JPH0973018A - Light wave length multiplexer/demultiplexer - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a light wavelength multiplexer/demultiplexer capable of correcting a central wavelength deviation arising during production. SOLUTION: In a light wavelength multiplexer/demultiplexer provided with a substrate 101, at least one input waveguide 102 formed on the substrate 101, an input side slab waveguide path 103 of a flat plate structure connected to the input waveguide 102, an array waveguide diffraction grating 104 consisting of multiple channels of wave guide paths 113, 114,..., 115 each of which is connected to the input waveguide 102 and has a different waveguide path length Li(i=1, 2, 3,...) from the others by ΔL, an output side slab of a waveguide path 105 connected to the array waveguide diffraction grating 104, and multiple output waveguide paths 106, 107,..., 108 connected to the output side slab of the waveguide path 105, a slit 109 is formed on the array waveguide diffraction grating 104.

Description

Detailed Description of the Invention

[0001]

TECHNICAL FIELD The present invention relates to an optical wavelength multiplexer / demultiplexer.

[0002]

2. Description of the Related Art In wavelength division multiplexing technology, an arrayed waveguide type optical wavelength multiplexer / demultiplexer (hereinafter referred to as "array type multiplexer / demultiplexer") is capable of extracting light of a specific wavelength from an output side. is there.

FIG. 4 is a plan view of a conventional 1-input / N-output optical wavelength multiplexer / demultiplexer using an arrayed waveguide diffraction grating. FIG.
4A is a sectional view taken along the line AA in FIG. 4, and FIG.
-B line sectional drawing, FIG.5 (c) is CC sectional view taken on the line of FIG. 4, FIG.5 (d) is DD sectional view taken on the line of FIG.

The configuration of a conventional optical wavelength multiplexer / demultiplexer will be described below with reference to FIGS. 4 and 5 (a) to 5 (d).

As shown in FIG. 4, the optical wavelength multiplexer / demultiplexer is a substrate
An input waveguide 202 formed on 201, a substantially fan-shaped input side slab waveguide 203 in which the input waveguide 202 is connected to the input side (lower left side in the figure), and one end of the input side slab waveguide An arrayed waveguide diffraction grating 204 connected to the output side (upper right side in the figure) of 203, and a substantially fan-shaped output side slab waveguide 205 having the other end of the arrayed waveguide diffraction grating 204 connected to the input side.
, And N output waveguides 206, 207, ..., 208 connected to the output side of the output side slab waveguide 205.

As shown in FIGS. 5A to 5D, the optical wavelength multiplexer / demultiplexer has a buffer layer 209 formed on a substrate 201.
A core 210 is formed on the buffer layer 209 with a material having a slightly higher refractive index than that of the buffer layer 209.
By covering the core with a clad 211 having a refractive index slightly lower than that of the core 210, the input waveguide 202 (FIG. 5 (a)), the slab waveguide 203 (FIG. 5 (b)), the arrayed waveguide diffraction grating
204 (FIG. 5C) and output waveguides 206, 207, ..., 208
(FIG. 5D) is formed.

The arrayed waveguide diffraction grating 204 has a plurality of channel waveguides whose lengths L _i (i = 1, 2, 3, ...) Are different by ΔL (for example, L _i = L _{i + 1} −ΔL). 212,213,
…, 214. The input-side slab waveguide 203 and the output-side slab waveguide 205 have a flat plate structure having a confining effect only in the film thickness direction.

FIG. 6A shows the waveform of the light intensity at the end face of the output side slab waveguide, and FIG. 6B shows the waveform of the output side slab waveguide corresponding to the position of the waveform shown in FIG. 6A. It is a figure which shows an end surface (it is also the figure which simplified FIG.5 (d)).

The operation principle of the arrayed waveguide diffraction grating type optical wavelength multiplexer / demultiplexer will be described below with reference to FIGS. 4, 6A and 6B.

The wavelength-multiplexed light 215 in which N waves of wavelengths λ ₁ -λ _N are multiplexed is spread by the diffraction effect in the input-side slab waveguide 203 following the input waveguide 202, and then further input-side slab guide is performed. Arrayed waveguide grating following waveguide 203
A plurality of channel waveguides 211, 212, ..., 213 constituting 204
It is propagated in and introduced into the output side slab waveguide 205 connected to the arrayed waveguide diffraction grating 204.

Here, the light introduced into the arrayed waveguide diffraction grating 204 is the length L of each channel waveguide 211, 212, ..., 213.
Since i is different from each other, the phases of the light beams are deviated. Since this phase shift has chromatic dispersion, the output side slab waveguide 20
Focused beams 61, 62,…, 6 of each wavelength at the end face 216 of 5
3 is focused on x ₁ , x ₂ , ..., x _N , respectively (Fig. 6).
(A)). Therefore, the wavelengths λ _{1 to} λ _N can be demultiplexed into the output waveguides 206, 207, ..., 208, respectively.

FIG. 7 is a wavelength loss characteristic diagram showing the relationship between the focused beam and the guided mode in each output waveguide, where the horizontal axis indicates the focusing position on the end face 216 (see FIG. 4), and the vertical axis indicates the vertical direction. The axis shows the light intensity. FIG. 8 is a wavelength loss characteristic diagram of the output waveguide, in which the horizontal axis represents wavelength and the vertical axis represents loss.

As an example, the wavelength loss characteristic of the i-th output waveguide will be described below with reference to FIGS. 7 and 8.

In FIG. 7, the focus position x of the focused beam 218 on the end face 216 of the output side slab waveguide 205 is shifted depending on its wavelength. At this time, the intensity of the light coupled to the output waveguide is the integral of the overlap portion (dotted area) 220 surrounded by the curve of the waveguide mode 219 of the i-th output waveguide and the curve of the focused beam 218. Is represented by. Therefore, when the focusing position x shifts with the shift of the wavelength (arrow P ₁ ), the integrated value of the superposed portion 220 gradually increases and the loss decreases.

In FIG. 8, a curve 221 shown by a solid line shows a loss wavelength characteristic of the i-th output waveguide, and a curve 225 shown by a broken line.
Shows the loss wavelength characteristic of the (i + 1) th output waveguide, and the curve 224 indicated by the alternate long and short dash line shows the loss wavelength characteristic of the (i-1) th output waveguide. A band 226 indicates a band used by the i-th output waveguide.

When the wavelength shifts further, it becomes minimum at the wavelength λ _i , and thereafter becomes gradually larger. Therefore, the loss wavelength characteristic curve 221 has a shape having a minimum value at the wavelength λ _i . Here, the point where 3 dB is increased from the above-mentioned minimum value of wavelength is referred to as 3 dB bandwidth 223.
The central wavelength of the bandwidth is defined as the central wavelength 222. 22
7 is crosstalk.

[0017]

However, the conventional arrayed waveguide diffraction grating type optical multiplexer / demultiplexer has the following problems.

The center wavelength of the light emitted from each output port is
It is required to have a desired value, and the deviation from the center wavelength is required to be 0.1 nm or less. The center wavelength of the emitted light varies due to variations in the optical path length of the arrayed waveguide diffraction grating and the thickness of the core of the channel waveguide that occur at the manufacturing stage.
There was a deviation from the intended center wavelength, which was a cause of yield reduction.

Therefore, an object of the present invention is to solve the above problems and to provide an optical wavelength multiplexer / demultiplexer capable of correcting the central wavelength shift occurring in the manufacturing stage.

[0020]

In order to achieve the above object, the present invention comprises a substrate and at least one substrate formed on the substrate.
Book input waveguide, an input-side slab waveguide connected to the input waveguide and having a flat plate structure, and a waveguide length L _i (i = 1, 2, 3,) connected to the input waveguide and different by ΔL. …)
An arrayed-waveguide diffraction grating consisting of a plurality of channel waveguides, an output-side slab waveguide connected to the arrayed-waveguide diffraction grating, and a plurality of output-use waveguides connected to the output-side slab waveguide. In this optical wavelength multiplexer / demultiplexer, slits are formed in the arrayed waveguide diffraction grating.

The present invention also provides a substrate, at least one input waveguide formed on the substrate, an input-side slab waveguide connected to the input waveguide and having a flat plate structure, and an input waveguide. Waveguide lengths L _i (i =
, 1, 2, 3, ...) Array waveguide diffraction grating consisting of a plurality of channel waveguides, an output-side slab waveguide connected to the array waveguide diffraction grating, and a plurality of output-side slab waveguides connected to the output-side slab waveguide In the optical wavelength multiplexer / demultiplexer provided with the output waveguide, the slit is formed in the arrayed waveguide diffraction grating, and the width of the slit is made different in each optical path.

In addition to the above structure, in the present invention, a matching agent having a desired refractive index may be injected into the slit.

With the above structure, when the light propagating through the channel waveguide of the arrayed-waveguide diffraction grating passes through the slit and enters the opposing channel waveguide, a slit causes an optical path length difference and is emitted from the output port. The wavelength of light changes. By injecting the matching agent into the slit, the optical path length difference is further changed, and the wavelength of the light emitted from the output port can be set to a desired wavelength.

[0024]

Embodiments of the present invention will be described below in detail with reference to the accompanying drawings.

FIG. 1 is a plan view showing an embodiment of an optical wavelength multiplexer / demultiplexer according to the present invention.

This optical wavelength multiplexer / demultiplexer is an arrayed waveguide grating type optical wavelength multiplexer / demultiplexer for multiplexing / demultiplexing an optical signal having a wavelength interval ΔL. The optical wavelength multiplexer / demultiplexer is composed of a quartz glass substrate (hereinafter referred to as “substrate”) 101 and an optical fiber 99.
An input waveguide 102 on which wavelength-multiplexed light 100 is incident from
The input side (lower left side in the figure) is a fan-shaped input side slab waveguide 103 connected to the input waveguide 102, and one end is connected to the output side (upper right side in the figure) of the input side slab waveguide 103. Array waveguide diffraction grating 104 and array waveguide diffraction grating 10
The output side slab waveguide 105 and the output side slab waveguide 105 that are connected to the input side (upper left side in the figure) to the other end of 4
Output waveguide 10 connected to the output side (lower right side in the figure) of
, 107, and 108, and a slit (groove) 109 for controlling the refractive index is formed in the arrayed waveguide diffraction grating 104.

This optical wavelength multiplexer / demultiplexer is similar to the conventional optical wavelength multiplexer / demultiplexer shown in FIG. 4 except that a buffer layer (209) is formed on a substrate 101 and the buffer layer (209) Core (210) from a material with a slightly higher refractive index.
(0) is a cladding with a slightly lower refractive index than the core (210)
It is covered with (211).

The input waveguide 102 is a channel waveguide having a rectangular cross-section structure, and a taper whose core width is gradually expanded toward the input side slab waveguide 103 immediately before the input side slab waveguide 103. It has a structure.

The input side slab waveguide 103 has a flat plate structure having no confinement structure in the lateral direction (direction along the substrate surface, that is, direction parallel to the paper surface). The end face 111 on the arrayed waveguide diffraction grating 104 side has an arc shape having a curvature center 112 at the connection point between the input waveguide 102 and the input side slab waveguide 103.

The arrayed waveguide diffraction grating 104 is composed of a plurality of channel waveguides 113, 114, ..., 115 having a rectangular cross section. The length of each channel waveguide 113, 114, ..., 115 is L
_i is different by ΔL (constant value) and arranged in the order of length (for example, L _i = L _{i + 1} −ΔL), i = 1, 2, 3,
…). The dimensions of these channel waveguides 113, 114, ..., 115 are designed to satisfy the single mode condition in the wavelength band used. In addition, the input side slab waveguide 10
In the vicinity of the output side of 3, the core width is
It has a taper structure that gradually expands toward
The input side slab waveguide 103 is arranged radially from the center of curvature 112 of the end face 111 on the array waveguide diffraction grating 104 side. Also, in the vicinity of the input side of the output side slab waveguide 1O5, the core width also has a taper structure that gradually expands toward the output side slab waveguide 1O5, and the array waveguide of the output side slab waveguide 105 is also provided. End face 11 on the side of the diffraction grating 104
They are arranged radially from the center of curvature 119.

The slits 109 on the arrayed waveguide diffraction grating 104 are formed so that the optical path length difference is Δl. Channel slits 113, 114, ..., 1 are provided in this slit 109.
An adhesive (for example, an ultraviolet curable epoxy adhesive) 110 as a matching agent, which is slightly different from the refractive index of 15, is injected and cured.

The output-side slab waveguide 1O5, like the input-side slab waveguide 103, has a flat plate structure having no lateral confinement structure. Array waveguide diffraction grating 104 end face 116
, The output waveguides 106, 107, ..., 108 and the output side slab waveguide
It has an arc shape with a center of curvature 119 on the connection surface with 1O5. Further, the end face 118 on the side of the output waveguides 106, 107, ...
Has an arc shape having a center of curvature 117 on the end surface 116 on the arrayed waveguide diffraction grating 104 side.

The output waveguides 106, 107, ..., 108 are composed of N channel waveguides having a rectangular cross section. The output waveguides 106, 107, ..., 108 have a linear shape near the output side of the output side slab guided path 1O5, and the output waveguides 106, 107 ,.
Along the end face 118 on the 08 side, they are arranged radially from the center of curvature 117 at intervals of an angle Δθ.

The center wavelength control method of the optical wavelength multiplexer / demultiplexer shown in FIG. 1 will be described below with reference to FIGS. 2 and 3.

In the arrayed-waveguide diffraction grating type optical wavelength multiplexer / demultiplexer, when the slit 109 is not formed, the central wavelength λ ₁ of the light emitted from the center of the output port is expressed by the equation (1).

[0036]

## EQU1 ## λ ₁ = ΔLN _eff / m where m is the diffraction order, N _eff is the equivalent refractive index, and ΔL is the optical path length difference of each channel.

Slits in the channel waveguides 113, 114, ..., 115
By forming 109 and using an adhesive 110 having a different refractive index in this slit 109, the central wavelength λ _{2 of the} light emitted from the same output port is changed to the formula (2).

[0038]

[Number 2] _{λ 2 = {(ΔL-Δl} ) · N eff + Δl · N effa} / m where N _effa the refractive index of the adhesive 110, .DELTA.l slit 10
9 shows the optical path length difference between the channel waveguides 113, 114, ..., 115 in FIG. Accordingly, the wavelength shift Δλ after the change of the refractive index is N
_{If effa} −N _eff = Δn, then this is _{expressed by} Equation 3.

[0039]

## EQU3 ## Δλ = λ ₂ 1 λ ₁ = ΔlΔn / m That is, the wavelength of the light emitted from the output port is changed by changing the optical path length difference Δl of the adhesive 110 injected into the slit 109. be able to.

FIG. 2 is a diagram showing the refractive index of the slit with respect to the refractive index of the substrate. The horizontal axis represents wavelength and the vertical axis represents loss.

In the same figure, a curve La shown by a solid line shows the loss wavelength characteristic when the refractive index of the adhesive 110 in the slit 109 is the same as the refractive index of the substrate 101. A curved line Lb indicated by a broken line and a curved line Lc indicated by an alternate long and short dash line show loss wavelength characteristics when the refractive index of the adhesive 110 in the slit 109 is different from that of the substrate 101. Also, λa is the slit 10
The refractive index n ₁ of the adhesive 110 in 9 is the refractive index n _{0 of the} substrate 101.
Is the center wavelength in the same case as. λb is the center wavelength when the refractive index n ₁ of the adhesive 110 in the slit 109 is smaller than the refractive index n ₀ of the substrate 101. λc is the center wavelength when the refractive index n ₁ of the adhesive 110 in the slit 109 is made larger than the refractive index n ₀ of the substrate 101.

In FIG. 3, the diffraction order m is 80, and Δl is 0.
FIG. 5 is a diagram showing the shift amount of the central wavelength when the refractive index of the adhesive in the slit is changed to 5 μm.

The refractive index difference is such that when the refractive index n ₀ of the substrate 101 is smaller than the refractive index of the adhesive 110 in the slit 109, the center wavelength shifts to the short wavelength side, and in the opposite case, it shifts to the long wavelength side. (Fig. 2).

It can be seen that when the refractive index difference is changed from 0 to 0.05, the center wavelength is changed from 0 to 0.3 nm.

As described above, according to the present embodiment, since the slits are formed in the arrayed waveguide diffraction grating, it is possible to realize the optical wavelength multiplexer / demultiplexer capable of correcting the center wavelength shift occurring in the manufacturing stage. .

In the above-described embodiments, the case where the quartz glass substrate is used has been described, but the present invention is not limited to this, and other light transmissive materials (for example, semiconductor, LiNbO 2) are used.
₍₃ etc.) may be used to form an arrayed waveguide grating type wavelength multiplexer / demultiplexer.

Further, an epoxy adhesive having a refractive index slightly different from that of the substrate was used for controlling the center wavelength, but it has light transmittance,
The same effect can be obtained by using a material having a desired refractive index (for example, low temperature glass).

[0048]

In summary, according to the present invention, the following excellent effects are exhibited.

In the optical wavelength multiplexer / demultiplexer, since the slits are formed in the arrayed waveguide diffraction grating, it is possible to realize the optical wavelength multiplexer / demultiplexer capable of correcting the center wavelength shift occurring in the manufacturing stage.

[Brief description of drawings]

FIG. 1 is a plan view showing an embodiment of an optical wavelength multiplexer / demultiplexer according to the present invention.

FIG. 2 is a diagram showing a refractive index of a slit with respect to a refractive index of a substrate.

FIG. 3 is a diagram showing the shift amount of the center wavelength when the diffraction order m is 80, Δl is 0.5 μm, and the refractive index of the adhesive in the slit is changed.

FIG. 4 is a conventional one-input N using an arrayed-waveguide diffraction grating.
It is a top view of an output optical wavelength multiplexer / demultiplexer.

5A is a sectional view taken along the line AA of FIG. 4, and FIG.
4 is a sectional view taken along the line BB of FIG. 4, (c) is a sectional view taken along the line CC of FIG.
(D) is the DD sectional view taken on the line of FIG.

6A is a diagram showing a waveform of light intensity at the end face of the output side slab waveguide, and FIG. 6B is a diagram showing an end face of the output side slab waveguide corresponding to the position of the waveform shown in FIG. 6A. is there.

FIG. 7 is a wavelength loss characteristic diagram showing a relationship between a focused beam and a waveguide mode in each output waveguide.

FIG. 8 is a wavelength loss characteristic diagram of the output waveguide.

[Explanation of symbols]

 101 substrate 102 input waveguide 103 input slab waveguide 113,114, ..., 115 channel waveguide 104 array waveguide diffraction grating 105 output slab waveguide 109 slit

Claims (3)

[Claims] 1. A substrate, at least one input waveguide formed on the substrate, an input-side slab waveguide connected to the input waveguide and having a flat plate structure, and the input waveguide. Wavelength lengths L _i (i = 1,
2, 3, ...) Arrayed-waveguide diffraction gratings composed of a plurality of channel waveguides, an output-side slab waveguide connected to the arrayed-waveguide diffraction grating, and a plurality of output-side slab waveguides connected to the output-side slab waveguide In the optical wavelength multiplexer / demultiplexer having the output waveguide, a slit is formed in the arrayed waveguide diffraction grating. 2. A substrate, at least one input waveguide formed on the substrate, an input-side slab waveguide connected to the input waveguide and having a flat plate structure, and the input waveguide. Wavelength lengths L _i (i = 1,
2, 3, ...) Arrayed-waveguide diffraction gratings composed of a plurality of channel waveguides, an output-side slab waveguide connected to the arrayed-waveguide diffraction grating, and a plurality of output-side slab waveguides connected to the output-side slab waveguide In the optical wavelength multiplexer / demultiplexer provided with the output waveguide, a slit is formed in the arrayed waveguide diffraction grating, and the width of the slit is made different in each optical path. vessel. 3. The optical wavelength multiplexer / demultiplexer according to claim 1, wherein a matching agent having a desired refractive index is injected into the slit.