JPH05188408A - Wavelength selector - Google Patents

Abstract

PURPOSE:To obtain a high extinction rate and to reduce the power consumption by connecting a Mach-Zehnder type interference type wavelength demultiplexer with the output ports of plural optical switches connected to the respective output ports of the wavelength demultiplexer to an input port to be cross-port constitution. CONSTITUTION:A wavelength unit 11 is equipped with the Mach-Zehnder interference type wavelength demultiplexer 7, thermooptical effect type optical switches 12 connected to the respective output ports, and a Mach-Zehnder interference type wavelength multiplexer 9 connected to their output ports; and the output ports of the optical switches 12 are connected to the input port in the cross-port constitution to obtain the high extinction rate. Further, the wavelength selector 13 is so constituted that the optical switches are in a no-voltage operation state when normally used; and then the reliability can be increased and the powder consumption is reduced.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a wavelength selector capable of arbitrarily selecting an optical signal having a required wavelength from wavelength multiplexed optical signals.

[0002]

2. Description of the Related Art Conventionally, in bidirectional wavelength-multiplexed optical communication, a wavelength-multiplexing component has been used as a means for arbitrarily selecting an optical signal of a required wavelength from wavelength-multiplexed optical signals. This wavelength multiplexing component is generally a combination of a wavelength demultiplexer or wavelength multiplexer using a diffraction grating and an optical switch using thermo-optical effect, electro-optical effect, acousto-optical effect, magneto-optical effect, etc. In the wavelength demultiplexer and the wavelength multiplexer, it is necessary that the loss (insertion loss) for the wavelength to be separated is small and the crosstalk is large, and that the optical switch has a large extinction ratio. For example,
A TO type optical switch utilizing the thermo-optic effect has obtained an extinction ratio of about 20 dB in the case of a 2 × 2 switch (Reference 1: Kawauchi, “Applications to silica-based optical waveguides and integrated optical components”). Optics Vol. 18, No. 12, 1989), FIG.
In the wavelength multiplexing component 1 used in the FM transmission system as shown in 0, a plurality of 2 × 2 TO type optical switches 4, 4, ... Are cascaded between the optical fibers 3, 3 ,. Is connected in two stages, and the overall extinction ratio is 17 dB.

Further, an acousto-optic variable wavelength filter (reference 2: O plus E, New Technology Communications, October 1991) and a waveguide type frequency selective switch (reference 3: Toba et al., "100ch optical FDM information distribution transmission" Consideration of system configuration method ", OCS-89-64) and other wavelength multiplexing components are also proposed. Also,
An optical switching device 5 as shown in FIG. 11 has also been proposed. This optical switching device 5 includes a Mach-Zehnder optical interference type wavelength demultiplexer 7 between a plurality of optical fiber cables 6 and 6 for transmitting a wavelength multiplexed signal 2, and a plurality of directional coupler type waveguide optical switches arranged in parallel. , 8, Mach-Zehnder interferometer type wavelength multiplexers 9 are connected in cascade (for example, Japanese Patent Laid-Open No. 6-58242).
3-131687).

[0004]

However, the conventional wavelength multiplexing component has various problems and drawbacks as described below. For example, a wavelength multiplexing component that combines a wavelength demultiplexer, a wavelength multiplexer, an optical switch, and the like can realize a high extinction ratio characteristic, but has a large configuration scale (for example, when four wavelengths are selected). 1
It has a size of about 2 × 11 cm ² ) and has a drawback that it consumes a large amount of power and cannot be integrated. In particular, for an optical switch, the extinction ratio is 27 dB or more when transmitting an AM video signal, and the extinction ratio is 17 dB or more when transmitting an FM video signal (Reference 2: Matsui et al., "Al.
1-Band TV service type optical distribution system ", 1991 IEICE Spring National Convention) is required, but the extinction ratio of the conventional 2x2TO optical switch 4 is about 20 dB. In addition, it cannot be used in the AM transmission system, and as described above, in the FM transmission system, two 2 × 2 TO type optical switches 4, 4, ... Are connected in cascade in view of the extinction ratio of the optical switch. Could only be used.

The one using an acousto-optic variable wavelength filter or a waveguide type frequency selective switch is intended for use in an optical FDM transmission system and allows continuous wavelength selection. The extinction ratio of the variable wavelength filter is about 13.6 dB, and the extinction ratio of the waveguide type frequency selective switch is about 14.8 dB. Both of them do not satisfy the required extinction ratio, so AM / FM transmission is impossible. Is. Furthermore, they have the disadvantage that only one wavelength can be selected at a time. Further, in the above-mentioned optical switching device 5, the directional coupler type waveguide optical switch 8 is used, but since the characteristics of these optical switches 8 and the designation of the ports used for input / output are not mentioned, extinction There is a problem that the specific characteristics and applicable area are unknown.

The present invention has been made in view of the above circumstances, and it is possible to select an arbitrary number of wavelengths from a wavelength division multiplexed optical signal and has a high extinction ratio characteristic required for AM transmission and the like. It is to provide a wavelength selector.

[0007]

In order to solve the above problems, the present invention employs the following wavelength selector. That is, the wavelength selector according to claim 1 is a Mach-Zehnder optical interference type wavelength demultiplexer, a plurality of thermo-optical effect type optical switches connected to each output port of the wavelength demultiplexer, and these optical demultiplexers. In a wavelength selector comprising a Mach-Zehnder optical interference type wavelength multiplexer connected to each output port of the switch, the output port of the optical switch is a cross port with respect to the input port. There is.

A wavelength selector according to a second aspect is the wavelength selector according to the first aspect, wherein the plurality of optical switches have at least a phase difference in optical path length between the directional couplers.
The optical switch that operates so as to output from the cross port when no voltage is applied to the thin film heater for changing the phase, and not output from the cross port when voltage is applied, and the optical path length between the directional couplers. An optical switch that operates so that the phase difference is π, the cross port does not output when a voltage is not applied to the thin film heater for changing the phase, and the cross port outputs when a voltage is applied,
It is characterized by including either one of.

The wavelength selector according to a third aspect is the wavelength selector according to the first or second aspect, wherein the wavelength demultiplexer, the optical switch and the wavelength multiplexer are integrated on a semiconductor substrate. It is characterized by

A wavelength selector according to a fourth aspect is the wavelength selector according to the first, second or third aspect, characterized in that an asymmetric optical branching device is provided on the input side of the wavelength demultiplexer. There is.

[0011]

In the wavelength selector according to the first aspect of the present invention, a high extinction ratio can be obtained by making the output port of the optical switch a cross port with respect to the input port.

Further, in the wavelength selector according to claim 2, at least the phase difference of the optical path length between the directional couplers is set to 0,
Phase difference of optical path length between optical switch and directional coupler that operates so as to output from cross port when voltage is not applied to thin film heater for changing phase and not output from cross port when voltage is applied Is set to π, and includes an optical switch that operates so as not to output from the cross port when a voltage is not applied to the thin film heater for changing the phase and to output from the cross port when a voltage is applied. As a result, the wavelength selector can be configured so that there is no voltage when the operating state of these optical switches is always in use, and therefore the reliability is high and the power consumption is low.

In the wavelength selector according to the third aspect of the present invention, since the wavelength demultiplexer, the optical switch and the wavelength multiplexer are integrated on a semiconductor substrate, downsizing and high reliability are possible. Power consumption is also reduced. The semiconductor substrate is a single crystal substrate such as silicon (Si), InP, GaAs, I.
A III-V group compound semiconductor substrate such as nGaAs or InGaAsP or a II-VI group compound semiconductor substrate such as ZnSe or ZnS is preferably used.

Further, in the wavelength selector according to the present invention, the asymmetric optical branching device is provided on the input side of the wavelength demultiplexer, so that the incident light can be branched into a plurality at a predetermined ratio. Become.

[0015]

Embodiments of the present invention will be described below with reference to the drawings. (Embodiment 1) FIG. 1 shows a wavelength selector 11 according to Embodiment 1 of the present invention.
It is a schematic block diagram of. The wavelength selector 11 includes a wavelength demultiplexer 7, a wavelength multiplexer 9, TO type optical switches 12, 12, ...
Are integrated on the same silicon (Si) substrate, and these TO type optical switches 12, 12, ... Are controlled by the wavelength selection control device 13 so as to perform a predetermined operation.
The size of the wavelength selector 11 is about 8.5 × 1 cm ² when four wavelengths are selected.

In this TO type optical switch 12, as shown in FIG. 2, a pair of waveguides 23 and 24 are formed on a substrate 22, and a part of these waveguides 23 and 24 are brought close to each other to direct each other. The couplers 25 and 26 are used. Further, a thin film heater 27 is formed on one of the waveguides 24, and the waveguide 2
3, an input port 28 is provided on the input side, a parallel output port 29 is provided on the output side, and a cross output port 30 is provided on the output side of the waveguide 24.

Next, the operating characteristics of the TO type optical switch 12 will be described. The operating characteristics of the TO type optical switch 12 can be expressed by the following equation. I ₁ / I ₀ = (1-2k) ² cos ² (Δφ / 2) + sin ² (Δφ / 2) (1) I ₂ / I ₀ = 4k (1-k) cos ² (Δφ / 2) (2) However, I ₀ : input port level I ₁ : parallel output port level I ₂ : cross output port level k: optical coupler coupling ratio φ: phase shift amount. This equation is an equation when the lengths of both optical paths between the directional couplers 25 and 26 of the TO type optical switch 12 are the same, and the phase difference between both optical paths at this time is zero.

FIG. 3 is a diagram showing the relationship between the power applied to the thin film heater of the TO type optical switch 12 and the transmittance. In this figure, ● indicates the output from the cross output port,
The circles indicate the output from the parallel output port. As is clear from this figure, when no voltage (power in the figure) is applied (when there is no power), the output is from the cross output port, but as the voltage is applied, the output from the parallel output port becomes larger and the cross output port becomes larger. No output to the output port. In the vicinity of the applied power of about 420 mW, the difference between the output from the parallel output port and the output from the cross output port becomes maximum, and the extinction ratio becomes 40 dB or more. When more voltage is applied, the output from the cross output port becomes larger than the output from the parallel output port, and the difference between the output from the cross output port and the output from the parallel output port is around the applied power of about 820 mW. Maximum and output from parallel output port is -20d
It is about B.

The reason why the TO type optical switch 12 exhibits the above-mentioned characteristic -I (when no voltage is applied: output from the cross output port, when applied voltage: no output from the cross output port) is given by the above formula (1). In (2) and (2), the cos term in the equation (1) remains due to the k value due to manufacturing variations, and the extinction ratio of the parallel output port becomes small, while the output from the cross output port is obtained by the equation ( This is because, as shown in 2), since it consists of a single term, a high extinction ratio can be obtained irrespective of variations in the k value. Therefore, it is possible to obtain an extinction ratio of 40 dB or more by using only the cross output port, which has conventionally been an extinction ratio of about 20 dB.

Further, by utilizing the property that a high extinction ratio can be obtained by using only this cross output port as an output port, a property -II (when no voltage is applied: no cross output port is provided) which is the opposite of the above property -I. Design a TO type optical switch for output and applied voltage: output from the cross output port. The reason is that there is no voltage (characteristic-I:
The output from the cross output port, characteristic-II: The cross output port has no output), so the reliability is high, and the voltage is applied to this TO type optical switch only when the wavelength is necessary (or unnecessary), and the optical path is set. This is because switching can reduce power consumption.

FIG. 4 is a block diagram of such a TO type optical switch 31. This TO type optical switch 31 has a characteristic-I.
The optical switch having the characteristic -II opposite to that of the TO type optical switch 12 of FIG. 1 is such that the optical path length difference between the directional couplers 25 and 26 of the waveguide 23 is the phase difference π with the TO type optical switch 12. The only difference is that it is designed.

FIG. 5 is a diagram showing the relationship between the optical output level of the TO type optical switch 31 and the electric power applied to the thin film heater. As is clear from this figure, this TO type optical switch 31
Shows that the characteristics-II (no voltage: no output at the cross output port, no voltage, output from the cross output port) are excellent.

As described above, according to the wavelength selector 11 of this embodiment, the wavelength demultiplexer 7, the wavelength multiplexer 9, and the TO type optical switches 12, 12, ... Are formed on the same silicon (Si) substrate. Since they are integrated on top of each other, the size can be reduced and the economy can be improved. Further, since the TO type optical switches 12, 12, ... Are connected in parallel, any number of wavelengths can be selected. Since the output port of the TO type optical switch 12 (31) is the cross output port 30 with respect to the input port 28, a high extinction ratio can be obtained.

Since two types of TO type optical switches 12 and 31 having different characteristics are arbitrarily combined,
A high extinction ratio and high reliability can be obtained, and power consumption can be reduced. Therefore, it is possible to obtain excellent effects such as enabling various application forms.

(Second Embodiment) FIG. 6 is a schematic configuration diagram of an AM video transmission system 41 which is an example to which the wavelength selector 11 of the first embodiment is applied. This AM video transmission system 41 is
A plurality of AM video signal generators 42, 42, ..., Wavelength λ ₁ ,
λ _2, λ _3, λ ₄ is different four electrical / optical (E /
O) converters 43, 43, ..., Wavelength demultiplexer 7, optical fiber cable 6, optical branching device 44, wavelength selector 11, and optical / electrical (O / E) converter 45.

Here, the characteristics of the TO type optical switch-I,
The combination of IIs is as follows: (a) Normally, no wavelength is required, and the wavelength is selected only when it is required.
1 (characteristic-II) is used. (B) Normally, the required M wavelengths are selected, and the required number of wavelengths is selected from the remaining number of wavelengths L. The TO type optical switch for selecting the M wavelengths is the TO type optical switch 1.
2 (characteristic-I) is used, and the TO-type optical switch for L wavelength selection uses the TO-type optical switch 31 (characteristic-II).

Specifically, the TO type optical switch 12 (characteristic-I) (when there is no voltage: output from the cross output port) is used for selecting the wavelength λ ₁ . The reason is that 11ch re-broadcast of airwaves on wavelength λ ₁ (eg NHK, NHK Education, Japan T
This is because it is possible to always receive in a voltageless state by inserting (V etc.). Other wavelengths λ ₂ ,
Regarding λ ₃ and λ ₄ , the TO type optical switch 31 (characteristic-I
I) (no voltage: no output at cross output port, applied voltage: output from cross output port) is used.

In this AM video transmission system 41, a plurality of AM video signal generators 42, 42, ...
After frequency-multiplexing various M-modulated AM video signals, the signals are input to four electric / optical (E / O) converters 43, 43, ... And the four converted optical outputs are wavelength-multiplexed by the wavelength multiplexer 7. Are multiplexed and transmitted as a wavelength multiplexed signal 2 in the optical fiber cable 6. The transmitted four wavelength-multiplexed signals 2 are branched by the optical branching device 44, and enter the wavelength selector 11.
In the wavelength selector 11, four wavelengths (λ
₁ , λ ₂ , λ ₃ , λ ₄ ) and then connected in parallel 4
, Which are respectively incident on the two TO type optical switches 12, 12, ... And these four optical outputs are combined by the wavelength multiplexer 9.
It is converted into an electric signal by the optical / electrical converter 45.

As described above, according to the AM video transmission system 41, since the extinction ratio of the TO type optical switches 12 and 31 used in the wavelength selector 11 is 40 dB or more, an AM video signal is required. Extinction ratio 27d
B or more can be sufficiently satisfied, and image quality can be sufficiently satisfied.

Further, since the number of channels is divided into four wavelengths, AM modulation can be performed in accordance with the TV channel arrangement (11 channels for one wavelength) for each wavelength, and 40 or more channels can be received. Become. Further, it is possible to reduce the deterioration of the image quality due to the second-order distortion and the third-order distortion that occur in the AM image transmission, the tuner for multi-channel reception which has been conventionally required is unnecessary, and the reliability and the consumption are low. It is possible to achieve excellent effects such as the ability to configure a power system.

(Third Embodiment) FIG. 7 is a schematic configuration diagram of a wavelength division multiplexing transmission system 51. This wavelength division multiplexing transmission system 5
1, a plurality of asymmetrical optical branching devices 52, 52, ... Are provided on one optical fiber cable 6, and a wavelength selector 11 is provided on each branching side of two output ports of each asymmetrical optical branching device 52. It is a thing. Here, the asymmetric optical branching device 52
Has a low loss on the trunk side of the two output ports,
It is constructed so that the branch side has a high loss.

According to this wavelength division multiplexing transmission system 51,
WDM signal 2 propagated through the optical fiber cable 6
Can be branched by the asymmetrical optical branching device 52 into a main line side and a branching side at a predetermined ratio. Here, since the main line side has low loss and the branch side has high loss, long-distance transmission is possible. Moreover, since the required extinction ratio of the electric stage is 80 dB, the extinction ratio of the optical stage is required to be 40 dB.
The output of the cross output port of the optical switches 12 and 31 is 4
It is applicable because 0 dB or more is obtained.

Further, in the wavelength division multiplexing transmission system 51, it is possible to adopt a mode in which a frequency is assigned to each area. For example, the number of required channels in each area may increase or decrease depending on the number of mobile units (the number of mobile phones and the number of mobile phones), and in some cases, an area where communication becomes impossible occurs. By applying the wavelength division multiplexing transmission system 51, the problem of channel shortage can be solved.

(Fourth Embodiment) FIG. 8 is a schematic configuration diagram of a mobile communication system 61 as an example to which the wavelength division multiplex transmission system 51 of the third embodiment is applied. This mobile communication system 6
1 divides the entire area Z in three zones of the zone Z ₁ to Z _3, wavelength multiplexing transmission system 5 to each zone Z ₁ to Z ₃
1 is applied. This mobile communication system 61
Then, the wavelengths λ ₁ to λ ₃ are assigned to the zones Z _{1 to} Z _3, respectively, and the number of moving bodies in the zone Z ₃ increases rapidly,
When the number of channels seems to be insufficient, the wavelength λ ₄ can be assigned to Z ₃ by operating the wavelength selector in the zone Z ₃ . For example, in the zone Z ₃ , the TO type optical switch for selecting the wavelength λ ₃ is the TO type optical switch 1
2 (characteristic-I) (when there is no voltage: output from the cross output port), the TO type optical switch for selecting wavelengths λ ₁ , λ ₂ and λ ₄ is the TO type optical switch 31 (characteristic-II) (no voltage). (Time: no output at cross output port, applied voltage: output from cross output port) is used. When the number of moving objects increases rapidly, voltage is applied to TO type optical switch 31 for selecting wavelength λ ₄ , and zone Z is used. By assigning the wavelength λ ₄ to ₃ and making the total 2 wavelengths, it is possible to cope with the shortage of the number of channels. Further, since the required extinction ratio of the electric stage is 80 dB, the extinction ratio of the optical stage needs to be 40 dB.
The output of the cross output ports of 2, 31 is 40 dB or more, and is applicable.

(Fifth Embodiment) FIG. 9 is a schematic configuration diagram of a mobile communication system 71 which is another example to which the wavelength division multiplex transmission system 51 of the third embodiment is applied. The mobile communication system 71 is different from the mobile communication system 61 described above in that one optical fiber cable 6 is provided in each of the _three zones Z _{1 to} Z ₃ and three wavelength selectors 11 and 11 are provided. ，
Are concentrated on the NTT (center) 72, and the directional coupler 7
It is a point that is connected by 3. In the mobile communication system 71, like the mobile communication system 61, allocation of wavelengths the wavelength lambda ₁ to [lambda] ₃ are assigned to each zone Z ₁ to Z _3.

Also in this mobile communication system 71,
The same effect as that of the mobile communication system 61 can be obtained. For example, with respect to the zone Z ₃ to the moving body is rapidly increased, it is possible to assign a wavelength lambda ₄ to Z ₃ by operating the wavelength selector zone Z _3. In this case, NTT
Since it is controlled by the (center) 72, there is an excellent effect that the reliability is high as compared with the remote control.

It should be noted that N in the mobile communication systems 61 and 71
Needless to say, it is possible to cope with the shortage of the number of channels by designing N + α (α: the number of margin wavelengths) wavelengths for the zones.

[0038]

As described above, according to the first aspect of the present invention.
According to the wavelength selector described, a Mach-Zehnder optical interference type wavelength demultiplexer, a plurality of thermo-optical effect type optical switches connected to each output port of this wavelength demultiplexer, and each of these optical switches In a wavelength selector comprising a Mach-Zehnder optical interference type wavelength multiplexer connected to the output port, the output port of the optical switch is a cross port with respect to the input port, and thus high extinction The ratio can be obtained.

According to the wavelength selector of the second aspect, in the wavelength selector of the first aspect, the plurality of optical switches set at least a phase difference in optical path length between the directional couplers to zero. , An optical switch that operates so as to output from the cross port when a voltage is not applied to the thin film heater for changing the phase and not to output from the cross port when a voltage is applied, and the position of the optical path length between the directional couplers. Phase difference is π
And an optical switch that operates so as not to output from the cross port when a voltage is not applied to the thin film heater for changing the phase and to output from the cross port when a voltage is applied. Because I decided
The wavelength selector can be configured so that there is no voltage when the operating state of these optical switches is always in use, and therefore reliability can be improved and power consumption can be reduced. it can.

According to the wavelength selector of claim 3, in the wavelength selector of claim 1 or 2, the wavelength demultiplexer, the optical switch and the wavelength multiplexer are integrated on a semiconductor substrate. As a result, downsizing, high reliability, and power consumption can be reduced.

According to the wavelength selector of the fourth aspect, in the wavelength selector of the first, second or third aspect,
Since the asymmetrical optical branching device is provided on the input side of the wavelength demultiplexer, the incident light can be branched into a plurality of lights at a predetermined ratio.

As described above, it is possible to support an AM video transmission system (extinction ratio> 27 dB) and a mobile communication system (extinction ratio> 40 dB) that require a high extinction ratio, and it is highly reliable and consumes less power. It is possible to provide a wavelength selector which can configure a system having a small number and can be further downsized and economical.

[Brief description of drawings]

FIG. 1 is a schematic configuration diagram of a wavelength selector according to the present invention.

FIG. 2 is a configuration diagram of a TO type optical switch used in the wavelength selector of the present invention.

FIG. 3 is a diagram showing a relationship between applied power and transmittance of a thin film heater of a TO type optical switch.

FIG. 4 is a configuration diagram of another TO type optical switch of the present invention.

FIG. 5 is a diagram showing a relationship between an optical output level of a TO type optical switch and electric power applied to a thin film heater.

FIG. 6 is a schematic configuration diagram of an AM video transmission system to which the wavelength selector of the present invention is applied.

FIG. 7 is a schematic configuration diagram of a wavelength division multiplex transmission system to which the wavelength selector of the present invention is applied.

FIG. 8 is a schematic configuration diagram of a mobile communication system to which the wavelength selector of the present invention is applied.

FIG. 9 is a schematic configuration diagram of another mobile communication system to which the wavelength selector of the present invention is applied.

FIG. 10 is a configuration diagram of a conventional wavelength multiplexing component.

FIG. 11 is a schematic configuration diagram of a conventional optical switching device.

[Explanation of symbols]

11 Wavelength Selector 7 Wavelength Demultiplexer 9 Wavelength Multiplexer 12 TO Optical Switch 13 Wavelength Selection Controller 22 Substrate 23, 24 Waveguide 25, 26 Directional Coupler 27 Thin Film Heater 28 Input Port 29 Parallel Output Port 30 Cross output port 31 TO optical switch 41 AM video transmission system 42 AM video signal generator 43 Electric / optical (E / O) converter 44 Optical splitter 45 Optical / electrical (O / E) converter 51 Wavelength multiplex transmission system 52 asymmetrical optical branching device 61 mobile communication system 71 mobile communication system 72 NTT (center) 73 directional coupler 2 wavelength multiplexed signal Z area Z _{1 to} Z ₃ zone λ ₁ , λ ₂ , λ ₃ , λ ₄ wavelength

Claims (4)

[Claims] 1. A Mach-Zehnder optical interference type wavelength demultiplexer, a plurality of thermo-optical effect type optical switches connected to each output port of this wavelength demultiplexer, and each output port of these optical switches. And a Mach-Zehnder optical interference type wavelength multiplexer, wherein the output port of the optical switch is a cross port with respect to the input port. 2. The wavelength selector according to claim 1, wherein the plurality of optical switches have a phase difference of at least 0 between optical path lengths between directional couplers, and a voltage is applied to a thin film heater for changing the phase. An optical switch that operates so that it outputs from the cross port when not applied, and does not output from the cross port when voltage is applied, a thin film for changing the phase with the phase difference of the optical path length between the directional couplers being π A wavelength selector comprising: an optical switch that does not output from a cross port when a voltage is not applied to a heater and that operates from a cross port when a voltage is applied. 3. The wavelength selector according to claim 1 or 2, wherein the wavelength demultiplexer, the optical switch and the wavelength multiplexer are integrated on a semiconductor substrate. 4. The wavelength selector according to claim 1, 2, or 3, wherein an asymmetric optical branching device is provided on the input side of the wavelength demultiplexer.