signal output fiber end has a minimum optical output when an optical signal is input to the amplified signal introduction fiber end of the output fiber end. Active coupler as described. 3. The active coupler according to claim 2, wherein an inequality represented by 0.5 ≦ r ≦ 0.518 is satisfied. 4. The signal amplification unit converts a light signal from the end of the signal extraction fiber into an electric signal, and an electric signal from the first photoelectric converter at an arbitrary amplification factor. 2. The active coupler according to claim 1, comprising: an amplifier circuit for amplifying the signal; and a second photoelectric converter for converting an amplified signal output from the amplifier circuit into an optical signal. 5. An optical signal amplification method using an active coupler according to claim 1, wherein an optical signal is input to an arbitrary fiber end of the input fiber end that is different from the amplified signal introduction fiber end. And distributes and outputs the optical signal to the output fiber end, and outputs the optical signal from the fiber end where the optical output is minimized when the optical signal is input to the amplified signal introduction fiber end of the output fiber end. Extracting the signal, amplifying the optical signal, inputting the amplified optical signal to the end of the fiber for introducing the amplified signal, and further distributing and outputting the amplified optical signal to the end of the output fiber. Amplification method.