CN204119235U - The tunable Instantaneous Frequency Measurement system of a kind of high accuracy - Google Patents

Abstract

The tunable Instantaneous Frequency Measurement system of a kind of high accuracy, relate to Microwave photonics field, continuous-wave laser (1) first connects the first Polarization Controller (2), first Polarization Controller (2) connects the light input end of light polarization modulator (3) subsequently, radio-frequency signal source (4) connects the rf inputs (31) of light polarization modulator (3), bias voltage source (5) connects the bias input end (32) of light polarization modulator (3), the output of light polarization modulator (3) connects the second Polarization Controller (6), second Polarization Controller (6) connects polarization beam apparatus (7), first of polarization beam apparatus (7), second output (71, 72) through first, second monomode fiber (8, 9) first is entered respectively, second photodetector (10, 11), the signal that detection obtains outputs to first of electric treatment module (12) respectively, second input (121, 122), thus obtain amplitude comparison function.

Description

The tunable Instantaneous Frequency Measurement system of a kind of high accuracy

Technical field

The utility model relates to Microwave photonics field, specifically the tunable Instantaneous Frequency Measurement system of a kind of high accuracy.

Background technology

The transient microwave frequency introducing Microwave photonics measures (IFM, instantaneous frequency measurement) system compares conventional electronics method and has its unique advantage: 1) system is less the measuring range tape tolerance, can realize the analysis and resolution of miniature ultra wide band microwave signal; 2) there is electromagnetism interference characteristic, the crypticity of measurement can be improved.Therefore, a large study hotspot of recent domestic is become based on the application study of Microwave photonics.Need to consider following factor when a design Instantaneous Frequency Measurement system: 1. measuring range is large; 2. certainty of measurement is high; 3. stability is high.The IFM system based on Microwave photonics proposed at present can be roughly divided into frequency-space mapping by operation principle, frequency-time maps and frequency-amplitude maps three classes.Wherein frequency-amplitude maps is the most effective a kind of implementation in research at present.IFM system (" the Instantaneous Microwave Frequency Measurement Using a Photonic Microwave Filter Pair forming microwave photon filter based on light polarization modulator and polarization-maintaining fiber that the people such as such as Canadian scholar S.Pan propose; " IEEE Photonics Technology Letters, vol.22, pp.1437-1439,2010), but the measuring range of the program is relatively fixing and certainty of measurement is uncontrollable.The people such as Canada scholar X.Zou propose a kind of measuring range and the adjustable implementation of precision (" the An Optical Approach to Microwave Frequency Measurement With Adjustable Measurement Range and Resolution that utilize dual wavelength modulation and light filtering; " IEEE Photonic Technology Letters, vol.20, pp.1989-1991,2008), but there is the too little problem of measuring range.Reconfigurable I FM system (" the Reconfigurable instantaneous frequency measurement system based on dual-parallel Mach-Zehnder modulator based on two parallel Mach zehnder modulators and a Dual Drive Mach zehnder modulators that the people such as Chinese Academy of Sciences scholar W.Li proposes; " IEEE Photonics Journal, vol.4, pp.427-436,2012) although comparatively wide-measuring range and degree of precision can be obtained, the bias voltage drifting problem solving modulator is needed.The people such as the H.Zhang of Nanjing Aero-Space University then propose a kind of scheme one (" Instantaneous frequency measurement with adjustable measurement range and resolution based on polarisation modulator utilizing light polarization modulation and polarization-sensitive effects; " Electronics Letters, vol.49, pp.277-279,2013), but the program is more complicated, stability reduces, and needs to carry out dynamic equilibrium to power.The people such as the J.L of this research institute are on this Research foundation, propose and a kind of there is IFM scheme two (" the Performance analysis on an instantaneous microwave frequency measurement with tunable range and resolution based on a single laser source of single light source without filter structure; " Optics & Laser Technology, vol.63, pp.54-61,2014.), simplify the structure and do not need to consider the dynamic balance issue of luminous power.But what this system adopted is one section of short dispersion compensating fiber, otherwise can produce polarization interference etc. at inside of optical fibre, impacts measurement result.In practical application, often can face the longer situation of transmission range, and monomode fiber is more common.For this reason, it is very necessary for designing a kind of high accuracy tunable Instantaneous Frequency Measurement system

Utility model content

The utility model proposes the tunable Instantaneous Frequency Measurement system of the better simply high accuracy of a kind of structure.Scheme adopts single light source and rearmounted monomode fiber, its structure and scheme one, two are distinguished to some extent, native system adopts bias modulator as Primary Component, utilize Polarization Controller, bias voltage source and polarization beam apparatus to control polarisation of light state, by controlling the dispersion parameters of monomode fiber, and incident polarization angle α is regulated, finally obtain power output than tunable ACF function curve, and the difficulty of IFM system realization can be reduced to greatest extent: 1) adopt single light source can eliminate the impact of luminous power shake; 2) structure eliminating filter simplifies more, also contributes to the impact eliminating light source center wave length shift; 3) in the tuning process of measuring range and precision, do not need the dynamic balance issue considering luminous power, regulating effect is better.This Instantaneous Frequency Measurement system can be measured the microwave signal frequency of frequency range 2GHz ~ 18.2GHz, has very high commercial value.

The technical solution of the utility model:

The tunable Instantaneous Frequency Measurement system of a kind of high accuracy, it is characterized in that: this measuring system comprises, continuous-wave laser, the first Polarization Controller, light polarization modulator, radio-frequency signal source, bias voltage source, the second Polarization Controller, polarization beam apparatus, the first monomode fiber, the second monomode fiber, the first photodetector, the second photodetector, electric treatment module; Concrete connected mode is:

The light input end of light output termination first Polarization Controller of continuous-wave laser, the light input end of the light output termination light polarization modulator of the first Polarization Controller, the rf inputs of the output termination light polarization modulator of radio-frequency signal source, the bias input end of the output termination light polarization modulator of bias voltage source, the light input end of light output termination second Polarization Controller of light polarization modulator, the input of the light output termination polarization beam apparatus of the second Polarization Controller, first of polarization beam apparatus exports the input of termination first monomode fiber, the input of output termination first photodetector of the first monomode fiber, the first input end of the output termination electric treatment module of the first photodetector, second of polarization beam apparatus exports the input of termination second monomode fiber, the input of output termination second photodetector of the second monomode fiber, second input of the output termination electric treatment module of the second photodetector.

The output angle [alpha] of the first Polarization Controller (2), α scope is 5 °≤α≤40 °;

Light polarization modulator (3) has complementary phases modulation depth, and be respectively+β and-β, wherein β value will meet small signal modulation, 0.1≤β≤0.3;

The half-wave voltage V of light polarization modulator (3) _π, half-wave voltage scope is 2V≤V _π≤ 6V

Regulate the output voltage V of bias voltage source (5) _bias, make V _bias1=0.5V _π;

Regulate radio-frequency signal source (4) output signal frequency f, frequency range is 2GHz≤f≤18.2GHz;

Regulate the output phase place σ of the second Polarization Controller (6), σ=45 °;

Set the dispersion values D of the first monomode fiber (8) and the second monomode fiber (9) _w=16.75ps/kmnm, length L=10km;

Specific works principle of the present utility model is as follows:

Under small signal modulation condition, can obtain light field expression formula is

$\left[\begin{array}{c}{E}_x\\ E_y\end{array}\right]=E_0{e}^{{\mathrm{jw}}_{c}t}\left[\begin{array}{c}\underset{k=-1}{\overset{1}{\mathrm{\Σ}}}\cos \mathrm{\α}{J}_k\left(\mathrm{\β}\right)\exp (\mathrm{jk\Ωt}+j{\mathrm{\ψ}}_k+\mathrm{j\φ})\\ \underset{k=-1}{\overset{1}{\mathrm{\Σ}}}\sin \mathrm{\α}{(-1)}^k{J}_k\left(\mathrm{\β}\right)\exp (\mathrm{jk\Ωt}+j{\mathrm{\ψ}}_k)\end{array}\right]---\left(1\right)$

Wherein E _oand ω _crepresent amplitude and the angular frequency of light carrier respectively, J _kfor the k rank coefficient of Bessel function, β=π V _rF/ √ 2V _πthe index of modulation (wherein V _πrepresent the half-wave voltage of PolM, Ω=2 π f _rFrepresent the angular frequency of unknown microwave signal). ψ _k=-k ²λ D _wl Ω ²/ 4 π c are that (wherein λ is wavelength, D in phase shift caused by dispersion _wbe dispersion parameters, L is fiber lengths, and c is vacuum light speed). φ=π V _bias/ V _πthen DC offset voltage V _biascaused angle of phase displacement.

From monomode fiber, light signal is out divided into two-way and enters into photo-detector and carry out subsequent treatment, in this patent, and the output voltage V of bias voltage source _bias1=0.5V _π, i.e. φ=pi/2, then two ways of optical signals can be expressed as:

$E_1\left(t\right)=\frac{\sqrt{2}}{2}{E}_0{e}^{{\mathrm{jw}}_{c}t}\underset{k=-1}{\overset{1}{\mathrm{\Σ}}}\left[(j\cos \mathrm{\α}+\sin \mathrm{\α}{(-1)}^k\right]J_k\left(\mathrm{\β}\right)\exp (\mathrm{jk\Ωt}+j{\mathrm{\ψ}}_k)---\left(2\right)$

$E_2\left(t\right)=\frac{\sqrt{2}}{2}{E}_0{e}^{{\mathrm{jw}}_{c}t}\underset{k=-1}{\overset{1}{\mathrm{\Σ}}}\left[(j\cos \mathrm{\α}-\sin \mathrm{\α}{(-1)}^k\right]J_k\left(\mathrm{\β}\right)\exp (\mathrm{jk\Ωt}+j{\mathrm{\ψ}}_k)$

$i_1\left(t\right)\∝\left[{\mathrm{\η}}_1{\left|E_0\right|}^2{J}_1\left(\mathrm{\β}\right)J_0\left(\mathrm{\β}\right)\sin ({\mathrm{\ψ}}_1+2\mathrm{\α})\right]\sin \mathrm{\Ωt}---\left(3\right)$

$i_2\left(t\right)\∝\left[{\mathrm{\η}}_2{\left|E_0\right|}^2{J}_1\left(\mathrm{\β}\right)J_0\left(\mathrm{\β}\right)\sin ({\mathrm{\ψ}}_1-2\mathrm{\α})\right]\sin \mathrm{\Ωt}$

Wherein ψ ₁=- ²λ D _wl Ω ²/ 4 π c

Suppose that two photo-detectors have identical sensitivity η ₁=η ₂, in electric treatment module, compare the microwave power that two detectors export, can obtain amplitude comparison function (ACF) is:

$\mathrm{ACF}=\frac{P_2}{P_1}\frac{{\sin }^2({\mathrm{\ψ}}_1-2\mathrm{\α})}{{\sin }^2({\mathrm{\ψ}}_1+2\mathrm{\α})}=\frac{{\sin }^2(-{\mathrm{\λ}}^2{D}_{w}L{\mathrm{\Ω}}^2/4\mathrm{\πc}+2\mathrm{\α})}{{\sin }^2(-{\mathrm{\λ}}^2{D}_{w}L{\mathrm{\Ω}}^2/4\mathrm{\πc}-2\mathrm{\α})}---\left(4\right)$

From formula (4), amplitude comparison function (ACF) has nothing to do with light source power and the index of modulation.

And the obtainable peak frequency of this system can be obtained by formula (5)

As can be seen from formula (5), α is respectively within the scope of 0 ° ~ 45 ° and 45 ° ~ 90 ° two during value, and ACF curve can overturn, and namely trap wave point can become peak value.Therefore, α is controlled within the scope of 0 ° ~ 45 °, in order to ensure to interfere, α ≠ 0 ° or 45 °, and D _wl is also set to fixed value, then only changes the feature that α observes ACF response.

The beneficial effects of the utility model are specific as follows:

The utility model makes full use of light polarization modulation and polarization beam splitting principle, achieves the tunable Instantaneous Frequency Measurement of high accuracy with Microwave photonics method, and structure is simple, and stability is high, therefore has high using value.

Accompanying drawing explanation

The tunable Instantaneous Frequency Measurement system schematic of a kind of high accuracy of Fig. 1.

Fig. 2 high accuracy tunable Instantaneous Frequency Measurement system radio frequency signal (2GHz≤f≤6.4GHz) ACF curve chart.

Fig. 3 Fig. 2 high accuracy tunable Instantaneous Frequency Measurement system radio frequency signal (2GHz≤f≤11.2GHz) ACF curve chart.

Fig. 4 Fig. 2 high accuracy tunable Instantaneous Frequency Measurement system radio frequency signal (2GHz≤f≤14.5GHz) ACF curve chart.

Fig. 5 Fig. 2 high accuracy tunable Instantaneous Frequency Measurement system radio frequency signal (2GHz≤f≤17GHz) ACF curve chart.

Fig. 6 Fig. 2 high accuracy tunable Instantaneous Frequency Measurement system radio frequency signal (2GHz≤f≤18.2GHz) ACF curve chart.

Embodiment

Below in conjunction with accompanying drawing 1 to 6, the tunable Instantaneous Frequency Measurement system of a kind of high accuracy is further described.

Embodiment one

The tunable Instantaneous Frequency Measurement system of a kind of high accuracy, as shown in Figure 1, it is characterized in that: this measuring system comprises, continuous-wave laser 1, first Polarization Controller 2, light polarization modulator 3, radio-frequency signal source 4, bias voltage source 5, second Polarization Controller 6, polarization beam apparatus 7, first monomode fiber 8, second monomode fiber 9, first photodetector 10, second photodetector 11, electric treatment module 12; Concrete connected mode is:

The light input end of light output termination first Polarization Controller 2 of continuous-wave laser 1, the light input end of the light output termination light polarization modulator 3 of the first Polarization Controller 2, the rf inputs 32 of the output termination light polarization modulator 3 of radio-frequency signal source 4, the bias input end 33 of the output termination light polarization modulator 3 of bias voltage source 5, the light input end of light output termination second Polarization Controller 6 of light polarization modulator 3, the input of the light output termination polarization beam apparatus 7 of the second Polarization Controller 6, first output 71 of polarization beam apparatus 7 connects the input of the first monomode fiber 8, the input of output termination first photodetector 10 of the first monomode fiber 8, the first input end 121 of the output termination electric treatment module 12 of the first photodetector 10, second output 72 of polarization beam apparatus 7 connects the input of the second monomode fiber 9, the input of output termination second photodetector 11 of the second monomode fiber 9, second input 122 of the output termination electric treatment module 12 of the second photodetector 11.

Output angle [alpha]=5 ° of the first Polarization Controller (2);

Light polarization modulator (3) has complementary phases modulation depth, and be respectively+β and-β, wherein β value will meet small signal modulation, β=0.1;

The half-wave voltage V of light polarization modulator (3) _π=2V

Regulate the output voltage V of bias voltage source (5) _bias=0.5V _π=1V;

Regulate radio-frequency signal source (4) output signal frequency f, frequency range is 2GHz≤f≤6.4GHz;

Regulate output phase place σ=45 ° of the second Polarization Controller (6);

Set the dispersion values D of the first monomode fiber (8) and the second monomode fiber (9) _w=16.75ps/kmnm, length L=10km;

By regulating polarization phase α, we can regulate the trap wave point frequency f of ACF curve.Corresponding ACF curve as shown in Figure 2.

Embodiment two

The tunable Instantaneous Frequency Measurement system of a kind of high accuracy, as shown in Figure 1, it is characterized in that: this measuring system comprises, continuous-wave laser 1, first Polarization Controller 2, light polarization modulator 3, radio-frequency signal source 4, bias voltage source 5, second Polarization Controller 6, polarization beam apparatus 7, first monomode fiber 8, second monomode fiber 9, first photodetector 10, second photodetector 11, electric treatment module 12; Concrete connected mode is:

The light input end of light output termination first Polarization Controller 2 of continuous-wave laser 1, the light input end of the light output termination light polarization modulator 3 of the first Polarization Controller 2, the rf inputs 32 of the output termination light polarization modulator 3 of radio-frequency signal source 4, the bias input end 33 of the output termination light polarization modulator 3 of bias voltage source 5, the light input end of light output termination second Polarization Controller 6 of light polarization modulator 3, the input of the light output termination polarization beam apparatus 7 of the second Polarization Controller 6, first output 71 of polarization beam apparatus 7 connects the input of the first monomode fiber 8, the input of output termination first photodetector 10 of the first monomode fiber 8, the first input end 121 of the output termination electric treatment module 12 of the first photodetector 10, second output 72 of polarization beam apparatus 7 connects the input of the second monomode fiber 9, the input of output termination second photodetector 11 of the second monomode fiber 9, second input 122 of the output termination electric treatment module 12 of the second photodetector 11.

Output angle [alpha]=15 ° of the first Polarization Controller (2);

Light polarization modulator (3) has complementary phases modulation depth, and be respectively+β and-β, wherein β value will meet small signal modulation, β=0.15;

The half-wave voltage V of light polarization modulator (3) _π=3V

Regulate the output voltage V of bias voltage source (5) _bias=0.5V _π=1.5V;

Regulate radio-frequency signal source (4) output signal frequency f, frequency range is 2GHz≤f≤11.2GHz;

Regulate output phase place σ=45 ° of the second Polarization Controller (6);

Set the dispersion values D of the first monomode fiber (8) and the second monomode fiber (9) _w=16.75ps/kmnm, length L=10km;

By regulating polarization phase α, we can regulate the trap wave point frequency f of ACF curve.Corresponding ACF curve as shown in Figure 3.

Embodiment three

The tunable Instantaneous Frequency Measurement system of a kind of high accuracy, as shown in Figure 1, it is characterized in that: this measuring system comprises, continuous-wave laser 1, first Polarization Controller 2, light polarization modulator 3, radio-frequency signal source 4, bias voltage source 5, second Polarization Controller 6, polarization beam apparatus 7, first monomode fiber 8, second monomode fiber 9, first photodetector 10, second photodetector 11, electric treatment module 12; Concrete connected mode is:

The light input end of light output termination first Polarization Controller 2 of continuous-wave laser 1, the light input end of the light output termination light polarization modulator 3 of the first Polarization Controller 2, the rf inputs 32 of the output termination light polarization modulator 3 of radio-frequency signal source 4, the bias input end 33 of the output termination light polarization modulator 3 of bias voltage source 5, the light input end of light output termination second Polarization Controller 6 of light polarization modulator 3, the input of the light output termination polarization beam apparatus 7 of the second Polarization Controller 6, first output 71 of polarization beam apparatus 7 connects the input of the first monomode fiber 8, the input of output termination first photodetector 10 of the first monomode fiber 8, the first input end 121 of the output termination electric treatment module 12 of the first photodetector 10, second output 72 of polarization beam apparatus 7 connects the input of the second monomode fiber 9, the input of output termination second photodetector 11 of the second monomode fiber 9, second input 122 of the output termination electric treatment module 12 of the second photodetector 11.

Output angle [alpha]=25 ° of the first Polarization Controller (2);

Light polarization modulator (3) has complementary phases modulation depth, and be respectively+β and-β, wherein β value will meet small signal modulation, β=0.2;

The half-wave voltage V of light polarization modulator (3) _π=4V

Regulate the output voltage V of bias voltage source (5) _bias=0.5V _π=2V;

Regulate radio-frequency signal source (4) output signal frequency f, frequency range is 2GHz≤f≤14.5GHz;

Regulate output phase place σ=45 ° of the second Polarization Controller (6);

Set the dispersion values D of the first monomode fiber (8) and the second monomode fiber (9) _w=16.75ps/kmnm, length L=10km;

By regulating polarization phase α, we can regulate the trap wave point frequency f of ACF curve.Corresponding ACF curve as shown in Figure 4.

Embodiment four

The tunable Instantaneous Frequency Measurement system of a kind of high accuracy, as shown in Figure 1, it is characterized in that: this measuring system comprises, continuous-wave laser 1, first Polarization Controller 2, light polarization modulator 3, radio-frequency signal source 4, bias voltage source 5, second Polarization Controller 6, polarization beam apparatus 7, first monomode fiber 8, second monomode fiber 9, first photodetector 10, second photodetector 11, electric treatment module 12; Concrete connected mode is:

The light input end of light output termination first Polarization Controller 2 of continuous-wave laser 1, the light input end of the light output termination light polarization modulator 3 of the first Polarization Controller 2, the rf inputs 32 of the output termination light polarization modulator 3 of radio-frequency signal source 4, the bias input end 33 of the output termination light polarization modulator 3 of bias voltage source 5, the light input end of light output termination second Polarization Controller 6 of light polarization modulator 3, the input of the light output termination polarization beam apparatus 7 of the second Polarization Controller 6, first output 71 of polarization beam apparatus 7 connects the input of the first monomode fiber 8, the input of output termination first photodetector 10 of the first monomode fiber 8, the first input end 121 of the output termination electric treatment module 12 of the first photodetector 10, second output 72 of polarization beam apparatus 7 connects the input of the second monomode fiber 9, the input of output termination second photodetector 11 of the second monomode fiber 9, second input 122 of the output termination electric treatment module 12 of the second photodetector 11.

Output angle [alpha]=5 ° of the first Polarization Controller (2);

Light polarization modulator (3) has complementary phases modulation depth, and be respectively+β and-β, wherein β value will meet small signal modulation, β=0.25;

The half-wave voltage V of light polarization modulator (3) _π=5V

Regulate the output voltage V of bias voltage source (5) _bias=0.5V _π=2.5V;

Regulate radio-frequency signal source (4) output signal frequency f, frequency range is 2GHz≤f≤17GHz;

Regulate output phase place σ=45 ° of the second Polarization Controller (6);

Set the dispersion values D of the first monomode fiber (8) and the second monomode fiber (9) _w=16.75ps/kmnm, length L=10km;

By regulating polarization phase α, we can regulate the trap wave point frequency f of ACF curve.Corresponding ACF curve as shown in Figure 5.

Embodiment five

The tunable Instantaneous Frequency Measurement system of a kind of high accuracy, as shown in Figure 1, it is characterized in that: this measuring system comprises, continuous-wave laser 1, first Polarization Controller 2, light polarization modulator 3, radio-frequency signal source 4, bias voltage source 5, second Polarization Controller 6, polarization beam apparatus 7, first monomode fiber 8, second monomode fiber 9, first photodetector 10, second photodetector 11, electric treatment module 12; Concrete connected mode is:

The light input end of light output termination first Polarization Controller 2 of continuous-wave laser 1, the light input end of the light output termination light polarization modulator 3 of the first Polarization Controller 2, the rf inputs 32 of the output termination light polarization modulator 3 of radio-frequency signal source 4, the bias input end 33 of the output termination light polarization modulator 3 of bias voltage source 5, the light input end of light output termination second Polarization Controller 6 of light polarization modulator 3, the input of the light output termination polarization beam apparatus 7 of the second Polarization Controller 6, first output 71 of polarization beam apparatus 7 connects the input of the first monomode fiber 8, the input of output termination first photodetector 10 of the first monomode fiber 8, the first input end 121 of the output termination electric treatment module 12 of the first photodetector 10, second output 72 of polarization beam apparatus 7 connects the input of the second monomode fiber 9, the input of output termination second photodetector 11 of the second monomode fiber 9, second input 122 of the output termination electric treatment module 12 of the second photodetector 11.

Output angle [alpha]=40 ° of the first Polarization Controller (2);

Light polarization modulator (3) has complementary phases modulation depth, and be respectively+β and-β, wherein β value will meet small signal modulation, β=0.3;

The half-wave voltage V of light polarization modulator (3) _π=6V

Regulate the output voltage V of bias voltage source (5) _bias=0.5V _π=3V;

Regulate radio-frequency signal source (4) output signal frequency f, frequency range is 2GHz≤f≤18.2GHz;

Regulate output phase place σ=45 ° of the second Polarization Controller (6);

Set the dispersion values D of the first monomode fiber (8) and the second monomode fiber (9) _w=16.75ps/kmnm, length L=10km;

By regulating polarization phase α, we can regulate the trap wave point frequency f of ACF curve.Corresponding ACF curve as shown in Figure 6.

Claims (2)

1. the tunable Instantaneous Frequency Measurement system of high accuracy, it is characterized in that: this measuring system comprises, continuous-wave laser (1), the first Polarization Controller (2), light polarization modulator (3), radio-frequency signal source (4), bias voltage source (5), the second Polarization Controller (6), polarization beam apparatus (7), the first monomode fiber (8), the second monomode fiber (9), the first photodetector (10), the second photodetector (11), electric treatment module (12); Concrete connected mode is:

The light input end of light output termination first Polarization Controller (2) of continuous-wave laser (1), the light input end of the light output termination light polarization modulator (3) of the first Polarization Controller (2), the rf inputs (31) of the output termination light polarization modulator (3) of radio-frequency signal source (4), the bias input end (32) of the output termination light polarization modulator (3) of bias voltage source (5), the light input end of light output termination second Polarization Controller (6) of light polarization modulator (3), the input of the light output termination polarization beam apparatus (7) of the second Polarization Controller (6), first output (71) of polarization beam apparatus (7) connects the input of the first monomode fiber (8), the input of output termination first photodetector (10) of the first monomode fiber (8), the first input end (121) of output termination electric treatment module (12) of the first photodetector (10), second output (72) of polarization beam apparatus (7) connects the input of the second monomode fiber (9), the input of output termination second photodetector (11) of the second monomode fiber (9), second input (122) of output termination electric treatment module (12) of the second photodetector (11).

2. the tunable Instantaneous Frequency Measurement system of a kind of high accuracy according to claim 1, is characterized in that:

The output angle [alpha] of the first Polarization Controller (2), α scope is 5 °≤α≤40 °;

Light polarization modulator (3) has complementary phases modulation depth, and be respectively+β and-β, wherein β value will meet small signal modulation, 0.1≤β≤0.3;

The half-wave voltage V of light polarization modulator (3) _π, half-wave voltage scope is 2V≤V _π≤ 6V

Regulate the output voltage V of bias voltage source (5) _bias, make V _bias1=0.5V _π;

Regulate radio-frequency signal source (4) output signal frequency f, frequency range is 2GHz≤f≤18.2GHz;

Regulate the output phase place σ of the second Polarization Controller (6), σ=45 °;

Set the dispersion values D of the first monomode fiber (8) and the second monomode fiber (9) _w=16.75ps/kmnm, length L=10km.