WO2021082377A1 - 一种基于相推法的光器件时延测量方法及装置 - Google Patents

一种基于相推法的光器件时延测量方法及装置 Download PDF

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WO2021082377A1
WO2021082377A1 PCT/CN2020/087447 CN2020087447W WO2021082377A1 WO 2021082377 A1 WO2021082377 A1 WO 2021082377A1 CN 2020087447 W CN2020087447 W CN 2020087447W WO 2021082377 A1 WO2021082377 A1 WO 2021082377A1
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phase
time delay
optical device
frequency
sweep
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PCT/CN2020/087447
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潘时龙
李树鹏
卿婷
傅剑斌
潘万胜
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南京航空航天大学
苏州六幺四信息科技有限责任公司
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    • G—PHYSICS
    • G01—MEASURING; TESTING
    • G01M—TESTING STATIC OR DYNAMIC BALANCE OF MACHINES OR STRUCTURES; TESTING OF STRUCTURES OR APPARATUS, NOT OTHERWISE PROVIDED FOR
    • G01M11/00—Testing of optical apparatus; Testing structures by optical methods not otherwise provided for
    • G01M11/02—Testing optical properties

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  • the invention relates to a method for measuring the time delay of an optical device, in particular to a method and a device for measuring the time delay of an optical device based on a phase inference method.
  • optical device time delay measurement methods mainly include pulse method, frequency scanning interferometry and phase inference method.
  • the pulse method calculates the time delay of the optical device under test by observing the time interval between the transmitted light pulse and the received light pulse. Because the dispersion of the optical device will expand the optical pulse and deteriorate the measurement accuracy, the pulse method is not suitable for the dispersion of long optical fibers. Larger optical devices make accurate measurements. In addition, the narrow pulse has a wide frequency spectrum. When measuring optical devices with a small passband range, they cannot pass all of them, thereby deteriorating the measurement accuracy (for example: ultra-dense wavelength division multiplexer, optically controlled delay chip, etc.).
  • Frequency scanning interferometry requires the use of a continuous frequency sweep laser, which is expensive, and is limited by the line width and frequency sweep linearity of this laser. Its measurement range is small, generally on the order of kilometers (10 microseconds), and its measurement accuracy As the time delay of the optical device increases, it decreases significantly. In addition, the frequency scanning interferometry essentially trades a large bandwidth for high measurement accuracy, so when measuring optical devices with a small passband range, the measurement accuracy will decrease.
  • the phase inference method uses phase changes to estimate the time delay of the optical device, which has high accuracy and can avoid the problem of a large amount of time delay deteriorating accuracy.
  • the existing phase extrapolation method requires fine frequency scanning when measuring large time delays, the number of scanning frequency points increases sharply, the measurement time is greatly lengthened, and environmental errors are easily introduced.
  • the traditional phase extrapolation method uses an optical vector analyzer to measure the phase response of the optical device, and then calculate the time delay response of the optical device.
  • high time delay measurement accuracy requires an extremely wide frequency sweep range, which requires high measuring instruments, is expensive, and is susceptible to chromatic dispersion.
  • Li Shupeng et al. SPLi, XCWang, T. Qing, SFLiu, JBFu, M.
  • the signal is linearly swept to obtain a series of phase changes, and from this, the fiber delay is calculated. Due to the small frequency sweep range, it not only reduces the requirements on the device, avoids the influence of chromatic dispersion, but is also suitable for measuring optical devices with a small passband range, and the range of types of optical devices that can be measured is large. However, since the frequency interval of the sweep determines the time delay of the optical device that can be measured, when measuring a large time delay, a smaller frequency interval is required, and the frequency range remains unchanged, then the number of frequency points scanned will increase sharply. As the measurement time increases, not only the measurement efficiency is low, but also environmental errors are introduced.
  • the technical problem to be solved by the present invention is to overcome the shortcomings of the existing phase extrapolation optical device time delay measurement technology, and provide a phase extrapolation-based optical device time delay measurement method, which can greatly reduce the number of scanning frequency points, thereby improving the measurement efficiency And reduce the impact of environmental errors on the measurement.
  • a method for measuring the time delay of an optical device based on the phase extrapolation method The sweep frequency range is determined in advance according to the measurement requirements and multiple sweep frequency points are selected in it; at each sweep frequency point, the microwave modulated signal of this frequency is used for the optical carrier Carry out modulation, and measure the phase change of the microwave modulation signal before and after the modulated optical signal passes through the optical device under test through the phase detector; perform phase unwrapping on a series of measured phase changes, and use the sweep frequency points obtained by the phase unwrapping Calculate the ambiguity of the maximum sweep frequency point in the unfolding phase, and finally calculate the time delay of the optical device under test according to the ambiguity of the maximum sweep frequency point; the selected minimum sweep frequency point frequency ⁇ a , maximum The sweep frequency point frequency ⁇ b , the number of sweep frequency points m, and the frequency ⁇ i of each sweep frequency point are as follows:
  • ⁇ is the phase accuracy of the phase detector
  • ⁇ is the target accuracy of the time delay measurement
  • ⁇ 0 is the time delay of the measurement system
  • ⁇ max is the maximum measurable time delay
  • ⁇ is the value range (0,1) The correction factor.
  • the method of phase unwrapping is specifically as follows:
  • the unfolded phase ⁇ ( ⁇ 2 ) of the sweep frequency point ⁇ 2 is obtained by the classical phase unwrapping algorithm, and the unfolded phases of the other sweep frequency points are obtained by the following formula:
  • the whole-cycle ambiguity N b of the maximum sweep frequency point is obtained according to the following formula:
  • the value range of the correction coefficient ⁇ is [0.80, 0.99].
  • the calculation of the time delay of the optical device under test according to the ambiguity of the whole circumference of the maximum frequency sweep frequency point is specifically based on the following formula:
  • ⁇ D is the time delay of the optical device to be measured
  • N b is the ambiguity of the whole cycle of the maximum frequency sweep point.
  • An optical device time delay measurement device based on phase inference method including:
  • the frequency point determination unit is used to determine the sweep frequency range according to the measurement requirements in advance and select multiple sweep frequency points in it;
  • the phase measurement unit is used to perform the microwave modulation signal on the optical carrier at each sweep frequency point Modulate, and measure the phase change of the microwave modulated signal before and after the modulated optical signal passes through the optical device under test through the phase detector;
  • the solving unit is used to perform phase unwrapping on a series of measured phase changes, and use the unwrapped phases of each sweep frequency point obtained by the phase unwrapping to calculate the whole cycle ambiguity of the maximum sweep frequency point, and finally according to the maximum Calculate the time delay of the optical device under test by sweeping the ambiguity of the whole circle of the frequency sweep;
  • the minimum sweep frequency point frequency ⁇ a , the maximum sweep frequency point frequency ⁇ b , the number of sweep frequency points m and the frequency ⁇ i of each sweep frequency point selected by the frequency point determination unit are as follows:
  • ⁇ is the phase accuracy of the phase detector
  • ⁇ is the target accuracy of the time delay measurement
  • ⁇ 0 is the time delay of the measurement system
  • ⁇ max is the maximum measurable time delay
  • ⁇ is the value range (0,1) The correction factor.
  • the method of phase unwrapping is specifically as follows:
  • the unfolded phase ⁇ ( ⁇ 2 ) of the sweep frequency point ⁇ 2 is obtained by the classical phase unwrapping algorithm, and the unfolded phases of the other sweep frequency points are obtained by the following formula:
  • the whole-cycle ambiguity N b of the maximum sweep frequency point is obtained according to the following formula:
  • the value range of the correction coefficient ⁇ is [0.80, 0.99].
  • the calculation of the time delay of the optical device to be measured according to the ambiguity of the entire circumference of the maximum sweep frequency point is specifically based on the following formula:
  • ⁇ D is the time delay of the optical device to be measured
  • N b is the ambiguity of the whole cycle of the maximum frequency sweep point.
  • the present invention improves the existing high-precision optical device time delay measurement technology based on the phase extrapolation method. It adopts nonlinear frequency sweep, and the frequency interval increases exponentially. In the same scanning range, compared with the existing linear frequency sweep In this way, the number of frequency points that need to be scanned by this method is less, and the scanning time is greatly reduced; in addition, because the scanning frequency points are greatly reduced, the requirements for the microwave frequency scanning source are also greatly reduced, and the introduction of environmental errors is reduced, and the measurement accuracy is improved.
  • the measurement efficiency is low and the environmental noise is easily introduced due to the excessive number of scanning frequency points.
  • the solution of the present invention is to abandon the traditional linear scanning method and switch to With nonlinear frequency sweeping, the frequency interval increases exponentially. In this way, within the same scanning range, the number of frequency points that need to be scanned and the scanning time are greatly reduced; in addition, because the scanning frequency points are greatly reduced, the requirements for the microwave frequency scanning source are also greatly reduced, and the introduction of environmental errors is reduced, and the measurement accuracy.
  • the laser source sends a beam of light carrier to the MZM modulator
  • the bias point controller controls the bias point of the MZM modulator to be located at the linear point
  • Load the microwave signal output by the microwave source to the RF input port of the MZM modulator, and the generated probe light signal can be expressed as:
  • A is the optical field amplitude
  • ⁇ e and ⁇ c are the angular frequencies of the microwave signal and the optical carrier respectively
  • M is the amplitude modulation coefficient
  • ⁇ 0 is the total transmission time of the probe light in the measurement system
  • ⁇ D is the total transmission time of the probe light in the optical device under test.
  • ⁇ is the photoelectric conversion coefficient. It can be seen from formula (3) that the phase change of the microwave signal with frequency ⁇ e can be expressed as:
  • phase change of the microwave signal with a frequency of ⁇ e obtained by the phase detector can be expressed as:
  • n is an integer, and is generally called the ambiguity of the frequency ⁇ e.
  • the existing phase extrapolation method uses linear frequency sweep to solve the whole-cycle ambiguity.
  • First determine the frequency sweep interval [ ⁇ a , ⁇ b ], the starting frequency ⁇ a and the ending frequency ⁇ b can be determined by the following formula:
  • ⁇ is the phase accuracy of the phase detector
  • ⁇ is the required measurement accuracy of the optical device time delay.
  • the frequency sweep interval determined by this method is small, so it can be used not only to measure optical fibers, but also to measure optical devices with a small passband range such as optical chips.
  • the existing phase extrapolation method needs to use the classic phase unwrapping algorithm, so its sweep frequency step ⁇ needs to meet Among them, m is the number of frequency sweep points, ⁇ 0 is the system delay, which can be obtained by calibration, and ⁇ max is the maximum measurable delay. From this, the number of frequency points that need to be swept is:
  • the unfolded phase response changes linearly with frequency
  • c is the speed of light in vacuum
  • n 0 is the refractive index of the optical fiber (can be found in the manual provided by the optical fiber manufacturer). If it is a reflection measurement, it needs to be divided by two.
  • This measurement method is limited by the classic phase unwrapping algorithm.
  • the number of frequency sweep points increases linearly with the increase of the maximum measurable delay.
  • the measurement speed is slow. For example: to measure a kilometer-level optical fiber with a measurement accuracy of 0.1 mm, thousands of frequency points need to be scanned.
  • the present invention uses nonlinear frequency scanning, and the frequency difference between the subsequent frequency and the initial frequency increases exponentially.
  • the specific method for determining the frequency of the sweep is as follows. First determine the start frequency ⁇ a and the stop frequency ⁇ b :
  • the correction coefficient ⁇ (0,1] which is an empirical value, depends on the stability of the system, and its preferred value range is [0.80,0.99]. Then determine the number of sweep points:
  • the present invention can determine each scanning frequency, scan each frequency point in turn, and obtain the corresponding phase response ⁇ ( ⁇ 1 ), ⁇ ( ⁇ 2 )... ⁇ ( ⁇ m ). Due to the non-linear frequency sweep, the frequency sweep step increases exponentially, so the number of required frequency points is greatly reduced, and the measurement speed can be greatly improved.
  • the corresponding time delay calculation algorithm is as follows:
  • the invention can directly adopt the hardware part of the existing high-precision optical device time delay measurement system based on the phase inference method, and can be realized by simply modifying the software part.

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Abstract

一种基于相推法的光器件时延测量方法，预先根据测量需求确定扫频频率范围并在其中选取多个扫频频点；在每一个扫频频点，用该频率的微波调制信号对光载波进行调制，并通过鉴相器测量出调制光信号经过待测光器件前后微波调制信号的相位变化；对所测得的一系列相位变化进行相位展开，并利用相位展开所得到的各扫频频点的展开相位计算出最大扫频频点的整周模糊度，最后根据最大扫频频点的整周模糊度计算出待测光器件的时延。还公开了一种基于相推法的光器件时延测量装置。本方法及装置可大幅度减少扫描频点数，从而提高测量效率并减少环境误差对测量的影响。

Description

一种基于相推法的光器件时延测量方法及装置 技术领域
本发明涉及一种光器件时延测量方法，尤其涉及一种基于相推法的光器件时延测量方法及装置。
背景技术
常用的光器件时延测量方法主要有脉冲法、频率扫描干涉法和相推法三种。脉冲法通过观测发射光脉冲与接收光脉冲的时间间隔计算出被测光器件的时延，由于光器件色散会对光脉冲进行展宽，恶化测量精度，因此脉冲法不适合对长光纤等色散量较大的光器件进行精确测量。此外，窄脉冲的频谱范围较宽，在测量通带范围较小的光器件时，无法全部通过，进而恶化测量精度(例如：超密集波分复用器、光控时延芯片等)。脉冲法存在着许多不可避免的误差，如仪器分辨力误差、光器件色散误差等。因此脉冲法的测量精度只是米量级，且随着光器件时延的增加，测量误差也随着增大。频率扫描干涉法需要使用连续扫频激光器，价格昂贵，而且受限于这种激光器的线宽跟扫频线性度，其测量范围较小，一般为公里(10微秒)量级，而且测量精度随着光器件时延的增大而明显减小。此外，频率扫描干涉法本质上是以大带宽换取高测量精度，所以在测量通带范围小的光器件时，测量精度会下降。相推法由于使用相位变化来推算光器件时延，精度较高，且可以规避大时延量恶化精度的问题。但是现有相推法在测量大时延的时候，需要精细的频率扫描，扫描频点数激增，测量时间大大加长，容易引入环境误差。
传统相推法使用光矢量分析仪测量光器件的相位响应，进而算出光器件时延响应。然而较高的时延测量精度需要极宽的扫频范围，对测量仪器要求较高，价格昂贵，且容易受到色散的影响。为克服这一问题，2019年李树鹏等人(S.P.Li,X.C.Wang,T.Qing,S.F.Liu,J.B.Fu,M.Xue,S.L.Pan,"Optical Fiber Transfer Delay Measurement Based on Phase-Derived Ranging,"IEEE Photonics Technology Letters,vol.31,no.16,pp.1351-1354,Aug.2019.)提出的基于相推法的高精度光纤时延测量系统，通过对窄线宽光源进行外调制，调制后的光信号通过环形器进入被测光纤，反射光经过光电转换之后通过鉴相器得到调制信号在待测光纤中经历的相位变化，再以固定的频率间隔在较小的一段频率范 围内对调制信号进行线性扫频，得到一系列的相位变化，并由此推算出光纤时延。由于扫频范围小，不仅降低了对器件的要求，避免了色散的影响而且适用于测量通带范围小的光器件，可测光器件的种类范围较大。但是由于扫频的频率间隔决定了能测量的光器件时延，所以测量大时延的时候，需要较小的频率间隔，而频率范围不变，那么扫描的频点数就会激增，所需要的测量时间随之增长，不仅测量效率低，还会引入环境误差。
发明内容
本发明所要解决的技术问题在于克服现有相推法光器件时延测量技术的不足，提供一种基于相推法的光器件时延测量方法，可大幅度减少扫描频点数，从而提高测量效率并减少环境误差对测量的影响。
本发明具体采用以下技术方案解决上述技术问题：
一种基于相推法的光器件时延测量方法，预先根据测量需求确定扫频频率范围并在其中选取多个扫频频点；在每一个扫频频点，用该频率的微波调制信号对光载波进行调制，并通过鉴相器测量出调制光信号经过待测光器件前后微波调制信号的相位变化；对所测得的一系列相位变化进行相位展开，并利用相位展开所得到的各扫频频点的展开相位计算出最大扫频频点的整周模糊度，最后根据所述最大扫频频点的整周模糊度计算出待测光器件的时延；所选取的最小扫频频点频率ω a、最大扫频频点频率ω b、扫频频点数量m以及各扫频频点的频率ω i具体如下：
Figure PCTCN2020087447-appb-000001
Figure PCTCN2020087447-appb-000002
Figure PCTCN2020087447-appb-000003
Figure PCTCN2020087447-appb-000004
其中，Δθ为所述鉴相器的相位精度，Δτ为时延测量目标精度，τ 0为测量系统的时延，τ max为最大可测时延，λ为取值范围为(0,1]的修正系数。
优选地，所述相位展开的方法具体如下：
扫频频点ω 2的展开相位φ(ω 2)通过经典相位展开算法得到，其余扫频频点的展开相位通过下式得到：
Figure PCTCN2020087447-appb-000005
其中，[…]为取整符号，表示对其中的数据进行“四舍五入”取整。
优选地，最大扫频频点的整周模糊度N b按照下式得到：
Figure PCTCN2020087447-appb-000006
其中，[…]为取整符号，表示对其中的数据进行“四舍五入”取整。
优选地，所述修正系数λ的取值范围为[0.80,0.99]。
优选地，所述根据最大扫频频点的整周模糊度计算出待测光器件时延，具体根据以下公式：
Figure PCTCN2020087447-appb-000007
其中，τ D为待测光器件的时延，N b为最大扫频频点的整周模糊度。
根据相同的发明思路还可以得到以下技术方案：
一种基于相推法的光器件时延测量装置，包括：
频点确定单元，用于预先根据测量需求确定扫频频率范围并在其中选取多个扫频频点；相位测量单元，用于在每一个扫频频点，用该频率的微波调制信号对光载波进行调制，并通过鉴相器测量出调制光信号经过待测光器件前后微波调制信号的相位变化；
解算单元，用于对所测得的一系列相位变化进行相位展开，并利用相位展开所得到的各扫频频点的展开相位计算出最大扫频频点的整周模糊度，最后根据所述最大扫频频点的整周模糊度计算出待测光器件的时延；
频点确定单元所选取的最小扫频频点频率ω a、最大扫频频点频率ω b、扫频频点数量m以及各扫频频点的频率ω i具体如下：
Figure PCTCN2020087447-appb-000008
Figure PCTCN2020087447-appb-000009
Figure PCTCN2020087447-appb-000010
Figure PCTCN2020087447-appb-000011
其中，Δθ为所述鉴相器的相位精度，Δτ为时延测量目标精度，τ 0为测量系统的时延，τ max为最大可测时延，λ为取值范围为(0,1]的修正系数。
优选地，所述相位展开的方法具体如下：
扫频频点ω 2的展开相位φ(ω 2)通过经典相位展开算法得到，其余扫频频点的展开相位通过下式得到：
Figure PCTCN2020087447-appb-000012
其中，[…]为取整符号，表示对其中的数据进行“四舍五入”取整。
优选地，最大扫频频点的整周模糊度N b按照下式得到：
Figure PCTCN2020087447-appb-000013
其中，[…]为取整符号，表示对其中的数据进行“四舍五入”取整。
优选地，所述修正系数λ的取值范围为[0.80,0.99]。
优选地，所述根据最大扫频频点的整周模糊度计算出待测光器件的时延，具体根据以下公式：
Figure PCTCN2020087447-appb-000014
其中，τ D为待测光器件的时延，N b为最大扫频频点的整周模糊度。
相比现有技术，本发明技术方案具有以下有益效果：
本发明对现有基于相推法的高精度光器件时延测量技术进行改进，采用非线性扫 频，频率间隔按照指数级递增，在相同的扫描范围内，相比于现有的线性扫频方式，本方法需要扫描的频点数较少，扫描时间大大减少；此外，由于扫描频点大幅减少，对微波扫频源的要求也大幅降低，同时减少了环境误差的引入，提高了测量精度。
具体实施方式
针对现有基于相推法的高精度光器件时延测量技术由于扫描频点数过多所导致的测量效率低且易引入环境噪声的不足，本发明的解决思路是摈弃传统的线性扫描方式，转而采用非线性扫频，频率间隔按照指数级递增。这样，在相同的扫描范围内，需要扫描的频点数和扫描时间大大减少；此外，由于扫描频点大幅减少，对微波扫频源的要求也大幅降低，同时减少了环境误差的引入，提高了测量精度。
为便于公众理解，在对本发明技术方案进行详细说明之前，先对现有基于相推法的高精度光器件时延测量技术的基本原理进行介绍。
以(S.P.Li,X.C.Wang,T.Qing,S.F.Liu,J.B.Fu,M.Xue,S.L.Pan,"Optical Fiber Transfer Delay Measurement Based on Phase-Derived Ranging,"IEEE Photonics Technology Letters,vol.31,no.16,pp.1351-1354,Aug.2019.)中的测量系统为例，激光源发出一束光载波到MZM调制器，偏置点控制器控制MZM调制器的偏置点位于线性点，再将微波源输出的微波信号加载到MZM调制器的RF输入口，所产生的探测光信号均可表示为：
E o(t)＝A(1+M cos(ω et))exp(jω ct)    (1)
其中，A是光场幅度，ω e和ω c分别是微波信号和光载波的角频率，M是调幅系数。探测光经过光环形器到待测光器件传输后到达高灵敏度光电探测模块，此时的光场可表示为：
E r(t)＝A(1+M cos(ω e(t-τ 0-τ D)))exp(jω c(t-τ 0-τ D))   (2)
其中，τ 0是探测光在测量系统中的总传输时间，τ D是探测光在待测光器件中的总传输时间。返回的探测光经过光电转换后，通过滤波器提取出一倍频信号，其电场可表示为：
i(t)＝2ηMA 2cos(ω e(t-τ 0-τ D))   (3)
其中，η为光电转换系数。从公式(3)可以看出，频率为ω e的微波信号的相位变 化可表示为：
Figure PCTCN2020087447-appb-000015
由于鉴相器测得的相位范围一般为-π到π，因此鉴相器得到的频率为ω e的微波信号的相位变化可表示为：
Figure PCTCN2020087447-appb-000016
其中，n为整数,一般也叫做频率ω e的整周模糊度。
现有的相推法通过线性扫频来解算整周模糊度。首先确定扫频区间[ω a,ω b]，起始频率ω a和终止频率ω b可由如下公式确定：
Figure PCTCN2020087447-appb-000017
其中，Δθ为鉴相器的相位精度，Δτ为所需要的光器件时延的测量精度。利用这种方法确定的扫频区间较小，所以不仅可以用来测量光纤也可以用于测量光芯片等通带范围较小的光器件。不过现有的相推法需要使用经典相位展开算法，所以它扫频的频率步进Δω需要满足
Figure PCTCN2020087447-appb-000018
其中，m为扫频点数，τ 0为系统时延，可由校准得到，τ max为最大可测时延，由此，可以得到需要扫频的频点数为：
Figure PCTCN2020087447-appb-000019
其中，[…]为取整符号，此处为“进一法”取整，即：去掉数值的小数部分再加一，如果数值本身是整数则不变。由此，可以得到需要扫描的各个频率点：
Figure PCTCN2020087447-appb-000020
依次扫描各个频点，可以得到相应的相位响应θ(ω 1)，θ(ω 2)…θ(ω m)。再通过经典相位展开算法得到展开的相位响应，可以用MATLAB的unwrap函数来实现。这种经典相位展开算法的描述如下：判断相邻两个频点测得的相位差的绝对值是否大于等于π，如果满足，就将后一个频率点的相位加上或者减去一个2π，使得相邻频点测得的相位差的绝对值小于π。展开的相位响应随频率呈线性变化，可利用最小二乘法线性拟合得到展开的相位响应随频率变化的线性函数φ(ω i)＝k·ω i+b，再将拟合得到的斜率k用于解算ω b的整周模糊度：
Figure PCTCN2020087447-appb-000021
其中，[…]为取整运算符，此处为“四舍五入”取整，如果数值是负数，则先取绝对值，再“四舍五入”后加上负号。最后，结合公式(4)、(5)可得待测光器件的时延为：
Figure PCTCN2020087447-appb-000022
在测量光纤这种传输介质时，其长度可以通过下式计算：
Figure PCTCN2020087447-appb-000023
其中，c为真空中光速，n 0为光纤折射率(可由光纤生产厂商提供的手册中查询得到)。如果是反射式测量，还需要除以二。
这种测量方法受限于经典相位展开算法，其扫频点数随着最大可测时延的增大呈线性增长，在测量大时延的时候，测量速度较慢。例如：测量一段公里级别长度的光纤，测量精度为0.1毫米的话，需要扫描成千上万个频点。
与该方法不同，本发明使用非线性频率扫描，后续频率与起始频率的频差呈指数级上升，具体的扫频频率确定方法如下。首先确定起始频率ω a和终止频率ω b：
Figure PCTCN2020087447-appb-000024
其中，修正系数λ∈(0,1]，这是一个经验值，视系统稳定性而定，其优选的取值范围为[0.80,0.99]。接着确定扫频点数：
Figure PCTCN2020087447-appb-000025
其中，[…]为取整符号，此处为“进一法”取整。最后确定起始频率ω 1＝ω a与终止频率ω m＝ω b之间的频率：
Figure PCTCN2020087447-appb-000026
至此，本发明可以确定好各个扫描频率，依次扫描各个频点，可以得到相应的相位响应θ(ω 1)，θ(ω 2)…θ(ω m)。由于采用非线性扫频，扫频步进呈指数级上升，所以需要的频点数量大大减少，测量速度可获得较大的提升，其相应的时延解算算法如下：
首先，利用经典相位展开算法计算出第二个频点的展开相位φ(ω 2)，再按照如下公式计算出剩余频点的展开相位：
Figure PCTCN2020087447-appb-000027
其中，[…]为取整符号，此处为“四舍五入”取整。由此可解算出终止频率的整周模糊度：
Figure PCTCN2020087447-appb-000028
其中，[…]为取整运算符，此处为“四舍五入”取整。最后，可由公式(10)得到待测光器件的时延。测量光纤时，可由公式(11)计算出长度。
本发明可直接采用现有基于相推法的高精度光器件时延测量系统的硬件部分，只需要对软件部分进行简单修改即可实现。

Claims (10)

  1. 一种基于相推法的光器件时延测量方法，预先根据测量需求确定扫频频率范围并在其中选取多个扫频频点；在每一个扫频频点，用该频率的微波调制信号对光载波进行调制，并通过鉴相器测量出调制光信号经过待测光器件前后微波调制信号的相位变化；对所测得的一系列相位变化进行相位展开，并利用相位展开所得到的各扫频频点的展开相位计算出最大扫频频点的整周模糊度，最后根据所述最大扫频频点的整周模糊度计算出待测光器件的时延；其特征在于，所选取的最小扫频频点频率ω a、最大扫频频点频率ω b、扫频频点数量m以及各扫频频点的频率ω i具体如下：
    Figure PCTCN2020087447-appb-100001
    Figure PCTCN2020087447-appb-100002
    Figure PCTCN2020087447-appb-100003
    Figure PCTCN2020087447-appb-100004
    其中，Δθ为所述鉴相器的相位精度，Δτ为时延测量目标精度，τ 0为测量系统的时延，τ max为最大可测时延，λ为取值范围为(0,1]的修正系数。
  2. 如权利要求1所述光器件时延测量方法，其特征在于，所述相位展开的方法具体如下：
    扫频频点ω 2的展开相位φ(ω 2)通过经典相位展开算法得到，其余扫频频点的展开相位通过下式得到：
    Figure PCTCN2020087447-appb-100005
    其中，[…]为取整符号，表示对其中的数据进行“四舍五入”取整。
  3. 如权利要求1所述光器件时延测量方法，其特征在于，最大扫频频点的整周模糊度N b按照下式得到：
    Figure PCTCN2020087447-appb-100006
    其中，[…]为取整符号，表示对其中的数据进行“四舍五入”取整。
  4. 如权利要求1所述光器件时延测量方法，其特征在于，所述修正系数λ的取值范围为[0.80,0.99]。
  5. 如权利要求1所述光器件时延测量方法，其特征在于，所述根据最大扫频频点的整周模糊度计算出待测光器件的时延，具体根据以下公式：
    Figure PCTCN2020087447-appb-100007
    其中，τ D为待测光器件的时延，N b为最大扫频频点的整周模糊度。
  6. 一种基于相推法的光器件时延测量装置，包括：
    频点确定单元，用于预先根据测量需求确定扫频频率范围并在其中选取多个扫频频点；相位测量单元，用于在每一个扫频频点，用该频率的微波调制信号对光载波进行调制，并通过鉴相器测量出调制光信号经过待测光器件前后微波调制信号的相位变化；
    解算单元，用于对所测得的一系列相位变化进行相位展开，并利用相位展开所得到的各扫频频点的展开相位计算出最大扫频频点的整周模糊度，最后根据所述最大扫频频点的整周模糊度计算出待测光器件的时延；
    其特征在于，频点确定单元所选取的最小扫频频点频率ω a、最大扫频频点频率ω b、扫频频点数量m以及各扫频频点的频率ω i具体如下：
    Figure PCTCN2020087447-appb-100008
    Figure PCTCN2020087447-appb-100009
    Figure PCTCN2020087447-appb-100010
    Figure PCTCN2020087447-appb-100011
    其中，Δθ为所述鉴相器的相位精度，Δτ为时延测量目标精度，τ 0为测量系统的时 延，τ max为最大可测时延，λ为取值范围为(0,1]的修正系数。
  7. 如权利要求6所述光器件时延测量装置，其特征在于，所述相位展开的方法具体如下：
    扫频频点ω 2的展开相位φ(ω 2)通过经典相位展开算法得到，其余扫频频点的展开相位通过下式得到：
    Figure PCTCN2020087447-appb-100012
    其中，[…]为取整符号，表示对其中的数据进行“四舍五入”取整。
  8. 如权利要求6所述光器件时延测量装置，其特征在于，最大扫频频点的整周模糊度N b按照下式得到：
    Figure PCTCN2020087447-appb-100013
    其中，[…]为取整符号，表示对其中的数据进行“四舍五入”取整。
  9. 如权利要求6所述光器件时延测量装置，其特征在于，所述修正系数λ的取值范围为[0.80,0.99]。
  10. 如权利要求6所述光器件时延测量装置，其特征在于，所述根据最大扫频频点的整周模糊度计算出待测光器件的时延，具体根据以下公式：
    Figure PCTCN2020087447-appb-100014
    其中，τ D为待测光器件的时延，N b为最大扫频频点的整周模糊度。
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