JPH07270640A - Optical branching and inserting circuit - Google Patents

Abstract

PURPOSE:To provide an optical branching and inserting circuit which makes switching of wavelengths for branching and inserting easy, enables branching, inserting and switching of signals among plural numbers of wavelength multiplexed light, and further can be used even for multiwavelength light of a high density. CONSTITUTION:This circuit has a wavelength-divided multiplexer/demultiplexer 11, optical multiplexer/demultiplexer 41 having the same structure as the multiplexer/demultiplexer 11, and 2X2 optical switches 51b-51f inserted into the loop back circuits of two lines corresponding to the respective multiplexer/ demultiplexer 11, 41 to switch the lines between these. The multiplexer/ demultiplexer 11 consists of input and output waveguides 13a-13f and 17a-17f, in which, except for a pair of input and output waveguides 13a, 17a for external connection, input and output ports 13b-13f, 17b-17f are connected with loop back optical paths 18b-18f.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an optical wavelength division multiplexing transmission system in which one or a plurality of optical signals are branched and extracted from a plurality of wavelength-multiplexed optical signals, and a wavelength equal to the wavelength of the extracted optical signals. The present invention relates to an optical add / drop circuit for newly inserting and multiplexing the optical signal of.

[0002]

2. Description of the Related Art Conventionally, an optical add / drop circuit for adding / dropping a wavelength-multiplexed optical signal in an optical wavelength division multiplexing transmission system has been known. The optical add / drop circuit is roughly divided into a circuit configured by using a demultiplexer and a multiplexer, and a circuit configured by using an acousto-optic filter. The outline of each conventional example will be described below.

First, a conventional optical add / drop circuit constructed using a demultiplexer and a multiplexer will be described. FIG. 16 is a block diagram for explaining the principle of this kind of optical add / drop circuit 3. In the figure, 1 and 2 are optical fiber transmission lines, and it is assumed that n-wave signal lights having wavelengths of λ1, λ2, ..., λn are wavelength-multiplexed and transmitted. In the optical add / drop circuit 3, the incoming multiplexed optical signal is separated into n signal lights having different wavelengths by the demultiplexer 4, and the necessary signal lights λi and λj are extracted to the outside. The remaining signal light propagates in the optical fibers 6a, 6b, ..., 6n, and these signal lights are combined by the multiplexer 5 with the signal lights of wavelengths λi and λj to be inserted from the outside to obtain the wavelength λ1, λ2
, .Lambda.n are output as multiplexed optical signals.

By the way, Y. Y. Tachikawa et al. Have reported an optical add / drop circuit that realizes the demultiplexing operation and the multiplexing operation by the above-mentioned principle by a single optical multiplexer / demultiplexer. FIG. 17 is a block diagram showing the configuration of the optical add / drop circuit. For details of this circuit, see Y. References by Tachikawa et al. (Y. Tachikawa et al., Electronics Lette
rs, vol.29, no.24, 25th November 1993, pp.2133-213
4). 17, in the optical add / drop circuit, an arrayed waveguide diffraction grating type optical multiplexer / demultiplexer 11 is provided between the optical fiber transmission lines 1 and 2, and each of the output waveguides 17 and the input waveguides 13 is provided between them. , An optical fiber (loopback optical path) for inputting the signal light output from the output waveguide 17 to the input waveguide 13 corresponding to the output waveguide 17
18 is provided and configured.

Generally, the number of input waveguides and output waveguides of the arrayed waveguide diffraction grating type optical multiplexer / demultiplexer 11 is arbitrary.
Here, for the sake of simplicity, the number of the optical fiber transmission lines 1 is six, and the optical fiber transmission line 1 is connected to the input waveguide 13a which is one of the six input waveguides 13a, 13b, ... Is the six output waveguides 17a, 17
, 17f, which is one of the output waveguides 17a.

In such a configuration, the wavelengths λ2 and λ
The wavelength-multiplexed optical signal of 5 waves of 3, ..., λ6 (the optical signal of wavelength λ1 will be described later) propagates through the optical fiber transmission line 1 and then is input to the array waveguide diffraction grating type optical multiplexer / demultiplexer 11. It is input to the waveguide 13a. In the slab waveguide 14,
This wavelength-multiplexed optical signal spreads due to diffraction and is input to a plurality of waveguides forming the arrayed waveguide diffraction grating 16.

These signal lights are condensed by the slab waveguide 15 after propagating through the arrayed waveguide diffraction grating 16. However, due to the phase difference generated while propagating through the arrayed waveguide diffraction grating 16, a converged light is generated. The convergence position will differ depending on the wavelength. By performing an appropriate design, for example, the wavelength λ1 is output from the output waveguide 17a, the wavelength λ2 is output from the output waveguide 17b, ..., The wavelength λ6 is output from the output waveguide 17f, and so on. j (j = a,
b, ..., F). That is, they are demultiplexed according to the wavelength multiplexing / demultiplexing characteristic shown in FIG.

In the conventional circuit shown in FIG. 17, the signal lights of the wavelengths to be branched, for example, the wavelengths λ3 and λ4 are taken out as they are. On the other hand, each of the remaining signal lights propagates in the corresponding optical fiber 18b, 18e, 18f, and is returned to the arrayed waveguide diffraction grating type optical multiplexer / demultiplexer 11 together with the signal lights of wavelengths λ3 and λ4 inserted from the outside. Be done.

The signal light returned to the input waveguide 13 is combined with the output waveguide by the same action as that of the first time. What is important here is that the j-th optical fiber 18j is connected to the j-th input waveguide 13j. As shown in FIG. 18, the wavelength λj input from the input waveguide 13j
The signal light of is output from the output waveguide 17a. That is, signal lights of all wavelengths λ2, ..., λ5, λ6 are sent out from the output waveguide 17a to the optical fiber transmission line 2.

However, when the wavelength-division-multiplexed signal light contains the signal light of wavelength λ1, only this signal light does not pass through the optical fiber 18, and the input waveguide 13a and the arrayed-waveguide diffraction grating 1
6, and output to the optical fiber transmission line 2 via each of the output waveguides 17a. Therefore, only the signal light of wavelength λ1 cannot be added / dropped in this circuit.

Next, an example of the configuration of a conventional optical add / drop circuit using a waveguide type acousto-optic filter will be described with reference to FIG. For details of this conventional example,
D. A. References by Smith et al. (DA Smith et al., IEEE Jour
nal on Selected Areas in Communications, vol.8, no.
6, August 1990, pp.1151-1159). In FIG. 19, the optical add / drop multiplexer 31 is composed of polarization splitters 32 and 35, a LiNbO ₃ waveguide 34, a transducer 33, and an oscillator 37.

In this circuit, a multiplexed optical signal having wavelengths λ1, λ2, ..., λn in the optical fiber transmission line 1 is separated into a TE wave and a TM wave by a polarization splitter 32, and the respective wavelength-multiplexed waveguides 34a. , 34b. Here, the transducer 33 excites the acoustic elastic wave 36 of the frequency fi on the waveguides 34a and 34b. Waveguide 34a,
In 34b, acoustic elastic waves 36
The photoelastic effect effectively acts only on the signal light having the wavelength λi corresponding to the vibration frequency fi, and mode conversion occurs. That is, the TE wave is converted into the TM wave and the TM wave is converted into the TE wave. Therefore, as a result of being multiplexed by the polarization splitter 35, only the signal light of the wavelength λi that has been mode-converted in the waveguides 34a and 34b is output to the optical fiber transmission line 6, and the signal light of the remaining wavelengths is transmitted by the optical fiber transmission. It is output to the path 2.

Since the optical add / drop circuit 31 of FIG. 19 has symmetry, it operates similarly even if the optical fiber transmission lines 1 and 5 and the optical fiber transmission lines 2 and 6 are interchanged.
Therefore, when the signal light of wavelength λi is added to the optical fiber transmission line 5, this signal light is multiplexed with the signal light of another wavelength added from the optical fiber transmission line 1 and output to the optical fiber transmission line 2. It

Here, if the frequency applied to the transducer 33 is changed, the light of the signal light output to the optical fiber transmission line 6 can be switched. Further, by adding a plurality of frequencies to the transducer 33, it is possible to simultaneously branch and output lights having a plurality of wavelengths into the optical fiber transmission line 6.

That is, the conventional circuit shown in FIG.
It realizes various functions as shown in FIG. In FIG. 20, wavelengths λ1, λ2, which propagate through the optical fiber transmission line 1,
The optical signals of λn are denoted by reference symbols s11, s12 ,.
, s1n, while the optical signals of wavelengths λ1, λ2, ..., λn propagating in the optical fiber transmission line 5 are denoted by reference numeral s2.
, S22, ..., S2n. In either case, the wavelength to be added / dropped is selected according to the input of the selection signal 9.

In FIG. 20, (a), (b), (c)
Shows a function of adding / dropping an optical signal of an arbitrary one wavelength, a function of adding / dropping an optical signal of an arbitrary plurality of wavelengths at the same time, and a function of exchanging optical signals of an arbitrary one or a plurality of wavelengths. The functions shown in FIG. 20 are indispensable for constructing a network using the wavelength division multiplexing transmission system and operating it flexibly. The reason is that it is necessary to dynamically switch the value and the number of wavelengths to be added / dropped according to the fluctuation of traffic.

[0017]

By the way, in the conventional optical add / drop circuit (array waveguide diffraction grating type optical multiplexer / demultiplexer with loopback optical path) described with reference to FIG. 17, the wavelength of the signal light to be added / dropped is increased. The output waveguide that outputs the branched optical signal and the input waveguide that inputs the inserted optical signal differ depending on the. Therefore, it is necessary to change the connection between the branch output and the add output each time when changing the wavelength at which the add / drop is performed, which causes a problem that it takes a lot of time and effort. Also,
There has been a fatal defect that the add / drop or replacement of a plurality of multiplexed signal lights as shown in FIGS. 20 (b) and 20 (c), which is indispensable for constructing an actual network, cannot be realized.

Further, in another conventional optical add / drop circuit (optical add / drop circuit using a waveguide-type acousto-optic filter) described with reference to FIG. 19, a wavelength range of light that interacts with an elastic wave of frequency fi. Since it is as wide as about 1 nm or more, the wavelength multiplexing interval can be narrowed to about 1 nm at most, and there is a drawback that it is extremely difficult to increase the multiplexing degree.

Further, there is a spurious wavelength region called a side lobe as shown in FIG. 21 in the wavelength branching characteristic when an elastic wave of frequency fi is added, and therefore, some optical signals of wavelengths that should not be branched actually. There was also the problem of leaking (causing crosstalk). This phenomenon is
The problem that the beat noise (coherent crosstalk) of the frequency fi is generated when the output light is demodulated due to a synergistic effect with another phenomenon that the frequency of the light acting on the elastic wave is shifted by fi (acoustic shift). Also had.

The present invention has been made in view of the above circumstances, and it is easy to switch the wavelengths to be added / dropped, and it is possible to add / drop the signal light between a plurality of wavelength multiplexed lights. Moreover, it is an object of the present invention to provide an optical add / drop circuit that can be used for high-density wavelength-division multiplexed light.

[0021]

In order to solve the above-mentioned problems, the optical add / drop circuit according to claim 1 has n (n is a natural number of 2 or more) optical paths through which each wavelength-multiplexed optical signal propagates. An optical add / drop circuit for adding / dropping an optical signal of a predetermined wavelength between, each having a plurality of pairs of input / output ports,
Corresponding to n wavelength division multiplexing optical demultiplexers, which are formed by loop-connecting other pairs of input / output ports except for one pair of input / output ports for external connection by loopback optical paths. It is characterized by comprising an n × n matrix switch which is inserted in the n loopback optical paths and which switches the paths between these optical paths.

The optical add / drop circuit according to claim 2 is
An optical add / drop circuit that adds / drops an optical signal of a predetermined wavelength between n (n is a natural number of 2 or more) optical paths through which each wavelength-multiplexed optical signal propagates, and has a plurality of pairs of input / output ports. A wavelength division multiplex optical multiplexer / demultiplexer formed by loop-connecting other pairs of input / output ports excluding n pairs of input / output ports for external connection by a loopback optical path, and a loopback optical path of the optical multiplexer / demultiplexer And an n × n matrix switch for switching the path between n loopback optical paths.

Further, the optical add / drop multiplexer according to claim 3 is
An optical add / drop circuit that adds / drops an optical signal of a predetermined wavelength between n (n is a natural number of 2 or more) optical paths through which each wavelength-multiplexed optical signal propagates, and has a plurality of pairs of input / output ports. , A wavelength division multiplexing optical multiplexer / demultiplexer in which other pairs of input / output ports for external connection are loop-connected by a loopback optical path, and each loopback of the optical multiplexer / demultiplexer A demultiplexer and a multiplexer that are inserted in the optical path and branch each optical path for a predetermined section for each wavelength, and n branch-back optical paths that are inserted in the branch optical path between the demultiplexer and the multiplexer. And an n × n matrix switch for switching the path between them.

The optical add / drop multiplexer according to claim 4 is
The optical add / drop circuit according to any one of claims 1 to 3, wherein, in place of the nxn matrix switch, a 2x2 switch is provided for every two loopback optical paths to be added / dropped. It has a feature.

An optical add / drop multiplexer according to a fifth aspect of the present invention is
An optical add / drop circuit that drops / adds an optical signal of a predetermined wavelength between two optical paths in which wavelength-multiplexed optical signals propagate in opposite directions, each having a plurality of input / output ports on two sides, Except for two pairs of input / output ports for external connection,
One wavelength division multiplex optical multiplexer / demultiplexer formed by loop-connecting a pair of input / output ports on the same side surface and a loopback optical path paired between different side surfaces of the optical multiplexer / demultiplexer. It is characterized in that it is provided with a 2 × 2 switch which is inserted and switches the path between these two optical paths.

An optical add / drop circuit according to a sixth aspect of the present invention is
An optical add / drop circuit that drops / adds an optical signal of a predetermined wavelength between two optical paths through which each wavelength-multiplexed optical signal propagates. The optical add / drop circuit has a plurality of pairs of input / output ports and is provided for external connection.
One wavelength division multiplexing optical multiplexer / demultiplexer in which other pairs of input / output ports except the paired input / output ports are loop-connected by a loopback optical path, and the two external optical paths and the optical multiplexer / demultiplexer are externally connected. First and second three-terminal optical circulators respectively connecting the input and output ports, and the transmission and reflection of the optical signal which is inserted in each loopback optical path of the optical multiplexer / demultiplexer and propagates in each optical path. It is characterized by comprising a transmission / reflection switching switch for switching between.

[0027]

According to the optical add / drop multiplexer of the first aspect, the wavelength-multiplexed optical signals propagating in the respective optical paths are input to the corresponding optical multiplexers / demultiplexers, and the respective optical multiplexers / demultiplexers demultiplex the respective wavelengths. After being waved, it propagates in the corresponding loopback optical path. Then, the optical signal of the predetermined wavelength to be added / dropped is switched between the corresponding loopback optical paths of each optical multiplexer / demultiplexer by the switching operation of the n × n matrix switch. Then, each loopback optical path optical signal that has completed the add / drop operation is input again to each optical multiplexer / demultiplexer, recombined, and then output from each external output port. In this way, the optical multiplexers / demultiplexers add and drop each other between the loopback optical paths for each wavelength. As a result, it is possible to add / drop a plurality of signal lights between a plurality of wavelength-multiplexed lights and to replace each of the signal lights independently for each wavelength only by switching the switches.

According to the optical add / drop multiplexer of the second aspect, a single optical multiplexer / demultiplexer is regarded as n optical multiplexers / demultiplexers, and n × is provided between corresponding n loopback optical paths. By the switching operation of the n-matrix switch, an optical signal of a predetermined wavelength is added / dropped. As a result, the same operation as that of the optical add / drop multiplexer according to claim 1 can be obtained with only a single optical multiplexer / demultiplexer, and there is no need to adjust the wavelength characteristics among a plurality of optical multiplexer / demultiplexers. The yield can be improved and the stability can be improved.

Further, according to the optical add / drop multiplexer of the third aspect, the multiplexed light is further separated for each wavelength in the loopback optical path, so that the wavelength multiplexing degree of the optical multiplexer / demultiplexer itself is not increased. The same operation as that of the optical add / drop circuit according to item 2 can be obtained.

Further, according to the optical add / drop circuit according to claim 4, in the operation of the optical add / drop circuit according to any one of claims 1 to 3, particularly, the switching operation of the 2 × 2 switch causes
Drop and add is performed between the loopback optical paths of the book.

According to the optical add / drop circuit of the fifth aspect, as in the optical add / drop circuit of the second aspect, a single optical multiplexer / demultiplexer is equivalently plural (two in this case). The optical signal passes through the optical multiplexer / demultiplexer in both directions. That is, a single optical multiplexer / demultiplexer has two wavelength divisions, two wavelength division multiplexers have equal wavelength division multiplexers, and two optical multiplexers / demultiplexers in which optical signals of the two propagate in opposite directions in the respective optical multiplexers / demultiplexers. Function as a container. As a result, claim 1 or 2
Similar to the optical add / drop circuit described above, add / drop or replacement of a plurality of signal lights between a plurality of wavelength-multiplexed lights can be realized independently for each wavelength only by switch switching. In addition to this, when the single optical multiplexer / demultiplexer functions as two optical multiplexers / demultiplexers, since the respective optical signals propagate in the optical multiplexer / demultiplexer in opposite directions, In addition, even if optical signals with different wavelengths are mixed, these optical signals do not mix into the optical path on the output side as they are, but pass through the optical multiplexer / demultiplexer and then return to the optical path on the input side in the reverse direction. Is output as light propagating to. As a result, if an optical isolator is inserted in the optical path on the input side, it can be easily removed. This is a great advantage when an optical fiber amplifier that generates spontaneous emission noise is used in the optical path on the input side.

According to the optical add / drop multiplexer of the sixth aspect, since the three-terminal optical circulator is connected to the external input / output portion of the optical multiplexer / demultiplexer, one input portion of the optical multiplexer / demultiplexer is connected in the opposite direction. It can be used as an output unit. Therefore, a single optical multiplexer / demultiplexer can function as two optical multiplexer / demultiplexers multiplexed in the propagation direction of the optical signal. At this time,
Since the pair of lights propagating in the opposite direction in one loopback optical path substantially constitute the loopback optical path pair, either the transmission or the reflection is switched by the transmission / reflection changeover switch inserted in the loopback optical path. The loopback optical paths can be interchanged by selection. As a result, with a single optical multiplexer / demultiplexer, it is possible to add / drop a plurality of signal lights among a plurality of wavelength-multiplexed lights and replace each signal independently for each wavelength only by switching.

[0033]

Embodiments of the present invention will be described below with reference to the drawings. A: First Embodiment FIG. 1 is a block diagram showing the configuration of the optical add / drop multiplexer according to the first embodiment of the present invention. In this optical add / drop circuit, an arrayed waveguide diffraction grating type optical multiplexer / demultiplexer 11 is provided between the optical fiber transmission lines 1 and 2, and each of the output waveguides 17 and the input waveguides 13 is provided between them. , The output waveguide 1
An optical fiber (loopback optical path) 18 for inputting the signal light output from the optical waveguide 7 to the input waveguide 13 corresponding to the output waveguide 17 is provided, and the conventional optical add / drop circuit described with reference to FIG. It is configured.

Similarly, an arrayed waveguide diffraction grating type optical multiplexer / demultiplexer 41 is provided between the optical fiber transmission lines 5 and 6 for add / drop, and between each output waveguide 47 and the input waveguide 43. An optical fiber (loopback optical path) 48 for inputting the signal light output from the output waveguide 47 to the input waveguide 43 corresponding to the output waveguide 47 is provided, and a conventional optical add / drop circuit is configured. There is.

Here, the optical fiber transmission line 1 is connected to the input waveguide 13a, which is one of the six input waveguides 13a to 13f, and similarly, the optical fiber transmission line 2 is connected to the output waveguide 17a. ing. The optical fiber transmission line 5 is connected to the input waveguide 43a, and the optical fiber transmission line 6 is connected to the output waveguide 47a. further,
Two arrayed waveguide diffraction grating type optical multiplexers / demultiplexers 11, 41
Represent almost equal wavelength multiplexing / demultiplexing characteristics.

Optical fiber (loopback optical path)
A pair of optical fibers corresponding to 18 and an optical fiber (loopback optical path) 48, that is, 18b and 48b, 18c and 4
The optical fiber pair (loopback optical path pair) of 8c, ..., 18f and 48f has 2 × 2 optical switches 51b, 51c,
..., 51f are connected.

Here, the 2 × 2 optical switch 51 may be constructed, for example, as shown in FIG. The optical switch shown in FIG. 2 forms a two-beam interference system (Mach-Zehnder interference system) by forming 3 dB couplers 514 and 515 by a quartz waveguide on a quartz waveguide substrate 512. Here, an electric current is passed through the heater 513 to change the temperature of a specific portion of the waveguide, and the change in the refractive index due to the temperature change causes 2 ×.
The optical switch operation of 2 is realized. That is, at a certain current value I1, the optical signals propagating through the optical fibers 516 and 517 are output to the optical fibers 518 and 519 (bar state), and at another certain current value I2, they are output to the optical fibers 519 and 518, respectively. (Crossed state).

Next, the operation of the optical add / drop multiplexer circuit shown in FIG. 1 will be described. Signal lights s12, s13, having wavelengths λ2, λ3, ..., λ6, which have propagated through the optical fiber transmission line 1.
, S16 is an arrayed waveguide grating type optical multiplexer / demultiplexer 11
Via the optical fiber 18b, 18c, respectively, according to the wavelength multiplexing / demultiplexing characteristics shown in FIG.
..., propagates through 18f. Similarly, the optical fiber transmission line 5
Signal light s having wavelengths λ2, λ3, ..., λ6 propagating through the inside
, S26 are demultiplexed via the arrayed waveguide diffraction grating type optical multiplexer / demultiplexer 41 and propagated in the optical fibers 48b, 48c ,. Therefore, the optical signals of wavelengths λ2, λ3, ..., λ6 are input to the optical switches 51b, 51c, ..., 51f, respectively.

Here, the optical switch 51i (i = b, c,
, F) is in the bar state, the output waveguide 17i (i = b, c, ..., Of the arrayed waveguide grating type optical multiplexer / demultiplexer 11)
f) output optical signal s1i (i = 2, 3, ...,
6) is inputted to the input waveguides 13i (i = b, c, ..., F) of the same arrayed-waveguide diffraction grating type optical multiplexer / demultiplexer 11, and similarly from the arrayed-waveguide diffraction grating type optical multiplexer / demultiplexer 41. Outputs s2i (i = 2, 3, ..., 6) are input waveguides 43i (i = b, of the same arrayed waveguide diffraction grating type optical multiplexer / demultiplexer 41).
c, ..., F). Therefore, similarly to the conventional circuit described with reference to FIG. 17, the optical signal s1i is output to the optical fiber transmission line 2 and the optical signal s2i is output to the optical fiber transmission line 6.

However, the optical switch 51j (i = b,
When c, ..., F) are in the cross state, the output s1j (j = 2, 3, ..., Of the arrayed waveguide diffraction grating type optical multiplexer / demultiplexer 11).
6) is input to the input waveguide 43j (j = b, c, ..., f) of the other arrayed waveguide diffraction grating type optical multiplexer / demultiplexer 41,
Output s2j of array waveguide diffraction grating type optical multiplexer / demultiplexer 41
(J = 2, 3, ..., 6) is an input waveguide 13j (j = b, c, ..., f) of the arrayed waveguide grating type optical multiplexer / demultiplexer 11.
Entered in. Therefore, the optical signal s1j is output to the optical fiber transmission line 6 and the optical signal s2j is output to the optical fiber transmission line 2. That is, the wavelength λj (j = 2,
Addition / dropping is performed on the signal lights of 3, ..., 6).

For example, when the 2 × 2 optical switches 51b, 51e and 51f are in the bar state and the 2 × 2 optical switches 51c and 51d are in the cross state as shown in FIG.
Add / drop is performed on the optical signals of 3 and λ4. That is, of the signal lights wavelength-multiplexed in the optical fiber transmission line 1, the signal lights a13 and s14 of the wavelengths λ3 and λ4 are branched and output to the optical fiber transmission line 6, and the remaining s12 and s.
15 and s16 are directly output to the optical fiber transmission line 2. On the other hand, at this time, the wavelength λ in the optical fiber transmission line 5
If the signal lights s23 and s24 of 3 and λ4 have propagated, they are inserted into the optical fiber transmission line 2. Further, at this time, the optical signals s22 and s2 of other wavelengths are introduced into the optical fiber transmission line 5.
If there are 5 and s26, these are output without being inserted into the optical fiber transmission line 6. That is, the function shown in FIG. 20C can be realized. Optical fiber transmission lines 1 and 5
The optical signals s11 and s12 of the wavelength λ1 are
It is output to the optical fiber transmission lines 2 and 6 as it is without passing through 8 and 48 and the optical switch 51.

As described above, in the optical add / drop multiplexer according to the present embodiment, the optical switch for switching the corresponding optical path pair is provided between the loopback optical paths of the plurality of arrayed waveguide diffraction grating type optical multiplexer / demultiplexers with loopback optical paths. With the skillful configuration, each multiplexer / demultiplexer can use the other party for recombining the branch output and pre-demultiplexing the insertion input,
The wavelength of the optical signal inserted from the single insertion input (optical fiber transmission line 5) and the wavelength of the optical signal branched to the single branch output (optical fiber transmission line 6) correspond to the 2 × 2 optical switch. Only by a simple operation of switching the crossbar state of 51, it is possible to arbitrarily and simultaneously select a plurality.

The optical add / drop multiplexer according to this embodiment is based on an arrayed waveguide diffraction grating type optical multiplexer / demultiplexer.
Unlike the conventional circuit using the acousto-optic filter described with reference to FIG. 9, the transmission width of the selected wavelength is, for example, 0.05
It is also possible to narrow it down to about nm. Since there is no frequency shift to the optical signal that is added / dropped, there is no problem of coherent crosstalk. Therefore, it is possible to significantly improve the wavelength multiplicity as compared with the conventional circuit using the acousto-optic filter. Further, for example, in FIG.
The use of the optical switch having such a configuration also has an advantage that the add / drop switching can be driven with less electric power than the acousto-optic filter. It should be noted that although an arrayed waveguide diffraction grating type optical multiplexer / demultiplexer is used in the present embodiment and other embodiments to be described below, the present invention is not limited to this, and FIG.
Any wavelength division multiplexing optical multiplexer / demultiplexer that exhibits the wavelength multiplexing / demultiplexing characteristics as shown in FIG. For example, a wavelength division multiplexing optical multiplexer / demultiplexer may be configured by multiplexing the input and output with a fiber array or the like in a configuration such as a spectrometer using a diffraction grating.

In the present embodiment and the embodiments described below, optical switches are provided for all loopback optical path pairs, but if there is a wavelength that does not need to be added / dropped, the corresponding optical switch is omitted. May be. Furthermore, when there is a wavelength that requires only branching or insertion, 1x2 or 2x1 is used instead of the 2x2 optical switch.
The optical switch may be used. If there is a wavelength that does not need to be output, the corresponding loopback optical path itself need not be configured.

Further, in the present embodiment, the number of wavelength multiplexing (the number of input / output waveguides) of the arrayed waveguide diffraction grating type optical multiplexer / demultiplexer 11 is set to 6 for simplification, but the present invention is not limited to this. Instead, for example, the number of multiplexing can be increased by increasing the number of loopback optical paths using an arrayed waveguide grating type optical multiplexer / demultiplexer with a wavelength multiplexing number of 16 which has already been reported.

Although the optical switch having the structure shown in FIG. 2 is used in this embodiment, the present invention is not limited to this, and an optical switch such as an optical switch formed on a LiNbO ₃ substrate may be used. A switch using the electro-optical effect may be used, and in this case, it is possible to switch the add / drop optical signal at high speed (for example, 1 nanosecond or less).

Further, in this embodiment, of the plurality of input waveguides and output waveguides, the endmost waveguides (13a, 17a) are provided.
Although a) is connected to the optical fiber transmission line, the present invention is not limited to this, and no matter which input / output waveguide is connected to the optical fiber transmission line, by appropriately selecting the loopback optical path, An equivalent optical add / drop circuit can be configured.

Further, although two arrayed waveguide grating type optical multiplexers / demultiplexers are used in the present embodiment, the present invention is not limited to this, and three or more multiplexers / demultiplexers are used. Then, the optical signal of the specific wavelength group λj is added / dropped between the first and second multiplexers / demultiplexers, and the optical signal of another wavelength group λk is transmitted between the first and third multiplexers / demultiplexers. It can also be configured to perform a drop-and-insert operation. In this case, the loopback optical path through which the wavelength group λj propagates is provided with a loopback optical path pair between the first and second optical multiplexers / demultiplexers to include an optical switch, while the loopback optical path through which the wavelength group λk propagates is the first. A loopback optical path pair may be provided between the third multiplexer / demultiplexer and an optical switch may be provided.

For example, FIG. 3 shows an example of such a configuration. In FIG. 3, the first and second optical multiplexers / demultiplexers 11, 4
In addition to 1, the third optical multiplexer / demultiplexer 91 is provided. The optical signals of wavelengths λ3 and λ6 (first wavelength group) are 2 × 2
By switching the optical switches 51c and 51f, the add / drop operation is performed between the first and second optical multiplexers / demultiplexers 11 and 41. Further, the optical signal of wavelength λ4 (second wavelength group) is switched by the 2 × 2 optical switch 51d,
The add / drop operation is performed between the first and third optical multiplexers / demultiplexers 11, 91. Further, the optical signals of the wavelengths λ2 and λ5 (third wavelength group) are switched by the 2 × 2 optical switches 51b and 51e, so that the second and third optical multiplexer / demultiplexers 4 are connected.
The add / drop operation is performed between 1 and 91.

Further, in the circuit using three or more optical multiplexers / demultiplexers described with reference to FIG. 3, the 2 × 2 optical switch 51 for switching the paths between the two loopback optical paths is used. However, the present invention is not limited to this, and may be configured by using an optical switch that switches paths among three or more loopback optical paths. An example of such a configuration is shown in FIG.

In the circuit shown in FIG. 4, instead of the 2 × 2 optical switches 51b to 51f shown in FIG. 3, the 3 × 3 optical switches 99b to 99b to switch the paths among the three optical paths.
It is equipped with 99f. This 3 × 3 optical switch 99b-9
By appropriately switching the loopback paths of the optical signals of wavelengths λ2 to λ6 by 9f, in the circuit shown in FIG. 4, the wavelengths λ2 to λ2 input from the three optical fiber transmission lines 1, 5 and 7, respectively. A 3-input 3-output signal switching operation is realized in which the optical signal of λ6 is appropriately sorted into the three optical fiber transmission lines 2, 6 and 8 for each wavelength.

Further, since the multiplexing / demultiplexing characteristic of the arrayed waveguide diffraction grating type optical multiplexer / demultiplexer generally has periodicity, for example, FIG.
In the multiplexer / demultiplexer having the characteristics shown in FIG. 8, the signal light of wavelength λj + 6 propagates along the same path as the signal light of wavelength λj (j = 1, 2, ..., 6). Therefore, by utilizing this periodicity, it is possible to simultaneously add / drop a plurality of signal lights (for example, wavelengths λ2 and λ8) by a single optical switch operation in this embodiment. Further, in the present embodiment and the following embodiments, the loopback optical path is composed of an optical fiber, but it may be composed of a waveguide, for example, an optical switch such as the waveguide shown in FIG. All of the components shown in FIG. 1 can be integrated on a single waveguide substrate by using the structure shown in FIG.

B: Second Embodiment FIG. 5 is a block diagram showing the structure of an optical add / drop multiplexer according to the second embodiment of the present invention. The circuit shown in this figure is
The point different from the circuit described in detail is that instead of using two arrayed waveguide diffraction grating type optical multiplexers / demultiplexers, a single arrayed waveguide diffraction grating type optical multiplexer / demultiplexer is used, 2 array waveguide diffraction grating type optical multiplexer / demultiplexer.

This optical add / drop circuit includes an arrayed waveguide diffraction grating type optical multiplexer / demultiplexer 61 having a wavelength multiplexing number of 12 between the input optical fiber transmission lines 1 and 5 and the output optical fiber transmission lines 2 and 6. An optical fiber for inputting the signal light output from the output waveguide 67 to the input waveguide 63 corresponding to the output waveguide 67 is provided between each output waveguide 67 and the input waveguide 63. A (loopback optical path) 68 is provided.

Here, the number of the optical fiber transmission lines 1 and 5 is 1.
Input waveguide 63 of the two input waveguides 63a to 63l
b and 63a, respectively, and the optical fiber transmission lines 2 and 6 are similarly connected to the output waveguides 67b and 67a. Then, a plurality of optical fibers (loopback optical path) 6
Of the eight, 68c and 68d, 68e and 68f, ..., 68
2 × 2 optical switches 52, 53, ..., 56 are connected to the optical fiber pair (loopback optical path pair) of k and 68l.

Next, the operation of the optical add / drop circuit shown in FIG. 5 will be described. Signal light s1 of wavelengths λ4, λ6, λ8, λ10, λ12 propagated through the optical fiber transmission line 1.
4, s16, s18, s110, and s112 are demultiplexed according to the relationship shown in FIG. 6 when passing through the arrayed waveguide diffraction grating type optical multiplexer / demultiplexer 61, and the optical fibers 68c,
Propagate through 68e, 68g, 68i and 68k. Similarly, the wavelengths λ4 and λ propagated through the optical fiber transmission line 5
6, λ8, λ10, λ12 signal lights s24, s26, s
28, s210, and s212 are optical fibers 68, respectively.
It propagates through d, 68f, 68h, 68j, and 68l.

This is the case where the arrayed waveguide diffraction grating type optical multiplexer / demultiplexer 61 having a wavelength division number of 12 is connected to the input waveguide 63m (m =
a, c, ..., I, k) and the output waveguide 67p (p = b,
d, ..., J, l) first optical multiplexer / demultiplexer (wavelength multiplex number 6), and second optical multiplexer / demultiplexer (input wavelength 63p and output waveguide 67m) (wavelength multiplex number 6) It is easy to understand if you consider it as two. From the relationship shown in FIG. 6, the characteristics of the first and second optical multiplexers / demultiplexers are shown in FIG.
It becomes like (b). That is, the single arrayed waveguide diffraction grating type optical multiplexer / demultiplexer 61 constitutes two optical multiplexers / demultiplexers having a double wavelength interval and equal wavelength multiplexing / demultiplexing characteristics.

Therefore, with the configuration of FIG. 5, the same operation as that of the first embodiment described with reference to FIG. 1 can be realized. The optical switches 52, 53, 54, 55, 56 include
Since the signal lights of the wavelengths λ4, λ6, λ8, λ10, and λ12 are input, the 2 × 2 optical switches 52, 55, and 56 are in the bar state, as shown in FIG.
When 3 and 54 are in the cross state, add / drop is performed on the optical signals of wavelengths λ6 and λ8. That is, of the signal lights wavelength-multiplexed in the optical fiber transmission line 1, the wavelength λ
Signal lights s16 and s18 of 6 and λ8 are branched and output to the optical fiber transmission line 6, and the remaining s14, s110, and s
112 is output to the optical fiber transmission line 2 as it is.
On the other hand, at this time, wavelengths λ6 and λ8 are introduced into the optical fiber transmission line 5.
If the signal lights s26 and s28 of No. 1 are propagated, they are inserted into the optical fiber transmission line 2. The optical fiber transmission line 1,
The optical signals s12 and s22 having the wavelength λ2 in 5 are output to the optical fiber transmission lines 2 and 6 as they are without passing through the optical fiber 68.

As described above, in the optical add / drop circuit according to the present embodiment, a single arrayed-waveguide diffraction grating type optical multiplexer / demultiplexer is used as two identical arrayed-waveguide diffraction grating type optical multiplexer / demultiplexers. By selecting such a loopback optical path pair and providing an optical switch, it is possible to realize exactly the same function as that of the first embodiment with a single arrayed waveguide diffraction grating type optical multiplexer / demultiplexer. That is, in addition to the effect of the first embodiment, it is not necessary to match the wavelength multiplexing / demultiplexing characteristics between the two arrayed waveguide diffraction grating type optical multiplexers / demultiplexers, and the yield is improved and the stability is improved. You can In this embodiment, the number of wavelength division multiplexing of the arrayed waveguide diffraction grating type optical multiplexer / demultiplexer 61 is set to 12 for simplicity, but the present invention is not limited to this, and in general, an array waveguide having a wavelength division number of 2N is used. If a waveguide diffraction grating type optical multiplexer / demultiplexer is used, it is possible to add / drop at a wavelength of N-1.

Further, in this embodiment and the following embodiments, two optical fiber transmission lines 1 and 5 are used for input.
Although the add / drop operation between two wavelength-multiplexed optical signals is realized, as described with reference to FIGS. 3 and 4 in the first embodiment, three input signals from three or more optical fiber transmission lines are provided. It is also possible to realize the add / drop operation between the wavelength-multiplexed optical signals. 8 and 9 show circuit configuration examples in which the circuits corresponding to FIGS. 3 and 4 are realized by one arrayed waveguide diffraction grating type optical multiplexer / demultiplexer 61, respectively.

In the circuit shown in FIG. 8, the third input optical fiber transmission line 7 is connected to the input waveguide 63c and the third output optical fiber transmission line 8 is connected to the output waveguide 67c. Then, the 2 × 2 optical switches 52 and 5 for switching the paths are respectively provided between the loopback optical paths 68d and 68f, 68g and 68h, 68k and 68l.
3, 54 are provided respectively. Then, by switching the 2 × 2 optical switch 54, the optical fiber transmission line 1,
The optical signals s112 and s212 of the wavelength λ12 (first wavelength group) input from the optical fiber 5 are output to the optical fiber transmission lines 2 and 6 or the optical fiber transmission lines 6 and 2, respectively.

By switching the 2 × 2 optical switch 53, the wavelength λ9 input from the optical fiber transmission lines 1 and 7 can be obtained.
The optical signals s19 and s39 of the (second wavelength group) are output to the optical fiber transmission lines 2 and 8 or the optical fiber transmission lines 8 and 2, respectively. Further, by switching the 2 × 2 optical switch 52, the optical signals s26 and s36 of the wavelength λ6 (third wavelength group) input from the optical fiber transmission lines 5 and 7 are transmitted to the optical fiber transmission lines 6 and 8 or It is output to the optical fiber transmission lines 8 and 6, respectively. In this way, the add / drop operation is realized between the two wavelength division multiplexed signals of the three wavelength division multiplexed optical signals for each wavelength of the signal light.

Further, in the circuit shown in FIG. 9, instead of the 2 × 2 optical switches 52 to 54 shown in FIG. 8, a 3 × 3 optical switch 99b for switching the paths among the three optical paths is used.
.About.99d. This 3 × 3 optical switch 99b,
The wavelengths λ6, λ9, and λ are set by
By appropriately switching the loopback paths of the 12 optical signals, the optical signals of wavelengths λ2 to λ6 respectively input from the three optical fiber transmission paths 1, 5 and 7 are converted into the three optical fiber transmission paths 2, 6 and 6. The wavelength add / drop operation of 3 inputs and 3 outputs that is appropriately distributed to 8 is realized. That is, the switching operation is realized among the three wavelength division multiplexed signals for each wavelength of the signal light.

In the present embodiment and the following embodiments described with reference to FIGS. 5, 8 and 9, the optical fiber transmission is sequentially performed from the end of the plurality of input waveguides and output waveguides. Connected to the road (eg 63a and 63b, 67
a and 67b), the present invention is not limited to this, and the input waveguides connecting the optical fiber transmission lines may be shifted (for example, 63b and 63c, 67a and 67b) or inverted (for example, 63a and 63b). , 67b and 67a) or separated (eg 63d and 63i, 67a).
c and 67j), a circuit having the same effect can be constructed. An example of such a configuration is shown in FIG.
A third embodiment will be described.

C: Third Embodiment FIG. 10 is a block diagram showing the structure of an optical add / drop multiplexer according to the third embodiment of the present invention. The circuit shown in this figure differs from that of the second embodiment described with reference to FIG. 5 in that the input optical fiber transmission lines 1 and 5 are the input waveguides of the arrayed waveguide diffraction grating type optical multiplexer / demultiplexer 61. It is connected to the waveguides 63c and 63b, and the connection of the optical fiber (loopback optical path) 68 is changed accordingly.

In the circuit shown in FIG. 10, an arrayed waveguide diffraction grating type optical multiplexer / demultiplexer 61 comprises a first waveguide 63m and an output waveguide 67m (m = a, c, ..., I, k). Optical multiplexer / demultiplexer, input waveguide 63p and output waveguide 67p (p =
b, d, ..., j, l) with a second optical multiplexer / demultiplexer
Considering it as one, it can be seen that it functions similarly to the optical add / drop circuit described with reference to FIG. 5 as described below.

In FIG. 10, signal lights s11, s15, s17, s19, and s111 of wavelengths λ1, λ5, λ7, λ9, and λ11 that have propagated through the optical fiber transmission line 1 are respectively optical switches 52, 53, 54, and. 55 and 56. Wavelength λ propagating in the optical fiber transmission line 5
1, λ5, λ7, λ9, λ11 signal lights s21, s2
The same applies to 5, s27, s29, s211. Therefore,
As shown in FIG. 10, 2 × 2 optical switches 52, 55, 56
Is in the bar state, and the 2 × 2 optical switches 53 and 54 are in the cross state, the add / drop is performed for the optical signals of the wavelengths λ5 and λ7. The optical signals s13 and s23 of the wavelength λ3 in the optical fiber transmission lines 1 and 5 are directly output to the optical fiber transmission lines 6 and 2 without passing through the optical fiber 68.

D: Fourth Embodiment FIG. 11 is a block diagram showing the structure of an optical add / drop multiplexer according to the fourth embodiment of the present invention. The optical add / drop circuit shown in this figure is characterized by an arrayed waveguide diffraction grating type optical multiplexer / demultiplexer 7
When 1 is equivalently used as two optical multiplexers / demultiplexers, unlike the second and third embodiments described above, light is bidirectionally transmitted in the arrayed waveguide diffraction grating type optical multiplexer / demultiplexer 71. It is in a place that is configured to pass.

This optical add / drop circuit has a wavelength between an input optical fiber transmission line 1, an output optical fiber transmission line 2 and an input optical fiber transmission line 5, and an output optical fiber transmission line 6. An arrayed waveguide diffraction grating type optical multiplexer / demultiplexer 71 having a multiplexing number of 12 is provided, and an optical fiber (loopback optical path) 78 is provided between the corresponding waveguides in the waveguides 73 and 78.

The optical fiber transmission lines 1 and 2 are respectively connected to the input / output waveguides 73b and 73a which are one of the twelve input / output waveguides 73a to 73l. Is connected to the input / output waveguides 77b and 77a. Of the plurality of optical fibers (loopback optical paths) 78, 78c and 78d, 78e and 78
The optical fiber pair (loopback optical path pair) of f, ..., 78k and 78l has 2 × 2 optical switches 52, 53 ,.
Are connected.

Next, the operation of the optical add / drop circuit shown in FIG. 11 will be described. Signal light s having wavelengths λ4, λ6, λ8, λ10, λ12 propagated through the optical fiber transmission line 1.
14, s16, s18, s110, and s112 are demultiplexed according to the relationship shown in FIG. 6 when passing through the arrayed waveguide diffraction grating type optical multiplexer / demultiplexer 71.
Propagate in c, 78e, 78g, 78i and 78k. Similarly, the wavelength λ 4, which has propagated through the optical fiber transmission line 5,
signal lights s24, s26 of λ6, λ8, λ10, λ12,
s28, s210, and s212 are the optical fibers 7 respectively.
It propagates through 8d, 78f, 78h, 78j, and 78l.

This is because the arrayed waveguide diffraction grating type optical multiplexer / demultiplexer 71 is used as an input / output waveguide 73p (p = b, d, ..., J,
l) and the input / output waveguide 77m (m = a, b, c, ..., I,
k) the first optical multiplexer / demultiplexer and the input / output waveguide 77p
It is easy to understand if it is considered as two, that is, the second optical multiplexer / demultiplexer composed of the input / output waveguide 73m. That is, from the single arrayed-waveguide diffraction grating type optical multiplexer / demultiplexer 71, the wavelength intervals are doubled and the wavelength-multiplexed / demultiplexed characteristics are equal, and the signal lights are arrayed waveguide diffraction grating-type optical multiplexer / demultiplexer 71. It functions as two optical multiplexers / demultiplexers that propagate in the opposite direction.

Therefore, with the configuration of FIG. 11, the first embodiment described with reference to FIG. 1 and the second embodiment described with reference to FIG.
It operates exactly like the embodiment. Optical switches 52, 53,
54, 55, and 56 have wavelengths λ4, λ6, and λ, respectively.
Since the signal lights of 8, λ10 and λ12 are input,
When the 2 × 2 optical switches 52, 55, and 56 are in the bar state and the 2 × 2 optical switches 53 and 54 are in the cross state, as shown in FIG. 5, it is possible to add / drop optical signals of wavelengths λ6 and λ8. That is, of the signal lights wavelength-multiplexed in the optical fiber transmission line 1, the signal lights s16,
s18 is branched and output to the optical fiber transmission line 6,
The remaining s14, s110, and s112 are directly output to the optical fiber transmission line 2. On the other hand, at this time, if the signal lights s26 and s28 having the wavelengths λ6 and λ8 have propagated through the optical fiber transmission line 5, they are inserted into the optical fiber transmission line 2.
The optical signal s of wavelength λ2 in the optical fiber transmission lines 1 and 5
12, s22 do not pass through the optical fiber 78, and are directly output to the optical fiber transmission lines 2 and 6.

As described above, according to the optical add / drop multiplexer of this embodiment, the same effect as that of the second embodiment described with reference to FIG. 5 can be obtained. In addition to this, in the present embodiment, when one arrayed waveguide diffraction grating type optical multiplexer / demultiplexer 71 functions as two arrayed waveguide diffraction grating type optical multiplexer / demultiplexer, the inside of the optical multiplexer / demultiplexer 71 is By adopting a skillful configuration in which the respective signal lights propagate in opposite directions, the following effects can be obtained, for example.

First, even if optical signals of wavelengths λ1, λ3, ..., λ11 are mixed in the optical fiber transmission lines 1 and 5, they are mixed in the optical fiber transmission lines 2 and 6 as they are. There is no. These signal lights pass through the arrayed waveguide diffraction grating type optical multiplexer / demultiplexer 71 once or an odd number of times, and then are output as lights propagating in the opposite directions in the optical fiber transmission lines 1 and 5, Optical fiber transmission line 1,5
It can be easily removed by inserting an optical isolator into. This is a great advantage when an optical fiber amplifier which generates spontaneous emission noise is used in the optical fiber transmission lines 1 and 5.

If the optical fibers (loopback optical paths) 78c and 78d are disconnected in the configuration of FIG.
Instead of interrupting the signal light of wavelength λ4, λ1, λ5,
It is possible to prevent the mixed optical signals of λ7, λ9, and λ11 from propagating in any optical fiber transmission line.

In this embodiment, of the plurality of input waveguides and output waveguides, the two waveguides (63a and 63b, 67a and 67b) from the end are connected to the optical fiber transmission line. The invention is not limited to this. For example, a circuit having an equivalent effect can be formed even if the input waveguide and the output waveguide connecting the optical fiber transmission lines are displaced, inverted, or spaced apart. be able to.

E: Fifth Embodiment FIG. 12 is a block diagram showing the structure of an optical add / drop multiplexer according to the fifth embodiment of the present invention. As shown in the figure, the feature of this optical add / drop circuit is that a single optical fiber (loopback optical path) is physically provided with two loops by providing a demultiplexer and a multiplexer in the middle of the loopback optical path. The wavelength multiplicity is improved by making it available as a back optical path.

This optical add / drop circuit comprises an arrayed waveguide diffraction grating type optical multiplexer / demultiplexer 1 having a wavelength multiplexing number of 6 between the input optical fiber transmission lines 1 and 5 and the output optical fiber transmission lines 2 and 6.
1 is provided, and the signal light output from the output waveguide 17 is input between the output waveguides 17 and the input waveguides 13 and is input to the input waveguide 13 corresponding to the output waveguides 17. A fiber (loopback optical path) 18 is provided. The optical fiber transmission lines 1 and 5 are connected to the input waveguides 13b and 13a, respectively, and similarly, the optical fiber transmission lines 2 and 6 are connected to the output waveguides 17b and 17a.

Further, the plurality of optical fibers (loopback optical paths) 18 are provided with optical fibers (loopback optical paths) 18c between corresponding input / output waveguides, that is, for example, between the output waveguide 17c and the input waveguide 13c. It In the middle of the optical fiber (loopback optical path) 18, a demultiplexer 91 and a multiplexer 92 are installed one by one in each optical path.
2 × 2 optical switches 94, 95, 9 between the multiplexer and the multiplexer 92.
6 are connected as shown.

Next, the operation of the optical add / drop circuit shown in FIG. 12 will be described. Signal lights s14, s15, s having wavelengths λ4, λ5, λ6 propagated through the optical fiber transmission line 1.
After passing through the arrayed waveguide diffraction grating type optical multiplexer / demultiplexer 11, 16 is demultiplexed according to the relationship shown in FIG. 18, and propagates in the optical fibers 18c, 18d and 18e, respectively. Similarly, the wavelength λ 4, which has propagated through the optical fiber transmission line 5,
The signal lights s24, s25, and s26 of λ5 and λ6 propagate in the optical fibers 18d, 18e, and 18f, respectively. That is, the optical fibers 18d and 18e have two different wavelengths.
Two signal lights are propagating.

Optical fiber (loopback optical path) 18i
The demultiplexer 91i and the demultiplexer 92i provided in (i = c, d, e, f) demultiplex and combine the above-mentioned two signal lights having different wavelengths. As the demultiplexer and the multiplexer, for example, an element using an asymmetric Mach-Zehnder interference system as shown in FIG. 13 may be used. The operation method of this element is almost the same as that of the optical switch described with reference to FIG.

The signal lights demultiplexed by the demultiplexer 91 are paired with the corresponding signal lights and input to the optical switches 94 to 96, and the outputs thereof are recombined by the multiplexer 92, and the optical fibers are recombined. It is re-inputted to the arrayed waveguide diffraction grating type optical multiplexer / demultiplexer 11 via (loopback optical path). Optical switch 9
Since signal lights of wavelengths λ4, λ5, and λ6 are input to 4, 95 and 96, respectively, as shown in FIG. 12, the 2 × 2 optical switch 96 is in the bar state and the 2 × 2 optical switches 94 and 95 are in the bar state.
Is in a cross state, it is possible to add / drop optical signals of wavelengths λ4 and λ5. That is, of the signal lights of wavelengths λ4, λ5, and λ6 wavelength-multiplexed in the optical fiber transmission line 1, the signal lights s14 and s15 of wavelengths λ4 and λ5 are branched and output to the optical fiber transmission line 6, and the rest. S1
6 is directly output to the optical fiber transmission line 2. On the other hand, at this time, if the signal lights s24 and s25 having the wavelengths λ4 and λ5 have propagated through the optical fiber transmission line 5, they are inserted into the optical fiber transmission line 2.

The wavelength λ in the optical fiber transmission lines 1 and 5
Among the optical signals of 1, λ2, λ3, s12, s13, s2
1, s22 do not pass through the optical fiber 18 and are directly output to the optical fiber transmission line 2 or 6. The optical signals s11 and s23 propagate through the optical fiber 18, but are output to the optical fiber transmission lines 2 and 6 without passing through the optical switch.

That is, in the present embodiment, by adopting a skillful configuration in which a demultiplexer and a multiplexer are arranged in the loopback optical path and an optical switch is arranged between them, the first embodiment described with reference to FIG. It is possible to obtain the same effect as that of the second embodiment without changing the wavelength interval to twice the wavelength interval of the arrayed waveguide diffraction grating type optical multiplexer / demultiplexer itself as in the second embodiment. I can.

In the present embodiment, the number of wavelength division multiplexing of the arrayed waveguide diffraction grating type optical multiplexer / demultiplexer 61 is set to 6 for simplification, but the present invention is not limited to this, and generally the number of wavelength division multiplexing N. If the arrayed waveguide diffraction grating type optical multiplexer / demultiplexer is used, it is possible to add / drop at the wavelength of N-3.

F: Sixth Embodiment FIG. 14 is a block diagram showing the structure of the optical add / drop multiplexer according to the sixth embodiment of the present invention. As shown in the figure, this optical add / drop circuit is characterized by using a circulator when connecting an optical fiber transmission line to the circuit.
The configuration is such that one optical fiber can be used as a loopback optical path for two signal lights propagating in both directions.

In this optical add / drop circuit, the optical fiber transmission line 1 for input and the optical fiber transmission line 6 for output are connected to each other.
Between the terminal optical circulator 88 and the three-terminal optical circulator 89 that connects the input optical fiber transmission line 5 and the output optical fiber transmission line 2, an arrayed waveguide diffraction grating type optical multiplexer / demultiplexer with a wavelength multiplexing number of 6 is provided. A waveguide 11 is provided with a container 11.
An optical fiber 18 is provided between the corresponding waveguides in each of 3 and 17.

The optical circulator 88 is connected to the input / output waveguide 13a, which is one of the six input / output waveguides 13a to 13f, and similarly the optical circulator 89.
Are connected to the input / output waveguide 17a, which is one of the six input / output waveguides 17a to 17f. , 18f are connected to transmission / reflection switching optical switches 81b, 81c, ..., 81f, respectively.

Here, the transmission / reflection switching type optical switch 81
May be configured as shown in FIG. 15, for example. Figure 15
The optical switch shown in FIG.
A 3 dB coupler 514 is formed by a quartz waveguide, and mirrors 816 and 817 are arranged at the ends of the branched waveguides to form a two-beam interference system (Michelson interference system).
Here, an electric current is applied to the heater 513 to change the temperature of one of the waveguides, and an optical switch operation for switching between reflection and transmission is realized by a change in the refractive index due to the temperature change.
That is, at a certain current value I1, the optical fibers 518, 5
The optical signals input from 19 are the optical fibers 51, respectively.
It is output to 9,518 (transmission state) and another certain current value I
In 2, the light is output to the optical fibers 818 and 819 (reflective state).

Next, the operation of the optical add / drop multiplexer circuit shown in FIG. 14 will be described. Signal lights s12 and s1 having wavelengths λ2, λ3, ..., λ6 propagated through the optical fiber transmission line 1.
3, s14, s15, and s16 are coupled to the waveguide 13a via the circulator 88 and, after passing through the arrayed waveguide diffraction grating type optical multiplexer / demultiplexer 11, are demultiplexed according to the relationship shown in FIG. Fibers 18b, 18
c, ..., Propagates in 18f. Similarly, the signal lights s22, s23, s24, s25, and s26 of the wavelengths λ2, λ3, ..., λ6 that have propagated through the optical fiber transmission line 5 pass through the circulator 89 and the waveguide 17a, respectively, and the optical fiber 18b. , 18c, ..., 18f propagate in the opposite direction.

This corresponds to the use of the arrayed waveguide diffraction grating type optical multiplexer / demultiplexer 11 as two optical multiplexer / demultiplexers having exactly the same characteristics with different input / output directions. That is, one optical fiber 18i (i = b, c, ..., F) constitutes a loopback optical path for each signal light propagating in both directions, and one fiber is equivalent to one pair. (Two)
Can be regarded as the optical path of. Therefore, by switching the reflection / transmission of this optical path pair with the optical switches 81b, 81c, ..., 81f, the same function as that of the first embodiment described with reference to FIG. 1 can be obtained.

That is, the optical switch 81i (i = b,
When c, ..., F) are in the transmissive state, the waveguide 17i (i =
b, c, ..., F) output optical signals s1i (i =
2, 3, ..., 6) are waveguides 13i (i = b, c ,.
f), and is input to the waveguide 13i (i = b, c, ..., F).
The optical signal s2i (i = 2, 3, ..., 6) output from is input to the waveguide 17i (i = b, c, ..., F). Therefore, the optical signal s1i is output to the optical fiber transmission line 2 via the waveguide 17a and the optical circulator 89, while the optical signal s2i is output to the optical fiber transmission line 6 via the waveguide 13a and the optical circulator 88. To be done.

On the other hand, the optical switch 81i (i = b, c,
,, f) is in the reflective state, the waveguide 17i (i = b,
c, ..., F) output optical signals s1i (i = 2,
3, ..., 6) are waveguides 17i (i = b, c, ..., Again)
f) and is input to the waveguide 13i (i = b, c,
, F) output from the optical signal s2i (i = 2, 3,
, 6) are again input to the waveguide 13i (i = b, c, ..., F). Therefore, the optical signal s1i is transmitted to the waveguide 13
a, output to the optical fiber transmission line 6 via the optical circulator 88, while the optical signal s2i is output to the optical fiber transmission line 2 via the waveguide 17a and the optical circulator 89.

For example, as shown in FIG. 14, the optical switch 8
1b, 81e and 81f are in a transmissive state, optical switches 81c and
When 81d is in the reflective state, it is possible to add / drop optical signals of wavelengths λ3 and λ4. That is, of the signal lights wavelength-multiplexed in the optical fiber transmission line 1, the wavelength λ
The signal lights s13 and s14 of 3 and λ4 are branched and output to the optical fiber transmission line 6, and the remaining s12, s15, and s1.
6 is directly output to the optical fiber transmission line 2. On the other hand, at this time, if the signal lights s23 and s24 having the wavelengths λ3 and λ4 have propagated through the optical fiber transmission line 5, they are inserted into the optical fiber transmission line 2. Optical fiber transmission lines 1 and 5
The optical signals s11 and s21 of the wavelength λ1 are
8 and the optical switch 81, and is output as it is to the optical fiber transmission lines 2 and 6.

As described above, in the optical add / drop circuit according to the present embodiment, the input / output optical fiber transmission line to the circuit is connected with the circulator, and transmission and reflection are switched in the loopback optical path formed by the optical fiber. With the skillful configuration of arranging the optical switches, it becomes possible to cause a single arrayed waveguide diffraction grating type optical multiplexer / demultiplexer to function as two optical multiplexer / demultiplexers having exactly the same characteristics in different signal light propagation directions. That is, there is an advantage that the same effect as that of the first embodiment described with reference to FIG. 1 can be realized by one arrayed waveguide diffraction grating type optical multiplexer / demultiplexer. In this embodiment only, n
It cannot be expanded to input n output.

[0097]

As described above, according to the present invention, switching of wavelengths to be added / dropped can be performed independently for each wavelength only by switch control, and signal lights of a plurality of wavelengths can be dropped. It is possible to provide an optical add / drop circuit that can be added and can perform wavelength multiplexing with high density at a wavelength interval that is at least twice the wavelength interval of the wavelength division multiplexing optical multiplexer / demultiplexer. Furthermore, since it is possible to control the switching of the signal light of each wavelength among multiple wavelength-multiplexed lights independently, it is easy to control when constructing an optical transmission system or optical switching system that switches the destination of optical signals based on the wavelength. It is extremely effective.

[Brief description of drawings]

FIG. 1 is a block diagram showing a configuration of an optical add / drop multiplexer according to a first embodiment of the present invention.

FIG. 2 is a block diagram showing a configuration example of a 2 × 2 optical switch used in the optical add / drop circuit according to the embodiment.

FIG. 3 is a block diagram showing an extension example of the optical add / drop circuit according to the embodiment.

FIG. 4 is a block diagram showing a second extension example of the optical add / drop circuit according to the same embodiment.

FIG. 5 is a block diagram showing the configuration of an optical add / drop multiplexer according to a second embodiment of the present invention.

FIG. 6 is a diagram for explaining wavelength multiplexing / demultiplexing characteristics of an arrayed waveguide diffraction grating type optical multiplexer / demultiplexer having a wavelength division number of 12 in the example.

FIG. 7 is a wavelength division / multiplexing of an arrayed-waveguide diffraction grating type optical multiplexer / demultiplexer having a wavelength-division multiplexed number of 6 which is equivalently configured from an arrayed-waveguide diffraction grating type optical multiplexer / demultiplexer having a wavelength-division multiplexing number of 12 in the embodiment. It is a figure explaining a wave characteristic, (a) shows the characteristic of the 1st optical multiplexer / demultiplexer, and (b) shows the characteristic of the 2nd optical multiplexer / demultiplexer, respectively.

FIG. 8 is a block diagram showing an extension example of the optical add / drop circuit according to the embodiment.

FIG. 9 is a block diagram showing a second extension example of the optical add / drop multiplexer according to the same embodiment.

FIG. 10 is a block diagram showing a configuration of an optical add / drop multiplexer according to a third embodiment of the present invention.

FIG. 11 is a block diagram showing a configuration of an optical add / drop circuit according to a fourth embodiment of the present invention.

FIG. 12 is a block diagram showing the structure of an optical add / drop multiplexer according to a fifth embodiment of the present invention.

FIG. 13 is a block diagram showing a configuration example of a demultiplexer and a multiplexer used in the optical add / drop multiplexer according to the same embodiment.

FIG. 14 is a block diagram showing the configuration of an optical add / drop multiplexer according to a sixth embodiment of the present invention.

FIG. 15 is a block diagram showing a configuration example of a transmission / reflection switching type optical switch used in the optical add / drop circuit according to the same embodiment.

FIG. 16 is a diagram illustrating the principle of a conventional optical add / drop circuit.

FIG. 17 is a block diagram showing a configuration example of a conventional optical add / drop circuit.

FIG. 18 is a diagram illustrating wavelength multiplexing / demultiplexing characteristics of an arrayed waveguide diffraction grating type optical multiplexer / demultiplexer used in a conventional optical add / drop circuit.

FIG. 19 is a block diagram showing a configuration example of another conventional optical add / drop circuit.

FIG. 20 is a diagram for explaining a function obtained by another conventional optical add / drop circuit, in which (a) is an add / drop function of a signal having an arbitrary one wavelength, and (b) is a signal having multiple arbitrary wavelengths. (C) shows a function of exchanging optical signals of arbitrary one or a plurality of wavelengths.

FIG. 21 is a diagram illustrating wavelength selection characteristics of another conventional optical add / drop circuit.

[Explanation of symbols]

1, 2, 5, 6, 7, 8 Optical fiber transmission line 11, 41, 61, 71, 91 Arrayed waveguide diffraction grating type optical multiplexer / demultiplexer 13a to 13f, 43a to 43f, 63a to 63l, 7
3a to 73l, 93a to 93f (input) waveguide 14, 15, 44, 45, 64, 65, 74, 75, 9
4,95 slab waveguide 16,46,66,76 arrayed waveguide diffraction grating 17a to 17f, 47a to 47f, 67a to 67l, 7
7a to 77l, 97a to 97f (output) waveguide 18b to 18f, 48b to 48f, 68c to 68l, 7
8c-78l, 98 Optical fiber (loop back optical path) 31 LiNbO3 waveguide type acousto-optic filter 32,35 Polarization splitter 33 Transducer 34a, 34b Waveguide 37 Oscillator 51b-51f, 52-56, 94-96 2x2 light Switches 81b to 81f Transmission / reflection switching optical switch 88,89 Optical circulator 99b to 99f 3 × 3 optical switch 512 Waveguide substrate 513 Heater 514, 515 3 dB coupler 516-519 Optical fiber 816,817 Mirror

Claims (6)

[Claims] 1. An n propagating each wavelength-division multiplexed optical signal
(N is a natural number of 2 or more) An optical add / drop circuit for adding / dropping an optical signal of a predetermined wavelength between two optical paths, each having a plurality of pairs of input / output ports and a pair of input / output ports for external connection. N pairs of wavelength division multiplexing optical multiplexers / demultiplexers in which other pairs of input / output ports except output ports are loop-connected by loopback optical paths, and n loopback optical paths corresponding to each optical multiplexer / demultiplexer are provided. And an n × n matrix switch that switches the path between these optical paths. 2. A wavelength-division-multiplexed optical signal propagates n
(N is a natural number of 2 or more) An optical add / drop circuit that adds / drops an optical signal of a predetermined wavelength between optical paths, and has a plurality of pairs of input / output ports and n pairs of input / output ports for external connection. And a pair of wavelength division multiplexing optical multiplexers / demultiplexers formed by loop-connecting other pairs of input / output ports by a loopback optical path, and n loopback optical paths inserted in the loopback optical path of the optical multiplexer / demultiplexer. An optical add / drop circuit, comprising: an n × n matrix switch for switching a path between the two. 3. An n propagating each wavelength-multiplexed optical signal
(N is a natural number of 2 or more) An optical add / drop circuit that adds / drops an optical signal of a predetermined wavelength between optical paths, and has a plurality of pairs of input / output ports and n pairs of input / output ports for external connection. And a pair of wavelength division multiplexing optical multiplexers / demultiplexers formed by loop-connecting other pairs of input / output ports by a loopback optical path, and each optical path being inserted into each loopback optical path of the optical multiplexer / demultiplexer. A demultiplexer and a multiplexer for branching for each predetermined section, and an n × n matrix switch that is inserted in a branch optical path between the demultiplexer and the multiplexer and switches a path between n loopback optical paths. An optical add / drop multiplexer circuit comprising: 4. The optical add / drop circuit according to claim 1, wherein the n × n matrix switch is replaced with a 2 × 2 switch for each two loopback optical paths to be added / dropped. An optical add / drop circuit that is provided with. 5. An optical add / drop circuit for adding / dropping an optical signal of a predetermined wavelength between two optical paths in which wavelength-multiplexed optical signals propagate in opposite directions, and a plurality of input / output terminals on each of two side surfaces. A wavelength division multiplexing optical multiplexer / demultiplexer having ports and excluding two pairs of input / output ports for external connection, and each pair of input / output ports in the same side face are loop-connected by a loopback optical path. An optical add / drop circuit which is provided in a pair of loopback optical paths between different side surfaces of the optical multiplexer / demultiplexer and which switches a path between these two optical paths. 6. Two wavelength-multiplexed optical signals propagate respectively
An optical add / drop circuit that adds / drops an optical signal of a predetermined wavelength between two optical paths, and has a plurality of pairs of input / output ports, and a pair of input / output ports other than one pair of input / output ports for external connection. One wavelength division multiplexing optical multiplexer / demultiplexer in which ports are loop-connected by a loopback optical path, and first and second connecting the two external optical paths and an input / output port for external connection of the optical multiplexer / demultiplexer, respectively. A second three-terminal optical circulator, and a transmission / reflection switch that is inserted in each loopback optical path of the optical multiplexer / demultiplexer and switches between transmission and reflection of an optical signal propagating in each optical path. Optical add / drop circuit.