High-crosstalk arrayed waveguide grating structure capable of changing waveform and improving demodulation resolution

Abstract

A high-crosstalk array waveguide grating structure capable of changing waveforms and improving demodulation resolution comprises an input optical waveguide, the output end of the input optical waveguide is connected with the input end of a coupling module, and the output end of the coupling module is sequentially connected with a first slab waveguide, an array waveguide and a second slab waveguide. The output end of the second slab waveguide is respectively connected with the input ends of the first output waveguide, the second output waveguide, the third output waveguide and the fourth output waveguide; according to the invention, the array waveguide grating structure connected with the coupling module at the input end is adopted, so that the output spectrum of the adjacent output channels has large bandwidth, the large dynamic range of the adjacent channels during FBG wavelength demodulation is ensured, an optical waveguide width value different from a design value is adopted, the top end waveform of the output spectrum is regulated and controlled, and the demodulation precision is improved. On the premise of ensuring that the dynamic range of adjacent output channels is not changed, the resolution of the demodulation wavelength is improved; the device has the advantages of simple structure, large bandwidth, high crosstalk and high wavelength demodulation resolution.

Description

Technical Field

[0001] The invention relates to the technical field of photon integration, and in particular to a high crosstalk array waveguide grating structure that changes waveforms to improve demodulation resolution. Background Art

[0002] Arrayed waveguide grating (AWG) is based on the basic principle of linear interference between lights of different wavelengths, and can achieve efficient wavelength multiplexing and demultiplexing. It is a typical device for dense wavelength division multiplexing (DWDM) systems. Silicon-based materials are ideal devices for on-chip demodulation FBG (fiber Bragg grating) due to their high refractive index, low loss, high integration and easy batch manufacturing.

[0003] Typical arrayed waveguide gratings are limited by their own structural design. When demodulating FBG, the resolution and dynamic range of the FBG demodulation wavelength are mutually restricted, that is, the above two parameters cannot be optimized at the same time. If you want to improve the mutual restriction, the most effective method at present is to design the output spectrum in a targeted manner, increase the number of input channels, and increase the spectrum peak in each output channel. This method has high requirements on the dimensional accuracy of the AWG structure, resulting in increased process difficulty and cost.

[0004] Pustakhod et al. modified the input waveguide to add a second peak to the spectral response of each output channel of the AWG, thereby improving the measurement resolution while ensuring the dynamic range. (Reference: D.Pustakhod, E.Kleijn, K.Williams and X.Leijtens, "High-Resolution AWG-Based Fiber Bragg Grating Interrogator," IEEE Photonic.Tech.L., vol.28, no.20, pp.2203-2206, Oct.2016.); Yuan Pei et al. improved the structure based on this structure, and further expanded the dynamic range while slightly reducing the demodulation resolution (Reference: S.Weng, P.Yuan, L.Lu, D.Zhang, and L.Zhu, "SOI-based arrayed waveguide grating with extended dynamic range for fiber Bragg grating interrogator,” Opt.FiberTechnol., vol.68, Jan.2022, Art.no.102815.); The above structures all adopt the method of increasing the output spectral peak in a single output channel to alleviate the mutual constraints of resolution and dynamic range. The pre-designed interleaved output between the spectral peaks requires high dimensional accuracy of the arrayed waveguide grating structure, making the structure difficult to manufacture and expensive. Summary of the invention

[0005] In order to overcome the defects of the above-mentioned prior art, the purpose of the present invention is to propose a high crosstalk array waveguide grating structure that changes the waveform to improve the demodulation resolution. It can utilize the high crosstalk between adjacent output spectrums of the AWG and the slope of the spectrum waveform to regulate and control without increasing the number of input channels of the AWG and the difficulty of the process of AWG manufacturing, so as to improve the demodulation wavelength resolution while ensuring a large demodulation dynamic range. It has the advantages of simple structure, large bandwidth, high crosstalk, and high wavelength demodulation resolution.

[0006] In order to achieve the above object, the present invention adopts the following technical scheme:

[0007] A high crosstalk arrayed waveguide grating structure for changing waveforms to improve demodulation resolution comprises an input optical waveguide 1, the output end of the input optical waveguide 1 is connected to the input end of a coupling module 2, the output end of the coupling module 2 is sequentially connected to a first slab waveguide 3, an array waveguide 4 and a second slab waveguide 5, and the output end of the second slab waveguide 5 is respectively connected to the input ends of a first output waveguide 6, a second output waveguide 7, a third output waveguide 8 and a fourth output waveguide 9.

[0008] The coupling module 2 includes a tapered waveguide 21 and a tapered multimode interference coupler 22 . The input end of the tapered waveguide 21 is connected to the output end of the input optical waveguide 1 , and the output end of the tapered waveguide 21 is connected to the input end of the tapered multimode interference coupler 22 .

[0009] The central wavelength of the first output waveguide 6 is λ 6 , the central wavelength of the second output waveguide 7 is λ 7 , the central wavelength of the third output waveguide 8 is λ 8 , the central wavelengths of the fourth output waveguide 9 are λ 9 , and λ 6 -λ 7 =λ 7 -λ 8 =λ 8 -λ 9 =Δλ; where Δλ is the channel spacing between output waveguides.

[0010] The waveguide widths of the input optical waveguide 1 , the arrayed waveguide 4 , the first output waveguide 6 , the second output waveguide 7 , the third output waveguide 8 , and the fourth output waveguide 9 are consistent.

[0011] When the arrayed waveguide grating structure participates in demodulation, the following formula is used to perform wavelength demodulation on the unknown FBG between different output channels from the first output waveguide to the fourth output waveguide:

[0012]

[0013] Where: Δλ 6 is the half-peak bandwidth of the output spectrum of the first output waveguide 6, Δλ 7 is the half-peak bandwidth of the output spectrum of the second output waveguide 7, Δλ ？ is the half-peak bandwidth of the output spectrum of the unknown FBG.

[0014] The present invention has the following beneficial effects:

[0015] 1. The present invention adopts an arrayed waveguide grating structure connected to a coupling module at the input end, so that the output spectrum of adjacent output channels has a large bandwidth, ensuring a large dynamic range of adjacent channels when demodulating the FBG wavelength.

[0016] 2. The present invention adopts a light waveguide width value different from the design value to adjust the top waveform of the output spectrum, thereby improving the resolution of the demodulated wavelength while ensuring that the dynamic range of adjacent output channels remains unchanged.

[0017] 3. The present invention adopts an arrayed waveguide grating structure connected to a multimode interference coupler at the input end, so that the output spectra of adjacent output channels have high crosstalk, providing a new reference solution for FBG wavelength demodulation on an optical chip.

[0018] 4. The present invention adopts a large-bandwidth, high-crosstalk array waveguide grating structure, which reduces the side lobes of the output spectrum, reduces the influence of the optical waveguide size on the output spectrum, increases the tolerance of the optical chip process, and improves the manufacturing flexibility.

[0019] In summary, the structure of the present invention can improve the wavelength demodulation resolution of unknown FBG by changing the slope of the waveform and utilizing the high crosstalk between adjacent output spectra while ensuring a large dynamic range. BRIEF DESCRIPTION OF THE DRAWINGS

[0020] Figure 1 This is a schematic diagram of the overall structure of the arrayed waveguide grating structure provided by the present invention.

[0021] Figure 2 This is a schematic structural diagram of the coupling module 2 provided by the present invention.

[0022] Figure 3 This is a graph showing the output spectrum changes after passing through the coupling module 2 provided by the present invention.

[0023] Figure 4 This is an output spectrum diagram of the arrayed waveguide grating structure when the optical waveguide width provided by the present invention is the same as the designed value.

[0024] Figure 5 This is an output spectrum diagram of the arrayed waveguide grating structure when the optical waveguide width provided by the present invention is different from the designed value.

[0025] Figure 6 The working principle diagram of improving the wavelength resolution of FBG demodulation provided by the present invention, wherein: Figure 6 (a) is the principle of peak output spectrum demodulation, Figure 6 (b) The dome output spectrum demodulation principle.

[0026] Figure 7 This is a graph showing the improvement in wavelength resolution of the FBG demodulation provided by the present invention.

[0027] In the figure: 1-input optical waveguide; 2-coupling module, 21-tapered waveguide, 22-tapered multimode interference coupler; 3-first planar waveguide; 4-arrayed waveguide; 5-second planar waveguide; 6-first output waveguide; 7-second output waveguide; 8-third output waveguide; 9-fourth output waveguide. DETAILED DESCRIPTION

[0028] The technical solutions in the embodiments of the present invention are described clearly and completely below in conjunction with the accompanying drawings in the embodiments of the present invention.

[0029] like Figure 1 to Figure 2 As shown, a high crosstalk arrayed waveguide grating structure for changing waveform to improve demodulation resolution includes an input optical waveguide 1, the output end of the input optical waveguide 1 is connected to the input end of a coupling module 2, the output end of the coupling module 2 is sequentially connected to a first slab waveguide 3, an array waveguide 4, and a second slab waveguide 5, and the output end of the second slab waveguide 5 is respectively connected to the input ends of a first output waveguide 6, a second output waveguide 7, a third output waveguide 8, and a fourth output waveguide 9.

[0030] The coupling module 2 includes a tapered waveguide 21 and a tapered multimode interference coupler 22. The input end of the tapered waveguide 21 is connected to the output end of the input optical waveguide 1, and the output end of the tapered waveguide 21 is connected to the input end of the tapered multimode interference coupler 22. The output spectrum after passing through the coupling module changes as shown in FIG. Figure 3 shown.

[0031] The central wavelength of the first output waveguide 6 is λ 6 , the central wavelength of the second output waveguide 7 is λ 7 , the central wavelength of the third output waveguide 8 is λ 8 , the central wavelengths of the fourth output waveguide 9 are λ 9 , and λ 6 -λ 7 =λ 7 -λ 8 =λ 8 -λ 9 =Δλ; where Δλ is the channel spacing between output waveguides.

[0032] The waveguide widths of the input optical waveguide 1 , the arrayed waveguide 4 , the first output waveguide 6 , the second output waveguide 7 , the third output waveguide 8 , and the fourth output waveguide 9 are consistent and are collectively referred to as optical waveguide widths.

[0033] When the optical waveguide width is the initial design value, the spectrum passing through the arrayed waveguide grating structure is as follows: Figure 4 As shown, when the optical waveguide width is different from the initial design value, the spectrum through the arrayed waveguide grating structure is as follows Figure 5 shown.

[0034] When the arrayed waveguide grating structure participates in demodulation, the following formula is used to perform wavelength demodulation on the unknown FBG between different output channels from the first output waveguide to the fourth output waveguide:

[0035]

[0036] Where: Δλ 6is the half-peak bandwidth of the output spectrum of the first output waveguide 6, Δλ 7 is the half-peak bandwidth of the output spectrum of the second output waveguide 7, Δλ ？ is the half-peak bandwidth of the output spectrum of the unknown FBG.

[0037] The working principle of the present invention is:

[0038] like Figure 1 As shown, the input light enters the first slab waveguide 3, the array waveguide 4, and the second slab waveguide 5 from the input optical waveguide 1 through the coupling module 2, and then outputs the spectrum from the first output waveguide 6, the second output waveguide 7, the third output waveguide 8, and the fourth output waveguide 9 respectively.

[0039] When the coupling module 2 is not connected to the input end of the arrayed waveguide grating structure, the shape of the output spectrum is as follows: Figure 3 When the tapered waveguide 21 is connected to the input end of the arrayed waveguide grating structure, the shape of the output spectrum is as shown in FIG. Figure 3 As shown in the output spectrum B in FIG. 1 , relative to the output spectrum A, the output spectrum B achieves an increase in bandwidth; when the tapered multimode interference coupler 22 is connected to the input end of the arrayed waveguide grating structure, the shape of the output spectrum is as follows: Figure 3 As shown in the output spectrum C in FIG. , relative to the output spectrum B, the output spectrum C further achieves an increase in bandwidth so as to achieve high crosstalk between adjacent output spectra.

[0040] like Figure 4 As shown, when the optical waveguide width is consistent with the designed value, the output spectrum presents a dome with a large bandwidth and a high crosstalk level.

[0041] like Figure 5 As shown, when the optical waveguide width is different from the designed value, the output spectrum presents a peak with a large bandwidth and a high crosstalk level.

[0042] like Figure 6 As shown in (a), when the arrayed waveguide grating structure participates in demodulation, taking the first output channel 6 and the second output channel 7 as an example, the wavelength of the unknown FBG is demodulated. The shaded part P 6j is the output optical power of the spectral overlap part of the first output waveguide 6 and the unknown FBG, and the shaded part P 7j is the output optical power of the spectral overlap part of the second output waveguide 7 and the unknown FBG, and the wavelength of the unknown FBG is λ B , the unknown FBG wavelength can be demodulated using the following formula, and the output optical power P 6j And the output optical power P 7j The logarithmic ratio of the unknown FBG wavelength λ B There is a linear relationship between:

[0043]

[0044] Where: Δλ 7j is the half-peak bandwidth of the output spectrum of the second output waveguide 7, Δλ B is the half-peak bandwidth of the output spectrum of the unknown FBG.

[0045] like Figure 6 As shown in (b), the shaded part P 6a is the output optical power of the spectral overlap part of the first output waveguide 6 and the unknown FBG, and the shaded part P 7a is the output optical power of the spectral overlap part of the second output waveguide 7 and the unknown FBG, and the wavelength of the unknown FBG is λ B , the unknown FBG wavelength can be demodulated using the following formula, and the output optical power P 6a And the output optical power P 7a The logarithmic ratio of the unknown FBG wavelength λ B There is a linear relationship between:

[0046]

[0047] Where: Δλ 7a is the half-peak bandwidth of the output spectrum of the second output waveguide 7, Δλ B is the half-peak bandwidth of the output spectrum of the unknown FBG.

[0048] When the optical waveguide width is changed to a value different from the design value, the top of the output spectrum will change. In particular, when the optical waveguide width is reduced, a peak appears on the top of the array waveguide grating output spectrum, such as Figure 6 As shown in (a), compared with the dome, the output optical power changes more significantly, such as Figure 6 (b) shows that the slope will be larger and the slope will increase (d(logP 7j ) / dλ) / (d(logP 6j ) / dλ)-(d(logP 7a ) / dλ) / (d(logP 6a ) / dλ); for FBG wavelength λ B The demodulation resolution will be improved, such as Figure 7 As shown, the black dots represent the peak spectra, corresponding to Figure 6 (a), the red dots represent the dome spectra, corresponding to Figure 6 (b), demodulation resolution is improved Since only the value of the optical waveguide width changes, the other parameters of the arrayed waveguide grating do not change, so the wavelength interval and dynamic range are the same. Therefore, under the premise of ensuring the same dynamic range, this structure can be used. Figure 6As shown, by changing the slope of the waveform and utilizing the high crosstalk between adjacent output spectra, the wavelength demodulation resolution of the unknown FBG is improved.

Claims

1. A high crosstalk array waveguide grating structure for changing waveform to improve demodulation resolution, comprising an input optical waveguide (1), characterized in that: The output end of the input optical waveguide (1) is connected to the input end of the coupling module (2); the output end of the coupling module (2) is sequentially connected to the first slab waveguide (3), the array waveguide (4) and the second slab waveguide (5); the output end of the second slab waveguide 5 is respectively connected to the input ends of the first output waveguide (6), the second output waveguide (7), the third output waveguide (8) and the fourth output waveguide (9).

2. A high crosstalk arrayed waveguide grating structure for changing waveform to improve demodulation resolution according to claim 1, characterized in that: The coupling module (2) comprises a tapered waveguide (21) and a tapered multimode interference coupler (22); the input end of the tapered waveguide (21) is connected to the output end of the input optical waveguide (1); and the output end of the tapered waveguide (21) is connected to the input end of the tapered multimode interference coupler (22).

3. The high crosstalk arrayed waveguide grating structure for changing waveform to improve demodulation resolution according to claim 1, characterized in that: The central wavelength of the first output waveguide (6) is λ6, the central wavelength of the second output waveguide (7) is λ7, the central wavelength of the third output waveguide (8) is λ8, and the central wavelength of the fourth output waveguide (9) is λ9, and λ6-λ7=λ7-λ8=λ8-λ9=Δλ; wherein Δλ is the channel spacing between the output waveguides.

4. The high crosstalk arrayed waveguide grating structure for changing waveform to improve demodulation resolution according to claim 1, characterized in that: The waveguide widths of the input optical waveguide (1), the arrayed waveguide (4), the first output waveguide (6), the second output waveguide (7), the third output waveguide (8), and the fourth output waveguide (9) are consistent.

5. A high crosstalk arrayed waveguide grating structure for changing waveform to improve demodulation resolution according to claim 1 or 4, characterized in that: When the arrayed waveguide grating structure participates in demodulation, the following formula is used to perform wavelength demodulation on the unknown FBG between different output channels from the first output waveguide to the fourth output waveguide: Where: Δλ6 is the half-peak bandwidth of the output spectrum of the first output waveguide (6), Δλ7 is the half-peak bandwidth of the output spectrum of the second output waveguide (7), and Δλ ？ is the half-peak bandwidth of the output spectrum of the unknown FBG.

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