JP2001083339A - Array waveguide type diffraction grating - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an array waveguide type diffraction grating which is small in dependence of a transmitted light wavelength on temperature and loss. SOLUTION: The array waveguides 4 of the array waveguide type diffraction grating successively connected with plural light input waveguides 2, first slab waveguides 3, plural array waveguides 4 varying in length from each other, second slab waveguides 5 and optical light output waveguides 6 on a substrate 1 are cut and separated in mid-way of a longitudinal direction to respectively form the first array waveguides 4a and the second array waveguides 4b, by which this array waveguide type diffraction grating is constituted. Connecting waveguides 8 which connect the corresponding first and second array waveguides 4a and 4b are disposed between the separated first and second array waveguides 4a and 4b in correspondence to all of the first and second array waveguides 4a and 4b. The connecting waveguides 8 are formed by the negative organic waveguides of the temperature coefficient of refractive indices different from the temperature coefficient of refractive indices and the lengths of the respective connecting waveguides 8 are formed to the lengths which nearly offset the dependence of the optical path lengths over the entire part of the array waveguides 4 on the temperature.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

[0001] 1. Field of the Invention [0002] The present invention relates to an arrayed waveguide type diffraction grating used for optical communication and the like, and more particularly to an arrayed waveguide type diffraction grating for compensating temperature fluctuation of a light transmission wavelength.

[0002]

2. Description of the Related Art In recent years, in optical communications, research and development on optical wavelength division multiplexing has been actively conducted as a method for dramatically increasing the transmission capacity, and practical use thereof has been progressing. Optical wavelength division multiplexing is, for example, a method of multiplexing and transmitting a plurality of lights having different wavelengths from each other. An optical wavelength multiplexing / demultiplexing device provided with a light transmitting device that transmits only light of a predetermined wavelength or a light reflecting device that reflects only light of a predetermined wavelength in order to extract light of Is essential.

As an example of a light transmitting device, a planar optical waveguide circuit (PLC; Planer Li) as shown in FIG.
ghwave Circuit). The optical waveguide circuit shown in the figure is an arrayed waveguide type diffraction grating (AWG;
(rrayed Waveguide Grating)
The arrayed waveguide type diffraction grating is formed by forming a waveguide configuration as shown in FIG. 1 on a substrate 1 made of silicon or the like, for example, using a silica glass core.

The waveguide configuration of the arrayed waveguide type diffraction grating is as follows.
At least one of the light input waveguides 2 arranged side by side
Of the first slab waveguide 3 is connected to a plurality of array waveguides 4 arranged in parallel, and the output side of the array waveguide 4 is connected to a second slab waveguide 3. 5
Are connected, and one or more light output waveguides 6 arranged side by side are formed on the emission side of the second slab waveguide 5.

[0005] The arrayed waveguides 4 are for propagating light derived from the first slab waveguides 3 and are formed to have different lengths, and the lengths of adjacent arrayed waveguides 4 are different from each other by ΔL. ing. The optical input waveguide 2 and the optical output waveguide 6 are provided in correspondence with the number of signal lights having different wavelengths to be split or multiplexed by, for example, an arrayed waveguide type diffraction grating. Wave 4
Are usually provided, for example, as many as 100. In the figure, for the sake of simplicity, the number of each of the optical input waveguide 2, the array waveguide 4, and the optical output waveguide 6 is shown. Is simply shown.

An optical fiber (not shown) on the transmission side, for example, is connected to the optical input waveguide 2 so that wavelength-division multiplexed light is introduced. The light introduced into the slab waveguide 3 spreads due to the diffraction effect and enters each array waveguide 4, and the array waveguide 4
Is propagated.

The light that has propagated through the array waveguide 4 is transmitted to the second
Reaches the slab waveguide 5, and is further condensed and output to the optical output waveguide 6. Since the lengths of all the array waveguides 4 are different from each other, each of the individual The phase of the light is shifted, and the wavefront of the converged light is tilted according to the amount of the shift.

When light is incident on the second slab waveguide 5 from the array waveguide 4 and the light is converged at an angle (diffraction angle) θ, θ and the wavelength λ of the condensed light are assumed to be θ. Has a relationship as shown in equation (1).

[0009] _{n s θ + n c ΔL =} mλ ····· (1)

[0010] Here, n _s is the refractive index of the second slab waveguide 5, n _c is the refractive index of the arrayed waveguide 4 (effective refractive index). M is the diffraction order, and its value is an integer.

In the equation (1), if the wavelength when θ = 0 is λ ₀ , the equation (2) is derived.

Λ ₀ = n _c ΔL / m (2)

For this reason, the light condensing positions of the lights having different wavelengths are different from each other. By forming the light output waveguides 6 at the positions, the light having different wavelengths can be transmitted to the different light output waveguides for each wavelength. 6 can be output.

That is, the arrayed waveguide type diffraction grating separates light of one or more wavelengths from the multiplexed light having a plurality of different wavelengths input from the optical input waveguide 2 to each optical output waveguide. 6 has a light demultiplexing function, and the center wavelength of the demultiplexed light is equal to the difference (Δ
L) and proportional to the effective refractive index n _c of the light guide 4.

Since the arrayed waveguide type diffraction grating has the above-described characteristics, the arrayed waveguide type diffraction grating can be used as a wavelength division multiplexing splitter for wavelength division multiplexing transmission. For example, as shown in FIG. .. Λn (n is an integer of 4 or more) is input from one optical input waveguide 2 to the first slab waveguide. 3, reaches the arrayed waveguide 4, passes through the second slab waveguide 5, and is condensed at different positions depending on the wavelength as described above, and enters the different optical output waveguides 6. The light is output from the output end of the optical output waveguide 6 through the optical output waveguide 6.

By connecting an optical fiber (not shown) for light output to the output end of each light output waveguide 6,
The light of each wavelength is extracted through the optical fiber.

The light transmission characteristics of the light output from each light output waveguide 6 (wavelength characteristics of the transmitted light intensity of the arrayed waveguide type diffraction grating) are as shown in FIG.
1, .lambda.2, .lambda.3,..., .Lambda.n), a light transmission characteristic in which the light transmittance decreases as the wavelength shifts from each light transmission center wavelength. In this figure, wavelength characteristics of light output from different optical output waveguides 6 are superimposed, and 32 different wavelengths of light having different wavelengths are diffracted into an arrayed waveguide type diffraction light as shown in FIG. When splitting by the grid,
The wavelength characteristics of the light output from each optical output waveguide 6 are shown.

The light transmission characteristic does not always have one maximum value, and may have two maximum values. The number of wavelengths showing the characteristics is not limited to one, but holds for different diffraction orders m in the above equation (1), and there may be a plurality of center wavelengths. Therefore, for example, when an arrayed waveguide type diffraction grating is used for wavelength division multiplexing optical communication, the diffraction order m is determined so that the light transmission characteristics correspond to the wavelength used in wavelength division multiplexing optical communication, and the arrayed waveguide type diffraction grating is determined. The grid is designed.

Since the arrayed waveguide type diffraction grating utilizes the principle of reciprocity (reversibility) of light, it has not only a function as an optical demultiplexer but also a function as an optical multiplexer. . That is, as shown in FIG. 4, when a plurality of lights having different wavelengths are made incident from the respective optical output waveguides 6, these lights pass through the reverse propagation path and are multiplexed by the array waveguide 4. The light is emitted from one optical input waveguide 2.

In such an arrayed waveguide type diffraction grating, as described above, since the wavelength resolution of the diffraction grating is proportional to the difference (ΔL) between the lengths of the arrayed waveguides 4 constituting the diffraction grating, ΔL is set to The large design enables the optical multiplexing and demultiplexing of wavelength-division multiplexed light with a narrow wavelength interval, which could not be realized by conventional diffraction gratings. , Ie, a function of demultiplexing or multiplexing a plurality of optical signals having a wavelength interval of 1 nm or less.

The arrayed waveguide type diffraction grating is manufactured by depositing and forming a waveguide structure of the arrayed waveguide type diffraction grating on a substrate 1 made of silicon or the like by using a glass material. Therefore, it is suitable for mass production.

[0022]

However, in the arrayed waveguide type diffraction grating as described above, the light transmission center wavelength has temperature dependence due to the following characteristics.
There is a problem that the central wavelength of light transmitted through the arrayed waveguide grating changes depending on the use temperature.

That is, since the length of each arrayed waveguide 4 changes due to thermal expansion and contraction of the waveguide caused by a temperature change of the arrayed waveguide type diffraction grating, the length difference Δ
L also added to change, by the temperature change, since it also changes the effective refractive index n _c of the arrayed waveguide 4, the optical path length of light propagating through the arrayed waveguide 4 (referred to the optical path length or optical length) Is further changed by the temperature change of the arrayed waveguide type diffraction grating. Therefore, if there is a temperature change in the arrayed waveguide type diffraction grating, the condensing position of the condensed light changes, the wavelength of the light incident on the light output waveguide 6 shifts, and the center wavelength of the light transmission characteristics also changes. Change.

The amount of change of the light transmission center wavelength due to the temperature change can be obtained by differentiating the above equation (2) with the temperature, and is expressed by the following equation (3).

[0025] _{dλ / dT = (λ / n} c) × (dn c / dT) + (λ / L) × (dL / dT) ····· (3)

In the equation (3), the first term on the right side is the temperature dependence of the effective refractive index of the arrayed waveguide 4, and the second term on the right side is the substrate 1
2 shows a change in the length of the array waveguide 4 due to the expansion and contraction of.

The refractive index temperature coefficient and the linear expansion coefficient of the arrayed waveguide 4 are positive values. Therefore, the higher the temperature of the arrayed waveguide type diffraction grating, the higher the temperature of the arrayed waveguide type diffraction grating. The center wavelength to be demultiplexed shifts to the longer wavelength side, and conversely, the lower the temperature of the arrayed waveguide grating becomes, the more the center wavelength shifts to the shorter wavelength side.

This is because, as the temperature rises, the refractive index of glass, which is a waveguide material, increases.
Is increased, and the length of the waveguide is physically increased by the linear expansion of the substrate 1 and the waveguide material (the second term of the right side of the equation (3) is increased). It is considered that the length of the optical path passing through the array waveguide 4 becomes longer.

For example, in order to measure the temperature dependence of the conventional arrayed waveguide type diffraction grating, the present inventors apply light having a wavelength λ = 1.55 μm to the arrayed waveguide diffraction grating, and
At 43 ° C. and 43 ° C., the center wavelength of the light transmitted through the arrayed waveguide type diffraction grating was measured, and the difference was measured.
Its value was 0.31 nm. When the temperature dependence of the center wavelength is determined from this result, it is 0.0155 nm / ° C.

Based on this result, the shift amount of the light transmission center wavelength due to the temperature change of the arrayed waveguide type diffraction grating formed by the quartz glass waveguide is obtained.
For light near 5 μm, the wavelength is 0.62 nm in a temperature range of 10 ° C. to 50 ° C., which is an indoor use temperature range as a wavelength division multiplexing optical communication device. Further, in a temperature range of 0 ° C. to 70 ° C., which is required as a specification of the device for wavelength multiplexing optical communication, the shift amount of the light transmission center wavelength is 1.08 nm.

In recent years, the interval between wavelength multiplexing and wavelength multiplexing / demultiplexing wavelengths in wavelength multiplexing communication is, for example, 0.4 nm or more.
Since the wavelength is very narrow at 1.6 nm, the value of the wavelength shift is not a negligible value.

Therefore, recently, as shown in FIG. 5, a groove 18 crossing the array waveguide 4 is formed in the middle of the array waveguide 4, and the groove 18 is
An array waveguide type diffraction grating of a type that compensates for the shift of the light transmission center wavelength due to the temperature change by filling a silicone resin 9 having a different refractive index from that of the optical waveguide has been proposed.

The silicone resin 9 has a negative temperature coefficient of refractive index. The groove 18 is formed in a triangular shape. As the length of the array waveguide 4 increases, the length of the silicone resin 9 increases. By increasing the length, the wavelength that is split or multiplexed by all the arrayed waveguides 4 is uniformly temperature-compensated by the silicone resin 9 to compensate for the light transmission center wavelength.

However, in this type of arrayed waveguide diffraction grating, since the temperature of the central wavelength of light transmission is compensated by the silicone resin 9 provided in the groove 18, the groove 18 is formed very accurately. And it is very difficult to make. Therefore, mass productivity is difficult, and the cost increases. In addition, the groove portion 18
Since it is difficult to manufacture the groove-shaped portion, even if the groove-shaped portion 18 is formed with extremely high precision, a manufacturing error is likely to occur.

The present invention has been made to solve the above-mentioned conventional problems, and its object is to provide an inexpensive, easy-to-manufacture and low-temperature-dependent light transmission center wavelength of an arrayed waveguide type diffraction grating. An object of the present invention is to provide an arrayed waveguide type diffraction grating.

[0036]

Means for Solving the Problems In order to achieve the above object, the present invention provides means for solving the problems with the following constitution. That is, according to the present invention, the first slab waveguide is connected to the output side of one or more optical input waveguides arranged in parallel, and the first slab waveguide is connected to the output side of the first slab waveguide. A plurality of juxtaposed arrayed waveguides of different lengths for transmitting light derived from the waveguide are connected,
A waveguide in which a second slab waveguide is connected to the output side of the plurality of arrayed waveguides, and a plurality of optical output waveguides arranged in parallel are connected to the output side of the second slab waveguide. A plurality of optical signals having different wavelengths input from the optical input waveguide are propagated with a phase difference for each wavelength by the arrayed waveguide, and a different optical output waveguide is provided for each wavelength. In the arrayed waveguide type optical diffraction grating for outputting light of different wavelengths from different optical output waveguides, all of the arrayed waveguides are cut and separated at at least one position in the middle in the longitudinal direction. Between the separated array waveguides, connecting waveguides for connecting the corresponding separated array waveguides are provided corresponding to all the separated array waveguides, and these connecting waveguides have a temperature coefficient of refractive index. The array The waveguides are formed by negative organic waveguides different from the temperature coefficient of the refractive index, and the lengths of the respective connection waveguides are formed so as to substantially cancel the temperature dependence of the optical path length of the entire arrayed waveguide. It is a means to solve the problem with a certain configuration.

In the present invention having the above structure, all the arrayed waveguides are cut and separated at at least one portion in the longitudinal direction, and the corresponding separated arrayed waveguides are connected between the separated separated arrayed waveguides. Connecting waveguides are provided corresponding to all the separated array waveguides.

In a conventional arrayed waveguide type diffraction grating, the transmission wavelength depends on the external environment temperature because the length of the arrayed waveguide changes with the change in the external environment temperature, and the optical path length of the propagation light changes. However, in the present invention, in the present invention, the connection waveguide is formed by a negative organic waveguide having a temperature coefficient of refractive index different from that of the arrayed waveguide type diffraction grating, and Since the length of the connection waveguide is formed so as to substantially offset the temperature dependence of the optical path length of the entire array waveguide, the connection waveguide reduces the temperature dependence of the entire optical path length of the array waveguide. It is possible to almost cancel out.

[0039]

Embodiments of the present invention will be described below with reference to the drawings. In the description of the present embodiment, the same reference numerals are given to the same parts as those in the conventional example, and the overlapping description will be omitted. FIG. 1 is a perspective view schematically showing an embodiment of an arrayed waveguide type diffraction grating according to the present invention.

As shown in the figure, the arrayed waveguide type diffraction grating of this embodiment also has a core waveguide structure formed on the substrate 1 like the conventional arrayed waveguide type diffraction grating.
The waveguide configuration has a plurality of optical input waveguides 2, a first slab waveguide 3, a plurality of array waveguides 4, a second slab waveguide 5, and a plurality of optical output waveguides 6. Further, the optical input waveguide 2, the array waveguide 4, and the optical output waveguide 6 are arranged side by side with a predetermined waveguide interval.

This embodiment is different from the conventional example in that all the arrayed waveguides 4 are cut and separated into a first arrayed waveguide 4a and a second arrayed waveguide 4b at an intermediate portion in the longitudinal direction. The distance between the separated first arrayed waveguide 4a and the second arrayed waveguide 4b is set to a corresponding separated arrayed waveguide (first and second arrayed waveguides 4a, 4a).
b) The connection waveguides 8 for connecting each other are provided corresponding to all the separated array waveguides, so that the temperature dependence of the optical path length of the entire array waveguide 4 is almost cancelled.

In this embodiment, the temperature coefficient of the refractive index of the arrayed waveguide 4 is positive, and the connecting waveguide 8 is an organic waveguide (a waveguide of an organic compound) having a negative temperature coefficient of the refractive index.
, And the length of the connection waveguides 8 is formed so as to substantially cancel the temperature dependence of the optical path length of the entire array waveguide.

The connection waveguide 8 is made of fluorinated polyimide (OPI-N3305 manufactured by Hitachi Chemical).
The refractive index of the connection waveguide 8 at a wavelength of 1.55 μm at 25 ° C. is 1.45, and the temperature coefficient of the refractive index of the connection waveguide 8 is −
It is 7.7 × 10 ⁻⁵ (1 / K). The length of each connection waveguide 8 is formed so as to satisfy the following equations (4) and (5).

Nc △ L = nc △ l + n′c △ l ’(4)

(Dnc / dT) △ l + (dnc '/ dT) △ l ′ = 0 (5)

Here, nc is the refractive index of the core forming the array waveguide 4, and ΔL is the length of the array waveguide 4 (the sum of the length of the array waveguide 4a and the length of the corresponding array waveguide 4b). ) And the length of the corresponding connection waveguide 8, the difference between the lengths of adjacent diffraction grating forming optical paths when the length is the diffraction grating forming optical path, and Δl is the difference between the optical path lengths of the adjacent array waveguides 4 (length Difference), Δl ′ indicates an optical path length difference (length difference) between adjacent connection waveguides 8, and nc ′ indicates a refractive index of the connection waveguide 8.

In the arrayed waveguide type diffraction grating of this embodiment, (dnc / dT) = 1 × 10 ⁻⁵ (1 / K), nc =
1.45, (dnc ′ / dT) = − 7.7 × 10 ⁻⁵ (1 / K),
nc ′ = 1.51 and ΔL = 60 μm. In addition,
Each of the above refractive indexes has a wavelength of 1.55 μm at 25 ° C.
Is the refractive index at.

In this embodiment, the corresponding first array waveguide 4a and second array waveguide 4b are arranged so that their optical axes face each other, and correspond to the first array waveguide 4a. A corresponding connection waveguide 8 is interposed between the second array waveguide 4b and the first and second array waveguides 4b.
a, 4b and the connection waveguide 8 are optically coupled. Also,
In order to suppress reflection at the connection end faces of the array waveguide 4 and the connection waveguide 8, each connection end face is formed on a slope inclined at an angle of 8 ° with respect to a plane orthogonal to the optical axis of each of the waveguides 4 and 8. Have been.

The present embodiment is configured as described above, and the arrayed waveguide type diffraction grating of the present embodiment is manufactured as follows. That is, first, a configuration similar to that of the conventional arrayed waveguide type diffraction grating is manufactured as follows. A lower clad film on the Si substrate 1 by a flame deposition method,
A core film is formed and vitrification is performed in a heating furnace to form a lower clad layer and a core layer. In order to increase the refractive index of the core, the core film is doped with a dopant such as TiO ₂ and GeO ₂ to have a composition different from that of the lower cladding layer.

Thereafter, a predetermined core pattern is formed on the core layer by using photolithography and dry etching techniques. Finally, an upper cladding film is formed in the same manner as the lower cladding film, and vitrification is performed to form an upper cladding layer. An array waveguide type diffraction grating without cutting the array waveguide 4 as shown in FIGS.

Next, at the central portion of the arrayed waveguide 4 of the arrayed waveguide type diffraction grating, a straight line portion orthogonal to the arrayed waveguide 4 is cut by a dicing saw, whereby all arrayed waveguides 4 are cut. It is separated into one array waveguide 4a and the second array waveguide 4b.

A connection waveguide group provided between the first arrayed waveguide 4a and the second arrayed waveguide 4b of the cut arrayed waveguide type diffraction grating is manufactured as follows. That is, fluorinated polyimide (OPI-N1005 manufactured by Hitachi Chemical Co., Ltd.) serving as a lower clad is applied on the Si substrate 1, flattened by spin coating, and then stepped to 100 °, 200 °, 350 ° in an oven. The temperature is increased and the fluorinated polyimide is cured to form a lower clad.

Thereafter, the substrate 1 with the lower clad is returned to room temperature, a fluorinated polyimide (OPI-N3305 manufactured by Hitachi Chemical Co., Ltd.) is applied on the lower clad, and spin coating and curing are performed in the same manner as the polyimide for the lower clad. Perform The core thickness at a spin coating rotation speed of 1800 rpm was 6 μm.

Thereafter, an oxide film SiO ₂ is formed on the core by a 0.5 μm sputtering method as a mask for core patterning, and a plurality of core patterns having a width of 6 μm are formed at intervals by photolithography and dry etching techniques. The connection waveguide groups arranged side by side are formed. The number of the connection waveguides 8 arranged in parallel corresponds to the number of the array waveguides 4. Thereafter, a fluorinated polyimide for upper cladding (OPI-N1005 manufactured by Hitachi Chemical Co., Ltd.) was applied on the core pattern so as to embed the core pattern, and the upper cladding was formed in the same manner as the lower cladding.

Then, the corresponding first arrayed waveguide 4a
The cut array waveguide type diffraction grating is arranged so that the optical axis of the second array waveguide 4b and the optical axis of the second array waveguide 4b face each other,
A corresponding connection waveguide 8 is provided between the first array waveguide 4a and the corresponding second array waveguide 4b. Then, using the alignment connection method, for example, the first array waveguide 4
a, the first and second array waveguides 4a, 4b and the connection waveguides are set such that the intensity of light propagating from the first through the corresponding connection waveguides 8 to the corresponding second array waveguide 4b is maximized. 8 are optically coupled, the separated ends of the first arrayed waveguide 4a, both ends of the connection waveguide 8 and the separated ends of the second arrayed waveguide 4b are fixed with an adhesive or the like.

The array waveguide 4a, the connection waveguide 8,
It is not necessary to connect and fix the array waveguides 4b collectively,
After the active alignment (alignment connection and fixing) of the array waveguide 4a and the connection waveguide 8, only the array waveguide 4b may be aligned and connected again.

The relative refractive index difference Δ of the connection waveguide 8 manufactured as described above with respect to the clad was 0.86% at the wavelength λ = 1.55 μm. The relative refractive index difference Δ is given by the following equation when the relative refractive index of the core (connection waveguide 8) is n ₁ and the relative refractive index of the cladding is n ₂ when the vacuum refractive index is 1. It is defined by (6), and the unit is%.

Δ = {(n ₁ −n ₂ ) / n ₁ } × 100 (6)

The present embodiment is manufactured as described above, and performs an optical multiplexing / demultiplexing operation such as demultiplexing of wavelength multiplexed light by an operation similar to that of the conventional arrayed waveguide type diffraction grating.
In the present embodiment, each array waveguide 4 having a positive refractive index temperature coefficient is cut and separated into a first array waveguide 4a and a second array waveguide 4b, and the corresponding array waveguide 4a and the array waveguide are separated. A connection waveguide 8 made of an organic waveguide having a negative coefficient of linear expansion is provided between the waveguide and the waveguide 4b. The length of each connection waveguide 8 determines the temperature dependence of the optical path length of the entire array waveguide 4. The temperature dependence of the entire arrayed waveguide 4 can be made very small because the size is formed so as to substantially cancel each other.

The inventors of the present invention actually found the temperature dependence of the light transmission wavelength in the arrayed waveguide type diffraction grating of this embodiment, and found that the temperature dependence of the transmission wavelength, which was about 0.0155 nm / K in the past, was obtained. Can be reduced to about 0.001 nm / K, and it is confirmed that the temperature dependence of the transmission wavelength can be significantly reduced to 1/15 or less by adopting the configuration of the present embodiment. Was.

In this embodiment, the excess loss generated by providing the connection waveguide 8 between the cut array waveguides 4a and 4b is 0.48 dB, and the provision of the connection waveguide 8 The loss increase could be kept very low.

The present invention is not limited to the above-described embodiment, but can adopt various embodiments. For example,
In the above-described embodiment, the connection waveguide 8 is formed of polyimide. However, the connection waveguide 8 is not necessarily formed of polyimide, and the negative organic conductor whose refractive index temperature coefficient is different from the refractive index temperature coefficient of the arrayed waveguide 4 is used. What is necessary is just to form by a wave path.

In the above-described embodiment, each array waveguide 4 is cut at one location in the longitudinal direction, and is divided into a first array waveguide 4a and a second array waveguide 4b.
Each arrayed waveguide 4 may be cut and separated at two or more locations in the longitudinal direction. Also in this case, the connection waveguides 8 are provided at the respective separation intervals in the same manner as in the above-described embodiment, and the corresponding separation array waveguides are connected to each other by the connection waveguides 8, so that substantially the same effect as in the above-described embodiment is obtained. Can play.

[0064]

According to the present invention, all the arrayed waveguides in the arrayed waveguide type diffraction grating are cut and separated at least at one point in the longitudinal direction, and the separated separated arrayed waveguides correspond to each other. Connection waveguides connecting the separated array waveguides are provided corresponding to all the separated array waveguides, and these connection waveguides have a refractive index temperature coefficient different from that of the arrayed waveguide type diffraction grating. The connection waveguide is formed by a negative organic waveguide, and the length of each connection waveguide is formed so as to substantially cancel the temperature dependence of the optical path length of the entire array waveguide. Thus, the temperature dependence of the optical path length of the entire arrayed waveguide can be almost canceled.

Further, in a conventional arrayed waveguide type diffraction grating in which a groove is formed to separate an intermediate portion in the longitudinal direction of the arrayed waveguide and silicon resin is provided in a groove between the separated arrayed waveguides, light is not transmitted. Since the light spreads when propagating in the silicone resin, the loss when light enters the array waveguide after propagating in the silicone resin was large, but in the present invention,
Since the arrayed waveguides separated from each other in the middle of the arrayed waveguide in the longitudinal direction are connected to each other by the connection waveguide, the light propagated in the connection waveguide enters the array waveguide with almost no leakage. It is possible to obtain an excellent arrayed waveguide type diffraction grating which can be reduced in size, has a small light transmission loss, and has a small temperature dependency as described above.

[Brief description of the drawings]

FIG. 1 is a perspective view schematically showing a main part of an embodiment of an arrayed waveguide grating according to the present invention.

FIG. 2 is an explanatory diagram showing a schematic configuration and a light demultiplexing function of a conventional arrayed waveguide grating in a perspective view.

FIG. 3 is a graph showing an example of a light transmission wavelength characteristic of a conventional arrayed waveguide type diffraction grating.

FIG. 4 is a perspective view showing a schematic configuration and a light multiplexing function of a conventional arrayed waveguide type diffraction grating.

FIG. 5 is an explanatory diagram showing a configuration example of a conventional arrayed waveguide type diffraction grating in which a silicon resin is interposed between arrayed waveguides.

[Explanation of symbols]

 Reference Signs List 1 substrate 2 optical input waveguide 3 first slab waveguide 4, 4a, 4b array waveguide 5 second slab waveguide 6 optical output waveguide 8 connecting waveguide

Continued on the front page (72) Inventor Takeshi Nakajima 2-6-1 Marunouchi, Chiyoda-ku, Tokyo Furukawa Electric Co., Ltd. (72) Inventor Kazuhisa Kashiwara 2-6-1 Marunouchi, Chiyoda-ku, Tokyo Furukawa Electric Industrial Co., Ltd. F term (reference) 2H047 KA02 KA03 KA12 LA19 QA04 QA05 RA00 TA00 TA35

Claims (1)

[Claims] 1. A first slab waveguide is connected to an output side of one or more optical input waveguides arranged side by side, and the first slab waveguide is connected to an output side of the first slab waveguide. A plurality of array waveguides having different lengths for transmitting light derived from the array waveguides are connected, and a second slab waveguide is connected to an output side of the plurality of array waveguides. The output side of the slab waveguide has a waveguide configuration in which a plurality of side-by-side optical output waveguides are connected, and a plurality of optical signals of different wavelengths input from the optical input waveguide, Array waveguide type optical diffraction that propagates with a phase difference for each wavelength by the array waveguide, makes it incident on a different optical output waveguide for each wavelength, and outputs light of different wavelengths from different optical output waveguides. In the grating, all of the array waveguides are in the middle of the longitudinal direction. Is cut and separated in at least one place, and connection waveguides for connecting the corresponding separated array waveguides are provided between the separated separated array waveguides so as to correspond to all the separated array waveguides. These connecting waveguides are formed by negative organic waveguides whose refractive index temperature coefficient is different from that of the arrayed waveguide,
In addition, the length of each connection waveguide is formed so as to substantially cancel the temperature dependence of the optical path length of the entire array waveguide.