A high-symmetry large-bandwidth flexible arrayed waveguide grating chip for a bragg fiber grating demodulation system

Abstract

This invention relates to a highly symmetric, wide-bandwidth flexible arrayed waveguide grating chip for FBG demodulation systems, belonging to the field of planar optical waveguide device technology. It comprises a polymer flexible substrate, a polymer lower cladding, a polymer waveguide core, and a polymer upper cladding. The refractive indices of the polymer upper and lower cladding materials are lower than those of the polymer waveguide core material. The polymer waveguide core is an optical waveguide structure integrated from two AWG and two MMI units. This invention solves the defects of existing arrayed waveguide gratings in FBG demodulation systems, such as demodulation blind zones and unidirectional transmission. It achieves demodulation with a wide dynamic range and high resolution for reflected wavelengths and supports bidirectional signal input and output at both ports, improving system flexibility. Furthermore, the use of polymer materials to fabricate optical waveguide devices offers significant advantages over inorganic material systems, including better flexibility, simpler processing, lower cost, and higher efficiency, making it suitable for dynamic deformation environments or bio-integrated scenarios.

Description

Technical Field

[0001] This invention belongs to the field of planar optical waveguide device technology, specifically relating to a highly symmetric, large-bandwidth flexible arrayed waveguide grating chip for Bragg fiber grating (FBG) demodulation systems. Background Technology

[0002] As a breakthrough technology in the field of photoelectric sensing, Bragg fiber grating sensors possess significant technological advantages in areas such as distributed monitoring networks, deformation detection of industrial facilities, oil and gas pipeline monitoring, and safety monitoring of power facilities, thanks to their small size, strong corrosion resistance, and excellent electromagnetic interference resistance. Among these, the FBG demodulation system based on arrayed waveguide gratings (AWGs), as the core equipment of fiber optic sensors, has been widely applied in related fields.

[0003] FBG demodulation systems utilize the powerful wavelength division multiplexing (WDM) capability of AWG chips to diffract the reflected light from the FBG onto different output channels of the AWG, demodulating multiple sensor signals simultaneously. The corresponding FBG center wavelength is then obtained based on the intensity ratio of the output signals from adjacent channels of the AWG chip, offering advantages such as high precision and high speed. However, due to the limitations of the spectral transmission characteristics of AWGs, when the center wavelength of the FBG reflection is close to the center wavelength of the AWG channel, only one channel can output optical power, resulting in a demodulation blind zone and preventing the simultaneous achievement of wide dynamic range and high resolution. Furthermore, existing AWG demodulation methods are unidirectional, lacking flexibility, and the materials used to fabricate AWG devices are mainly inorganic rigid material systems, including silicon nitride, III-V compound semiconductors, and silicon-on-insulator, limiting the practical application scenarios of AWG devices in FBG demodulation systems. Summary of the Invention

[0004] This invention addresses the shortcomings of existing FBG demodulation systems, such as unidirectional transmission of AWG devices and the existence of demodulation blind zones, by proposing a highly symmetric, large-bandwidth flexible array waveguide grating chip for FBG demodulation systems.

[0005] This invention proposes a highly symmetric, wide-bandwidth flexible arrayed waveguide grating chip. Based on a polymer material platform, the device possesses a certain degree of flexibility. By integrating two wavelength-independent one-to-two multimode interferometers (MMIs) and two spectrally adjacent AWGs, it achieves a highly symmetric structure, allowing for flexible interchangeability of the input and output ports. Furthermore, it effectively expands the operating bandwidth and eliminates the demodulation blind zone problem present in traditional designs. This device has significant application prospects.

[0006] This invention integrates two identical AWGs and two identical 1×2MMI structures. Each AWG has N output channels, and the center wavelength of each output channel in the right AWG is designed to lie between the center wavelengths of the corresponding two adjacent output channels in the left AWG. During device operation, light of a specific wavelength reflected by the FBG sensor is input from any one of the 1×2MMIs and then uniformly split into two paths entering the left and right AWGs. Based on the known mathematical relationship between the logarithmic ratio of the light intensity between adjacent output channels of the two AWGs and the center wavelength of the light reflected by the FBG sensor, the center wavelength value reflected by the sensor is demodulated. This invention solves the demodulation blind zone and unidirectional transmission defects of existing arrayed waveguide gratings in FBG demodulation systems, achieving wide dynamic range and high-resolution demodulation of reflected wavelengths, and supporting bidirectional signal input and output at both ports, significantly improving system flexibility. Furthermore, optical waveguide devices made of polymer materials have significant advantages over inorganic material systems, such as good flexibility, simple processing, low cost, and high efficiency, making them particularly suitable for dynamic deformation environments or bio-integrated scenarios. This device exhibits excellent flexibility and adaptability during operation, effectively solving the problems of narrow dynamic detection range and insufficient accuracy in existing technologies, and has broad prospects for practical applications.

[0007] The technical solution adopted by this invention to solve its technical problem is as follows:

[0008] The present invention discloses a highly symmetric, large-bandwidth flexible arrayed waveguide grating chip for FBG demodulation systems, as shown in the attached figure. Figure 1 (correspond Figure 2 As shown in the cross-sectional view (A-A'), from bottom to top, the structure consists of a polymer flexible substrate 41, a polymer lower cladding layer 42, a polymer waveguide core layer 43, and a polymer upper cladding layer 44. The polymer waveguide core layer 43 and the polymer upper cladding layer 44 are both located on top of the polymer lower cladding layer 42, and the polymer waveguide core layer 43 is completely encapsulated within the polymer upper cladding layer 44. The effective refractive index of the polymer waveguide core layer is higher than that of the polymer upper and lower cladding layers. This invention fully leverages the advantages of polymer materials, such as good flexibility, diverse selection, and low loss. It can be further combined with doping modification technology to improve material performance, making it particularly suitable for dynamic deformation environments or bio-integration scenarios. Furthermore, the fabrication process of this invention is simple, low-cost, and compatible with semiconductor technology, facilitating integration and large-scale production, and possesses significant practical value.

[0009] The structure of polymer waveguide core layer 43 is shown in the attached figure. Figure 2As shown, it consists of a first 1×2 MMI unit 8, a second 1×2 MMI unit 38, a left AWG, and a right AWG. The first 1×2 MMI unit 8 and the second 1×2 MMI unit 38 have the same dimensions and structure and are symmetrically arranged front to back. The left AWG and right AWG have the same dimensions and structure and are symmetrically arranged left to right about the first 1×2 MMI unit 8 and the second 1×2 MMI unit 38. The entire device has central symmetry. The first 1×2 MMI unit 8 consists of a first 1×2 MMI unit input single-mode straight waveguide 1 and a first 1×2 MMI unit input linear cone connected in sequence. The second 1×2MMI unit consists of waveguide 2, a first 1×2MMI unit multimode planar waveguide 3, a first 1×2MMI unit first output linear tapered waveguide 4 and a first 1×2MMI unit second output linear tapered waveguide 6 with the same dimensions and structure, a first 1×2MMI unit first output bent waveguide 5 and a first 1×2MMI unit second output bent waveguide 7 with the same dimensions and structure; the second 1×2MMI unit 38 is composed of a second 1×2MMI unit input single-mode straight waveguide 31, a second 1×2MMI unit input linear tapered waveguide 32, and a second 1×2MMI unit multimode planar waveguide 38 connected in sequence. The left AWG consists of a plate waveguide 33, a second 1×2 MMI unit with identical dimensions and structure, a first output linear tapered waveguide 34 and a second 1×2 MMI unit with identical dimensions and structure, a first output bent waveguide 35 and a second 1×2 MMI unit with identical dimensions and structure, and a second output bent waveguide 37; the left AWG consists of a first output waveguide array 11 and a second output waveguide array 27 with identical dimensions and structure and N waveguide numbers, a first linear tapered waveguide array 13 and a second linear tapered waveguide array 25 with identical dimensions and structure and N waveguide numbers. The array consists of a first planar waveguide 15 and a second planar waveguide 23 with identical dimensions and structure, a third linear tapered waveguide array 17 and a fourth linear tapered waveguide array 21 with identical dimensions and structure and a waveguide number n>N, and a first curved waveguide array 19 with a waveguide number n>N. The first output waveguide array 11, the first linear tapered waveguide array 13, the first planar waveguide 15, the third linear tapered waveguide array 17, the first curved waveguide array 19, the fourth linear tapered waveguide array 21, the second planar waveguide 23, the second linear tapered waveguide array 25, and the second output waveguide array 27 are connected sequentially.The right AWG consists of a third output waveguide array 12 and a fourth output waveguide array 28 with the same dimensions and structure and a waveguide number of N; a fifth linear tapered waveguide array 14 and a sixth linear tapered waveguide array 26 with the same dimensions and structure and a waveguide number of N; a third planar waveguide 16 and a fourth planar waveguide 24 with the same dimensions and structure; a seventh linear tapered waveguide array 18 and an eighth linear tapered waveguide array 22 with the same dimensions and structure and a waveguide number of n>N; and a second curved waveguide array 20 with a waveguide number of n>N. The third output waveguide array 12, the fifth linear tapered waveguide array 14, the third planar waveguide 16, the seventh linear tapered waveguide array 18, the second curved waveguide array 20, the eighth linear tapered waveguide array 22, the fourth planar waveguide 24, the sixth linear tapered waveguide array 26, and the fourth output waveguide array 28 are connected sequentially; the first 1×2 MMI unit 8 is connected to the first planar waveguide 15 of the left AWG via the first bent waveguide 9, and to the third planar waveguide 16 of the right AWG via the second bent waveguide 10; the second 1×2 MMI unit 38 is connected to the second planar waveguide 23 of the left AWG via the third bent waveguide 39, and to the fourth planar waveguide 24 of the right AWG via the fourth bent waveguide 40; the first 1×2 MMI unit input single-mode straight waveguide 1 and the second 1×2 MMI unit input single-mode straight waveguide 31 constitute the input port of the high-symmetry, high-bandwidth flexible array waveguide grating chip; the N waveguides in the first output waveguide array 11, the N waveguides in the second output waveguide array 27, the N waveguides in the third output waveguide array 12, and the N waveguides in the fourth output waveguide array 28 constitute the output port of the high-symmetry, high-bandwidth flexible array waveguide grating chip, where N is an integer greater than or equal to 4.

[0010] The array consists of: a first 1×2 MMI unit input single-mode straight waveguide 1, a first 1×2 MMI unit first output curved waveguide 5, a first 1×2 MMI unit second output curved waveguide 7, a second 1×2 MMI unit input single-mode straight waveguide 31, a second 1×2 MMI unit first output curved waveguide 35, a second 1×2 MMI unit second output curved waveguide 37, a first curved waveguide 9, a second curved waveguide 10, a third curved waveguide 39, a fourth curved waveguide 40, a first output waveguide array 11, a second output waveguide array 27, a third output waveguide array 12, a fourth output waveguide array 28, and a first curved waveguide array. In arrays 19 and 20, the width W1 of each waveguide is the same, ranging from 2 to 10 μm; the array length L3 of arrays 11, 27, 12, and 28 is the same, ranging from 1000 to 8000 μm, the array width W7 is the same, ranging from 500 to 8000 μm, and the spacing W2 between individual waveguides in the array is the same, ranging from 10 to 150 μm; the first 1×2 MMI unit input linear tapered waveguide 2, the first 1×2 MMI unit first output linear tapered waveguide 4, the first 1×2 MMI unit second output linear tapered waveguide 6, and the second... The length L2 of each linear tapered waveguide in the 1×2MMI unit input linear tapered waveguide 32, the first output linear tapered waveguide 34 of the second 1×2MMI unit, the second output linear tapered waveguide 36 of the second 1×2MMI unit, and the lengths of individual linear tapered waveguides in the first linear tapered waveguide array 13, the second linear tapered waveguide array 25, the third linear tapered waveguide array 17, the fourth linear tapered waveguide array 21, the fifth linear tapered waveguide array 14, the sixth linear tapered waveguide array 26, the seventh linear tapered waveguide array 18, and the eighth linear tapered waveguide array 22 are the same, ranging from 100 to 500 μm. The narrow port width W of each linear tapered waveguide is... 1. The width of the same type is 2-10 μm, and the width of the wide port W3 is 4-20 μm. The connection between the first 1×2MMI unit input linear tapered waveguide 2, the first 1×2MMI unit first output linear tapered waveguide 4, the first 1×2MMI unit second output linear tapered waveguide 6, the second 1×2MMI unit input linear tapered waveguide 32, the second 1×2MMI unit first output linear tapered waveguide 34, the second 1×2MMI unit second output linear tapered waveguide 36 and the first 1×2MMI unit multimode planar waveguide 3, the second 1×2MMI unit multimode planar waveguide 33 is the wide port of the linear tapered waveguide.The first linear tapered waveguide array 13, the second linear tapered waveguide array 25, the third linear tapered waveguide array 17, the fourth linear tapered waveguide array 21, the fifth linear tapered waveguide array 14, the sixth linear tapered waveguide array 26, the seventh linear tapered waveguide array 18, and the eighth linear tapered waveguide array 22 are connected to the first planar waveguide 15, the second planar waveguide 23, the third planar waveguide 16, and the fourth planar waveguide 24 of the planar waveguide at the wide port of the linear tapered waveguide, and W3 > W1; the first linear tapered waveguide array 13, the second linear tapered waveguide array 25, the third linear tapered waveguide array 26, the seventh linear tapered waveguide array 17, the fourth linear tapered waveguide array 21, the fifth linear tapered waveguide array 14, the sixth linear tapered waveguide array 26, the seventh linear tapered waveguide array 18, and the eighth linear tapered waveguide array 22 are connected to the first planar waveguide 15, the second planar waveguide 23, the third planar waveguide 16, and the fourth planar waveguide 24 of the planar waveguide are connected to the wide port of the linear tapered waveguide, and W3 > W1; The wide-port center spacing W6 of adjacent linear tapered waveguides in linear tapered waveguide arrays 17, 21, 14, 26, 18, and 22 is the same, ranging from 4 to 30 μm, and W6 ≥ W3; the width W5 of the first 1×2 MMI unit multimode planar waveguide 3 and the second 1×2 MMI unit multimode planar waveguide 33 is the same, ranging from 25 to 70 μm, and the length L1 is the same, ranging from 450 to 1500 μm; the first 1×2 MMI unit multimode planar waveguide 3... The waveguide center distances of the first output linear tapered waveguide 4 and the second output linear tapered waveguide 6 of the first 1×2 MMI unit, and the waveguide center distance W4 of the first output linear tapered waveguide 34 and the second output linear tapered waveguide 36 of the second 1×2 MMI unit, are the same, ranging from 10 to 20 μm; the Rowland circle diameters R of the first planar waveguide 15, the second planar waveguide 23, the third planar waveguide 16, and the fourth planar waveguide 24 are the same, ranging from 500 to 8000 μm; the waveguide center extension line of the first curved waveguide 9 at the connection with the first planar waveguide 15 and the first planar waveguide 24 are the same. The channel input angle formed by the centerline of waveguide 15, the channel input angle formed by the extended waveguide center line of the third curved waveguide 39 at the connection with the second flat waveguide 23 and the centerline of the second flat waveguide 23 are the same as θ1, the channel input angle formed by the extended waveguide center line of the second curved waveguide 10 at the connection with the third flat waveguide 16 and the centerline of the third flat waveguide 16, and the channel input angle formed by the extended waveguide center line of the fourth curved waveguide 40 at the connection with the fourth flat waveguide 24 and the centerline of the fourth flat waveguide 24 are the same as θ2, θ1 is not equal to θ2, and; (m is the diffraction order of the grating, n) s(where Δλ is the effective refractive index of the planar waveguide and Δλ is the difference in center wavelength between adjacent output channels of the AWG). The shortest curved waveguide in the first curved waveguide array 19 and the second curved waveguide array 20 has the same length L4, ranging from 1000 to 5000 μm, and the longest curved waveguide has the same length L5, ranging from 1300 to 30000 μm. The length difference ΔL between adjacent waveguides is the same, ranging from 10 to 200 μm, and L5 = L4 + (n-1) × ΔL. All waveguide lengths are defined as the projected length of the waveguide along the line connecting the centers of the first 1×2 MMI unit input single-mode straight waveguide 1 and the second 1×2 MMI unit input single-mode straight waveguide 31.

[0011] The high-symmetry, large-bandwidth flexible array waveguide grating chip for FBG demodulation systems described in this invention, when the first 1×2 MMI unit input single-mode straight waveguide 1 is used as the input channel for the reflected light of the FBG, and the N waveguides in the second output waveguide array 27 and the N waveguides in the fourth output waveguide array 28 are used as output channels, the signal light is input through the first 1×2 MMI unit input linear tapered waveguide 2 and then into the wavelength-independent first 1×2 MMI unit multimode planar waveguide 3. It is then evenly split into two identical beams of signal light, which are respectively input into the first planar waveguide 15 of the left AWG by the first output linear tapered waveguide 4, the first output curved waveguide 5, and the first curved waveguide 9 of the first 1×2 MMI unit, and into the third planar waveguide 16 of the right AWG by the second output linear tapered waveguide 6, the second output curved waveguide 7, and the second curved waveguide 10 of the first 1×2 MMI unit. According to the grating formula (1), due to the designed signal light incident angle θ... i The difference between θ1 and θ2 makes the center wavelengths of the output channels of the left and right AWG, which are not spatially adjacent, close, forming spectral adjacency. That is, the center wavelength of each output channel in the fourth output waveguide array 28 is correspondingly located in the middle of the center wavelengths of the two output channels in the second output waveguide array 27. When the center wavelength of the FBG reflected signal light to be demodulated is between the center wavelengths of any two adjacent output channels in the second output waveguide array 27 of the left AWG, unlike the case where a single AWG has only one channel output, two beams of signal light with different output intensities will be detected in any output channel in the second output waveguide array 27 of the left AWG and the corresponding output channel in the fourth output waveguide array 28 of the right AWG. Then, according to the relationship between the logarithmic ratio of the light intensities of adjacent channels in the output spectrum and the center wavelength of the FBG reflected signal light in demodulation formula (2), the wavelength λ of the FBG reflected light can be obtained. FBG Where Δλ is the center wavelength spacing between adjacent spectral channels, Δλ FBGThe full width at half maximum (FWHM) of the FBG reflected light is given when the center wavelength of the FBG reflected signal light is within the range of the center wavelength of any output waveguide channel in the left AWG second output waveguide array 27 and the center wavelength of the corresponding adjacent output waveguide channel in the right AWG fourth output waveguide array 28 in the output spectrum. In demodulation formula (2), P... i Δλ is the signal optical power output from the corresponding output waveguide channel in the second output waveguide array 27 of the left AWG. i and λ i These are the full width at half maximum (FWHM) and center wavelength of the channel spectrum, respectively. i+1 λ is the signal optical power output from the corresponding spectral adjacent output waveguide channel in the fourth output waveguide array 28 of the right AWG. i+1 It is the center wavelength of the channel spectrum. When the center wavelength of the FBG reflected signal light is within the range of the center wavelength of any output waveguide channel in the right AWG fourth output waveguide array 28 and the corresponding adjacent output waveguide channel center wavelength in the left AWG second output waveguide array 27, P in demodulation formula (2) i Δλ is the signal optical power output from the corresponding output waveguide channel in the fourth output waveguide array 28 of the right AWG. i and λ i These are the full width at half maximum (FWHM) and center wavelength of the channel spectrum, respectively. i+1 λ is the signal optical power output from the corresponding spectral adjacent output waveguide channel in the second output waveguide array 27 of the left AWG. i+1 This is the center wavelength of the channel spectrum. Therefore, when the device is working, the logarithmic ratio of the light intensity of adjacent channels in the demodulation function is linear with the center wavelength of the FBG reflected signal light, and it is continuous in the spectrum, resulting in high detection resolution and solving the problems of demodulation blind zone and narrow dynamic detection range in traditional single AWGs. When the second 1×2MMI unit input single-mode straight waveguide 31 is used as the input channel of the FBG reflected light, and the N waveguides in the first output waveguide array 11 and the N waveguides in the third output waveguide array 12 are used as output channels, the working principle is the same as described above, and the two ends can be interchanged.

[0012] n s W6sinθ i +n s W6sinθ o +n c ΔL=mλ (1)

[0013]

[0014] Where n s n is the mode effective refractive index of the AWG array waveguide. c For the mode effective refractive index of the AWG planar waveguide, θ iLet θ be the incident angle of the signal light. o The signal light emission angle.

[0015] The high-symmetry, large-bandwidth flexible array waveguide grating chip for FBG demodulation system described in this invention has two AWGs that are flat or Gaussian-type aligned waveguide gratings, and two 1×2 MMI units that are wideband wavelength-independent one-to-two uniform optical splitters.

[0016] The present invention discloses a high-symmetry, large-bandwidth flexible array waveguide grating chip for FBG demodulation systems. The polymer flexible substrate 41 is made of polymer PDMS with a thickness of 0.5–1 mm. The polymer lower cladding layer 42 and the polymer upper cladding layer 44 are made of any one of a series of transparent polymer materials, including fluorinated bisphenol A phenolic resin (F-SU8Clad), polyethylene (PE), polystyrene (PS), polycarbonate (PC), polymethyl methacrylate (PMMA), P (MMA-co-GMA), and EpoClad (in the same device, the polymer upper cladding layer 44 material above the polymer core layer 33 can be the same as or different from the polymer lower cladding layer 42 material), with a thickness of 5–15 μm (the thickness of the polymer upper cladding layer 44 above the polymer core layer 33 can be the same as or different from the thickness of the polymer lower cladding layer 42). The polymer core layer 43 is made of a polymer with a refractive index greater than that of the polymer cladding material, including fluorinated bisphenol A phenolic resin core (F-SU8Core), SU-8 2002, and SU-8... A series of UV direct-write photoresist materials, including 2005 and EpoCore, have a thickness of 3–8 μm.

[0017] Compared with existing device structures and fabrication techniques, the advantages of this invention are:

[0018] (1) The present invention designs a wavelength-independent 1×2MMI waveguide structure at the input end, so that the input signal light is evenly divided into two uniform signal lights. At the same time, the designed tapered waveguide connection reduces device loss. More importantly, the optical field transmitted in the input MMI and tapered waveguide generates mode integration, thereby making the output spectrum of AWG more flat-topped, significantly widening the output spectral bandwidth, reducing inter-channel crosstalk, and obtaining a more ideal Gaussian spectral response, covering a wider wavelength demodulation range;

[0019] (2) This invention uses two AWGs with identical structural parameters. By designing different channel input angles θ1 and θ2 between the left and right AWGs, the center wavelengths of the output channels of the two AWGs are different, and the output channel spectra are adjacent, forming a continuous spectral band. This ensures that at least two output channels have effective signals at any FBG reflected light wavelength, and the peak position can be achieved by controlling the input angles θ1 and θ2. It has both the high speed and high precision characteristics of traditional AWG demodulation methods and the flexibility of operation. It effectively solves the problem of demodulation blind zone, realizes continuous demodulation, and greatly improves the dynamic demodulation range of FBG sensors.

[0020] (3) Compared with the traditional FBG sensor wavelength demodulation AWG, the demodulation signal input / output terminals of this invention can be interchanged between the left and right ports, which is reciprocal and greatly improves the flexibility of use. At the same time, based on the polymer material platform, the preparation process is simple and low cost, and the device has good flexibility, which can achieve ultra-thinness and certain bending deformation. It is not easy to break after repeated bending and can still maintain the stability of light transmission under dynamic deformation. It has significant advantages in dynamic deformation environment or biological integration scenario. Attached Figure Description

[0021] Figure 1 This is a schematic cross-sectional view of a high-symmetry, large-bandwidth flexible arrayed waveguide grating chip for FBG demodulation systems according to the present invention (corresponding to...). Figure 2 (Sectional view A-A' in the middle);

[0022] Figure 2 This is a schematic diagram of the core layer structure of a high-symmetry, large-bandwidth flexible array waveguide grating chip for FBG demodulation systems according to the present invention.

[0023] Figure 3 The input waveguide cross section of the device described in Example 1 (corresponding to the attached diagram) Figure 2 Single-mode transmission optical field diagram at position B-B';

[0024] Figure 4 (a) is a schematic diagram of the 1×2MMI structure described in this invention; Figure 4 (b) is the output optical power diagram of the two output channels (CH1 and CH2, i.e., the first output linear tapered waveguide 4 and the second output linear tapered waveguide 6 of the first 1×2MMI unit) in the O band of the present invention;

[0025] Figure 5 (a) is a schematic diagram of the spectral distribution of the device described in this invention in the O band; Figure 5 (b) The device uses adjacent channels (O1, O9, O2, O) at the center wavelength. 10 ) FBG wavelength demodulation process curve; Figure 5 (c) represents the adjacent channels (O1, O9, O2, O) of the device's center wavelength. 10 The relationship between the logarithmic ratio of output optical power and the reflection wavelength of the FBG is shown in the graph.

[0026] Figure 6 This is a flowchart of the device fabrication process in Example 2. Detailed Implementation

[0027] The present invention will now be described more clearly and comprehensively with reference to the accompanying drawings. It should be noted that those skilled in the art will gain a deeper understanding of the advantages and functions of the present invention from this description. However, the described embodiments are only some, not all, of the embodiments of the present invention. All other embodiments obtained by those skilled in the art based on the embodiments of the present invention without creative effort are within the scope of protection of the present invention.

[0028] Example 1:

[0029] In this embodiment, the polymer flexible substrate 41 is a PDMS polymer flexible substrate with a thickness of 0.5 mm.

[0030] In this embodiment, the polymer upper cladding 44 (the thickness of the polymer upper cladding above the polymer waveguide core layer 43) and the polymer lower cladding 42 of the device are 6 μm thick F-SU8Clad (refractive index n = 1.4942 @ 1310 nm).

[0031] In this embodiment, the polymer waveguide core 43 of the fabricated device is an F-SU8Core with a thickness of 3μm and a width (W1) of 3μm (refractive index n = 1.515@1310nm).

[0032] In this embodiment, the demodulated signal band is selected as the O band (1260nm~1360nm).

[0033] This embodiment uses COMSOL Mutiphysics software to simulate a highly symmetric, large-bandwidth flexible arrayed waveguide grating chip for an FBG demodulation system at the input waveguide (corresponding to the attached image). Figure 2 The waveguide cross-section at position B-B' shows the optical field diagram. To ensure that the demodulated signal light is input to the chip in fundamental mode form, see attached diagram. Figure 3 As shown in the figure, the simulation results indicate that the polymer waveguide core structure of the designed device should have a size of 3μm×3μm. Under this size, the signal light can achieve low-loss single-mode transmission.

[0034] As attached Figure 4As shown, this embodiment uses Rsoft software to simulate and design a 1×2 MMI device with O-band wavelength independence in a high-symmetry, large-bandwidth flexible arrayed waveguide grating chip for FBG demodulation systems. To better improve the bandwidth of the AWG and obtain a more ideal Gaussian spectral response, as shown in the attached diagram... Figure 4 As shown in (a) and (b), when the linear tapered waveguide wide port width W3 is 6 μm, the MMI device multimode interference region structure length L1 is 28.1 μm, the width W5 is 520.0 μm, and the center distance W4 between the two output waveguides is 15.1 μm, the 1×2 MMI device has the lowest transmission loss, the signal optical power output by the two channels is consistent, and the transmission characteristics in the O band are wavelength independent.

[0035] This embodiment presents a high-symmetry, large-bandwidth flexible arrayed waveguide grating chip structure for an FBG demodulation system. The waveguide number N in the first output waveguide array 11, second output waveguide array 27, third output waveguide array 12, and fourth output waveguide array 28 is 8; the number of bent waveguides n in the first bent waveguide array 19 and second bent waveguide array 20 is 40; the grating diffraction order m is 41; the center wavelength difference Δλ between adjacent AWG output channels is 1.6 nm; and the structure includes a first 1×2 MMI unit input single-mode straight waveguide 1, a first 1×2 MMI unit first output bent waveguide 5, a first 1×2 MMI unit second output bent waveguide 7, a second 1×2 MMI unit input single-mode straight waveguide 31, and a second 1×2 MMI unit input single-mode straight waveguide 31. The individual waveguide width W1 in the MMI unit's first output curved waveguide 35, the second 1×2 MMI unit's second output curved waveguide 37, the first curved waveguide 9, the second curved waveguide 10, the third curved waveguide 39, the fourth curved waveguide 40, and the first output waveguide array 11, the second output waveguide array 27, the third output waveguide array 12, the fourth output waveguide array 28, the first curved waveguide array 19, and the second curved waveguide array 20 is 3μm; the array length L3 of the first output waveguide array 11, the second output waveguide array 27, the third output waveguide array 12, and the fourth output waveguide array 28 is 1500μm, and the array width W7 is 3500μm. To facilitate FA array coupling, the waveguides in the array... The spacing W2 between the guides is 127 μm; the first 1×2 MMI unit input linear tapered waveguide 2, the first 1×2 MMI unit first output linear tapered waveguide 4, the first 1×2 MMI unit second output linear tapered waveguide 6, the second 1×2 MMI unit input linear tapered waveguide 32, the second 1×2 MMI unit first output linear tapered waveguide 34, the second 1×2 MMI unit second output linear tapered waveguide 36, and the first linear tapered waveguide array 13, the second linear tapered waveguide array 25, the third linear tapered waveguide array 17, the fourth linear tapered waveguide array 21, the fifth linear tapered waveguide array 14, the sixth linear tapered waveguide array 26, the seventh linear tapered waveguide array 18, and the... In the eight linear tapered waveguide array 22, the length L2 of a single linear tapered waveguide is 300 μm, the narrow port width W1 of a single linear tapered waveguide is 3 μm, and the wide port width W3 is 6 μm; the center-to-center distance W6 between the wide ports of adjacent linear tapered waveguides in the first linear tapered waveguide array 13, the second linear tapered waveguide array 25, the third linear tapered waveguide array 17, the fourth linear tapered waveguide array 21, the fifth linear tapered waveguide array 14, the sixth linear tapered waveguide array 26, the seventh linear tapered waveguide array 18, and the eighth linear tapered waveguide array 22 is 6 μm; the width W5 of the first 1×2 MMI unit multimode planar waveguide 3 and the second 1×2 MMI unit multimode planar waveguide 33 is 28 μm.The length L1 is 520μm; the waveguide center distances of the first output linear tapered waveguide 4 and the second output linear tapered waveguide 6 of the first 1×2MMI unit, and the waveguide center distance W4 of the first output linear tapered waveguide 34 and the second output linear tapered waveguide 36 of the second 1×2MMI unit are 15.1μm; the Rowland circle diameter R of the first planar waveguide 15, the second planar waveguide 23, the third planar waveguide 16, and the fourth planar waveguide 24 is 1150μm; the channel input angle formed by the extension line of the waveguide center of the first curved waveguide 9 at the connection with the first planar waveguide 15 and the center line of the first planar waveguide 15, and the channel input angle formed by the extension line of the waveguide center of the third curved waveguide 39 at the connection with the second planar waveguide 15, and the channel input angle formed by the extension line of the waveguide center of the third curved waveguide 39 at the connection with the second planar waveguide 15, are 15.1μm; The channel input angle θ1 formed by the extended waveguide center line at the connection point of plate waveguide 23 and the center line of the second plate waveguide 23 is 16.3°. The channel input angle formed by the extended waveguide center line of the second curved waveguide 10 at the connection point with the third plate waveguide 16 and the center line of the third plate waveguide 16, and the channel input angle θ2 formed by the extended waveguide center line of the fourth curved waveguide 40 at the connection point with the fourth plate waveguide 24 and the center line of the fourth plate waveguide 24, are 16.9°. The total length L4 of the shortest curved waveguide in the first curved waveguide array 19 and the second curved waveguide array 20 is 1000 μm, the total length L5 of the longest curved waveguide is 2392.3 μm, and the length difference ΔL between adjacent waveguides is the same at 35.7 μm.

[0036] The high-symmetry, high-bandwidth flexible arrayed waveguide grating chip for the FBG demodulation system described in this embodiment has the following O-band transmission spectrum: Figure 5 As shown in (a), the solid and dashed lines represent the upper and lower output channel spectra, respectively. It can be seen that the maximum insertion loss of the device is around -4dB, and the wavelength spacing between individual AWG channels is 1.6nm. The 1×2 MMI device and linear tapered waveguide design make the AWG spectrum more flat-topped, increase the bandwidth, and reduce crosstalk between spatially adjacent channels of a single AWG (crosstalk < -27dB). Furthermore, it can be seen that at any demodulation wavelength, there are effective output signals from both output channels, and there is no demodulation dead zone. (See attached image.) Figure 5 As shown in (b), assuming the wavelength of the light reflected by the FBG is located at λ shown in the figure. FBG At this time, the reflected light from the FBG is input into the arrayed waveguide grating of this embodiment. Two effective signals with optical powers of P1 and P9 can be detected at the output channels O1 and O9 of the device. Then, according to the logarithmic ratio of O1 and O9 and λ in the demodulation formula (2), FBG linear relationship Then the λ can be demodulated. FBG Similarly, λ FBG In the appendix Figure 5 Demodulation can be performed at any position in the spectrum in (b). (See attached image.) Figure 5 As shown in (c), λ was calculated and enumerated.FBG The wavelength ranges 1.3048–1.3056, 1.3056–1.3064, 1.3064–1.3072, and 1.3072–1.3082 are respectively and The linear relationship between the two, i.e. the demodulation function, shows that continuous demodulation with high accuracy can be achieved. At the same time, the working effect is consistent when the input and output of the left and right ports are interchanged.

[0037] Example 2:

[0038] The fabrication method of the high-symmetry, large-bandwidth flexible arrayed waveguide grating chip for the FBG demodulation system described in this embodiment has the following steps: Figure 6 As shown, the specific description is as follows:

[0039] A. Cleaning the PDMS polymer flexible substrate 41: The polymer flexible substrate is ultrasonically cleaned with acetone solution for 15 min; then, the surface of the PDMS polymer flexible substrate is wiped four times in one direction with acetone-soaked cotton balls, and the above wiping process is repeated with ethanol-soaked cotton balls to remove acetone residue; after rinsing with deionized water multiple times, the surface is dehydrated by nitrogen purging technology; the clean polymer flexible substrate is transferred to a constant temperature oven for drying (temperature 120℃, time 30 min); finally, plasma surface treatment is performed for 90 s;

[0040] B. Spin-coating F-SU8Clad polymer lower cladding layer 42: On the surface of the treated PDMS polymer flexible substrate, an F-SU8 cladding film was prepared using a spin-coating process with a spin speed of 2500 r / min and a time of 20 s. This was followed by pre-baking at temperatures / times of 60℃ / 5 min, 90℃ / 10 min, and 120℃ / 10 min to allow the organic solvent to evaporate, followed by natural cooling to room temperature. After cooling to room temperature, the substrate was exposed to ultraviolet light at a wavelength of 350–400 nm for 110 s, followed by post-baking at 60℃ / 5 min, 90℃ / 10 min, and 120℃ / 10 min, and then allowed to cool naturally to obtain a 5 μm thick F-SU8Clad polymer lower cladding layer. Finally, a plasma surface treatment was performed for 90 s.

[0041] C. Spin-coating F-SU8Core core film 43': On the surface of the F-SU8Clad film with the polymer undercoating, an F-SU8 core film was prepared by spin-coating. The spin speed was 3000 r / min and the time was 20 s. Then, the film was baked at the following temperatures / times: 60℃ / 5 min, 90℃ / 10 min, and 120℃ / 10 min to evaporate the organic solvent. Then, the film was allowed to cool naturally to room temperature to obtain a 3 μm thick negative F-SU8Core core film 43'.

[0042] D. Core layer F-SU8Core thin film 43' photolithography: The designed device structure (corresponding to the attached...) is then... Figure 2 A photomask 45 (with a structure complementary to the prepared core layer structure) was applied to the negative F-SU8Core thin film and attached to its surface. It was exposed to ultraviolet light with a wavelength of 350-400nm for 111s using an ultraviolet lithography machine. After exposure, it was baked at a temperature / time of 120℃ for 10min and then allowed to cool naturally to room temperature.

[0043] E. Development of the F-SU8Core Core Layer 43 Structure: The unexposed core layer film was etched away using PGMEA developer to obtain a clearly visible morphology of the F-SU8Core polymer waveguide core layer structure. Then, the developer was washed away with isopropanol solution, followed by deionized water and nitrogen drying. The film was then baked at 120℃ for 10 min and allowed to cool naturally to room temperature to complete the fabrication of the F-SU8Core polymer waveguide core layer structure 43. Finally, a plasma surface treatment was performed for 120 s.

[0044] F. Spin-coating F-SU8Clad polymer cladding 44: On the surface of the prepared polymer waveguide core F-SU8Core structure 43, an F-SU8Clad polymer cladding is prepared using a spin-coating process with a spin speed of 2500 r / min and a time of 20 s. Then, a pre-baking process is performed at temperatures / times of 60℃ / 5 min, 90℃ / 10 min, and 120℃ / 10 min to evaporate the organic solvent. The mixture is then allowed to cool naturally to room temperature. After cooling to room temperature, the mixture is exposed to ultraviolet light at a wavelength of 350–400 nm for 110 s using a photolithography machine, followed by a post-baking process at 60℃ / 5 min, 90℃ / 10 min, and 120℃ / 10 min to harden the film. The mixture is then allowed to cool naturally to obtain a 5 μm thick F-SU8Clad polymer cladding. Finally, a high-symmetry, large-bandwidth flexible array waveguide grating chip for FBG demodulation systems, as described in this invention, is obtained.

Claims

1. A highly symmetric, large-bandwidth flexible arrayed waveguide grating chip for FBG demodulation systems, characterized in that: From bottom to top, it consists of a polymer flexible substrate (41), a polymer lower cladding (42), a polymer waveguide core layer (43), and a polymer upper cladding (44). The polymer waveguide core layer (43) and the polymer upper cladding (44) are both located on the polymer lower cladding (42), and the polymer waveguide core layer (43) is completely enclosed in the polymer upper cladding (44). The effective refractive index of the polymer waveguide core layer is higher than that of the polymer upper cladding and the polymer lower cladding. The polymer waveguide core layer (43) is composed of a first 1×2 MMI unit (8), a second 1×2 MMI unit (38), a left AWG, and a right AWG. The first 1×2 MMI unit (8) and the second 1×2 MMI unit (38) have the same size parameters and structure and are symmetrically arranged front and back. The left AWG and the right AWG have the same size parameters and structure and are related to the first 1×2 MMI unit (8) and the second 1×2 MMI unit (38). The MMI units (38) are symmetrically arranged on the left and right, and the entire device has central symmetry; the left AWG and right AWG are flat or Gaussian-type aligned waveguide gratings, and the two 1×2 MMI units are wideband wavelength-independent one-to-two uniform optical splitters; the first 1×2 MMI unit (8) is composed of the first 1×2 MMI unit input single-mode straight waveguide (1), the first 1×2 MMI unit input linear tapered waveguide (2), the first 1×2 MMI unit multimode planar waveguide (3), the first 1×2 MMI unit first output linear tapered waveguide (4) and the first 1×2 MMI unit second output linear tapered waveguide (6) with the same size parameters and structure, the first 1×2 MMI unit first output curved waveguide (5) and the first 1×2 MMI unit second output curved waveguide (7) with the same size parameters and structure; the second 1×2 MMI unit (38) is composed of the second 1×2 MMI unit input single-mode straight waveguide (31), the second 1×2 MMI unit multimode planar waveguide (32), the first 1×2 MMI unit input single-mode straight waveguide (31), the second 1×2 MMI unit multimode planar waveguide (32), the first 1×2 MMI unit first output curved waveguide (5) and the first 1×2 MMI unit second output curved waveguide (7) with the same size parameters and structure; The system consists of an MMI unit input linear tapered waveguide (32), a second 1×2 MMI unit multimode planar waveguide (33), a second 1×2 MMI unit first output linear tapered waveguide (34) with the same size parameters and structure, a second 1×2 MMI unit second output linear tapered waveguide (36), a second 1×2 MMI unit first output curved waveguide (35) with the same size parameters and structure, and a second 1×2 MMI unit second output curved waveguide (37).The left AWG consists of a first output waveguide array (11) and a second output waveguide array (27) with the same size parameters and structure and a waveguide number of N; a first linear tapered waveguide array (13) and a second linear tapered waveguide array (25) with the same size parameters and structure and a waveguide number of N; a first planar waveguide (15) and a second planar waveguide (23) with the same size parameters and structure; a third linear tapered waveguide array (17) and a fourth linear tapered waveguide array (21) with the same size parameters and structure and a waveguide number of n>N; and a first curved waveguide array (19) with a waveguide number of n>N. The first output waveguide array (11), the first linear tapered waveguide array (13), the first planar waveguide (15), the third linear tapered waveguide array (17), the first curved waveguide array (19), the fourth linear tapered waveguide array (21), the second planar waveguide (23), the second linear tapered waveguide array (25), and the second output waveguide array (27) are connected sequentially. The right A WG consists of a third output waveguide array (12) and a fourth output waveguide array (28) with the same size parameters and structure and a waveguide number of N; a fifth linear tapered waveguide array (14) and a sixth linear tapered waveguide array (26) with the same size parameters and structure and a waveguide number of N; a third planar waveguide (16) and a fourth planar waveguide (24) with the same size parameters and structure; a seventh linear tapered waveguide array (18) and an eighth linear tapered waveguide array (22) with the same size parameters and structure and a waveguide number of n>N; and a second curved waveguide array (20) with a waveguide number of n>N. The third output waveguide array (12), the fifth linear tapered waveguide array (14), the third planar waveguide (16), the seventh linear tapered waveguide array (18), the second curved waveguide array (20), the eighth linear tapered waveguide array (22), the fourth planar waveguide (24), the sixth linear tapered waveguide array (26), and the fourth output waveguide array (28) are connected sequentially; the first 1×2 The MMI unit (8) is connected to the first planar waveguide (15) of the left AWG via the first curved waveguide (9), and to the third planar waveguide (16) of the right AWG via the second curved waveguide (10); the second 1×2 MMI unit (38) is connected to the second planar waveguide (23) of the left AWG via the third curved waveguide (39), and to the fourth planar waveguide (24) of the right AWG via the fourth curved waveguide (40); the input single-mode straight waveguide (1) of the first 1×2 MMI unit and the input single-mode straight waveguide (31) of the second 1×2 MMI unit constitute the input port of the high-symmetry, high-bandwidth flexible array waveguide grating chip; the N waveguides in the first output waveguide array (11), the N waveguides in the second output waveguide array (27), the N waveguides in the third output waveguide array (12), and the N waveguides in the fourth output waveguide array (28) constitute the output port of the high-symmetry, high-bandwidth flexible array waveguide grating chip, where N is an integer greater than or equal to 4.

2. The high-symmetry, large-bandwidth flexible arrayed waveguide grating chip for FBG demodulation systems as described in claim 1, characterized in that: First 1×2 MMI unit input single-mode straight waveguide (1), first 1×2 MMI unit first output curved waveguide (5), first 1×2 MMI unit second output curved waveguide (7), second 1×2 MMI unit input single-mode straight waveguide (31), second 1×2 MMI unit first output curved waveguide (35), second 1×2 The second output curved waveguide (37), first curved waveguide (9), second curved waveguide (10), third curved waveguide (39), and fourth curved waveguide (40) of the MMI unit have the same individual waveguide width W1 of 2 to 10 μm as the first output waveguide array (11), second output waveguide array (27), third output waveguide array (12), fourth output waveguide array (28), first curved waveguide array (19), and second curved waveguide array (20); the array length L3 of the first output waveguide array (11), second output waveguide array (27), third output waveguide array (12), and fourth output waveguide array (28) is 1000 to 8000 μm, the array width W7 is 500 to 8000 μm, and the spacing W2 between individual waveguides in the array is 10 to 150 μm; the first 1×2 MMI unit input linear tapered waveguide (2), the first 1×2 MMI unit first output linear tapered waveguide (4), and the first 1×2 The second output linear tapered waveguide (6) of the MMI unit, the second 1×2 MMI unit input linear tapered waveguide (32), the first output linear tapered waveguide (34) of the second 1×2 MMI unit, the second output linear tapered waveguide (36) of the second 1×2 MMI unit, and the individual linear tapered waveguides in the first linear tapered waveguide array (13), the second linear tapered waveguide array (25), the third linear tapered waveguide array (17), the fourth linear tapered waveguide array (21), the fifth linear tapered waveguide array (14), the sixth linear tapered waveguide array (26), the seventh linear tapered waveguide array (18), and the eighth linear tapered waveguide array (22) have the same length L2 of 100-500μm, and the same narrow port width W1 of 2-10μm and wide port width W3 of 4-20μm; the first 1×2 The connection points of the MMI unit input linear tapered waveguide (2), the first output linear tapered waveguide (4) of the first 1×2 MMI unit, the second output linear tapered waveguide (6) of the first 1×2 MMI unit, the second input linear tapered waveguide (32) of the second 1×2 MMI unit, the first output linear tapered waveguide (34) of the second 1×2 MMI unit, the second output linear tapered waveguide (36) of the second 1×2 MMI unit, and the first multimode planar waveguide (3) and the second multimode planar waveguide (33) of the first 1×2 MMI unit are wide ports of the linear tapered waveguides;The first linear tapered waveguide array (13), the second linear tapered waveguide array (25), the third linear tapered waveguide array (17), the fourth linear tapered waveguide array (21), the fifth linear tapered waveguide array (14), the sixth linear tapered waveguide array (26), the seventh linear tapered waveguide array (18), and the eighth linear tapered waveguide array (22) are connected to the first planar waveguide (15), the second planar waveguide (23), the third planar waveguide (16), and the fourth planar waveguide (24) of the planar waveguides in a linear tapered shape. The wide port of the waveguide, and W3 > W1; the center-to-center spacing W6 of the wide ports of adjacent linear tapered waveguides in the first linear tapered waveguide array (13), the second linear tapered waveguide array (25), the third linear tapered waveguide array (17), the fourth linear tapered waveguide array (21), the fifth linear tapered waveguide array (14), the sixth linear tapered waveguide array (26), the seventh linear tapered waveguide array (18), and the eighth linear tapered waveguide array (22) is the same, which is 4 to 30 μm, and W6 ≥ W3; the first 1×2 The width W5 of the MMI unit multimode planar waveguide (3) and the second 1×2 MMI unit multimode planar waveguide (33) are the same, ranging from 25 to 70 μm, and the length L1 is the same, ranging from 450 to 1500 μm; the waveguide center distance of the first output linear tapered waveguide (4) and the second output linear tapered waveguide (6) of the first 1×2 MMI unit, and the second output linear tapered waveguide (34) and the second 1×2 MMI unit multimode planar waveguide (33) are the same, ranging from 25 to 70 μm; The waveguide center distance W4 of the second output linear tapered waveguide (36) of the MMI unit is the same, ranging from 10 to 20 μm; the Rowland circle diameter R of the first planar waveguide (15), the second planar waveguide (23), the third planar waveguide (16), and the fourth planar waveguide (24) is the same, ranging from 500 to 8000 μm; the channel input angle formed by the extension line of the waveguide center of the first curved waveguide (9) at the connection with the first planar waveguide (15) and the center line of the first planar waveguide (15), and the channel input angle formed by the extension line of the waveguide center of the third curved waveguide (39) at the connection with the second planar waveguide (24) and the channel input angle formed by the extension line of the waveguide center of the third curved waveguide (39) at the connection with the second planar waveguide (24) and the channel input angle formed by the extension line of the waveguide center of the third curved waveguide (39) at the connection with the second planar waveguide (24) and the channel input angle formed by the extension line of the waveguide center of the third curved waveguide (39) at the connection with the second planar waveguide (24) and the channel input angle formed by the extension line of the waveguide center of the first curved waveguide (9) and the channel input angle formed by the extension line of the waveguide center of the first curved waveguide (15 ... and the channel input angle formed by the extension line of the waveguide center of the first curved waveguide (15) and the channel input angle formed by the The channel input angle formed by the extended waveguide center line at the connection of waveguide (23) and the center line of the second flat waveguide (23) is the same as θ1. The channel input angle formed by the extended waveguide center line at the connection of the second curved waveguide (10) and the center line of the third flat waveguide (16) and the channel input angle formed by the extended waveguide center line at the connection of the fourth curved waveguide (40) and the center line of the fourth flat waveguide (24) is the same as θ2. θ1 is not equal to θ2, and; Where m is the grating diffraction order, n s Δλ is the effective refractive index of the planar waveguide, and Δλ is the difference in center wavelength between adjacent output channels of the AWG. The shortest curved waveguide in the first curved waveguide array 19 and the second curved waveguide array 20 has the same length L4, which is 1000-5000 μm, and the longest curved waveguide has the same length L5, which is 1300-30000 μm. The length difference ΔL between adjacent waveguides is the same, which is 10-200 μm, and L5 = L4 + (n-1) × ΔL. All waveguide lengths are defined as the projected length of the waveguide along the line connecting the center of the first 1×2 MMI unit input single-mode straight waveguide 1 and the second 1×2 MMI unit input single-mode straight waveguide 31.

3. The high-symmetry, large-bandwidth flexible arrayed waveguide grating chip for FBG demodulation systems as described in claim 1, characterized in that: When the input single-mode straight waveguide (1) of the first 1×2 MMI unit is used as the input channel for the reflected light of the FBG, and the N waveguides in the second output waveguide array (27) and the N waveguides in the fourth output waveguide array (28) are used as the output channels, the signal light is input into the first 1×2 MMI unit multimode planar waveguide (3) after passing through the first 1×2 MMI unit input linear tapered waveguide (2), and is then evenly split into two identical beams of signal light. These beams are input into the first planar waveguide (15) of the left AWG by the first output linear tapered waveguide (4), the first output curved waveguide (5), and the first curved waveguide (9) of the first 1×2 MMI unit, respectively, and into the first planar waveguide (15) of the left AWG by the second output linear tapered waveguide (6) of the first 1×2 MMI unit and the first 1×2 MMI unit multimode planar waveguide (3). The second output curved waveguide (7) and the second curved waveguide (10) of the MMI unit are input into the third planar waveguide (16) of the right AWG. Due to the difference in the incident angles θ1 and θ2 of the designed signal light, the center wavelengths of the output channels of the left AWG and the right AWG, which are not spatially adjacent, are close, forming spectral adjacency. That is, the center wavelength of each output channel in the fourth output waveguide array (28) is located in the middle of the center wavelengths of the two output channels in the second output waveguide array (27) respectively. When the center wavelength of the FBG reflected signal light to be demodulated is between the center wavelengths of any two adjacent output channels in the second output waveguide array (27) of the left AWG, two beams of signal light with different light intensities will be detected in any output channel in the second output waveguide array (27) of the left AWG and the corresponding output channel in the fourth output waveguide array (28) of the right AWG respectively. Then, according to the relationship between the logarithmic ratio of the light intensity of the adjacent channels in the output spectrum and the center wavelength of the FBG reflected signal light in the demodulation formula (2), the wavelength λ of the FBG reflected light can be obtained. FBG ; Where Δλ is the center wavelength spacing between adjacent spectral channels. FBG The full width at half maximum (FWHM) of the FBG reflected light is given when the center wavelength of the FBG reflected signal light is within the range of the center wavelength of any output waveguide channel in the left AWG second output waveguide array (27) and the center wavelength of the corresponding adjacent output waveguide channel in the right AWG fourth output waveguide array (28) in the output spectrum. In demodulation formula (2), P... i Δλ is the signal optical power output of the corresponding output waveguide channel in the second output waveguide array (27) of the left AWG. i and λ i These are the full width at half maximum (FWHM) and center wavelength of the channel spectrum, respectively. i+1 λ is the signal optical power output from the corresponding spectral adjacent output waveguide channel in the fourth output waveguide array (28) of the right AWG. i+1 It is the center wavelength of the channel spectrum; when the center wavelength of the FBG reflected signal light is within the range of the center wavelength of any output waveguide channel in the right AWG fourth output waveguide array (28) and the corresponding adjacent output waveguide channel center wavelength in the left AWG second output waveguide array (27), P in demodulation formula (2) i Δλ is the signal optical power output of the corresponding output waveguide channel in the fourth output waveguide array (28) of the right AWG. i and λ i These are the full width at half maximum (FWHM) and center wavelength of the channel spectrum, respectively. i+1 λ is the signal optical power output from the corresponding spectral adjacent output waveguide channel in the second output waveguide array (27) of the left AWG. i+1 It is the center wavelength of the channel spectrum.

4. A high-symmetry, large-bandwidth flexible arrayed waveguide grating chip for FBG demodulation systems as described in claim 1, 2, or 3, characterized in that: The polymer flexible substrate (41) is made of polymer PDMS with a thickness of 0.5–1 mm; the polymer lower cladding (42) and polymer upper cladding (44) are made of fluorinated bisphenol A phenolic resin, polyethylene, polystyrene, polycarbonate, polymethyl methacrylate, P(MMA-co-GMA) or EpoClad with a thickness of 5–15 μm; the polymer core layer (43) is made of fluorinated bisphenol A phenolic resin core, SU-8 2002, SU-82005 or EpoCore with a refractive index greater than that of the polymer cladding material, with a thickness of 3–8 μm.

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