CN101592526A - A kind of measuring method of average light wavelength and device - Google Patents

Abstract

To solve in the existing technology of measuring mean wavelength, there are not energy measurement wide range light wavelength in a kind of measuring method of average light wavelength and device, measuring accuracy is lower, measuring error is big and the difficult problem of transferring of stable operating point.The light signal that the present invention includes input obtains two-way light by phase modulation (PM), and makes the two-way light through the fiber optic loop transmission produce interference; The light signal of receive interfering also converts described light signal to electric signal, by demodulation obtains the mean wavelength of the light signal of described input to electric signal.The present invention is converted into electric signal by the interference light signal that will receive, and the mean wavelength of the light signal that obtains importing by demodulation to electric signal, have that measuring accuracy is higher, measuring error is less and the characteristics of easy measurement, the mean wavelength that can be used for measuring optical fiber sensing and optical-fibre communications field wide range light signal, also can be used to measure the mean wavelength of narrow spectrum light signal, be specially adapted to the measurement of high precision wide range average light wavelength.

Description

A kind of measuring method of average light wavelength and device

Technical field

The present invention relates to a kind of measuring method and device of average light wavelength, belong to Fibre Optical Sensor and optical-fibre communications field.

Background technology

Prior art adopts the wavemeter of measuring mean wavelength mainly based on principle of interference at present, mainly contains Fizeau interference type (Fizeau), Fabry-Bo Luo type (Fabry-Perot) and Michaelson (Mechelson) by the measuring principle branch.

(1) Fizeau interference type (Fizeau)

The Fizeau wavemeter can be measured the output wavelength of pulse or continuous wave laser, comprise the light field of the not coated surface of two formation interferometers, an input light field and two difference coated surface reflections never, this two bundles reflected light forms the sinusoidal interference striped on ccd detector.CCD exports simulating signal, converts digital signal to by sampling amplifier and analog to digital converter again, reads in the computing machine and calculates, and determines the wavelength value of light source at last.Not needing to be characterized in built-in reference light source, measuring accuracy is low, must put into constant temperature oven.

(2) Fabry-Bo Luo type (Fabry-Perot)

Fabry-Perot interference type wavemeter is that the phenomenon that produces multiple-beam interference when utilizing light beam to pass through two platings with the certain glass plate of high reflectance spacing is measured the testing laser wavelength.This wavemeter can be used to measure the output wavelength of pulse or continuous wave laser, and system can adopt the etalon of a plurality of different-thickness.The F-P wavemeter is compared by the interference fringe that known reference laser of wavelength and testing laser produce, and measures the wavelength of testing laser.

(3) Michaelson (Mechelson)

The Michelson wavemeter is fit to measure the continuous laser wavelength.The measuring accuracy of Michelson wavemeter can reach 1ppm and reach as high as 0.1ppm and be higher than other two kinds of wavemeters, when moving reflector during along the axis translation, write down two groups of different interference fringes of reference laser and measured laser simultaneously, according to the product and the air refraction of the vacuum wavelength value of two groups of fringe number ratios and reference laser, can directly try to achieve the measured laser wavelength value.

More than three kinds of wavemeters energy measurement wide range light wavelength not, can only measure narrow spectrum light (laser), because these wavemeters all are based on principle of interference, and the coherence of wide range light is relatively poor, cause the striped after the interference of light frequently of two beamwidths unintelligible, the wavemeter that adopts the conventional interference principle that interference fringe is analyzed is difficult to measure exactly the wide range light wavelength.Also has a kind of wavemeter in addition based on Mach-Ze De type (March-Zhnder), receive the interference light of waveguide modulator output by photodetector, and change the light signal of interference light into electric signal, the mean wavelength that calculates bright dipping by observation circuit again, the wavemeter of Mach-Ze De type (March-Zhnder) need form two fiber arms, and the stability of two fiber arms becomes and influences the principal element of system's detection accuracy stable operating point and be difficult to adjust, theoretical precision is limited, is difficult to improve accuracy of detection.And generally adopt spectrometer for the measurement of wide range light at present, spectrometer is to analyze the instrument that optical signal spectrum distributes, it has utilized the interference light-dividing device that light signal is carried out beam split, measures every bundle light wavelength respectively, draws the mean wavelength of light signal then by the weighted integral computing.Though spectrometer can be measured the wide range light wavelength, according to the design feature of spectrometer, measuring wavelength is the simplest application of spectrometer, and its precision also is difficult to satisfy the requirement of high-precision optical fiber gyro optical wavelength measurement precision.

Therefore, in the existing technology of measuring mean wavelength, have not energy measurement wide range light wavelength, measuring accuracy is lower, measuring error is big and the difficult problem of transferring of stable operating point.Wherein the wavemeter of Mach-Ze De type (March-Zhnder) need form two fiber arms, and the stability of two fiber arms becomes the principal element that influences system's detection accuracy.

Summary of the invention

The invention provides a kind of measuring method and device of average light wavelength, to solve in the existing technology of measuring mean wavelength, have not energy measurement wide range light wavelength, measuring accuracy is lower, measuring error is big and the difficult problem of transferring of stable operating point.

A kind of measuring method of average light wavelength comprises:

The light signal of input is obtained two-way light by phase modulation (PM), and make two-way light produce interference through the fiber optic loop transmission;

The light signal of receive interfering also converts described light signal to electric signal, by demodulation obtains the mean wavelength of the light signal of described input to electric signal.

A kind of measurement mechanism of average light wavelength comprises:

The optical modulation unit, the light signal that is used for importing carries out phase modulation (PM) and obtains two-way light, and makes the two-way light through the fiber optic loop transmission produce interference;

The photodetection unit is used to receive the light signal of interference and converts described light signal to electric signal, by demodulation obtains the mean wavelength of the light signal of described input to electric signal.

The present invention is converted into electric signal by the interference light signal that will receive, and the mean wavelength of the light signal that obtains importing by demodulation to electric signal, have that measuring accuracy is higher, measuring error is less and the characteristics of easy measurement, the mean wavelength that can be used for measuring optical fiber sensing and optical-fibre communications field wide range light signal, also can be used to measure the mean wavelength of narrow spectrum light signal, be specially adapted to the measurement of high precision wide range optical wavelength.Use this kind wavemeter that the measuring accuracy of wide range average light wavelength is better than 1ppm.Have good optics reciprocity, can significantly reduce the error of introducing by polarization, backscattering back-reflection, improve measuring accuracy.

Description of drawings

Fig. 1 is the schematic flow sheet of the measuring method of a kind of average light wavelength of providing of the specific embodiment of the present invention;

Fig. 2 is the Sagnac interferometer synoptic diagram that the specific embodiment of the present invention provides;

Fig. 3 is the phase modulated signal synoptic diagram that the specific embodiment of the present invention provides;

Fig. 4 is the modulating and demodulating signal synoptic diagram that the specific embodiment of the present invention provides;

Fig. 5 is the signal deteching circuit schematic diagram that the specific embodiment of the present invention provides;

Fig. 6 is the structural representation of the measurement mechanism of a kind of average light wavelength of providing of the specific embodiment of the present invention.

Embodiment

In the technical scheme of the measuring method of a kind of average light wavelength that the specific embodiment of the present invention provides, at first the light signal with input obtains two-way light by phase modulation (PM), and two-way light through the fiber optic loop transmission is produced interfere; Receive the light signal of interference then and convert light signal to electric signal, by the electric signal demodulation being obtained the mean wavelength of the light signal of input.

Further, transmission comprises two-way light respectively by symmetrical coiling and two opposite fiber optic loop transmission of incident direction through fiber optic loop.The mean wavelength of the light signal of input is calculated according to following formula and is obtained:

$\mathrm{\φ}=\frac{\mathrm{\π}}{\mathrm{\λ}}\·\frac{l}{d}\·\mathrm{\ΓU}{n}_e^3{\mathrm{\γ}}_{33};$

Wherein φ is the light signal phase differential that positive and negative two directions are propagated in Y waveguide, and l is the length of waveguide, and d is the thickness of waveguide, and λ is an average wavelength of light source, and U is a modulation voltage, and Γ is the overlap factor of electric field and light field, n _eBe extraordinary ray refractive index, γ ₃₃Be specific inductive capacity.

The measuring method of a kind of average light wavelength that provides for clearer explanation the specific embodiment of the present invention now is elaborated to this method in conjunction with Figure of description, as shown in Figure 1, specifically can comprise:

Step 11 obtains two-way light with the light signal of importing by phase modulation (PM), and makes the two-way light through the fiber optic loop transmission produce interference.

The method that present embodiment provides is based on the Sagnac interferometer, as shown in Figure 2.At first, the light signal that light source sends enters Y waveguide optical modulation unit through coupling mechanism, obtain two-beam through Y waveguide optical modulation cells modulate then, again two-beam is transmitted by symmetrical coiling and two opposite fiber optic loop of incident direction respectively, produce interference behind the two-way light process Y waveguide optical modulator through the fiber optic loop transmission.

Step 12 receives the light signal of interference and converts light signal to electric signal, by the electric signal demodulation being obtained the mean wavelength of the light signal of input.

For the light signal that does not add modulation, interfering output is the cosine function of Pockels phase shift, if it is carried out direct demodulation, need carry out the arc cosine computing, and operand will be very big, and sensitivity is not high, and measuring error is big.In order to improve accuracy of detection, what expect easily is that cosine signal is changed into sinusoidal signal, because sinusoidal signal sensitivity when small-signal, the rate of change maximum, and at measured φ _PCan characterize out during positive and negative variation.To be converted into sinusoidal response to cosine response, need between the two-beam that interferes, introduce one ± pi/2 or ± phase shift of π 3/2, can realize by on Y waveguide optical modulation unit, adding suitable voltage like this.The modulation phase signal that is added on the Y waveguide by voltage signal is:

${\mathrm{\φ}}_m\left(t\right)=\left\{\begin{array}{cc}0& 0\≤t\≤\mathrm{kT}/4\\ \mathrm{\π}/2& \mathrm{kT}/4\≤t\≤\mathrm{kT}/2\\ 2\mathrm{\π}& \mathrm{kT}/2\≤t\≤3\mathrm{kT}/4\\ \mathrm{\π}/2& 3\mathrm{kT}/4\≤t\≤\mathrm{kT}\end{array}\right.,k=\mathrm{1,2,3}...$

Wherein, shown in Fig. 4 a, T is a modulation signal cycle, and fetch cycle T=4 τ, τ are the transit time of light in optical fiber.Shown in Fig. 4 b, the light after the modulation will delay time T after transmitting in optical fiber.Shown in Fig. 4 c, after adding modulation signal on the Y waveguide, the phase differential of the light of positive and negative two directions propagation weak point is in the Y waveguide:

$\mathrm{\Δ}{\mathrm{\φ}}_m\left(t\right)={\mathrm{\φ}}_m\left(t\right)-{\mathrm{\φ}}_m(t-\mathrm{\τ})=\left\{\begin{array}{cc}-\mathrm{\π}/2& 0\≤t\≤\mathrm{kT}/4\\ -3\mathrm{\π}/2& \mathrm{kT}/4\≤t\≤\mathrm{kT}/2\\ \mathrm{\π}3/2& \mathrm{kT}/2\≤t\≤3\mathrm{kT}/4\\ \mathrm{\π}/2& 3\mathrm{kT}/4\≤t\≤\mathrm{kT}\end{array}\right.,k=\mathrm{1,2,3}...$

Two-beam interferes back output at the Y waveguide place, the signal that is detected by photodetector is:

P(t)＝P ₀[1+cos(Δφ _R+Δφ _m(t))]

Δ φ wherein _RFor fiber optic loop is rotated the Sagnac phase differential that causes, when light path is static, Δ φ _R=0 (can ignore the influence of factors such as earth rotation).At this moment:

P(t)＝P ₀[1+cos(Δφ _m(t))]

(1) when the mean wavelength of light source does not change, P (t)=P ₀

(2) when the elongated Δ λ of the mean wavelength of light source, Δ φ reduces φ _r, then the power that detects of detector is:

$P\left(t\right)=P_0[1+\cos (\mathrm{\Δ}{\mathrm{\φ}}_m\left(t\right)-{\mathrm{\φ}}_r)]=\left\{\begin{array}{cc}{P}_0-P_0\sin {\mathrm{\φ}}_r& 0\≤t\≤\mathrm{kT}/4\\ P_0+P_0\sin {\mathrm{\φ}}_r& \mathrm{kT}/4\≤t\≤\mathrm{kT}/2\\ P_0+P_0\sin {\mathrm{\φ}}_r& \mathrm{kT}/2\≤t\≤3\mathrm{kT}/4\\ P_0-P_0\sin {\mathrm{\φ}}_r& 3\mathrm{kT}/4\≤t\≤\mathrm{kT}\end{array}\right.,\mathrm{\κ}=\mathrm{1,2,3}...$

(3) when the mean wavelength of light source shortened Δ λ, Δ φ increased φ _r, then the power that detects of detector is:

$P\left(t\right)=P_0[1+\cos (\mathrm{\Δ}{\mathrm{\φ}}_m\left(t\right)-{\mathrm{\φ}}_r)]=\left\{\begin{array}{cc}{P}_0+P_0\sin {\mathrm{\φ}}_r& 0\≤t\≤\mathrm{kT}/4\\ P_0-P_0\sin {\mathrm{\φ}}_r& \mathrm{kT}/4\≤t\≤\mathrm{kT}/2\\ P_0-P_0\sin {\mathrm{\φ}}_r& \mathrm{kT}/2\≤t\≤3\mathrm{kT}/4\\ P_0+P_0\sin {\mathrm{\φ}}_r& 3\mathrm{kT}/4\≤t\≤\mathrm{kT}\end{array}\right.,\mathrm{\κ}=\mathrm{1,2,3}...$

Just can detect phase signal by the output voltage signal that detects photodetector

As shown in Figure 5, the signal that detects carried out demodulation after, according to the Pockels effect, have following formula to set up:

$\mathrm{\φ}=\frac{\mathrm{\π}}{\mathrm{\λ}}\·\frac{l}{d}\·\mathrm{\ΓU}{n}_e^3{\mathrm{\γ}}_{33}$

Wherein φ is the light signal phase differential that positive and negative two directions are propagated in Y waveguide, and l is the length of waveguide, and d is the thickness of waveguide, and λ is an average wavelength of light source, and U is a modulation voltage, and Γ is the overlap factor of electric field and light field, n _eBe extraordinary ray refractive index, γ ₃₃Be specific inductive capacity.Other is constant to remove voltage U and wavelength X in this formula, can be constant K with its equivalence, obtains:

$K=\frac{\mathrm{\πl}}{d}\·\mathrm{\Γ}{n}_e^3{\mathrm{\γ}}_{33}$

Following formula can be reduced to:

$\mathrm{\φ}=K\·\frac{U}{\mathrm{\λ}}$

When other factors is constant, when fluctuation takes place optical source wavelength, can produce the Pockels phase shift, this phase shift signalling converts light intensity signal to through interfering, and converts electric signal to and be detected, thereby can calculate the mean wavelength of light source.

The specific embodiment of the present invention can be used for the mean wavelength of measuring optical fiber sensing and optical-fibre communications field wide range light signal, also can be used to measure the mean wavelength of narrow spectrum light signal, particularly to the measurement of high precision wide range optical wavelength.For research average wavelength of light source in broad spectrum stability, development mean wavelength high stable light source, and the mean wavelength of light in the optical fibre gyro measured control, to the optic fiber gyroscope graduation factor that causes by mean wavelength change compensate all significant, thereby solve the constant multiplier stability problem of high-precision optical fiber gyro.Owing to adopt the Sagnac interferometer of forming by integrated optical modulator of Y branch and fiber optic loop to carry out optical wavelength measurement, the optical wavelength that records promptly is the light wavelength lambda in the optic fiber gyroscope graduation factor, the measuring error of having avoided other instruments that optic fiber gyroscope graduation factor medium wavelength lambda definition difference is brought; Select the Sagnac interferometer that constitutes by Y waveguide and fiber optic loop for use, have good optics reciprocity, can significantly reduce the error of introducing by polarization, backscattering back-reflection, improve measuring accuracy; Optical fiber winding adopts symmetrical coiling and the opposite formation of incident direction, can offset the error of being introduced by the Faradic electricity magnetic effect, improves measuring accuracy.

The specific embodiment of the present invention also provides a kind of measurement mechanism of average light wavelength, in embodiments of the present invention, the device of implementing measuring method can comprise light path system and Circuits System, light path system can comprise light source, coupling mechanism, Y waveguide optical modulation unit and fiber optic loop, the light signal that light source sends enters Y waveguide optical modulation unit through coupling mechanism, obtain two-beam through Y waveguide optical modulation cells modulate then, again two-beam is transmitted by symmetrical coiling and two opposite fiber optic loop of incident direction respectively, produce interference behind the two-way light process Y waveguide optical modulator through the fiber optic loop transmission; Circuits System can comprise pre-amplification circuit, A/D converter, microprocessor, D/A converter, postfilter and power circuit composition as shown in Figure 5.Pre-amplification circuit is to analog voltage signal U _ACarry out low noise amplification and will amplify by A/D converter after analog voltage signal convert digital voltage signal U to _D, microprocessor is to digital voltage signal U _DCarry out exporting a digital voltage signal U after the calculation process _D` converts analog voltage signal U to by A/D converter again <sub>A</sub>`, analog voltage signal U _ABe added on the Y waveguide integrated optical modulator behind the ` process postfilter smothing filtering, form closed-loop system.Effect in device describes present embodiment below in conjunction with Figure of description and each device, as shown in Figure 6, specifically can comprise:

Optical modulation unit 61, the light signal that is used for importing carries out phase modulation (PM) and obtains two-way light, and makes the two-way light through the fiber optic loop transmission produce interference;

Photodetection unit 62 is used to receive the light signal of interference and converts light signal to electric signal, by the electric signal demodulation being obtained the mean wavelength of the light signal of input.

At first the light signal of importing is carried out phase modulation (PM) and obtain two-way light, and make two-way light produce interference through the fiber optic loop transmission by optical modulation unit 61; Receive the light signal of interference and convert light signal to electric signal by photodetection unit 62 then, by the electric signal demodulation being obtained the mean wavelength of the light signal of input.

Further, transmission comprises two-way light respectively by symmetrical coiling and two opposite fiber optic loop transmission of incident direction through fiber optic loop.The mean wavelength of the light signal of input is calculated according to following formula and is obtained:

$\mathrm{\&phi;}=\frac{\mathrm{\&pi;}}{\mathrm{\&lambda;}}\&CenterDot;\frac{l}{d}\&CenterDot;\mathrm{\&Gamma;U}{n}_e^3{\mathrm{\&gamma;}}_{33};$

Wherein φ is the light signal phase differential that positive and negative two directions are propagated in Y waveguide, and l is the length of waveguide, and d is the thickness of waveguide, and λ is an average wavelength of light source, and U is a modulation voltage, and Γ is the overlap factor of electric field and light field, n _eBe extraordinary ray refractive index, γ ₃₃Be specific inductive capacity.

The specific implementation of the processing capacity of each unit that comprises in the said system is described in method embodiment before, no longer is repeated in this description at this.

The above; only for the preferable embodiment of the present invention, but protection scope of the present invention is not limited thereto, and anyly is familiar with those skilled in the art in the technical scope that the present invention discloses; the variation that can expect easily or replacement all should be encompassed within protection scope of the present invention.Therefore, protection scope of the present invention should be as the criterion with the protection domain of claims.

Claims (6)

1, a kind of measuring method of average light wavelength is characterized in that, comprising:

The light signal of input is obtained two-way light by phase modulation (PM), and make two-way light produce interference through the fiber optic loop transmission;

The light signal of receive interfering also converts described light signal to electric signal, by demodulation obtains the mean wavelength of the light signal of described input to electric signal.

2, method according to claim 1 is characterized in that, described transmission comprises through fiber optic loop: described two-way light is transmitted by symmetrical coiling and two opposite fiber optic loop of incident direction respectively.

3, method according to claim 1 is characterized in that, the mean wavelength of the light signal of described input is calculated according to following formula and obtained:

$\mathrm{\&phi;}=\frac{\mathrm{\&pi;}}{\mathrm{\&lambda;}}\&CenterDot;\frac{l}{d}\&CenterDot;\mathrm{\&Gamma;U}{n}_e^3{\mathrm{\&gamma;}}_{33};$

Wherein φ is the light signal phase differential that positive and negative two directions are propagated in Y waveguide, and l is the length of waveguide, and d is the thickness of waveguide, and λ is an average wavelength of light source, and U is a modulation voltage, and Γ is the overlap factor of electric field and light field, n _eBe extraordinary ray refractive index, γ ₃₃Be specific inductive capacity.

4, a kind of measurement mechanism of average light wavelength is characterized in that, comprising:

The optical modulation unit, the light signal that is used for importing carries out phase modulation (PM) and obtains two-way light, and makes the two-way light through the fiber optic loop transmission produce interference;

The photodetection unit is used to receive the light signal of interference and converts described light signal to electric signal, by demodulation obtains the mean wavelength of the light signal of described input to electric signal.

5, device according to claim 4 is characterized in that, described transmission comprises through fiber optic loop: described two-way light is transmitted by symmetrical coiling and two opposite fiber optic loop of incident direction respectively.

6, device according to claim 4 is characterized in that, the mean wavelength of the light signal of described input is calculated according to following formula and obtained:

$\mathrm{\&phi;}=\frac{\mathrm{\&pi;}}{\mathrm{\&lambda;}}\&CenterDot;\frac{l}{d}\&CenterDot;\mathrm{\&Gamma;U}{n}_e^3{\mathrm{\&gamma;}}_{33};$

Wherein φ is the light signal phase differential that positive and negative two directions are propagated in Y waveguide, and l is the length of waveguide, and d is the thickness of waveguide, and λ is an average wavelength of light source, and U is a modulation voltage, and Γ is the overlap factor of electric field and light field, n _eBe extraordinary ray refractive index, γ ₃₃Be specific inductive capacity.

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