CN111277325A - Instantaneous frequency measurement method and system with adjustable measurement range based on polarization modulator - Google Patents
Instantaneous frequency measurement method and system with adjustable measurement range based on polarization modulator Download PDFInfo
- Publication number
- CN111277325A CN111277325A CN202010067523.3A CN202010067523A CN111277325A CN 111277325 A CN111277325 A CN 111277325A CN 202010067523 A CN202010067523 A CN 202010067523A CN 111277325 A CN111277325 A CN 111277325A
- Authority
- CN
- China
- Prior art keywords
- optical
- mode
- frequency
- polarization
- wave
- Prior art date
- Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
- Granted
Links
Images
Classifications
-
- H—ELECTRICITY
- H04—ELECTRIC COMMUNICATION TECHNIQUE
- H04B—TRANSMISSION
- H04B10/00—Transmission systems employing electromagnetic waves other than radio-waves, e.g. infrared, visible or ultraviolet light, or employing corpuscular radiation, e.g. quantum communication
- H04B10/07—Arrangements for monitoring or testing transmission systems; Arrangements for fault measurement of transmission systems
- H04B10/075—Arrangements for monitoring or testing transmission systems; Arrangements for fault measurement of transmission systems using an in-service signal
- H04B10/079—Arrangements for monitoring or testing transmission systems; Arrangements for fault measurement of transmission systems using an in-service signal using measurements of the data signal
- H04B10/0795—Performance monitoring; Measurement of transmission parameters
Abstract
The invention provides a polarization modulator-based instantaneous frequency measurement method and system with adjustable measurement range, and relates to the field of microwave photonics. In the system, TE and TM modes of light waves are subjected to equal-amplitude reverse modulation through a light polarization modulator, relative phase shift is introduced between the TE and TM modes through bias voltage, after TE and TM modes of light waves are combined through an optical power splitter branch and a polarizing film, equal-quantity dispersion is introduced into an upper path and a lower path through a dispersion module formed by optical fibers, frequency information of a signal to be measured is mapped onto phase information caused by dispersion, photoelectric conversion is carried out through a PD, the frequency information is transferred to the amplitude of alternating current components of light current, an amplitude comparison function ACF is constructed by using the alternating current components in an optical circuit, and the frequency of the signal to be measured can be calculated through the ACF function. The system has simple structure, the system measurement range can be changed by adjusting the bias voltage and the polarization angle of the lower branch, and the system measurement resolution can be improved by optimizing the slope of the ACF.
Description
Technical Field
The invention relates to the field of optical communication and the technical field of microwave photonics measurement, in particular to a frequency-amplitude mapping frequency measurement technology for converting frequency information of a microwave signal into power information through a dispersion effect, and provides an instantaneous frequency measurement method and an instantaneous frequency measurement system which are simple in system structure, can change the measurement range of the system by adjusting a bias voltage and a polarization angle of a lower branch and can improve the measurement resolution of the system by optimizing the slope of an ACF.
Background
In the field of Electronic Warfare (EW), instantaneous microwave frequency measurements (IFM) of received radar signals can be used to identify unknown Radio Frequencies (RF) prior to further processing. Due to its inherent electrical bottleneck, conventional electronic frequency monitors have a limited measurement range, focus on 0.5 to 18GHz, and perform poorly in complex and variable environments. Photon-assisted instantaneous frequency measurement is considered a new approach to addressing electronic bottlenecks. Compared with the traditional electronic method for microwave frequency measurement, the photon auxiliary method has a larger measurement range, is not easily influenced by environmental factors such as temperature, humidity and the like, and has unique advantages in the aspect of anti-electromagnetic interference.
At present, many microwave frequency measurement methods based on microwave photonics have been proposed, and photonic microwave frequency measurement schemes can be roughly classified into 5 types: scanning type frequency measurement, frequency-amplitude mapping type frequency measurement, frequency-space mapping type frequency measurement, frequency-time domain mapping type frequency measurement and photon compression sensing technology. The scanning type photon frequency measurement scheme can be roughly divided into two schemes, one scheme is that the microwave frequency information is displayed in a time domain scanning mode by utilizing the special properties of some optical devices; the other is based on the scanning characteristics of the wavelength of the light. The frequency-space mapping type is a type of converting microwave frequency information into a distribution in a spatial position or a distribution at different output ports, and is also called as a channelized filter type frequency measurement. The frequency-time domain mapping type frequency measurement scheme is characterized in that a microwave signal to be measured is loaded on an optical wave according to different time delays of the optical wave with different wavelengths passing through a dispersion medium, and a mapping relation between the frequency of the microwave signal and the time delay is established. The optical domain compressed sensing technology is used for greatly compressing the size of an original signal through an observation matrix irrelevant to Fourier basis aiming at a microwave signal with sparse frequency, then sampling, and accurately recovering the original signal with high probability through a reconstruction algorithm. The physical mechanism of the frequency-amplitude mapping type frequency measurement scheme is to convert frequency information of a microwave signal into amplitude (or power) information and indirectly measure a frequency value to be measured by detecting the amplitude information. Frequency-amplitude mapping can be divided into two categories: one is to convert the microwave frequency information into microwave power, detect and compare the microwave power value and demodulate to get the frequency value; the other is to convert the microwave frequency information into optical power and analyze the microwave frequency by means of optical power detection. The first requires the use of a dispersive medium to establish two complementary optical filters for the amplitude comparison function (required for the second), and estimates the microwave frequency by monitoring the optical power.
Research shows that the microwave frequency measurement precision implemented by the scanning type frequency measurement based on the scheme is related to the stability of the selected light source and the optical filter, and the measurement precision is often not very high because the output wavelength of the light source and the transmission function of the optical filter are easily influenced by the external environment and the filtering bandwidth of the optical filter is limited; the frequency-time mapping type frequency measurement scheme can often realize simultaneous measurement of a plurality of frequencies, but the spectral width of the ultrashort pulse is far beyond the observation bandwidth of the existing photoelectric detector and oscilloscope, so that the spectral resolution is poor; the photon compression sensing technology is difficult to directly digitize signals with large bandwidth because the sampling rate of the current analog-to-digital converter is limited; the frequency-amplitude mapping frequency measurement scheme has the advantages of capability of realizing instantaneous measurement, simple structure, larger measurable frequency and higher resolution, and becomes a hotspot of the current instantaneous frequency measurement technology.
Currently, researchers have proposed various schemes to implement instantaneous frequency measurement, which can be mainly classified into two categories: (1) the microwave frequency information is converted into optical power. Such as: a single laser and a pair of complementary comb filters are used to align the optical carrier with the peaks or valleys of the transmission frequency response. Although optical power can be converted to photocurrent by the low-speed PD, the frequency measurement range is typically half of the Free Spectral Range (FSR) of the filter. (2) And converting the microwave frequency information into microwave power. Such as: the frequency measurement is realized by a Phase Modulator (PM), a polarization modulator (PolM) and a Mach-Zehnder modulator (MZM), respectively. Although the measurement range can be increased by reducing the length of the dispersive medium, the measurement resolution is still limited. In order to balance the measurement range and resolution of an IFM system, an IFM with adjustable measurement range is expected to provide a solution. Two lasers of different wavelengths and one PolM can be used to obtain the tunable range of frequency measurement and improve resolution by reducing the measurement range of the ACF curve. But the use of twin lasers increases system cost; the measurement range can also be adjusted by adjusting the wavelength of the laser or the dispersion of the dispersive element, but recalibration is required to ensure measurement accuracy and the system cannot make instantaneous measurements; furthermore, a tunable measurement range can be achieved based on a dual-polarized mach-zehnder modulator (DPol-MZM), but the system requires complex bias control to minimize the bias drift of the MZM. The microwave power monitoring system based on two wavelengths performs well in the aspect of range adjustability, but has the obvious defect that the slope of the ACF function is small, so that the measurement resolution is low.
Research shows that based on the existing instantaneous frequency measurement system, the instantaneous frequency measurement method and the system have simple system structure, can change the measurement range of the system by adjusting the bias voltage and the polarization angle of the lower branch circuit, and can improve the measurement resolution of the system by optimizing the slope of the ACF.
Disclosure of Invention
The invention provides a microwave instantaneous frequency measurement method and a microwave instantaneous frequency measurement system based on an adjustable measurement range of a polarization modulator.
The system mainly comprises a continuous wave laser (CW), a light polarization modulator (PolM), a Single Mode Fiber (SMF), two polarizing plates (Pol), two Photoelectric Detectors (PD), two optical circulators and three Polarization Controllers (PC). In this scheme, PolM acts as a special phase modulator, supporting both modulation of the Transverse Electric (TE) and Transverse Magnetic (TM) modes, with complementary phase modulation indices. The linearly polarized light wave output by the CW laser is coupled into the PolM through PC0 and is modulated in the PolM by the microwave signal to be measured. The PC0 is used here to adjust the polarization direction of the incident light wave to 45 ° relative to the principal axis of the PolM so that the TE mode and TM mode in the PolM have the same power. DC bias voltage VbiasThe coupling with the microwave signal to be measured is simultaneously applied to the PolM, so that a certain phase difference is introduced between the two orthogonal modes. If the light wave emitted by the CW laser is denoted as E0exp(jωct), assuming the microwave signal to be measured is a sine wave with unknown angular frequency Ω, the output optical wave field of the PolM can be expressed as
In the formula, m ═ pi VRF/VπDenotes the modulation index, # V, of PolMbias/VπIs a phase shift caused by a DC bias, where VRFIs the voltage of the RF signal, VπRepresenting the half-wave voltage of PolM. It can be seen that the TE and TM modes introduce additional phase shifts + ψ and- ψ, respectively, so that there is a relative phase shift of 2 ψ between the two modes. Applying the Jacobi-Anger extension to formula (1) to obtain
Wherein Jn(. cndot.) denotes a Bessel function of order n of the first class. In small signal conditions, the second and higher order sidebands are ignored here. It can be seen from equation (2) that the TE mode and TM mode optical wave fields of the PolM output both include an optical carrier and two 1-order sidebands, and the optical carriers and ± 1-order sidebands of the TE mode and the TM mode in the output optical wave field are equal in amplitude, while the + 1-order sidebands in the TE mode lead the optical carrier in phase and the-1-order sidebands lag the optical carrier in phase, and the + 1-order sidebands in the TE mode lag the optical carrier in phase and the-1-order sidebands lead the optical carrier in phase.
To construct the amplitude comparison function, the PolM output light wave was split into two beams by a 1 × 2 optical power splitter. In the upper branch, the TE mode in the x-axis direction is extracted by the cascade of polarizers Pol1 and PC1, i.e.
In the lower arm, the combined linearly polarized light waves were projected by adjusting PC2 into the orthogonal polarized TE and TM modes at polarization angle α onto the transmission axis of Pol2
As can be seen from equation (4), since the optical carriers and the two 1-order sidebands in the TE and TM modes are different in phase, Pol2 outputs that the optical carriers and the two 1-order sidebands in the linearly polarized optical waves have different amplitudes and phases from the corresponding optical frequency components of the TE mode output from the upper branch.
To map the frequency information onto the phase, the same phase shift is introduced for the upper and lower arms by the dispersion module. The dispersion module is composed of a section of single-mode fiber SMF and two optical circulators, is used for realizing bidirectional independent transmission of optical signals, and experiences the same dispersion, and the phase shifts of the same frequency components are completely equal. The light wave from the upper branch is injected into SMF through a port 1-2 of the optical circulator 1, and is output through a port 2-3 of the circulator 2 after being transmitted by the optical fiber; meanwhile, the light wave from the lower branch is injected into SMF along the opposite direction through the port 1-2 of the optical circulator 2 and is output from the port 2-port 3 of the optical circulator 1; since the two optical signals are transmitted in opposite directions on the same SMF and separately output, the dispersion experienced by the two optical signals is the same and the phase shifts introduced by the optical frequency components of the same frequency are exactly equal. If the propagation constant of the light wave in the optical fiber can be expressed as
Wherein β (ω)c) Is at an angular frequency ωcPropagation constant of (c), β' (ω)c) And β' (ωc) Is β (omega) with respect to angular frequency omegacFirst and second derivatives of, and β' (ω)c)＝-λ0 2D/2 π c, wherein D and λ0＝2πc/ω0Third order and other higher order derivatives of β (ω), neglecting the dispersion coefficient of the SMF and the center wavelength of the optical carrier, respectively, at ωcSum of phase shifts at ωcThe phase shift of the sidebands at + -omega can be expressed as
Where L is the fiber length. The light waves output from the circulators 1 and 2 after being transmitted through the optical fiber can be expressed as
As can be seen from equations (7) and (8), the phase shift caused by the fiber dispersion
Depending only on the frequency of the optical wave, regardless of TE or TM mode.
The square law photodetectors PD1 and PD2 convert the optical signals into electrical signals, and the photocurrent is i (t) - η | e (t) -ventilated2Wherein the AC component in the photocurrent can be expressed as
Where η is the responsivity of the PD from the photocurrent, an Amplitude Comparison Function (ACF) can be constructed:
according to the formula (11), for the light source wavelength λ0PolM half-wave voltage VπThe dispersion coefficient D and the length L of the optical fiber are constant, the phase shift experienced by the upper and lower branch optical signals and the bias voltage V of the PolMbiasThe polarization angle α, the frequency of the optical signal and the microwave signal to be measured are related, when the polarization angle α and the bias voltage VbiasWhile fixed, the ACF is a function of the frequency of the microwave signal to be measured, independent of the optical power and the input microwave power, and thus the frequency of the microwave signal to be measured can be estimated based on the ACF, the adjustment polarization angle α and the bias voltage VbiasThe position of the peak point of the ACF can be changed, thereby adjusting the frequency measurement range.
The present invention provides a microwave Instantaneous Frequency Measurement (IFM) system. .
The system consists of light modulation part, contrast light path part,The dispersion module and the signal processing part are formed. Wherein the light modulation section includes: a continuous wave laser CW LD, a light polarization controller PC0, a DC voltage source, a light polarization modulator PolM; the contrast light path part includes: a 1 × 2 optical power splitter, two polarizers Pol, two light polarization controllers PC1 and PC 2; the dispersion module includes: two optical circulators and a section of single mode fiber SMF; the signal processing section includes: two photodetectors PD1 and PD 2. Continuous wave laser CW LD: for generating the desired central wavelength of lambda0The continuous light wave is used as an optical carrier of a microwave signal to be measured, an optical polarization controller PC0 is used for adjusting the polarization direction of linearly polarized light output by a CW LD and enabling the polarization direction of input linearly polarized light and the polarization directions of a TE mode and a TM mode of PolM to form an included angle of 45 degrees, a direct-current voltage source is used for providing direct-current bias voltage coupled with the microwave signal to be measured and changing the magnitude of phase shift introduced by the TE mode and the TM mode of output light waves of PolM through adjusting the bias voltage so as to adjust the instantaneous frequency measurement range, a polarization modulator PolM is used for conducting phase modulation with equal amplitude and opposite phase of modulation indexes on the TE mode and the TM mode of input light waves under the driving of the microwave signal to be measured and introducing opposite phase shift to the light waves of the TE mode and the TM mode of output light waves through the direct-current bias voltage coupled with the microwave signal to be measured, a 1 x 2 power splitter is used for splitting the light signal output from the PolM into two paths, polarizing controllers PC1 and PC2 are used for adjusting the polarization direction of the polarization of linearly polarized light entering a polarizer Pol, a polarizer 1 is used for extracting the TE mode along the TE mode and isolating the TE mode, the linear polarization frequency dispersion characteristic of the light signal, the light signal introduced into a single-polarized light wave dispersion port of the polarizer 82, the polarizer is used for realizing the linear dispersion of the linear polarization signal, the linear polarization signal is used for realizing the linear dispersion characteristic of the linear polarization signal introduced into the linear polarization signal, the linear polarization signal is used for realizing the linear polarization signal introduced intoA shooting relationship; photodetectors PD1 and PD 2: the method is used for converting optical signals output by the upper branch circuit and the lower branch circuit into electric signals and extracting alternating current components to construct an ACF function.
Compared with other microwave instantaneous frequency measurement systems, the microwave signal instantaneous frequency method and the microwave signal instantaneous frequency measurement system provided by the invention have the advantages that: the system only needs one laser, one polarization modulator and one section of single-mode fiber, and has simple structure and low system cost; the used optical modulator is a polarization modulator, only one direct current bias is needed to be added, and complex bias control is not needed, so that the system stability cannot be influenced by bias voltage drift; the system measurement range can be adjusted by changing the bias voltage and the polarization angle of the lower branch, so that the system has higher flexibility; the system has larger ACF curve slope in a lower frequency band, and the measurement resolution of the system is improved. Therefore, the instantaneous frequency measurement system provided by the invention has the advantages of simple structure, low cost and no need of complex bias control, can effectively improve the slope of the ACF curve, further improve the resolution of the measurement system, and has adjustable measurement range, thereby having important practical significance.
Drawings
FIG. 1 is a schematic diagram of the instantaneous frequency measurement principle and system structure based on a polarization modulator
In FIG. 2, when the polarization angle α is fixed at 30 °, the bias voltages are adjusted to be 0.0056Vπ,0.017Vπ,0.042Vπ,0.083Vπ,0.25VπMeasured ACF curve
Fig. 3 when α is 30 ° Vbias＝0.25VπAnd comparing the microwave frequency measurement value with the theoretical value within 3-34.8GHz and determining the error.
FIG. 4 comparison of resolution values obtained based on simulated ACF curve differential operation with theoretical values
FIG. 5 shows the bias voltage when it is fixed at 0.25VπComparison of measured ACF with theoretical ACF at varying polarization angles of 10 °,20 °,30 °,40 °, and 45 °.
Fig. 6 when α is 45 °, Vbias＝0.25VπAnd comparing the microwave frequency measured within 3-42.8GHz with the theoretical value and determining the error.
Detailed Description
The invention provides a method and a system for realizing microwave instantaneous frequency measurement, wherein a system link is shown in figure 1, and the specific implementation needs to adopt the following steps:
linearly polarized light with the central wavelength of 1550nm and the line width of 0.5MHz emitted by the continuous wave laser is injected into a light polarization modulator PolM through a polarization controller PC0, and the PC0 is adjusted to enable the polarization direction of the linearly polarized light to form an included angle of 45 degrees with the polarization directions of a TE mode and a TM mode of the PolM, so that the components of the linearly polarized light in two orthogonal polarization states of the PolM are equal; unknown frequency microwave signal to be measured and a DC bias voltage VbiasThe coupling drive PolM performs phase modulation on the TE mode and the TM mode, wherein the modulation coefficients are equal in magnitude and opposite in sign. DC bias voltage V coupled with microwave signal to be measuredbiasFor introducing a certain phase difference between the TE mode and the TM mode. Because the power of the input RF signal is small, the second and higher order sidebands are negligible under small signal modulation.
The light wave output by the PolM is split into two beams by a 1 x 2 optical power splitter into two branches for different polarization processing to construct an amplitude comparison function, in the upper branch, the TE mode is extracted along the x-axis direction using Pol1 and PC1, while the TM mode is blocked and only the TE mode passes through the polarizer, in the lower branch, a linearly polarized light wave with a polarization angle α is formed by adjusting the transmission axis direction of Pol2 onto which Pol2 and PC2 project orthogonally polarized TE and TM modes at a polarization angle α.
A dispersion module is then used to introduce phase shifts for the upper and lower arms, mapping the frequency information onto the phase. The module consists of two optical circulators and a section of dispersive optical fiber with the length of 2km and the dispersion coefficient of 17 ps/nm/km. The light wave of the upper branch is injected into SMF through a port 1-2 of the optical circulator 1, and is output through a port 2-3 of the circulator 2 after being transmitted by the optical fiber; meanwhile, the optical wave of the lower branch is injected into SMF along the opposite direction through the port 1-2 of the optical circulator 2 and is output from the port 2-port 3 of the optical circulator 1; because two optical signals are transmitted on the same SMF along opposite directions, the two optical signals are separately output and are not influenced by polarization mode dispersion of optical fibers; since the dispersion experienced by both optical signals is the same, the phase shifts introduced by optical frequency components of the same frequency are exactly equal.
The signals output by the two circulators are photoelectrically converted by two photodiodes PD1 and PD2 with the sensitivity of 1mA/mW respectively. And extracting alternating current components of the output light currents of the PD1 and the PD2 and performing phase division budget to obtain an ACF value. At this time, the wavelength λ of the light source0PolM half-wave voltage VπThe dispersion coefficient D and the length L of the optical fiber are fixed when the polarization angle α and the bias voltage V are usedbiasAt a certain time, the ACF is not related to the optical power and the input microwave power, and is only a function of the microwave frequency, so that the frequency of the microwave signal to be measured can be calculated by using the ACF function. By regulating the DC bias voltage V applied to PolMbiasOr the polarization angle α may change where the peak of the ACF function occurs, i.e., may change the measurement range.
As shown in FIG. 2, when the polarization angle α is fixed at 30 °, the bias voltages are adjusted to 0.0056Vπ、0.017Vπ、0.042Vπ、0.083Vπ、0.25VπThe resulting ACF curves, corresponding to the measurement ranges of 3-8.2GHz, 3-14.2GHz, 3-22GHz, 3-28.6GHz and 3-34.8GHz, respectively, indicate that varying the bias voltage can change the system measurement range, FIG. 3 shows that when α is 30 degrees, V is shown in order to check the accuracy of the microwave frequency measurementbias＝0.25VπAnd comparing the frequency of the microwave signal measured within 3-34.8GHz with a theoretical value and determining the error. It can be seen that the microwave frequency of the frequency band above 3GHz is well matched with the theoretical value, and the maximum measurement error is kept below 0.1 GHz. In order to demonstrate the measurement resolution obtained by simulation, the resolution capability of the system is represented based on the differential operation of the simulated ACF, and the result is shown in fig. 4. As can be seen from fig. 4, the resolution calculated as a result of the simulation coincides with the theoretical value of the resolving power represented by the ACF difference, and the resolving power decreases as the frequency measurement range increases, which means that a trade-off is made between the measurement range and the accuracy in which the frequency measurement accuracy can be improved by appropriately decreasing the measurement range according to the actual situation.
FIG. 5 shows the bias voltage being fixed at 0.25VπACF and theory measured by varying the polarization angleComparison of ACF. As can be seen from fig. 5, by adjusting the polarization angles to 10 °,20 °,30 °,40 ° and 45 °, different measurement ranges of 3-20.2GHz, 3-28.6GHz, 3-35GHz, 3-40.4GHz, and 3-42.8GHz can be obtained, respectively, which means that the measurement ranges can also be adjusted by changing the polarization angles. When V isbias＝0.25VπThe maximum measurement range that can be obtained for the system is 42.8ghz when α is 45 deg. fig. 6 shows that when α is 45 deg., Vbias＝0.25VπAnd comparing the microwave frequency measured within 3-42.8GHz with the theoretical value and determining the error. It can be seen that the measured value of the microwave frequency of the frequency band above 3GHz is consistent with the theoretical value, and the maximum measurement error is still kept below 0.1 GHz.
In summary, the present invention provides a method and a system for measuring instantaneous frequency of microwave. The designed instantaneous frequency measurement system consists of a CW laser, a light polarization modulator, two polarizing plates, two circulators, three polarization controllers and a section of single-mode fiber, and has the advantages of simple structure, low cost, capability of changing the measurement range of the system by adjusting the bias voltage and the polarization angle of a lower branch and capability of improving the measurement resolution of the system by preferably selecting the slope of the ACF.
The above description is only for the specific embodiments of the present invention, but the scope of the present invention is not limited thereto, and any person skilled in the art can easily conceive of the changes or substitutions within the technical scope of the present invention, and all the changes or substitutions should be covered within the scope of the present invention. Therefore, the protection scope of the present invention shall be subject to the protection scope of the appended claims.
Claims (5)
1. An instantaneous frequency measurement method with adjustable measurement range based on an optical polarization modulator is characterized by comprising the following steps:
the wavelength emitted by CW LD of continuous wave laser is lambda0Is injected into the optical polarization modulator PolM via the polarization controller PC0 to achieve a frequency fUTAdjusting the PC0 to enable the polarization direction of the linearly polarized light and the polarization directions of the transverse electric TE mode and the transverse magnetic TM mode of the PolM to form an included angle of 45 degrees; TE mode and TM mode optical wave fields of PolM outputComprises an optical carrier and two 1 st order sidebands; by adjusting the DC bias voltage V applied to PolM coupled with the microwave signal to be measuredbiasIntroducing a certain phase difference between two orthogonal TE modes and TM modes, dividing the light wave output by PolM into an upper branch and a lower branch by a 1X 2 optical power divider for constructing an amplitude comparison function, combining the orthogonally polarized TE and TM modes into a linearly polarized light wave with a polarization angle of α by an upper branch through a polarization controller PC1 and a polarizing plate Pol1 cascade structure, transmitting the optical signals of the upper branch and the lower branch through the same dispersion optical fiber by a dispersion module, introducing mutually independent and completely same phase shifts into the optical frequency components with the same frequency, linearly changing the phase shifts along with the signal frequency, converting the optical signals into current signals by square-law photodetectors PD1 and PD2, mapping the phase shift information in the optical signals into the alternating current signals of photocurrent, extracting the alternating current components of the upper branch and the lower branch, extracting the alternating current components, dividing the square phase to obtain an ACF to deduce the frequency of the signal to be measured, calculating the lambda value of the light source output wavelength by an ACF curve, and outputting a lambda value0PolM half-wave voltage VπThe dispersion coefficient D and the length L of the optical fiber are constant, the phase shift experienced by the upper and lower branch optical signals and the bias voltage V of the PolMbiasThe frequency of the signal to be measured and the optical signal with the polarization angle α are related to the frequency of the microwave signal to be measured, when the polarization angle α is equal to the bias voltage VbiasWhile fixed, the ACF is a function of the frequency of the microwave signal to be measured, independent of the optical power and the input microwave power, so that the frequency of the microwave signal to be measured can be calculated based on the ACF, and the polarization angle α and the bias voltage V are properly adjustedbiasThe position of the peak point of the ACF can be changed, thereby adjusting the frequency measurement range.
2. The method of claim 1, wherein the optical modulation of the microwave signal under test is:
the wavelength emitted by the continuous wave laser is lambda0The linearly polarized light wave is adjusted and injected into PolM by PC0, and PC0 is used for adjusting the photoelectric field vector direction of the linearly polarized light to enable the linearly polarized light to be in the polarization direction of a transverse electric TE mode and a transverse magnetic TM mode of the waveguide in PolMForming an included angle of 45 degrees, so that TE mode components and TM mode components of the light wave field have the same amplitude; PolM is a special phase modulator with a half-wave voltage VπThe phase modulator can perform phase modulation with equal modulation factor and opposite sign on the TE mode and the TM mode of the injected light wave, is equivalent to be composed of two phase modulators with opposite modulation indexes, and is coupled with a driving signal to generate direct current voltage VbiasRealizing the bias of PolM, the DC bias voltage V in the driving signalbiasThe TE mode and TM mode light wave fields are led into opposite phase shifts +/-psi; the TE mode and TM mode of the PolM output light wave are composed of a plurality of sidebands with equal frequency intervals, and the frequency is adjusted to be fUTTo-be-detected microwave signal voltage VRFEnsuring modulation index β ═ π VRF/VπThe value is taken to meet the small-signal condition, so that the signal amplitude of the second-order and higher-order sidebands is small enough to be ignored; the optical carrier waves of TE mode and TM mode in the output optical wave field are respectively equal to the amplitude of +/-1 order sideband, and the phase of +1 order sideband in the TE mode leads the optical carrier wave and the phase of-1 order sideband lags the optical carrier wave, and the phase of +1 order sideband in the TE mode lags the optical carrier wave and the phase of-1 order sideband leads the optical carrier wave; DC bias voltage VbiasMaking the opposite phase shift introduced by the TE mode and TM mode light wave fields form a phase difference 2 psi between the two; by adjusting the bias voltage VbiasThe relative phase between the optical carrier and each 1-order sideband can be changed, so that the frequency range of the microwave signal to be measured can be adjusted, and when the polarization angle α is fixed, VbiasWhen 0 the frequency measurement range is minimal, Vbias＝0.25VπThe measurement range is maximal.
3. The method of claim 1, wherein the contrast optical path:
a contrast optical path is formed by connecting a PC1 and Pol1 cascade structure in an upper branch with a polarization controller PC2 and a polaroid 2 cascade structure in a lower branch in parallel, a PolM output light wave is divided into two branches through a 1 x 2 optical power splitter, a Pol1 and a PC1 are used for extracting a TE mode and a TM mode is filtered out in the upper branch, orthogonally polarized TE and TM modes are projected to a transmission axis of Pol2 in the lower branch through a PC2 and combined into a linear polarized light wave with a polarization angle of α, but because the phases of a light carrier wave and two 1-order sidebands in the TE and TM modes are different, the light carrier wave and the two 1-order sidebands in the output polarized light wave of the Pol2 have different amplitudes and phases corresponding to light frequency components output by the upper branch, and linearly polarized light output by the upper branch is subjected to photoelectric conversion and then used for constructing an amplitude comparison function.
4. The method of claim 1, wherein the dispersion module:
the dispersion module is composed of a section of single-mode fiber SMF and two optical circulators, is used for realizing bidirectional independent transmission of optical signals, and experiences the same dispersion, and the phase shifts of the same frequency components are completely equal; the light wave from the upper branch is injected into SMF through a port 1-2 of the optical circulator 1, and is output through a port 2-3 of the circulator 2 after being transmitted by the optical fiber; meanwhile, the light wave from the lower branch is injected into SMF along the opposite direction through the port 1-2 of the optical circulator 2 and is output from the port 2-port 3 of the optical circulator 1; because two optical signals are transmitted and separately output on the same SMF along opposite directions, and the two optical signals are completely equivalent to each other under the influence of polarization mode dispersion of optical fibers; since the dispersion experienced by both optical signals is the same, the phase shifts introduced by optical frequency components of the same frequency are exactly equal.
5. A polarization modulator-based measurement-adjustable range instantaneous frequency measurement system, comprising:
continuous wave laser CW LD: for generating the desired central wavelength of lambda0The continuous light wave is used as the light carrier wave of the radio frequency signal;
light polarization controller PC 0: the polarization direction adjusting device is used for adjusting the polarization direction of linearly polarized light, so that the polarization direction of input linearly polarized light and the polarization directions of a TE mode and a TM mode of PolM form an included angle of 45 degrees;
light polarization modulator PolM: under the drive of a microwave signal to be detected, the device is used for carrying out modulation index equal-amplitude reverse-phase modulation on a TE mode and a TM mode of an input optical wave, and introducing opposite phase shift to the TE mode and the TM mode of an output optical wave through direct-current bias voltage coupled with the microwave signal to be detected;
a direct-current power supply: providing direct current bias voltage coupled with a microwave signal to be measured, changing the size of phase shift introduced by a TE mode and a TM mode of PolM output light waves by adjusting the bias voltage, and further adjusting the instantaneous frequency measurement range;
1 × 2 optical power splitter: dividing the optical signal output from the PolM into two paths;
light polarization controllers PC1 and PC 2: the linear polarization direction of the linear polarization light wave in the upper limit branch of the contrast light path is adjusted;
polarizing plate Pol 1: the system is used for extracting TE mode light waves along the x-axis direction and filtering TM modes;
a polarizer Pol2 for projecting the orthogonally polarized TE and TM modes into a linearly polarized light wave with a polarization angle of α, combined into α;
optical circulators 1 and 2: the optical device is a three-port optical device with nonreciprocal characteristics, optical signals can be output from the next port in sequence when being input from any port, and the port is not communicated with other ports and is used for realizing that the optical signals of the upper branch and the lower branch are transmitted in the opposite direction in the same single-mode optical fiber;
single-mode fiber: the chromatic dispersion characteristics of the optical fiber introduce phase shift linearly changing with wavelength for an optical carrier and two 1 st order sidebands in an optical signal, and the magnitude of the phase shift is determined by the dispersion coefficient D and the length L of a single mode optical fiber and the wavelength lambda of the optical signal0Determining, and the phase shift changes linearly with the frequency of the microwave signal to be measured to obtain a frequency-amplitude mapping relation;
photodetectors PD1 and PD 2: the optical fiber is used for performing photoelectric conversion on optical signals output by the upper and lower branches, and extracting alternating current components in output photocurrent for constructing an ACF function in an electrical domain.
Priority Applications (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| CN202010067523.3A CN111277325B (en) | 2020-01-20 | 2020-01-20 | Instantaneous frequency measurement method and system with adjustable measurement range based on polarization modulator |
Applications Claiming Priority (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| CN202010067523.3A CN111277325B (en) | 2020-01-20 | 2020-01-20 | Instantaneous frequency measurement method and system with adjustable measurement range based on polarization modulator |
Publications (2)
| Publication Number | Publication Date |
|---|---|
| CN111277325A true CN111277325A (en) | 2020-06-12 |
| CN111277325B CN111277325B (en) | 2021-05-04 |
Family
ID=70998971
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| CN202010067523.3A Expired - Fee Related CN111277325B (en) | 2020-01-20 | 2020-01-20 | Instantaneous frequency measurement method and system with adjustable measurement range based on polarization modulator |
Country Status (1)
| Country | Link |
|---|---|
| CN (1) | CN111277325B (en) |
Cited By (5)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN113315573A (en) * | 2021-05-28 | 2021-08-27 | 重庆邮电大学 | Optical auxiliary broadband microwave instantaneous frequency measurement method and device |
| CN113467418A (en) * | 2021-06-25 | 2021-10-01 | 河北工业大学 | Method for measuring performance index of control loop |
| CN113992263A (en) * | 2021-11-11 | 2022-01-28 | 浙大城市学院 | Broadband frequency measurement system and method based on microwave photon filtering and compressed sensing technology |
| CN114061916A (en) * | 2021-11-29 | 2022-02-18 | 南京航空航天大学 | Optical device frequency response measuring method and device |
| CN114513250A (en) * | 2021-12-31 | 2022-05-17 | 北京交通大学 | Instantaneous frequency measurement system and method based on differential optical time stretching principle |
Citations (19)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN101487738A (en) * | 2008-02-04 | 2009-07-22 | 北京高光科技有限公司 | Method and apparatus for measuring optical spectral property based on polarization analysis |
| CN101599800A (en) * | 2009-04-27 | 2009-12-09 | 北京邮电大学 | Utilize lithium niobate modulator to produce the apparatus and method of 8 times frequency optical millimeter waves |
| US7738598B1 (en) * | 2006-09-15 | 2010-06-15 | Itt Manufacturing Enterprises, Inc. | Detection and time-of-arrival estimation using an IFM receiver |
| CN103152098A (en) * | 2013-02-05 | 2013-06-12 | 北京邮电大学 | Polarization interference-based in-band optical signal-to-noise ratio detection method and device |
| CN204119235U (en) * | 2014-11-04 | 2015-01-21 | 北京交通大学 | The tunable Instantaneous Frequency Measurement system of a kind of high accuracy |
| CN104849550A (en) * | 2015-06-01 | 2015-08-19 | 北京交通大学 | Bias-voltage-control-based adjustable instantaneous frequency measure system |
| US9134355B2 (en) * | 2013-02-25 | 2015-09-15 | Ganesh Ramaswamy Basawapatna | Apparatus for very high speed adaptive spectrum analysis |
| CN105007120A (en) * | 2015-07-08 | 2015-10-28 | 北京邮电大学 | Eightfold-frequency optical millimeter wave generation method and system based on polarization modulator cascading |
| CN105812053A (en) * | 2016-03-07 | 2016-07-27 | 北京邮电大学 | Instantaneous frequency measuring method and system |
| CN106053938A (en) * | 2016-06-18 | 2016-10-26 | 西安电子科技大学 | Apparatus and method for realizing instantaneous microwave frequency measurement by dual polarization modulators |
| CN106100753A (en) * | 2016-06-02 | 2016-11-09 | 北京邮电大学 | Two-way wire and wireless mixed light cut-in method based on optical phase modulator and system |
| CN106656322A (en) * | 2016-09-19 | 2017-05-10 | 西安电子科技大学 | Device and method for realizing instantaneous frequency measurement using phase modulator |
| CN106788702A (en) * | 2016-11-16 | 2017-05-31 | 武汉邮电科学研究院 | It is a kind of to be based on 120 degree of coherent optical detection device and methods of optical mixer unit |
| US10135544B1 (en) * | 2018-01-19 | 2018-11-20 | Eagle Technology, Llc | Methods and apparatus for radio frequency (RF) photonic spectrometer using optical frequency combs |
| CN208459628U (en) * | 2018-05-30 | 2019-02-01 | 南京邮电大学 | A kind of mixing phasmon waveguide bragg grating with the double forbidden bands of TM, TE mode |
| CN109445155A (en) * | 2018-12-22 | 2019-03-08 | 复旦大学 | A kind of unpolarized type narrow-band optical bandpass filter of electric tuning |
| EP3486678A1 (en) * | 2017-11-17 | 2019-05-22 | Rohde & Schwarz GmbH & Co. KG | Multi-signal instantaneous frequency measurement system |
| CN110031832A (en) * | 2019-03-15 | 2019-07-19 | 西北工业大学 | A kind of microwave photon Doppler shift measurement system and its adjusting method |
| CN209375653U (en) * | 2018-11-27 | 2019-09-10 | 北京交通大学 | Optical power based on dual-polarization intensity modulator detects Instantaneous Frequency Measurement system |
-
2020
- 2020-01-20 CN CN202010067523.3A patent/CN111277325B/en not_active Expired - Fee Related
Patent Citations (19)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| US7738598B1 (en) * | 2006-09-15 | 2010-06-15 | Itt Manufacturing Enterprises, Inc. | Detection and time-of-arrival estimation using an IFM receiver |
| CN101487738A (en) * | 2008-02-04 | 2009-07-22 | 北京高光科技有限公司 | Method and apparatus for measuring optical spectral property based on polarization analysis |
| CN101599800A (en) * | 2009-04-27 | 2009-12-09 | 北京邮电大学 | Utilize lithium niobate modulator to produce the apparatus and method of 8 times frequency optical millimeter waves |
| CN103152098A (en) * | 2013-02-05 | 2013-06-12 | 北京邮电大学 | Polarization interference-based in-band optical signal-to-noise ratio detection method and device |
| US9134355B2 (en) * | 2013-02-25 | 2015-09-15 | Ganesh Ramaswamy Basawapatna | Apparatus for very high speed adaptive spectrum analysis |
| CN204119235U (en) * | 2014-11-04 | 2015-01-21 | 北京交通大学 | The tunable Instantaneous Frequency Measurement system of a kind of high accuracy |
| CN104849550A (en) * | 2015-06-01 | 2015-08-19 | 北京交通大学 | Bias-voltage-control-based adjustable instantaneous frequency measure system |
| CN105007120A (en) * | 2015-07-08 | 2015-10-28 | 北京邮电大学 | Eightfold-frequency optical millimeter wave generation method and system based on polarization modulator cascading |
| CN105812053A (en) * | 2016-03-07 | 2016-07-27 | 北京邮电大学 | Instantaneous frequency measuring method and system |
| CN106100753A (en) * | 2016-06-02 | 2016-11-09 | 北京邮电大学 | Two-way wire and wireless mixed light cut-in method based on optical phase modulator and system |
| CN106053938A (en) * | 2016-06-18 | 2016-10-26 | 西安电子科技大学 | Apparatus and method for realizing instantaneous microwave frequency measurement by dual polarization modulators |
| CN106656322A (en) * | 2016-09-19 | 2017-05-10 | 西安电子科技大学 | Device and method for realizing instantaneous frequency measurement using phase modulator |
| CN106788702A (en) * | 2016-11-16 | 2017-05-31 | 武汉邮电科学研究院 | It is a kind of to be based on 120 degree of coherent optical detection device and methods of optical mixer unit |
| EP3486678A1 (en) * | 2017-11-17 | 2019-05-22 | Rohde & Schwarz GmbH & Co. KG | Multi-signal instantaneous frequency measurement system |
| US10135544B1 (en) * | 2018-01-19 | 2018-11-20 | Eagle Technology, Llc | Methods and apparatus for radio frequency (RF) photonic spectrometer using optical frequency combs |
| CN208459628U (en) * | 2018-05-30 | 2019-02-01 | 南京邮电大学 | A kind of mixing phasmon waveguide bragg grating with the double forbidden bands of TM, TE mode |
| CN209375653U (en) * | 2018-11-27 | 2019-09-10 | 北京交通大学 | Optical power based on dual-polarization intensity modulator detects Instantaneous Frequency Measurement system |
| CN109445155A (en) * | 2018-12-22 | 2019-03-08 | 复旦大学 | A kind of unpolarized type narrow-band optical bandpass filter of electric tuning |
| CN110031832A (en) * | 2019-03-15 | 2019-07-19 | 西北工业大学 | A kind of microwave photon Doppler shift measurement system and its adjusting method |
Non-Patent Citations (4)
| Title |
|---|
| DANIEL LAM, BRANDON W. BUCKLEY, CEJO K. LONAPPAN, ASAD M. MADNI: "Ultra-wideband instantaneous frequency estimation , 48 and instantaneous frequency ,adjustable", 《IEEE INSTRUMENTATION & MEASUREMENT MAGAZINE》 * |
| SONGNIAN FU,JUNQIANG ZHOU: "Instantaneous Microwave Frequency Measurement Using Programmable Differential Group Delay (DGD) Modules", 《IEEE PHOTONICS JOURNAL》 * |
| 王照，马健新，张瑞姣，李艳杰，张齐齐，张琦，刘人豪，余建国: "基于单边带调制的直接探测光 ＯＦＤＭ－ＲｏＦ系", 《光电子激光》 * |
| 魏志虎，王荣，方涛，蒲涛，郑吉林，孙帼丹，甄飞: "基于偏振调制器和单模光纤的微波瞬时频率测", 《光电子激光》 * |
Cited By (9)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN113315573A (en) * | 2021-05-28 | 2021-08-27 | 重庆邮电大学 | Optical auxiliary broadband microwave instantaneous frequency measurement method and device |
| CN113315573B (en) * | 2021-05-28 | 2023-02-10 | 重庆邮电大学 | Optical-assisted broadband microwave instantaneous frequency measurement method |
| CN113467418A (en) * | 2021-06-25 | 2021-10-01 | 河北工业大学 | Method for measuring performance index of control loop |
| CN113467418B (en) * | 2021-06-25 | 2022-06-28 | 河北工业大学 | Method for measuring performance index of control loop |
| CN113992263A (en) * | 2021-11-11 | 2022-01-28 | 浙大城市学院 | Broadband frequency measurement system and method based on microwave photon filtering and compressed sensing technology |
| CN114061916A (en) * | 2021-11-29 | 2022-02-18 | 南京航空航天大学 | Optical device frequency response measuring method and device |
| CN114061916B (en) * | 2021-11-29 | 2022-08-02 | 南京航空航天大学 | Optical device frequency response measuring method and device |
| CN114513250A (en) * | 2021-12-31 | 2022-05-17 | 北京交通大学 | Instantaneous frequency measurement system and method based on differential optical time stretching principle |
| CN114513250B (en) * | 2021-12-31 | 2023-11-07 | 北京交通大学 | Instantaneous frequency measurement system and method based on differential optical time stretching principle |
Also Published As
| Publication number | Publication date |
|---|---|
| CN111277325B (en) | 2021-05-04 |
Similar Documents
| Publication | Publication Date | Title |
|---|---|---|
| CN111277325B (en) | Instantaneous frequency measurement method and system with adjustable measurement range based on polarization modulator | |
| US9923631B1 (en) | Optical signal processing characterization of microwave and electro-optic devices | |
| CN107085143B (en) | A kind of photoelectricity frequency sound test instrument and test method | |
| CN110017967B (en) | Phase comparison-based chirp parameter testing method for electro-optic intensity modulator | |
| CN110632388B (en) | Frequency mixing-based photoelectric detector frequency response measuring method and device | |
| CN102281107A (en) | Dispersion measuring device and method for fiber optical device | |
| CN104020334B (en) | A kind of electro-optic phase modulator half-wave voltage measuring system and measuring method | |
| CN108844614B (en) | Chaotic Brillouin optical correlation domain analysis system and method based on phase spectrum measurement | |
| CN109186643B (en) | Accurate sensing system and sensing method based on reflection function resonant filter | |
| CN102914423B (en) | Measuring method for sag frequency of dispersion optical fiber | |
| CN103414513B (en) | A kind of pulsed light dynamic extinction ratio measurement mechanism and method with high dynamic range | |
| CN107976300B (en) | Method for measuring beat length of polarization maintaining optical fiber | |
| CN111751845B (en) | Laser radar frequency locking device and method for gas detection | |
| CN107356412B (en) | A kind of measurement method of the measuring system based on rare-earth doped optical fibre refractive index | |
| CN109831249A (en) | A kind of measuring device of polarization maintaining optical fibre main shaft difference delay | |
| CN111464241B (en) | Measurement system and measurement method for improving precision of arrival angle of microwave signal | |
| CN113541780A (en) | Instantaneous frequency measuring device based on optical power monitoring | |
| CN107806981B (en) | Measuring device for beat length of polarization maintaining optical fiber | |
| CN106936498B (en) | A kind of signal analysis method based on ultra wide band phase noise measuring system | |
| CN201830267U (en) | Photon type digital microwave frequency measuring device adopting phase shift comb type filter array | |
| CN112816180A (en) | Optical fiber dispersion measuring method and measuring device | |
| CN101977086B (en) | Photon type digital microwave frequency measuring method and device adopting phase-shift comb filtering array | |
| Zhu et al. | Switchable instantaneous frequency measurement by optical power monitoring based on DP-QPSK modulator | |
| CN106771689B (en) | A kind of ultra wide band phase noise measuring system | |
| CN114978307B (en) | Single-branch detection instantaneous frequency measurement system based on polarization-maintaining fiber birefringence effect |
Legal Events
| Date | Code | Title | Description |
|---|---|---|---|
| PB01 | Publication | ||
| PB01 | Publication | ||
| SE01 | Entry into force of request for substantive examination | ||
| SE01 | Entry into force of request for substantive examination | ||
| GR01 | Patent grant | ||
| GR01 | Patent grant | ||
| CF01 | Termination of patent right due to non-payment of annual fee |
Granted publication date: 20210504 Termination date: 20220120 |
|
| CF01 | Termination of patent right due to non-payment of annual fee |