KR100198464B1 - Nxn waveguide grating router using multimode interface - Google Patents

Abstract

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a multi-mode interference NxN optical waveguide grating router, which is a core component in realizing a WDM (Wavelength Division Multiplexing) all-optical network of the next generation, as a waveguide grating router (WGR) , The conventional WGR is implemented by integrating the radial star coupler and the optical waveguide row and solving the problem that the insertion loss (chip inside) of about 3-4dB is inevitably generated by the radiation of the molding coupler In the present invention, the NXN WGR with high performance is proposed by replacing the radial shaping coupler with the multimode interference (MMI) shaping coupler by incorporating the low loss performance of the MMI shaping coupler into the design of the WGR. A wavelength channel spacing is given and a path difference of the waveguide to be used in the optical waveguide row is determined so that an appropriate channel wavelength is assigned to the output waveguide when light is incident on the input waveguide i. Then, it is verified through computer simulation that the lightwaves entering the input terminal other than the input waveguide i are allocated to the output terminals of the same N channel wavelengths at the output terminal. That is, the 8x8 WGR using the waveguide path difference of the optical waveguide row found in the NxN MMI WGR is 0.4 dB or less in 1.6 nm (200 GHz) wavelength channel spacing with the standardization movement of the current wavelength division method as a result of computational simulation using the BPM (Beam Propagation Method) And a crosstalk of -25 dB or less.

Description

Multi-mode interference NxN optical waveguide grating router

The present invention relates to a waveguide grating router (WGR), and more particularly, to a waveguide grating router (WGR), in which a radial forming coupler is replaced by a multimode interference (MMI) Mode interference NxN optical waveguide grating router.

Optical waveguide grating routers are typically optical waveguide grating routers composed of radial shaping couplers and optical waveguide arrays. Their design methods and interpretations are generally as follows.

Figure 1 shows the structure of a 5x5 shaped coupler.

The shaping coupler is used for the input and output stages of the optical waveguide grating router and its proper design is very important because it determines the performance of the optical waveguide grating router. In general, the number of input and output stages is uniformly constituted by waveguide arrays of NxN structure and is arranged symmetrically with respect to the center of the free region. From a practical point of view, the curved waveguide of the starting point is far enough away from the side waveguide to pass the curved waveguide without being affected by the mutual coupling. Then, a straight waveguide is positioned before the free area, gradually narrowing the gap with the waveguide on the side.

As shown in Fig. 1, the straight waveguides are directed toward the center of the counterpart circle. The light wave excited at the input waveguide reaches the free space of the slab waveguide shape and diffracted to transmit the uniform optical power to the output waveguide. The area corresponding to the free area consists of two circles forming an intersection, the center of which is located in the escort of the opposing circle.

Since the input waveguides are close to each other in the vicinity of the free region, a mutual coupling occurs in which a part of the optical power is passed to the adjacent waveguide. Therefore, this mutual coupling means that the emitted light wave is not diffracted from the slab waveguide region but diffracted before that. The generation of the mutual coupling does not greatly affect the optical power, but the optical waveguide lattice router generates the effect of removing the phase center from the boundary between the actual waveguide and the slab waveguide. Therefore, a longitudinal displacement distance is required to adjust the shifted focus position in the waveguide array. In order to maintain the shape of the radiation pattern constantly, a waveguide not used next to the edge waveguide is deliberately set so that the shape of the wave excited in the outermost waveguide is shaped like a center light wave.

Ideally, in designing optical waveguide grating routers using the above molded coupler, it is desirable to have very low parent densities and to use as many input / output stages as possible. Therefore, assuming that the number of usable channels approaches the total number of input / output stages, the arrangement pattern of the light waves aligned to the output stage can be expressed as follows.

Where N is the number of waveguides used, and [Delta] [psi] represents the phase difference of the aligned light waves aligned in the second shaping combiner.

If the number of waveguides to be used as the input / output stage approaches the number of waveguide columns forming the radiation pattern, the angle at which the entire output cross-section is to be searched becomes larger in the pattern of the lightwaves as a whole, so that the parent wave appears in the angle at which the output waveguide exists. This phenomenon eventually leads to crosstalk between channels. Therefore, it is reported that using half of the total I / O stages as input / output stages is not affected by the negative mode.

The general radius setting should be such that the light waves passing through the narrow slit can be spread sufficiently. As the radius increases, the loss increases. Therefore, it is necessary to select a value that considers the lossy surface and the uniformity at the same time. In addition, the angle of the output waveguide must be determined so that the diffracted light wave in the tilted waveguide row is guided well. If the angle is large, the optical power appearing on the output waveguide is reduced. When the angle is small, the coupling with the waveguide on the side becomes large.

In order to use two designed couplers as a WDM device, the waveguide row connecting the couplers must be designed. In terms of role, the forming coupler simply divides the incoming light wave by the same amount, and the branched light wave reaches the second forming coupler through the waveguide row having the same length differences as the side waveguide. The phase of the light waves in the slab waveguide region of the second shaped coupler reached a certain difference.

FIG. 2 shows the phase relation of the light waves arranged at the input end of the second shaping coupler. The relationship of the phase differences aligned through the optical waveguide row is as follows.

Here, ΔL is the difference in length of the waveguide thermal gratings, and n _eff is the effective refractive index of the waveguide thermal grating. In order to correctly interpret Δφ, it is necessary to change it to a normalized amount and then expressed as a normalized phase difference Δψ '.

Here, m is a positive integer closest to n _eff ? L /?, Which means the order of the array waveguide grating. From the point of view of the normalized phase difference,

Where m0 is expressed.

On the other hand, the relationship between the phase difference Δψ '(λ) between adjacent light waves at the input end of the coupler and the inclination angle Δθ shown in FIG. 1 is as follows.

Where n _c is the refractive index of the free region and? Is the spacing between the waveguide rows at the input end. Assuming that a lens with a focal length f is placed at the input end using the relationship between the equations (4) and (5), the position x at which the focus appears is expressed as a function of wavelength as follows.

Using the equation (6), the change of the position of the output terminal according to the change of the wavelength can be finally expressed as follows.

Since the light waves used in the analysis are plane waves, a tool that acts as a lens is needed to focus on one point. Therefore, in the optical waveguide lattice router, the linear waveguide column serves as a lens at the input and output ends, and collects the coherent light waves in a certain direction according to the topological arrangement at a point of the free domain output section. The change of the phase arranged according to the change of the wavelength is observed as the phenomenon that the focused light wave searches for the free space, which means that the wavelength can be filtered by optically using this phenomenon. If the wavelength is a short wavelength with respect to the central wavelength, the normalized phase difference △ ψ 'has a positive value, so that an image is generated upward with respect to the center of the output section. In case of a long wavelength, a normalized phase difference Δψ' It can be expected that a negative value is generated and an image is generated in the lower side.

The basic relationship used in the design of optical waveguide columns is as follows. First, the following equation can be obtained by applying Equation (7) to the interval between the output waveguides by using the channel spacing [Delta] [chi] _ch .

The channel wavelength focused on one point of the output stage changes the position of the output stage where the phase changes as the wavelength changes with respect to the center wavelength. The repetition period of the wavelength to be filtered at one output end is referred to as FSR (Free Spectral Range) and can be expressed as follows.

Where c is the velocity of the light wave in air.

If the above equation (9) is converted into a wavelength relationship in the frequency relationship, the following equation is obtained.

The above equation (10) can be rearranged as a simple relation as follows.

In the equation (11), it can be seen that the Free Spectral Range is simply determined through the relationship between the diffraction order and the wavelength. As can be seen from Equations (8) and (11) above, the selection of arbitrary lattice orders, the focus interval and the gap of the waveguide rows form an organic relationship, . Since the arbitrary number of diffraction orders does not affect the channel spacing and the free spectral range, it is necessary to adjust the focal distance and the interval of the waveguide columns in order to adjust only the channel spacing in the fixed free spectral range. Finally, the focal length must be carefully designed since it is accompanied by various parameters such as the radius of the circle of free space and the focus compensation distance for focusing the aligned light waves.

Meanwhile, the conventional optical waveguide grating router has a structure using a molding coupler as shown in FIG. 3, and related design techniques and fabrication are now being commercialized in Europe and Japan. However, this structure inherently has a surplus insertion loss of about 3-4 dB and there is no clear alternative to solve it.

The operation of a conventional optical waveguide grating router composed of the radial shaping coupler shown in FIG. 3 is as follows. The light wave that has branched through the first shaping combiner 1 has a specific phase difference due to the optical waveguide row having a constant path difference and focuses the light wave at one point of the output stage through the second shaping combiner 2.

In order to realize an all-optical network using WDM technology, components such as a WGR (waveguide grating router), a tunable DBR semiconductor laser, a tunable receiver, and a frequency (wavelength) converter are required. In particular, WGR plays a very important role in optical path routing, add / drop filtering, and so on. A conceptual diagram illustrating the function of the 5x5 WGR to illustrate the function of the WGR is shown in FIG. Since the position of the output terminal changes according to the position of the input end and the incident wavelength, it can be seen that the optical path can be routed by changing the wavelength according to the position of the input end using a wavelength converter.

As described above, two commonly used methods for realizing the WGR are the two radial forming couplers shown in FIG. 1 for the input and output stages, and an AWG (Arrayed Waveguide Grating) It is a connected form. By properly adjusting the length difference between adjacent waveguides in the AWG, the function shown in FIG. 8 can be performed. In such a device, a surplus insertion loss of about 3-4 dB occurs due to the radiation of the waveguide structure (excluding absorption of material and scattering loss). On the other hand, the mask design process is relatively complicated because it requires much more waveguides than the number of input / output stages in the optical waveguide array and the focal distance of the molding coupler and coupling between the input and output waveguides must be carefully considered.

The MMI NxN coupler of the present invention has a very small excess insertion loss, a very simple structure and a small size.

In this NxN optical coupler, when a light wave is incident on a specific input terminal, each output terminal has a specific phase value. For example, let Φ _{ik be} the phase at each output k when entering at input i. If the phase of the incoming light wave is -Φ _ik each time the light wave enters the waveguide of the output stage upside down, the light wave appears at the input i according to the Reciprocity Theorem. Using this principle properly, we can implement the NxN WGR shown in the conceptual diagram of Fig. 4 by using two NxN MMI couplers and AWGs. Of course, the length of each waveguide should be determined to be output to a specific output waveguide at a specific wavelength.

The present invention aims to provide a method of manufacturing a semiconductor device using a simple mask design and a tolerance at the time of fabrication, with a surplus insertion loss of less than 0.5 dB, very good channel isolation (less cross-channel crosstalk)

1 is a schematic diagram of a conventional NxN optical waveguide grating router configured with a radial shaped coupler;

FIG. 2 is a schematic diagram of an NxN optical waveguide grating router configured with a multi-mode coupler proposed in the present invention; FIG.

FIG. 3 is a cross-sectional refractive index profile of a unit waveguide considered in the optical waveguide grating router in FIG. 2; FIG.

FIG. 4 is a frequency response characteristic curve of a 4 × 4 optical waveguide grating router according to an embodiment of the present invention,

(a) shows a case where the first input waveguide is excited.

(b) shows a case where the third input waveguide is excited.

FIG. 5 is a frequency response characteristic curve of an 8 × 8 optical waveguide grating router according to another embodiment of the present invention,

(a) shows a case where the first input waveguide is excited.

(b) shows a case where the fifth input waveguide is excited.

6 is a schematic view of a typical 5x5 shaped coupler;

7 is a schematic view showing the coherence of light waves at the output end of the optical waveguide grating router;

FIG. 8 is a functional diagram of the optical waveguide grating router. FIG.

In order to achieve the above object, the multi-mode interference NxN optical waveguide grating router of the present invention includes N input terminals for inputting a plurality of channel wavelengths, A first NxN multimode interference combiner for outputting the first NxN multimode interference combiner output to the branched image; N pieces of grating optical waveguide columns for transmitting the branched propagated light waves so as to have different phases according to a path difference of each waveguide; And a second NxN multiplexing step of adjusting the optical waveguide thermal grating so as to focus on a specific position of the output end thereof with N output terminals so that optical powers having respective phase differences are reproduced at a specific position of the output terminal in accordance with a wavelength, Mode interference combiner.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, the present invention will be described in detail with reference to the accompanying drawings.

FIG. 4 is a configuration diagram of an NxN optical waveguide grating router configured as a multi-mode coupler of the present invention.

The first multi-mode interference combiner 11 serves to uniformly branch the optical power incident on an arbitrary position by using a general interference effect. The optical waves propagated to the N optical waveguide columns 13 branched have different phases according to the path difference of each waveguide and arrive at the second multi-mode interference coupler 12. Optical powers having respective phase differences are regenerated at specific output positions of the second multi-mode interference coupler 12 according to wavelengths by adjusting the optical waveguide thermal grating so as to focus on a specific position of the output stage.

The proposed low - loss NxN optical waveguide grating router consists of two multi - mode interference combiners and optical waveguide arrays connecting them. The multi-mode interference coupler, which has recently been attracted attention due to its excellent reproducibility and low loss characteristics resulting from the simplicity of the shape, can analyze the phase relationship of the modes that can exist in the multi-mode waveguide, so that the electric field distribution of incident light on the wave- Or multi-mode waveguides that are reproduced in multiple form.

The NxN type multi-mode interference combiner can obtain N branched images using the general interference effect of the multi-mode, and the length of the device can be obtained as follows.

Where L _x is the beat length between the two lowest modes and N is the number of phases.

In order to utilize a multimode interference coupler as a broadband WDM device such as an optical waveguide grating router, a low loss characteristic and a wavelength independent characteristic are required. Therefore, in order to improve the universal ridge-type multi-mode interference coupler, it is necessary to deeply etch the core region in the multi-mode region. This process is similar to the assumption that the mode of the participating modes to form the self-image is to obtain Equation (12) since the Goo-Haenchen shift effect becomes small due to the large binding force of the light source in the multi-mode region. The load can be expected. Thus, the loss can be improved through this process. The second is that the typical wavelength-dependent nature of passive devices is proportional to the length of the device. Therefore, the input and output terminals of the multi-mode interference coupler are brought as close as possible within the range where mutual coupling does not occur, thereby reducing the length of the device as much as possible. Table 1 shows the characteristics of the designed results for InP / INGaAsP 4x4 and 8x8 multimode interference combiners.

The phase condition of the optical waveguide column to be used in the proposed NxN optical waveguide grating router,

As follows. The first term ([Delta] [phi] _1n ⁱ ) of the above equation (13) represents the phase difference at each stage (output stage 1) at the output stage n of the first multi-mode interference combiner 11 when the i- Mode interference coupler 12, the second term? 1 _1n ^j represents the phase difference at each end of the input terminal of the second multi-mode interference coupler for generating the phase of the light wave at the j-th output terminal of the second multi- 1). △ Φ _1n ^{i, j} represents the phase difference (reference waveguide No. 1) of the path that is incident on the i-th input and passes through the n-th optical waveguide row and goes to the j-th output.

Table 2 shows the phase difference between the reference stage (input stage number 1) and the input stage at an arbitrary position in the first NxN multimode combiner. The phase difference calculated in the actual design process exists as the phase of the inherent light wave according to the number of input / output stages due to the general interference effect irrespective of the refractive index of the medium. Table 3 shows the phase relationships of the light waves required at the input stage to match the phase to a specific output in the second NxN multimode interference combiner. Table 4 summarizes the phase difference compared to the reference short-wave (i = 1) according to the change of the input stage generated in the first NxN multimode interference combiner and the phase difference compared to the input signal of the second NxN multimode interference combiner When the phase difference of the required branched light source is expressed through the relationship of Equation (13), the relative phase difference is compared with the reference short-wave (n = 1) only when the light wave is subjected to the light rupture.

As shown in Table 4, the relative phase difference &Dgr; &PHgr; of the optical waveguide (n = 2 ... N) is satisfied at a specific wavelength, the light wave excited at the input i of the optical waveguide grating router will have a phase at the output j. The channel wavelengths are ... λ ... λ and the length difference of the optical waveguide row satisfying Table 3 at each wavelength should be obtained. The portion to be considered in the construction of the NxN optical waveguide row is the path difference of the N-1 waveguide rows. (Path difference between the waveguide n and the waveguide 1) of the optical waveguide column required for the channel wavelength? To exit at the output stage j, using the phase difference relationship of the optical wave to be experienced in the optical waveguide string obtained through the above equation (13) Shall satisfy the following formula.

Where n _eff is the effective refractive index in the waveguide sequence, and m _1n ^{i, j} is 0 ^{, 1} , 2 ... . Lt; / RTI >

(? L ₁₂ , ...) satisfying the above equation (14). ,? L _1n , ... ΔL _1N } is smoothly determined, the light wave incident on the input terminal i of the path difference set is output to the output terminal j of λ _j ^{i, j} (j = 1 to N). The relation for obtaining one path difference? L _1n is shown in the following equations (15-23).

(1) When the first input is excited

When the first input stage is excited, the channel wavelength array of the output stage P ₁ = {λ ₁ ^1,1 , ... ? _j ^{1, j} , ... λ _N ^{1, N} }

(2) When the i-th input is excited

When the j-th input terminal is excited, the channel wavelength array of the output terminal

P _i = {? ₁ ^{i, 1} , ... ? _j ^{i, j} , ... λ _N ^{i, N} }

(3) When the Nth input terminal is excited

When the Nth input terminal is excited, the channel wavelength array of the output terminal

P ₁ = {? ₁ ^{N, 1} , ... ? _j ^{N, j} , ... λ _N ^{N, N} }

The channel wavelength constellation {λ ₁ , ... ? _j , ... λ _N }, it is necessary to generate a new channel wavelength array according to the position of the excited input terminal and the position of the output terminal which forms the image in order to obtain the path difference (ΔL _1n ) of the optical waveguide row. Then, a set of channel wavelength arrays generated by the combination {P ₁ , ... P _i, ... P _N }. Using the above equations (15) to (23) to find one path difference [Delta] L _1n , an integer m _1n ^i, which means a unique phase difference and the number of self- each of the path difference between the calculated by ΔL ^{j {1,1} ... _1n ,? L _1n ^{1, j} ... ,? L _1n ^{1, N} ... ,? L _1n ^{i, 1} ... ,? L _1n ^{i, j} ... ,? L _1n ^{i, N} ... ,? L _1n ^{N, 1} ... ,? L _1n ^{N, j} ... , ΔL _1n ^{N, N} } have different values. Therefore, one path difference ([Delta] L _1n ) having a globally unified value must be determined by comparing each different path difference. The following is the normalization procedure for comparing each path difference.

Assuming that the reference path difference is? L _1n ^1,1 ,

If L _1n ^1,1 -ΔL _1n ^{i, j} > 0, 1 is a positive integer, and if ΔL _1n ^1,1 -ΔL _1n ^{i, j} <0, then 1 has a negative integer, and the integer l is Range is always satisfied.

Therefore, the NxN path differences? L _1n determined by the inherent phase difference are obtained by computerization. Since this process uses numerical analysis, the following tolerance range should be set. And one waveguide path difference (ΔL _1n ) is determined when there is a unified path difference within the tolerance range.

Where ε is the tolerance for converging the numerical error to find the path difference.

The sequence of channel wavelengths {P ₁ , ... P _i, ... P _N } is an important issue. Therefore, in the present invention, the path difference of the optical waveguide row is obtained by using the repeatability of the phase difference. First, the phases that should be satisfied in the optical waveguide row due to the eigen phase difference of the light waves branched by the two multi-mode interference combiners expressed in Table 4 are investigated. Through this process, the phase differences for generating phases at the respective output stages corresponding to the input terminals excited in Table 4 can be represented as a set as shown in Table 5. [ The set of phase differences shown in Table 5 is expected to have a mutually independent relationship between the sets of phase differences that the optical waveguide row must satisfy in order to generate an image at the output stage when one input stage is excited.

The mutual independence of the phase difference sets is that no phase difference set is formed with the same composition and position of the elements under the condition that the same input is excited.

If we extend this relation until the Nth input is excited, we find that the phase difference set required when the same input is excited is present in a group of phase difference sets formed according to the output stage when the other input is excited. I could. Therefore, if the same channel wavelength is allocated to the same phase difference position by applying the mutual independence of the phase difference of the multi-mode interference coupler, the output channel of the output channel The wavelength can be expected. This process can effectively shorten the computerized processing time by knowing the wavelength sequence to be determined by the repeatability of the phase difference set.

Therefore, considering the number of combinations of N! Channel wavelengths corresponding to N phase differences, an arrangement table of channel wavelengths to be used for the routing of the NxN optical waveguide grating router according to the entire input / output stage can be constructed as shown in Table 6. Using the channel wavelength combination table determined in Table 6, the path difference of the optical waveguide rows was calculated for a 1.6 nm channel spacing with the standardization movement of the current wavelength division scheme. Table 7 shows the routing table of channel wavelengths applicable to 4x4 and 8x8 optical waveguide grating routers through computerization. This process is applicable to general NxN optical waveguide grating routers. Also, when computing the channel wavelength used, the tolerance range for converging the path difference is ε = 10 Mu m. This tolerance means that the phase difference of the optical waveguide row within the error range within ± 1.2 ° when viewed at the center channel wavelength (1.55 μm). The calculated path difference of the optical waveguide rows is shown in Table 8. This value means the shortest path difference satisfying the wavelength arrangement of Table 7. [

FIG. 5 is a cross-sectional refractive index profile of a unit waveguide considered in computer simulation to verify the feasibility of the present invention. A core layer of 0.35 탆 -InGaAsP (1.2Q) was formed on the InP substrate, and the InP was again grown to form a slab waveguide. In order to provide lateral confinement, a ridge waveguide was formed by etching the upper layer of InP to 0.2 μm. At this time, the index contrast examined by the effective refractive index method is 0.5%.

The FD-BPM (Finite Difference Beam Propagation Method), which is widely used, is used for computer simulation. The optical waveguide grating router was constructed by using the 4x4 and 8x8 multimode interference combiner shown in Table 1 and the optical waveguide row shown in Table 8.

As a result of the simulation, the frequency characteristics of the 4 × 4 optical waveguide grating router and the 8 × 8 optical waveguide grating router are shown in FIGS. 6 and 7, respectively. In the case of the 4x4 optical waveguide grating router, the loss of less than 0.3dB and the loss of 8x8 optical power within the range of the channel wavelength exist in the case where the wavelength of each channel is exactly 1.6nm (200GHz) And a loss of 0.4 dB or less in the case of the waveguide grating router. It can be seen that the loss is remarkably improved compared to about 3 dB radiation loss due to the diffraction of the conventional optical waveguide grating router using the radially formed coupler. Table 9 compares the frequency characteristics of the optical waveguide grating router using the multi-mode interference coupler proposed in this paper and the case of using the radial shaping coupler that was introduced previously. The loss of the NxN optical waveguide grating router composed of the proposed multimode coupler is analyzed as loss due to excess loss generated in the multimode coupler and failure to control a part of the phase of the optical wave according to the tolerance.

In other words, the optical waveguide grating router composed of a radial shaping coupler, which is known in the conventional method, is known to have a radiation loss of about 3-4 dB because of the nature of the device body using the diffracting property of light. However, there is no concrete method to solve this problem. Therefore, a multi-mode interference coupler that is under the spotlight as a low-loss characteristic due to the present invention is selected as a substitute, and optical phase characteristics are analyzed to make a great contribution to the realization of a new low-loss NxN optical waveguide lattice router. The multimode interference coupler used in this study analyzed the relationship between the length and wavelength dependence of a passive device in order to eliminate the wavelength dependence. The structure of the multimode interference combiner was deeply etched to the multimode region in order to reflect the low- As shown in Table 1, the existing multi-mode interference combiner is improved. The design of the optical waveguide column that reflects the frequency characteristics determines the nature of the optical waveguide column to be used in the optical waveguide grating router because it analyzes the phase relationship of the branched waveguide undergoing the optical waveguide heat. We also found the independence of the phase difference set of the light wave in the waveguide row and found the length difference of the optical waveguide column to be actually used by completing the algorithm to predict the channel wavelength array. Since the number of waveguides in the optical waveguide array is the same as the number of input / output stages in the proposed structure, the optical waveguide lattice router composed of the conventional shaping coupler needs about 2-3 times as many waveguides as the number of input / It can be seen that the fabrication process has been simplified because a superior transmission characteristic can be obtained with the number of waveguides remarkably smaller than those arranged in the column.

The present invention provides a low-loss optical waveguide grating router using an NxN multimode interference coupler for a first optical waveguide grating router and a low-loss and wavelength-independent multi-mode interference combiner for forming an optical waveguide grating router. I made a wish. In addition, a general design guideline is provided through the analysis of optical waveguide columns connecting two multi-mode couplers, and the prediction of channel wavelength arrays through the independence of the phase difference set in the optical waveguide columns can effectively shorten the computerized processing time It looked. The design of optical waveguide columns and the design of multimode couplers that are insensitive to low loss and wavelength variations are also applicable to extended input and output stages and are therefore useful for the design of general optical waveguide grating routers. The conventional radial shaping coupler has inherent loss regardless of the number of input / output stages by using diffracted light, whereas the structure of the present invention minimizes loss and enables efficient use of light waves.

It is an object of the present invention to provide a very simple multimode interference NxN optical waveguide grating router with a surplus insertion loss within 0.5 dB by replacing a radial shaping combiner using a multimode coupler with low loss characteristics and a compact structure.

Claims (1)

A NxN optical waveguide grating router comprising: a first NxN multi-mode interference filter having N input terminals for inputting a plurality of channel wavelengths and outputting optical power incident on an arbitrary position to N branched images using a general interference effect; A coupler; N pieces of grating optical waveguide columns for transmitting the branched propagated light waves so as to have different phases according to a path difference of each waveguide; And a second NxN multiplexing step of adjusting the optical waveguide thermal grating so as to focus on a specific position of the output end thereof with N output terminals so that optical powers having respective phase differences are reproduced at a specific position of the output terminal in accordance with a wavelength, Mode interfering coupler, wherein the multi-mode interference type NxN optical waveguide grating router is a simple structure with reduced surplus loss.