JP2001228347A - Optical waveguide type wavelength filter - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a small-sized and new optical waveguide type wavelength filter having an excellent boxy filter characteristic, and a 1×N optical waveguide type wavelength filter successively providing these optical waveguide type wavelength filters and a variable wavelength filter/optical switch constituted of those optical waveguide type wavelength filters. SOLUTION: In the optical waveguide type wavelength filter laminated with a crossing input side optical waveguide 1 and an output side optical waveguide 2 and a ring resonator 3, and for performing ADD/DROP operation of the input side optical waveguide 1 and the output side optical waveguide 2 each other through the ring resonator 3, plural ring resonators 3a, 3b each other are laminated.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an optical waveguide type wavelength filter. For more information,
The invention of this application has excellent box-shaped filter characteristics,
The present invention relates to a new optical waveguide type wavelength filter, a 1 × N optical waveguide type wavelength filter in which the optical waveguide type wavelength filters are connected, and a tunable wavelength filter / optical switch constituted by the optical waveguide type wavelength filters.

[0002]

2. Description of the Related Art With the remarkable progress of advanced information technology in recent years, the inventor of the invention of the present application has already been working on a wavelength access network in order to realize further large capacity and high functionality of optical communication. An optical waveguide type wavelength filter that performs an ADD / DROP operation between an input optical waveguide and an output optical waveguide using a ring resonator, which is useful as an ADD / DROP type filter or the like, has been proposed (Japanese Patent Application No. 200-131).
0-32480).

FIG. 12 shows an example of this optical waveguide type wavelength filter. As illustrated in FIG. 12, the input side optical waveguide (1) and the output side optical waveguide (2) intersect, and a ring resonator (3) is stacked near the intersection. Part of the ring resonator (3) overlaps the input bus (11) of the input optical waveguide (1) and the DROP bus (21) of the output optical waveguide (2) at a certain interval. Are laminated. The interval is
The distance is such that optical coupling between the ring resonator (3) and each of the optical waveguides (1) and (2) is possible. In this case, of the wavelength multiplexed light guided through the input bus (11) of the input side optical waveguide (1), only the wavelength light that resonates with the ring resonator (3) is output via the ring resonator (3). DRO of side optical waveguide (2)
The signal is branched to the P bus (21).

In this optical waveguide type wavelength filter, the ring resonator (3) can have a radius of about 10 μm, and the free spectral width (FSR) can be about 20 nm. Has become.

[0005] However, in such an excellent optical waveguide type wavelength filter, further improvement in filter characteristics is desired in order to further improve the performance. More specifically,
Since the filter characteristic is of the Lorentz type, flatness of the transmission band has not been sufficiently obtained.

[0006]

SUMMARY OF THE INVENTION Accordingly, the present invention has been made in view of the above circumstances, and is an improvement on a conventional optical waveguide type wavelength filter, and a flattened transmission band to form a box. The following new optical waveguide type wavelength filter which realizes the filter characteristics described above is provided.

That is, according to the invention of this application, a crossed input optical waveguide and output optical waveguide and a ring resonator are laminated, and the input optical waveguide and the output optical waveguide are interconnected via the ring resonator. In the optical waveguide type wavelength filter which performs the ADD / DROP operation, an optical waveguide type wavelength filter is provided, wherein a plurality of ring resonators are laminated. , The flatness of the transmission band is adjusted according to the interval between the ring resonators.
Is one embodiment thereof.

Further, the invention of this application is characterized in that a plurality of the above-mentioned optical waveguide type wavelength filters have a through bus of an input side optical waveguide of one adjacent optical waveguide type wavelength filter and an input side optical waveguide of the other optical waveguide type wavelength filter. A 1 × N optical waveguide type wavelength filter characterized in that the input wavelengths of the optical waveguide type wavelength filters are connected and connected to each other, and the resonance wavelengths of the laminated ring resonators of the respective optical waveguide type wavelength filters are different from each other. 3), wherein in the 1 × N optical waveguide type wavelength filter, the optical waveguide type wavelength filter at the extreme end position is the input side optical waveguide of the optical waveguide type wavelength filter adjacent to the DROP bus of the output side optical waveguide. Is connected to the input bus of
The adjacent wavelengths of the optical waveguide type wavelength filters are connected to each other, and the resonance wavelengths of the laminated ring resonators of the optical waveguide type wavelength filters at the extreme end positions and the adjacent optical waveguide type wavelength filters are the same or different from each other. ) Is one embodiment thereof.

The above-mentioned optical waveguide type wavelength filter or 1 ×
In the N-waveguide type wavelength filter, the core layer and / or the cladding layer of each of the optical waveguides is made of a material having an electro-optic effect, a material having a thermo-optic effect, or a material having a photoelastic effect. According to another aspect of the present invention, the resonance wavelength of the laminated ring resonator is variable according to the control of the temperature, the control of the temperature, or the control of the external stress.

Further, the invention of this application is constituted by the above-mentioned optical waveguide type wavelength filter or 1 × N optical waveguide type wavelength filter, and the core layer and / or the cladding layer of each optical waveguide are formed by electro-optics. It is made of a material having an effect, a material having a thermo-optic effect, or a material having a photoelastic effect, and the resonance wavelength of the laminated ring resonator is variable according to the control of an external electric field, the control of temperature, or the control of external stress. A variable wavelength filter or an optical switch (claim 6) is also provided.

[0011]

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a block diagram showing an embodiment of the present invention;

[0012]

[Embodiment 1] FIG. 1 illustrates an optical waveguide type wavelength filter according to an embodiment of the present invention.

For example, as exemplified in FIG. 1, in the optical waveguide type wavelength filter of the present invention, the ring resonator (3) laminated on the crossed input optical waveguide (1) and output optical waveguide (2). It is characterized by itself being further laminated.

In this case, further description will be made. In FIG. 1, two ring resonators (3a) and (3b) are stacked. When an optical signal is coupled to each of the ring resonators (3a) and (3b), an even mode having a propagation constant βe and an odd mode having a propagation constant βo are excited. Here, two ring resonators (3
a) By adjusting the interval of (3b), the difference between the propagation constants of the even and odd modes is reduced, and the respective resonance wavelengths are slightly shifted. For this reason, the Lorentz-type filter characteristics as illustrated in FIG. 2A are synthesized, and a box-shaped filter characteristic can be obtained as illustrated in FIG. 2B.

Here, the propagation constant was analyzed by changing the distance between the ring resonators (3a) and (3b). As shown in FIG. 3, the lower-layer ring resonator (3a) and the upper-layer ring resonator (3b) both have the same structure and the like. For example, the width W _{r of the} ring core portion = 1.50 μm
m, the thickness t _r of the ring core portion is 1.50 μm, the radius R of the ring is 10 μm, and the core refractive index n _{c is} 1.7852.

Under this condition, the ring interval t _rsep =
At 1.00 μm, 1.25 μm, and 1.50 μm,
ShapeFact for Fines
or) was analyzed. The finesse was determined as the FSR for a 3 dB bandwidth of even mode, and the shape factor was 10
It was determined with a 1 dB bandwidth relative to a dB bandwidth. The input light is a TE mode light having a wavelength of 1.543 μm. FSR
Is assumed to be constant. FIG. 4 exemplifies this analysis result and shows the dependence of the shape factor on the finesse and the ring spacing. As is clear from FIG. 4, at any ring interval t _rsep , as the finesse increases, the shape factor improves and approaches the box-shaped filter characteristic. However, when the limit exceeds a certain limit, the filter characteristic is separated. It can be seen that the filter characteristics are no longer box-shaped.

From the above results, the optimum ring interval t for obtaining the most box-shaped filter characteristic in a certain finesse.
It can be seen that _rsep is uniquely determined. Therefore, in the optical waveguide type wavelength filter of the present invention, the two ring resonators (3a) and (b) are stacked, and the interval between them is adjusted, thereby realizing a box-shaped filter characteristic excellent in flatness of the transmission band. . By realizing the box-shaped filter characteristic, it is possible to improve the accuracy of the ADD / DROP operation of the resonance wavelength light.

[Embodiment 2] As described in Japanese Patent Application No. 2000-32480, the above-described optical waveguide type wavelength filter of the present invention realizes a 1 × N optical waveguide type wavelength filter by connecting a plurality thereof. Can be.

FIG. 5 shows an example of a 1 × 2 optical waveguide type wavelength filter when two optical waveguide type wavelength filters are connected. The two optical waveguide type wavelength filters are:
The through bus (12a) of one adjacent input-side optical waveguide (1a) and the input bus (11b) of the other input-side optical waveguide (1b) are connected and connected, and the adjacent optical waveguide type wavelength is used. The ring resonators (3aa) and (3ab) (hereinafter, referred to as “layer resonators”) stacked in the filter (1a) as described above.
And a laminated ring resonator (3ba) (3b) in the optical waveguide type wavelength filter (1b).
The resonance wavelengths of b) are different from each other, and a 1 × 2 optical waveguide type wavelength filter is formed.

In this case, the wavelength-division multiplexed optical signals λ _{1... N} input from the input bus (11a) of the input-side optical waveguide (1a) of one of the optical-waveguide-type wavelength filters are input to the input-side optical waveguide (1a). When propagating through (1b), the laminated ring resonators (3aa) and (3ab) or the laminated ring resonators (3ab)
ba) (optical signal of the wavelength lambda _a, or lambda _b matching the resonant wavelength of 3bb) are laminated ring resonator (3aa) (3a
b) or DRO of the output side optical waveguides (2a) (2b) where the laminated ring resonators (3ba) (3bb) overlap.
The signal is split into the P buses (21a) and (21b). On the other hand, likewise the wavelength lambda _a light or wavelength lambda _b light ADD bus (22
a) When input from (22b), the multilayer ring resonator (3aa) (3ab) or the multilayer ring resonator (3b)
a) (3bb), through buses (12a) (12
b).

This 1 × 2 optical waveguide type wavelength filter can be made very small because it is only necessary to connect the optical waveguide type wavelength filter of the present invention. Then, as described above, each optical waveguide type wavelength filter (3a)
Since the filter characteristic of (3b) has a box shape, the filter characteristic of the 1 × 2 optical waveguide type wavelength filter also has a box shape.

Of course, three or more optical waveguide type wavelength filters (3) may be connected in the same manner, and a 1 × N optical waveguide type wavelength filter having good box-shaped filter characteristics suitable for wavelength multiplex communication. Can be realized.

[Embodiment 3] FIGS. 6 and 7 each show a 1 × N optical waveguide type wavelength filter according to another embodiment of the present invention.

The 1 × N optical waveguide type wavelength filter illustrated in FIGS. 6 and 7 is adjacent to the DROP bus (21a) of the output side optical waveguide (2a) of the optical waveguide type wavelength filter located at the end. The configuration is such that an input bus (11b) of an input side optical waveguide (1b) of another optical waveguide type wavelength filter is connected. The laminated ring resonators (3aa) and (3ab) of the optical waveguide type wavelength filter at the extreme end overlap the input bus (11a) and the DROP bus (21a) in the example of FIG. 6, and in the example of FIG. It overlaps with the ADD bus (22a) and the through bus (12a).

In the 1 × N optical waveguide type wavelength filter having such a configuration, the resonance wavelengths of the laminated ring resonators (3a) and (3b) of the optical waveguide type wavelength filter at the extreme end position and the other adjacent optical waveguide type wavelength filters. Filter laminated ring resonator (3
a) If the FSRs of (3b) are different and only one resonance peak wavelength matches, only one peak can be extracted from a plurality of peaks of the periodic filter characteristic (so-called comb-shaped characteristic). become able to. If the respective resonance wavelengths are slightly deviated, a box shape is obtained.

[Embodiment 4] The optical waveguide type wavelength filter in each of the above-described embodiments has a laminated ring resonator (3a) on an input side optical waveguide (1) and an output side optical waveguide (2) crossed in the same layer. ) (3b) ((3a in FIGS. 5 to 7)
a) (3ab) or (3ba) (3bb)) is laminated, but other than this configuration, for example, as illustrated in FIG. 8, on the input side optical waveguide (1). The laminated ring resonators (3a) and (3b) may be laminated, and the output side optical waveguide (2) may be laminated on the upper ring resonator (3b). Of course, a part of the laminated ring resonators (3a) and (3b) overlaps the input optical waveguide (1) and the output optical waveguide (2) at a certain interval. Either the input side optical waveguide (1) or the output side optical waveguide (2) may be upside down.

Embodiment 5 In the optical waveguide type wavelength filter or the 1 × N optical waveguide type wavelength filter according to the present invention as described above, the core layer or the cladding layer of each of the optical waveguides (1) and (2) or the same. Both are made of a material having an electro-optic effect, a material having a thermo-optic effect, or a material having a photoelastic effect, and the laminated ring resonator (3a) (3a) ( By making the resonance wavelength of 3b) variable, a variable wavelength filter or an optical switch can be realized.

FIGS. 9, 10, and 11 are main part configuration diagrams showing one embodiment of the variable wavelength filter. In each embodiment, the core layer and / or the cladding layer of the input side optical waveguide (1) and the output side optical waveguide (2) are made of a material having an electro-optic effect, a material having a thermo-optic effect, or a photo-elastic effect. It is made of material.

In the example shown in FIG. 9, a heating element (4) as a thermal control means is provided on an upper ring resonator (3b), and the heating element (4) is used to form a laminated ring resonator (3a). The resonance wavelength of (3b) can be controlled. At this time, in order to prevent the Q value of the stacked ring resonators (3a) and (3b) from being reduced due to the heating element (4), the ring resonator (3b) in the upper layer and the heating element (4) are prevented. It is preferable to provide a buffer layer having a low refractive index between the layers. The heating element (4) is a cover layer (for example, SiO ₂ or the like) of the laminated ring resonators (3a) (3b).
It may be provided on the top. In this case, the heating element (4) does not need to be located immediately above the multilayer ring resonators (3a) and (3b).
a) A ring shape surrounding (3b) can be provided.

On the other hand, the laminated ring resonators (3a) (3b)
Has a characteristic of high sensitivity, the resonance frequency can be adjusted by providing a metal plate or a dielectric thin plate on the upper ring resonator (3b).

In the variable wavelength filter illustrated in FIG.
Micro electro mechanical (MEM) piston (51) and this M
A mechanical or optical control means (5) having a glass or polymer thin plate (52) held by an EM piston (51) is provided above the upper ring resonator (3b), The thin plate (52) moves up and down above the upper ring resonator (3b) in accordance with the piston movement of 51), thereby controlling the changing distance between the ring resonator (3b) and the thin plate (52). By doing so, the resonance frequency of the laminated ring resonators (3a) (3b) is controlled.

The thin plate member (52) is provided with a laminated ring resonator (3).
a) It is desirable that the entire surface of the laminated ring resonator (3b) is covered so that reflection is not caused by unevenly disturbing (3b).

When a thin plate (52) made of polymer is used, the thin plate made of polymer (52) and the ring resonator (3b) in the upper layer can always be kept in contact with each other. Thereby, a thin plate made of polymer (52)
Can be made lower than the refractive indexes of the laminated ring resonators (3a) and (3b). By pressing the polymer thin plate (52), the resonance wavelength of the laminated ring resonators (3a) and (3b) can be controlled in accordance with the photoelastic effect of the polymer whose refractive index changes with pressure.

The variable wavelength filter illustrated in FIG. 11 is one in which the resonance wavelength of the laminated ring resonators (3a) and (3b) is made variable by an electro-optical element (6) whose refractive index is electrically variable. The electro-optical element (6) as the electro-optical control means is made of, for example, a material such as an electro-optical polymer which is electrically controlled by a voltage applied via an electrode (61), and which is a ring resonance of an upper layer. Container (3
b) provided above.

Each of the above-described examples in the third embodiment is a case of a tunable wavelength filter. Similarly, by adjusting the phases and the like of the laminated ring resonators (3a) and (3b), the optical waveguide type light is adjusted. Switches can also be implemented.

The present invention is not limited to the above examples, and various embodiments can be made in detail. Each of the above-described embodiments is a case where the number of stacked ring resonators is two. However, it is needless to say that more ring resonators may be stacked, and the number of stacked ring resonators may be increased. Indeed, the flatness of the transmission band is improved. Even with an optical waveguide wavelength filter in which n ring resonators are stacked, a 1 × N optical waveguide wavelength filter, a variable wavelength filter, and an optical switch can of course be realized.

[0037]

As described in detail above, according to the present invention, a compact and excellent box-shaped filter characteristic can be obtained.
A new optical waveguide type wavelength filter, a 1 × N optical waveguide type wavelength filter in which the optical waveguide type wavelength filters are connected, and a tunable wavelength filter / optical switch constituted by the optical waveguide type wavelength filters are provided. As a result, it is possible to further increase the capacity and function of the optical communication.

[Brief description of the drawings]

FIG. 1 is a schematic perspective view illustrating an optical waveguide type wavelength filter of the present invention.

FIGS. 2A and 2B are conceptual diagrams illustrating flattening (boxing) of filter characteristics. FIG.

FIG. 3 is a schematic sectional view showing one embodiment of the optical waveguide type wavelength filter of the present invention.

FIG. 4 is a diagram illustrating the finesse and ring spacing dependence of the shape factor in the optical waveguide wavelength filter of FIG. 3;

FIG. 5 is a schematic perspective view showing an example of a 1 × N optical waveguide type wavelength filter of the present invention.

FIG. 6 is a schematic plan view showing another example of the 1 × N optical waveguide type wavelength filter of the present invention.

FIG. 7 is a schematic plan view showing still another example of the 1 × N optical waveguide type wavelength filter of the present invention.

FIG. 8 is a schematic view showing another example of the optical waveguide type wavelength filter of the present invention.

FIG. 9 is a schematic perspective view showing an example of the variable wavelength filter of the present invention.

FIG. 10 is a schematic diagram showing another example of the variable wavelength filter of the present invention.

FIG. 11 is a schematic diagram showing still another example of the variable wavelength filter of the present invention.

FIG. 12 is a schematic perspective view showing an example of a conventional optical waveguide type wavelength filter.

[Explanation of symbols]

 1, 1a, 1b Input optical waveguides 11, 11a, 11b Input bus 12, 12a, 12b Through bus 2, 2a, 2b Output optical waveguides 21, 21a, 21b DROP bus 22, 22a, 22b ADD bus 3, 3a, 3b Ring resonator 3aa, 3ab Ring resonator 3ba, 3bb Ring resonator 4 Heating element 5 Mechanical-optical control means 51 MEM piston 52 Thin plate 6 Electro-optical element 61 Electrode

Continuation of the front page (72) Inventor Zhu Shitoku M2J2B9 Canada, Ontario, North York, Clareville Crescent 17 F-term (reference) 2H047 KA03 KA12 KB01 KB08 LA18 NA01 NA02 NA10 RA08 2K002 AA02 AB04 BA06 BA13 BA20 DA08 EA13 HA01 HA02 HA11

Claims (6)

[Claims] An input optical waveguide and an output optical waveguide which are crossed with each other and a ring resonator are stacked, and an ADD / DROP operation between the input optical waveguide and the output optical waveguide is performed via the ring resonator. An optical waveguide wavelength filter, wherein a plurality of ring resonators are stacked. 2. The optical waveguide wavelength filter according to claim 1, wherein the flatness of the transmission band is adjusted according to the distance between the ring resonators. 3. An optical waveguide type wavelength filter according to claim 1, wherein a plurality of optical waveguide type wavelength filters have a through bus of an input side optical waveguide of one adjacent optical waveguide type wavelength filter and an input side optical waveguide of the other optical waveguide type wavelength filter. Is connected to the input bus of
1. A 1 × N optical waveguide type wavelength filter, which is connected to each other, wherein the laminated ring resonators of the respective optical waveguide type wavelength filters have different resonance wavelengths. 4. An optical waveguide type wavelength filter at an extreme end position,
The DROP bus of the output side optical waveguide is connected to the input bus of the input side optical waveguide of the adjacent optical waveguide type wavelength filter, and is connected to the adjacent optical waveguide type wavelength filter. 4. The 1 * N optical waveguide type wavelength filter according to claim 3, wherein the resonance wavelengths of the laminated ring resonators of the wavelength filter and the adjacent optical waveguide type wavelength filter are the same or different from each other. 5. The core layer and / or cladding layer of each optical waveguide is made of a material having an electro-optic effect, a material having a thermo-optic effect, or a material having a photo-elastic effect, for controlling an external electric field or 5. The optical waveguide type wavelength filter according to claim 1, wherein the resonance wavelength of the laminated ring resonator is variable according to control of temperature or control of external stress, or the 1 * N optical waveguide type wavelength filter according to claim 3 or 4. 6. The optical waveguide type wavelength filter according to claim 1 or 2 or the 1 × N optical waveguide type wavelength filter according to claim 3 or 4, wherein a core layer and / or a cladding layer of each optical waveguide is provided. It is made of a material with electro-optic effect, a material with thermo-optic effect, or a material with photo-elastic effect, and the resonance wavelength of the laminated ring resonator is variable according to the control of external electric field, the control of temperature, or the control of external stress. A tunable filter or optical switch, characterized in that: