JPH06265958A - Integrated optical device and optical communication network using this device - Google Patents

Abstract

PURPOSE:To provide an integrated optical coupler, a semiconductor conductor amplifier, and an optical communication network using these devices by integrating an optical device, especially, a normally open semiconductor optical switch to give the fail safe function to the semiconductor amplifier. CONSTITUTION:The waveguide type optical device where at least a first clad layer 11, a first core layer 12, a second clad layer 13, a third clad layer 14, a second core layer 15, and a fourth clad later 16 are laminated on a semiconductor substrate 10 is divided into plural areas 1, 3, and 3 in the guiding direction, and a refraction modulating layer 20 is provided between the second alas layer 13 and the third clad layer 14 in at least one of these areas, and a mechanism to charge the carrier into the first core layer 13 or the second core layer 15 is provided in each of these areas 1, 2, and 3. Further, the fail safe function is provided by which incident light is outputted as it is at the time of not charging the carrier.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an integrated optical device used for optical communication and the like, in particular an integrated optical coupler and a semiconductor optical amplifier, and an optical communication network using this device.

[0002]

2. Description of the Related Art Among optical devices used in optical communication, in particular, optical local area networks, the importance of optical amplifiers has increased rapidly in recent years. Optical amplifiers are roughly divided into fiber amplifiers and semiconductor amplifiers, and they are used properly depending on the application.

In the case of a semiconductor amplifier (hereinafter also referred to as LDA), since it has a structure equivalent to that of a semiconductor laser, it is a great advantage that it is excellent in integration. As an example in which LDA is mainly integrated, K. Y. "M by LIOU et al.
onolithically Integrated G
aInAsP / InP Optical Amplif
ier with Low Loss Y-brach
ing Waveguides and Monoto
ring Photodetector "(Confe
Rence on Laser and Electr
oOptics '90, lecture number CDF7). FIG. 14 is a schematic diagram of this.

On the InP substrate 800, an optical amplifier unit 801,
The Y branch section 802 and the PIN light receiving section 803 are integrated. The layer structure is such that an optical guide layer (wavelength 1.1 μm) is provided under the active layer (wavelength 1.3 μm), and the active layer is common to the optical amplifier section 801 and the light receiving section 803. The Y branch section 802 has a structure in which the active layer is removed, and the end surfaces of the optical amplifier section 801 and the light receiving section 803 are antireflection coated. It is characterized in that the waveguide loss and coupling loss of the waveguide of each part are extremely small, and that the Y branch part 802 can be branched in two directions and can be monitored by each.

[0005]

However, this configuration has a major drawback. That is, the signal light must be LDA
Therefore, if a problem occurs in the LDA, the signal light will be seriously damaged. The semiconductor optical amplifier has a higher carrier injection amount than LD and the probability of internal deterioration is considered to be higher than LD, and the fail-safe function against deterioration is indispensable. For that purpose, it is conceivable to provide a normal optical switch before and after the LDA. For example, in Japanese Examined Patent Publication No. 4-64044, an optical component such as a lens or a prism is externally used, but with this method, the optical component must be externally attached, which inevitably increases the size and raises the price. , The advantages of integration are lost. That is,
LDA's unique advantages are lost.

The present invention was devised in view of the above problems, and an object thereof is an integrated optical device, particularly norm.
It is an object to provide an integrated optical coupler and a semiconductor optical amplifier having a configuration in which an LDA has a fail-safe function by integrating an all-open semiconductor optical switch, and an optical communication network using this device. .

[0007]

The gist of the present invention is to provide at least a first cladding layer, a first core layer, a second cladding layer, a third cladding layer, a second core layer and a fourth core layer on a semiconductor substrate.
A waveguide type optical device having a structure in which clad layers are laminated, and is divided into a plurality of regions in the waveguide direction, and
At least one of the regions has a refractive index modulation layer between the second cladding layer and the third cladding layer,
The integrated optical device has a mechanism for injecting carriers into the first core layer or the second core layer in each of the plurality of regions.

Specifically, the refractive index modulation layer is formed of a grating, the structure of the first core layer and / or the second core layer is composed of a single quantum well or a plurality of quantum wells, and On the other hand, the first core layer and the second core layer may be a transparent medium or a gain medium.

Further, the gist of the present invention is that a semiconductor substrate is
At least a first conductivity type first clad layer, a first conductivity type first core layer, a first conductivity type second clad layer, a second core layer and a second conductivity type third clad layer are laminated. A conductive optical device having a plurality of regions, which are divided into a plurality of regions in the waveguide direction, and at least one region of the divided regions is periodically arranged in the second cladding layer, the third cladding layer, or both. An integrated optical device having a current confinement layer.

At this time, the periodic current confinement layer is made of a material having the same refractive index as that of the adjacent clad layer, and its conductivity type is different from that of the clad layer.
The structure of the first core layer, the second core layer, or both, is composed of a single or a plurality of quantum wells,
For the incident light, the first core layer and the second core layer may be transparent media or gain media.

Further, the gist of the present invention is that a semiconductor substrate is provided with
A waveguide type optical device having a double optical waveguide structure in which a first optical waveguide and a second optical waveguide are laminated, and the optical device is divided into a plurality of regions in the waveguide direction, and at least one of the regions is An integrated optical device comprising: a refractive index modulation unit that controls the light distribution of the double optical waveguide structure; and a unit that injects carriers in each of the plurality of regions.

Further, as a specific application, an optical communication network characterized in that the integrated optical device is arranged on a bus type optical transmission line having a plurality of terminal stations,
There is an optical communication network characterized in that the integrated optical device is arranged on a star type optical transmission line having a plurality of terminal stations.

[0013]

Operation An optical device having a structure in which two waveguides are close to each other is generally well known as a directional coupler. At this time, if the respective propagation constants are β ₁ and β ₂ , Δβ = β ₂
The power branching ratio is determined by −β _{1, the} waveguide spacing d, and the coupling length L, so that the functions of the coupler and the switch can be provided. Furthermore, by introducing a layer that modulates the propagation constant between the two waveguides, that is, a refractive index modulation layer (typically, there are two described below), the degree of freedom in design and the manufacturing allowance are increased. , Or a new function, for example, an optical filtering function can be added.

On the other hand, by injecting carriers into the core layer of the waveguide, not only can it be used as an optical amplifier or a semiconductor laser as a gain medium in a wavelength range determined by the material of the core, but the refractive index of the core layer is lowered. Therefore, the light intensity distribution can be changed.

At this time, when the carrier is injected into the core,
By setting the carrier density to be cyclically different,
The two effects (light amplification and light intensity distribution change) are performed simultaneously.
You can also be satisfied. For example, the first core layer and
And a second core layer to form a directional coupler, while
For example, when carriers are periodically injected only into the first core layer
think of. 1 x 10¹⁸ cm^-3When carrier injection
Folding rate is 10^-3Decrease in order (Casey and
Panish; Heterostructure L
asers (Academic Press, 19
78)). Therefore, carriers may be injected periodically.
Is equivalent to forming a variable index grating
Is.

Further, the directional coupler is formed by the first core layer and the second core layer (in this case, the variable refractive index grating is formed), while only the first core layer is formed, for example. You may inject a carrier.

In both of the above cases, assuming that the grating vector is K, the Bragg condition (phase matching condition) is β ₂ = β ₁ + K (1) Here, assuming that Δ = β ₂ − (β ₁ + K) (2), the power transfer rate η is η = 1 / (1+ (Δ / κ) ² ) · (sin β _c z) ² ·· (3) Here, κ is the coupling efficiency between the two waveguides, z is the coordinate in the traveling direction, and β _c = (κ ² + Δ ² ) ^1/2 (4).

From this, the maximum power transfer rate η _max is η _max = 1 / (1+ (Δ / κ) ² ) (5), and the maximum perfect coupling length L is L = π / 2β _c ·・ ・ ・ It can be expressed by (6).

When the variable refractive index grating is formed, the effective refractive indexes of the waveguides 1 and 2 are set to n ₁ and n _2.
Then, when carrier injection is performed at about 1 × 10 ¹⁸ cm ⁻³ , the refractive index decreases on the order of 10 ⁻³ . As a result, the propagation constant decreases and κ increases.

When carrier injection is performed only in the waveguide 1.
Of the propagation constant of the waveguide 1 and the coupling efficiency with the waveguide 2 of
_{1, inj}And κ_injThen β_{1, inj}= Β₁-Δβ₁Becomes (Δβ₁> 0), and at this time, Δ during carrier injection is Δ_injWhen expressed by
From equation (2) Δ_inj= Δ + Δβ₁ And the power transfer rate is η_intIs from equation (3)_int= 1 / (1+ (Δ / κ_inj+ Δβ_{1, inj}/ Κ_inj)²) ・ (Sin β_{c, inj}z) ² Becomes

Therefore, since κ rises during carrier injection, >> 1 ... When carrier is not injected Δ / κ: (7) << 1 ... When carrier is injected As described above, the layer configuration can be set. In this way, it is possible to prevent η _int from increasing during carrier injection and power transfer, and not injecting power.

At this time, if there is no grating, κ
<< 1 so Δ / κ >> 1 ... always ... (8), and power transfer does not occur.

Particularly in the case of a high injection device such as an optical amplifier, the carrier injection effect of the refractive index is large, which is advantageous in design.

On the other hand, when carriers are injected periodically,
Since K = 0 when carrier is not injected, Δ _c = β ₂ −β _{1 is} not injected Δ _inj = β _{2, inj} − (β _{1, inj} + K) When injected = Δ _c −K.

By selecting κ when carrier is not injected as κ << 1, >> 1 ... When carrier is not injected Δ / κ: (7 ') << 1 ... When carrier is injected In this way, it is possible to prevent power transfer during carrier injection and power transfer during non-injection.

When there is no periodic current constriction layer,
The layer structure can be set so that Δ / κ >> 1 (8 ') is always maintained, and power transfer can be prevented.

Particularly in the case of a high injection device such as LDA, the carrier injection effect of the refractive index is large, which is advantageous in design.

Since the refractive index varies depending on the amount of injected carriers, the effective grating pitch changes. As a result, a filtering effect appears, but the filter band can be set to be wide or narrow according to the purpose by controlling the grating shape, and therefore it may be designed according to the case.

[0029]

First Embodiment FIG. 1 is a sectional view of the first embodiment of the present invention. Three regions are connected in series with respect to the traveling direction of light. Regions 1 and 3 are coupler regions,
The area 2 is a gain area or an optical amplification section. The layer structure was designed so that the expression (7) is satisfied in the areas 1 and 3 and the expression (8) is satisfied in the area 2.

For example, in FIG. 1, 10 is n-type Ga.
As substrate, 11 is an n-type first clad layer (Al _0.5 Ga _0.5
As, thickness 1.5 μm), 12 is the n-type first core layer (Al
_0.08 Ga _0.92 As, thickness 0.1 μm), 13 is n-type second
Clad layer (Al _0.5 Ga _0.5 As, thickness 0.5 μm),
14 is an n-type third cladding layer (Al _0.3 Ga _0.7 As, thickness 0.5 μm), and 15 is an undoped second core layer (Al _0.08
Ga _0.92 As, thickness 0.05 μm), 16 is a p-type fourth cladding layer (Al _0.5 Ga _0.5 As, thickness 1.5 μm), 1
7 is a contact layer (GaAs). 18 and 19
Is a positive electrode and a negative electrode, and 20 is a grating for modulating the refractive index. In the case of this example, the wavelength of the guided light was 860 nm, and the grating 20 was set to a sine curve with a pitch of 8.5 μm and a depth of 1.2 nm.

The device lengths of the regions 1 and 3 are set to the complete coupling length (500 μm in this embodiment) determined by the equation (4), and the device length of the region 2 (amplification section) is set to 600 μm. An antireflection (AR) coat 22 is applied to the input / output end faces. Reference numeral 21 is a spherical fiber.

The operation principle will be described with reference to FIG.
For example, consider a case where light having a wavelength of 860 nm is guided only to the first core layer 12.

1) When carriers are not injected into the entire region In FIG. 2, since the refractive index does not change, the light 26 input to the optical waveguide 25 does not couple with the waveguide mode of the second waveguide 24 at all. Therefore, it passes through the regions 2 and 3 and is output to the outside.

2) When carriers are injected into the entire region In FIG. 3, the light 31 guided in the first waveguide 25 is
While being modulated by the grating 20, the second
Coupling with the waveguide 24. Since the transfer rate is set to 100% with respect to the injected carrier density, when guided by the complete coupling length, it moves to the waveguide 24 with the transfer rate of 100% (the electric field distribution is shown by 32). Since the region 2 is the gain region, only the optical amplification is performed and the light intensity is increased (the electric field distribution is indicated by 33). Next, in the region 3 where the guided light 34 travels, as in the region 1, the waveguide 24
To the waveguide 25 and is output to the outside through the non-reflection end face 22. In region 2, regardless of carrier injection,
Since there is no coupling, the carrier injection amount and device length can be selected in order to achieve desired optical amplification.

[0035]

Second Embodiment Although the core 15 of the optical amplifier section is made of bulk AlGaAs in the first embodiment, a quantum well layer (QW) may be used. FIG. 6 shows the Al content of each layer as an example of the layer structure in this case. The second core layer is made of Al _0.2 Ga _0.8 As
The multiple quantum well structure 15a is composed of five pairs of (barrier layer) and GaAs (well layer). As a result, the gain spectrum can be made narrower than that in the first embodiment, and the magnitude of the gain can be increased. FIG. 11 shows a bulk gain spectrum 701 and a multiple quantum well gain spectrum 702 when carrier injection levels are made equal.
Is a schematic representation.

[0036]

Third Embodiment FIG. 5 is a sectional view of a third embodiment of the present invention. Similarly, three regions are connected in series with respect to the traveling direction of light. Regions 1 and 3 are optical couplers, and region 2 is an optical amplifier. The layer structure was designed so that the expression (7 ′) is satisfied in the areas 1 and 3 and the expression (8 ′) is satisfied in the area 2.

For example, in FIG. 5, 100 is an n-type G
aAs substrate, 101 is an n-type first cladding layer (Al _0.5 G
a _0.5 As, thickness 1.5 μm), 102 is an n-type first core layer (Al _0.08 Ga _0.92 As, thickness 0.1 μm), 103
Is an n-type second cladding layer (Al _0.5 Ga _0.5 As, thickness 0.
5 μm), 104 is an undoped second core layer (Al _0.08 G
a _0.92 As, thickness 0.05 μm), 105 is a p-type third cladding layer (Al _0.5 Ga _0.5 As, thickness 1.5 μm), 1
Reference numeral 06 is a contact layer (GaAs). 107 and 108 are a positive electrode and a negative electrode, and 109 is a periodic current confinement layer for modulating the refractive index. In the case of this example, the wavelength of the guided light was 860 nm, and the grating of the periodic current confinement layer 109 was set to a rectangular shape with a pitch of 8.5 μm and a duty of 50%.

The device lengths of the regions 1 and 3 are set to the complete coupling length (500 μm in this embodiment) determined by the equation (4), and the device length of the region 2 (amplification section) is set to 600 μm. Further, on the input / output end face facing the spherical optical fiber 110,
An antireflection (AR) coat 111 is applied.

Next, the manufacturing method of the third embodiment will be briefly described.

For example, an ordinary metal organic chemical vapor deposition method (M
OCVD method) and molecular beam epitaxial growth method (MBE)
(100) n-type GaAs substrate 10
0 to grow from the first cladding layer 101 to the second core layer 104. After growing the second core layer 104, p-type Al
_0.5 Ga _0.5 As layer (thickness 0.3 μm, carrier concentration p ~
3 × 10 ¹⁷ cm ⁻³ ), an n-type Al _0.5 Ga _0.5 As layer (thickness 0.5 μm, carrier concentration n˜3 × 10 ¹⁷ cm ⁻³ ), and then with a pitch of 8.5 μm as described above. The grating pattern has a depth of p-type Al _0.5 Ga _0.5 As
Etch to reach layer. After this, M continued
P-type Al _0.5 Ga _0.5 As layer (thickness 0.7μ
m, carrier concentration p˜3 × 10 ¹⁷ cm ⁻³ ).

The carrier concentration is set to about 3 × 10 ¹⁷ cm ^-3 in order to prevent a difference in refractive index in this region when carriers are not injected. As a result, the periodic current confinement layer 109 is produced. After this, the contact layer 106
To grow.

This embodiment is completed by forming an embedded structure or the like and forming electrodes 107 and 108 for controlling the transverse mode. FIG. 8 is a schematic view of the cross section of FIG.
In the figure, 401 is an Al _0.5 Ga _0.5 As high resistance buried layer. The structure for controlling the transverse mode is the same for the other embodiments.

Next, the operating principle of the third embodiment will be described with reference to FIG. For example, consider a case where light having a wavelength of 860 nm is guided only to the first core layer 102.

1) When carriers are not injected into the entire region In FIG. 6, since there is no change in the refractive index in the vicinity of the periodic current confinement layer 109 as described above, the light 201 input to the optical waveguide 205 is transmitted through the waveguide 204. It does not couple with the guided mode at all. Therefore, it passes through the regions 2 and 3 and is output to the outside (fail safe function).

2) When carriers are independently injected into the entire region The carriers injected from the positive electrode 107 are modulated in carrier distribution by the periodic current confinement layer 109, and carrier distribution is generated in the second core layer 104. , An equivalent refractive index distribution corresponding to this is formed.

Therefore, the light 30 guided to the waveguide 205 is
1 is coupled to the waveguide 204 by the periodic current confinement layer 109, as shown in FIG. Since the transfer rate is set to 100% with respect to the injected carrier density, when guided by the complete coupling length, it moves to the waveguide 204 with the transfer rate of 100% (the electric field distribution is shown by 302). The carrier that has passed through the second core layer 104 is the first core layer 102.
However, since the carrier diffusion effect and the carrier injection efficiency are low (since there is no pn junction in the first core layer 102), the refractive index is not modulated in the first core layer 102.

Since the region 2 is the gain region, only the optical amplification is performed and the light intensity becomes large (the electric field distribution is 303
). Next, in the region 3 where the guided light 304 travels, like the region 1, it transits from the waveguide 204 to the waveguide 205 and is output to the outside via the non-reflection end face 111. Since the region 2 does not couple regardless of carrier injection, the carrier injection amount and device length can be selected for desired optical amplification.

Although the n-type substrate is used in this embodiment, it may be advantageous to use the p-type substrate because the diffusion length varies depending on the carrier.

[0049]

Fourth Embodiment FIG. 9 is a schematic view of the fourth embodiment of the present invention. The periodic current confinement layer 109 ′ is the second cladding layer 103.
It is different from that of the third embodiment in that it is set in the box.

As a result, 1) the carrier distribution in the second core layer 104 at the time of carrier injection is the third even if the same grating pattern is used.
Different from the example, that is, the effective grating is different, 2) Inducing carrier distribution in the first core layer 102 depending on the position of the periodic current confinement layer 109 ', and 3) Regrowing in manufacturing. Third to form gain layer 104
As a result, it requires higher manufacturing technology than the embodiment.

By actively utilizing 2), the first core layer 102
Although the coupling can be increased by using as a gain medium, it may become a loss medium at the time of non-carrier injection. The operating principle is the same as that of the third embodiment.

[0052]

Fifth Embodiment In the third and fourth embodiments, bulk AlGaAs is used for the core layer 104 of the optical amplifier section, but a quantum well layer (QW) may be used. FIG. 10 shows the Al content of each layer as an example of the layer structure in this case. The second core layer is made of Al _0.2
The multiple quantum well structure 104a is composed of five pairs of Ga _0.8 As (barrier layer) and GaAs (well layer). As a result, the gain spectrum can be narrowed in band as compared with the third and fourth embodiments, and the magnitude of the gain can be increased. FIG. 11 schematically shows a bulk gain spectrum 701 and a multiple quantum well gain spectrum 702 when carrier injection levels are made equal.

By using a strained quantum well layer as the second core layer, it is possible to give equal gains to TE mode and TM mode (polarization independent LDA).

Next, an embodiment in which the device of the present invention is applied to an optical communication network will be described. In an optical communication network having a bus type, a star type, or a loop type as a transmission path form, when branching light to extract information, an optical amplifier according to the branching method and the number of branches is required.

[0055]

[Embodiment 6] FIG. 12 shows an application example in which the apparatus of the present invention is used as an optical booster amplifier. 400 is a bus line, 401 and 402 are optical repeaters, and 403-406.
Are optical nodes, and 407 to 410 are active optical switches. Optical repeaters 401 and 402 include the device of the present invention and are used to compensate for the power lost at each branch. Normally, the optical repeaters 401 and 402 and the optical switches 407 to 410 are interlocked with each other, and the optical repeater 401 or 402 performs amplification according to the number of branches, and when amplification is being performed, the switch is always open to the node side. There is.

When a trouble occurs in the optical amplifier for some reason, the power supply to the optical amplifier is turned off,
The active optical switch is also closed, and the optical signal on the bus line 400 passes without loss. That is, the fail safe function works.

[0057]

[Embodiment 7] FIG. 13 shows a device of the present invention including a booster amplifier +
It is an application example when it is used as a switch. Reference numeral 500 is an optical transmission line, 501 is an optical amplifier / optical switch including the device of this embodiment, 502 is a star type optical switch, and 503 to 50.
Reference numeral 7 is an optical node.

The function as a booster amplifier is the same as that of the sixth embodiment. When each terminal transmits, it cuts off the current of the optical amplifier / optical switch 501, and becomes a mere transmission device. Therefore, for example, a ping-pong communication network that alternately performs transmission and reception can be easily set up.

[0059]

The effects of the present invention are as follows.

1) Since the optical switch, the optical amplifier, the optical modulator, and the optical merging / branching device can be monolithically integrated, the device can be made compact and have high functionality. 2) Fail-safe is automatically performed when an active device such as an optical amplifier fails. 3) Easy integration with other devices.

[Brief description of drawings]

FIG. 1 is a schematic cross-sectional view of a first embodiment of the device of the present invention.

FIG. 2 is a schematic diagram illustrating the operation principle of the first embodiment.

FIG. 3 is a schematic diagram illustrating the operation principle of the first embodiment.

FIG. 4 is a view for explaining the layer structure of a second embodiment of the device of the present invention.

FIG. 5 is a schematic cross-sectional view of a third embodiment of the device of the present invention.

FIG. 6 is a schematic diagram illustrating the operating principle of the third embodiment.

FIG. 7 is a schematic diagram illustrating the operating principle of the third embodiment.

FIG. 8 is a cross sectional view of the third embodiment.

FIG. 9 is a schematic cross-sectional view of a fourth embodiment of the device of the present invention.

FIG. 10 is a view for explaining the layer structure of a fifth embodiment of the device of the present invention.

FIG. 11 is a schematic diagram of gain spectra of the second and fifth embodiments.

FIG. 12 is a diagram showing an embodiment of an optical communication system to which the device of the present invention is applied.

FIG. 13 is a diagram showing an embodiment of an optical communication system to which the device of the present invention is applied.

FIG. 14 is a perspective view showing a conventional example.

[Explanation of symbols]

 10, 100 substrate 11, 101 first clad layer 12, 102 first core layer 13, 103, 103 'second clad layer 14, 105 third clad layer 15, 15a, 104, 104a second core layer 16 fourth clad Layer 17, 106 Contact layer 18, 107 Positive electrode 19, 108 Negative electrode 20 Grating 21, 110 Precursor optical fiber 22, 111 Antireflection film 24, 25, 204, 205 Optical waveguide 109, 109 'Periodic current constriction layer 350 High resistance buried layer 400 Optical bus line 401, 402 Optical repeater 403-406, 503-507 Optical node 407-410 Active optical switch 500 Optical transmission line 501 Optical amplifier / optical switch 502 Star coupler

Claims (15)

[Claims] 1. A semiconductor substrate on which at least a first cladding layer, a first core layer, a second cladding layer, a third cladding layer,
A waveguide type optical device having a double optical waveguide structure in which a second core layer and a fourth clad layer are laminated, which is divided into a plurality of regions in the waveguide direction and at least one region of the regions is divided into a plurality of regions. A refractive index modulation layer is provided between the second cladding layer and the third cladding layer, and means for injecting carriers into the first core layer or the second core layer in each of the plurality of regions is provided. Integrated optical device. 2. The integrated optical device according to claim 1, wherein the refractive index modulation layer is formed of a grating. 3. The integrated optical device according to claim 1, wherein the structure of the first core layer, the second core layer, or both of them comprises a single quantum well or a plurality of quantum wells. 4. The integrated optical device according to claim 1, wherein the first core layer is a transparent medium for incident light. 5. The integrated optical device according to claim 1, wherein the second core layer is a gain medium for incident light. 6. The integrated optical device according to claim 1 is arranged on a bus type optical transmission line having a plurality of terminal stations, and when a carrier is not injected, an incident light is output as it is. An optical communication network characterized by not causing damage. 7. The integrated optical device according to claim 1 is arranged on a star type optical transmission line having a plurality of terminal stations, and when a carrier is not injected, an incident light is output as it is. An optical communication network characterized by not causing damage. 8. A semiconductor substrate having at least a first conductivity type first cladding layer, a first conductivity type first core layer, a first conductivity type second cladding layer, a second core layer and a second conductivity type. Is a waveguide type optical device having a double optical waveguide structure in which a third clad layer is laminated, and is divided into a plurality of regions in the waveguide direction, and at least one region of the divided regions has the second An integrated optical device having a periodic refractive index modulation layer in the cladding layer, the third cladding layer, or both, and controlling the light distribution of the double waveguide by the periodic refractive index modulation layer. device. 9. The periodic refractive index modulation layer is made of a material having the same refractive index as that of the cladding layer adjacent to the periodic refractive index modulation layer, and the periodicity is the same as the region of the conductivity type different from that of the cladding layer. 9. The integrated optical device according to claim 8, further comprising means for independently injecting carriers into the plurality of regions. 10. The integrated optical device according to claim 8, wherein the structure of the first core layer, the second core layer, or both comprises a single quantum well or a plurality of quantum wells. 11. The integrated optical device according to claim 8, wherein the first core layer is a transparent medium for incident light. 12. The integrated optical device according to claim 8, wherein the second core layer is a gain medium for incident light. 13. The integrated optical device according to claim 8 is arranged on a bus type optical transmission line having a plurality of terminal stations, and when a carrier is not injected, a fail-safe function in which incident light is output as it is will hinder the network. An optical communication network characterized by the fact that it does not cause trouble. 14. The integrated optical device according to claim 8 is arranged on a star type optical transmission line having a plurality of terminal stations, and when a carrier is not injected, a fail-safe function of outputting incident light as it is causes a trouble to a network. Optical communication network characterized by not causing 15. A first optical waveguide and a second optical waveguide on a semiconductor substrate.
A waveguide type optical device having a double optical waveguide structure in which optical waveguides are stacked, wherein the optical device is divided into a plurality of regions in the waveguide direction, and at least one region of the regions is the double optical waveguide structure. And a means for injecting a carrier into each of the plurality of regions, the integrated optical device comprising: