阅读说明：本技术 一种温度不敏感的平场型阵列波导光栅路由器 (Temperature-insensitive flat-field type array waveguide grating router ) 是由 何建军 范柱平 于 2021-07-02 设计创作，主要内容包括：本发明公开了一种温度不敏感的平场型阵列波导光栅路由器。它包括输入耦合光纤阵列、输入波导、输入平板波导区、阵列波导区、输出平板波导区、输出波导、输出耦合光纤阵列和温度补偿装置；平场型阵列波导光栅路由器包括平输入场型和平聚焦场型,基于像差理论进行设计；温度补偿装置置于平场型平板波导端的输入或输出波导上,根据温度变化反馈,通过无源或有源的方式使输入或输出波导沿输入或输出面直线移动,以补偿温度的影响,从而实现温度不敏感特性。本发明温度不敏感的平场型阵列波导光栅路由器能够保持良好的线性色散和聚焦效果,而且控制灵活方便,在大规模可重构波分复用系统中具有很高的应用前景。(The invention discloses a flat field type array waveguide grating router insensitive to temperature. The device comprises an input coupling optical fiber array, an input waveguide, an input slab waveguide area, an array waveguide area, an output slab waveguide area, an output waveguide, an output coupling optical fiber array and a temperature compensation device; the flat field type arrayed waveguide grating router comprises a flat input field type and a flat focusing field type, and is designed based on an aberration theory; the temperature compensation device is arranged on an input waveguide or an output waveguide at the flat-field flat-plate waveguide end, and the input waveguide or the output waveguide is linearly moved along an input surface or an output surface in a passive or active mode according to temperature change feedback so as to compensate the influence of temperature, thereby realizing the temperature insensitivity. The flat field type array waveguide grating router insensitive to temperature can keep good linear dispersion and focusing effects, is flexible and convenient to control, and has a very high application prospect in a large-scale reconfigurable wavelength division multiplexing system.)

1. The utility model provides a flat-field type array waveguide grating router insensitive to temperature, is including the input-coupled fiber array (1), array waveguide grating router and the output-coupled fiber array (7) that connect gradually, and array waveguide grating router includes the input waveguide district, input slab waveguide district, array waveguide district (4), output slab waveguide district (5) and the output waveguide district that connect gradually from input-coupled fiber array (1) to output-coupled fiber array (7), its characterized in that: one of the input slab waveguide area (3) or the output slab waveguide area (5) is selected to be a flat field type slab waveguide area, the end surface (101) of the flat field type slab waveguide area on one side close to the arrayed waveguide area (4) is set to be a flat field type structure, and the end surfaces of all input waveguides of the input waveguide area or all output waveguides of the output waveguides (6) connected with the end surface are arranged on the same plane and serve as a cutting surface (103), so that the arrayed waveguide grating router forms a flat field type arrayed waveguide grating router (110); a temperature compensation device (111) is arranged at the cutting surface (103), the temperature compensation device (111) is arranged between the flat field type flat waveguide area and an input waveguide area or an output waveguide area connected with the flat field type flat waveguide area, and the temperature compensation device (111) moves along the cutting surface along with the change of temperature, so that a flat field type arrayed waveguide grating router insensitive to temperature is further formed; and the arrangement of the centers of all the arrayed waveguides in the arrayed waveguide region (4) connected with the flat field type flat waveguide region is not set to be uniformly distributed any more.

2. A temperature insensitive flat field arrayed waveguide grating router according to claim 1, wherein: in the flat-field type arrayed waveguide grating router (110), the end face (102) of an input flat waveguide region (3) or an output flat waveguide region (5) which is used as the flat-field type flat waveguide region and is close to one side of the arrayed waveguide region (4) is set to be of a Rowland circle structure.

3. A temperature insensitive flat field arrayed waveguide grating router according to claim 2, wherein: the flat field type structure of the flat field type array waveguide grating router (110) is divided into a flat input field type and a flat focusing field type:

the flat input field type means that the input slab waveguide area (3) is a flat field type slab waveguide area, and the end surfaces of all input waveguides connected with the flat field type slab waveguide area are positioned on the same plane of a cutting surface (103);

the flat focusing field type means that the output flat waveguide area (5) is a flat field type flat waveguide area, and the end surfaces of the output waveguides connected with the flat field type flat waveguide area are on the same plane of the cutting surface (103).

4. A temperature insensitive flat field arrayed waveguide grating router according to claim 1, wherein: the position arrangement of the centers of all array waveguides in the array waveguide area (4) connected to the end face of the flat field type flat waveguide area is determined by a two-point method, the positions of the centers of all array waveguides connected to the end face of the flat field type flat waveguide area are not uniformly distributed on the end face of the flat field type flat waveguide area, and the centers of every two adjacent array waveguides have the same length difference.

5. A temperature insensitive flat field arrayed waveguide grating router according to claim 1, wherein: the position arrangement of the centers of all array waveguides in the array waveguide region (4) connected to the end face of the flat field type flat waveguide region is determined by a three-point method, the positions of the centers of all array waveguides connected to the end face of the flat field type flat waveguide region are not uniformly distributed on the end face of the flat field type flat waveguide region any more, and the centers of every two adjacent array waveguides do not have fixed length difference any more.

6. A temperature insensitive flat field arrayed waveguide grating router according to claim 1, wherein: according to the change of the environmental temperature, each input waveguide in the input waveguide area or each output waveguide in the output waveguide (6) connected with the flat field type slab waveguide area is driven to synchronously translate along a cutting surface (103) vertical to the extending direction of the waveguides through a temperature compensation device (111), and then the connection and position relation between the flat field type slab waveguide area and the input waveguide area or the output waveguide (6) in the flat field type arrayed waveguide grating router (110) influenced by the environmental temperature is adjusted and changed.

7. A temperature insensitive flat field arrayed waveguide grating router according to claim 1 or 6 wherein: one side of the temperature compensation device (111) is fixedly connected with the input waveguide (2) or the output waveguide (6), and the other side of the temperature compensation device is connected with the input slab waveguide area (3) or the output slab waveguide area (5); the temperature compensation device (111) mainly comprises a fixing part (112), a telescopic rod (113) and an alignment substrate (114), wherein the fixing part (112) is kept fixed, one end of the telescopic rod (113) is fixed on the fixing part (112), the other end of the telescopic rod (113) is fixedly connected with the alignment substrate (114), and the end parts of the input waveguide (2) or the output waveguide (6) are fixed on the alignment substrate (114).

8. A temperature insensitive flat field arrayed waveguide grating router according to claim 1, wherein: the free spectral range FSR of the flat-field type arrayed waveguide grating router (110) is calculated according to the following formula:

FSR＝(λ_cN_w)/(mN_g)＝Δλ·N

wherein λ is_cExpressed as the channel wavelength from the central input waveguide to the central output waveguide in the flat-field type arrayed waveguide grating router, m is the diffraction order, N_wAnd N_gRespectively, the equivalent refractive index and the group refractive index of the arrayed waveguide, Δ λ is the channel spacing, and N represents the input/output wave derivative.

Technical Field

The invention relates to a waveguide grating router structure in the technical field of optical communication, in particular to a flat field type array waveguide grating router insensitive to temperature.

Background

The N × N Arrayed Waveguide Grating Router (AWGR) can simultaneously realize complete non-blocking connection of N × N signals, has the advantages of high integration level, large transmission capacity, small volume, small insertion loss, low cost and the like, and becomes one of key components in an optical interconnection network system.

Most optoelectronic materials used to make AWGR have some thermo-optic effect, which causes the refractive index of the waveguide to change with temperature, causing the center wavelength of each channel to shift. Such shifts can cause greater crosstalk and higher loss, degrading the performance of the AWGR.

In recent years, many proposals have been made by those skilled in the art to realize the temperature insensitive characteristic of the device. Such as by doping or by using a polymer or other temperature compensating material. The method has high requirement on process tolerance and low yield. And a compensation medium with a negative thermo-optic coefficient is inserted into the arrayed waveguide or the slab waveguide region of the AWGR to compensate the change of the optical path difference, but the method increases additional insertion loss and has more difficulty in design and manufacture.

One solution that is relatively easy to implement is based on an integrated wavelength division multiplexing device of the flat field type, which implements the temperature insensitive feature by means of a temperature compensation device, such as the national invention patent (publication: CN 1404253A). The device is realized by a position deviation compensation device. The position offset compensation device is arranged at the output end of the chip, and the position of the output waveguide is controlled in an active and passive mode, so that the offset of the central wavelength of the channel caused by temperature change is compensated. The method is simple and easy to implement. The active mode can adopt micro-displacement actuating mechanisms such as a micro motor, a PZT electrostrictive material, an electrostatic crawling brake, a peristaltic motor and the like, and the position of the output waveguide is controlled by utilizing a digital signal technology; the passive mode does not need electric signal control, and utilizes the thermal expansion effect of specific materials (metal, alloy or plastic and the like) to generate a certain expansion and contraction quantity to control the position of the output waveguide when the environmental temperature changes, so that the central wavelength of the device is kept unchanged.

However, where the wavelength division multiplexer or demultiplexer is an Nx1 or 1xN device, the temperature compensation device can be installed at the input or output of a single waveguide to perform the aberration cancellation for a particular channel wavelength in the (de) multiplexer, and the method has a limited ability to improve the overall aberration of the device, especially in large scale integrated wavelength routing devices. Whereas the AWGR typically has three parameters, up to three channel wavelengths may be allowed to simultaneously resolve aberrations. Moreover, AWGR is an NxN device with many waveguides at both input and output ends, which causes a shift in the focus direction while the dispersion is compensated when the temperature compensated mechanical structure moves.

Disclosure of Invention

Aiming at the defects of the background art and based on the existing technical means, the invention provides a flat-field type arrayed waveguide grating router insensitive to temperature, which solves the problem that the arrayed waveguide grating router causes the central wavelength to shift due to the change of the environmental temperature.

The technical scheme adopted by the invention is as follows:

as shown in fig. 3, the optical fiber array comprises an input coupling optical fiber array, an arrayed waveguide grating router and an output coupling optical fiber array which are connected in sequence, wherein the arrayed waveguide grating router comprises an input waveguide region, an input slab waveguide region, an arrayed waveguide region, an output slab waveguide region and an output waveguide region which are connected in sequence from the input coupling optical fiber array to the output coupling optical fiber array, the input waveguide region is formed by a plurality of input waveguides, and the output waveguide region is formed by a plurality of output waveguides; the number of the input waveguides and the number of the output waveguides are both N, and the N is the same as the number of channels in the arrayed waveguide grating router.

As shown in fig. 1 and 2, one of the input slab waveguide region or the output slab waveguide region is set to be a flat-field structure and used as a flat-field slab waveguide region, an end surface of the flat-field slab waveguide region on a side close to the arrayed waveguide region is set to be a flat-field structure, end surfaces of the input waveguides or the output waveguides of the input waveguide region connected with the end surface are set to be in the same plane and used as a cutting surface, so that the arrayed waveguide grating router forms a flat-field arrayed waveguide grating router and is further used for being connected to the input slab waveguide region or the output slab waveguide region, and thus the cutting surface of the chip can be moved to the cutting surface. And the arrangement of the centers of all the arrayed waveguides in the arrayed waveguide region connected with the flat field type flat waveguide region is not set to be uniformly distributed any more.

The temperature compensation device is arranged at the cutting surface, the temperature compensation device is arranged between the flat field type flat waveguide area and the input waveguide area or the output waveguide area connected with the temperature compensation device, the temperature compensation device moves along the cutting surface along with the change of the temperature, namely, one position is selected from the input side or the output side, one side position is selected from the input waveguide area and the input flat waveguide area or the output flat waveguide area to be provided with the temperature compensation device, and the flat waveguide area at the position of one side is arranged to be of a flat field type structure, so that the flat field type arrayed waveguide grating router insensitive to the temperature is further formed.

The temperature compensation device and the input or output waveguide connected with the temperature compensation device are separated from the flat-field type arrayed waveguide grating router chip, namely the temperature compensation device belongs to the peripheral design of the flat-field type arrayed waveguide grating router chip, and the temperature compensation control mechanism is flexible and convenient.

In the planar field type arrayed waveguide grating router, the end face of the input planar waveguide region or the output planar waveguide region serving as the planar field type planar waveguide region on one side close to the arrayed waveguide region is arranged and kept in a standard Rowland circle structure, and the specific implementation can be realized by arranging each input port or output port in the arrayed waveguide region connected with the end face on the Rowland circle or in a confocal structure.

Fig. 2 shows the input slab waveguide region as a flat-field slab waveguide region, and fig. 1 shows the output slab waveguide region as a flat-field slab waveguide region.

The flat field type structure of the flat field type array waveguide grating router is divided into a flat input field type and a flat focusing field type:

the flat input field type means that the end surfaces of all input waveguides or the end surfaces of all output waveguides connected with the flat field type flat waveguide region are positioned on the same plane, and the input flat waveguide region or the output flat waveguide region which is not used as the other side of the flat field type flat waveguide region is still in a traditional Rowland circle structure;

the flat focusing field type means that output signals of each input waveguide or each output waveguide connected with the flat field type flat waveguide region are focused on the same plane, and the input flat waveguide region or the output flat waveguide region which is not used as the other side of the flat field type flat waveguide region is still in a traditional Rowland circle structure.

The position arrangement of the centers of all array waveguides in the array waveguide region connected with the flat field type slab waveguide region and connected with the end face of the flat field type slab waveguide region is determined by a two-point method, the positions of the centers of all array waveguides connected with the end face of the flat field type slab waveguide region are not uniformly distributed on the end face of the flat field type slab waveguide region, and the centers of every two adjacent array waveguides have the same length difference.

The position arrangement of the centers of all array waveguides in the array waveguide region connected with the flat field type slab waveguide region and connected with the end face of the flat field type slab waveguide region is determined by a three-point method, the positions of the centers of all array waveguides connected with the end face of the flat field type slab waveguide region are not uniformly distributed on the end face of the flat field type slab waveguide region, and a fixed length difference is not formed between the centers of every two adjacent array waveguides.

According to the change of the environmental temperature, each input waveguide in the input waveguide region or each output waveguide in the output waveguide connected with the flat field type slab waveguide region is driven by the temperature compensation device to synchronously translate along a cutting surface vertical to the extending direction of the waveguide, so that the connection and position relation between the flat field type slab waveguide region and the input waveguide region or the output waveguide in the flat field type arrayed waveguide grating router influenced by the environmental temperature is adjusted and changed to compensate the influence of the temperature, and the temperature insensitivity characteristic is realized. The input optical signals received by each input waveguide connected with the flat-field slab waveguide area are not changed before and after being influenced by the ambient temperature, and the input optical signals sent by each output waveguide are not changed before and after being influenced by the ambient temperature

As shown in fig. 10, the temperature compensation device is disposed in a flat plane in the flat-field type arrayed waveguide grating router, and one side of the temperature compensation device is connected to the input waveguide or the output waveguide, and the other side of the temperature compensation device is connected to the input slab waveguide region or the output slab waveguide region; the temperature compensation device mainly comprises a fixing part, a telescopic rod and an alignment substrate, wherein the fixing part is kept fixed, one end of the telescopic rod is fixed on the fixing part, the other end of the telescopic rod is fixedly connected with the alignment substrate, the end parts of the input waveguides or the output waveguides are fixed on the alignment substrate and are arranged on a cutting surface, and the end surfaces of the input waveguides or the output waveguides are aligned through a plane aligned with the surface of the alignment substrate to form a flat field type structure.

The telescopic rod is made of a material which deforms under the change of temperature, in particular a material which lengthens or retracts along a cutting surface under the change of temperature. The amount of expansion and contraction caused by the change in unit temperature of the telescopic rod is related to the coefficient of thermal expansion of the material itself and the length thereof. According to the change of the environmental temperature, the temperature compensation device drives each input waveguide or output waveguide connected with the flat field type flat waveguide area to synchronously translate along a cutting surface vertical to the extension direction of the waveguide, so that the relative positions of each input waveguide or output waveguide connected with the flat field type flat waveguide area and an input or focused output signal can be matched.

The temperature compensation device is deformed according to the temperature change feedback of the chip, and the input waveguide or the output waveguide is driven to move in a translation mode along the cutting surface in a passive (or active) mode so as to compensate the offset caused by the temperature influence, thereby realizing the temperature insensitivity characteristic.

Therefore, the invention realizes the setting and control of the temperature offset compensation of the flat-field type array waveguide grating router by selecting the materials and the lengths of the telescopic rods with different thermal expansion coefficients and arranging the centers of all the array waveguides of the array waveguide region connected with the flat-field type flat waveguide region.

The free spectral range FSR of the flat-field type array waveguide grating router has the following calculation formula:

FSR＝(λ_cN_w)/(mN_g)＝Δλ·N

wherein λ is_cExpressed as the channel wavelength from the central input waveguide to the central output waveguide in the flat-field type arrayed waveguide grating router, m is the diffraction order, N_wAnd N_gRespectively, the equivalent refractive index and the group refractive index of the arrayed waveguide, Δ λ is the channel spacing, and N represents the input/output wave derivative.

The flat-field type array waveguide grating router is suitable for design and manufacture of material platforms based on silicon dioxide, silicon nitride, silicon on insulator, indium phosphide and the like.

On the basis of a standard Rowland circular arrayed waveguide grating router, the invention keeps one of an input slab waveguide area or an output slab waveguide area still in a standard Rowland circular shape, and sets the output or input end surface connected with the other slab waveguide area as a plane (namely a cutting surface) which respectively corresponds to a flat focusing field type and a flat input field type arrayed waveguide grating router. And the input waveguide or the output waveguide connected at the cutting surface is placed in a temperature compensation device.

The flat field type array waveguide grating router insensitive to temperature can keep good linear dispersion and focusing effects, is flexible and convenient to control, and has a very high application prospect in a large-scale reconfigurable wavelength division multiplexing system.

The invention has the beneficial effects that:

the invention designs the flat field type array waveguide grating router insensitive to temperature by using the aberration theory on the basis of not increasing extra loss, not reducing device crosstalk, not introducing extra temperature compensation medium and not increasing process manufacturing difficulty.

The two-point method and the three-point method are adopted, so that the aberration of each channel of the flat-field type arrayed waveguide grating router is reduced, the device can keep good linear dispersion and focusing effects, and the performance of the device is improved and guaranteed.

The flat field type array waveguide grating router insensitive to temperature separately designs the temperature compensation control device and the flat field type array waveguide grating router chip, has flexible and convenient compensation mechanism, and has very high application prospect in a large-scale reconfigurable wavelength division multiplexing system.

Drawings

FIG. 1 is a schematic diagram of an arrangement of a flat input field type arrayed waveguide grating router of the present invention that is temperature insensitive;

FIG. 2 is a schematic diagram of the flat-focus field-type arrayed waveguide grating router of the present invention;

FIG. 3 is a design layout of a standard Rowland circular arrayed waveguide grating router;

FIG. 4 is a schematic structural diagram of a flat-focus field-type arrayed waveguide grating router;

FIG. 5 is a schematic diagram of the position distribution of the slab waveguide region of the arrayed waveguide designed based on the two-point method and the three-point method according to the present invention;

FIG. 6 is a graph showing aberration of the present invention at a central input waveguide;

FIG. 7 is a graph comparing the variation curves of the relative length difference of the arrayed waveguides of the present invention based on a three-point method and a standard Rowland circle design;

FIG. 8 is a transmission spectrum at the incidence of the center input waveguide CH #8 and the edge input waveguide CH #16 when designed based on a two-point approach;

fig. 9 is a transmission spectrum at the incidence of the center input waveguide CH #8 and the edge input waveguide CH #16 when designed based on the three-point method.

Fig. 10 is a diagram of a temperature compensation device employing a passive system.

In the figure, an input coupling optical fiber array 1, a flat field type arrayed waveguide grating router 110, an output coupling optical fiber array 7, an input waveguide 2, an input slab waveguide area 3, an arrayed waveguide area 4, an output slab waveguide area 5, an output waveguide 6, a cutting surface 103, an inlet arrayed waveguide 101, an outlet arrayed waveguide 102, a temperature compensation device 111, a fixing part 112, an expansion link 113 and an alignment substrate 114.

Detailed Description

The invention is described in further detail below with reference to the figures and the embodiments.

In general, the refractive index of the waveguide will change with temperature, which will affect the focus position of the original central wavelength of the AWGR, and can be explained by the grating diffraction equation:

N_sd_a(sinθ_i+sinθ_o)+N_wΔL＝mλ

wherein N is_sAnd N_wEquivalent refractive indices of slab waveguide region and arrayed waveguide, d_aFor spacing of adjacent arrayed waveguides in the slab region, theta_iAnd theta_oIs the diffraction angle of the signal in the input slab waveguide region and the output slab waveguide region, and Δ L is the length difference between adjacent arrayed waveguides. m is the diffraction order and λ is the vacuum channel wavelength.

The equation of the grating diffraction is differentiated to obtain the value of theta_i＝θ_oNear 0, the rate of change of the focus (or diffraction) position with wavelength is: dx/d λ ═ R Δ LN_g/(N_sd_aλ_c) Where x represents the focal position of the signal perpendicular to the direction of extension of the output waveguide. R represents the length of the slab waveguide region, λ_cIs the center wavelength from the center input waveguide to the center output waveguide. When theta is_i＝θ_oWhen equal to 0, corresponds to the central wavelength λ_cThe diffraction equation is simplified to N_w0ΔL＝mλ_cIn which N is_w0For arrayed waveguides at a central wavelength λ_cThe equivalent refractive index of (d). The two-sided differential yields the dispersion coefficient as: d lambda/dN_w0＝λ_c/N_w0。

The derivative C of the equivalent refractive index of the waveguide with temperature is assumed to be constant, i.e. dN_wC, the rate of change dx/dT of the signal with temperature at the focal center position perpendicular to the extension direction of the output waveguide can be derived as:

dx/dT＝(dx/dλ)*(dλ/dN_w)*dN_w/dT＝RΔLN_g/(N_sd_aN_w0)*C

wherein N is_gT represents the ambient temperature, which is the group index of the arrayed waveguides.

Therefore, the change rate of the AWGR signal along with the change of the focus position perpendicular to the extension direction of the output waveguide and the ambient temperature is in linear relation with the derivative of the equivalent refractive index of the waveguide to the temperature.

Taking a silica waveguide as an example, the derivative C of the equivalent refractive index with temperature is usually 8-10 x10^-6K, where C is 10^-5and/K, the coefficient of the change of the center position of the signal focus output with temperature is obtained as dx/dT equal to 0.23um/K based on the design parameters of the silica AWGR with reference to table 1 below. .

That is, for every 1K change in ambient temperature, the silica-based AWGR signal is shifted by 0.23um in the focus position perpendicular to the direction of extension of the output waveguide. If the output waveguide end face (or the input waveguide end face) connected with the slab waveguide region is designed into a plane to be used as a planar arrayed waveguide grating router AWGR, and the output waveguide (or the input waveguide) is driven by a certain device to synchronously translate along the plane along with the temperature change (for example, the output waveguide (or the input waveguide) translates by 0.23um every 1-degree temperature difference), the original channel wavelength will be normally output from the original output waveguide, so that the wavelength drift of the AWGR caused by the temperature change is compensated, and the problem of central wavelength shift of the arrayed waveguide grating router caused by the environmental temperature change is solved.

The invention is further described below with respect to the design of a planar waveguide grating router by way of a specific example.

For convenience of explanation, silicon dioxide (SiO) is used herein as the basis₂) The material platform takes a flat focusing field type arrayed waveguide grating router as an example to explain a design method. The flat input field type arrayed waveguide grating router is a structure completely symmetrical with the flat input field type arrayed waveguide grating router, and the same design method can be adopted. The method is also suitable for designing and manufacturing material platforms such as silicon nitride, silicon on insulator, indium phosphide and the like.

The structural parameters of a 16 × 16 standard rowland circular AWGR were first designed and optimized based on a silica-based silicon dioxide material platform, where table 1 lists the specific design parameters.

TABLE 116 × 16 Main design parameters of the Standard Rowland round AWGR

The layout topography for designing a 16 × 16 standard rowland circular AWGR is shown in fig. 3 according to the main parameters in table 1. The standard rowland circular AWGR is designed based on a rowland circular structure, all input waveguide ports and focus output waveguide ports are located on a rowland small circular arc, and the positions of the centers of each array waveguide at the inlet array waveguide 101 and the outlet array waveguide 102 are arranged on a rowland large circular arc at equal intervals, and the length difference of adjacent array waveguides is a constant and has complete axial symmetry. Such a rowland circular structure has been proved to satisfy the second-order imaging condition, and is one of the most preferable structures from the viewpoint of eliminating the full-band aberration.

The flat-field type arrayed waveguide grating router insensitive to temperature sets the end surface of an input waveguide or an output waveguide connected with one of an input flat waveguide region 3 or an output flat waveguide region 5 as a plane, and takes the flat waveguide region where the cutting surface 103 is positioned as a flat-field type flat waveguide region, wherein the end surface of the input waveguide or the output waveguide is used as a cutting surface 103 of the flat-field type arrayed waveguide grating router 110. When the input waveguide port or the focused output waveguide port is not on the small rowland arc, but on the same plane, as shown in fig. 1-2 and 4, it is imperative to influence the imaging conditions of the AWGR.

In order to reduce the aberration of each channel of the flat field type AWGR and improve the overall performance of the device, only one side of the input flat waveguide area or the output flat waveguide area is designed into the flat field type flat waveguide area. Based on aberration theory, by adopting a Stigmatic Points design method, the aberration of several key channel wavelengths is completely eliminated by properly adjusting the space and the position between the adjacent arrayed waveguides on the inlet arrayed waveguide (101) or the outlet arrayed waveguide 102 and the length difference of the adjacent arrayed waveguides. Considering that the maximum number of parameters to be adjusted is only three, the aberration of at most three channel wavelengths can be eliminated.

As shown in fig. 4, the flat-focus field-type arrayed waveguide grating router includes an input waveguide 2, an input slab waveguide region 3, an arrayed waveguide region 4, and an output slab waveguide region 5. The optical signals are incident from the input waveguide 2 to the input slab waveguide area 3, are diverged to the inlet arrayed waveguide 101 based on kirchhoff diffraction, are transmitted through arrayed waveguides with different lengths in the arrayed waveguide area 4, and reach the position of the outlet arrayed waveguide 102, and finally, the optical signals with different wavelengths are focused at different positions of the same output plane 103 due to interference.

Based on the symmetry, rectangular coordinates YOZ and Y ' O ' Z ' as shown in FIG. 4 are established in the input slab waveguide region and the output slab waveguide region. Where the origin O and O ' are located at the center of the inlet arrayed waveguide 101 and the outlet arrayed waveguide 102 (i.e., one arrayed waveguide at the center in the arrayed waveguide region 4), respectively, as the origin of coordinates, and the Y or Y ' axis and the Z or Z ' axis are perpendicular and parallel to the normal line of the inlet arrayed waveguide 101 or the outlet arrayed waveguide 102, respectively.

Defining the optical path function as:

F(w，λ)＝N_s(|SP(w)|+|P′(w)D|)+N_wL(w)-mλG(w)

wherein F (w, λ) represents an optical path length function of w-th arrayed waveguide in the arrayed waveguide region 4 of the optical signal having the wavelength λ, w is the number of arrayed waveguides in the arrayed waveguide region 4, and w is 1,2, …, N_wgAnd S and D are the position of a signal input port of the flat-field type arrayed waveguide grating router (110) and the position of signal output focusing imaging of the flat-field type arrayed waveguide grating router (110), wherein the coordinate of D on the Z axis is a constant. P (w) and P' (w) indicate the position of the center of the arrayed waveguide w in the input/output slab waveguide region, l (w) indicates the length of the arrayed waveguide w, g (w) indicates the number of arrayed waveguides from P (w) to the center arrayed waveguide (P (0,0)), and g (w) is 0 for the center arrayed waveguide. P (0,0) is at the origin O; n is a radical of_wRepresenting the equivalent refractive index of the arrayed waveguide. N is_sRepresenting the equivalent refractive index of the input/output slab waveguide region. λ represents the vacuum channel wavelength.

The aberration (optical path difference) function is defined as the following expression:

ΔF(w,λ)＝N_s(|SP(w)|-|SO|+|P′(w)D|-|DO′|)+N_w(L(w)-L(O))-mλG(w)

where Δ F (w, λ) represents the difference in optical path length function between the w-th arrayed waveguide and the central arrayed waveguide in the arrayed waveguide region 4 for an optical signal having a wavelength λ. O denotes a position of one arrayed waveguide at the center in the arrayed waveguide region 4 at the inlet arrayed waveguide 101, i.e., the origin O of the YOZ coordinate system, and O 'denotes a position of one arrayed waveguide at the center in the arrayed waveguide region 4 at the outlet arrayed waveguide 102, i.e., the origin O' of the Y 'OZ' coordinate system. The Z-axis of the YOZ coordinate system is along the waveguide extending direction, and the Y-axis is along the waveguide array arrangement direction of the inlet array waveguide 101.

Among these, for the standard rowland round AWGR, there is l (w) ═ N (w-N)_halfwg) x.DELTA.L + L (O), L (O) and N_halfwgRespectively, the length and number of one arrayed waveguide in the center of the arrayed waveguide region 4.

Example 1

The flat-field type arrayed waveguide grating router is designed by adopting a two-point method (2 static points).

As shown in fig. 4, keeping the standard rowland circle of the input slab waveguide region unchanged (i.e., p (w)) and first step giving the position S of the initial input waveguide where the central input waveguide CH #8 (which may not be the central input waveguide) is selected; two wavelengths λ 1 and λ 2 are then selected (λ 1 ═ 1.5374 μm and λ 2 ═ 1.5461 μm in this example) for which aberration cancellation is desired, assuming that λ 1 and λ 2 are imaged at D1 and D2 of the focal plane along the diffraction angles of the original grazing circle AWGR (as in fig. 3), where the coordinates of D1 and D2 on the Z 'axis are the same (Z' ═ R).

Because the length of the arrayed waveguide is not changed by the two-point method (i.e., L (w)) is kept unchanged, for each arrayed waveguide, the optical path difference function between the centers of the adjacent arrayed waveguides should satisfy the following equation set:

wherein, Δ F (w, λ)₁) Denotes the wavelength λ₁The aberration function of the w-th arrayed waveguide in the arrayed waveguide region; Δ F (w, λ)₂) Denotes the wavelength λ₂The aberration function of the w-th arrayed waveguide in the arrayed waveguide region; n is a radical of_S1，N_S2Respectively, the input/output slab waveguide regions at a wavelength of λ₁And λ₂Equivalent refractive index of time, N_w1、N_w2Respectively, indicate the wavelength of the arrayed waveguide is lambda₁And λ₂The equivalent refractive index of the glass; d1 and D2 each represent λ₁And λ₂The diffraction angles along the original standard rowland circle AWGR (see fig. 3) are imaged at the location of the focal plane. Lambda [ alpha ]₁And λ₂Corresponding to two different channel wavelengths.

For each array wave, the above equation system is solved in turn, and the position distribution P' (w) of the centers of the array waveguides of the exit array waveguide 102 is determined, which is not a uniform distribution at equal intervals any more, as shown in fig. 5 (a). The distribution of the positions of the centers of the respective arrayed waveguides of the outlet arrayed waveguide 102 determined by the two-point method is slightly different from the distribution of the positions of the centers of the respective arrayed waveguides of the outlet arrayed waveguide 102 of the standard rowland circle AWGR.

Then imaging the plane in Z ═ R, where R denotes the length of the slab waveguide regionAnd (4) degree. Determining other channel wavelengths lambda_iImaging point D of_i。D_iThe position is selected to satisfy the condition that the maximum absolute value aberration value is minimum in all the arrayed waveguides.

Then, it is assumed that a certain imaging point Do (here, the central imaging point CH #8) is used as an input point, and propagation is reversed, and an imaging point D is determined_iThe positions of the end faces of other input waveguides are determined by the same method as the method of the invention, wherein the positions of the end faces of the input waveguides are distributed on the original Rowland circle.

So far, all parameters of the flat focusing field type arrayed waveguide grating router based on the two-point method are determined. FIG. 6(a) shows the aberration curve of the present example when input from the central input waveguide CH #8, and the aberration Δ F < 0.05 λ of the flat-field type arrayed waveguide grating router designed by the two-point method satisfies the ideal imaging condition Δ F < 0.25 λ.

Example 2

The flat-field type arrayed waveguide grating router is designed by adopting a three-point method (3 static points).

The three-point method is the same as the two-point method in example 1 for designing the flat-field type arrayed waveguide grating router, except that the position P' (w) of the center 101 of the exit arrayed waveguide and the relative length L (w) of the arrayed waveguide region 4 are composed of 3 aberration-free points λ₁、λ₂And λ₃Determined together, λ is chosen in this example₁＝1.5374μm、λ₂1.5421 μm and λ₃1.5461 μm. Namely, the following three equations are connected in sequence to solve the values of P' (w) and l (w).

Wherein, Δ F (w, λ)₁) Denotes the wavelength λ₁The aberration function of the w-th arrayed waveguide in the arrayed waveguide region; Δ F (w, λ)₂) Denotes the wavelength λ₂The aberration function of the w-th arrayed waveguide in the arrayed waveguide region; Δ F (w, λ)₃) Denotes the wavelength λ₃The aberration function of the w-th arrayed waveguide in the arrayed waveguide region; n is a radical of_S1、N_S2、N_S3Respectively, indicate the wavelength of the arrayed waveguide is lambda₁、λ₂And λ₃Equivalent refractive index of time, N_w1、N_w2、N_w3Respectively, indicate the wavelength of the arrayed waveguide is lambda₁、λ₂And λ₃The equivalent refractive index of the film. D₁、D₂、D₃Respectively represent lambda₁And λ₂The diffraction angle along the original standard Rowland circle AWGR (see FIG. 3) is imaged at the position of the focal plane, λ₁、λ₂And λ₃Respectively three different channel wavelengths.

Fig. 5(b) and 7 show the distribution of the individual arrayed waveguide positions P' (w) in the exit arrayed waveguide 102 and the length l (w) -l (o) of the arrayed waveguide w in the arrayed waveguide region 4 with respect to one array at the center, respectively, for this example compared to a standard rowland circular AWGR. The distribution of each arrayed waveguide in the outlet arrayed waveguide 102 is different by 80 μm from that of the original standard rowland circular AWGR, and the arrayed waveguides at the outermost edge are not uniformly distributed on the outlet arrayed waveguide 102 any more; the relative length of the arrayed waveguide no longer increases linearly with the arrayed wave derivative (w).

The flat field AWGR designed by the three-point method achieves lower aberrations (3.1 × 10) than the two-point method^-4A/λ, increased by about 2 orders of magnitude), as shown in fig. 6 (b).

Fig. 8 and 9 show the results of the spectrum simulation of the flat-field arrayed waveguide grating designed by the two-point method and the three-point method with respect to the central input waveguide CH #8 and the edge input waveguide CH #16, respectively. Table 2 lists the main performance parameters in the simulation results.

TABLE 2 comparison of Performance of the present invention Flat field AWGR with the Standard Rowland round AWGR

From simulation results, the flat-field type arrayed waveguide grating router based on the two-point method and the three-point method can keep good linear dispersion and focusing effects. The flat field AWGR designed by the three-point method has lower loss and larger 3dB bandwidth, and the performance of the flat field AWGR is closer to that of a standard Rowland round AWGR.

It should be noted that the two-point method is simpler in layout. Meanwhile, the position S of the initial input waveguide and the wavelength lambda of the optical aberration to be eliminated are reasonably selected, so that the method is very key for further reducing the integral aberration of the device and improving the performance of the device.

As for the temperature compensation device, a passive temperature compensation mechanism is taken as an example. As shown in fig. 10, the alignment substrate 114 holds all the input (flat input field type 2) or output waveguides (flat output field type 6) against the cutting surface 103. The fixed part 112 and the AWGR chip 110 of the present invention are fixed in relative position. The fixing member 112 and the alignment substrate 114 are selected from materials having the same or similar thermal expansion coefficient as the AWGR chip, so that the influence of thermal expansion and contraction on the compensation displacement can be ignored.

The expansion link 113 is made of a specific material, such as metal, alloy or plastic, and utilizes its thermal expansion or thermal contraction effect to generate a certain amount of expansion amount to control the translation of the alignment substrate 114 in the cutting surface 103 when the ambient temperature changes, so as to drive the input (flat input field type 2) or output (flat output field type 6) waveguide to translate along the input or output end surface. If the amount of expansion of the expansion link 113 is just enough to match the displacement required by the AWGR, i.e. the expansion coefficient η of the expansion link 113 is equal to the coefficient dx/dT of the change of the central position of the AWGR with temperature, the central wavelength of the device remains unchanged.

The material has a coefficient of expansion η that is related to the length L and the coefficient of thermal expansion α of the material, and approximately satisfies η ═ α L. Therefore, the design of the telescopic rod 113 is very flexible, and the required length can be determined after selecting a specific material, or the required length can be determined after selecting a specific material, and the size of the device and the existing material are considered in practical application. The following table gives the coefficients of thermal expansion for common materials:

TABLE 3 thermal expansion coefficients of common materials

As above, the coefficient dx/dT of the silica-based waveguide with respect to the change in the center position of the AWGR with temperature is 0.23 (um/K). If the telescopic rod 113 is made of aluminum material, the required length is approximately 9.7 mm.

Finally, the chip 110 of the flat-field type arrayed waveguide grating router, the temperature compensation device 111, the input optical fiber array 1 and the output optical fiber array 7 are combined and packaged together, and the overall design of the flat-field type arrayed waveguide grating router insensitive to temperature can be completed, as shown in fig. 1 and fig. 2.

The embodiments of the present invention of the temperature insensitive flat field type arrayed waveguide grating router are described in detail above with reference to the accompanying drawings. It should be noted that the above-mentioned embodiments illustrate rather than limit the invention, and that any modifications and changes made within the spirit of the invention and the scope of the appended claims are intended to fall within the scope of the invention.