CN114089475B - Quasi-distributed fiber Bragg grating demodulation chip and bearing equipment - Google Patents
Quasi-distributed fiber Bragg grating demodulation chip and bearing equipment Download PDFInfo
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- CN114089475B CN114089475B CN202210024277.2A CN202210024277A CN114089475B CN 114089475 B CN114089475 B CN 114089475B CN 202210024277 A CN202210024277 A CN 202210024277A CN 114089475 B CN114089475 B CN 114089475B
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- G—PHYSICS
- G02—OPTICS
- G02B—OPTICAL ELEMENTS, SYSTEMS OR APPARATUS
- G02B6/00—Light guides; Structural details of arrangements comprising light guides and other optical elements, e.g. couplings
- G02B6/10—Light guides; Structural details of arrangements comprising light guides and other optical elements, e.g. couplings of the optical waveguide type
- G02B6/12—Light guides; Structural details of arrangements comprising light guides and other optical elements, e.g. couplings of the optical waveguide type of the integrated circuit kind
- G02B6/12007—Light guides; Structural details of arrangements comprising light guides and other optical elements, e.g. couplings of the optical waveguide type of the integrated circuit kind forming wavelength selective elements, e.g. multiplexer, demultiplexer
- G02B6/12009—Light guides; Structural details of arrangements comprising light guides and other optical elements, e.g. couplings of the optical waveguide type of the integrated circuit kind forming wavelength selective elements, e.g. multiplexer, demultiplexer comprising arrayed waveguide grating [AWG] devices, i.e. with a phased array of waveguides
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- G—PHYSICS
- G02—OPTICS
- G02B—OPTICAL ELEMENTS, SYSTEMS OR APPARATUS
- G02B6/00—Light guides; Structural details of arrangements comprising light guides and other optical elements, e.g. couplings
- G02B6/10—Light guides; Structural details of arrangements comprising light guides and other optical elements, e.g. couplings of the optical waveguide type
- G02B6/12—Light guides; Structural details of arrangements comprising light guides and other optical elements, e.g. couplings of the optical waveguide type of the integrated circuit kind
- G02B6/12007—Light guides; Structural details of arrangements comprising light guides and other optical elements, e.g. couplings of the optical waveguide type of the integrated circuit kind forming wavelength selective elements, e.g. multiplexer, demultiplexer
- G02B6/12009—Light guides; Structural details of arrangements comprising light guides and other optical elements, e.g. couplings of the optical waveguide type of the integrated circuit kind forming wavelength selective elements, e.g. multiplexer, demultiplexer comprising arrayed waveguide grating [AWG] devices, i.e. with a phased array of waveguides
- G02B6/12019—Light guides; Structural details of arrangements comprising light guides and other optical elements, e.g. couplings of the optical waveguide type of the integrated circuit kind forming wavelength selective elements, e.g. multiplexer, demultiplexer comprising arrayed waveguide grating [AWG] devices, i.e. with a phased array of waveguides characterised by the optical interconnection to or from the AWG devices, e.g. integration or coupling with lasers or photodiodes
- G02B6/12021—Comprising cascaded AWG devices; AWG multipass configuration; Plural AWG devices integrated on a single chip
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- G—PHYSICS
- G02—OPTICS
- G02B—OPTICAL ELEMENTS, SYSTEMS OR APPARATUS
- G02B6/00—Light guides; Structural details of arrangements comprising light guides and other optical elements, e.g. couplings
- G02B6/10—Light guides; Structural details of arrangements comprising light guides and other optical elements, e.g. couplings of the optical waveguide type
- G02B6/12—Light guides; Structural details of arrangements comprising light guides and other optical elements, e.g. couplings of the optical waveguide type of the integrated circuit kind
- G02B2006/12083—Constructional arrangements
- G02B2006/12107—Grating
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- G—PHYSICS
- G02—OPTICS
- G02B—OPTICAL ELEMENTS, SYSTEMS OR APPARATUS
- G02B6/00—Light guides; Structural details of arrangements comprising light guides and other optical elements, e.g. couplings
- G02B6/10—Light guides; Structural details of arrangements comprising light guides and other optical elements, e.g. couplings of the optical waveguide type
- G02B6/12—Light guides; Structural details of arrangements comprising light guides and other optical elements, e.g. couplings of the optical waveguide type of the integrated circuit kind
- G02B2006/12133—Functions
- G02B2006/12138—Sensor
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Abstract
The invention relates to a quasi-distributed fiber Bragg grating demodulation chip and a bearing device, comprising: light from a wide-spectrum light source enters a quasi-distributed fiber Bragg grating sensor array through a circulator, reflected wavelengths enter a 1 xN array waveguide grating through the circulator again, wavelengths lambada i reflected by each FBGi are respectively emitted from an output port i of the array waveguide grating, then pass through two Mach-Zehnder interferometers with fixed phase difference pi/2, and finally measure optical power through four photoelectric detectors.
Description
Technical Field
The invention relates to the field of quasi-distributed fiber bragg grating sensing-oriented photonic integrated demodulation chips, in particular to a quasi-distributed fiber bragg grating demodulation chip and bearing equipment.
Background
A Fiber Bragg Grating (FBG) senses a signal by using a principle that a central wavelength of reflected light varies with temperature or strain; compared with the traditional electronic sensor, the FBG-based optical fiber sensor has the characteristics of lightness, multi-channel multiplexing, electromagnetic interference resistance and suitability for extreme environments, and is widely applied to the fields of aerospace, energy, structural health detection, medical intelligent diagnosis and the like. The two major core components of the fiber grating sensor are a sensor and a demodulation system, the design and the preparation of the sensor are relatively mature, and the main problem limiting the further wide application of the fiber grating sensor is the demodulation of a sensing signal. Most of the traditional fiber Bragg grating demodulation equipment is assembled by discrete components, the demodulation principle comprises a tunable Fabry-Perot cavity, a diffraction grating matched CCD detection, wavelength tunable laser scanning, optical frequency domain reflection and the like, and the demodulator assembled based on the discrete components has the defects of large volume, high cost, poor reliability and difficulty in integration. The integrated photonic fiber grating demodulator has the advantages of high demodulation speed, high sensitivity, high reliability, no electromagnetic interference and the like; compared with the traditional demodulator composed of a plurality of discrete components, the demodulator can integrate the light source, the detector and the demodulation unit on a chip with the size of a few millimeters, thereby greatly reducing the cost and the volume of the demodulator. At present, the excellent performance of III-V materials in the aspect of active devices (light sources and detectors) and the characteristics of small size and low loss of silicon-based materials in the manufacture of passive devices (waveguides, arrayed waveguide gratings, micro-rings and the like) are combined, the III-V/Si hybrid integration technology is utilized, and a peripheral signal acquisition processing circuit is combined to perform chip-level integration on discrete devices of an optical fiber Bragg grating demodulator, so that attention is paid. At present, a chip scheme based on integrated photon demodulation mainly comprises three structures of an Arrayed Waveguide Grating (AWG), a Mach-Zehnder interferometer (MZI) and a micro-ring resonant cavity (MRR). The existing fiber grating demodulation chip based on silicon photoelectron integration has an AWG structure, the central wavelength is calculated by utilizing the power ratio between adjacent channels of the AWG, the demodulation chip based on the AWG structure has high requirements on the performance (channel uniformity, crosstalk between the channels and the like) of an AWG device, and because the process tolerance of a silicon optical platform is not high, the AWG with excellent performance is not easy to manufacture, so that the product-level application is difficult to realize at present on the silicon optical platform; the existing fiber grating demodulation chip based on silicon photoelectron integration also has a Mach-Zehnder interferometer structure, the performance of a single Mach-Zehnder interferometer structure can be quite good, but the demodulation chip can only demodulate a single fiber grating, and the requirement of quasi-distributed fiber grating sensing cannot be met by simple series connection or parallel connection. Therefore, in recent years, the research on the quasi-distributed fiber grating sensing chip based on the mach-zehnder interference structure of the silicon optical material has attracted attention.
Disclosure of Invention
In order to solve the problems that a silicon optical platform is insufficient in linear range and cannot meet the sensing requirements of a quasi-distributed fiber grating based on a single Mach-Zehnder interference structure, the invention provides the quasi-distributed fiber grating demodulation chip based on a cascaded Arrayed Waveguide Grating (AWG) and a double Mach-Zehnder interferometer (double-MZI) structure, the double-MZI structure can make up the problem that the linear range of demodulation is insufficient, and the structures of the cascaded AWG and MZI can demodulate a plurality of fiber Bragg grating sensors at the same time, so that the sensing requirements of the quasi-distributed fiber grating are met.
The purpose of the invention is realized by the following technical scheme:
the embodiment of the invention provides a quasi-distributed fiber Bragg grating demodulation chip, which comprises a wide spectrum light source, an optical circulator, an arrayed waveguide grating with 1 xN channels, N double Mach-Zehnder interferometer structures and 4N Ge photoelectric detectors, wherein the wide spectrum light source, the optical circulator, the arrayed waveguide grating with 1 xN channels, the N double Mach-Zehnder interferometer structures and the 4N Ge photoelectric detectors are sequentially connected in the propagation direction of an optical signal; light from the wide-spectrum light source enters N quasi-distributed Fiber Bragg Gratings (FBGs) through the optical circulator, the light is reflected by the quasi-distributed fiber Bragg gratings to become N reflection peaks with different wavelengths, the N reflection peaks with different wavelengths return to the optical circulator and are respectively emitted from the ith output port of the arrayed waveguide grating after being incident into the arrayed waveguide grating, i is a positive integer and is not less than 1 and not more than N, the reflection peaks of each quasi-distributed fiber Bragg grating are respectively output from the corresponding output ends of the arrayed waveguide grating, then pass through the corresponding double Mach-Zehnder interferometer structure and are finally respectively received by the four Ge photoelectric detectors, and the reading circuit deduces the central wavelength of the quasi-distributed fiber Bragg gratings according to the light power value received by the Ge photoelectric detectors.
In some embodiments, the input end of the arrayed waveguide grating is connected with the quasi-distributed fiber Bragg grating through a grating coupler; the output end of the arrayed waveguide grating is respectively connected with the corresponding double Mach-Zehnder interferometer structures through a 2 multiplied by 2 multimode interference coupler, and the channel interval of the arrayed waveguide grating is related to the wavelength demodulation dynamic range of the optical fiber Bragg grating.
In some embodiments, the double mach-zehnder interferometer structure includes a first 2 × 2 multimode interference coupler, a second 2 × 2 multimode interference coupler, a 1 × 2 multimode interference coupler, a first mach-zehnder interferometer, a second mach-zehnder interferometer, a first 2 × 2 directional coupler, and a second 2 × 2 directional coupler, wherein one of the input terminals of the first 2 × 2 multimode interference coupler is connected to a corresponding output terminal of the arrayed waveguide grating, one of the output terminals of the first 2 × 2 multimode interference coupler is connected to one of the input terminals of the second 2 × 2 multimode interference coupler, another output terminal of the first 2 × 2 multimode interference coupler is connected to an input terminal of the 1 × 2 multimode interference coupler, an output terminal of the second 2 × 2 multimode interference coupler is connected to an input terminal of the first 2 × 2 directional coupler via the first mach-zehnder interferometer, the output end of the 1 × 2 multimode interference coupler is connected with the input end of the second 2 × 2 directional coupler through the second mach-zehnder interferometer, and the two output ends of the first 2 × 2 directional coupler and the two output ends of the second 2 × 2 directional coupler are respectively and correspondingly connected with 4 Ge photodetectors.
In some embodiments, the optical signals output by the two output terminals of the first 2 × 2 multimode interference coupler have equal power and are out of phase by pi/2, so that the phase difference between the first mach-zehnder interferometer and the second mach-zehnder interferometer is locked to pi/2.
In some embodiments, the coupling region length of the first 2 x 2 directional coupler and the coupling region length of the second 2 x 2 directional coupler are adjustable such that the magnitude of the extinction ratio of the first mach-zehnder interferometer to the second mach-zehnder interferometer is adjustable.
In some embodiments, the Ge photodetector is made of a Ge material epitaxial on a silicon waveguide, the Ge photodetector has three metal electrodes with a reverse bias voltage, the three metal electrodes are in a GSG (Ground-signal-Ground) structure, light from the double mach-zehnder interferometer structure is horizontally incident on the Ge photodetector through the silicon waveguide, and the optical power of the incident light is reversely deduced through the measured current.
In a second aspect of the embodiments of the present invention, a carrier device is provided, which includes a carrier and the quasi-distributed fiber bragg grating demodulation chip of any one of the first aspect, where the demodulation chip is accommodated in the carrier.
In some embodiments, the carrier device comprises a composite material, the carrier is a main body of the composite material, the quasi-distributed fiber bragg grating center wavelength information derived by the demodulation chip comprises strain and temperature information of the main body, and the composite material comprises at least one of a resin-based composite material, a ceramic-based composite material and a metal-based composite material; or the like, or, alternatively,
the bearing device comprises medical health equipment, the bearing body comprises a probe of the medical health equipment, and the quasi-distributed fiber Bragg grating central wavelength information deduced by the demodulation chip comprises the heart rate and/or body temperature information of a human body monitored by the probe of the medical health equipment.
In some embodiments, the carrier device includes an aircraft, the carrier includes a wing of the aircraft, and the quasi-distributed fiber bragg grating center wavelength information derived by the demodulation chip includes three-dimensional shape, strain and temperature information of the wing.
In some embodiments, the aircraft comprises an unmanned aerial vehicle or a helicopter.
The invention has the following beneficial effects: the demodulation chip based on the cascade array waveguide grating and the double-Mach-Zehnder interferometer structure can realize the quasi-distributed fiber Bragg grating sensing, and the number and the wavelength variation range of the fiber Bragg gratings can be flexibly designed by respectively changing the number of the array waveguide grating channels and the free spectral range of the Mach-Zehnder interferometer structure; moreover, the double Mach-Zehnder interferometer structure utilizing the inherent phase difference pi/2 can realize high-sensitivity linear demodulation in the whole wavelength range; the demodulation chip is realized in a silicon optical platform except for an integrated broadband light source, so that the size and the cost of a device can be greatly reduced.
Drawings
FIG. 1 is a block diagram of a quasi-distributed fiber grating demodulation chip system based on a cascaded arrayed waveguide grating and a double Mach-Zehnder interferometer structure according to the present invention.
FIG. 2 is a schematic diagram of the structure of a 1 XN-channel arrayed waveguide grating according to the present invention.
Fig. 3 is a schematic diagram of a wavelength demodulation unit with a dual MZI structure according to the present invention.
Fig. 4 is a transmission curve of the fiber bragg grating according to the present invention.
Fig. 5 is a transmission curve of four output channels of the wavelength demodulation unit with the dual MZI structure of the present invention.
Fig. 6 is a demodulation curve of the dual MZI structure wavelength demodulation unit of the present invention.
FIG. 7 is an enlarged schematic diagram of the linear region of the demodulation curve of the dual MZI structure of the present invention.
Fig. 8 is a demodulation curve of the dual MZI structure wavelength demodulation unit of the present invention over a large wavelength range.
FIG. 9 is a single channel transmission curve of a cascaded arrayed waveguide grating and a single Mach-Zehnder interferometer of the present invention.
FIG. 10 is a single channel transmission curve of the cascaded arrayed waveguide grating and the double Mach-Zehnder interferometer of the present invention.
FIG. 11 is a demodulation curve of the cascaded arrayed waveguide grating and the double Mach-Zehnder interferometer of the present invention.
Reference numerals:
1-wide spectrum light source (ASE or SLD), 2-arrayed waveguide grating, 3-double Mach-Zehnder interferometer structure, 4-optical circulator, 5-signal readout circuit, 6-Ge photodetector, 20-AWG input channel, 21-AWG input slab waveguide, 22-AWG output slab waveguide, 23-AWG arrayed waveguide region, 24, 25, 26, 27, 28-AWG output channel, 30, 31-2 x 2 multimode interference coupler, 32-1 x 2 multimode interference coupler, 33, 34-Mach-Zehnder interferometer, 35, 36-2 x 2 directional coupler, 301, 302, 303, 304, 305, 306-grating coupler, 307-double MZI structure and AWG connection point.
Detailed Description
Reference will now be made in detail to the exemplary embodiments, examples of which are illustrated in the accompanying drawings. When the following description refers to the accompanying drawings, like numbers in different drawings represent the same or similar elements unless otherwise indicated. The embodiments described in the following exemplary embodiments do not represent all embodiments consistent with the present application. Rather, they are merely examples of apparatus and methods consistent with certain aspects of the present application, as detailed in the appended claims.
The terminology used herein is for the purpose of describing particular embodiments only and is not intended to be limiting of the application. As used in this application and the appended claims, the singular forms "a", "an", and "the" are intended to include the plural forms as well, unless the context clearly indicates otherwise. It should also be understood that the term "and/or" as used herein refers to and encompasses any and all possible combinations of one or more of the associated listed items.
It is to be understood that although the terms first, second, third, etc. may be used herein to describe various information, such information should not be limited to these terms. These terms are only used to distinguish one type of information from another. For example, first information may also be referred to as second information, and similarly, second information may also be referred to as first information, without departing from the scope of the present application. The word "if," as used herein, may be interpreted as "at.
It should be noted that, in the following examples and embodiments, features may be combined with each other without conflict.
The invention is further described below with reference to the accompanying drawings.
As shown in fig. 1, a quasi-distributed fiber bragg grating demodulation chip based on a cascaded Arrayed Waveguide Grating (AWG) and a double mach-zehnder interferometer structure (double-MZI, hereinafter, the double mach-zehnder interferometer structure may also be referred to as a double MZI structure) structure is designed and manufactured on a silicon optical material platform, and includes a wide spectrum light source 1, an optical circulator 4, an arrayed waveguide grating 2 with 1 × N channels, N double MZI structures 3, and 4N Ge photodetectors 6, which are connected in sequence along an optical signal propagation direction, and further includes a readout circuit 5, and an output end of the Ge photodetector 6 is connected to the readout circuit 5; light from the wide-spectrum light source 1 is incident to N quasi-distributed Fiber Bragg Gratings (FBGs) through the optical circulator 4, and is reflected by the fiber bragg gratings to become N reflection peaks with different wavelengths, the N reflection peaks with different wavelengths return to the optical circulator 4 and are incident to the arrayed waveguide grating 2 to be emitted from the ith (i =1, 2, 3.. N) output port of the arrayed waveguide grating respectively, each fiber bragg grating reflection peak is output from the corresponding arrayed waveguide grating output end respectively, then passes through the corresponding double-mach-zender interferometer 3 structure and finally is received by four Ge photoelectric detectors 6 respectively, and the readout circuit 5 calculates the central wavelength of the fiber bragg gratings according to the value of the light power received by the Ge photoelectric detectors.
The demodulation chip based on the cascade array waveguide grating and the double-Mach-Zehnder interferometer structure in the embodiment of the invention can realize quasi-distributed fiber Bragg grating sensing, and the number and the wavelength variation range of the fiber Bragg grating can be flexibly designed by respectively changing the number of the array waveguide grating channels and the free spectral range of the Mach-Zehnder interferometer structure; moreover, the double Mach-Zehnder interferometer structure utilizing the inherent phase difference pi/2 can realize high-sensitivity linear demodulation in the whole wavelength range; the demodulation chip can be realized in a silicon optical platform except for the rest devices of the integrated broadband light source, so that the size and the cost of the device are greatly reduced.
As shown in fig. 2, a schematic diagram of a 1 × N channel arrayed waveguide grating structure provided in the embodiment of the present invention is shown. The array waveguide grating 2 is composed of an input end 20, an input flat waveguide 21, an array waveguide region 23, an output flat waveguide 22 and a plurality of output ends 24, 25, 26, 27 and 28, wherein the input end 20 of the array waveguide grating 2 is connected with the optical circulator 4 through a grating coupler; each output end of the arrayed waveguide grating 2 is connected with the corresponding double MZI structure 3 through a 2 multiplied by 2 multimode interference coupler 30, the number of the output ends corresponds to the number of the fiber grating sensors, and the channel interval of the arrayed waveguide grating is related to the wavelength dynamic range of the fiber grating sensors.
In an embodiment of the present invention, the dual mach-zehnder interferometer structure includes a first 2 × 2 multimode interference coupler (i.e., 30 in fig. 3), a second 2 × 2 multimode interference coupler (i.e., 31 in fig. 3), a 1 × 2 multimode interference coupler (i.e., 32 in fig. 3), a first mach-zehnder interferometer (i.e., 33 in fig. 3), a second mach-zehnder interferometer (i.e., 34 in fig. 3), a first 2 × 2 directional coupler (i.e., 35 in fig. 3), and a second 2 × 2 directional coupler (i.e., 36 in fig. 3), wherein one of the input terminals of the first 2 × 2 multimode interference coupler is connected to a corresponding output terminal of the arrayed waveguide grating, one of the output terminals of the first 2 × 2 multimode interference coupler is connected to one of the input terminals of the second 2 × 2 multimode interference coupler, and the other output terminal of the first 2 × 2 multimode interference coupler is connected to the input terminal of the 1 × 2 multimode interference coupler, the output end of the second 2 x 2 multimode interference coupler is connected with the input end of the first 2 x 2 directional coupler through the first mach-zehnder interferometer, the output end of the 1 x 2 multimode interference coupler is connected with the input end of the second 2 x 2 directional coupler through the second mach-zehnder interferometer, and the two output ends of the first 2 x 2 directional coupler and the two output ends of the second 2 x 2 directional coupler are respectively and correspondingly connected with 4 Ge photoelectric detectors. The optical signals output by the two output ends of the first 2 multiplied by 2 multimode interference coupler have equal power and the phase difference is pi/2, so that the phase difference between the first Mach-Zehnder interferometer and the second Mach-Zehnder interferometer is locked to be pi/2. The length of the coupling area of the first 2 x 2 directional coupler and the length of the coupling area of the second 2 x 2 directional coupler are adjustable, so that the size of the extinction ratio of the first Mach-Zehnder interferometer and the second Mach-Zehnder interferometer is adjustable.
As shown in fig. 3, the dual MZI structure 3 is mainly composed of a 2 × 2 multimode interference coupler 30, a 2 × 2 multimode interference coupler 31, a 1 × 2 multimode interference coupler 32, mach- zehnder interferometers 33, 34, and 2 × 2 directional couplers 35, 36. Light from the output of the arrayed waveguide grating 2 enters the dual MZI structure demodulation unit through the connection point 307 of the dual MZI structure and the AWG. The 2 × 2 multimode interference coupler 30 is a common type 3dB multimode interference coupler, and according to the self-imaging principle (self-imaging effect), an optical signal at an input end is divided into two optical signals with equal power and pi/2 phase difference at an output end, wherein one optical signal enters the 2 × 2 multimode interference coupler 31, and the other optical signal enters the 1 × 2 multimode interference coupler 32. Since the phase difference between the two output ports of the 2 × 2 multimode interference coupler 31 is pi/2 and the phase difference between the two output ports of the 1 × 2 multimode interference coupler 32 is equal, the phase difference between the mach-zehnder interferometer 33 and the mach-zehnder interferometer 34 is locked to be pi/2. The extinction ratio of the Mach-Zehnder interferometer is mainly determined by the splitting ratio of the input end, the splitting ratio of the output end and the loss on the arm, and the reason why the Mach-Zehnder interferometer adopts the 2 multiplied by 2 directional couplers 35 and 36 as the output end is that the splitting ratio of the directional couplers can be adjusted arbitrarily by changing the length of the coupling areas 35 and 36, and then the extinction ratio of the Mach-Zehnder interferometer is changed. The demodulation chip of the invention expects that the extinction ratio of the double MZI structure cannot be too large or too small, the requirement on a rear reading circuit is high if the extinction ratio is too large, and the demodulation sensitivity is low if the extinction ratio is too small, so that the comprehensive consideration is needed according to the requirements of the processing capacity and the sensitivity of the circuit. The free spectral range of the mach-zehnder interferometer is determined by the dynamic range of the FBG measurement, which is determined by the wavelength and the optical length difference of the two arms, and the transmission curve of the FBG reflected signal is shown in fig. 4. The light emitted from the double MZI structure 3 can be detected by an InGaAs material detector, and in this case, the vertical optical coupling is required to be performed by the grating couplers 301, 302, 303, 304, 305 and 306 in a hybrid integration mode, and the horizontal optical coupling can be performed by a waveguide and a Ge photodetector.
As shown in fig. 5, the transmission curves of the four output channels of the wavelength demodulation unit with the dual MZI structure of the present invention are shown. The thin solid line and the thin dotted line respectively represent transmission curves of two output ports of the mach-zehnder interferometer 33, the two output ports of the mach-zehnder interferometer 33 are vertically coupled through the grating coupler 301 and the grating coupler 302 respectively and received by the two Ge photoelectric detectors, the ratio of the optical power detected by the two detectors and the central wavelength value of the optical fiber bragg grating have a corresponding relationship, and the size of the central wavelength can be deduced reversely according to the size of the optical power ratio; the thick solid line and the thick dotted line respectively represent transmission curves of two output ports of the mach-zehnder interferometer 34, the two output ports of the mach-zehnder interferometer 34 are vertically coupled through the grating coupler 303 and the grating coupler 304 respectively and received by the two Ge photoelectric detectors, the ratio of the optical power detected by the two detectors and the central wavelength value of the optical fiber bragg grating also have a corresponding relation, and the size of the central wavelength can be deduced reversely according to the size of the optical power ratio. Since the two mach-zehnder interferometers are identical in structural design, their extinction ratios and free spectral ranges are also identical, the only difference being that the transmission curve is shifted by a quarter of the free spectral range due to the inherent pi/2 phase difference.
As shown in fig. 6, the demodulation curves (adjacent channel power ratio vs wavelength) of the dual MZI structure wavelength demodulation unit of the present invention are shown. The solid black line shows the relationship between the power ratio and wavelength of the adjacent channel of the first MZI, and the dashed black line shows the relationship between the power ratio and wavelength of the adjacent channel of the other MZI. As can be seen from the figure, the period of the MZI demodulation curve is consistent with the size of the free spectral range, the demodulation curve shapes of the two MZIs are basically consistent, and the two MZIs are relatively shifted by a quarter period; the slope of the demodulation curve represents the sensitivity of the demodulation, which is required to be high if sensitivity is desired, but this sacrifices the free spectral range. Amplifying and displaying the linear area of the demodulation curve in fig. 6 and performing linear fitting, as shown in fig. 7; by performing an expansion of the demodulation curve in fig. 6 over the full wavelength range, as shown in fig. 8, it can be seen that the consistency of the demodulation curve over the full wavelength range is very good.
As shown in fig. 9, the single channel transmission curve of the cascaded arrayed waveguide grating and the single mach-zehnder interferometer of the present invention. The solid black line and the dashed black line respectively represent transmission curves of two output ports of the arrayed waveguide grating and mach-zehnder interferometer cascade structure, and can also be understood as a superposition of the transmission curves of two devices independently. As shown in fig. 10, a single-channel transmission curve of the cascaded arrayed waveguide grating and the double mach-zender interferometer of the present invention represents a case of one output channel of the arrayed waveguide grating and also represents a case of demodulating one FBG sensor, and the four curves represent transmission curves of four output ports of the cascaded structure of the arrayed waveguide grating and the double mach-zender interferometer, respectively. As shown in fig. 11, the demodulation curves of the cascaded arrayed waveguide grating and the double mach-zehnder interferometer of the present invention are shown. The solid black line and the dashed black line represent the relationship between the power ratio and the wavelength of two MZI adjacent channels, respectively.
The invention is based on advanced integrated photon technology, the size of the whole chip is very small, and the size is 10 millimeters (mm) multiplied by 10 millimeters (mm); in addition, since a plurality of demodulation chips can be processed simultaneously on one wafer, the cost is relatively low. The quasi-distributed fiber Bragg grating demodulation chip can be applied to various application scenes, such as structural health monitoring of composite materials in the aerospace field, detection of strain/three-dimensional shapes of wings of airplanes and unmanned planes and monitoring of human body temperature in the medical health field. For example, most of the ship body materials of the existing aerospace field satellite, rocket, space plane and other equipment use composite materials, and the quasi-distributed fiber bragg grating is embedded into the composite materials, so that the composite materials can be subjected to real-time material damage monitoring; for example, in the field of aircrafts, the quasi-distributed fiber bragg grating is mounted on the surface of a wing or a rotor wing, so that the strain and the three-dimensional shape of the wing or the rotor wing in the operation process can be monitored; for example, in the field of medical health, the quasi-distributed fiber bragg grating is integrated into clothes of patients or medical equipment, and various physiological indexes (heart rate, body temperature and the like) of human bodies can be monitored in real time.
The demodulation chip based on the cascaded arrayed waveguide grating and the double-mach-zender interferometer structure as shown in fig. 1 can be realized on a platform of silicon (Si) material, silicon nitride (Si 3N 4) or indium phosphide (InP) and the like. The silicon (Si) material platform has the advantages that the size can be made very small, a photoelectric detector can be integrated, the optical loss is moderate, but the defects that a light source cannot be integrated and the temperature is sensitive are overcome; the silicon nitride (Si 3N 4) material platform has the advantage that waveguide loss can be made very low and moderate in size, but has the disadvantage that it is inconvenient to integrate light sources and photodetectors; indium phosphide (InP) material platforms have the advantage of monolithic integration with light sources and photodetectors, but are expensive and large in size.
It should be noted that an embodiment of the present invention further provides a carrier device, where the carrier device may include a carrier and the quasi-distributed fiber bragg grating demodulation chip in the foregoing embodiment, where the quasi-distributed fiber bragg grating demodulation chip is accommodated in the carrier.
For example, in some embodiments, the carrier device includes a composite material, the carrier is a main body of the composite material, and the fiber bragg grating central wavelength information derived by the demodulation chip includes strain and temperature information of the main body. The composite material includes at least one of a resin-based, ceramic-based, and metal-based composite material. Illustratively, the composite material is resin-based, or the composite material is ceramic-based, or the composite material is metal-based composite material. For example, most of the existing ship body materials of the equipment in the aerospace field, such as satellites, rockets, space shuttles and the like, use composite materials, and the quasi-distributed fiber bragg grating is embedded in the composite materials, so that real-time material damage monitoring can be carried out on the composite materials.
In some embodiments, the carrier device includes an aircraft, the carrier includes a wing of the aircraft, and the fiber bragg grating center wavelength information derived by the demodulation chip includes three-dimensional shape, strain and temperature information of the wing. For example, in the field of aircrafts, the quasi-distributed fiber bragg grating is mounted on the surface of a wing or a rotor wing, so that the strain and the three-dimensional shape of the wing or the rotor wing in the operation process can be monitored.
In some embodiments, the carrier device includes a medical health device, the carrier includes a probe of the medical health device, and the fiber bragg grating center wavelength information derived by the demodulation chip includes information of a heart rate and/or a body temperature of a human body monitored by the probe of the medical health device. For example, in the field of medical health, the quasi-distributed fiber bragg grating is integrated into clothes of patients or medical equipment, and various physiological indexes (heart rate, body temperature and the like) of human bodies can be monitored in real time.
The above description is only exemplary of the present application and should not be taken as limiting the present application, as any modification, equivalent replacement, or improvement made within the spirit and principle of the present application should be included in the scope of protection of the present application.
Claims (9)
1. A quasi-distributed fiber Bragg grating demodulation chip is characterized by comprising a wide spectrum light source, an optical circulator, an array waveguide grating with 1 xN channels, N double Mach-Zehnder interferometer structures and 4N Ge photoelectric detectors which are sequentially connected according to the propagation direction of an optical signal, and a reading circuit, wherein the output end of the Ge photoelectric detector is connected with the reading circuit, the array waveguide grating is provided with 1 input end and N output ends, the N output ends of the array waveguide grating are connected with the input ends of the N double Mach-Zehnder interferometer structures, each double Mach-Zehnder interferometer structure comprises 4 output ends, and each output end of each double Mach-Zehnder interferometer structure is correspondingly connected with one Ge photoelectric detector; light from a wide-spectrum light source is incident to N quasi-distributed Fiber Bragg Gratings (FBGs) through an optical circulator and is reflected by the quasi-distributed fiber Bragg gratings to form N reflection peaks with different wavelengths, the N reflection peaks with different wavelengths return to the optical circulator and are respectively emitted from the ith output port of the arrayed waveguide grating after being incident into the arrayed waveguide grating, i is a positive integer and is not less than 1 and not more than N, the reflection peaks of each quasi-distributed fiber Bragg grating are respectively output from the corresponding output ends of the arrayed waveguide grating, then pass through the corresponding double Mach-Zehnder interferometer structure and are finally respectively received by four Ge photoelectric detectors, and a reading circuit deduces the central wavelength of the quasi-distributed fiber Bragg gratings according to the light power value received by the Ge photoelectric detectors;
the double Mach-Zehnder interferometer structure comprises a first 2 x 2 multimode interference coupler, a second 2 x 2 multimode interference coupler, a 1 x 2 multimode interference coupler, a first Mach-Zehnder interferometer, a second Mach-Zehnder interferometer, a first 2 x 2 directional coupler and a second 2 x 2 directional coupler, wherein one input end of the first 2 x 2 multimode interference coupler is connected with a corresponding output end of the arrayed waveguide grating, one output end of the first 2 x 2 multimode interference coupler is connected with one input end of the second 2 x 2 multimode interference coupler, the other output end of the first 2 x 2 multimode interference coupler is connected with the input end of the 1 x 2 multimode interference coupler, the output end of the second 2 x 2 multimode interference coupler is connected with the input end of the first 2 x 2 directional coupler through the first Mach-Zehnder interferometer, the output end of the 1 × 2 multimode interference coupler is connected with the input end of the second 2 × 2 directional coupler through the second mach-zehnder interferometer, and the two output ends of the first 2 × 2 directional coupler and the two output ends of the second 2 × 2 directional coupler are respectively and correspondingly connected with 4 Ge photodetectors.
2. The demodulation chip of the quasi-distributed fiber bragg grating as claimed in claim 1, wherein the input end of the arrayed waveguide grating is connected with the quasi-distributed fiber bragg grating through a grating coupler; the output end of the arrayed waveguide grating is respectively connected with the corresponding double Mach-Zehnder interferometer structures through a 2 multiplied by 2 multimode interference coupler, and the channel interval of the arrayed waveguide grating is related to the wavelength demodulation dynamic range of the optical fiber Bragg grating.
3. The quasi-distributed fiber bragg grating demodulation chip of claim 1, wherein optical signals output by two output ends of the first 2 x 2 multimode interference coupler have equal power and have a phase difference of pi/2, so that the phase difference between the first mach-zehnder interferometer and the second mach-zehnder interferometer is locked to be pi/2.
4. The quasi-distributed fiber bragg grating demodulation chip of claim 1, wherein the coupling region length of the first 2 x 2 directional coupler and the coupling region length of the second 2 x 2 directional coupler are adjustable, so that the extinction ratio of the first mach-zehnder interferometer and the second mach-zehnder interferometer is adjustable.
5. The quasi-distributed fiber bragg grating demodulation chip according to claim 1, wherein the Ge photodetector is made of a Ge material epitaxial on a silicon waveguide, the Ge photodetector has three metal electrodes to which a reverse bias voltage is applied, the three metal electrodes are of a GSG structure, light from the double mach-zender interferometer horizontally enters the Ge photodetector through the silicon waveguide, and the optical power of the incident light is reversely deduced through the measured current.
6. A carrier device comprising a carrier and the quasi-distributed fiber bragg grating demodulation chip of any one of claims 1 to 5, wherein the demodulation chip is accommodated in the carrier.
7. The carrier device of claim 6, wherein the carrier device comprises a composite material, the carrier is a main body of the composite material, the quasi-distributed fiber Bragg grating center wavelength information derived by the demodulation chip comprises strain and temperature information of the main body, and the composite material comprises at least one of a resin-based composite material, a ceramic-based composite material and a metal-based composite material; or the like, or, alternatively,
the bearing device comprises medical health equipment, the bearing body comprises a probe of the medical health equipment, and the quasi-distributed fiber Bragg grating central wavelength information deduced by the demodulation chip comprises the heart rate and/or body temperature information of a human body monitored by the probe of the medical health equipment.
8. The carrying device according to claim 6, wherein the carrying device comprises an aircraft, the carrying body comprises a wing of the aircraft, and the quasi-distributed fiber Bragg grating center wavelength information derived by the demodulation chip comprises three-dimensional shape, strain and temperature information of the wing.
9. The carrier apparatus of claim 8, wherein the aircraft comprises an unmanned aerial vehicle or a helicopter.
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