CN203534963U - SPR (Surface Plasma Resonance) optical fiber sensor based on frequency modulation spectrum principle - Google Patents
SPR (Surface Plasma Resonance) optical fiber sensor based on frequency modulation spectrum principle Download PDFInfo
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- CN203534963U CN203534963U CN201320584004.XU CN201320584004U CN203534963U CN 203534963 U CN203534963 U CN 203534963U CN 201320584004 U CN201320584004 U CN 201320584004U CN 203534963 U CN203534963 U CN 203534963U
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Abstract
The utility model discloses an SPR (Surface Plasma Resonance) optical fiber sensor based on frequency modulation spectrum principle. One end of a light source is connected with an EOM (Electro Optic Modulator) photoelectric modulation circuit; one end of the EOM photoelectric modulation circuit is connected with an SPR sensor; the other ends of the SPR sensor and the EOM photoelectric modulation circuit are co-connected with an interference circuit; the interference circuit is connected with the photoelectric modulation circuit, a pre-amplification circuit, an A/D (Analog-to-Digital) conversion circuit, a step wave driving circuit and a digital integrating circuit; the digital integrating circuit is connected with a step incremental integration circuit, a D/A switching circuit, a step wave driving circuit and a frequency modulation circuit, the frequency modulation circuit is connected with the other end of the light source, so as to form a power loop of the SPR optical fiber sensor. The SPR optical fiber sensor disclosed by the utility model is based on the frequency modulation spectrum principle, and with the combination of digital modulation technology and closed loop control, rapid locking on SPR absorption peak change under refractive index change modulation is achieved.
Description
Technical field
The utility model relates to Automatic Detection and Control technology and surface plasma body resonant vibration (surface plasmon resonance, SPR) Fibre Optical Sensor field, is specifically related to the SPR Fibre Optical Sensor based on frequency modulation spectral principle.
Background technology
Utilize the medium/metal interface SPR effect resonant wavelength can responsive response environment medium dielectric property or refractive index and variation thereof and the SPR optical sensor developed, because of its advantage in measuring accuracy and sensitivity, in aspect extensive application such as biomedicine, biological chemistry and physics.SPR Fibre Optical Sensor, combines Fibre Optical Sensor and SPR effect advantage, is one of important focus in spr sensor and application thereof.
At present, in SPR Fibre Optical Sensor and applied research thereof, structurally adopt single light path design, to all kinds of optical noises of introducing in light source intensity fluctuation, sensing light path, lack necessary endogeny and suppress mechanism.On signal is processed, adopt the Spectrographic mensuration under wideband light source excitation, determine that SRP centre wavelength is with variation to be measured, need, by spectral analysis tools such as spectrometers, can not meet and be applied to on-line measurement needs.
SPR Fibre Optical Sensor, in essence based on the modulation to optical fiber sensor head resonance absorption wavelength to be measured, by the resonant wavelength changing is measured, realizes the mensuration to environment refractive index and variation thereof.In Spectrographic measurement scheme, because absorption peak place the first derivative spectra value is almost equal to zero, absorb light intensity insensitive to the response of resonant wavelength variation.Correspondingly, can to realize measuring accuracy limited for sensor.Specifically, establishing the absorption spectra function of optical fiber sensor head based on SRP effect is
,
with
survey respectively light center frequency and SPR formant frequency.In Spectrographic is measured, surveying light has with respect to absorption peak
during frequency shift (FS), generation is proportional to
absorption light intensity change, by the measurement that this light intensity is changed, realize determining of sensing head absorption peak and variation thereof, determine refractive index to be measured and variation thereof.
determining
, make to change and determine that absorbent core wavelength has precision limited, testing medium detecting refractive index precision and sensitivity deterioration based on light intensity.Importantly, this deteriorated of metering system that come from, be in Spectrographic measurement scheme follow-up signal and data processing link insurmountable.
Summary of the invention
The purpose of this utility model is: provide a kind of SPR Fibre Optical Sensor based on frequency modulation spectral principle, from frequency modulation spectral principle, in conjunction with Digital Modulation and Closed loop Control, for on-line measurement.
Technical solution of the present utility model is: this SPR Fibre Optical Sensor comprises SPR sensing head, interfere circuit, photoelectric switching circuit, pre-amplification circuit, A/D change-over circuit, demodulator circuit, digital integrating circuit, step incremental integration circuit, D/A change-over circuit, staircase waveform driving circuit, frequency modulation circuit, light source and EOM photoelectricity modulation circuit, one end of light source connects EOM photoelectricity modulation circuit, one end of EOM photoelectricity modulation circuit connects SPR sensing head, SPR sensing head, the other end of EOM photoelectricity modulation circuit connects interference circuit altogether, interfere circuit to connect photoelectric switching circuit, pre-amplification circuit, A/D change-over circuit, demodulator circuit and digital integrating circuit, digital integrating circuit connects step incremental integration circuit, D/A change-over circuit, staircase waveform driving circuit and frequency modulation circuit, frequency modulation circuit connects the other end of light source, the whole electric loop that forms SPR Fibre Optical Sensor.
During work, centre frequency tunable laser is light source, and its output light is divided into two by a Y type coupling mechanism after EOM carries out narrow-band frequency modulation: phase differential
, isocandela two-beam, input respectively the optic fibre light path of two symmetries, wherein a light path comprises based on SPR effect transmission-type sensing head; Detection optical fiber, reference optical fiber will be exported separately light via a Y type coupling mechanism again and " unite two into one ", after mutually interfering, act on photodetector, record the square wave photo-signal containing the frequency selectivity resonance absorption information based on SPR effect; Photo-signal is after pre-amplification circuit, A/D change-over circuit and demodulator circuit signal condition are processed, and acquisition amplitude is proportional to the square wave photo-signal of surveying difference on the frequency between light fundamental frequency centre frequency and SPR effect resonance absorption peak center; This signal, through digital integration processing, D/A conversion, acts on light source as negative feedback control signal, and light source center frequency is modulated, and makes it under close loop negative feedback control action gradually in SPR effect absorption peak centre frequency; When the two is consistent, photocurrent square wave amplitude is zero, and light source center Frequency Locking is in SPR effect absorption peak centre frequency; After factor causes refractive index to change arbitrarily, system repeats said process, by negative feedback, is again locked in new absorption peak centre frequency; Modulated square wave in locking process is corresponding to corresponding frequencies side-play amount.
The utlity model has following advantage:
1, based on to surveying the narrow-band frequency modulation of light, realize with single order differential absorption spectra and substitute Spectrographic measurement, improve frequency sensitivity or the resolution of optical fiber SPR sensor.
2, introduce reference path, by bifocal path structure, design, effectively suppress the light-intensity variation impact that light source fluctuation and remaining Modulation and Amplitude Modulation (residual amplitude modulation, RAM) cause;
3, based on negative feedback closed loop structure, by SPR absorption peak is changed to quick lock in absorption peak position with variations in refractive index to be measured, to surveying the light-intensity variation of light, produce the good effect of subduing, the limit that is only limited to photodetector quantum noise on realization theory is measured sensitivity.
Accompanying drawing explanation
The closed-loop measuring principle schematic of the basic frequency modulation spectral principle of Fig. 1.
Fig. 2 is SPR Fibre Optical Sensor circuit theory schematic diagram.
Embodiment
As shown in Figure 2, this SPR Fibre Optical Sensor comprises SPR sensing head, interfere circuit, photoelectric switching circuit, pre-amplification circuit, A/D change-over circuit, demodulator circuit, digital integrating circuit, step incremental integration circuit, D/A change-over circuit, staircase waveform driving circuit, frequency modulation circuit, light source and EOM photoelectricity modulation circuit, one end of light source connects EOM photoelectricity modulation circuit, one end of EOM photoelectricity modulation circuit connects SPR sensing head, SPR sensing head, the other end of EOM photoelectricity modulation circuit connects interference circuit altogether, interfere circuit to connect photoelectric switching circuit, pre-amplification circuit, A/D change-over circuit, demodulator circuit and digital integrating circuit, digital integrating circuit connects step incremental integration circuit, D/A change-over circuit, staircase waveform driving circuit and frequency modulation circuit, frequency modulation circuit connects the other end of light source, the whole electric loop that forms SPR Fibre Optical Sensor.
Wherein, SPR optical fiber sensor head is selected the multimode silica fibre of numerical aperture 0.3, core district diameter 600 μ m, core district refractive index 1.465, utilize hydrofluorite to carry out covering processing, based on magnetron sputtering technique (JSD560-V vacuum magnetic-control sputtering instrument) plating thickness 50nm gold thin film, sensing unit length 15mm.
Wherein, arrowband probe source coordinates radio frequency tunable narrow-band filter plate to form by wideband light source, and light intensity is output as pulsed light, repetition frequency 5kHz; Wideband light source is selected the product HL/2000 of U.S. Ocean Optics company light source: output power 5W, wavelength coverage 360nm-near infrared, power consumption 1.2A, 12VDC, the adjustable focusing connector output of SMA905; Radio frequency tunable narrow-band filter plate is selected the product Semrock Versa Chrome of Photonics company series tunable narrow-band filter plate: continuous tuning wavelength coverage 0.1-30 nm, bandwidth 2nm, the positive and negative 0.1%-0.2% of the linearity, output intensity degree of stability 0.5%, TTL/CMOS level drives, rf frequency 20-350 MHz.
Wherein, the monochromatic narrowband modulation of filter plate output, selects MLP080-YDC to complete; Modulator is that Gooch & Housego company produces: tuning range 0-80MHz, modulating frequency stability is less than 0.01% Quartz Stabilized, inserts intensity loss and is less than 2.45 db, return loss-30 db, radio-frequency driven power consumption 1W, carrier wave light signal polarization state is random.
Wherein, monochromatic narrow-band frequency modulation light is divided into two bundle phase differential via a Y type three-dB coupler
, isocandela light, input respectively the optic fibre light path of two symmetries, wherein a light path comprises based on SPR effect transmission-type sensing head, another road is reference path; Detection optical fiber, reference optical fiber will be exported separately light via a Y type coupling mechanism again and " unite two into one ", after mutually interfering, act on photodetector, record the square wave photo-signal containing the frequency selectivity resonance absorption information based on SPR effect; According to frequency modulation spectral principle, photo-signal is after pre-amplification circuit, A/D change-over circuit and demodulator circuit signal condition are processed, and acquisition amplitude is proportional to the square wave photo-signal of surveying difference on the frequency between light fundamental frequency centre frequency and SPR effect resonance absorption peak center; This signal, through digital integration treatment circuit, D/A change-over circuit, acts on light source as negative feedback control signal, and light source center frequency is modulated, and makes it under close loop negative feedback control action gradually in SPR effect absorption peak centre frequency; When the two is consistent, photocurrent square wave amplitude is zero, and light source center Frequency Locking is in SPR effect absorption peak centre frequency; After factor causes refractive index to change arbitrarily, system repeats said process, by negative feedback, is again locked in new absorption peak centre frequency; Modulated square wave in locking process is corresponding to corresponding frequencies side-play amount.
Wherein, photodetector is selected the Japanese ZARLINK product C30921ES Si of company series photodetector assembly, and service band is 400-1100 nm, includes PIN pipe and pre-amplifying module, supports Transistor-Transistor Logic level output.
Wherein, A/D converter is selected 16 high-speed AD converters of ADS1100 type, and American TI Company is produced, and difference input, has continuous self-calibration function, conversion accuracy 0.0125%, operating voltage 2.7-5.5 V, maximum clock 30M.
Wherein, narrowband modulation needed number staircase waveform is produced by FPGA module, EP2C5Q208C8 in the product Cyclonell of chip selection altera corp series, and full copper SRAM technique, 110 pin PinPQFD sealings, include 4608 logical blocks, are equivalent to 260,000 gate circuits.
As shown in Figure 1, with
represent the index of modulation,
represent frequency modulating signal,
the monochromatic tunable optical centre frequency that expression is exported after optical filter,
represent total light intensity, narrow-band frequency modulation light has
,
,
,
This modulating light is divided into isocandela two-beam through 3dB photo-coupler, and one for surveying light, transfers to SPR optical fiber sensor head, and another is reference light; Survey light, through SPR optical fiber sensor head, generation is decided by the wavelength selectivity light intensity of SPR effect absorbs; Detection light after absorption and reference light act on photodetector (PD) and are converted to the radio frequency photocurrent that contains absorption information after interventional procedures; After low-frequency disturbance is eliminated in high-pass filtering (High Pass), with this locality, the former radiofrequency signal for narrow-band frequency modulation (RF Source) mixing (Mixer) after phase shift (Phase shifter), again through low-pass filtering (Low Pass, relevant detection) process, obtain a photocurrent containing absorption characteristic differential smoothing information; If
for surveying light and the peak-to-peak difference on the frequency of SPR resonance absorption, when detection light path without absorbing medium or
time, symmetrical absorption peak makes differential smoothing be output as zero; When
time, will export with
the photocurrent being directly proportional, replaces in Spectrographic measurement
determine absorption peak;
,
be respectively SPR optical fiber sensor head at single order sideband place, absorption peak place single order Differential Spectrum, due to
, with
replace
make to measure sensitivity or resolution is significantly increased; Will be by
definite photocurrent is through amplify processing, and using as negative feedback control signal, regulation and control filter plate centre frequency, meets optical path
, realize and survey the locking of light center frequency to the SPR optical fiber sensor head center absorption frequency as absorbing medium; Like this, by suitable demarcation, the regulation and control amount in negative feedback process reflects testing medium refractive index and variation thereof; When modulating frequency and absorption peak full width at half maximum are during with the order of magnitude, above-mentioned negative feedback closed loop structure modulating light spectrometry can effectively realize.
Claims (5)
1. the SPR Fibre Optical Sensor based on frequency modulation spectral principle, it is characterized in that: this SPR Fibre Optical Sensor comprises SPR sensing head, interfere circuit, photoelectric switching circuit, pre-amplification circuit, A/D change-over circuit, demodulator circuit, digital integrating circuit, step incremental integration circuit, D/A change-over circuit, staircase waveform driving circuit, frequency modulation circuit, light source and EOM photoelectricity modulation circuit, one end of light source connects EOM photoelectricity modulation circuit, one end of EOM photoelectricity modulation circuit connects SPR sensing head, SPR sensing head, the other end of EOM photoelectricity modulation circuit connects interference circuit altogether, interfere circuit to connect photoelectric switching circuit, pre-amplification circuit, A/D change-over circuit, demodulator circuit and digital integrating circuit, digital integrating circuit connects step incremental integration circuit, D/A change-over circuit, staircase waveform driving circuit and frequency modulation circuit, frequency modulation circuit connects the other end of light source, the whole electric loop that forms SPR Fibre Optical Sensor.
2. the SPR Fibre Optical Sensor based on frequency modulation spectral principle according to claim 1, it is characterized in that: SPR optical fiber sensor head is selected the multimode silica fibre of numerical aperture 0.3, core district diameter 600 μ m, core district refractive index 1.465, utilize hydrofluorite to carry out covering processing, based on magnetron sputtering technique JSD560-V vacuum magnetic-control sputtering instrument plating thickness 50nm gold thin film, sensing unit length 15mm.
3. the SPR Fibre Optical Sensor based on frequency modulation spectral principle according to claim 1, is characterized in that: arrowband probe source coordinates radio frequency tunable narrow-band filter plate to form by wideband light source, and light intensity is output as pulsed light, repetition frequency 5kHz; Wideband light source is selected the product HL/2000 of U.S. Ocean Optics company light source: output power 5W, wavelength coverage 360nm-near infrared, power consumption 1.2A, 12VDC, the adjustable focusing connector output of SMA905; Radio frequency tunable narrow-band filter plate is selected the product Semrock Versa Chrome of Photonics company series tunable narrow-band filter plate: continuous tuning wavelength coverage 0.1-30 nm, bandwidth 2nm, the positive and negative 0.1%-0.2% of the linearity, output intensity degree of stability 0.5%, TTL/CMOS level drives, rf frequency 20-350 MHz.
4. the SPR Fibre Optical Sensor based on frequency modulation spectral principle according to claim 3, is characterized in that: the monochromatic narrowband modulation of filter plate output, and select MLP080-YDC to complete; Modulator is that Gooch & Housego company produces: tuning range 0-80MHz, modulating frequency stability is less than 0.01% Quartz Stabilized, inserts intensity loss and is less than 2.45 db, return loss-30 db, radio-frequency driven power consumption 1W, carrier wave light signal polarization state is random.
5. the SPR Fibre Optical Sensor based on frequency modulation spectral principle according to claim 1, it is characterized in that: wherein, photodetector is selected the Japanese ZARLINK product C30921ES Si of company series photodetector assembly, service band is 400-1100 nm, include PIN pipe and pre-amplifying module, support Transistor-Transistor Logic level output.
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Cited By (4)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN105548078A (en) * | 2016-01-13 | 2016-05-04 | 中国计量学院 | Hydrogen sensing device based on side-polished graded-index optical fiber |
| CN105606565A (en) * | 2016-02-25 | 2016-05-25 | 中国科学院合肥物质科学研究院 | Wavelength modulation absorption spectrum measurement device |
| CN112290905A (en) * | 2020-11-10 | 2021-01-29 | 四川大学 | Technology for frequency-up regulation of quartz resonator based on magnetron sputtering |
| CN114460674A (en) * | 2022-01-25 | 2022-05-10 | 南京邮电大学 | Addressable surface plasmon closed-loop control modulation system and method |
-
2013
- 2013-09-23 CN CN201320584004.XU patent/CN203534963U/en not_active Expired - Fee Related
Cited By (7)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN105548078A (en) * | 2016-01-13 | 2016-05-04 | 中国计量学院 | Hydrogen sensing device based on side-polished graded-index optical fiber |
| CN105606565A (en) * | 2016-02-25 | 2016-05-25 | 中国科学院合肥物质科学研究院 | Wavelength modulation absorption spectrum measurement device |
| CN105606565B (en) * | 2016-02-25 | 2018-07-13 | 中国科学院合肥物质科学研究院 | A kind of wavelength modulated optical absorption spectra measuring device |
| CN112290905A (en) * | 2020-11-10 | 2021-01-29 | 四川大学 | Technology for frequency-up regulation of quartz resonator based on magnetron sputtering |
| CN112290905B (en) * | 2020-11-10 | 2024-03-22 | 四川大学 | Method for adjusting up-conversion of quartz resonator based on magnetron sputtering |
| CN114460674A (en) * | 2022-01-25 | 2022-05-10 | 南京邮电大学 | Addressable surface plasmon closed-loop control modulation system and method |
| CN114460674B (en) * | 2022-01-25 | 2023-11-14 | 南京邮电大学 | Addressable surface plasmon closed-loop control modulation system and method |
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