JPH11215058A - Super-wide band wavelength dispersion compensation device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To compensate the wavelength dispersion of a transmission line over a wide band and a dispersion slope. SOLUTION: Signal light obtd. by multiplexing plural different wavelengths is propagated on an input light transmission line 1. To the signal length from the line 1 the primary wavelength dispersion is compensated through a dispersion compensation fiber 2, a wavelength division multiplex (WDM) filter 3 divides this output into a short wavelength (L) band and an long wave length (H) band, and they are inputted to WDM filters 7 and 9 through light circulators 5 and 6 respectively. λ1 to λ8 are grouped and propagated to chirped grating fibers 8a to 8d, which are connected to the filters 7 and 9, and λ9 to λ16 are grouped and propagated to 10a to 10b. A secondary wavelength dispersion compensation is performed on the respective ways from a port (1) to a port (3) of the circulators 5 and 6 and the wavelength dispersion that occurs, when the wavelength multiplex transmission is performed is compensated.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an ultra-wide band chromatic dispersion compensating device for compensating chromatic dispersion of a transmission line for wavelength multiplex communication over a wide band.

[0002]

2. Description of the Related Art In recent years, with the rapid development of optical fiber amplifiers in the 1.55 μm band, high-speed and large-capacity information is transmitted by wavelength multiplex transmission using several to several tens of 1.55 μm band optical signals. Research and development of systems for long-distance transmission have become active. As a configuration method of such a system, a single-mode optical fiber having a zero-dispersion characteristic of 1.3 μm is used for a transmission line, and several to several tens of wavelength-multiplexed signal light in the 1.55 μm band is transmitted therethrough. A method is being considered. When a wavelength-multiplexed signal light is transmitted over a long distance, a problem is chromatic dispersion (the speed of light differs depending on the wavelength).

FIG. 9 shows the relationship between the dispersion state and the propagation distance.
When the pulse-shaped input signal light propagates through the optical fiber, if the dispersion is zero, no change occurs in the waveform output from the optical fiber. However, as the dispersion value increases, the pulse waveform itself of the input signal light collapses and spreads.
When the input signal light propagates in the optical fiber having a large dispersion value over a long distance, the output signal light deteriorates. Therefore, it is necessary to compensate for chromatic dispersion and make the dispersion value zero.
As a method of compensating for the chromatic dispersion of an optical fiber in the 1.55 μm band, a method of adding a dispersion compensating fiber to a wavelength division multiplex transmission line has been proposed. A specific example is disclosed in JP-A-8-2
No. 34255 and JP-A-9-191290.

FIG. 10 shows a first example of a conventional chromatic dispersion compensating device. The optical branching coupler (CPL) 101 has a wavelength λ
₁ inputs the signal light 100-1 are wavelength-multiplexed by to [lambda] _n, the wavelength lambda _1, branches and outputs to each wavelength of λ ₂ ··· ~λ _n. Each of the n output terminals of the optical branching coupler 101 is connected to a band-pass filter (BPF) 102-1 to 102-n that passes only a predetermined wavelength band. Bandpass filters 102-1 to 102
−n, a chromatic dispersion compensator (DC) 103 −
1 to 103-n are connected, and an optical branching coupler (CPL) 104 is connected to these output terminals. The optical splitter 104 outputs a signal light 100-2 obtained by wavelength-multiplexing the wavelengths λ _{1 to} λ _n .

In the configuration shown in FIG. 10, wavelengths λ _{1 to} λ _n are demultiplexed for each wavelength by the optical splitter / coupler 101, and furthermore, wavelengths other than the wavelengths determined by the band-pass filters 102-1 to 102-n are used. The wavelength component is removed. Then, the wavelength dispersion of the transmission line by independently wavelength dispersion compensator 103-1 to 103-n for each optical signal of each wavelength of demultiplexed is compensated, for each of the wavelengths lambda ₁ to [lambda] _n The dispersion becomes zero as a whole. Chromatic dispersion compensator 103-1 to 1
The output of 03-n is multiplexed by the optical branching coupler 104 and output as the signal light 100-2.

In order to extend the transmission distance, a method of inserting an optical fiber amplifier in the middle of a transmission line has been considered. One example is disclosed in Japanese Patent Application Laid-Open No. 8-316912. This will be described below. FIG. 11 shows a second example of the conventional chromatic dispersion compensating device. Input optical transmission line 2
A signal light input 100-1 wavelength-division multiplexed with wavelengths λ _{1 to} λ _n is propagated to 01, and an optical amplifier 202 is connected to the output terminal. In the optical amplifier 202,
A first port of the optical circulator 203 is connected;
A chromatic dispersion compensating fiber 205 is connected to the second port, and an output optical transmission line 204 is connected to the third port. Further, the chromatic dispersion compensating fiber 205 includes a chirped grating fiber.
r) 206 is connected, and the non-reflective terminal 207 is connected to its output terminal.
Is provided.

In FIG. 11, a wavelength-multiplexed signal light 100-1 is input to an input optical transmission line 201 and propagated to attenuate the power of each signal light of wavelengths λ _{1 to} λ _n and reduce the wavelength of each signal light. Can be compensated for. That is, the power attenuation of each signal light of the wavelengths λ _{1 to} λ _n is compensated by the amplification of the signal light by the optical amplifier 202. The chromatic dispersion value of the signal light of each of the wavelengths λ _{1 to} λ _n is obtained by inputting the output signal light of the optical amplifier 202 to the first port of the optical circulator 203, extracting the signal light from the second port, and extracting the second signal light. After the signal light 208 is propagated through the chromatic dispersion compensating fiber 205 and the chirped grating fiber 206 connected to the port, and the signal light is reflected for each wavelength in the chirped grating fiber 206, the chromatic dispersion compensating device 205 As signal light 209 in the opposite direction. The signal light 209 that has propagated in the opposite direction propagates from the second port to the third port of the optical circulator 203, and further propagates as signal light 210 in the output optical transmission line 4, thereby achieving high chromatic dispersion compensation. Output is achieved, and a signal light output 100-2 is obtained.

FIG. 12 shows a third example of a conventional chromatic dispersion compensating device. The configuration of FIG. 12 is different from the configuration of FIG.
The optical amplifier 202 is moved between the optical circulator 203 and the output optical transmission line 204. Since there is no change in other configurations, duplicate description will be omitted. The signal light input 100-1 multiplexed by the wavelengths λ _{1 to} λ _n from the input optical transmission line 201 passes through the optical circulator 203 and propagates to the chromatic dispersion compensating fiber 205. After the chromatic dispersion compensation is performed by the chromatic dispersion compensating fiber 205, the reflected signal light is reflected by the chirped grating fiber 206, and the reflected signal light reaches the optical amplifier 202 through a path from the second port to the third port of the optical circulator 203. Then, after being optically amplified here, it passes through the output optical transmission line 204 and is extracted as a signal optical output 100-2.

[0009]

However, the conventional chromatic dispersion compensating device has the following problems. (1) In the case of the configuration of FIG. 10, the chromatic dispersion compensator 103-1
Pass-through optical components, for example, a dispersion compensating fiber are used for -103-n. However, since the length of the optical compensator is several km or more, optical loss is large, the size is large, cost reduction is difficult, and the like. There's a problem. (2) Further, an optical splitter / coupler 101 for distributing n the signal light output wavelength-multiplexed to the input unit is required, and further, a light for multiplexing the n-demultiplexed signal light to the output unit. Since the branch coupler 104 is required, there is a problem that the wavelength-multiplexed signal light is attenuated due to the branch loss in the optical branch coupler, and the transmission distance is limited. (3) Further, since a large number of optical components are used, a connection loss between the optical components becomes a problem, and reflected light from each connecting portion deteriorates crosstalk between the channels. There's a problem. (4) In the case of the configurations shown in FIGS. 11 and 12, an optical amplifier having independent functions and a chromatic dispersion compensator are provided, and they are cascaded. Become. Further, there is a problem that the transmission loss increases as the number of optical components increases, and it is difficult to reduce the size. (5) The increase in the number of optical components as in (4) increases the connection loss between each optical component and further increases the polarization-dependent loss. (6) Further, a major problem of the configurations of FIGS. 11 and 12 is that
As the wavelength band of the wavelength-multiplexed signal light is widened, it is difficult to make the chromatic dispersion characteristics of the chirped grating fiber 206 highly accurate. Low reliability.

Accordingly, it is an object of the present invention to provide an ultra-wide band chromatic dispersion compensating device capable of compensating chromatic dispersion of a transmission line and its dispersion slope over a wide band. Still another object of the present invention is to provide an ultra-wide band chromatic dispersion compensating device which can constitute an amplification of chromatic dispersion compensated signal light by an integrated circuit.

[0011]

SUMMARY OF THE INVENTION In order to achieve the above object, the present invention provides an input optical transmission line through which signal light in which a plurality of different wavelengths are multiplexed is propagated, and a signal from the input optical transmission line. An optical demultiplexer that demultiplexes light into signal light in a plurality of wavelength regions such as a long wave band and a short wave band, and the signal light in the plurality of wavelength regions demultiplexed by the optical demultiplexer has a plurality of different wavelengths. A plurality of optical multiplexers / demultiplexers for demultiplexing the signal light, compensating for the wavelength dispersion of the demultiplexed signal light, and multiplexing the signal light for output; and the signal light demultiplexed by the plurality of optical multiplexers / demultiplexers. And a plurality of chirped grating fibers for individually propagating and reflecting light, performing chromatic dispersion compensation, and sending the resultant to the optical multiplexer / demultiplexer.

[0012]

Embodiments of the present invention will be described below with reference to the drawings. In each embodiment of the present invention, a short wavelength band of 1.53 μm to 1.56 μm (hereinafter referred to as “L band”) and a wavelength band of 1.57 μm to 1.56 μm are used.
1.61 μm long wavelength band (hereinafter referred to as “H band”)
To compensate for the chromatic dispersion of an optical transmission line (for example, a single-mode fiber or a dispersion-shifted fiber) in which at least eight or more waves are wavelength-division-multiplexed, and disperse their dispersion slopes (to each of the wavelengths λ _{1 to} λ _n) . On the other hand, it is aimed at controlling the dispersion value of the signal light of each wavelength in the above-mentioned wavelength band to almost zero.

FIG. 1 shows a first embodiment of an ultra-wide band chromatic dispersion compensating device according to the present invention. The input optical transmission line 1 through which the signal light 13 is propagated has a dispersion compensating fiber (D
CF) 2 is connected, and WDM is
Filter (wavelength division multiplex filter: Wavelength Divisi
on Multiplexing filter) 3 is connected. WDM
A port of the optical circulator 5 is connected to an end of the filter 3 for outputting the signal light 4a (short wavelength band), and an end of the filter 3 for outputting the signal light 4b (long wavelength band) of the WDM filter 3 (optical demultiplexer). Is connected to the port of the optical circulator 6. A WDM filter 7 (optical multiplexer / demultiplexer) is connected to a port of the optical circulator 5, and chirped grating fibers 8a, 8a,
8b, 8c and 8d are connected. Similarly, a WDM filter 9 (optical multiplexer / demultiplexer) is connected to a port of the optical circulator 6, and chirped grating fibers 10a, 10b, 10
c and 10d are connected. Optical circulators 5, 6
Each of the ports is connected to a WDM filter 11 (optical multiplexer), and an output end thereof is connected to an output optical transmission line 12.

The input optical transmission line 1 has, for example, a wavelength of 1.3.
A single-mode fiber (or dispersion-shifted fiber) having a zero-dispersion wavelength in μm is used, and its length is several tens of km. The wavelength-multiplexed signal light 13 is composed of the L band (wavelength region) and the H band as described above. For example, the L band contains eight signal lights (wavelengths λ _{1 to} λ ₈ ) at 0.8 nm intervals, and the H band contains eight signal lights (wavelengths λ _{9 to} λ ₁₆ ) at 0.8 nm intervals. I have. These signal lights are, for example, 10
Propagation is at a transmission rate of Gb / s. Each of the WDM filters 7 and 9 is an optical multiplexing / demultiplexing circuit having one input and four outputs.

Next, the ultra-wide band chromatic dispersion compensation of the configuration of FIG.
The operation of the device will be described. The input optical transmission line 1
The carried signal light 13 is input to the dispersion compensating fiber 2.
Then, dispersion compensation is performed. The dispersion compensating fiber 2 is
Wavelength λ₁~ Λ ₁₆(However, λ₁<
λ₁₆) That the signal light 13 wavelength-division multiplexed propagates
(Λ)₁D for₁, Λ₁₆In the case of
D₁₆, D₁<D₁₆) And a variance with a value of almost the opposite sign
And, for example, -D₁Fiber with a dispersion value of
The length is defined. Output from the dispersion compensating fiber 2
The signal light 14 is input to the WDM filter 3. this
Between the WDM filter 3 and the WDM filter 11,
The dispersion deviation value at each wavelength is compensated. WDM
The filter 3 is used for the wavelength-multiplexed signal light λ.₁~ Λ₁₆Two
Wavelength band, ie, λ₁~ Λ₈And λ₉~ Λ₁₆Split into two
You. Wavelength λ₁~ Λ₈Is demultiplexed as the signal light 4a, and the wavelength is
λ₉~ Λ ₁₆Are demultiplexed as signal light 4b, and
Calculators 5 and 6 are input to each port.

The optical circulator 5 outputs the signal light 4a input to the port to the port as the signal light 15a and propagates the signal light 15a to the WDM filter 7. And WD
The signal light 16a from the M filter 7 is output from port to port. Similarly, the optical circulator 6 outputs the signal light 4b input to the port to the port as the signal light 15b and propagates the signal light 4b to the WDM filter 9.
Then, the signal light 16b from the WDM filter 9 is output from port to port.

The WDM filter 7 is wavelength-multiplexed.
The signal light 15a is divided into four wavelength bands, that is, λ₁And λ_Two,
λ_ThreeAnd λ_Four, Λ_FiveAnd λ₆, Λ₇And λ₈Output to
You. Specifically, λ₁And λ_TwoIs chirped grating
Λ_ThreeAnd λ _FourBut chirp greaty
Λ_FiveAnd λ₆Is Chirp Grete
Λ₇And λ₈Is chirped gray
It is output to the toting fiber 8d. Similarly, WDM
The filter 9 converts the wavelength-multiplexed signal light 15b into four signals.
Wavelength band, ie, λ₉And λ_Ten, Λ₁₁And λ₁₂, Λ₁₃And λ
₁₄, Λ_FifteenAnd λ₁₆And output. λ₉And λ_TenIs cha
Λ in the grating 10a₁₁And λ₁₂But
The chirped grating fiber 10b has λ₁₃And λ
₁₄Is λ in the chirped grating fiber 10c._Fifteen
And λ₁₆Appears on chirped grating fiber 10d
Is forced.

The chirped grating fibers 8a to 8d and 10a to 10d are chromatic dispersion compensating circuits for performing dispersion compensation and dispersion slope compensation that could not be compensated by the dispersion compensating fiber 2. For example, the chirped grating fiber 8a compensates for the chromatic dispersion of the signal light of wavelengths λ ₁ and λ ₂ propagating therein, and the signal light of wavelengths λ ₁ and λ ₂ is 17a and the chirped grating fiber 8a The signal light having the wavelength λ ₁ propagates through the inside of the chirped grating fiber 8a, and then is reflected. The signal light having the wavelength λ ₂ is reflected slightly before the reflection position of the wavelength λ ₁ in the chirped grating fiber 8 a, returns as signal light 17 b, and is multiplexed by the WDM filter 7.

In the chirped grating fiber 8b, signal lights of wavelengths λ ₃ and λ ₄ respectively propagate, and the wavelength λ
Numeral ₄ is the near side, and the wavelength λ ₃ propagates further to the far side than the wavelength λ _{4 and} is reflected, respectively.
Return to here, where it is multiplexed. The signal lights of wavelengths λ ₅ and λ ₆ respectively propagate in the chirped grating fiber 8 c, and the wavelength λ ₆ is reflected at the near side and the wavelength λ ₅ is further reflected at the far side, and returns to the WDM filter 7 again. Multiplexed. Furthermore, chirped grating fiber 8d
Inside, signal lights of wavelengths λ ₇ and λ ₈ propagate, respectively, and the wavelength λ ₈ is reflected at the near side and the wavelength λ ₇ is reflected at the far side, and returns to the WDM filter 7 again. Are multiplexed. In the WDM filter 7, the chromatic dispersion is compensated by giving the signal light of each wavelength a propagation delay. Chirped grating fiber 1
Also at 0a, 10b, 10c, and 10d, the signal light of the input wavelength propagates in the same manner as the WDM filter 7 side, reflects at a predetermined position, returns to the WDM filter 9 again, and is multiplexed. Is given a propagation delay, thereby compensating the chromatic dispersion.

The signal light that has been dispersion-compensated by the WDM filters 7 and 9 passes through the WDM filters 7 and 9 in the opposite direction to the signal light 16.
The light propagates as a and b and is output from each port of the optical circulators 5 and 6 to the WDM filter 11 through the port. The WDM filter 11 combines the L-band dispersion-compensated signal light 16a and the H-band dispersion-compensated signal light 16b, and outputs the resultant to the output optical transmission line 12 as a dispersion-compensated signal light 19.

Since the wavelength-multiplexed signal light 13 is transmitted over a length of several tens km in the input optical transmission line 1, the longer the transmission distance, the larger the chromatic dispersion value.
It will have a dispersion slope. The chromatic dispersion value needs to be as close to 0 as possible and the dispersion slope must be small, that is, the transmission distortion of the signal light propagating in the input transmission line 1 needs to be as small as possible.

According to the above-described embodiment, the dispersion values (D _{1 to} D ₁₆ ) of the respective wavelengths caused by the propagation of the wavelength-multiplexed signal light 13 in the input optical transmission line 1 are firstly calculated. The compensation fiber 2 compensates for −D ₁ , and D
_{2 -D 1, D 3 -D 1} , D 4 -D 1, ··· D 16 -D 1
Since the wavelength dispersion values up to are compensated between the WDM filter 3 and the WDM filter 11, the wavelength dispersion value and the dispersion slope can be compensated. As a result, the dispersion of the signal light from the wavelengths λ ₁ to λ ₁₆ is substantially zero on the output optical transmission line 12 side, and the signal light 18 compensated so that the chromatic dispersion values are substantially equal between each other. Can be obtained.

FIG. 2 shows a second embodiment of the ultra-wide band chromatic dispersion compensating device according to the present invention. There are the following three points different from the configuration of FIG. First, the first difference is that each of the WDM filters 7 and 9 uses an optical multiplexer / demultiplexer having one input and eight outputs. That is, the WDM filter 7
Demultiplexes the signal light of wavelengths λ ₁ to λ ₈ to eight output terminals, respectively, and outputs chirped grating fibers 8a, 8b, 8c, 8d, 8e, 8 connected to the respective output terminals.
f, 8g, and 8h. Similarly, the WDM filter 9 splits the signal light of wavelengths λ ₉ to λ ₁₆ into eight output terminals, respectively, and outputs chirped grating fibers 10a, 10b, 10c, and 10c connected to the respective output terminals.
It propagates in 10d, 10e, 10f, 10g, and 10h.

The second difference is chirped grating fiber 8a is for compensating for the dispersion of the wavelength lambda ₁ of the signal light, likewise, chirped grating fiber 10a, the signal light of the wavelength lambda ₉ Is used to compensate for the dispersion of The other chirped grating fibers 8b to 8h and 10b to 10h are also used for compensating the dispersion of the signal light of one wavelength.

The third difference is that the WDM filter 1 shown in FIG.
1, an optical isolator 20 and an optical circulator 21
Is used to form an optical multiplexer. That is,
The dispersion-compensated L-band signal light 16 a passes through an optical isolator 20 and becomes a signal light 22 as an optical circulator 2.
The light enters the first port and is guided to the output optical transmission line 12 through the port. On the other hand, the dispersion-compensated H-band signal light 16 b enters the port of the optical circulator 21, is guided to the port, and propagates as signal light 23 to the optical isolator 20. Then, the light is reflected by the optical isolator 20 and becomes the signal light 24 as the optical circulator 2.
The light enters one port, and is output to the output optical transmission line 12 through the port.

The configuration of FIG. 2 is characterized in that the optical isolator 20 and the optical circulator 21 are used instead of the WDM filter 11 on the output side, so that the optical isolation between the L-band signal light 16a and the H-band signal light 16b is achieved. It is possible to increase the characteristics and to maintain good optical crosstalk characteristics between each other. In addition, since the optical circulator 21 is used, it is possible to prevent reflected return light from the output optical transmission line 12 side.

FIG. 3 shows a third embodiment of the ultra-wide band chromatic dispersion compensating device according to the present invention. In this embodiment,
The aim is to realize an optical device that has an amplifying function by integrating an ultra-wide band chromatic dispersion compensating device and an amplifying device, and that can reduce the cost. In FIG. 3, the same reference numerals are used for those having the same or the same functions as those in FIGS. 1 and 2, and thus the duplicated description will be omitted here.

In FIG. 3, Er (rare earth element) -doped optical fibers 31 and 32 are used for a transmission line between the optical circulators 5 and 6 and the WDM filter 11 in FIG. Er
The WDM coupler 33 is located near the input side of the doped optical fiber 31.
Are coupled, and WDM is provided on both sides of the Er-doped optical fiber 32.
Couplers 34 and 35 are coupled. WDM coupler 33
Is connected to an excitation light source 36, and WDM couplers 34, 35
Are connected to excitation light sources 37 and 38. Excitation light source 3
6, a semiconductor laser having a wavelength of 1.48 μm or 0.98 μm is used.
A semiconductor laser of a 48 μm band or a 0.98 μm band is used. Further, an optical isolator 20 is provided in the output optical transmission line 12 in order to prevent light from entering from the output side.

The L-band signal light 1 already dispersion-compensated
6a is an optical fiber 3 from the optical circulator 5
1 is input. The excitation light from the excitation light source 36 is input to the Er-doped optical fiber 31 through the WDM coupler 33. When this pumping light is propagated through the Er-doped optical fiber 31 to form a population inversion state, the signal light 16 a is amplified, for example, from several thousand times to about 10,000 times, and the amplified signal light is transmitted to the WDM filter 11. It is input to one input terminal. Further, the excitation light source 3 is
The pumping lights from 7, 38 are input through WDM couplers 34, 35. As a result, the signal light 16b is amplified, for example, from several thousand times to about 10,000 times, and the amplified signal light is input to the other input terminal of the WDM filter 11. The WDM filter 11 multiplexes the amplified signal lights of the two bands and sends the multiplexed signal lights to the optical isolator 20. The signal light of the two bands passing through the optical isolator 20 is
The output light transmission path 12 propagates as signal light 18. The optical isolator 20 has a function of suppressing reflected return light of signal light from the output optical transmission line 12.

The pumping light to the Er-doped optical fiber 31 is E
The pumping may be performed not only from the input side of the r-doped optical fiber 31 but also from the output side. In addition to the excitation light source 36,
A configuration may be adopted in which excitation is performed from both sides by adding a table. FIG.
Shows a fourth embodiment of the ultra-wide band chromatic dispersion compensating device according to the present invention. The basic configuration of the present embodiment is the same as that of FIG.
a is provided with an optical filter 41 and wavelengths λ ₁ , λ ₂ , λ ₃ , λ
_The feature is that the amplification degree of the L-band signal light composed of ₄ , λ ₅ , λ ₆ , λ ₇ and λ ₈ can be made uniform. That is, in order to suppress the gain peak in the 1.53 μm band of the wavelength λ ₁ , the optical filter 41 is provided in the middle of the chirped grating fiber 8 a, and the 1.53 μm band is provided.
m-band signal light is attenuated. In the present embodiment, of the signal light of wavelengths λ ₁ and λ ₂ propagating through the chirped grating fiber 8a, mainly the wavelength λ ₁ (=
(1.53 μm) is partially attenuated. Thereby, the amplification degree of the signal light of the wavelengths λ _{1 to} λ ₁₆ can be made substantially uniform.

The adjustment of the amplification degree between the L band and the H band is as follows.
This can be achieved by appropriately setting the lengths of the Er-doped optical fibers 31 and 32, the amount of Er added, the optical power of the excitation light sources 36, 37 and 38, and the like. For the Er-doped optical fibers 31 and 32, in addition to the addition of Er, a quartz-based fiber or a fluoride-based fiber to which Al is co-doped can be used.
Alternatively, a fiber in which a silica-based fiber and a fluoride-based fiber to which Al is co-doped may be used.

According to the embodiment of FIG. 4, similarly to the embodiment of FIG. 3, it becomes possible to amplify the signal light in addition to the chromatic dispersion compensation. FIG. 5 shows a fifth embodiment of the ultra-wide band chromatic dispersion compensating device according to the present invention. In this embodiment, the Er-doped optical fibers 31 and 3 used in FIG.
2, WDM couplers 33, 34, 35, excitation light sources 36, 3
7 and 38 are added to the configuration of FIG. That is, Er-doped optical fibers 131 and 32 are connected between the optical circulator 5 and the optical isolator 20, and between the optical circulator 6 and the optical circulator 21, respectively. The pumping lights from 36, 37 and 38 are respectively propagated,
Each of the signal lights 16a and 16b can be independently amplified.

According to the embodiment of FIG. 5, in addition to chromatic dispersion compensation, amplification of signal light can be performed. FIG. 6 shows a sixth embodiment of the ultra-wide band chromatic dispersion compensating device according to the present invention. In FIG. 6, the same reference numerals are used for the same components as those used in FIG. The port of the optical circulator 61 is connected to the input optical transmission line 1, the port is connected to the dispersion compensating fiber 2, and the port is connected to the output optical transmission line 12. A WDM filter 3 is connected to the dispersion compensating fiber 2, and the WDM filter 3
The filter 3 is connected to WDM filters 7 and 9. Chirped grating fibers 8a to 8d are connected to the WDM filter 7, and chirped grating fibers 10a to 10d are connected to the WDM filter 9.

In FIG. 6, a signal light 13 (having wavelengths λ _{1 to} λ ₁₆ ) propagating through the input optical transmission line 1 is input to a port of the optical circulator 61, and the signal is transmitted from the port to the dispersion compensating fiber 2. The light is output as light 62 and the signal light 63 from the dispersion compensating fiber 2 is output to the port as the signal light 12. About 1/2 of the dispersion of the wavelength dispersion value caused by propagating through the input optical transmission line ₁ (D 1 ~D ₁₆₎ (approximately, -D _1/2) is compensated by the dispersion compensating fiber 2. The signal light 64 having passed through the dispersion compensating fiber 2 enters a WDM filter 3 which is an optical demultiplexer, and the WDM filter 3 converts the signal light 64 into two wavelength bands, namely, an L-band signal light 15a and an H-band signal light 15b. Separated. The L-band signal light 15 a (signal light of wavelengths λ _{1 to} λ ₈ ) enters the WDM filter 7. The H-band signal light 15b (signal light of wavelengths λ _{9 to} λ ₁₆ ) is a WDM signal.
The light enters the filter 9.

Wavelengths λ _{1 to} λ incident on WDM filter 7
Each of the eight wavelengths of _eight is demultiplexed into four output terminals, propagating chirped grating fiber 8a~8d connected to respective output terminals. For example, the chirped grating fiber 8a has wavelengths λ ₁ and λ ₂
The signal light of wavelength λ ₂ is reflected back before the chirped grating fiber 8a and returned, and the wavelength λ 2
The signal light of ₁ is reflected at a position deeper than the reflection position of λ ₂ and returns, reaches the output end of the WDM filter 7 again, is multiplexed, and propagates as the signal light 16a. Similarly, signal lights of wavelengths λ ₄ and λ ₅ , and λ ₇ and λ ₈ also propagate through chirped grating fibers 8 b, 8 c and 8 d, are reflected at predetermined positions and returned, and are multiplexed by WDM filter 7. , And propagates as a signal light 65a, and further, is multiplexed by the WDM filter 3 and propagates as a signal light 65. In addition, the wavelength λ ₉
The H-band signal light 15b of λ ₁₆ is
Λ ₉ and λ ₁₀ , λ ₁₃ and λ ₁₄ , λ ₁₅ and λ ₁₆ , and propagates in the respective chirped grating fibers 10 a, 10 b, 10 c, and 10 d at predetermined positions. The reflected light propagates through the chirped grating fiber in the opposite direction, returns to the WDM filter 9, is multiplexed, propagates like the signal light 16b, is multiplexed with the signal light 16a by the WDM filter 3, and After passing through the dispersion compensating fiber 2 as described above, the signal light 18 is output from the port of the optical circulator 3 to the output optical transmission line 12 through the port.

As described above, in the ultra-wideband chromatic dispersion compensating device of FIG. 6, the chromatic dispersion caused by the propagation of the wavelength division multiplexed signal light 13 in the input optical transmission line 1
The optical signal light 62 passes through the dispersion compensating fiber 2 to compensate for the approximate dispersion value, and the remaining dispersion value is compensated when the signal light 65 from the WDM filter 3 is transmitted to the dispersion compensating fiber 2 from the opposite direction. doing. If the dispersion compensation amount in the dispersion compensating fiber 2 is reduced and the dispersion compensation amount in the chirped grating fibers 8a to 10d is increased, and the attenuation of the signal light in the dispersion compensating fiber 2 is reduced, It can support long distance transmission. Therefore, the smaller the amount of dispersion compensation in the dispersion compensating fiber 2 in FIGS.
It is preferable that each chirped grating fiber has a large amount of dispersion compensation.
The chromatic dispersion compensation may be performed only with each chirped grating fiber without providing the dispersion compensating fiber 2. In this way, chromatic dispersion compensation with lower loss can be performed, and longer distance transmission can be realized.

FIG. 7 shows a seventh embodiment of the ultra-wide band chromatic dispersion compensating device according to the present invention. In this embodiment,
The feature is that an amplification function is added to the configuration of FIG.
That is, an Er-doped optical fiber 71 and an optical isolator 72 are inserted in series between the port of the optical circulator 61 and the output optical transmission line 12, and WDM couplers 73 and 74 are coupled to both sides of the Er-doped optical fiber 71. Excitation light sources 75 and 76 are connected to each other.
The other configuration is as shown in FIG.

The signal light 13 is applied to the port of the optical circulator 61 → the port of the optical circulator 61 → the dispersion compensating fiber 2 → the WDM filter 3 → the WDM filters 7, 9 → W
The operation from the DM filter 3 → the dispersion compensating fiber 2 → the port of the optical circulator 61 is the same as that in FIG. 6, and the description is omitted here. The signal light 63 from the port of the optical circulator 61 whose wavelength dispersion has been compensated for is Er.
The light is propagated through the addition optical fiber 71, and the
The pump light from the optical fibers 5 and 76 is propagated through the WDM couplers 73 and 74 into the Er-doped optical fiber 71. As a result, the signal light 63 passing through the Er-doped optical fiber 71 is amplified several thousand times to 10,000 times, and
The signal light 18 is output to the output optical transmission line 12 as signal light 18.

As described above, according to the ultra-wide band chromatic dispersion compensating device of FIG. 7, a device having a chromatic dispersion compensating function and an amplifying function can be realized by a simple configuration, a small number of optical components, and a transmission system with a small optical loss. Can be realized by: The chromatic dispersion compensation from the signal light 13 to the signal light 18 is also performed for each of the chirped grating fibers 8a to 8c.
Needless to say, the configuration may be such that d is shared.

FIG. 8 shows a modification of FIG. This example is obtained by adding the function of a gain equalizer to the configuration of FIG.
That is, in order to suppress the amplification gain of the signal light in the 1.53 μm band (λ ₁ ), the optical filter 41 (see FIG. 4) for attenuating the signal light in the 1.53 μm band in the middle of the chirped grating fiber 8a. (The same filter as used) is inserted. Thus, the wavelength λ ₁
To λ ₁₆ can be kept uniform.

The present invention is not limited to the configurations of the above embodiments. First, a waveguide-type chirped grating filter may be used instead of the chirped grating fibers 8a to 10d. Also, W
As the DM filters 3, 7, 9, and 11, any of a waveguide type, an interference film filter type, and a fiber grating type may be used. The wavelength-multiplexed signal lights are 8, 20, 32, 6
The number of channels such as 4, 100,... Can be used. Therefore, the number of multiplexes in the WDM filters 7 and 9 is 4, 8, 20, 3 according to the number of channels.
2, 50, ..., etc. However, WDM
The number of output terminals of the filters 7 and 9 does not necessarily have to be half of the above-mentioned number of channels, and can be dealt with by increasing the number of channels propagated into each chirped grating fiber. For example, when the number of multiplexed wavelengths is 32, the number of channels propagated in each of the chirped grating fibers 8a to 10d in the configuration of FIG. In the case where a dispersion-shifted fiber having a zero-dispersion wavelength in the 1.53 μm wavelength band is used for the input optical transmission line 1 and a distance of several tens of km or more is propagated, the dispersion compensating fiber 2 shown in FIGS. Need not be used.

[0042]

As described above, according to the ultra-wide band chromatic dispersion compensating / amplifying device of the present invention, the signal light from the input optical transmission line is demultiplexed into a plurality of wavelength regions by the optical demultiplexer. The optical multiplexer / demultiplexer demultiplexes the plurality of wavelength regions into a predetermined number of wavelength bands, and multiplexes the signal light after wavelength dispersion-compensating the signal light of the demultiplexed wavelength band to output side. , And individually propagate the signal light of each wavelength band demultiplexed by the optical multiplexer / demultiplexer using a plurality of chirped grating fibers, and perform wavelength dispersion in a process where the signal light is reflected from a predetermined position. Each of the compensated signal lights is transmitted to the optical multiplexer / demultiplexer to be multiplexed, so that the following effects are specifically obtained. (1) A single mode fiber or a dispersion-shifted fiber of several tens of km using a wavelength of 1.53 μm to 1.61 μm.
It is possible to compensate for chromatic dispersion generated when performing wavelength multiplex transmission over the above. (2) The number of optical parts is small, the loss is low, and unnecessary characteristics are less likely to cause a fire. Long-distance, large-capacity, high-speed transmission is possible, and these can be achieved at low cost. (3) Since precise dispersion compensation can be performed for each wavelength, high-quality transmission is possible. (4) Since a simple configuration in which chromatic dispersion compensation of many wavelength-multiplexed signal lights over an ultra-wide band and amplification of those signal lights can be integrated into a simple configuration, a higher-performance and lower-cost communication system can be constructed. be able to. (5) Since the chromatic dispersion compensation of each chirped grating fiber is for signal light of one wavelength or several wavelengths, it is possible to use a chirped grating fiber that can be reduced in size, cost, and mass-produced. become.

[Brief description of the drawings]

FIG. 1 is a connection diagram showing a first embodiment of an ultra-wide band chromatic dispersion compensating device according to the present invention.

FIG. 2 is a connection diagram showing a second embodiment of the ultra-wide band chromatic dispersion compensating device according to the present invention.

FIG. 3 is a connection diagram showing a third embodiment of the ultra-wide band chromatic dispersion compensating device according to the present invention.

FIG. 4 is a connection diagram showing a fourth embodiment of the ultra-wide band chromatic dispersion compensating device according to the present invention.

FIG. 5 is a connection diagram showing a fifth embodiment of the ultra-wide band chromatic dispersion compensating device according to the present invention.

FIG. 6 is a connection diagram showing a sixth embodiment of the ultra-wide band chromatic dispersion compensating device according to the present invention.

FIG. 7 is a connection diagram showing a seventh embodiment of the ultra-wide band chromatic dispersion compensating device according to the present invention.

FIG. 8 is a connection diagram showing a modification of FIG. 7;

FIG. 9 is an explanatory diagram showing a relationship between a dispersion state and a propagation distance.

FIG. 10 is a connection diagram showing a first example of a conventional chromatic dispersion compensating device.

FIG. 11 is a connection diagram showing a second example of a conventional chromatic dispersion compensating device.

FIG. 12 is a connection diagram showing a third example of a conventional chromatic dispersion compensating device.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1 Input optical transmission line 2 Dispersion compensation fiber 3, 7, 9, 11 WDM filter 5, 6, 21, 61 Optical circulator 8a, 8b, 8c, 8d Chirped grating fiber 8e, 8f, 8g, 8h Chirped grating fiber 10a , 10b, 10c, 10d Chirped grating fiber 10e, 10f, 10g, 10h Chirped grating fiber 12 Output optical transmission line 20, 72 Optical isolator 31, 32, 71 Er-doped optical fiber 33, 34, 35, 73, 74 WDM Couplers 36, 37, 38, 75, 76 Excitation light source 41 Optical filter

Claims (14)

[Claims] 1. An input optical transmission line through which signal light in which a plurality of different wavelengths are multiplexed is propagated, and a signal light from the input optical transmission line is converted into a signal light in a plurality of wavelength regions such as a long wave band and a short wave band. An optical demultiplexer that demultiplexes the signal light in the plurality of wavelength regions into a plurality of different wavelengths of signal light and wavelength-disperses the signal light that is demultiplexed by the optical demultiplexer. A plurality of optical multiplexers / demultiplexers for multiplexing after compensating and transmitting to the output side; and the signal lights demultiplexed by the plurality of optical multiplexers / demultiplexers are individually propagated and reflected to perform chromatic dispersion compensation to perform the optical multiplexing. An ultra-wide band chromatic dispersion compensating device, comprising: a plurality of chirped grating fibers to be sent to a duplexer. 2. The ultra-wideband chromatic dispersion compensating device according to claim 1, wherein said input optical transmission line is a single mode fiber or a dispersion shift fiber having a zero dispersion wavelength at a wavelength of 1.3 μm. 3. The ultra-wideband chromatic dispersion compensating device according to claim 1, wherein said optical demultiplexer is provided with a dispersion compensating fiber at a preceding stage thereof. 4. A plurality of optical circulators are used to propagate signal light from the optical multiplexer / demultiplexer to the plurality of optical multiplexer / demultiplexers and to propagate signal light from the plurality of optical multiplexer / demultiplexers to the output side. 2. The ultra-wide band chromatic dispersion compensating device according to claim 1, wherein 5. The ultra-wideband chromatic dispersion compensating device according to claim 1, further comprising an optical multiplexer for multiplexing the signal lights output from the plurality of optical circulators. 6. An optical isolator for passing signal light in one wavelength region of the plurality of wavelength regions output from one of the plurality of optical multiplexers / demultiplexers, and passing the optical isolator. The input signal light from the first port and output to the second port, and the other wavelength region of the plurality of wavelength regions output from another of the plurality of optical multiplexer / demultiplexers. The signal light is input from the third port and output to the first port, reflected by the optical isolator, and the reflected signal light is input from the first port and output to the second port 6. The ultra-wide band chromatic dispersion compensating device according to claim 5, comprising a circulator. 7. The ultra-wideband chromatic dispersion compensating device according to claim 5, wherein an optical isolator is connected to an output side of the optical multiplexer. 8. A plurality of rare earth element-doped optical fibers connected to the output side of the plurality of optical multiplexers / demultiplexers and amplifying respective output signal lights of the optical multiplexer / demultiplexers, and each of the rare earth element added optical fibers 2. The ultra-wideband chromatic dispersion compensating device according to claim 1, further comprising: an excitation unit that supplies excitation light to the device. 9. The ultra-wideband chromatic dispersion compensating device according to claim 8, wherein said pumping means propagates the pumping light in one or both directions in the rare earth element-doped optical fiber. 10. When the multiplexed signal light includes signal light having a wavelength of 1.53 μm to 1.61 μm, the pumping means serves as a pumping light source in a 0.98 μm band and 1.48 μm.
The ultra-wide band chromatic dispersion compensating device according to claim 8, further comprising a semiconductor laser that emits pump light in a band or both wavelength bands. 11. The chirped grating fiber is characterized in that an optical filter for attenuating the 1.53 μm wavelength signal light is inserted in the middle of the chirped grating fiber as long as it propagates the 1.53 μm wavelength signal light. The ultra-wide band chromatic dispersion compensating device according to claim 1, wherein 12. The input optical transmission line is connected to a first terminal of a three-terminal optical circulator, and the optical demultiplexer is connected to the three-terminal optical circulator.
2. The ultra-wideband chromatic dispersion compensating device according to claim 1, wherein the terminal is connected to a second terminal of the terminal optical circulator, and the output side is connected to a third terminal of the three-terminal optical circulator. 13. A rare earth element-doped optical fiber connected to an output terminal of the three-terminal optical circulator for amplifying an output signal light of the optical circulator, and an excitation unit for supplying excitation light to the rare earth element-doped optical fiber. 13. The ultra-wide band chromatic dispersion compensating device according to claim 12, wherein 14. The ultra-wide band chromatic dispersion compensating device according to claim 1, wherein said chirped grating fiber is constituted by a chirped grating waveguide.