JPH10242943A - Wavelength division multiplexing optical processor - Google Patents

Abstract

PROBLEM TO BE SOLVED: To improve the transmission characteristic of a wavelength division MULTIPLEXING OPTICAL transmission system. SOLUTION: A demultiplexer 20 demultiplexes a wavelength division multiplexing optical signal having wavelengths λ1 to λn into signals of respective wavelength λ1 to λn and outputs these signals to channels #1 to #n. Wavelength selection filters 22-1 to 22-n consist of fiber grating parts 24 to 30. The wavelength dispersion of light transmitted through the filters 22-1 to 22-n is respectively compensated by wavelength dispersion compensating fibers 32-1 to 32-n and the compensated signals are multiplexed again by a multiplexer (wavelength multiplexer) 34.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

[0001] 1. Field of the Invention [0002] The present invention relates to a wavelength division multiplexing optical processing apparatus, and more particularly, to a wavelength division multiplexing optical processing apparatus for individually processing individual wavelengths or wavelength bands of a wavelength division multiplexing optical signal.

[0002]

2. Description of the Related Art In an optical fiber communication system, a wavelength division multiplex system is considered to be promising. Wavelength division multiplexing (WDM)
In this method, a wavelength division multiplexed optical signal is transmitted on an optical fiber, but a repeater or the like separates the wavelength division multiplexed optical signal into individual wavelengths or a group of wavelength bands, and performs processing such as gain equalization or chromatic dispersion compensation. It is necessary to perform wavelength division multiplexing again and transmit the signal onto an optical fiber. This is because the transmission characteristics such as chromatic dispersion and the amplification characteristics of the relay amplifier differ depending on the wavelength, and it is necessary to make these uniform.

FIG. 14 is a schematic block diagram of a conventional example in which a wavelength division multiplexed optical signal is demultiplexed into individual wavelengths to compensate for chromatic dispersion. The demultiplexer 10 demultiplexes the signal light obtained by wavelength division multiplexing the signal lights of the wavelengths λ _{1 to} λ _n into n pieces. Duplexer 10
Each output of the optical bandpass filter designed primarily to pass through one wavelength of wavelengths λ ₁ ~λ _n 12-1~12-
n. For example, optical bandpass filters 12-1 mainly passes through the wavelength lambda _1, an optical bandpass filter 12
2 mainly passes through the wavelength λ _2, and similarly, the bandpass optical filter 12-n is designed to pass mainly through the wavelength λ _n .

The light transmitted through the band-pass optical filters 12-1 to 12-n is converted into chromatic dispersion compensating fibers 14-1 to 14-n designed to compensate for the chromatic dispersion of the corresponding wavelength.
Where the chromatic dispersion is compensated. If the chromatic dispersion in the wavelength band of λ _{1 to} λ _n can be compensated by one chromatic dispersion compensating fiber, there is no problem, but it becomes very difficult as the number of wavelengths to be wavelength division multiplexed increases. As shown, the wavelength dispersion is compensated by dividing into channels of individual wavelengths (or individual wavelength bands).

[0005] Wavelength dispersion compensating fibers 14-1 to 14-n
Are multiplexed (in this case, wavelength division multiplexed) by the multiplexer 16.

[0006] Demultiplexer 10 and bandpass optical filter 12-1
Instead of ~ 12-n, an arrayed waveguide grating (AWG) may be used. By using the AWG, a wavelength division multiplexed optical signal can be separated into individual wavelengths by one element.

[0007]

In the conventional example, the output light from the band-pass optical filters 12-1 to 12-n contains many components (signal light and noise) other than the wavelength assigned to each wave channel. It is. For example, the bandpass optical filter 12
The output light of -2 channel next to other original lambda ₂ # 1
Λ ₁ , λ _3, and may also include wavelengths outside the above. Bandpass optical filter 12- used in the conventional example
Nos. 1 to 12-n are formed by laminating a large number of dielectric films, and it is extremely difficult to obtain good blocking characteristics. That is, the sharpness of the bandpass characteristic is not good enough to completely remove components (signal light and noise) other than the assigned wavelength.

As a result, light of the same wavelength is included in a channel other than the original channel (usually an adjacent channel, which has the most influence). Greatly deteriorates.

When the multiplexer 16 is made of, for example, AWG,
Since a predetermined wavelength light of the input light of each input port is output from the multiplexed output, it has a function of removing wavelength light that should not be input to the input port, of the input light of each input port. . That is, it is possible to suppress the same wavelength light from leaking from another port. However, the ability to suppress the leakage is about 30 dB, which is not sufficient.

In any case, the transmission characteristics are greatly deteriorated because the optical signals of the same wavelength, which are dispersion-compensated by the dispersion compensating fibers 14-1 to 14-n having different chromatic dispersion compensation characteristics, are multiplexed. Resulting in. 5 for adjacent channels
Although suppression of 0 dB or more is required, the conventional example cannot satisfy this requirement.

To improve the sharpness of the filter characteristics of the band-pass optical filters 12-1 to 12-n, it is necessary to connect the same type of band-pass optical filters in multiple stages, but this increases the transmission loss.

By using an AWG for the demultiplexer 10 and further using bandpass optical filters 12-1 to 12-n together,
Although wavelength selectivity can be enhanced, it is not sufficient in terms of complete separation of light of each wavelength.

An object of the present invention is to provide a wavelength division multiplexing optical processing apparatus which solves such a problem.

Another object of the present invention is to provide a wavelength division multiplexing optical processing device which enables transmission characteristics substantially equal to that of single wavelength transmission even in wavelength division multiplex transmission.

[0015]

According to the present invention, a predetermined wavelength or wavelength band excluding the wavelength or wavelength band assigned to each of the channels after the input wavelength division multiplexed light is demultiplexed into a plurality of channels. A wavelength selecting means for selectively removing is provided. Thus, light of a wavelength or a wavelength band assigned to each channel can be extracted with low loss.

By reflecting the wavelength assigned to each channel or the wavelength on both sides of the wavelength band by the first and second reflection means, only the wavelength or wavelength band assigned to each channel can be extracted from each channel. Even if leakage occurs between channels at the time of multiplexing, transmission characteristics are not adversely affected. That is, a multiplexing means having some leakage between ports can be used.

Since the first and second reflecting means comprise one or more reflecting elements for reflecting individual wavelengths of the wavelength division multiplexed light, other wavelength components which influence the transmission characteristics are effectively reduced. Can be removed. By using a grating structure for the reflection element, sharp reflection characteristics can be obtained.

The first reflecting means reflects one or more adjacent wavelengths on one side of the assigned wavelength or wavelength band, and the second reflecting means reflects the other of the assigned wavelength or wavelength band. By mainly reflecting one or more adjacent wavelengths on the side of, it is possible to suppress the influence of leakage between adjacent channels, which has an adverse effect upon multiplexing, with a small number of reflective elements.

[0019]

Embodiments of the present invention will be described below in detail with reference to the drawings.

FIG. 1 is a schematic block diagram showing an embodiment of the present invention. Reference numeral 20 denotes a demultiplexer that demultiplexes an optical signal obtained by wavelength division multiplexing the optical signals of wavelengths λ _{1 to} λ _n into n channels. The demultiplexer 20 is a unit that separates the input wavelength division multiplexed light into individual wavelengths λ _{1 to} λ _n , such as an AWG, but simply splits the input wavelength division multiplexed light into n pieces. However, here, it is assumed that AWG is used to separate the light into individual wavelengths. It is assumed that wavelengths λ _{1 to} λ _n are assigned to the respective channels # 1 to #n after the demultiplexing by the demultiplexer 20. That is, the channel #i is the wavelength lambda _i is output, a certain degree by the wavelength separation performance of the duplexer 20, and enters another wavelength.

The lights output from the channels # 1 to #n of the demultiplexer 20 are respectively wavelength-selective filters 22-1 to 22-1.
22-n. Wavelength selection filters 22-1 to 22
-N is a filter element that almost completely blocks (reflects here) the wavelengths adjacent to the wavelengths allocated to the channels # 1 to #n.
Consisting of a serially connected fiber grating. Therefore, the wavelength selection filters 22-1 to 22-n
The wavelengths assigned to the channels # 1 to #n are transmitted with substantially no loss.

FIG. 2 shows the wavelength selection filters 22-1 to 22-2.
-N shows the transmission wavelength characteristic. FIG. 2A shows a multiplexer 20.
The spectrum of the input light of FIG.
(C) is the transmission wavelength characteristic of the filter 22-2, (d) is the transmission wavelength characteristic of the filter 22-i,
(E) shows the transmission wavelength characteristic of the filter 22-n.

As can be seen from FIG. 2, generally, the wavelength selection filter 22-i comprises a fiber grating 24 that completely reflects the wavelength λ _i-1 and a fiber grating that completely reflects the wavelength λ _{i + 1.} 26. Channel # 1 at both ends, # n, since there is no need to remove the wavelength of the outside, the wavelength selection filter 22-1 includes only a fiber grating 28 to fully reflect wavelengths lambda _2, the wavelength selective filter 22- n consists only of the fiber grating 30 that completely reflects the wavelength λ _n-1 .

The fiber grating is capable of selectively completely reflecting a very narrow wavelength range of several nanometers, and is very good as a filter. Moreover,
The wavelength shifted from the reflection wavelength is transmitted with substantially no loss. Therefore, as shown in FIG. 1, even if the fiber gratings having different reflection wavelengths are cascaded, the wavelength allocated to the channel can be transmitted with almost no loss.

The light transmitted through the wavelength selection filters 22-1 to 22-n is converted into chromatic dispersion compensating fibers 32-1 to 32-n.
Incident on. Wavelength dispersion fiber 32-1 to 32-n, respectively, are designed to compensate for the wavelength dispersion of the wavelength lambda ₁ to [lambda] _n, to compensate for the wavelength dispersion of the corresponding wavelength lambda ₁ to [lambda] _n.

A multiplexer (wavelength multiplexer) 34 multiplexes (wavelength multiplexes) the output lights of the dispersion compensating fibers 32-1 to 32-n.
I do. The output light of the multiplexer 34 is a wavelength division multiplexed light of light in which the wavelength dispersion of each wavelength light included in the input light of the demultiplexer 20 is individually compensated. The light input to the adjacent input port of the multiplexer 34 is transmitted to the wavelength selection filters 22-1 to 22-.
Since n removes the same wavelength component completely,
Even if the multiplexer 34 in which the leakage between the ports is not small is used, it is possible to prevent the transmission characteristics from being deteriorated by the multiplexer 34.

When an element for simply adding the input light of each input port is used as the multiplexer 34, or when there is leakage even between distant input ports, the same wavelength component is added between distant channels. Must be absent. For this purpose, the wavelength selection filters 22-1 to 22-
n may be cascaded with a fiber grating so as to reflect all wavelengths other than the wavelength assigned to the channel. 3, the wavelength selection filter 22-i of the channel #i, a block diagram of a configuration for changing to reflect all wavelengths other than the wavelength lambda _i. That is, fiber gratings 36 to 38 that respectively reflect the wavelengths λ ₁ to λ _i−1 and fiber gratings 40 to 42 that respectively reflect the wavelengths λ _{i + 1} to λ _n are connected in cascade. The wavelength selection filter 22 thus changed
FIG. 4 shows transmission wavelength characteristics of -1 to 22-n.

As a device that reflects a single wavelength, a multilayer reflective film structure can be used other than the fiber grating. If the pass wavelength band or the cutoff wavelength band is made to have a certain width, manufacturing becomes difficult, and it is difficult to obtain a sharp cut-off characteristic. Can be manufactured. In this respect, wavelength separation is easier when a single wavelength is allocated than when a wavelength band including a plurality of wavelengths is allocated to each channel.

Next, two wavelengths of 20 Gb / s each are
An embodiment applied to a dispersion compensator for compensating the accumulated chromatic dispersion of individual wavelengths in an optical soliton transmission system for transmitting 9,000 km will be described. FIG. 5 is a schematic block diagram showing an embodiment of an optical fiber soliton transmission system for wavelength division multiplex transmission of two wavelengths. In the transmitting station 60, the optical transmitters 62 and 64 output 20 GB / s optical soliton pulses of wavelengths λ ₁ and λ ₂ , respectively, and the multiplexer 66 multiplexes the output lights of the optical transmitters 62 and 64. Output to the optical fiber transmission line. The optical fiber transmission line includes a number of transmission optical fibers 6.
And a dispersion compensating fiber 7 for compensating the accumulated chromatic dispersion at appropriate intervals.
2, 74 are inserted. In this embodiment, the dispersion compensating fiber 72, 74 is designed to the accumulated chromatic dispersion to zero for a wavelength lambda _1. Further, at an appropriate interval, a dispersion compensator 76 for compensating the accumulated chromatic dispersion of the individual wavelength (here, λ ₂ ) as described in the embodiment shown in FIG. 1 is inserted.

In the embodiment shown in FIG. 5, the wavelength λ _{1 is set} to 155.
The wavelength was set to 7.2 nm and the wavelength λ ₂ was set to 1560.0 nm. Transmission optical fiber 68 is 35km example, the chromatic dispersion with respect to the distance is 0.46ps / nm / k with respect to the wavelength lambda ₁
m, is 0.68ps / nm / km for a wavelength lambda _2. Dispersion compensating fiber 72 -56p respect to the wavelength lambda ₁
s / nm, and the dispersion compensating fiber 74
It gives the wavelength dispersion of -71ps / nm with respect to the wavelength λ _1. The dispersion compensating fiber 74 is optimized for the wavelength lambda _1. The individual wavelength dispersion compensator 76 is approximately 300 k
They are installed at m intervals.

FIG. 6 is a schematic diagram showing the relationship between the accumulated chromatic dispersion and the distance in the dispersion compensation period of the dispersion compensator 76. The vertical axis indicates the accumulated chromatic dispersion, and the horizontal axis indicates the distance. At the output end of the transmitting station 60 (or the dispersion compensator 76), the cumulative chromatic dispersion is zero at both the wavelengths λ ₁ and λ ₂ , but the cumulative chromatic dispersion increases at an increasing rate of each wavelength with distance. With the first dispersion compensating fiber 72, the cumulative chromatic dispersion of both the wavelengths λ ₁ and λ ₂ is reduced by 56 ps / nm, and thereafter, the cumulative chromatic dispersion of both the wavelengths λ ₁ and λ ₂ is increased again. The second dispersion compensating fiber 74 reduces the cumulative chromatic dispersion of the wavelengths λ ₁ and λ ₂ by 71 ps / nm, and then increases the cumulative chromatic dispersion of both the wavelengths λ ₁ and λ ₂ again. Dispersion compensating fiber 72, 7
4 is optimized for wavelength λ ₁ , so that about 300
km, that is, at the input end of the dispersion compensator 76,
The cumulative chromatic dispersion of the wavelength λ ₁ is zero. But,
The cumulative chromatic dispersion of the wavelength λ ₂ is about 64 ps / nm. Dispersion compensator 76 compensates only accumulated chromatic dispersion of the wavelength lambda _2, it is zero. The configuration of the dispersion compensator 76 will be described later.

Thus, the dispersion compensating fiber 72,
While the cumulative chromatic dispersion is compensated for the wavelength λ ₁ by the 74, the cumulative chromatic dispersion of the wavelength λ ₂ that cannot be compensated for by the dispersion compensating fibers 72 and 74 is individually and periodically compensated for by the dispersion compensating device 76.

In the receiving station 78, the wavelength separation device 80 separates the wavelength division multiplexed light from the optical transmission line into the respective wavelengths λ ₁ and λ ₂ , and the demodulation devices 82 and 84 receive the respective wavelengths λ ₁ and λ ₂ . Demodulate light.

As a result of the orbital experiment, the residual chromatic dispersion of the wavelength λ ₂ can be reduced to almost zero by the dispersion compensator 76.
Gordon house timing jitter of soliton transmission can be reduced to almost zero, 2 wavelengths, 20 Gb / s, 9000 km
Transmission is now possible.

FIG. 7 shows a specific configuration example of the dispersion compensating device 76. Basically, the configuration shown in FIG. 1 is simplified for two wavelengths.

The 3 dB coupler 110 splits the wavelength division multiplexed light having the wavelengths λ ₁ and λ ₂ into _two , and applies one to the optical bandpass filter (OBPF) 112 and the other to the optical bandpass filter 114. Optical bandpass filter 11
2,114 comprises a second-order Butterworth filter,
Each is designed and manufactured to transmit wavelengths λ ₁ and λ ₂ . The half width is 3 nm, and the loss at wavelengths separated by 2.8 nm is -15 dB. With this level of separation capability, only about 3000 km can be transmitted due to crosstalk.

In this embodiment, the output of the optical band-pass filter 112 is further provided with an optical band-rejection filter (OBRF) 11 in which fiber gratings 116a and 116b reflecting the wavelength λ ₂ are cascaded.
6 and the output of the optical band-pass filter 114 has a fiber grating 11 that reflects the wavelength λ _1.
An optical band rejection filter 118 in which 8a and 118b are cascaded is connected. Optical band
The rejection filter 116, the wavelength lambda ₁ of the channel from the wavelength lambda ₂ of the component 50dB or more, removal can, also, the wavelength lambda ₁ of the component from the wavelength lambda ₂ of the channel 5
0 dB or more can be removed.

FIG. 8 shows the transmission characteristics of the optical band-pass filter 112 and the optical band rejection filter 116. The optical bandpass filter 112 has a very gentle wavelength characteristic. On the other hand, since a steep reflection wavelength characteristic can be obtained with the fiber grating, the optical band rejection filter 116
Has a very narrow half-value width of about 1 nm, and shows a steep wavelength characteristic. FIG. 9 shows an optical bandpass filter 112.
Transmission characteristics and optical band rejection filter 11
6 shows transmission characteristics obtained by combining the transmission characteristics of FIG. Adjacent wavelength λ ₂
It can be seen that the loss is as high as 50 dB.

The optical band-pass filter 114 and the optical band rejection filter 118 also have wavelengths λ ₁ and λ ₂
Are basically the same as those of the optical bandpass filter 112 and the optical band rejection filter 116 except that the relationship is reversed. FIG. 10 shows transmission characteristics obtained by combining the transmission characteristics of the optical bandpass filter 114 and the transmission characteristics of the optical band rejection filter 118.

Optical band rejection filter 11
The output light of _No. 6 is input to a 3 dB coupler 124 serving as a multiplexing means via a dispersion shift fiber 120 designed to have zero dispersion with respect to the wavelength λ1. On the other hand, the output light of the optical band rejection filter 118 is
Through the dispersion compensating fiber 122 to provide a wavelength dispersion of -64ps / nm to the wavelength lambda _2, the multiplexing means 3d
Input to the B coupler 124. Dispersion shift fiber 1
Although 20 may not be provided, it is connected on the balance with the dispersion compensating fiber 122 (loss, delay, etc.). 3d
The B coupler 124 combines the lights from the fibers 120 and 122 and outputs the combined light.

FIG. 11 shows the light transmission characteristics of the entire dispersion compensator 76. Some parts of the transmittance is reduced during the wavelength lambda ₁ and wavelength lambda _2. As in the conventional example, the optical BPFs 112, 11
When only 4 is used, the transmittance between the wavelengths λ ₁ and λ ₂ may be the highest, and the crosstalk increases, so that long distance transmission of 9000 km cannot be realized.

Next, an embodiment of a dispersion compensator for three wavelengths will be described. FIG. 12 shows a schematic block diagram of the configuration.
The wavelength division multiplexed light having the wavelengths λ ₁ , λ ₂ , and λ ₃ is divided into two by the 3 dB coupler 130, one output light is supplied to the 3 dB coupler 132 and further divided into two, and the other output light is divided into optical bandpass filters. 134. 3dB coupler 1
Each of the lights divided into two at 32 is applied to optical bandpass filters 136 and 138.

Optical bandpass filters 134, 136,
Reference numeral 138 is a second-order Butterworth filter, each of which is designed and manufactured to transmit a wavelength λ ₂ , λ ₃ , and λ ₁ with a half width of 3 nm. Optical bandpass filter 1
34, 136, and 138 are output from the optical amplifier 1 respectively.
The signals are applied to the optical band-pass filters 146, 148, and 150 having the same specifications as the optical band-pass filters 134, 136, and 138 via the reference numerals 40, 142, and 144, respectively. By providing the optical band-pass filters 134, 136, and 138 for extracting the wavelength components of the respective channels at a stage preceding the optical amplifiers 140, 142, and 144, the amplification gain of the optical amplifiers 140, 142, and 144 can be increased.

The output of the optical bandpass filter 146 is connected to an optical band rejection filter 152 that selectively reflects the wavelengths λ ₁ and λ ₃ of the adjacent channels. Optical band rejection filter 152
Is applied to a reflecting element 152a in which optical fiber gratings that reflect the wavelength λ ₁ are cascaded in two stages, and the wavelength λ ₃
And a cascade-connected reflecting element 152b in which two-stage cascaded optical fiber gratings for reflecting light. Since the wavelengths λ ₁ and λ ₃ are both adjacent to the wavelength λ ₂ , the reflection elements 152 a and 152 b shown in FIG.
As in the case of (1), two stages of fiber gratings are connected to improve the removal performance. The wavelength λ of the adjacent channel is determined by the optical band rejection filter 152.
₁ and λ ₃ can be suppressed by 50 dB or more.

The output of the optical bandpass filter 148 is connected to an optical band rejection filter 154 that selectively reflects the wavelengths λ ₁ and λ ₂ of adjacent channels. Optical band rejection filter 154
Is applied to a reflecting element 154a in which optical fiber gratings reflecting the wavelength λ ₂ are cascade-connected in two stages, and the wavelength λ ₁
In a cascade connection of a reflection element 154b composed of an optical fiber grating that reflects light. Wavelength λ
_{Since the} wavelength λ ₂ is adjacent to ₃ , the reflection element 154
As shown in FIG. 7, two stages of fiber gratings are connected in the same manner as in FIG. 7 to improve the rejection performance. However, since the wavelength λ ₁ is adjacent to the adjacent channel and is slightly apart, the reflection element 154 b is set to 1 The structure consists of two optical fiber gratings. This is because the component of the wavelength λ ₁ has already been greatly attenuated by the optical bandpass filters 136 and 148. The band rejection filter 154 converts the signal light having the wavelengths λ ₁ and λ ₂ of the adjacent channels into −
It can be reduced to 50 dB or less.

The output of the optical bandpass filter 150 is connected to an optical band rejection filter 156 that selectively reflects the wavelengths λ ₂ and λ ₃ of the adjacent channels. Optical band rejection filter 156
Is applied to the reflecting element 156a in which optical fiber gratings reflecting the wavelength λ ₂ are cascade-connected in two stages, the wavelength λ ₃
In a cascade connection of a reflection element 156b composed of an optical fiber grating that reflects light. The reflecting element 156a is a two-stage optical fiber grating,
The reason why the reflection element 156b is one optical fiber grating is that the optical band rejection filter 1
Same as 54. The optical band rejection filter 154 can wavelength λ2 of adjacent channels, lambda ₃ of the signal light below -50 dB.

Optical band rejection filter 15
2 is input to a dispersion compensating fiber 158 that provides a wavelength dispersion of −32 ps / nm with respect to the wavelength λ ₂ , and the output light of the optical band rejection filter 154 is −84 ps with respect to the wavelength λ ₃ / Nm, the output light of the optical band rejection filter 156 is ₁ to the wavelength λ ₁ .
Input to single mode fiber 162 which provides 6 ps / nm chromatic dispersion.

Here, six dispersion-shifted fibers having a length of 35 km, and approximately 215 km for relay amplification are used as units.
An optical fiber transmission system in which the dispersion compensating device shown in FIG. 12 is arranged and _one dispersion compensating fiber of -108 ps / nm with respect to the wavelength λ1 is arranged in the middle of 215 km is assumed. Each wavelength λ1 in the 215km, λ _2, λ
FIG. 13 shows changes in the cumulative chromatic dispersion of No. ₃ with respect to the distance.
As shown in FIG. 13, the accumulated chromatic dispersion of each signal light of each wavelength λ ₁ , λ ₂ , λ ₃ becomes zero at the output stage of the fibers 158, 160, 162.

The 3 dB coupler 164 is connected to the fiber 16
0,162 output lights, and 3 dB coupler 166
Multiplexes the output light of the fiber 158 with the output light of the 3 dB coupler 164, and the multiplexed output is supplied to an optical fiber transmission line (not shown).

Although the embodiment for compensating for the chromatic dispersion of the individual wavelength light has been described, the present invention can be applied to other applications (for example, a synchronous modulator for soliton transmission,
It is apparent that the present invention can be applied to a gain equalization and a saturable absorption element (noise removal). Also, although described as an embodiment using a fiber element, a planar optical circuit, it can also be implemented as other forms of optical element,
it is obvious.

[0051]

As can be easily understood from the above description, according to the present invention, when wavelength-division-multiplexed light is wavelength-separated, individually processed, and then wavelength-multiplexed again, the same wavelength light having different processing steps is used. Can be prevented from being multiplexed, and the transmission characteristics of the wavelength division multiplexing transmission system can be greatly improved.

Therefore, in the wavelength division multiplexing transmission system, transmission characteristics substantially equal to those in the case of single wavelength transmission can be achieved, and the total transmission capacity can be greatly increased by increasing the number of wavelengths.

[Brief description of the drawings]

FIG. 1 is a schematic block diagram of an embodiment of the present invention.

FIG. 2 is a transmission wavelength characteristic diagram of wavelength selection filters 22-1 to 22-n.

FIG. 3 is a schematic configuration block diagram of a modified example of the wavelength selection filter 22-i.

4 is a transmission wavelength characteristic diagram of the wavelength selection filters 22-1 to 22-n modified as shown in FIG.

FIG. 5 shows an optical fiber for wavelength division multiplex transmission of two wavelengths.
1 is a schematic configuration block diagram of an embodiment of a soliton transmission system.

FIG. 6 is a schematic diagram showing a relationship between a cumulative chromatic dispersion and a distance in a dispersion compensation cycle of the dispersion compensation device 76.

FIG. 7 is a schematic block diagram of a dispersion compensator 76.

8 shows transmission characteristics of the optical bandpass filter 112 and the optical band rejection filter 116. FIG.

9 shows transmission characteristics obtained by combining the transmission characteristics of the optical bandpass filter 112 and the transmission characteristics of the optical band rejection filter 116. FIG.

10 shows transmission characteristics obtained by combining the transmission characteristics of the optical bandpass filter 114 and the transmission characteristics of the optical band rejection filter 118. FIG.

11 shows the light transmission characteristics of the entire dispersion compensator 76. FIG.

FIG. 12 is a schematic block diagram of an embodiment of a dispersion compensator for three wavelengths.

13 is a schematic diagram showing a change in accumulated chromatic dispersion with distance when the dispersion compensator shown in FIG. 12 is used.

FIG. 14 is a schematic block diagram of a conventional example.

[Explanation of symbols]

10: Demultiplexer 12-1 to 12-n: Band-pass optical filter 12-1 to 1
2-n 14 to 14-n: chromatic dispersion compensating fiber 16: multiplexer 20: duplexer 22-1 to 22-n: wavelength selective filter 24, 26, 28, 30: fiber grating 32-1 to 32 -N: chromatic dispersion compensating fiber 34: multiplexer (wavelength multiplexer) 36, 38, 40, 42: fiber grating 60: transmitting station 62, 64: optical transmitter 66: multiplexer 68: optical fiber for transmission 70: Optical amplifier 72, 74: Dispersion compensating fiber 76: Dispersion compensating device 78: Receiving station 80: Wavelength demultiplexing device 82, 84: Demodulating device 110: 3 dB coupler 112, 114: Optical bandpass filter (OBPF) 116: Optical Band rejection filter (OBR)
F) 116a, 116b: Fiber grating 118: Optical band rejection filter (OBR)
F) 118a, 118b: fiber gratings 130, 132: 3 dB couplers 134, 136, 138: optical bandpass filters 140, 142, 144: optical amplifiers 146, 148, 150: optical bandpass filters 152: optical band filters rejection filter 152a: lambda ₁ reflective element 152 b: lambda ₃ reflective element 154: optical band rejection filter 154a: lambda ₂ reflective element 154b: lambda ₁ reflective element 156: optical band rejection filter 156a: lambda ₂ Reflecting element 156b: λ ₃ reflecting element 158: Dispersion compensating fiber 160: Dispersion compensating fiber 162: Single mode fiber

──────────────────────────────────────────────────続 き Continued on the front page (51) Int.Cl. ⁶ Identification code FI H04B 10/135 10/13 10/12 (72) Inventor Shu Yamamoto 2-3-2 Nishishinjuku, Shinjuku-ku, Tokyo Kokusai Telegraph Inside Telephone Co., Ltd. (72) Inventor Shigeyuki Akiba 2-3-2 Nishi-Shinjuku, Shinjuku-ku, Tokyo International Telephone & Telephone Co., Ltd.

Claims (29)

[Claims] 1. An input wavelength division multiplexed light is demultiplexed into a plurality of channels, and in each of the plurality of channels, a predetermined optical processing is performed on a wavelength or a wavelength band assigned to the channel, and then the combined light is processed. A wavelength-division multiplexing optical processing device for oscillating, wherein a wavelength selecting means for selectively removing a predetermined wavelength or a wavelength band excluding an allocated wavelength or a wavelength band is provided for each of a plurality of channels. Wavelength division multiplex optical processing device. 2. The wavelength selecting means according to claim 1, wherein said wavelength selecting means reflects one or more wavelengths of a wavelength band on one side of said assigned wavelength or wavelength band, and cascade-connected to said first reflecting means. 2. The wavelength division multiplexing optical processing device according to claim 1, further comprising a second reflection unit that reflects one or more wavelengths of the assigned wavelength or the wavelength band on the other side of the wavelength band. 3. The wavelength division multiplexing light processing apparatus according to claim 2, wherein said first and second reflection means comprise one or more reflection elements for reflecting individual wavelengths of said wavelength division multiplexing light. 4. The wavelength division multiplexing optical processing device according to claim 3, wherein said reflection element has a grating structure. 5. The wavelength selecting means includes first reflecting means for reflecting one or more adjacent wavelengths on one side of the assigned wavelength or wavelength band, and cascade-connected to the first reflecting means. 2. The wavelength division multiplexing optical processing apparatus according to claim 1, further comprising a second reflection unit that mainly reflects one or more adjacent wavelengths on the other side of the allocated wavelength or the wavelength band. 6. The wavelength division multiplexing optical processing device according to claim 5, wherein said first and second reflection means have a grating structure. 7. The wavelength selecting means of the channels at both ends of the plurality of channels comprises reflecting means for reflecting one or more wavelengths of the assigned wavelength or a wavelength band inside the wavelength band. 3. The wavelength division multiplexing optical processing device according to 1. 8. The wavelength division multiplexing light processing apparatus according to claim 7, wherein said reflection means comprises one or more reflection elements for reflecting individual wavelengths of said wavelength division multiplexing light. 9. The wavelength division multiplexing optical processing device according to claim 8, wherein the reflection element has a grating structure. 10. The method according to claim 7, wherein the wavelength selecting means of the channels at both ends of the plurality of channels comprises a reflecting element for reflecting the assigned wavelength or one wavelength of a wavelength band inside the wavelength band. The wavelength division multiplexing optical processing apparatus as described in the above. 11. The wavelength division multiplexing optical processing device according to claim 10, wherein said reflection element has a grating structure. 12. The wavelength division multiplexing optical processing according to claim 1, wherein the predetermined processing includes one of chromatic dispersion compensation processing, synchronous modulation processing for soliton transmission, gain equalization, and noise removal processing. apparatus. 13. A wavelength division multiplexing optical processing device for optically processing wavelength division multiplexing light for each individual wavelength, wherein the input wavelength division multiplexing light is demultiplexed into a plurality of channels corresponding to different wavelengths. Demultiplexing means, in each of the plurality of channels, wavelength selecting means for blocking a predetermined wavelength other than the wavelength assigned to the channel, and in each of the plurality of channels, an optical processing means for performing predetermined optical processing A wavelength division multiplexing optical processing device comprising: multiplexing means for multiplexing the output lights of the plurality of channels. 14. The wavelength selecting means, a first reflecting means for reflecting one or more wavelengths in a wavelength band on one side of the allocated wavelength, a cascade connection to the first reflecting means,
14. The wavelength division multiplexing optical processing apparatus according to claim 13, further comprising second reflection means for reflecting one or more wavelengths in a wavelength band on the other side of the allocated wavelength. 15. The wavelength division multiplexing optical processing device according to claim 14, wherein said first and second reflection means comprise one or more reflection elements for reflecting individual wavelengths of said wavelength division multiplexing light. 16. The wavelength division multiplexing optical processing device according to claim 15, wherein said reflection element has a grating structure. 17. The wavelength selecting means, first reflecting means for reflecting one or more adjacent wavelengths on one side of the allocated wavelength, cascaded to the first reflecting means,
14. The wavelength division multiplexing optical processing apparatus according to claim 13, further comprising a second reflection unit that reflects one or more adjacent wavelengths on the other side of the assigned wavelength. 18. The wavelength division multiplexing optical processing device according to claim 17, wherein said first and second reflection means have a grating structure. 19. The apparatus according to claim 13, wherein the wavelength selecting means of the channels at both ends of the plurality of channels comprises reflecting means for reflecting at least one wavelength in a wavelength band inside the allocated wavelength. Wavelength division multiplex optical processing device. 20. The wavelength division multiplexing light processing apparatus according to claim 19, wherein said reflection means comprises one or more reflection elements for reflecting individual wavelengths of said wavelength division multiplexing light. 21. The wavelength division multiplexing optical processing device according to claim 19, wherein the reflection element has a grating structure. 22. The apparatus according to claim 19, wherein the wavelength selecting means of each of the channels at both ends of the plurality of channels comprises a reflecting element that reflects one adjacent wavelength in a wavelength band inside the allocated wavelength. Wavelength division multiplexing optical processing device. 23. The wavelength division multiplexing optical processing device according to claim 21, wherein said reflection element has a grating structure. 24. The wavelength according to claim 13, wherein the optical processing means is an optical element that executes one of a chromatic dispersion compensation process, a synchronous modulation process for soliton transmission, a gain equalization, and a noise removal process. Division multiplex optical processing device. 25. A wavelength division multiplexing optical processing device for optically processing wavelength division multiplexing light for each individual wavelength, wherein the input wavelength division multiplexing light is demultiplexed into a plurality of channels corresponding to different wavelengths. A demultiplexing means, an optical bandpass filter means for passing a wavelength allocated to the channel in each of the plurality of channels, and an output light of the bandpass filter means in each of the plurality of channels. A predetermined wavelength removing unit that removes at least a wavelength component of an adjacent channel; a light processing unit that performs predetermined optical processing in each of the plurality of channels; and a multiplexing unit that multiplexes output light of the plurality of channels. A wavelength division multiplexing optical processing device characterized by comprising: 26. The apparatus according to claim 26, wherein the predetermined wavelength removing unit includes a first removing unit that removes a wavelength component of one adjacent channel and a second removing unit that removes a wavelength component of the other adjacent channel. 26. The wavelength division multiplexing optical processing device according to claim 25. 27. The first and second removing means include one or more first reflection elements that reflect an adjacent wavelength component and one or more second reflection elements that reflect an adjacent next wavelength component. The wavelength division multiplexing optical processing device according to claim 26. 28. The wavelength division multiplexing optical processing device according to claim 27, wherein said first and second reflection elements have a grating structure. Wavelength division multiplex optical processing device. 29. The wavelength division multiplexing optical processing apparatus according to claim 25, wherein said predetermined wavelength removing means of both ends of said plurality of channels comprises removing means for removing wavelength components of adjacent channels.