JPH05232333A - Waveguide type optical multiplexer demultiplexer - Google Patents

Abstract

PURPOSE:To improve the transmission characteristics of the waveguide type optical multiplexer demultiplexer without spoiling its speediness. CONSTITUTION:The waveguide type optical multiplexer demultiplexer 10 includes a silicon substrate 11, a glass layer (not shown in figure) formed on the silicon substrate 11, a 1st optical waveguide 131 and a 2nd optical waveguide 132 which are formed in the glass layer, 1st-5th directional coupling parts 141-145 which are formed by putting the intermediate parts of the optical waveguides 131 and 132 put close to each other at five places, 1st-8th thin film heaters 151-158; and a 1st fundamental constitution circuit and a 2nd fundamental constitution circuit are arranged almost optically symmetrically about the center point (3rd directional coupling part 143) of the circuit.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a waveguide type optical multiplexer / demultiplexer, and more particularly to a waveguide type optical multiplexer / demultiplexer for multiplexing or demultiplexing two or more signal lights having different wavelengths used in the field of optical communication. It relates to a duplexer.

[0002]

2. Description of the Related Art In the field of optical communication, a technique for multiplexing and transmitting signal lights having different frequencies is important. That is, two or more signal lights having different frequencies, which have respectively propagated through different optical waveguides, are combined and converged into one optical waveguide, and two signals having different frequencies propagated through one optical waveguide. The optical multiplexer / demultiplexer for demultiplexing the above signal light and decomposing it into each optical waveguide for each frequency is a key component in the field of optical communication.

FIG. 8 is a plan view showing an example of a Mach-Zehnder optical interferometer type optical multiplexer / demultiplexer, which is one of typical conventional guided wave type optical multiplexer / demultiplexers.

Mach-Zehnder optical interferometer type optical multiplexer / demultiplexer 100
Is a flat substrate 101 and a first substrate formed on the flat substrate 101.
Optical waveguide 102a and second optical waveguide 102b, and a first directional coupling portion 103a and a second directional coupling portion 103b which are formed such that the intermediate portions of the respective optical waveguides 102a and 101b are close to each other at two locations. And a first thin film heater 108a formed above the first optical waveguide 102a between the first directional coupling portion 103a and the second directional coupling portion 103b, and the first directional coupling portion. The second thin film heater 108b is formed above the second optical waveguide 102b between the 103a and the second directional coupling portion 103b. Here, the first directional coupling portion 103a and the second directional coupling portion 103b.
And each function as a 3 dB coupler.

Mach-Zehnder optical interferometer type optical multiplexer / demultiplexer 100
Then, the first directional coupling portion 103a and the second directional coupling portion 10
The waveguide length L + ΔL of the second optical waveguide 102b between 3b and
Between the first directional coupling portion 103a and the second directional coupling portion 103b
The waveguide length difference is greater than the waveguide length L of the first optical waveguide 102a between
Since it is longer by ΔL, the second optical waveguide 102b is inserted.
Signal light of the first frequency f input from the input port 104b
P_through And the signal light P of the second frequency f + Δf_cross When
Signal light P multiplexed with_inIs the first directional coupling portion 103a or
And by passing through the second directional coupler 103b, etc.
The signal light P of the first frequency f is divided into power_through 
Is output from the output port 105b of the second optical waveguide 102b,
Signal light P of the second frequency f + Δf_cross Is the first optical waveguide
It is output from the output port 105a of the path 102a. Signal light P_inTo
Signal light P for_cross Light intensity transmission T_cross Frequency
An example of the dependency (transmission characteristic) is shown by the solid line in FIG.
Light P_inSignal light P for_through Light intensity transmission T
_through Fig. 9 shows an example of the frequency dependence (transmission characteristics) of
Each is indicated by a line. In this example, two light intensity transmittances T
_through, T_crossChanges sinusoidally with frequency
However, the interval of the period is 10 GHz. Therefore,
Use of Mach-Zehnder optical interferometer type optical multiplexer / demultiplexer 100
Thus, the first directional coupling portion 103a and the second directional coupling portion 103a
By using the waveguide length difference ΔL with 103b,
It is possible to demultiplex the signal light that generates

In general, in frequency multiplex communication, the signal is
Propagation is performed using sideband frequencies on both sides of the carrier frequency. Therefore, it is desirable that the transmission characteristics be constant in a constant frequency band centered on the carrier frequency. However, in the Mach-Zehnder interferometer type optical multiplexer / demultiplexer 100 shown in FIG. 8, since the two light intensity transmissivities T _through and T _cross change sinusoidally with respect to the frequency, they are constant over the entire sideband frequency region. There is a problem that the transmission characteristics cannot be provided, and the signal light P _through and the signal light P _cross are distorted.

A Mach-Zehnder optical interferometer type optical multiplexer / demultiplexer 200 shown in FIG. 10 has been proposed as one of the guided wave type optical multiplexer / demultiplexers capable of solving this problem.

Mach-Zehnder optical interferometer type optical multiplexer / demultiplexer 200
Is different from the Mach-Zehnder interferometer type optical multiplexer / demultiplexer 100 shown in FIG. 8 in the following points. (1) First directional coupling portion 203a and second directional coupling portion 20
The ring path 20 is provided on the lower side of the first optical waveguide 202a in FIG.
6 is provided, and the first optical waveguide 202a and the ring path 206 between the first directional coupling portion 203a and the second directional coupling portion 203b are brought close to each other, thereby The directional coupling portion 203c is formed. (2) The first thin film heater 208a is connected to the first directional coupling portion 20.
First optical waveguide 20 between 3a and second directional coupling portion 203b
Instead of being formed above 2a, the lower ring path 20 in the figure
It is formed above 6.

That is, the Mach-Zehnder interferometer type optical combiner
The duplexer 200 uses the ring path 20 to improve the transmission characteristics.
6 and the third directional coupling portion 203c as a ring resonator.
It is activated to give a periodic delay. In Figure 11,
Signal light P_inSignal light P for _cross Light intensity transmission T
_cross An example of the frequency dependence (transmission characteristic) of is shown. Figure 1
As shown in 1, the Mach-Zehnder optical interferometer type optical multiplexer / demultiplexer
At 200, the light intensity transmittance T_cross Is rectangular to frequency
And the transmission characteristics are improved.

[0010]

However, in the above-mentioned conventional Mach-Zehnder interferometer type optical multiplexer / demultiplexer 200, in order to improve the transmission characteristics by giving a periodic delay,
As a result of the signal light Pin input from the input port 204b of the second waveguide 202b staying _{in the} ring path 206 for a long time, the time response is significantly deteriorated, and there is a problem that it cannot be applied to the field of high-speed optical communication.

An object of the present invention is to provide a waveguide type optical multiplexer / demultiplexer capable of improving transmission characteristics without impairing high speed.

[0012]

A waveguide type optical multiplexer / demultiplexer according to the present invention includes a substrate and a first optical waveguide and a second optical waveguide formed on the substrate. The two signal lights that are incident from one of the second optical waveguides are demultiplexed, and one of the two signal lights is emitted from the one optical waveguide, and The other signal light of the two signal lights is emitted from the other optical waveguide of the first and second optical waveguides, and the signal light incident from the first optical waveguide and the signal light incident from the second optical waveguide are incident. In the waveguide type optical multiplexer / demultiplexer which combines the signal light with the optical signal and outputs the optical signal from either one of the first and second optical waveguides, the first optical waveguide and the second optical waveguide The first part, in which the middle part with the waveguide is formed in close proximity to each other at five positions, is formed in sequence. A fifth directional coupling portion is included, and between the first directional coupling portion and the second directional coupling portion, the second optical waveguide is closer to the first optical waveguide than the first optical waveguide. The first optical waveguide is longer than the second optical waveguide between the second directional coupling portion and the third directional coupling portion by a difference of 1 optical path length. The third optical path length is longer in the second optical waveguide than in the first optical waveguide between the third directional coupling portion and the fourth directional coupling portion by an optical path length difference. The difference is longer, and between the fourth directional coupling portion and the fifth directional coupling portion, the first optical waveguide is larger than the second optical waveguide by the fourth optical path length difference. Long, the first to fourth optical path length differences are equal or substantially equal, and the coupling rate of the first directional coupling section and the coupling rate of the fifth directional coupling section are Poetry substantially equal, the second and the coupling ratio of the directional coupler section and said fourth directional coupling portion coupling ratio is approximately equal or equal.

Here, between the first directional coupling portion and the second directional coupling portion, the first optical waveguide is longer than the second optical waveguide in the first optical path length. The difference is long,
Between the second directional coupling portion and the third directional coupling portion, the second optical waveguide is longer than the first optical waveguide by a second optical path length difference, and Between the third directional coupling portion and the fourth directional coupling portion, the first optical waveguide is longer than the second optical waveguide by a third optical path length difference, Between the directional coupling portion and the fifth directional coupling portion, the second optical waveguide is the first optical waveguide.
It may be longer than the optical waveguide by the fourth optical path length difference.

Further, instead of the third directional coupling portion, a sixth directional coupling portion and a third directional coupling portion each having a coupling rate of half the coupling rate of the third directional coupling portion. A seventh directional coupling section having a coupling rate that is half the coupling rate of the section, and between the sixth directional coupling section and the seventh directional coupling section, the first optical waveguide 73 The optical path length of _{1 and} the optical path length of the second optical waveguide may be equal or substantially equal.

Further, the first optical waveguide and the second optical waveguide are each composed of a quartz glass core embedded in a silica glass layer formed on a flat substrate. It may be a system single mode optical waveguide.

[0016]

In the waveguide type optical multiplexer / demultiplexer according to the present invention, the first to fifth directional couplings are formed in such a manner that the intermediate portions of the first optical waveguide and the second optical waveguide are arranged in close proximity to each other at five positions. Including parts,
As will be described later, the first basic constituent circuit and the second basic constituent circuit are arranged such that they are arranged substantially optically in point symmetry with respect to the center point of the circuit (the third directional coupling portion 14 ₃ ). By doing so, the frequency band in which the light intensity transmittance is “1” and the frequency band in which the light intensity transmittance is “0” can be flattened for the reason described later.

[0017]

Embodiments of the present invention will now be described with reference to the drawings.

FIG. 1 is a plan view showing a first embodiment of a waveguide type optical multiplexer / demultiplexer according to the present invention.

The waveguide type optical multiplexer / demultiplexer 10 has a silicon substrate 11 and a film thickness of 50 μm formed on the silicon substrate 11.
glass layer consisting of S _i O ₂ -based glass of about m (not shown)
When the first optical waveguide 13 ₁ and the second optical waveguide 13 ₂ formed on the glass layer, the optical waveguides 13 _1, 13 ₂
The first part of which the middle parts of the two are formed in close proximity to each other
To the fifth directional coupling portions 14 _{1 to} 14 ₅ and the first directional coupling portion 14 ₁ and the first directional coupling portion 14 ₂ between the first directional coupling portion 14 ₁ and the second directional coupling portion 14 ₂ .
And the first and second thin film heaters 15 ₁ and 15 ₂ formed above the glass layers and above the second optical waveguides 13 ₁ and 13 ₂ , respectively, and the second directional coupling portion 14 ₂ and Three
Third and fourth thin film heaters 15 ₃ and 15 formed above the glass layer and above the first and second optical waveguides 13 ₁ and 13 ₂ with the directional coupling portion 14 _{3 of
4} and the first and second optical waveguides 13 ₁ , 13 ₂ between the third directional coupling portion 14 ₃ and the fourth directional coupling portion 14 _4.
A fifth layer formed above the glass layer and on the glass layer, respectively.
And between the sixth thin film heaters 15 ₅ and 15 ₆ and the first and second optical waveguides 13 ₁ and 13 ₂ between the fourth directional coupling portion 14 ₄ and the fifth directional coupling portion 14 ₅ . 7th and 8th thin film heaters 15 ₇ and 15 ₈ formed above and on the glass layer, respectively.

Next, the optical waveguides 13 ₁ and 13 ₂ , the directional coupling portions 14 _{1 to} 14 ₅ and the thin film heaters 15 ₁ to 15 ₈ will be described in detail.

[0021] (1) optical waveguides 13 _1, 13 ₂ each of the first optical waveguide 13 ₁ and the second optical waveguide 13 _2, constructed from a core portion consisting of S _i O ₂ -GeO ₂ glass quartz It is a system single mode optical waveguide in which the core has a cross-sectional shape of about 8 μm square.

Further, first directional coupling portion 14 ₁ and the between the second directional coupler 14 _2, the second optical waveguide 13 ₂
Is shorter than the first optical waveguide 13 ₁ by the first waveguide length difference Δ.
It is long by L ₁ (= first optical path length difference), and is the first between the second directional coupling portion 14 ₂ and the third directional coupling portion 14 ₃ .
Of the optical waveguide 13 ₁ is longer than the second optical waveguide 13 ₂ by the second waveguide length difference ΔL ₂ (= the second optical path length difference),
Third directional coupling portion 14 ₃ and fourth directional coupling portion 14 ₄
Between the second optical waveguide 13 ₂ and the first optical waveguide 13 ₁ , the second optical waveguide 13 ₂ is longer than the first optical waveguide 13 ₁ by the third waveguide length difference ΔL ₃ (= the third optical path length difference), and the fourth directionality Between the coupling portion 14 ₄ and the fifth directional coupling portion 14 ₅ , the first optical waveguide 13 _{1 has} a fourth waveguide length difference ΔL more than the second optical waveguide 13 _2.
4 (= the fourth optical path length difference). here,
The first to fourth waveguide length differences ΔL _{1 to} ΔL ₄ are set to be equal or substantially equal to each other.

The waveguide length differences ΔL _{1 to} ΔL ₄ are
By appropriately selecting the value, optical multiplexing / demultiplexing in various frequency bands becomes possible.

(2) Each of the directional coupling portions 14 _{1 to} 14 ₅ The first to the fourth directional coupling portions 14 _{1 to} 14 ₅ connect the first optical waveguide 13 ₁ and the second optical waveguide 13 ₂ . They are arranged by being arranged in parallel with each other over a distance of several hundreds of μm while maintaining an interval of several μm.
The coupling ratio of the _first directional coupling portion 14 _{1 and} the coupling ratio of the fifth directional coupling portion 14 ₅ are set to be substantially equal to each other, and the coupling ratio of the second directional coupling portion 14 ₂ is set. Rate and fourth
It is set so as to be substantially equal to the coupling rate of the directional coupling section 14 ₄ .

[0025] (3) the thin-film heaters 15 _{1-15 8} of the first to eighth respective thin film heater 15 _{1-15 8,} the silica-based optical waveguide by utilizing the thermo-optic effect for fine tuning the optical path length difference It functions as a phase controller. In addition,
When the temperature of the waveguide type optical multiplexer / demultiplexer 10 itself can be stabilized by other means, the first to eighth thin film heaters 1
5 ₁ to 15 ₈ are unnecessary.

Next, the structure of the waveguide type optical multiplexer / demultiplexer 10 will be described with reference to FIGS.

The waveguide type optical multiplexer / demultiplexer 10 is equivalent to that shown in FIG.
As shown in FIG.₁ And the second basic
Configuration circuit 20₂ And are the center points of the circuit (the third directional coupling part).
14 ₃ ), So that they are arranged almost point-symmetrically with respect to
It is configured. Here, the first basic configuration circuit 20₁ When
Second basic configuration circuit 20₂ And three directions, respectively
Coupling part 34₁~ 34₃The asymmetric matrix as shown in Figure 3
Optically equivalent to the Bach-Zehnder interferometer type optical multiplexer / demultiplexer 30.
Therefore, the first basic configuration circuit 20₁And the second
Basic configuration circuit 20₂ Also as shown in Figure 4, respectively
Two asymmetric Mach-Zehnder optical interferometer type optical multiplexer / demultiplexers 40
It has a configuration in which it is optically arranged substantially in point symmetry.
Can be said.

Therefore, in the waveguide type optical multiplexer / demultiplexer 10 shown in FIG. 1, the asymmetric Mach-Zehnder optical interferometer type optical multiplexer / demultiplexer 40 shown in FIG. Since it can be said that it has a combined configuration,
The following relationship holds. (1) The first to fourth waveguide length differences ΔL _{1 to} ΔL ₄ are equal or almost equal to each other. (2) Assuming that the coupling ratio of the _first directional coupling portion 44 ₁ shown in FIG. 4 is s and the coupling ratio of the second directional coupling portion 44 ₂ is t, the first direction shown in FIG. The coupling ratio of the sexual coupling portion 14 ₁ is s, the coupling ratio of the second directional coupling portion 14 ₂ is 2t, the third
The directional coupling portion 44 _{3 has} a coupling ratio of 2 s, the fourth directional coupling portion 44 _{4 has} a coupling ratio of 2 t, and the fifth directional coupling portion 14 ₅
The coupling ratio of is s.

Generally, in an optical circuit having an optically point-symmetrical arrangement, the transmission characteristics of the entire circuit are determined by the circuit characteristics of the basic constituent circuit. The left end of the first optical waveguide 13 ₁ in FIG. 1 is the input port 16 for the signal light P _in , and the right end of the first optical waveguide 13 ₁ is the output port (hereinafter, referred to as “through port”). ) 17 ₁ and the second optical waveguide 1
An output port (hereinafter, referred to as a “cross-port”) 17 _{2 of} 3 ₂ in the figure is used as an output port 17 ₂ from the input port 16 of the _first basic constituent circuit 20 ₁ shown in FIG. 2 to the second optical waveguide 13 ₂ . Let T _{2 be} the light intensity transmittance of the waveguide-type optical multiplexer / demultiplexer 10 from the input port 16 to the cross-port 1
The light intensity transmittance T _cross to 7 ₂ is expressed as T _cross = 1- (1-2 × T ₂ ) ² (1). The following can be understood from the equation (1).

When T ₂ = 0, T _cross = 0 T ₂ = 1, T _cross = 0 T ₂ = 0.5, T _cross = 1 Also, when T ₂ ≈0.5, ( The value in parentheses on the right side of equation 1) is a value close to "0", but because the squared parentheses affect the light intensity transmittance T ₂ almost at a distance from "0.5". The value is close to "0". That is, because of this square term, the light intensity transmittance T ₂ is "0.
In the frequency band near 5 ", the waveguide type optical multiplexer / demultiplexer 10
The light intensity transmission T _cross from the entire input port 16 to the cross-port 17 ₂ is almost “1”. The waveguide type optical multiplexer / demultiplexer according to the present invention realizes flat characteristics by utilizing this principle.

FIGS. 5A, 5B and 5C respectively show
Asymmetric Mach-Zehnder optical interferometer type optical multiplexing / demultiplexing shown in FIG.
40, asymmetric Mach-Zehnder optical interferometer type shown in FIG.
Optical multiplexer / demultiplexer 30 and waveguide type optical multiplexer / demultiplexer shown in FIG.
Light intensity transmittance T at 10 _cross Shows the frequency dependence of
It is a graph. From this graph, we can see that
Karu (1) As shown in FIG. 5 (A), the asymmetric matrix shown in FIG.
In the Bach-Zehnder optical interferometer type optical multiplexer / demultiplexer 40,
Transient T_cross Changes sinusoidally with frequency,
Intensity transparency T_cross The minimum value of is about "0.5". (2) As shown in FIG. 5B, the asymmetric matrix shown in FIG.
In the Bach-Zehnder optical interferometer type optical multiplexer / demultiplexer 30, the optical intensity transmission is
Transient T_cross Is the light intensity transmission T_cross Becomes "1"
A flat area is obtained in the vicinity. This is the above formula (1)
An optical circuit having an optically point-symmetrical arrangement as described in 1.
Then T₂ Light intensity transmittance T when ≈0.5_cross Gaho
This is due to the property of becoming "1". In addition, the non-
Light intensity at the symmetric Mach-Zehnder interferometer type optical multiplexer / demultiplexer 30
Transparency T_cross The minimum value of is also about "0.5"
It (3) As shown in FIG. 5C, the waveguide type shown in FIG.
In the optical multiplexer / demultiplexer 10, the light intensity transmittance T_cross Is "0"
A flat region is obtained in the vicinity of and "1". This
This is an optical point symmetry, as explained in equation (1) above.
In an optical circuit having an arrangement, T₂ Transmits light intensity when = 1
Degree T_cross Becomes "0" and T₂ Light intensity when ≈0.5
Transparency T_cross This is due to the property that is almost "1".

Next, the waveguide type optical multiplexer / demultiplexer 1 shown in FIG.
An example of prototype 0 will be described.

In this prototype, a waveguide type optical multiplexer / demultiplexer 10 was prototyped by a combination of a known glass film deposition technique by flame hydrolysis reaction and a known fine processing technique by reactive ion etching. Since photolithography technology can be used in this fabrication method, the waveguide lengths of the first optical waveguide 13 ₁ and the second optical waveguide 13 ₂ can be fabricated with an accuracy of 0.1 μm or less.

FIG. 6 shows the entire waveguide type optical multiplexer / demultiplexer 10.
Force port 16 to through port 17 ₁ Light intensity transmission to
T_through And input port 16 to cross port 1
7₂Intensity T_cross Frequency-dependent measurement result of
Show the result.

In this measurement result, the light intensity transmittance T _through from the input port 16 to the through port 17 ₁ and the light intensity transmittance T from the input port 16 to the cross-port 17 ₂ are shown.
_The characteristics are slightly different from _{cros s} , but both are average 2G
A flat region is obtained in the frequency region of Hz.

The waveguide type optical multiplexer / demultiplexer 10 of this embodiment is used.
Then, the first directional coupling portion 14₁ And the second directional coupler
14₂ Between the second optical waveguide 13 and₂ Is the first
Optical waveguide 13₁ First waveguide length difference ΔL₁ Only long
The second directional coupling portion 14₂And the third directional coupler 1
Four₃ Between the first optical waveguide 13 and₁ Is the second light
Waveguide 13₂ Than the second waveguide length difference ΔL₂ Only long
Third directional coupling portion 14 ₃ And the fourth directional coupler 14_Four 
Between the second optical waveguide 13 and₂ Is the first optical waveguide
Road 13₁ Than the third waveguide length difference ΔL₃ Only long, 4th
Directional coupling portion 14_Four And the fifth directional coupler 14_Five With
In between, the first optical waveguide 13₁ Is the second optical waveguide 1
Three₂ Than the fourth waveguide length difference ΔL_Four Made it longer. Only
On the contrary, the first directional coupling portion 14₁ And the second direction
Joint part 14₂ Between the first optical waveguide 13 and₁ Is the first
2 optical waveguide 13₂ First waveguide length difference ΔL₁ Only
Long, second directional coupling 14₂ And the third directional coupler
14₃ Between the second optical waveguide 13 and₂ Is the first
Optical waveguide 13₁ Than the second waveguide length difference ΔL₂ Only long
The third directional coupling portion 14₃ And the fourth directional coupler 1
Four_Four Between the first optical waveguide 13 and₁ Is the second light
Waveguide 13₂ Than the third waveguide length difference ΔL₃ Only long
Fourth directional coupling portion 14_Four And the fifth directional coupler 14_Five 
Between the second optical waveguide 13 and₂ Is the second optical waveguide
Road 13₁ Than the fourth waveguide length difference ΔL_Four Just make it longer
Also has similar characteristics.

FIG. 7 is a plan view showing a second embodiment of the waveguide type optical multiplexer / demultiplexer of the present invention.

The waveguide type optical multiplexer / demultiplexer 70 of this embodiment is shown in FIG.
The third directional coupling portion 14 shown in FIG. ₃ Instead of the third
Directional coupling portion 14₃ Has a binding rate of half the binding rate of
Sixth directional coupling portion 74₆ And the third directional coupling portion 14
₃ Seventh directional coupling portion having a coupling rate of half the coupling rate of
74₇ And a sixth directional coupling portion 74 including₆ And the
7 directional coupler 74₇ Between the first optical waveguide 7 and
Three₁ Waveguide length and second optical waveguide 73₂ The waveguide length of
In terms of equality or near equality, in the first embodiment shown in FIG.
Different from the waveguide type optical multiplexer / demultiplexer 10.

That is, if the equal optical path length (waveguide length) is present,
Consider two light waves propagating in two optical waveguides
, The phase difference of each light wave is generally related to the propagation distance.
It is kept constant without. The interference phenomenon of light is the phase of two light waves
Since it is a phenomenon that takes advantage of the difference,
Regardless of the optical path length (waveguide length), the optical path
If the length difference (waveguide length difference) is constant, the total interference phenomenon
That is, the optical multiplexing / demultiplexing characteristics do not change. Therefore, in FIG.
The third directional coupling portion 14 shown₃ To the sixth directional coupler
74₆ And the seventh directional coupler 74₇ Divided into and 6th
Directional coupling 74 ₆ And the seventh directional coupler 74₇ Between
First optical waveguide 73₁ Waveguide length and second optical waveguide 73
₂ Even if the waveguide lengths of
The demultiplexing characteristics do not change.

For the above reasons, the waveguide type light of this embodiment is
Also in the multiplexer / demultiplexer 70 of the first embodiment shown in FIG.
Optical multiplexing / demultiplexing characteristics similar to those of the waveguide type optical multiplexer / demultiplexer 10 can be obtained.
It Actually, the input port of the entire waveguide type optical multiplexer / demultiplexer 70
From 76 to Crossport 77 ₂ Intensity T
_cross As a result of actually measuring the frequency dependence of
Transmission characteristics were obtained.

In the above description, the optical point symmetry arrangement does not mean that the point symmetry is geometrically symmetric. That is, optically, circuits in which light waves have similar interference effects are considered to be the same, and therefore they are topologically the same, and the optical path length difference of the corresponding optical waveguide and the coupling rate of the corresponding directional coupling portion are the same. Two circuits that are the same are considered optically identical circuits.

Although the silica type single mode optical waveguide formed on the silicon substrate is used as the optical waveguide, the waveguide type optical multiplexer / demultiplexer of the present invention is not limited to this, and other material type optical waveguides can be used. It is also applicable to optical waveguides. For example, it may be an ion diffusion optical waveguide formed by a metal ion diffusion technique on a multi-component glass substrate or a lithium niobate crystal substrate.

An example in which optical multiplexers / demultiplexers are individually formed on a silicon substrate has been shown. However, when a large number of optical multiplexers / demultiplexers are formed in an array on the same substrate, or on a substrate or a substrate. It goes without saying that the optical multiplexer / demultiplexer of the present invention can be applied as an element of a hybrid optical integrated circuit in which light reception / emission prevention is directly mounted on the end portion.

[0044]

Since the present invention is configured as described above, it has the following effects.

An intermediate portion between the first optical waveguide and the second optical waveguide includes first to fifth directional coupling portions which are sequentially formed in close proximity to each other at five places, and include a first basic component circuit and a first basic configuration circuit. 2 is the center point of the circuit (third directional coupling section 1
4 ₃ ) is arranged so as to be optically substantially point-symmetrical with respect to 4 ₃ ), so that a ring path is not used.
Since the frequency band where the light intensity transmittance is “1” and the frequency band where the light intensity transmittance is “0” can be flattened, the transmission characteristics can be improved without impairing the high speed.

[Brief description of drawings]

FIG. 1 is a plan view showing a first embodiment of a waveguide type optical multiplexer / demultiplexer according to the present invention.

FIG. 2 is a diagram optically equivalent to the waveguide type optical multiplexer / demultiplexer shown in FIG.

FIG. 3 is a plan view showing an asymmetric Mach-Zehnder interferometer type optical multiplexer / demultiplexer that is optically equivalent to the basic configuration circuit shown in FIG.

4 is a plan view showing an asymmetric Mach-Zehnder interferometer type optical multiplexer / demultiplexer for explaining the configuration of the asymmetric Mach-Zehnder interferometer type optical multiplexer / demultiplexer shown in FIG.

5 is a graph showing frequency dependence of light intensity transmittance from an input port to a cross port, FIG. 5A is a graph in the case of the asymmetric Mach-Zehnder interferometer type optical multiplexer / demultiplexer shown in FIG. 3B is a graph in the case of the asymmetric Mach-Zehnder interferometer type optical multiplexer / demultiplexer shown in FIG. 3, and FIG. 7C is a graph in the case of the waveguide type optical multiplexer / demultiplexer shown in FIG.

6 is a graph showing a measurement result of frequency dependence of light intensity transmittance from an input port to a cross-port in a prototype example of the waveguide type optical multiplexer / demultiplexer shown in FIG.

FIG. 7 is a plan view showing a second embodiment of the waveguide type optical multiplexer / demultiplexer of the present invention.

FIG. 8 is a plan view showing an example of a Mach-Zehnder interferometer type optical multiplexer / demultiplexer, which is one of typical conventional guided wave type optical multiplexer / demultiplexers.

[9] the frequency of the Mach-Zehnder interferometer type optical coupler-signal light P _through the light intensity transmittance with respect to light intensity transmittance and the signal light P _in the signal light P _cross with respect to the signal light P _in the filter shown in FIG. 8 It is a graph which shows an example of dependency.

10 shows a Mach-Zehnder optical interferometer type optical multiplexer / demultiplexer proposed as one of guided wave type optical multiplexer / demultiplexers capable of solving the problem in the Mach-Zehnder optical interferometer type optical multiplexer / demultiplexer shown in FIG. It is a top view.

11 is a graph showing an example of the frequency dependence of the light intensity transmittance of the signal light P _cross with respect to the signal light P _{in in} the Mach-Zehnder interferometer type optical multiplexer / demultiplexer shown in FIG.

[Explanation of symbols]

₁₀ , 70 Waveguide type optical multiplexer / demultiplexer 11, 71 Silicon substrate 13 ₁ , 33 ₁ , 43 ₁ , 73 ₁ First optical waveguide 13 ₂ , 33 ₂ , 43 ₂ , 73 ₂ Second optical waveguide 14 ₁ , 34 ₁ , 44 ₁ , 74 ₁ 1st directional coupling part 14 ₂ , 34 ₂ , 44 ₂ , 74 ₂ 2nd directional coupling part 14 ₃ , 34 ₃ 3rd directional coupling part 14 ₄ , 74 ₄ Fourth directional coupling portion 14 ₅ , 74 ₅ Fifth directional coupling portion 15 ₁ , 35 ₁ , 45 ₁ , 75 ₁ First thin film heater 15 ₂ , 35 ₂ , 45 ₂ , 75 ₂ Second thin film Heater 15 ₃ , 35 ₃ , 75 ₃ Third thin film heater 15 ₄ , 35 ₄ , 75 ₄ Fourth thin film heater 15 ₅ , 75 ₅ Fifth thin film heater 15 ₆ , 75 ₆ Sixth thin film heater 15 ₇ , 75 ₇ seventh thin film heater 15 _8, 75 ₈ 8 thin film heater 16,76 input port 17 ₁ of 77 ₁ Surupo 17 _2, 77 ₂ crossport 20 ₁ first basic configuration circuit 20 ₂ second basic configuration circuit 30 and 40 asymmetrical Mach-Zehnder interferometer type optical demultiplexer 74 ₆ sixth directional coupling portion 74 ₇ seventh Directional coupling part P _in Signal light T _throuh , T _cross , T ₂ Light intensity transmittance s, t, 2t Coupling rate

Claims (4)

[Claims] 1. A substrate, and a first optical waveguide and a second optical waveguide formed on the substrate, wherein light is incident from one of the first and second optical waveguides. The two signal lights are demultiplexed, one of the two signal lights is emitted from the one optical waveguide, and the other signal light of the two signal lights is divided into the first and second signal lights. Of the first optical waveguide, the signal light incident from the first optical waveguide and the signal light incident from the second optical waveguide are combined to generate the first optical waveguide.
In a waveguide type optical multiplexer / demultiplexer that emits light from either one of the second optical waveguide and the second optical waveguide, the intermediate portions of the first optical waveguide and the second optical waveguide are arranged in close proximity to each other at five positions and are sequentially arranged. A first to a fifth directional coupling portion formed, wherein the second optical waveguide is the first between the first directional coupling portion and the second directional coupling portion. Is longer than the optical waveguide by the first optical path length difference, and the first optical waveguide is the second optical waveguide between the second directional coupling portion and the third directional coupling portion. The second optical waveguide is longer than the first optical waveguide between the third directional coupling portion and the fourth directional coupling portion, the second optical waveguide being longer than the waveguide by the second optical path length difference. Is also longer by the third optical path length difference, and the first directional coupling section and the fifth directional coupling section are provided with the first directional coupling section. The optical waveguide is longer than the second optical waveguide by a fourth optical path length difference, the first to fourth optical path length differences are equal or substantially equal, and the coupling ratio of the first directional coupling portion is And the coupling rate of the fifth directional coupling section are equal or substantially equal to each other, and the coupling rate of the second directional coupling section and the coupling rate of the fourth directional coupling section are equal to or substantially equal to each other. A waveguide type optical multiplexer / demultiplexer characterized by the above. 2. A first optical path length difference between the first optical waveguide and the second optical waveguide between the first directional coupling portion and the second directional coupling portion. Between the second directional coupling portion and the third directional coupling portion, the second optical waveguide is longer than the first optical waveguide by a second optical path length difference. Between the third directional coupling portion and the fourth directional coupling portion, the first optical waveguide is longer than the second optical waveguide by a third optical path length difference, Between the fourth directional coupling portion and the fifth directional coupling portion, the second optical waveguide is longer than the first optical waveguide by a fourth optical path length difference. The waveguide type optical multiplexer / demultiplexer according to claim 1. 3. A sixth directional coupling section and a third directional coupling having a coupling rate of half the coupling rate of the third directional coupling section instead of the third directional coupling section. A seventh directional coupling section having a coupling rate that is half the coupling rate of the section, and between the sixth directional coupling section and the seventh directional coupling section, the first optical waveguide 73. ₁ optical path length and the second
The waveguide type optical multiplexer / demultiplexer according to claim 1 or 2, wherein the optical path lengths of the optical waveguides are equal or substantially equal to each other. 4. Quartz composed of a core portion made of silica-based glass in which the first optical waveguide and the second optical waveguide are embedded in a silica-based glass layer formed on a flat substrate, respectively. An optical multiplexer / demultiplexer according to any one of claims 1 to 3, wherein the optical multiplexer / demultiplexer is a system single mode optical waveguide.