JPH02232631A - Waveguide type optical switch - Google Patents

Abstract

PURPOSE:To obtain the waveguide type optical switch scarcely having wavelength dependency by using a Mach-Zehnder optical interferometer circuit type 3dB optical coupler, which is constituted by coupling two directional couplers by optical waveguides with slightly different length, as an element, and constituting a circuit type optical switch with phase shifters. CONSTITUTION:Two 3dB optical couplers as elements of the Mach-Zehnder type optical switch are constituted in the configuration of a Mach-Zehnder optical interferometer circuit and the optical path difference of the circuit is set a little bit shorter (nearly 1mum) than the short-wavelength end of an in-use wavelength range. Namely, the 3dB optical couplers 22 and 23 themselves are constituted by coupling the two directional couplers 22a and 22b, and 23a and 23b each by two optical waveguides 22c and 22d, and 23c and 23d each, and such a coupled waveguide is supplied with an optical path length difference of nearly 1mum; and those two 3dB optical couplers 22 and 23 are coupled by two optical waveguides 24 and 25 equipped with phase shifters to obtain desired optical switch constitution on the whole. Consequently, the waveguide type optical switch which operates while scarcely having wavelength dependency in a desired wavelength of, for example, 1.3 - 1.44mum.

Description

[Detailed Description of the Invention] [Industrial Field of Application] The invention relates to a waveguide type optical switch that is commonly used in the field of optical communication, etc., and more specifically, it has less wavelength dependence and a wide range of applications. This paper concerns a waveguide optical switch that can simultaneously switch signal light in a wavelength range. (Prior technology) In order to further spread optical fiber communication, in addition to improving the performance and lowering the cost of optical fibers and receiving/emitting elements, optical branching couplers, optical multiplexers/demultiplexers, and optical switches are required. We have reached a stage where the development of various optical circuit components such as these is essential. Among these, optical switches are expected to play an important role in the near future, as they can freely switch optical fiber lines according to demand and provide detours in the event of a line failure. Conventionally, 1) bulk type and 2) waveguide type have been proposed as configurations of optical switches, but each has its own problems. The bulk type is assembled from components such as movable prisms and lenses, and although it has the advantage of less wavelength dependence and relatively low loss, the assembly and adjustment process is complicated, making it unsuitable for mass production and being expensive. It has shortcomings and has not become widely popular. The waveguide type is based on an optical waveguide on a flat substrate, and utilizes photolithography and microfabrication technology to mass produce so-called integrated optical switches, and is a future type of optical switch format. It is expected that , FIG. 7 is a plan view showing an example of the configuration of a conventional waveguide type optical switch. Here, the 3 dB optical couplers 2 and 3 formed on the substrate 1 are connected to two adjacent optical waveguides 4 and 5.
3 dB optical couplers 2 and 3 are connected to form a directional coupler, and the ρ coupling rate is set to be 50% (% of the complete coupling length) at the signal light wavelength.
The optical path lengths of the wooden optical waveguides 4 and 5 are set to be the same (symmetrical) when the phase shifters 4a and 5a disposed in the middle of these two optical waveguides are not operated. The signal light input from the input port 1a is emitted from the output port 2b in the above state, and is not emitted from the output port lb. However, l8 between the optical waveguides 4 and 5
When at least one of the phase shifters 4a and 5a is operated so that an optical path length difference in the vicinity of % wavelength corresponding to 0° (π radian) optical phase is generated, the signal light is shifted to the output port 1b.
The light is then switched to emit and emit light, achieving operation as an optical switch. This type of waveguide optical switch is
Also called the Matsuha-Zehnder optical interferometer circuit type, the switching effect can be achieved using a relatively simple phase shifter, so configurations have been attempted in various optical waveguide material systems including glass optical waveguides. There were problems like.

(Problems to be Solved by the Invention) FIG. 8 is a wavelength characteristic diagram showing the coupling rate from the input port la to the output port 2b of the optical switch designed and manufactured for a 1.3μ1 wavelength. Curve (a) shows phase shifter 4
This is the coupling characteristic when a and 5a are off, and curve (b)
is the coupling characteristic when either one of the phase shifters is on. Curve (C) is for reference the component 3d
It shows the coupling rate wavelength characteristics of the B-end coupler.

When one phase shifter is on (curve (b)), 1
．． In a relatively wide wavelength range of about ±0.2 μl centered on 3 μI, the (la → 2b) coupling rate is almost zero (5% or less).
Therefore, the ζ signal light can pass through a path of (1a-lb) with little wavelength dependence. In contrast, the off state (
In curve (a)), the binding rate (la → 2b) of gO% or more is limited to a narrow region of about 1.3μ ± 0.1μ; for example, at a wavelength of 1.55μ, the binding rate is 50%. There was a major problem in that the switching state was only halfway reached. In this way, the main reason for the large wavelength dependence of the conventional waveguide optical switch shown in FIG. 7 is the 3D
The B optical coupler (directional coupler) has a large wavelength dependence as shown in the curve (c) in Figure 8, and as shown in this curve (C), the coupling rate is 50% at a wavelength of 1.3 μm. When set so that, at a wavelength of 1.55 μl, it deviates significantly from 50% and no longer functions as a 3 dB optical coupler. When optical switches are used in fields such as optical fiber line switching, the line contains 1.3 μm wavelength light and 1.3 μm wavelength light.
. Since there are many situations in which 55μ1 wavelength light is passing through at the same time, the fact that the optical switch has such a large wavelength dependence has been a major practical problem.

SUMMARY OF THE INVENTION It is therefore an object of the present invention to solve the above-mentioned drawbacks and to provide a desired wavelength range, for example from 1.3μ to l. In the 55μ heavy range,
The object of this invention is to provide a waveguide-type Matsuhatsu Enda optical interferometer circuit-type optical switch that operates with little wavelength dependence. (Means for Solving the Problems) In the present invention, the two 3dB optical couplers themselves, which are the constituent elements of the Matsuha-Zehnder type optical switch, are configured in the form of a Matsuha-Zehnder optical interference needle circuit. The optical path length difference is slightly shorter than the short wavelength end of the wavelength range used (
Set to around 1μzen. In other words, the 3 dB optical coupler itself is constructed by connecting two directional couplers with two optical waveguides, giving these connected waveguides an optical path length difference of about 1 μm, and connecting these two 3 dB optical couplers. The optical coupler is connected with two optical waveguides equipped with a phase shifter to form the desired optical switch configuration as a whole. That is, the present invention provides a substrate, two optical waveguides disposed on the substrate, two 3dB optical coupling sections that couple the two optical waveguides at different positions of the optical waveguides, and two optical waveguides.
provided in the optical waveguide between two 3dB optical coupling parts,
In a waveguide type optical switch having an optical phase shifter section that finely adjusts the optical path length of the optical waveguide, each of the two 3 dB optical coupling sections is arranged on the substrate so as to couple the two optical waveguides at different positions of the optical waveguide. 2 directional couplers arranged in the
The optical path length difference of the wooden optical waveguides is set to be slightly smaller than the wavelength at the short wavelength end of the operating wavelength range, and It is characterized in that the optical waveguides are arranged on opposite sides between two 3 dB optical coupling parts.

Here, the operating wavelength range includes a 1.3μ1 to 1.55μ range, and the optical path length difference in the 3dB optical coupler is set to approximately 1μ, so that the wavelength dependence of the coupling rate of the 3dB optical coupler is 1.3
It is preferable that it be relaxed in the range of μI to 1.55μI. It is possible to configure the optical waveguide with a glass optical waveguide and configure the optical phase shifter with a thermo-optic effect phase shifter such as a thin film heater placed on the glass optical waveguide. (Function) Here, let Ll and L2 be the coupling lengths of the directional couplers constituting the Matsuha-Zehnder optical interferometer circuit for a 3 dB optical coupler, and let λ0 be the optical path length difference between the coupling waveguides. what if,
λ. In the case of 0.0 μl, the coupling rate characteristic of the 3 dB optical coupler is equivalent to that of a unidirectional coupler with the coupling length (Ll + + L2), and as the wavelength λ increases, the coupling rate characteristic of the 3 dB optical coupler becomes Similar to (C), it only increases monotonically from 0% to 100%, and this does not have any improvement effect. Next, the operation of the present invention in which the optical path length difference λ0 is set to around 1 μm will be explained. In this case, the wavelength λ is λ. If it is nearby, insert the optical path length. is the same as the wavelength of the signal light. ,
Despite the difference in optical path length between the directional couplers, the overall coupling rate of the 3 dB optical coupler of the Matsuha-Zehnder optical interferometer configuration is equivalent to that of the directional coupler of the coupling length (L1+L2). This is due to the principle of light wave interference, which states that when the optical path length difference in the Matsuha-Zehnder optical interferometer circuit is an integral multiple of the wavelength, it is indistinguishable from when the optical path length difference is zero. When the signal light wavelength exceeds λ0 and reaches 1.3 μl or even 1.55 μl, the optical path length difference gradually deviates from the relationship of an integral multiple of the wavelength (here, 1 times) and becomes a fractional multiple. That is, in this state, a significant phase difference appears between the two directional couplers constituting the 3 dB optical coupler in the form of a Matsuh-Zehnder optical interferometer, that is, a phase difference that deviates from an integral multiple of 2π. Due to this phase difference, the equivalent coupling length of the entire 3dB optical coupler is L
It deviates from the simple sum of 1 and 12 and gradually decreases. Here, a simple directional coupler (coupling length #t1+1
The optical path length is inserted so that the increase in the coupling rate in 2) is suppressed by the decrease in the equivalent coupling length due to the phase difference. If the coupling lengths Ll and L2 of each directional coupler are properly set, the 3dB optical coupler can be used in the desired wavelength range, for example, 1.3~
1. It is possible to maintain a coupling rate of around 50% in the 55 μm region, and this Matsuha-Zehnder optical interferometer type 3
By combining the dB optical couplers, it is possible to provide an optical switch that can operate simultaneously over the entire desired wavelength range.

(Example) Hereinafter, the present invention will be explained in detail with reference to Examples. In the following examples, a silica-based single mode optical waveguide formed on a silicon substrate is used as an optical waveguide, and a thermo-optic effect phase shifter mounted on the silica-based optical waveguide is used as a phase shifter. This is because this combination can provide an optical switch that has excellent connectivity with single-mode optical fibers and is polarization-independent; however, the present invention is not limited to these combinations. .

Embodiment 1 FIG. 1(A) shows the configuration of an optical switch designed to be able to operate simultaneously in the 1.3μl wavelength range and the 1.55μl wavelength range, as a first embodiment of the optical switch of the present invention. It is a plan view, and FIGS. 1 (B), (C) and ([1)
are enlarged cross-sectional views along lines ^A', 8B'' and CC' in FIG.
Optical couplers 24 and 25 are two quartz-based single mode optical waveguides formed on a silicon substrate 2l, and 24g and 25a are thermo-optic phase shifters provided on the optical waveguides 24 and 25, respectively. It is a phase vessel). Ia and lb are input ports, lb and 2b are output boats. In this embodiment, unlike the conventional example shown in FIG.
The 3 dB optical couplers 22 and 23 constitute 3 dB optical couplers z2 and 23, each configured in the form of a Matsuha-Zehnder optical interferometer circuit consisting of two directional couplers 22a and 22b and 23a and 23b. In each Matsuhatsu Enda optical interferometer circuit, an optical path length is inserted between the optical waveguides 22c and 22d and between 23c and 23d. is set. Here, the optical waveguide 22 with the longer optical path length is
c and 23d are placed on opposite sides between both optical couplers 22 and 23. As shown in FIGS. 1(B), (C), and (11), the optical waveguides 24 and 25 have core dimensions of 8 μm x 8 μm.
It is buried in a cladding layer 2Ib with a thickness of about 50μ disposed on the substrate l. The directional couplers 22a, 22b, 23a, 23b have two optical waveguides 22C (25) and 22d, as illustrated in the Nl diagram (B).
(24) are arranged in parallel over a length of several 100 microns with an interval of several microns. Figure 1 (
In the line segment BB” shown in C), the directional coupler 22
In order to set an optical path length difference of λG between a and 22b, the optical waveguide 24c (251) is connected to the optical waveguide 22 (1 (24
) the optical waveguide to be longer! 2C draws a gentle arc, and on the contrary, between the directional couplers 23a and 23b, the optical waveguide 23d (24) is made longer than the optical waveguide 23c (25). so that it draws an arc.

The optical path lengths of the two optical waveguides 24 and 25 connecting the 3 dB optical couplers 22 and 23 are set to be equal with an accuracy of 0.1 μm or less, and on the cladding Jl2ib, as shown in FIG. 0), thin film heaters (chromium metal film) are used as the thermo-optic effect phase shifters 24a and 25a.
is formed over a width of 50μ and a length of about 5Ill.

The radius of curvature of the optical waveguide arc portion in this example is 50 mm.
It was designed. Optical switch chip size is 40m+mX
It was 2.5ma+. The fabrication was performed by a known combination of glass film deposition technology using flame hydrolysis reaction and microfabrication technology using reactive ion etching.

In the present invention, the optical path length is inserted between the two directional couplers constituting the 3 dB forward couplers 22 and 23, respectively.

It is important to set it accurately. As a result of fabrication experiments and simulations, the setting error of λ0 was ±0.1 μ
It has been found that it is desirable to keep it within m, which is a range that can be easily achieved by using photolithography technology. Before explaining the characteristics of the optical switch of this example that was actually manufactured, the more detailed configuration and coupling characteristics of the 3 (1B optical couplers 22 and 23) will be explained. This is a coupling rate vs. wavelength characteristic diagram of the Matsuhatsu Enda optical interferometer circuit type 3 dB optical coupler 22, 23, which is a component of the wood invention.This coupling rate characteristic is as shown in FIG. 2 (8). optical waveguides 22c and 2
These are the results of actual measurements on a test 3dB optical coupler 22 configured by separately forming directional couplers 22a and 22b using 2d. The curve (a) shown in FIG.
This is the wavelength dependence of the coupling rate of b itself, which was realized by setting the coupling optical waveguide spacing to 4 μl and the effective length of the coupling part to L1=L2=0.31.

In this example, the directional couplers 22a and 22b are designed to be equivalent. Curve (b) represents the optical path length difference between the directional couplers 22a and 22b as λ. It shows the wavelength-dependent characteristic of the coupling rate of the optical coupler 22 as a whole when it is set to = 1.15 μm. What should be noted here is that the optical path length difference of λ0 = 1.15 μm is actually (1.15 μm), considering that the refractive index of the silica optical waveguide 24.25 is approximately 1.45. 1
5μm/1.45) = 0.79μm. Curve (C) is intentionally drawn. =θ. The wavelength dependence of the overall coupling rate of the two directional couplers 22a and 22b when set to θμ is shown, and the coupling characteristics in this case are determined by the coupling length (Ll+÷ It is comparable to the directional coupler of 2). Curve (b) shows that by appropriately setting the optical path length difference (λ = 1.15μffl), the coupling rate of the entire optical coupler 22 is approximately 50% over the wavelength range of 1.22 to 1.60μ4. This shows that the error is within a 10% error range. This fact indicates that in the optical coupler characteristics of the conventional optical switch shown in curve (c) of FIG.
4-1.37μml1: This is in contrast to the limited amount. FIG. 3 shows a 3dB optical coupler 22. As 23,・Second
Using an optical coupler with the characteristics shown in curve (b) of figure (A),
This figure shows the actual measurement results of the coupling ratio (la→2b) versus wavelength characteristics of the optical switch of the first embodiment of the present invention shown in FIG. 1, which was manufactured. The point to be kept in mind when configuring this optical switch is that inside the optical coupler 22, the optical waveguide 22c has a higher wavelength than the optical waveguide 22d.
. While the optical path length is longer by =1.15μ layer, conversely, inside the optical coupler 23, the optical waveguide 23d is set longer than the optical waveguide 23c by λo”1.15μ−. (This point will be discussed later in Mu
do). Curve (a) in FIG. 3 shows the wavelength-dependent characteristic of the optical coupling rate (la→2b) when the optical switch is off, that is, when the phase shifters 24a and 25a are off. In the conventional example, that is, in FIG. 8(a), the coupling rate is 9.
While the wavelength range in which the coupling rate is 0% or more is limited to 1.20 to 1,40μ, in Fig. 3(a), the coupling rate is 9.
The wavelength range where 0% or more occurs is as wide as 1.20 to 1.51μ, and includes not only the 1.3μ■ band but also the 1.55μG band. The curve ゜(b) in Figure $3 is the result of either one of the phase shifters (
A state (on state) in which a thin film heater) is energized and a 0.71 μm optical path length change is caused in one of the corresponding optical waveguides by utilizing the refractive index change due to the thermo-optic effect.
The graph shows the wavelength-dependent characteristics of the coupling rate (la-2b) at a thin film heater consumption of 9t power (approximately 0.5 watts). The wavelength range in which the coupling rate is less than 5% is from 1.24 to 70μ. In this state, the signal light passes through the path (ia-1b). In other words, the optical switch of this example has a state in which the coupling rate is 90% or more and a state in which the coupling rate is 5% in both the 1.3μl band and the 1.55μ1 band.
It is possible to switch between the following states at the same time, solving the drawbacks of conventional optical switches.

In the state of curve (b) in Figure 3, the (la-2b) coupling rate is about 2% at a wavelength of 1.3 μm, but by further reducing this coupling rate, almost 100% of the light is (la-2b) 1
b) In order to propagate along the path, the optical path length change due to the phase shifter is made to be transparent at a wavelength of 1.3 μl.
(1.3μm/2) = 0.65μ. This state corresponds to curve (C) in FIG. However, in this case, the coupling rate at the 1.55 μ overlapping wavelength is 6%.
At the cost of an increase in degree.

Curve (d) in Figure 3 shows the change in optical path length by (1.55μ//
2) = 0.775 p ta adjusted to 1.55
This is an example of prioritizing the μm wavelength band and sacrificing the 1.3 μm wavelength band. Curve (b) is an intermediate state between curve (c) and curve (d), that is, the optical path length difference is changed to (1.42 μm/2) − 0.71 μ so that the wavelength is 1.42 μ1.
It can be said that this corresponds to the case where the temperature is adjusted to be warm and the 1.3 μm band and the 1.55 μm band are moderately compatible. Of course, curves (b), (c) . (d) can be used depending on the purpose.

FIG. 4 (^) is an explanatory diagram of the coupling ratio versus wavelength characteristic of the 3 dB optical coupler 22 used to construct the optical switch of the second embodiment of the present invention. The difference from the optical coupler in the first embodiment is that in the second embodiment, the directional couplers 22a and 22
b are not equal, and as shown in FIG. 4 (8), the coupling length 1 of the directional coupler 22a is 0.61, which is twice the coupling length L2 of the directional coupler 22b, which is 0.3 mm. This point is set to . Also, the important optical path length difference between the directional couplers 22a and 22b is λ. = 0.95μ■. In FIG. 4(^), curve (a) is the coupling characteristic of the directional coupler 22a, curve}! i! (b) is the coupling characteristic of the directional coupler 22b, and curve (C) is the 3dB optical coupler 22b.
This shows the overall bonding properties. This 3dB optical coupler 22
The wavelength dependence of the coupling rate of is shown in FIG. 2 (A
) is more relaxed than curve (b), and the binding rate is 5.
The wavelength range of 0%±5% is l. +7 μl ~ 1.66 μl
It also extends to Figure 5 shows the 3dB optical coupler explained in Figure 4 (^).
FIG. 2 is an explanatory diagram of the wavelength characteristics of the optical switch of the second embodiment, which is arranged and manufactured in the same manner as in FIG. 1. What I would like to point out here is the internal configuration of the 3dB optical coupler 23, and the directional coupler 23a that constitutes the 3dB optical coupler 23.
The coupling length of the directional coupler 23b is selected to be the same as that of the directional coupler 22b, and the coupling length of the directional coupler 23b is selected to be the same as that of the directional coupler 22a. It should also be mentioned that the optical path length difference between the directional couplers 23a and 23b is set so that the optical waveguide 24 is longer. In FIG. 5, curve (8) is the coupling rate (la→2b) characteristic when the phase shifter of the optical switch is off.
Compared to the case of the first embodiment, the wavelength range where the coupling rate is 90% or more is further expanded to 1.11μ11 to 1.75μI. Curves (b), (c) and (d) are for one phase shifter, (b) 0.71 pva,
(C) 0.65 μm, (d) 0.775 pm This is the coupling rate characteristic when the optical switch is turned on with a change in optical path length difference of 0.75 μm, and almost the same state as in the first example is achieved. The operation as a wide wavelength range optical switch was confirmed.

Although the configuration and operation of the present invention have been described above with respect to two examples, the present invention is not limited to these configurations.

6(A) to ([11] are explanatory diagrams for considering modifications of the optical switch of the present invention. Here, as a directional coupler, the coupling lengths Ll and L2 used in the second embodiment are The optical path length difference between the directional couplers is λ = 0.9.
Assume that it is set to 5μ. FIG. 6(^) shows the configuration of the second embodiment itself, which exhibits the desired operation as the optical switch of the present invention. FIG. 6(B) is an example in which the optical path length difference within the 3 dB optical coupler 23 is set by lengthening the optical waveguide 23c side, contrary to the case of FIG. 6(A>). In such an arrangement, switching operation with little wavelength dependence cannot be obtained. This is an example in which the configuration was reversed to the case of (^), and this configuration was also inappropriate. In Fig. 6(D), both the 3dB optical coupler 22 and the 3dB optical coupler 23 are directionally coupled and 23
g, 23b each bond length Ll. Replace L2 and 3d
The optical path length differences in the B optical couplers 22 and 23 are shown in FIG.
This is an example in which the optical waveguides 22d and 23c are set longer than in the case of ^). In this case, the same proper operation as in the case of Fig. 6(A) was obtained. From the above experiments, it is inferred that in the optical switch of the present invention, the components need to be arranged so as to be optically approximately symmetrical with respect to the center point. The details must be determined by individual simulations according to wave coupling theory. In the above embodiment, the optical path length between the two 3 dB optical couplers was the same when the phase shifter was off, but in some cases, an optical path difference of about 0.71 μI was set in advance. It is also possible to reverse the optical path length difference by turning on a phase shifter, thereby reversing the on/off states in FIGS. 3 and 5. Such an optical switch is also applicable to the present invention. Please point out that it is included in the scope. The optical path switching function of the switch of the present invention has been described above, but the operation of the optical switch of the present invention is not necessarily limited to the switch function. The optical switch of the present invention can also be operated as a variable optical coupler.

The structure and operation of the present invention have been explained above using the case of a silica-based optical waveguide provided on a silicon substrate as an example.
As stated at the beginning, the present invention is not limited to these materials, but can be applied to other materials as long as the directional coupler and the phase shifter can be constructed, and are included within the scope of the present invention. For example, a LiNbO3-based optical waveguide can be used as the optical waveguide, and an electro-optic effect phase shifter can be used as the phase shifter. In addition, since the coupling length of each directional coupler mentioned in the above example varies slightly depending on the "habits" of the manufacturing process, it should be noted that the curve (a) in FIG. Song k in Figure 4 (^)! *It is important for the manufacturer to make appropriate adjustments so that a wavelength-dependent directional coupler similar to (al, (b)) can be obtained. (Effects of the Invention) As explained above, in the present invention, The Matsuha-Zehnder optical interferometer circuit-type 3dB optical coupler, which is constructed by connecting two directional couplers with optical waveguides of slightly different lengths, is used as a component, and together with the phase shifter, the Matsuha-Zehnder optical interferometer circuit-type optical switch is installed. By configuring this structure, it is possible to provide a waveguide type optical switch with extremely low wavelength dependence.The optical switch of the present invention can be used in many applications such as the construction of optical fiber communication networks in which signal lights of multiple wavelengths are multiplexed and propagated. It is expected that dogs will make a contribution.

[Brief explanation of the drawing]

FIG. 1(A) is a plan view showing the configuration of the first embodiment of the optical waveguide type optical switch of the present invention, and FIG. 1(B). (C) and (D) are cross-sectional views of each part, Figure 2 (8) is a coupling characteristic diagram of the 3 dB optical coupler that constitutes the switch according to the first embodiment of the present invention, and Figure 2 (B) is the 3 dB optical coupling. 3 is a coupling rate characteristic diagram of the optical switch according to the first embodiment of the present invention, and FIG.
A coupling characteristic diagram of a dB optical coupler, FIG. 4(B) is an explanatory diagram of the 3 dB optical coupler, N5 diagram is a coupling rate characteristic diagram of the optical switch of the second embodiment of the present invention, and FIG. 6 is a diagram of the optical switch of the present invention. FIG. 7 is a plan view showing a configuration example of a conventional waveguide type optical switch. FIG. 8 is a wavelength characteristic diagram of a conventional waveguide type optical switch. l... Substrate, 2.3... 3dB optical coupler, 4.5... Optical waveguide, 4a, 5a... Phase shifter, la, 2a, lb, 2b - Human output boat, 2l...・
Silicon substrate, 2lb...Quartz-based cladding layer, 22.23...Matsuha-Zehnder optical interferometer circuit configuration 3d
B optical coupler, 22a, 22b, 23a, 23b - directional coupler,
22c. 22d, 23c, 23d... optical waveguide, 24
．． 25...Quartz-based optical waveguide, 24a, 25a...Thermo-optic effect phase shifter (thin film heater). Patent applicant Nippon Telegraph and Telephone Corporation

Claims (1)

[Claims] 1) A substrate, two optical waveguides disposed on the substrate, and two 3dB optical coupling sections that couple the two optical waveguides at different positions of the optical waveguides, respectively. , the two 3dB
In a waveguide type optical switch having an optical phase shifter section that is provided in the optical waveguide between the optical coupling sections and finely adjusts the optical path length of the optical waveguide, each of the two 3 dB optical coupling sections is connected to the two 3 dB optical coupling sections. two directional couplers arranged on the substrate to couple the optical waveguides at different positions of the optical waveguides, respectively;
The optical path length difference between the two optical waveguides connecting the two directional couplers is set to be slightly smaller than the wavelength at the short wavelength end of the operating wavelength range, and each of the two 3 dB optical coupling parts A waveguide type optical switch characterized in that of the two optical waveguides, the optical waveguide having a longer optical path length is disposed on opposite sides between the two 3 dB optical coupling parts. 2) The operating wavelength range includes a 1.3 μm to 1.55 μm region, and the optical path length difference in the 3dS optical coupler is approximately 1.
2. The waveguide type optical switch according to claim 1, wherein the wavelength dependence of the coupling rate of the 3 dB optical coupler is relaxed in a range of 1.3 μm to 1.55 μm. 3) The optical waveguide is constituted by a glass optical waveguide, and the optical phase shifter is constituted by a thermo-optic effect phase shifter comprising a thin film heater disposed on the glass optical waveguide. The described waveguide optical switch.