WO2023088421A1 - 探测带宽大于1THz的光信号实时矢量分析方法及装置 - Google Patents

探测带宽大于1THz的光信号实时矢量分析方法及装置 Download PDF

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WO2023088421A1
WO2023088421A1 PCT/CN2022/132832 CN2022132832W WO2023088421A1 WO 2023088421 A1 WO2023088421 A1 WO 2023088421A1 CN 2022132832 W CN2022132832 W CN 2022132832W WO 2023088421 A1 WO2023088421 A1 WO 2023088421A1
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time
signal
domain
optical
real
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French (fr)
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张驰
张新亮
李仑
蔡宇翀
李耀帅
刘辰
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华中科技大学
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    • 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
    • H04B10/60—Receivers
    • H04B10/61—Coherent receivers
    • H04B10/64—Heterodyne, i.e. coherent receivers where, after the opto-electronic conversion, an electrical signal at an intermediate frequency [IF] is obtained
    • 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
    • H04B10/60—Receivers
    • H04B10/61—Coherent receivers
    • G—PHYSICS
    • G01—MEASURING; TESTING
    • G01J—MEASUREMENT OF INTENSITY, VELOCITY, SPECTRAL CONTENT, POLARISATION, PHASE OR PULSE CHARACTERISTICS OF INFRARED, VISIBLE OR ULTRAVIOLET LIGHT; COLORIMETRY; RADIATION PYROMETRY
    • G01J1/00—Photometry, e.g. photographic exposure meter
    • G01J1/42—Photometry, e.g. photographic exposure meter using electric radiation detectors
    • G—PHYSICS
    • G01—MEASURING; TESTING
    • G01J—MEASUREMENT OF INTENSITY, VELOCITY, SPECTRAL CONTENT, POLARISATION, PHASE OR PULSE CHARACTERISTICS OF INFRARED, VISIBLE OR ULTRAVIOLET LIGHT; COLORIMETRY; RADIATION PYROMETRY
    • G01J9/00—Measuring optical phase difference; Determining degree of coherence; Measuring optical wavelength
    • 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
    • H04B10/073—Arrangements for monitoring or testing transmission systems; Arrangements for fault measurement of transmission systems using an out-of-service signal
    • H04B10/0731—Testing or characterisation of optical devices, e.g. amplifiers
    • 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
    • H04B10/25—Arrangements specific to fibre transmission
    • 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
    • H04B10/60—Receivers
    • H04B10/61—Coherent receivers
    • H04B10/615—Arrangements affecting the optical part of the receiver
    • H04B10/6151—Arrangements affecting the optical part of the receiver comprising a polarization controller at the receiver's input stage

Definitions

  • the invention relates to the technical field of real-time measurement of optical signals with a bandwidth greater than 1 THz, in particular to simultaneous real-time acquisition and analysis of intensity and phase information of signals with a bandwidth greater than 1 THz.
  • the two-dimensional time-frequency distribution map is obtained, and then the intensity and phase information of the pulse can be extracted by using the two-dimensional phase reconstruction iterative algorithm (D.J.Kane and R.Trebino.Single-shot measurement of the intensity and phase of an Arbitrary ultrashort pulse by using frequency-resolved optical gating. Optics Letters, 1993, vol.18, no.10, 823-825).
  • the measurement time window range is usually only tens of picoseconds, and the measurement frame rate is also very limited, so real-time ultra-fast measurement cannot be achieved.
  • Time-domain lens magnification technology is another way to measure high-speed signals.
  • One of its original intentions is to solve the difficulty in detecting high-speed optical waveforms due to limited detection bandwidth. Similar to a space lens magnification system.
  • the input signal can be amplified by passing through the time-domain imaging system.
  • the signal to be measured is stretched in the time domain by the first dispersive device, it passes through the time domain lens system, and then continues to stretch through the second dispersive unit.
  • the second chromatic dispersion is N of the first chromatic dispersion.
  • the final output signal time window is N times the time window of the signal to be tested, which reduces the detection bandwidth and analog-to-digital conversion bandwidth of the system to collect the signal to be tested by N times.
  • the high-speed signal is amplified in the time domain, which is equivalent to slowing down, and then it can be collected and observed with a low-speed real-time sampling system (R Salem et al. Optical time lens based on four-wave mixing on a silicon chip. Optics Letters, 2008, vol.33, no.10 1047-1049).
  • the system magnification is equal to the ratio of the output dispersion to the input dispersion.
  • the system measurement time window is determined by the size of the front pump dispersion, which is limited by the magnification and the dispersion amount.
  • the measurement time range is usually 200ps.
  • the effective multiplication of the measurement time window can be realized by using the delay buffer ring technology combined with the time domain amplification method.
  • the time-domain segmentation method effectively improves the range of the signal time window, but the frame rate of the measurement is restricted, and at the same time, only the intensity information of the optical signal that changes with time is obtained, and the phase change information of the other dimension is lost.
  • time-domain optics to realize ultrafast waveform measurement is the Fourier transform in the time domain, which avoids the bandwidth-limited problem of time-domain detection by converting the time-domain waveform to the spectrum for measurement.
  • the way to realize the time-domain Fourier transform is mainly based on the method of time-domain lens, and its realization method is usually based on nonlinear parametric processes such as electro-optical phase modulator and four-wave mixing.
  • the second phase modulation is loaded on the time domain through the time domain lens, and finally the mapping of the time domain information of the signal to be measured to the frequency domain is realized through the output dispersion.
  • the magnitude of the output light field spectrum is the mapping of the output light field in the time domain (M.Foster et al.Silicon-chip-based ultrafast optical oscillator.Nature,2008,vol.456,no.7218 ,81-84).
  • the time window of this method is limited by the window size of the time-domain lens, and it can only realize the characterization of a single intensity change information.
  • the technical problem to be solved by the present invention is to propose a method and device capable of real-time analysis of an optical signal with a bandwidth greater than 1 THz by using a single-channel receiving end, so as to simultaneously obtain the full optical field information of the signal's intensity and phase in the frequency domain and time domain.
  • the present invention first proposes a measurement method with a large detection bandwidth and real-time measurement of intensity and phase, including the following steps:
  • the signal to be measured undergoes time-domain Fourier transform through time-domain lens focusing technology to obtain real-time spectral information mapped on the time-domain waveform signal;
  • step D performing Fourier inverse transform on the frequency-domain full-field information of the signal to be measured obtained in step C, and recovering the time-domain full-field information of the signal to be tested;
  • step A specifically comprises the following steps:
  • the electro-optical intensity modulator realizes the interception of the time window range of the signal
  • the intensity-modulated signal passes through the electro-optic phase modulator, and the secondary phase of the optical signal in the window is loaded with time.
  • ⁇ f is the "focal length" of the time-domain lens
  • the optical signal carrying the secondary phase is compressed by the optical fiber dispersion ⁇ 2 to obtain the time-domain spectral information of the signal to be measured.
  • the dispersion size ⁇ 2 is the "image distance" of the time-domain lens focusing system.
  • step D the coherent detection utilizes the phase diversity technology to simultaneously obtain two interference signals of in-phase and quadrature, and restore the full optical field information by analyzing the two interference signals of in-phase and quadrature.
  • the present invention also proposes a real-time vector analysis device for optical signals with a detection bandwidth greater than 1 THz, including a time-domain lens focusing system, a first optical fiber mode-locked laser, a first dispersion compensation optical fiber, an optical bandpass filter, a first, a second Polarization controller, coherent receiver, real-time oscilloscope;
  • the time-domain lens focusing system is used to realize the time-domain Fourier transform of the signal to be tested, and realize the mapping transformation from the signal frequency domain to the time domain;
  • the first fiber mode-locked laser is used to generate an ultrashort pulse sequence with a pulse width of less than 1 ps and a pulse repetition frequency of the order of MHz;
  • the first dispersion compensating fiber is used for the first fiber mode-locked laser to perform dispersion stretching to realize chirped frequency-sweeping light source;
  • the optical bandpass filter is used to control the working spectral range of the first fiber mode-locked laser, so as to avoid aliasing of adjacent pulses during the time-domain stretching process;
  • the first and second polarization controllers are used to control the polarization state of the signal light and the local oscillator light input to the coherent receiver, so that the interference effect is the strongest;
  • the coherent receiver is used to realize coherent detection of signal light and local oscillator light, and convert the optical signal into an electrical signal for output;
  • the real-time oscilloscope is used for sampling and analog-to-digital conversion of the electrical signal output by the coherent receiver, and displaying it in real time.
  • the time-domain lens system includes an electro-optic intensity modulator, an electro-optic phase modulator, an arbitrary waveform generator, a second dispersion compensating fiber, and a first optical amplifier;
  • the electro-optical intensity modulator is used to implement time window interception of the signal to be tested;
  • the electro-optical phase modulator is used to load the optical signal in the window with a secondary phase in time
  • the arbitrary waveform generator is used to generate radio frequency signals applied to the electro-optic intensity modulator and the electro-optic phase modulator;
  • the first optical amplifier is used to amplify the optical signal output by the electro-optic intensity modulator to compensate for the optical power loss caused by the electro-optical intensity modulation and the system link;
  • the second dispersion compensating optical fiber is used for performing dispersion compression on the optical signal after secondary phase modulation to obtain time-domain spectral information of the signal to be measured.
  • the present invention realizes the real-time acquisition of the time-domain spectral information of the signal to be measured through the time-domain lens focusing technology. Its real-time measurement frame rate is consistent with the period of the time-domain lens, generally in the order of MHz, which effectively realizes the ultra-fast measurement of the frequency domain information of the signal to be measured.
  • the present invention simultaneously obtains the intensity and phase information of the frequency domain of the signal to be measured through the coherent detection process of the chirped frequency sweep source and the time domain spectral signal of the signal to be measured.
  • the full-field information in the frequency domain is processed by inverse Fourier transform, and the full-field information in the time domain of the signal to be tested is also obtained. Therefore, what the present invention obtains is the whole-field information in the frequency domain and time domain of the signal to be tested.
  • the present invention adopts the chirp-sweeping light source as the coherent detection local oscillator light, converts the frequency of the signal to be measured to the fundamental frequency, reduces the demand for the electrical analog bandwidth, effectively reduces the complexity of the entire detection system structure, and improves The measurement bandwidth of the system is increased, and a measurement bandwidth greater than 1THz can be achieved.
  • the repetition frequency of the chirped frequency-sweeping light source and the period of the time-domain lens system of the present invention can be adjusted according to the requirements of different measurement scenarios.
  • the repetition frequency of the frequency-sweeping source and the period of the time-domain lens system can be increased , can achieve higher frame rate measurement, and capture the frequency domain and time domain full optical field information of the signal under test that changes at a high speed. Therefore, the present invention is of great significance in the scene of real-time full-field information measurement of high-speed signals.
  • Fig. 1 is a schematic structural diagram of a large-bandwidth signal real-time vector analysis device embodied in the present invention.
  • Figure 2 shows the time-domain spectrum information of the signal to be measured passing through the time-domain lens focusing system, and the coordinate axis is obtained by mapping the time-wavelength relationship.
  • Fig. 3 (a) has provided the intensity information loaded on the channel carrier 1545nm in the implementation case
  • Fig. 3 (b) has provided the simulation result of the intensity information loaded on the channel carrier 1545nm measured by the device of the present invention
  • Fig. 3(c) provides the 160Gb/s-16QAM phase symbol information loaded on the channel carrier 1545nm in the implementation case
  • Simulation results of s-16QAM phase symbol information are provided.
  • Fig. 4 (a) has provided the intensity information loaded on the channel carrier 1555nm in the implementation case;
  • Fig. 4 (b) has provided the simulation result of the intensity information loaded on the channel carrier 1555nm measured by the device of the present invention;
  • Fig. 4 (c) provides the 400Gb/s-16QAM phase symbol information loaded on the channel carrier 1555nm in the implementation case;
  • Fig. 4 (d) provides the 400Gb/s-16QAM phase symbol information loaded on the channel carrier 1555nm measured by the device of the present invention /s-16QAM phase symbol information simulation results.
  • the optical signal real-time vector analysis device with a detection bandwidth greater than 1 THz, the device includes a time-domain lens focusing system, a first optical fiber mode-locked laser 6, an optical band-pass filter 7, a first dispersion compensation fiber 8, and a first optical fiber mode-locked laser.
  • the real-time vector analysis method for optical signals with a detection bandwidth greater than 1 THz specifically implemented in the present invention includes the following steps:
  • the output of the first fiber mode-locked laser is a Gaussian ultrashort pulse with a pulse width of about 1 ps and a pulse repetition frequency of 20 MHz.
  • the time domain waveform of a single pulse is expressed as E 1 (t).
  • the specific expression of the time-domain optical signal is as follows:
  • I 1 is the intensity of the ultrashort pulse signal output by the first fiber mode-locked laser
  • t PW is the pulse width of the ultrashort pulse of the first fiber mode-locked laser
  • ⁇ LO is its spectrum center frequency
  • ⁇ 1 is its initial phase
  • t 0 is the center reference moment of the window.
  • the repetition frequency domain of the above-mentioned Gaussian ultrashort pulse is on the order of MHz.
  • the expression of the first fiber mode-locked laser passing through the first dispersion compensating fiber can be obtained from the linear propagation equation of the optical pulse in the fiber. Simplify the analytical model, disregard the effects of higher-order dispersion in dispersion, and avoid nonlinear effects.
  • the dispersion satisfies the far-field dispersion condition, and the electric field of the output local oscillator optical time-domain signal can be approximately expressed as:
  • U 1 ( ⁇ ) is the frequency domain expression of E 1 (t), and ⁇ 1 is the group velocity dispersion of the first dispersion compensating fiber.
  • the electro-optical intensity modulator will intercept the time window, and the secondary phase will be loaded onto the optical signal through the phase modulator.
  • the specific expression of the modulated optical signal is:
  • E s (t) is the expression of the signal to be measured
  • T is the time window size of the time-domain lens system in each period
  • ⁇ f is the "focal length" of the time-domain lens.
  • the output time-domain signal waveform can be obtained from the linear transmission equation of the optical pulse in the fiber:
  • U i ( ⁇ ) is the frequency domain representation of the light field of the time domain lens system output signal
  • ⁇ 2 is the group velocity dispersion of the first dispersion compensation fiber
  • ⁇ f is equal to ⁇ 2
  • ⁇ 2 is equal to ⁇ 1
  • the signal to be measured has completed the time-domain Fourier transform through the time-domain lens focusing system, and its spectral information is mapped to the time-domain waveform.
  • the whole-field information in the frequency domain and time domain of the signal to be tested can be recovered in real time, which effectively reduces the demand for the bandwidth of the detector and the number of detection receivers.
  • the intensity dimension signal is obtained, but also the phase dimension information is obtained at the same time, realizing real-time vector full-field signal analysis.
  • the system can also capture its change vector information at a frame rate of MHz order.
  • the signal to be tested is a 160Gb/s 16QAM signal with a channel carrier of 1545nm and a dual-channel advanced 16QAM signal with a channel carrier of 1555nm and 400Gb/s.
  • Modulation format signal the system observation bandwidth is greater than 10nm, and the time window is 300ps.
  • the device of the invention acquires two channel intensity and phase information simultaneously, and realizes real-time vector measurement and channel monitoring of large bandwidth signals.
  • Figure 2 shows the time-domain spectrum information of the signal to be measured passing through the time-domain lens focusing system, and the coordinate axis is obtained by mapping the time-wavelength relationship.
  • Fig. 3 (a) has provided the intensity information loaded on the channel carrier 1545nm in the implementation case
  • Fig. 3 (c) has provided the simulation result of the intensity information loaded on the channel carrier 1545nm measured by the device of the present invention
  • Fig. 3(b) provides the 160Gb/s-16QAM phase symbol information loaded on the channel carrier 1545nm in the implementation case
  • Simulation results of s-16QAM phase symbol information are provided.
  • Fig. 4 (a) has provided the intensity information loaded on the channel carrier 1555nm in the implementation case;
  • Fig. 4 (c) has provided the simulation result of the intensity information loaded on the channel carrier 1555nm measured by the device of the present invention;
  • Fig. 4 (b) provides the 400Gb/s-16QAM phase symbol information loaded on the channel carrier 1555nm in the implementation case;
  • Fig. 4 (d) provides the 400Gb/s-16QAM phase symbol information loaded on the channel carrier 1555nm measured by the device of the present invention /s-16QAM phase symbol information simulation results.

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Abstract

本发明公开了一种探测带宽大于1THz的光信号实时矢量分析方法及装置，方法为：通过时域透镜聚焦技术将待测信号的频谱映射到不同的时间位置信息；将超短光脉冲经色散充分展宽得到其时域光谱，形成啁啾扫频源；将二者输入到相干接收系统实现干涉过程及光信号到电信号转化，经数据采集处理恢复待测信号的频域强度和相位信息；再通过傅里叶逆变换，恢复其时域全光场信息。装置包括时域透镜聚焦系统，第一色散补偿光纤，第一光纤锁模激光器，光学带通滤波器，第一、第二偏振控制器，相干接收机和实时示波器。本发明实现了对带宽大于1THz的光信号的实时获取其信号时域和频域的强度及其相位的全光场信息，在大带宽多维度信息测量应用场景中有重要的意义。

Description

探测带宽大于1THz的光信号实时矢量分析方法及装置 技术领域
本发明涉及带宽大于1THz光信号实时测量技术领域，特别涉及对带宽大于1THz信号的强度和相位信息同时实时获取分析。
背景技术
随着飞秒锁模激光器的出现以及高速、大容量光通信技术的高速发展，对于高速信号的实时测量表征成为了迫切需要解决的科学问题。同时，光通信高级调制格式信号的表征、任意波形以及非重复性事件的获取分析，将光信号的分析复杂性推到了新的高度，这对光信号的测量处理提出了更高的要求。
传统的将光信号通过光电探测器转换成电信号，然后利用电学系统来进行信号处理的方式，对于带宽大于100GHz的光信号难以实现实时测量观测，通常也仅能获取单一维度的强度信息，并且成本也非常高昂。
传统电学分析和处理光信号的方法受限于模数、数模转换带宽、探测器带宽，因此很难应用在这种大带宽光信号实时矢量测量分析场景中。时域光学的发展则给大带宽信号测量分析开辟了一些新的途径，其中研究最为广泛的即时域成像。为了表征飞秒量级精度的超短脉冲，Rick Trebino与Dan Kane提出了频率分辨光学开关的方法，其将待测脉冲分为两束，并产生相对时间延时，利用两脉冲在非线性介质中相互作用，得到二维的时间-频率分布图，再使用二维位相重建迭代算法便可提取脉冲的强度和相位信息(D.J.Kane and R.Trebino.Single-shot measurement of the intensity and phase of an arbitrary ultrashort pulse by using frequency-resolved optical gating.Optics Letters,1993,vol.18,no.10,823-825)。但是其测量时间窗口范围通常仅有几十皮秒，并且测量帧率也非常受限，因此无法实现实时超快的测量。
时域透镜放大技术则是另一种测量高速信号的方式，其初衷之一即解决受限的探测带宽在高速光波形探测上的困难。类似于空间透镜放大系统。输入信号经过时域成像系统就可以被放大。该方案中待测信号经过第一段色散器件时域拉伸后，经过时域透镜系统，再经过第二段色散单元继续拉伸，此时第二段色散量是第一段色散量的N倍，最终输出信号时间窗口是待测信号时间窗口的N倍放大，这样就使得系统采集待测信号的探测带宽、模数转换带宽下降了N倍。高速信号通过时域放大即相当于降速，然后就可以用低速的实时采样系统对此进行采集和观测(R Salem et al.Optical time lens  based on four-wave mixing on a silicon chip.Optics Letters,2008,vol.33,no.10 1047-1049)。系统放大倍率等于输出色散与输入色散的比值，系统测量时间窗口决定于前级pump色散的大小，受限于放大倍率与色散量之间的制约，其测量时间范围通常为200ps。为了扩大系统测量时域窗口，利用延时缓存环技术结合时域放大方法，可以实现测量时间窗口的有效倍增。时域分割的方式有效提升了信号时间窗口范围，但是测量的帧率受到了制约，同时也只得到随时间变化的光信号的强度信息，另一维度的相位变化信息丢失。时域光学实现超快波形测量的另一个重要途径即时域傅里叶变换，通过将时域波形转换到光谱上测量来规避时域探测的带宽受限问题。实现时域傅里叶变换的方式主要是基于时域透镜的方法，其实现方法通常基于电光相位调制器及四波混频等非线性参量过程。输入信号经过输入色散传输后，再经过时域透镜在时域上加载二次相位调制，最后经过输出色散实现待测信号时域信息到频域的映射。当输入色散与输出色散相等时，输出光场频谱的幅度是输出光场时域的映射(M.Foster et al.Silicon-chip-based ultrafast optical oscilloscope.Nature,2008,vol.456,no.7218,81-84)。但是该方法时间窗口受限于时域透镜的窗口大小，同样也只能实现单一强度变化信息的表征。
为了同时捕获大带宽信号的强度和相位信息，频谱分割技术也得到了广泛的应用。将大带宽信号利用不同频率的本振光实现多路相干探测完成探测接收，同时获取不同频谱片段的强度和相位信息，再在频域进行频谱恢复，利用傅里叶逆变换得到其大带宽时域矢量信息(N.Fontaine et al.Real-time full-field arbitrary optical waveform measurement.Nature Photonics,2010,vol.4,no.4,248–254)。该测量方法有效避开了电学带宽瓶颈的限制，但是其系统复杂程度高，系统进一步拓展探测带宽到THz量级受到较大限制。通过对现有技术的分析，可以发现当前的大带宽信号实时分析测量难以实现在THz量级的测量带宽下，既保证测量时间窗口以及系统的低复杂度，同时实时获取强度和相位的全光场信息，进行矢量分析。
发明内容
本发明所要解决的技术问题是提出能利用单通道的接收端实现对带宽大于1THz光信号实时分析的方法和装置，实现同时获取信号在频域和时域的强度和相位全光场信息。
为解决上述技术问题，本发明首先提出一种探测带宽大并且可以实时测量强度和相位的测量方法，包括以下步骤：
A、待测信号经过时域透镜聚焦技术实现时域傅里叶变换，得到映射在时域波形信号上的实时光谱信息；
B、将超短光脉冲经色散大小为Φ 1的色散作用充分展宽得到其时域光谱，形成啁啾扫频源，作为相干探测的本振光；
C、将映射在时域波形信号上的光谱信息与相干探测的本振光进行相干探测，将相干得到的光信号转化为电信号，所述电信号经数据采集处理，恢复待测信号的频域强度和相位信息；
D、将步骤C得到的待测信号的频域全场信息进行傅里叶逆变换，恢复待测信号的时域全光场信息；
其中步骤A具体包括如下步骤：
A1、电光强度调制器实现对信号的时间窗口范围截取；
A2、强度调制后的信号再经过电光相位调制器，对窗口内光信号加载时间上的二次相位
Figure PCTCN2022132832-appb-000001
实现时域透镜功能，Φ f为所述时域透镜的“焦距”；
A3、携带二次相位的光信号通过光纤色散Φ 2作用使之压缩，得到待测信号的时域光谱信息，色散大小Φ 2为时域透镜聚焦系统的“像距”。
其中，步骤A2中对应的“焦距”Φ f与步骤A3中的“像距”Φ 2满足一定的成像条件以实现聚焦成像，即Φ f＝Φ 2。
其中，步骤A3中的“像距”Φ 2的色散量Φ 2应与步骤C中的色散量Φ 1相等，即Φ 2＝
Φ 1；
其中，步骤D相干探测利用了相位分集技术，同时获取同相和正交的两路干涉信号，通过分析同相和正交的两路干涉信号恢复其全光场信息。
本发明同时提出了一种探测带宽大于1THz的光信号实时矢量分析装置，包括时域透镜聚焦系统，第一光纤锁模激光器，第一色散补偿光纤，光学带通滤波器，第一、第二偏振控制器，相干接收机，实时示波器；
所述时域透镜聚焦系统，用于对待测信号实现时域傅里叶变换，实现信号频域到时域的映射变换；
所述第一光纤锁模激光器用于产生脉宽小于1ps，脉冲重复频率为MHz量级的超短脉冲序列；
所述第一色散补偿光纤，用于第一光纤锁模激光器进行色散拉伸作用以实现啁啾的扫频光源；
所述光学带通滤波器，用于控制第一光纤锁模激光器的工作光谱范围，避免实现时域拉伸过程中发生相邻脉冲混叠；
所述第一、第二偏振控制器，用于控制输入到相干接收机的信号光和本振光的偏振状态，使其干涉效果最强；
所述相干接收机，用于信号光与本振光实现相干探测，并将光信号转换成为电信号输出；
所述的实时示波器，用于对相干接收机输出的电信号进行采样和模数转换，并实时显示。
其中，所述时域透镜系统包括电光强度调制器，电光相位调制器，任意波形发生器，第二色散补偿光纤，第一光放大器；
所述电光强度调制器，用于对待测信号实现时间窗口截取；
所述电光相位调制器，用于对窗口内光信号加载时间上的二次相位；
所述任意波形发生器，用于产生施加在电光强度调制器及电光相位调制器上的射频信号；
所述第一光放大器，用于将电光强度调制器输出的光信号放大，补偿电光强度调制及系统链路带来的光功率损耗；
所述第二色散补偿光纤，用于对二次相位调制后的光信号进行色散压缩得到待测信号时域光谱信息。
其中，所述基于电光相位调制器的时域透镜“焦距”Φ f与第二色散补偿光纤的色散量Φ 2应该相等，即Φ f＝Φ 2。
其中，所述第一色散补偿光纤和第二色散补偿光纤的色散量大小相等，即Φ 1＝Φ 2。
本发明具有以下有益效果：
(1)本发明通过时域透镜聚焦技术，实现待测信号的时域光谱信息的实时获取。其实时测量帧率与时域透镜周期一致，一般为MHz量级，有效实现了待测信号频域信息的超快测量。
(2)本发明通过啁啾扫频源与待测信号时域光谱信号的相干探测过程，同时获取了待测信号频域的强度和相位信息。将频域全场信息进行傅里叶逆变换处理，待测信号时域的全光场信息也得到了获取。因此，本发明获得的是待测信号频域及时域的全场信息。
(3)本发明采用啁啾扫频光源作为相干探测本振光，将待测信号频率都转化到了基频，降低了对电学模拟带宽的需求，有效降低了整个检测系统结构的复杂度，提高了系统测量带宽，可以实现大于1THz的测量带宽。
(4)本发明的啁啾扫频光源的重复频率与时域透镜系统的周期可以根据不同测量场景需求进行调节，对于高速动态变化的待测信号，增加扫频源的重复频率及时域透镜周期，可以实现更高帧率的测量，捕获高速变化的待测信号的频域及时域全光场信息。因此，本发明在高速信号的实时全场信息测量场景中有重要意义。
附图说明
下面结合附图和具体实施方式对本发明的技术方案作进一步详细说明；但本发明的一种探测带宽大于1THz的光信号实时矢量分析方法及装置不局限于实施例。
图1为本发明具体实施的大带宽信号实时矢量分析装置的结构示意图。
图2给出了待测信号经过时域透镜聚焦系统的时域频谱信息，坐标轴由时间-波长关系映射得到。
图3(a)给出了实施案例中加载在信道载波1545nm上的强度信息；图3(b)给出了通过本发明装置测得的加载在信道载波1545nm上的强度信息的仿真结果；图3(c)给出了实施案例中加载在信道载波1545nm上的160Gb/s-16QAM相位码元信息；图3(d)给出了通过本发明装置测得加载在信道载波1545nm上的160Gb/s-16QAM相位码元信息的仿真结果。
图4(a)给出了实施案例中加载在信道载波1555nm上的强度信息；图4(b)给出了通过本发明装置测得的加载在信道载波1555nm上的强度信息的仿真结果；图4(c)给出了实施案例中加载在信道载波1555nm上的400Gb/s-16QAM相位码元信息；图4(d)给出了通过本发明装置测得的加载在信道载波1555nm上的400Gb/s-16QAM相位码元信息的仿真结果。
具体实施方式
如图1所示的探测带宽大于1THz的光信号实时矢量分析装置，该装置包括时域透镜聚焦系统，第一光纤锁模激光器6，光学带通滤波器7，第一色散补偿光纤8，第二偏振控制器9，第一偏振控制器10，相干接收机11，示波器12；其中，时域透镜聚焦系统包括电光强度调制器1，第一光放大器2，电光相位调制器3，任意波形发生器4，第二色散补偿光纤5。
本发明具体实施的探测带宽大于1THz的光信号实时矢量分析方法具体包括如下步骤：
1)第一光纤锁模激光器的输出为高斯型超短脉冲，脉宽为1ps左右、脉冲重复频率为20MHz，单个脉冲时域波形表示为E 1(t)。其时域光信号具体表达如下：
Figure PCTCN2022132832-appb-000002
式中，I 1为第一光纤锁模激光器输出超短脉冲信号的强度，t PW为第一光纤锁模激光器超短脉冲的脉冲宽度，ω LO为其频谱中心频率,φ 1为其初始相位，t 0为窗口的中心参考时刻。上述高斯型超短脉冲的重复频域为MHz量级。
2)由光纤中光脉冲线性传输方程可以得到第一光纤锁模激光器经过第一色散补偿光纤后表达式。简化分析模型，不考虑色散中的高阶色散影响，并避免非线性效应。色散满足远场色散条件，输出本振光时域信号电场可以近似表示为：
Figure PCTCN2022132832-appb-000003
其中，U 1(ω)为E 1(t)的频域表达式,Φ 1为第一色散补偿光纤的群速度色散大小。
3)待测信号经过时域透镜系统，会进行电光强度调制器截取时间窗口，通过相位调制器加载二次相位到光信号上，被调制后的光信号的具体表示为：
Figure PCTCN2022132832-appb-000004
其中，E s(t)为待测信号表达式,T为时域透镜系统在每个周期内的时间窗口大小，Φ f为时域透镜的“焦距”。
4)被调制的信号经过第二色散补偿光纤进行色散压缩时,由光纤中光脉冲的线性传输方程可以得到输出时域信号波形为：
Figure PCTCN2022132832-appb-000005
其中，U i(ω)为时域透镜系统输出信号的光场的频域表示,Φ 2为第一色散补偿光纤的群速度色散大小，Φ f与Φ 2相等，且Φ 2与Φ 1相等，U s(ω)待测信号的光场的频域表示。待测信号通过时域透镜聚焦系统完成了时域傅里叶变换，其光谱信息映射到了时域波形。
5)经过时域傅里叶变换得到的待测信号时域频谱信息E out(t)与扫频源E LO(t)分别作为信号光和本振光输入相干光接收机中，通过调节偏振控制器，使得偏振态对准干涉，保证干涉强度最强。经过相位分集技术，再经过两路平衡探测器输出得到干涉信号的同相和正交两路信号，其可以表示为：
Figure PCTCN2022132832-appb-000006
6)通过模数转换、数据采集处理得到的强度和相位矢量信息。为了简化计算，我们在这里不考虑高阶色散及非线性的影响。利用时间-频率变换关系：t＝t 0+Φ f(ω–ω LO)，将时间轴变换为频率轴，恢复得到其频域全场信号的表达式近似表示为：
Figure PCTCN2022132832-appb-000007
7)对式(6)进行傅里叶逆变换，得到待测信号时域全光场信号的近似表示为：
Figure PCTCN2022132832-appb-000008
当本振光脉冲脉宽无穷窄时，式(7)可以进一步简化近似表示为：
Figure PCTCN2022132832-appb-000009
上式可以看到，待测信号的频域及时域全场信息都实现了实时恢复，有效降低了对于探测器带宽及探测接收端数量的需求。同时不仅获取强度维度信号，还同时获取了相位维度的信息，实现了实时的矢量全场信号分析，对于快速变化的信号，系统同样可以以MHz量级帧率来捕获其变化矢量信息，下面将以应用实例予以说明。
实施案例
为了验证本方案具备大带宽信号实时矢量分析能力，本方案通过仿真模型验证，待测信号为信道载波为1545nm的160Gb/s的16QAM信号以及信道载波为1555nm的400Gb/s的16QAM的双信道高级调制格式信号，系统观测带宽大于10nm，时间窗口 为300ps。本发明装置将两个信道强度和相位信息同时获取下来，实现大带宽信号的实时矢量测量及信道监测。
图2给出了待测信号经过时域透镜聚焦系统的时域频谱信息，坐标轴由时间-波长关系映射得到。
图3(a)给出了实施案例中加载在信道载波1545nm上的强度信息；图3(c)给出了通过本发明装置测得的加载在信道载波1545nm上的强度信息的仿真结果；图3(b)给出了实施案例中加载在信道载波1545nm上的160Gb/s-16QAM相位码元信息；图3(d)给出了通过本发明装置测得加载在信道载波1545nm上的160Gb/s-16QAM相位码元信息的仿真结果。
图4(a)给出了实施案例中加载在信道载波1555nm上的强度信息；图4(c)给出了通过本发明装置测得的加载在信道载波1555nm上的强度信息的仿真结果；图4(b)给出了实施案例中加载在信道载波1555nm上的400Gb/s-16QAM相位码元信息；图4(d)给出了通过本发明装置测得的加载在信道载波1555nm上的400Gb/s-16QAM相位码元信息的仿真结果。从图中可以看出，本发明的一种探测带宽大于1THz的光信号实时矢量分析方法及装置可以对大带宽信号实现实时的时域及频域的全光场信息获取，完成矢量分析。
以上具体实施例仅用来进一步说明本发明的一种探测带宽大于1THz的光信号实时矢量分析方法及装置，本发明并不局限于实施例。应当指出，对本领域的普通技术人员来说，在不脱离本发明技术原理的前提下，还可以对本发明的技术方案进行修改或者等同替换，其均应涵盖在本发明的权利要求范围当中。

Claims (9)

  1. 一种探测带宽大于1THz的光信号实时矢量分析方法，其特征在于，包括以下步骤：
    A、待测信号经过时域透镜聚焦技术实现时域傅里叶变换，得到映射在时域波形信号上的实时光谱信息；
    B、将超短光脉冲经色散大小为Φ 1的色散作用充分展宽得到其时域光谱，形成啁啾扫频源，作为相干探测的本振光；
    C、将映射在时域波形信号上的光谱信息与相干探测的本振光进行相干探测，将相干得到的光信号转化为电信号，所述电信号经数据采集处理，恢复待测信号的频域强度和相位信息；
    D、将步骤C得到的待测信号的频域全场信息进行傅里叶逆变换，恢复待测信号的时域全光场信息。
  2. 根据权利要求1所述的探测带宽大于1THz的光信号实时矢量分析方法，其特征在于：所述步骤A具体包括如下步骤：
    A1、电光强度调制器实现对信号的时间窗口范围截取；
    A2、强度调制后的信号再经过电光相位调制器，对窗口内光信号加载时间上的二次相位
    Figure PCTCN2022132832-appb-100001
    实现时域透镜功能，Φ f为所述时域透镜的“焦距”；
    A3、携带二次相位的光信号通过光纤色散Φ 2作用使之压缩，得到待测信号的时域光谱信息，色散大小Φ 2为时域透镜聚焦系统的“像距”。
  3. 根据权利要求2所述的探测带宽大于1THz的光信号实时矢量分析方法，其特征在于：步骤A2中对应的“焦距”Φ f与步骤A3中的“像距”Φ 2相等，即Φ f＝Φ 2。
  4. 根据权利要求3所述的探测带宽大于1THz的光信号实时矢量分析方法，其特征在于：步骤A3中的“像距”的色散量Φ 2应与步骤B中的色散量Φ 1相等，即Φ 2＝Φ 1。
  5. 根据权利要求1所述的探测带宽大于1THz的光信号实时矢量分析方法，其特征在于：所述步骤C中的相干探测利用了相位分集技术，同时获取同相和正交的两路干涉信号，通过分析同相和正交的两路干涉信号恢复其全光场信息。
  6. 一种探测带宽大于1THz的光信号实时矢量分析装置，其特征在于：包括时域透镜聚焦系统，第一光纤锁模激光器，光学带通滤波器，第一色散补偿光纤，第一、第二偏振控制器，相干接收机，实时示波器；
    所述时域透镜聚焦系统，用于对待测信号实现时域傅里叶变换，实现信号频域到时域的映射变换；
    所述第一光纤锁模激光器用于产生脉宽小于1ps，脉冲重复频率为MHz量级的超短脉冲序列；
    所述第一色散补偿光纤，用于第一光纤锁模激光器进行色散拉伸作用以实现啁啾的扫频光源；
    所述光学带通滤波器，用于控制第一光纤锁模激光器的工作光谱范围，避免实现时域拉伸过程中发生相邻脉冲混叠；
    所述第一、第二偏振控制器，分别用于控制输入到相干接收机的信号光和本振光的偏振状态，使其干涉效果最强；
    所述相干接收机，用于信号光与本振光实现相干探测，并将光信号转换成为电信号输出；
    所述的实时示波器，用于对相干接收机输出的电信号进行采样和模数转换，并实时显示。
  7. 根据权利要求5所述的探测带宽大于1THz的光信号实时矢量分析装置，其特征在于：所述时域透镜系统包括电光强度调制器，电光相位调制器，任意波形发生器，第二色散补偿光纤，第一光放大器；
    所述电光强度调制器，用于对待测信号实现时间窗口截取；
    所述电光相位调制器，用于对窗口内光信号加载时间上的二次相位；
    所述任意波形发生器，用于产生施加在电光强度调制器及电光相位调制器上的射频信号；
    所述第一光放大器，用于将电光强度调制器输出的光信号放大，补偿电光强度调制及系统链路带来的光功率损耗；
    所述第二色散补偿光纤，用于对二次相位调制后的光信号进行色散压缩得到待测信号时域光谱信息。
  8. 根据权利要求6所述的探测带宽大于1THz的光信号实时矢量分析装置，其特征在于：所述基于电光相位调制器的时域透镜“焦距”Φ f与第二色散补偿光纤的色散量Φ 2相等，即Φ f＝Φ 2。
  9. 根据权利要求7所述的探测带宽大于1THz的光信号实时矢量分析装置，其特征在于：所述第一色散补偿光纤和第二色散补偿光纤的色散量大小相等，即Φ 1＝Φ 2。
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