JP2000206362A - Optical ADM (Add / DropMultiplexing) node device - Google Patents

Abstract

(57) [Summary] [Problem] Optical AD accompanying multiplicity improvement in wavelength division multiplexing transmission
An object of the present invention is to provide a simple optical ADM structure by solving the problem of increasing the volume and cost of M (Add / Drop Multiplexing) nodes. SOLUTION: A wavelength λ1 which is branched and output to a branch terminal 10-1.
And the wavelength λ1 + Δλ (where Δλ is the free spectral range of the arrayed waveguide grating type multiplexer / demultiplexer 10), the wavelength λ1
The signal of wavelength λ1 + Δλ is directly transmitted to the optical switch 11-2 by the wavelength selective two-input two-output optical switch 11-1 operating at
The signal 1 is transmitted to the optical switch 11-2 directly or after dropping / inserting as necessary. The two optical signals incident on the wavelength-selective two-input two-output optical switch 11-2 operating at the wavelength λ1 + Δλ are, as described above, only the signal of the wavelength λ1 + Δλ is dropped and inserted as necessary. Are transmitted to the optical multiplexer 14. The output signal of the optical switch 11-2 is multiplexed with the output signal of another optical switch by the optical multiplexer 14, and transmitted from the optical ADM node as a wavelength multiplexed signal. [Effect] The number of branch terminals of the optical multiplexer / demultiplexer in the optical ADM node can be reduced.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to an optical ADM (Add / Drop).
And more particularly to an optical ADM in a repeater for optical signal transmission in wavelength division multiplex transmission.

[0002]

2. Description of the Related Art Wavelength multiplex transmission is one of the means for constructing a large-capacity optical communication network in the future. In wavelength division multiplexing transmission in which information is exchanged or the optical path is changed for each wavelength of an optical signal, branching of a signal of an arbitrary wavelength from the wavelength division multiplexed signal (Dr.
It is important to consider optical ADM technology that performs op) and insertion (Add).

As a configuration of a conventional optical ADM node, for example, B. Glance, Fellow, IEEE, Large-Capacity Local Acc
ess Network, IEEE Photonics Technology Lett., vol.
5, No. 12, pp1448-1451, 1993 (Reference 1), K. Kitayama,
Subcarrier-Multiplexed Signaling Based Add / Drop Mu
ltiplexer in Optical FDM Networks, IEEE PhotonicsT
echnology Lett., vol. 8, No. 6, 1996 (Reference 2). Document 1 describes a structure in which an optical ADM node using two optical multiplexer / demultiplexers having the same branching characteristic in combination transmits and receives one wavelength signal by demultiplexing it to one terminal. FIG. 1 shows the configuration of an optical ADM node according to Reference 1 when the number of branch terminals input to an optical multiplexer / demultiplexer for demultiplexing a wavelength multiplexed signal for each wavelength or multiplexing signals of each wavelength is four. . The wavelength multiplexed signal incident on the 1 × 4 demultiplexer 1 is branched to each output terminal 1-j for each signal wavelength λj (j = 1, 2, 3, 4), and the demultiplexed output signal is output to one of The input terminal enters a two-input two-output optical switch 2 connected to a 1 × 4 demultiplexer 1.
The incident optical signal is output by the optical switch 2 to an output terminal connected to the input terminal of the 1 × 4 multiplexer 3 or an output terminal connected to the receiver as needed. In the latter case, the optical signal enters the receiver and is received.At the same time, a signal of the same wavelength is transmitted from the transmitter connected to one input terminal of the optical switch 2, and connected to the 1 × 4 multiplexer 3. Is output from the output terminal. The signal output from the optical switch 2 enters the 1 × 4 multiplexer 3, is multiplexed with other signals, and is transmitted as a wavelength multiplexed signal.

In Reference 2, an N × N optical multiplexer / demultiplexer is used.
A structure is described in which a two-input two-output optical switch having a transceiver is provided in an optical path between each input / output branch terminal for each wavelength of the multiplexer / demultiplexer. FIG. 2 shows the configuration of the optical ADM node of Reference 2 when the number of branch terminals is four. The wavelength multiplexed signal incident on the 5 × 5 optical multiplexer / demultiplexer 4 has a signal wavelength λj (j = 1, 2,
3, 4), the signal is demultiplexed to each branch output terminal 4-j, and the demultiplexed output signal has one input terminal connected to the 5 × 5 optical multiplexer / demultiplexer 4
The light enters the input 2 output optical switch 5. The incident optical signal is output by the optical switch 5 to an output terminal connected to the 5 × 5 multiplexer 4 or an output terminal connected to the receiver as necessary. In the latter case, the optical signal enters the receiver and is received, and at the same time, a signal of the same wavelength is transmitted from the transmitter connected to one input terminal of the optical switch 5 and connected to the 5 × 5 multiplexer 4. Is output from the output terminal. Optical switch 5
The output signal enters the 5 × 5 multiplexer / demultiplexer 4, is multiplexed with other signals, and is transmitted as a wavelength multiplexed signal.

As described above, optical ADM in wavelength division multiplexing transmission
Conventionally, an arrayed waveguide grating grating (AWG) has been used as a multiplexer / demultiplexer in a node. FIG. 3 shows a conventional relationship between the insertion loss and the wavelength of the AWG used in the optical ADM node when the number of branch terminals of the AWG is four. λ1, λ2, λ3, and λ4 represent signal wavelengths that are multiplexed and demultiplexed at branch terminals 1, 2, 3, and 4 of the AWG, respectively. The wavelengths split at the AWG branch terminals 1, 2, 3, and 4 are shown in 6, 7, 8, and 9 in the figure, and the AWG simultaneously combines the wavelengths at FSR (Free Spectrum Range) intervals at each branch terminal. It has the property of demultiplexing. Conventionally, the FSR is set wider than the signal band, and one wavelength signal is dropped and inserted from one terminal. Therefore, the same number of AWG branch terminals as the number of signals is required.

On the other hand, in recent years, transmission capacity is expected to increase more and more, and research on wavelength division multiplexing transmission technology, which is one method for constructing a large capacity network, is being advanced. In particular, due to the development of optical fiber amplification technology, in addition to the 1.55 μm wavelength band, 1.
Wavelength multiplex transmission, which multiplexes and transmits a plurality of wavelengths even in the 58 μm band, is becoming possible. In wavelength division multiplexing transmission, the capacity is being promoted by improving the degree of wavelength multiplexing, but the degree of multiplexing is further increased by realizing wideband use, enabling efficient transmission and reception for each optical signal wavelength within a compact and inexpensive node. It has become a challenge.

[0007]

SUMMARY OF THE INVENTION It is an object of the present invention to reduce the number of branch ports of an optical multiplexer / demultiplexer, and to solve the problem of an increase in the volume and cost of an optical ADM node due to an increase in multiplicity. Another object of the present invention is to provide a simple optical ADM structure.

[0008]

According to an embodiment of the present invention, AW
A plurality of signal wavelengths are dropped and inserted at one output terminal of G, and transmission / reception for each signal wavelength is performed within each terminal of the AWG.

That is, from the above viewpoint, the input wavelength-division multiplexed signal is demultiplexed for each wavelength, and F
Demultiplexing means having a periodic demultiplexing characteristic for outputting a plurality of optical signals having different wavelengths in a period of SR (Free Spectral Range);
An optical ADM circuit for extracting a signal to a receiving unit or inserting a signal from a transmitting unit for each wavelength with respect to a plurality of signals output from each output terminal of the demultiplexing unit;
In an optical ADM node including a multiplexing unit that multiplexes and outputs an output from a DM circuit, an FSR value of the demultiplexing unit is set to an integral multiple of a signal wavelength interval of an input wavelength multiplexed signal. Wherein each of the N optical ADM circuits comprises:
It is characterized in that at least two or more wavelength-selective two-input / two-output optical switches showing a switching operation only for an optical signal having a unique wavelength are connected in series, and each of the wavelength-selective two-input / two-output light An optical transmitter and an optical receiver are connected to the other input and output of the switch, respectively, and the switching operation wavelengths of the wavelength-selective 2-input 2-output optical switches in the optical ADM circuit are mutually different. Embodiments of the present invention disclose an optical ADM node characterized by matching different signal wavelengths.

[0010]

Embodiments of the present invention will be described below with reference to the drawings. FIG. 4 is a block diagram showing an embodiment of the present invention. However, for the sake of simplicity, the number of wavelength multiplexes is eight.
FIG. 4 is a diagram when the number of branch terminals of the optical multiplexer / demultiplexer is 4, and an optical ADM circuit that transmits and receives all branch signals of each branch terminal 10-j (j = 1, 2, 3, 4) for each signal wavelength AWG 10 for the structure of
Only one row of the branch terminal 10-1 is shown, and the description of the configuration of the other three-terminal ADM circuit is omitted. FIG. 5 shows the branching characteristics required for AWG 10 and AWG 14 used for the demultiplexing means and the multiplexing means. In the figure, equally spaced signal wavelengths are represented from the short wavelength side as λ1, λ2, λ3, λ4, λ5, λ6, λ7, λ8, and the FSR of the AWG is represented as Δλ. The AWG sets the FSR to an integral multiple of the signal wavelength interval, four times in this embodiment, and sets the branch wavelength interval equal to the signal wavelength interval. This allows AWG 10
And signal wavelengths λ1 and λ5 (= λ1 + Δλ) by AWG14
From terminal 1 and signal wavelengths λ2 and λ6 (= λ2 + Δλ)
From 2, the signal wavelengths λ 3 and λ 7 (= λ 3 + Δλ) are input from the terminal 3, and the signal wavelengths λ 4 and λ 8 (= λ 4 + Δλ) are input from the terminal 4 to the demultiplexed output or the multiplexed input.

[0011] Of the signal of wavelength λ1 and the signal of wavelength λ5, which are demultiplexed and output from the AWG 10 to the branch terminal 10-1, the wavelength-selective two-input two-output optical switch 11-1 operating at the wavelength λ1 has the wavelength λ5. The signal is output to an output terminal connected to the wavelength selective two-input two-output optical switch 11-2. The signal of the wavelength λ1 is output to an output terminal connected to the wavelength-selective optical switch 11-2 or an output terminal connected to the receiver 12-1 as necessary. The signal of wavelength λ1 that has entered the receiver 12-1 is received by the receiver 12-1, and a new signal of wavelength λ1 is simultaneously transmitted from the transmitter 13-1 to one input terminal of the optical switch 11-1. The signal is output from the output terminal of the optical switch 11-1 connected to the optical switch 11-2. The signal of wavelength λ1 and the signal of wavelength λ5 output from the optical switch 11-1 further enter the wavelength selective optical switch 11-2 operating at the wavelength λ5. Similarly to the operation of the optical switch 11-1, the signal of the wavelength λ1 is output to the output terminal connected to the AWG 14 by the optical switch 11-2,
The signal of wavelength λ5 is output to an output terminal connected to the AWG 14 or an output terminal connected to the receiver 12-2 as necessary. The signal of wavelength λ5 incident on the receiver 12-2 is received by the receiver 12-2, and at the same time, a new signal of wavelength λ5 is transmitted from the transmitter 13-2 to one input terminal of the optical switch 11-2. Output from the output terminal of the optical switch 11-2 connected to the AWG 14. The structure of the optical ADM circuit is the same for the remaining three branch terminals 10-2, 10-3, and 10-4 of the AWG 10,
In each optical ADM circuit, the processing of all the signals demultiplexed and output from the AWG 10 is performed. The output signal of the optical ADM circuit is again multiplexed with the signal of the other branch terminal by the AWG 14, and transmitted from the optical ADM node as an eight-wavelength multiplexed signal.

The order of the wavelength-selective optical switches 11-1 and 11-2 in the optical ADM circuit for transmitting and receiving a plurality of signals demultiplexed and output from the AWG to the respective branch terminals in the above-described embodiment is arbitrary. is there.

In the above embodiment, a 1 × N type AWG is used for each of the multiplexing means and the demultiplexing means. However, as in the second embodiment shown in FIG. 6, one N × N type AWG is used for both means. of
The present invention can be implemented using an AWG. Of the signal of wavelength λ1 and the signal of wavelength λ5 branched from AWG 19 to branch terminal 19-1, wavelength selective optical switch 20-1 operating at wavelength λ1
The signal of the wavelength λ5 is changed by the wavelength selective optical switch 20-2.
Is output to the output terminal connected to. The signal of wavelength λ1 is output to an output terminal connected to the wavelength-selective optical switch 20-2 or an output terminal connected to the receiver 21-1, as necessary. The signal of wavelength λ1 that has entered the receiver 21-1 is received by the receiver 21-1, and at the same time, a new signal of wavelength λ1 is transmitted from the transmitter 22-1 to one input terminal of the optical switch 20-1. Optical switch 20-1 connected to optical switch 20-2
Is output from the output terminal. The signal of the wavelength λ1 and the signal of the wavelength λ5 output from the optical switch 20-1 are further divided into the wavelength λ5
And enters the wavelength-selective optical switch 20-2 operating at. Similarly to the operation of the optical switch 20-1, the signal of the wavelength λ1 is output to the output terminal connected to the AWG 19 by the optical switch 20-2, and the signal of the wavelength λ5 is connected to the AWG 19 as necessary. The output terminal is connected to the output terminal or the output terminal connected to the receiver 21-2. The signal of wavelength λ5 incident on the receiver 21-2 is received by the receiver 21-2, and at the same time, a new signal of wavelength λ5 is transmitted from the transmitter 22-2 to one input terminal of the optical switch 20-2. Switch 20 connected to AWG 19
Output from -2 output terminal. The structure of the optical ADM circuit is A
The same applies to the remaining three branch terminals 19-2, 19-3, and 19-4 of the WG 19, and all optical ADM circuits process all the signals that have been demultiplexed and output from the AWG 19. The output signal of the optical ADM circuit is multiplexed again with the signal of the other branch terminal by the AWG 19, and transmitted from the optical ADM node as an 8-wavelength multiplexed signal.

In the above two embodiments, the number of branch terminals of the optical multiplexer / demultiplexer is reduced by half by setting the FSR to half of the wavelength multiplexed signal band.
By setting it to 3 or / 4, the number of branch terminals of the optical multiplexer / demultiplexer can be reduced to 3 or / 4, respectively.

As described above, in the optical multiplexer / demultiplexer in the optical ADM node for the N-wavelength multiplexed signal according to the present invention, the number of AWG branch terminals, which conventionally required only N, is set to N / N.
It can be reduced to 2 or less. As a result, the volume and cost of the optical ADM node can be reduced by the reduced number of terminals.

According to the embodiment of the present invention, the number of branch ports of the optical multiplexer / demultiplexer is reduced, the problem of the increase in the volume and cost of the optical ADM node accompanying the improvement of the multiplicity is improved, and the simple optical ADM is improved.
It is possible to provide a structure.

[0017]

According to the embodiment of the present invention, the configuration of the optical ADM node device can be simplified.

[Brief description of the drawings]

FIG. 1 is a diagram showing a configuration of a conventional optical ADM (Add / Drop Multiplexing) node.

FIG. 2 is a diagram illustrating a configuration of a conventional optical ADM node.

FIG. 3 is a diagram showing the relationship between the signal wavelength band of the conventional wavelength multiplex transmission and the wavelength dependence of the insertion loss of the optical multiplexer / demultiplexer.

FIG. 4 is a diagram illustrating a configuration of an optical ADM node according to the first embodiment of the present invention.

FIG. 5 is a diagram illustrating a relationship between a signal wavelength band of wavelength multiplex transmission and a wavelength dependence of an insertion loss of an optical multiplexer / demultiplexer according to an embodiment of the present invention.

FIG. 6 is a diagram illustrating a configuration of an optical ADM node according to a second embodiment of the present invention.

[Explanation of symbols]

1… 1 × 4 splitter 1-1… Branch terminal 1, 1-2… Branch terminal 2, 1-3… Branch terminal 3,1-
1… Branch terminal 4 2… Optical switch 3… 1 × 4 multiplexer 4… 5 × 5 array waveguide diffraction grating type multiplexer / demultiplexer (Arrayed Wav
eguide Grating: AWG) 4-1 ... Branch terminal 1, 4-2 ... Branch terminal 2, 4-3 ... Branch terminal 3, 4-
4… Branch terminal 4 5… Optical switch 6… AWG terminal 1 branch characteristic 7… AWG terminal 2 branch characteristic 8… AWG terminal 3 branch characteristic 9… AWG terminal 4 branch characteristic 10… 1 × 4 AWG 10-1… Branch terminal 1, 10-2… Branch terminal 2, 10-3… Branch terminal
3, 10-4 ... branch terminal 4 11-1 ... wavelength selective optical switch operating at wavelength λ1 12-1 ... receiver of signal of wavelength λ1 13-1 ... transmitter of signal of wavelength λ1 11-2 ... wavelength Wavelength-selective optical switch operating at λ5 12-2… Receiver of signal of wavelength λ5 13-2… Transmitter of signal of wavelength λ5 14… 1 × 4 AWG 15… Branch characteristics of AWG terminal 1 16… AWG Branch characteristic of terminal 2 17… Branch characteristic of AWG terminal 3 18… Branch characteristic of AWG terminal 4 19… 5 × 5 AWG 19-1… Branch terminal 1, 19-2… Branch terminal 2, 19-3… Branch Terminal
3, 19-4 ... branch terminal 4 20-1 ... wavelength-selective optical switch operating at wavelength λ1 21-1 ... receiver of signal of wavelength λ1 22-1 ... transmitter of signal of wavelength λ1 20-2 ... wavelength Wavelength-selective optical switch operating at λ5 21-2 ... Receiver of signal of wavelength λ5 22-2 ... Transmitter of signal of wavelength λ5 where Δλ is FSR (Free Spectral Range) and j is from 1 to the number of terminals When AWG terminal numbers are used, λj represents the shortest wavelength among the signal wavelengths multiplexed and demultiplexed at the branch terminal j.

Claims (5)

[Claims] An input wavelength multiplexed signal is demultiplexed for each wavelength.
FSR (Free Spectral Rang)
e) a demultiplexing unit having a function of outputting a plurality of optical signals having different wavelengths to the output terminal in the cycle of e), and transmitting the plurality of optical signals output from the output terminals to a receiving unit for each wavelength. An optical ADM circuit that extracts a signal or inserts a signal from a transmitting unit, and a multiplexing unit that multiplexes and outputs an output from each of the optical ADM circuits and outputs the multiplexed signal from one terminal of the output terminal And output the first and second optical signals having different wavelengths from each other to a first optical ADM node having a first wavelength selection characteristic, so that the first optical signal can be branched. Together with a third optical signal having the same wavelength characteristic as the first optical signal.
The second optical ADM node means can input the output optical signal of the first optical ADM node means into the second optical ADM node means, and the second optical signal can be dropped.
A fourth optical signal having the same wavelength characteristic as that of the second optical ADM node can be inserted from the second optical ADM node means.
An optical ADM node device configured to input an output signal from a DM node unit to the multiplexing unit. 2. The demultiplexing means and the multiplexing means have an identical branching characteristic.
2. The optical ADM node device according to claim 1, wherein the optical ADM node device is configured by dwaveguide grating (AWG). 3. The optical ADM node means has a wavelength-selective two-input two-output optical switch that performs a switching operation only for an optical signal of a specific wavelength, and the optical switch has an acousto-optic filter (AOTF). 3. The optical ADM node device according to claim 1, wherein: 4. The demultiplexing means and the multiplexing means,
The optical ADM node device according to any one of claims 1 to 3, wherein the optical ADM node device has a structure in which a transmission / reception unit is connected between input / output terminals for each wavelength using one NxN optical multiplexer / demultiplexer. . 5. The optical ADM node device according to claim 1, wherein an FSR value of said demultiplexing means is set to an integral multiple of a signal wavelength interval of an input wavelength multiplex signal. .