JP3224086B2 - Arrayed waveguide grating with variable frequency width of flat band characteristics - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001] The present invention relates to an arrayed waveguide grating having a variable frequency width of a flat band characteristic which can realize an arrayed waveguide type optical multiplexer / demultiplexer having a flat optical frequency band characteristic.

[0002]

2. Description of the Related Art FIG. 1 shows an example of a conventional arrayed waveguide grating. The arrayed waveguide grating connects the input channel waveguides 2, the channel waveguide array 4, the output channel waveguides 3, and the input channel waveguides 2 and the channel waveguide arrays 4 arranged on the substrate 1. And a second fan-shaped slab waveguide 6 for connecting the channel waveguide array 4 and the output channel waveguide 3 to each other. Are sequentially increased by a predetermined waveguide length difference ΔL.

In such a conventional arrayed waveguide grating, as shown in an enlarged view near the first sectoral slab waveguide 5 in FIG. The cores of the respective channel waveguides 2 and 4 of the channel waveguide array 4 were connected by a tapered waveguide (also referred to as a tapered waveguide) that spreads linearly.
Similarly, as shown in an enlarged view of the vicinity of the second sector slab waveguide 6 in FIG. 3, the output channel waveguide 3 and the channel waveguide array 4 at the boundary with the second sector slab waveguide 6. The core of each waveguide was connected to the second fan-shaped slab waveguide 6 by a tapered waveguide that spreads linearly.

In FIGS. 2 and 3, R is the radius of curvature of the first and second fan-shaped slab waveguides 5 and 6, and U is the tapered core of the input and output channel waveguides 2 and 3. Aperture width, S ₁ is the distance between the input and output channel waveguides 2 and 3, d ₁ is the length of the tapered waveguide of the input and output channel waveguides 2 and 3, and D is the channel waveguide array 4
Tapered waveguide core opening width, 2a channel waveguide portion of the core width, S ₂ interval of each waveguide of the channel waveguide array 4, and d ₂ are electrically tapered channel waveguide array 4 The length of the wave path.

[0005]

As shown in FIG. 4, the frequency characteristic of such a conventional arrayed waveguide grating is such that the center optical frequency of each waveguide (in FIG. 4, 200 GHz interval,
When converted to a wavelength, the loss characteristic becomes parabolic in the vicinity of 0.0016 μm), and the 1 dB frequency bandwidth is B 1 dB = 35.
(GHz).

As described above, the array waveguide grating having the above-described conventional structure has a parabolic loss characteristic. Therefore, the wavelength (optical frequency) of the laser light source changes due to a temperature change or the like so that the center of each signal channel (waveguide) is changed. When the wavelength fluctuates from the wavelength (the center optical frequency), there is a problem to be solved that the loss increases significantly.

An object of the present invention is to solve the above-mentioned problems of the prior art by changing an input waveguide.
Flat band characteristics that can change the bandwidth of the duplexer
Is to provide an array conducting grating whose frequency width is variable .

[0008]

In order to achieve the above-mentioned object, an array of the present invention having a variable frequency width of the flat band characteristic is provided.
The guiding waveguide grating includes an input channel waveguide, a channel waveguide array, an output channel waveguide, and a second channel connecting the input channel waveguide and the channel waveguide array arranged on the substrate. And a second fan-shaped slab waveguide connecting the channel waveguide array and the output channel waveguide, wherein the length of the channel waveguide array is a predetermined length. An arrayed waveguide grating configured to be sequentially elongated with a difference in wave length , wherein a core of each input waveguide of the input channel waveguide near a boundary with the first fan-shaped slab waveguide has a parabolic shape. And light enters the different input channel waveguides.
When input, the second fan-shaped slab waveguide and the output
Flat electricity formed at the boundary with the channel waveguide
The cores of adjacent parabolic-shaped input waveguides are formed so as to have different widths so that the field distributions have different widths.

Here, the parabolic shape of the core of each input waveguide of the input channel waveguide is as follows:

[0010]

(Equation 2)

(Where A _i is a parameter specifying each parabolic shape, a is １ ／ of the core width, x is a position in the direction of the core opening width, and y is a position in the axial direction of the core). Can be done.

In the present invention, as described above, the core width of each input waveguide has a parabolic shape near the boundary between the first fan-shaped slab waveguide and the input channel waveguide array. A light distribution having a flat electric field distribution is formed at the boundary between the fan-shaped slab waveguide and the output channel waveguide. For this reason, it is possible to realize an arrayed waveguide grating having a flat band characteristic such that the demultiplexing output characteristic becomes substantially constant even when the frequency of the light source changes. Furthermore, since the widths of the adjacent parabolic-shaped input waveguide cores are different from each other, when light is input to the different input waveguides, the second fan-shaped slab waveguide and the output channel waveguide are not connected to each other. The width of the flat electric field distribution formed at the boundary differs from one another.

Therefore, in the present invention, the frequency width of the flat band characteristic can be changed by selecting the input waveguide, and the frequency width of the flat band characteristic can be selected according to the requirements of the system. In addition, this makes it possible to provide an optical demultiplexer suitable for large-capacity, long-distance optical communication, wavelength division routing, and the like.

[0014]

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

FIG. 5 shows an array waveguide type optical multiplexer / demultiplexer as an example of the embodiment of the flat band characteristic array waveguide grating of the present invention. In this optical multiplexer / demultiplexer, an input channel waveguide 12, an output channel optical waveguide 13,
A channel waveguide array 14, a first fan-shaped slab waveguide 15 for connecting the input channel waveguide 12 to the channel waveguide array 14, and a connection between the channel waveguide array 14 and the output channel waveguide 13; A second fan-shaped slab waveguide 16 is formed on the substrate 11. The channel waveguide array 14 is configured such that its length is sequentially increased by a predetermined waveguide length difference ΔL.

FIG. 6 is an enlarged view of the vicinity of the first fan-shaped slab waveguide 15 showing the features of the present invention. As shown in FIG. 6, each core of the input channel waveguide 12 near the boundary of the first fan-shaped slab waveguide 15 has a parabolic shape in which adjacent cores have different core widths. On the other hand, the core of each waveguide of the channel waveguide array 14 near the boundary of the first fan-shaped slab waveguide 15 has a tapered shape that spreads linearly, as in the conventional example.

In FIG. 6, R is the radius of curvature of the first fan-shaped slab waveguide 15 and D is the channel waveguide array 1.
A core opening width of the waveguide 4 of the tapered, 2a channel waveguide portion of the core width, S ₂ interval of channel waveguide array 14, d ₂ the taper length of the channel waveguide array 14 (the waveguide Length of the tapered portion).

Further, W _i (in the present embodiment is set to i = 1 to 3) is the core opening width of each waveguide in the parabolic shape of the input channel waveguide 12, S ₁ is input channel waveguide 12 , L _i (i = 1 to 3 in the present embodiment)
Is the length of each parabola of the input channel waveguide 12 (parabola-shaped portion of each waveguide).

As shown in the enlarged view of FIG. 7, the polarizer shape of the core of each waveguide of the input channel waveguide 12 near the boundary with the first fan-shaped slab waveguide 15 is such that the direction of the core opening width is x. And y is the axial direction of the core, and is determined by the following equation (1). (Where A _i is a parameter for specifying each parabolic shape, and a is 1/1 of the core width.
2 (referred to as core half width). )

[0020]

(Equation 3)

Now, in the configuration of FIG. 5, one port of the input channel waveguide 12 has an optical frequency f (wavelength λ = c
/ F: where C is the speed of light). The incident light forms a parallel beam light distribution when passing through the parabolic region shown in FIG. 6, and at the boundary with the first fan-shaped slab waveguide 15, a space as shown in FIG. A flat electric field distribution is generated. Core width 2a =
7 [mu] m, in the case of the core thickness (core thickness) 2t = 7 [mu] m, refractive index difference delta = 0.75% of the optical waveguide, the structural parameters for obtaining a flat light distribution as shown in FIG. 8, A ₁ =
1.0, l ₁ = 250 μm, A ₂ = 1.1, l ₂ = 30
0 μm, A ₃ = 1.2, l ₃ = 350 μm.

The thus-obtained light having a flat distribution further spreads in the first fan-shaped slab waveguide 15 in the lateral direction, and excites the respective waveguides of the channel waveguide array 14 to produce the second light. Is focused on the position of the output channel waveguide 13 corresponding to the optical frequency f in the fan-shaped slab waveguide 16.

At this time, according to the reciprocity theorem, the light distribution at the boundary between the second fan-shaped slab waveguide 16 and the output channel waveguide 13 is also similar to the distribution shown in FIG.
The light distribution becomes flat as shown in FIG.

FIG. 10 is an enlarged view of the vicinity of the second fan-shaped slab waveguide 16 of FIG. Second fan-shaped slab waveguide 1
The core of each of the output channel waveguides 13 and the channel waveguide array 14 near the boundary of No. 6 has a tapered shape that spreads linearly as in the conventional example. Here, R is the radius of curvature of the second fan-shaped slab waveguide 16, D is the core opening width of the tapered waveguide of the channel waveguide array 14, 2a is the core width of the channel waveguide portion, S ₂ is the interval between the channel waveguide arrays 14, and d ₂ is the taper length of the channel waveguide array 14. Also, U
Is a core opening width of the waveguide of the tapered output channel waveguide 13 (all the same width), S ₁ is the interval of the output channel waveguide 13, d ₁ output channel waveguide 13
Is the taper length.

Since the core opening width U of the waveguide of the output channel waveguide 13 is designed to be a fraction of the width of the flat light distribution shown in FIG. Even if f changes slightly, the amount of light coupled to the output channel waveguide 13 becomes substantially constant. That is, a flat frequency band characteristic is realized in which the demultiplexed output is substantially constant even if the frequency f of the light source slightly changes.

Further, as shown in FIG. 9, since the widths of the light distributions from different parabola widths W _i (i = 1 to 3 in the present embodiment) are different from each other, the frequency at which the demultiplexed output becomes substantially constant is obtained. The width can be changed by choosing the input channel waveguide.

[0027]

An embodiment of the present invention will be described in detail with reference to the drawings.

With respect to the arrayed waveguide grating of the present invention described with reference to FIGS. 5 to 10, a mask was manufactured using the following parameters. That is, 2a = 7 μm, R = 11.
3 mm, ΔL = 63 μm, S ₂ = 25 μm, D = 20 μ
m, d ₂ = 2 mm, S ₁ = 25 μm, U = 10 μm, A
₁ = 1.0, l ₁ = 250 μm, W ₁ = 32 μm, A ₂
= 1.1, l ₂ = 300 μm, W ₂ = 37 μm, A ₃ =
1.2, l ₃ = 350 μm, W ₃ = 42 μm.

The flat band characteristic array waveguide grating of the present embodiment was manufactured using the quartz optical waveguide with the mask thus manufactured.

First, an SiO ₂ lower cladding layer was deposited on the Si substrate 11 by a flame deposition method, and then a SiO ₂ glass core layer to which GeO ₂ was added as a dopant was deposited. . Next, the core layer was etched using a pattern as shown in FIGS. 5, 6, and 10 based on the above design, to produce an optical waveguide portion.
Finally, the SiO ₂ upper cladding layer was deposited again.

The measurement results of the optical frequency characteristics of the flat band characteristic arrayed waveguide grating manufactured as described above are shown in FIGS.
It is shown in FIG. 13 (the frequency interval is 200 GHz, and the wavelength is 0.0016 μm). 11 to 13 show measurement results of frequency characteristics when light is input to the input channel waveguides 12 having parabola widths W _{1 to} W ₃ , respectively.

As shown in FIG. 11, when light is input to the input channel waveguide having a parabolic width of W ₁ = 32 μm, the 1 dB frequency bandwidth is B _1dB = 116 (GHz). Further, as shown in FIG. 12, when light is input to the input channel waveguide having a parabola width of W ₂ = 37 μm,
The dB frequency bandwidth is B _1dB = 140 (GHz).
Further, as shown in FIG. 13, 1 dB when light is input to an input channel waveguide having a parabola width of W ₃ = 42 μm.
Is B _1dB = 164 (GHz). From FIG. 11 to FIG. 13, the optical frequency characteristics are flattened, and by inputting light into the input channel waveguides having different parabola widths W _{1 to} W ₃ , flat frequency characteristics of different bandwidths are obtained. It can be seen that it has been obtained.

Thus, the 1 dB bandwidth which was 35 (GHz) in the conventional arrayed waveguide grating (FIG. 4) is
By inputting light into input channel waveguides having different parabola widths, the flat frequency characteristics of different bandwidths are greatly increased without deteriorating the crosstalk of adjacent signal channels, and the flat frequency characteristics of one array waveguide grating are different. It can be seen that it can be obtained by:

[0034]

As described above, according to the present invention,
Input switch near the boundary with the first fan-shaped slab waveguide
The core of each input waveguide of the channel waveguide is spread in a parabolic shape.
Light is input to different input channel waveguides.
Slab waveguide and output channel
Flat electric field distribution formed at the boundary with the waveguide
So that the widths of adjacent
Since the waveguide cores are formed with different widths,
Changing the demultiplexer bandwidth by changing the force waveguide
For example, WDM channel width to be demultiplexed
(When multiple channels are included in the 3 dB band)
Can be obtained.

Therefore, according to the present invention, even when the wavelength of the light source such as a laser fluctuates from the center wavelength of each signal channel due to a temperature change or the like, the passage loss does not increase, so that the design tolerance of the wavelength division routing system and the like can be improved. Has the advantage of increasing Further, according to the present invention, the frequency width of the flat band characteristic can be changed by selecting the input waveguide, and the frequency width of the flat band characteristic can be changed by one arrayed waveguide grating according to the requirements of the system. A remarkable effect that it can be realized is obtained.

[Brief description of the drawings]

FIG. 1 is a perspective view showing an example of the structure of a conventional arrayed waveguide grating.

FIG. 2 is an enlarged view of the vicinity of a first fan-shaped slab waveguide 5 in FIG.

FIG. 3 is an enlarged view of the vicinity of a second fan-shaped slab waveguide 6 in FIG.

FIG. 4 is a graph showing measurement results of frequency characteristics of a conventional arrayed waveguide grating.

FIG. 5 is a perspective view showing an example of an embodiment of a flat band characteristic arrayed waveguide grating of the present invention.

FIG. 6 is an enlarged view of the vicinity of a first fan-shaped slab waveguide 15 in FIG.

7 shows an input channel waveguide 12 and a first channel waveguide 12 shown in FIG. 6;
FIG. 4 is an enlarged view showing one of the parabolic cores near the boundary with the fan-shaped slab waveguide 15.

8 is a graph showing an electric field distribution at a boundary between a first fan-shaped slab waveguide 15 and an input channel waveguide 12 in FIG.

9 is a graph showing an electric field distribution at a boundary between a second fan-shaped slab waveguide 16 and an output channel waveguide 13 in FIG.

FIG. 10 is an enlarged view of the vicinity of a second fan-shaped slab waveguide 16 in FIG.

In the flat band characteristic arrayed waveguide grating of the present invention in FIG. 11 FIG. 6 is a graph showing the measurement results of the frequency characteristics in the case of inputting light to the input channel waveguide having a width W ₁ of the parabolic.

12 is a graph showing measurement results of frequency characteristics when light is input to an input channel waveguide having a parabola width W ₂ in the flat band characteristic array waveguide grating of the present invention in FIG. 6;

13 is a graph showing measurement results of frequency characteristics when light is input to an input channel waveguide having a parabola width W ₃ in the flat band characteristic array waveguide grating of the present invention in FIG. 6;

[Explanation of symbols]

Reference Signs List 1 substrate 2 input channel waveguide 3 output channel waveguide 4 channel waveguide array 5 first sector slab waveguide 6 second sector slab waveguide 11 substrate 12 input channel waveguide 13 output channel waveguide Waveguide 14 Channel waveguide array 15 First fan-shaped slab waveguide 16 Second fan-shaped slab waveguide W _i (W ₁ , W ₂ , W ₃ ) Input channel waveguide 12
Core opening width l _i (l ₁ , l ₂ , l ₃ ) of each parabolic waveguide of the input channel waveguide 12
Core width A _i of length S ₁ interval 2a channel waveguide portion of the input channel waveguide 12 of the parabolic portion of each waveguide _{(A 1, A 2, A} 3) parameter specifies the respective parabolic R the first fan-shaped slab waveguide 15 radius of curvature D waveguides of the channel waveguide core opening width of the waveguide of the tapered array 14 S ₂ channel spacing d ₂ channel waveguide array 14 of waveguide array 14 in the tapered Part length

Continuation of the front page (56) References JP-A-8-211237 (JP, A) ELECTRONICS LETTE RS Vol. 32, no. 18, p. 1661-1662 (1996) (58) Fields investigated (Int. Cl. ⁷ , DB name) G02B 6/12-6/14 G02B 6/28-6/293 JICST file (JOIS)

Claims (2)

(57) [Claims] An input channel waveguide disposed on a substrate, a channel waveguide array, an output channel waveguide, and a first connecting the input channel waveguide and the channel waveguide array. A fan-shaped slab waveguide, and a second fan-shaped slab waveguide connecting the channel waveguide array and the output channel waveguide, wherein the length of the channel waveguide array is a predetermined waveguide length An arrayed waveguide grating configured to be sequentially elongated by a difference , wherein a core of each input waveguide of the input channel waveguide near a boundary with the first fan-shaped slab waveguide spreads in a parabolic shape. And light is input to a different input channel waveguide.
A second fan-shaped slab waveguide and an output channel waveguide;
The width of the flat electric field distribution formed at the boundary of
S differently, adjacent said parabolic input waveguide of variable array guide his path grating frequency width of the flat band characteristic, wherein a width of the core is different from each other by formation of. 2. The parabolic shape of the core of each input waveguide of the input channel waveguide is given by: (Where Ai is a parameter specifying each parabolic shape, a is は of the core width, x is the position in the direction of the core opening width, and y is the position in the axial direction of the core). 2. The arrayed waveguide grating according to claim 1, wherein the frequency width of the flat band characteristic is variable .