CN108566244B - Multichannel parallel optical device spectral response measuring method and device - Google Patents

Multichannel parallel optical device spectral response measuring method and device Download PDF

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CN108566244B
CN108566244B CN201810357361.XA CN201810357361A CN108566244B CN 108566244 B CN108566244 B CN 108566244B CN 201810357361 A CN201810357361 A CN 201810357361A CN 108566244 B CN108566244 B CN 108566244B
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frequency
comb
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CN108566244A (en
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潘时龙
卿婷
李树鹏
薛敏
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Nanjing University of Aeronautics and Astronautics
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Nanjing University of Aeronautics and Astronautics
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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
    • H04B10/07—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
    • H04B10/077—Arrangements for monitoring or testing transmission systems; Arrangements for fault measurement of transmission systems using an in-service signal using a supervisory or additional signal
    • 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
    • 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
    • H04B10/077—Arrangements for monitoring or testing transmission systems; Arrangements for fault measurement of transmission systems using an in-service signal using a supervisory or additional signal
    • H04B10/0775—Performance monitoring and measurement of transmission parameters

Abstract

The invention discloses a multichannel parallel optical device spectral response measuring method, which comprises the following steps: step 1, modulating a microwave signal to a first optical frequency comb signal to generate a multichannel carrier suppression optical double-sideband signal; then coupling the optical fiber with a second optical frequency comb signal to generate a multichannel asymmetric optical double-sideband signal, namely a detection optical signal; the comb tooth frequency intervals of the first optical frequency comb signal and the second optical frequency comb signal are different; step 2, performing photoelectric conversion on the detection optical signal after passing through the optical device to be detected, and then extracting the frequency spectrum response of the optical device to be detected in each channel in parallel; and 3, combining the frequency response of the optical device to be tested on each channel into a complete frequency spectrum response of the optical device to be tested. The invention also discloses a multichannel parallel optical device spectral response measuring device. The invention can realize high resolution, large-scale and high-precision measurement, avoid the mutual crosstalk of different channels, and effectively eliminate the frequency dependence of the receiver and the measurement error caused by modulation nonlinearity.

Description

multichannel parallel optical device spectral response measuring method and device
Technical Field
The invention relates to a method for measuring spectral response of an optical device, in particular to a method and a device for measuring spectral response of an optical device in a multi-channel parallel mode, and belongs to the technical field of optical device measurement.
Background
In recent years, with rapid development and popularization of optical communication, photonic technology has been rapidly developed and continuously improved, and requirements for optical device measurement technology essential in the processes of optical device manufacturing, production, application, detection and the like are also higher and higher. However, the existing optical device measurement technology has many problems such as low measurement accuracy and resolution, small measurement range, etc. In 1998 j.e.roman proposed an optical vector analysis method based on optical single sideband modulation [ j.e.rom a n, m.y.frankel, and r.d.eman, "Spectral characterization of fiber characterization with high resolution," opt.let, vol.23, No.12, pp.939-941, jun.1998 ]. With the benefit of mature electrical spectrum analysis technology, the optical vector analysis method based on optical single-sideband modulation can convert coarse-grained optical domain frequency sweep into high-precision electrical domain frequency sweep, so that the measurement resolution is greatly improved and can theoretically reach the Hz magnitude (the resolution of the existing commercial optical vector analyzer is 200MHz), and the high-resolution and high-precision measurement of optical devices is realized. However, the optical vector analysis method based on optical single-sideband modulation is limited by the current electrical spectrum analysis technology, high-precision electrical spectrum analysis can be realized only in the range of 50GHz, and the measurement accuracy is influenced by high-order sidebands caused by modulation nonlinearity. Recently, the Optical device measurement method based on asymmetric double-sideband modulation proposed by "Optical vector based on asymmetric Optical double-sideband modulation using an Optical-drive double-sideband modulator" (t.qing, s.p.li, m.xue, w.li, n.h.zhu and s.l.pan, "Optical vector based on asymmetric Optical double-sideband modulation using a double-sideband modulator," Optics, vol.25, No.5, pp.4665-4671, mar.2017 ") can achieve simultaneous measurement of amplitude response and phase response, increase the linear measurement range of single-sideband modulation, and cause high-order sideband measurement accuracy. However, this method still cannot satisfy the measurement range of few THz in the optical device.
To further increase the measurement range, schlemn et al combine the optical comb with the optical vector analysis technique based on optical single-sideband modulation in "wireless optical vector network based on optical single-sideband modulation and optical frequency vector" (m.xue, y.j.zhao, x.w.gu and s.l.pan, "Performance analysis of optical vector and optical single-sideband modulation," Journal of the optical Society of America B, No. 30, No.4, 928.928-933, ap.2013.) so that the measurement range is greatly increased, but this method has the disadvantages: 1. each channel needs to be measured in sequence, if the time for measuring one channel is T, the time for measuring N channels is NT, the larger the expanded measurement range is, the longer the measurement time is, which is contrary to the actual requirement, and the shorter the measurement time is required in the actual measurement, the better the measurement efficiency can be improved; 2. because the rejection ratio of the filter is limited in practice, when one comb is filtered out, the other comb still remains, and these remaining combs can also generate modulation signals, including not only single-sideband signals but also high-order sidebands, which can beat with adjacent sidebands or remaining comb signals in the photodetector to generate frequency components the same as the measurement result, and different channels crosstalk with each other, resulting in a great measurement error; 3. there is a wavelength dependence, and once the wavelength of the carrier changes, the center wavelength of the subsequent measuring device needs to be changed.
In order to realize fast measurement, 2015, a person wearing a hall et al used "an apparatus and method for measuring frequency response of an optical device" (CN 201510345041.9) two rows of optical frequency combs with different repetition frequencies, a first optical frequency comb is used as a detection signal, the amplitude and phase information of the detection signal is obtained through a device to be measured, a second optical frequency comb is used as a reference signal, the first optical frequency comb and the second optical frequency comb beat in a photoelectric detector, and because the repetition frequencies of the two rows of optical frequency combs are different, the frequency difference between the detection signal and the reference signal in each channel is different, so that the amplitude and phase information of different channels can be distinguished in frequency. The method has the advantages that amplitude and phase information on frequency points covered by all the first optical frequency combs can be measured at one time, and the method is suitable for measuring fast-changing physical phenomena. The disadvantages of this method are: 1. the number of measurement points is equal to the number of comb teeth of the optical frequency comb, so that the resolution is very low and the method is not suitable for measuring narrow-spectrum optical devices; 2. if a certain resolution is required, the repetition frequency of the optical frequency comb is small, so that the measurement range is small and the measurement is not suitable for measuring a wide-spectrum optical device; 3. for the purpose of fast measurement, a time domain receiving method (a DSP or oscilloscope or a time domain sampling instrument) must be used, and a high signal-to-noise ratio and a large dynamic range cannot be obtained.
from the above analysis, it is very difficult to achieve a large measurement range, a high resolution, and a fast measurement at the same time.
Disclosure of Invention
The technical problem to be solved by the invention is to overcome the defects of the prior art and provide a multichannel parallel optical device spectral response measuring method and device, which can realize high-resolution, large-range and quick high-precision measurement at the same time, avoid the mutual crosstalk of different channels and effectively eliminate the frequency dependence of a receiver and the measuring error caused by modulation nonlinearity.
The invention specifically adopts the following technical scheme to solve the technical problems:
A multichannel parallel optical device spectral response measuring method comprises the following steps:
Step 1, obtaining a detection light signal by the following method: modulating the microwave signal to a first optical frequency comb signal to generate a multi-channel carrier suppression optical double-sideband signal, wherein each comb tooth of the first optical frequency comb signal corresponds to one channel; then, coupling the multichannel carrier suppression optical double-sideband signal with a second optical frequency comb signal to generate a multichannel asymmetric optical double-sideband signal, namely the detection optical signal; the comb tooth frequency intervals of the first optical frequency comb signal and the second optical frequency comb signal are different;
Step 2, performing photoelectric conversion on the detection optical signal after passing through the optical device to be detected, and then extracting the frequency spectrum response of the optical device to be detected in each channel in parallel from the converted electric signal;
And 3, combining the amplitude-frequency response and the phase-frequency response of the optical device to be tested on each channel into a complete frequency spectrum response of the optical device to be tested.
preferably, the specific method for extracting the spectral response of the to-be-detected optical device in each channel in parallel in step 2 is as follows: and extracting the frequency spectrum response of each channel from the converted electric signals in parallel, and then respectively removing the frequency spectrum response of the measuring system in the corresponding channel from the frequency spectrum response of each channel to obtain the frequency spectrum response of the optical device to be measured in each channel.
further, the spectral response of the measurement system at each channel is obtained by the following parallel method: and dividing a parallel reference signal from the detection optical signal, directly performing photoelectric conversion on the reference signal, and extracting the frequency spectrum response of each channel in parallel from the converted electric signal, namely the frequency spectrum response of the measurement system in each channel.
Preferably, the microwave signal is a microwave frequency sweep signal.
Preferably, the first and second optical-frequency comb signals satisfy the following condition:
|ωshift|>|(N-1)Δω′|,ifωshift<0,Δω′>0orωshift>0,Δω′<0
wherein, ω isstartis the angular frequency, ω, of the first comb tooth in the first optical frequency comb signalshiftIs a frequency difference between a first comb tooth in the first optical-frequency comb signal and a first comb tooth in the second optical-frequency comb signal, Δ ω is a comb tooth frequency interval of the first optical-frequency comb signal, Δ ω' is a frequency difference between a comb tooth frequency interval of the first optical-frequency comb signal and a comb tooth frequency interval of the second optical-frequency comb signal, ωsampleIs the sampling bandwidth of the spectral response extraction, and N is the comb tooth number of the first optical frequency comb signal.
the following technical scheme can be obtained according to the same invention concept:
A multi-channel parallel optical device spectral response measurement apparatus, comprising:
a detection light signal generation module for obtaining a detection light signal by: modulating the microwave signal to a first optical frequency comb signal to generate a multi-channel carrier suppression optical double-sideband signal, wherein each comb tooth of the first optical frequency comb signal corresponds to one channel; then, coupling the multichannel carrier suppression optical double-sideband signal with a second optical frequency comb signal to generate a multichannel asymmetric optical double-sideband signal, namely the detection optical signal; the comb tooth frequency intervals of the first optical frequency comb signal and the second optical frequency comb signal are different;
The microwave amplitude-phase detection module is used for performing photoelectric conversion on the detection optical signal passing through the optical device to be detected and extracting the frequency spectrum response of the optical device to be detected in each channel in parallel from the converted electric signal;
And the main control unit is used for combining the amplitude-frequency response and the phase-frequency response of the optical device to be tested on each channel into a complete frequency spectrum response of the optical device to be tested.
preferably, the microwave amplitude and phase detection module comprises:
The first photoelectric conversion module is used for performing photoelectric conversion on the detection optical signal passing through the optical device to be detected;
the first amplitude and phase extraction module is used for extracting the frequency spectrum response of each channel in parallel from the electric signal converted by the first photoelectric conversion module;
And the correction module is used for respectively removing the spectral response of the measurement system in the corresponding channel from the spectral response of each channel extracted by the first amplitude-phase extraction module to obtain the spectral response of the optical device to be measured in each channel.
Further, the correction module includes:
The second photoelectric conversion module is used for performing photoelectric conversion on one path of parallel reference signals which are separated from the detection optical signal;
and the second amplitude and phase extraction module is used for extracting the frequency spectrum response of each channel in parallel from the electric signal converted by the second photoelectric conversion module, namely the frequency spectrum response of the measurement system in each channel.
Preferably, the microwave signal is a microwave frequency sweep signal.
Preferably, the first and second optical-frequency comb signals satisfy the following condition:
|ωshift|>|(N-1)Δω′|,ifωshift<0,Δω′>0orωshift>0,Δω′<0
wherein, ω isstartIs the angular frequency, ω, of the first comb tooth in the first optical frequency comb signalshiftIs a frequency difference between a first comb tooth in the first optical-frequency comb signal and a first comb tooth in the second optical-frequency comb signal, Δ ω is a comb tooth frequency interval of the first optical-frequency comb signal, Δ ω' is a frequency difference between a comb tooth frequency interval of the first optical-frequency comb signal and a comb tooth frequency interval of the second optical-frequency comb signal, ωsampleis the sampling bandwidth of the spectral response extraction, and N is the comb tooth number of the first optical frequency comb signal.
Compared with the prior art, the invention has the following beneficial effects:
1. Meanwhile, the requirements of large measurement range, high resolution and rapid measurement are met; 2. different from the prior serial measurement mode, the parallel measurement makes the measurement time irrelevant to the channel number, and if the time for measuring one channel is T, the time for measuring N channels is still T; 3. the detection signals of different channels have different frequencies after being converted into point electric signals, so that the problem of crosstalk of different channels is avoided; 4. the measurement is not affected by high-order sidebands caused by modulation nonlinearity; 5. the measurement range is greatly improved, and if N optical frequency combs are used, the measurement range is expanded to 2N times; 6. the measuring system has no wavelength dependence, the wavelength of the light source is changed, and the subsequent measuring device does not need to be adjusted.
Drawings
FIG. 1 is a schematic structural diagram of a preferred embodiment of an optical device spectral response measuring apparatus according to the present invention;
FIG. 2 is a schematic structural diagram of an optical frequency comb module in a preferred embodiment;
FIG. 3 is a signal schematic at various locations in the apparatus of FIG. 1;
FIG. 4 shows the measurement result when the number of teeth of the optical frequency comb is 3;
FIG. 5 shows the measurement result when the number of teeth of the optical frequency comb is 5;
Fig. 6 is a schematic structural diagram of another embodiment of the spectral response measuring device of the optical device of the present invention.
Detailed Description
Aiming at the defects of the prior art, the idea of the invention is that on the basis of the existing optical device measuring method based on asymmetric double-sideband modulation, two groups of optical frequency comb signals with different comb tooth frequency intervals are utilized to generate a multi-channel asymmetric optical double-sideband signal; because the comb tooth frequency intervals of the two groups of optical frequency comb signals are different, the frequency difference between the double-side band signals of different channels in the multichannel asymmetric optical double-side band signals and the corresponding local oscillator signals is different, the frequencies of the double-side band signals and the local oscillator signals after the beat frequency of the double-side band signals is converted into electric signals in the photoelectric detector are different, and the signal aliasing of different channels is avoided.
Specifically, the method for measuring the spectral response of the multichannel parallel optical device comprises the following steps: step 1, obtaining a detection light signal by the following method: modulating the microwave signal to a first optical frequency comb signal to generate a multi-channel carrier suppression optical double-sideband signal, wherein each comb tooth of the first optical frequency comb signal corresponds to one channel; then, coupling the multichannel carrier suppression optical double-sideband signal with a second optical frequency comb signal to generate a multichannel asymmetric optical double-sideband signal, namely the detection optical signal; the comb tooth frequency intervals of the first optical frequency comb signal and the second optical frequency comb signal are different;
step 2, performing photoelectric conversion on the detection optical signal after passing through the optical device to be detected, and then extracting the frequency spectrum response of the optical device to be detected in each channel in parallel from the converted electric signal;
And 3, combining the amplitude-frequency response and the phase-frequency response of the optical device to be tested on each channel into a complete frequency spectrum response of the optical device to be tested.
The invention relates to a multichannel parallel optical device frequency spectrum response measuring device, which comprises:
A detection light signal generation module for obtaining a detection light signal by: modulating the microwave signal to a first optical frequency comb signal to generate a multi-channel carrier suppression optical double-sideband signal, wherein each comb tooth of the first optical frequency comb signal corresponds to one channel; then, coupling the multichannel carrier suppression optical double-sideband signal with a second optical frequency comb signal to generate a multichannel asymmetric optical double-sideband signal, namely the detection optical signal; the comb tooth frequency intervals of the first optical frequency comb signal and the second optical frequency comb signal are different;
the microwave amplitude-phase detection module is used for performing photoelectric conversion on the detection optical signal passing through the optical device to be detected and extracting the frequency spectrum response of the optical device to be detected in each channel in parallel from the converted electric signal;
And the main control unit is used for combining the amplitude-frequency response and the phase-frequency response of the optical device to be tested on each channel into a complete frequency spectrum response of the optical device to be tested.
In the above technical solution, the microwave signal may be a fixed frequency microwave signal or a frequency sweep signal, and preferably, the frequency sweep signal is adopted, so that the measurement range can be further expanded.
In order to arrange the detection signals converted into the electrical signals according to a certain rule and eliminate the problem of frequency overlapping, the first optical-frequency comb signal and the second optical-frequency comb signal preferably satisfy the following conditions:
|ωshift|>|(N-1)Δω′|,ifωshift<0,Δω′>0orωshift>0,Δω′<0
wherein, ω isstartIs the angular frequency, ω, of the first comb tooth in the first optical frequency comb signalshiftIs a frequency difference between a first comb tooth in the first optical-frequency comb signal and a first comb tooth in the second optical-frequency comb signal, Δ ω is a comb tooth frequency interval of the first optical-frequency comb signal, Δ ω' is a frequency difference between a comb tooth frequency interval of the first optical-frequency comb signal and a comb tooth frequency interval of the second optical-frequency comb signal, ωsampleIs the sampling bandwidth of the spectral response extraction, and N is the comb tooth number of the first optical frequency comb signal.
In the above technical solution, the spectral response of each channel extracted in parallel from the converted electrical signal is actually the combined response of the optical device to be measured and the measurement system, so that calibration is necessary, that is, the spectral response of the measurement system in the corresponding channel is removed from the spectral response of each channel, so as to obtain the spectral response of the optical device to be measured in each channel. In a conventional calibration method of a measurement system, the above measurement process is repeated without accessing an optical device to be measured, so as to obtain a spectral response of the measurement system in each channel. However, such a calibration scheme may cause undesirable calibration effects due to interference factors such as fluctuations in the power of the light source, changes in the measurement environment (e.g., environmental jitter, temperature changes, etc.), and the like. In order to solve the problem, the invention obtains the frequency spectrum response of the measuring system in each channel in real time by the following parallel methods: and dividing a parallel reference signal from the detection optical signal, directly performing photoelectric conversion on the reference signal, and extracting the frequency spectrum response of each channel in parallel from the converted electric signal, namely the frequency spectrum response of the measurement system in each channel. And removing the measurement result of the reference light path from the measurement results of the parallel measurement light paths, so that the common noise of the two paths can be completely eliminated. By adopting the parallel reference calibration scheme, the obtained system frequency spectrum response is not influenced by factors such as light source power fluctuation, measurement environment change and the like.
For the public to understand, the technical scheme of the invention is explained in detail by a preferred embodiment and the accompanying drawings:
The basic structure of the measuring device in this preferred embodiment is shown in fig. 1. The microwave optical frequency comb comprises an optical frequency comb module used for generating an optical frequency comb 1 and an optical frequency comb 2, a microwave source, a modulation module, a photoelectric detector 1, a photoelectric detector 2, an amplitude-phase extraction module 1, an amplitude-phase extraction module 2 and a control and data processing module. The comb teeth frequency intervals of the optical frequency comb 1 and the optical frequency comb 2 are different.
As shown in fig. 1, the modulation module modulates a microwave signal output by a microwave source to an optical frequency comb 1 to generate a multi-channel carrier-suppressed optical double-sideband signal, where each comb corresponds to one channel; then coupling the multichannel carrier suppression optical double-sideband signal with an optical frequency comb 2 to generate a multichannel asymmetric optical double-sideband signal; the multichannel asymmetric optical double-sideband signal is divided into two paths, one path is used as a detection optical signal, and the other path is used as a reference signal; in a detection light path, after a detection light signal passes through an optical device to be detected, an asymmetric light double-side-band signal of each channel carries response information such as amplitude, phase and polarization of the optical device to be detected, and after the asymmetric light double-side-band signal is converted into an electric signal by a photoelectric detector 1, the response information of each channel is extracted in parallel by an amplitude-phase extraction module 1; in a reference light path, a multichannel asymmetric light double-sideband signal is directly converted into an electric signal by a photoelectric detector 2 without passing through an optical device to be detected, and then response information of each channel is extracted in parallel by an amplitude-phase extraction module 2; and the control and data processing module removes the response of the measurement system from the combined response to obtain the frequency spectrum response of the optical device to be measured in each channel, and combines the frequency spectrum response to obtain the complete frequency spectrum response of the optical device to be measured.
The microwave source in this embodiment is a microwave frequency sweep source, and can generate a microwave frequency sweep signal.
The optical-frequency comb 1 and the optical-frequency comb 2 can be generated by using various existing optical-frequency comb generation methods, and in order to improve the quality of the generated signals and reduce the implementation cost, the optical-frequency comb module shown in fig. 2 is used to generate two optical-frequency comb signals in the present embodiment. As shown in fig. 2, an optical signal output by a light source is divided into two paths, one path passes through a modulator 1 and is modulated by a microwave source with a frequency Δ ω to generate an optical frequency comb 1 with a repetition frequency Δ ω (the generated sidebands are regarded as comb teeth of the optical frequency comb); the other path of the modulated light frequency is modulated by a microwave source with the frequency of delta omega + delta omega 'after passing through a frequency shifter (ensuring that comb teeth of two rows of light frequency combs are not overlapped on the frequency), and the light frequency comb 2 with the repetition frequency of delta omega + delta omega' is generated.
The method is completely different from a one-hall double-optical-frequency comb measuring method, the optical-frequency comb 1 is not used as a detection signal, but is modulated by a microwave source in a modulator to generate optical double-sideband signals of N (optical-frequency comb 1 comb teeth) channels, the N +/-1 order sideband signals are used as detection signals for detecting the amplitude response and the phase response of an nth channel, and the variation range of each sideband is half of the repetition frequency of the optical-frequency comb 1. Because the frequency resolution of the microwave source is very high, the measurement resolution can be greatly improved and theoretically can reach the Hz magnitude; the optical frequency comb 2 is used as a local oscillation signal, the nth comb tooth in the optical frequency comb 2 can be regarded as a fixed-frequency shift frequency of the nth channel carrier in the optical frequency comb 1, and after the optical frequency comb 2 is coupled with the optical double-sideband signals of the N channels generated by the optical frequency comb 1, the asymmetric optical double-sideband signals of the N channels can be obtained; the asymmetric optical double-sideband signal carries response information such as amplitude, phase, polarization and the like after passing through an optical device to be detected, and then is converted into an electric signal by a photoelectric detector; because the repetition frequencies of the optical frequency comb 1 and the optical frequency comb 2 are different, and the frequency difference between the +/-1 order sidebands of different channels in the asymmetric optical double-sideband signal and the carrier wave after frequency shift is different, the frequencies of the +/-1 order sidebands and the carrier wave after frequency shift are different after the two sidebands are subjected to beat frequency conversion in the photoelectric detector into electric signals, the signal aliasing of different channels is avoided, the problem that residual comb teeth and high-order sidebands introduce errors to measurement results in a measurement method based on the optical frequency comb and the single sideband of the Schmitt sensor is solved, and therefore amplitude responses and phase responses carried by detection signals of a plurality of channels can be received by an amplitude phase. And splicing the spectral responses of the channels to obtain the overall amplitude response and phase response of the to-be-detected optical device. The method can be realized by a frequency domain receiving method, namely, a vector network analyzer and other spectrum analyzers are used as an amplitude phase extraction module, so that higher signal-to-noise ratio and larger dynamic range can be realized.
In order to make the public more clearly understand the technical scheme of the invention, the following briefly introduces the measuring principle of the invention:
Two groups of optical frequency comb signals E with different comb tooth frequency intervalsOFC1and EOFC2can be expressed as:
Wherein, anAnd bnis the amplitude phi is the optical frequency comb OFC1And OFC2initial phase difference of ωstartIs OFC1Angular frequency, ω, of the first carrier (i.e. comb modulated with microwave signal)shiftIs OFC1First carrier and OFC2Frequency difference of the first carrier, Δ ω is OFC1Is the repetition frequency (i.e. comb frequency interval), Δ ω + Δ ω' is the OFC2the repetition frequency of (c). In order to arrange the detection signals converted into the electric signals according to a certain rule and eliminate the problem of frequency overlapping, the two groups of optical frequency comb signals preferably satisfy the following conditions:
|ωshift|>|(N-1)Δω′|,ifωshift<0,Δω′>0orωshift>0,Δω′<0
Wherein ω issampleis the sampling bandwidth of the amplitude and phase extraction module.
suppose that the nth optical frequency comb OFC1and OFC2can be expressed as ωnAnd ω'nHas omegan＝ωstart+(n-1)Δω，ω′n＝(ωstart+ωshift) + (n-1) Δ ω'. Optical frequency comb OFC1Carrier suppression double-sideband signal and optical frequency comb OFC generated after modulation2Coupled to become asymmetric optical double sideband signal, which can be expressed as
Wherein, ω iseIs the angular frequency of the microwave source, A-nand A+nis OFC1the nth carrier corresponds to the amplitude of the swept sideband. The asymmetric optical double sideband signal is divided into a measurement path and a reference path.
In the measuring path, the optical signal passes through the device to be measured and carries the amplitude response and the phase response of the device to be measured, and the output signal can be expressed as
Wherein H (ω) ═ Hsys(ω)·HDUT(ω),Hsys(omega) and HDUTAnd (ω) is the transfer function of the system and the device under test, respectively. After photoelectric conversion, OFC can be obtained1Spectral response on both sides of the nth carrier:
Where η is the responsivity of the photodetector.
On the reference path, the device under test transmits a response HDUT(ω) 1, the spectral response of the system can be obtained
According to the formula (6) and the formula (7), the transfer function H of the device under test can be obtainedDUT(ω)：
where H (| ω)n-ωeI) and H (omega)o+ωe) Is the device to be tested in OFC1The spectral response of the nth channel, and H (ω') is a constant. Fig. 3 shows the signals at a-E in the measuring device of fig. 1.
in order to verify the effect of the above-described apparatus, a principle verification experiment was performed, and the experimental results are shown in fig. 4 and 5. In the experiment, a sweep frequency microwave source with the bandwidth of 10GHz and an amplitude phase extraction module with the bandwidth of 10GHz are used, if 3 optical frequency combs are used, a 60GHz measurement range can be realized, if 5 optical frequency combs are used, a 100GHz measurement range can be realized, and the measurement time of the two measurement experiments is the same. It should be noted that the larger the number of optical frequency combs, the smaller the power of each optical frequency comb with a certain total power, and the dynamic range and the signal-to-noise ratio will decrease accordingly. The signal-to-noise ratio of the measurement results as shown in fig. 4 is higher than that shown in fig. 5.
Fig. 6 shows another embodiment of the spectral response measuring apparatus of the optical device of the present invention. This embodiment differs from that of figure 1 in that no parallel reference optical path is used and therefore calibration is required using conventional methods to remove the spectral response of the measurement system. The rest of the device and the basic principle are the same as the device shown in fig. 1, and the description is omitted here.

Claims (8)

1. A multichannel parallel optical device spectral response measuring method is characterized by comprising the following steps:
Step 1, obtaining a detection light signal by the following method: modulating the microwave signal to a first optical frequency comb signal to generate a multi-channel carrier suppression optical double-sideband signal, wherein each comb tooth of the first optical frequency comb signal corresponds to one channel; then, coupling the multichannel carrier suppression optical double-sideband signal with a second optical frequency comb signal to generate a multichannel asymmetric optical double-sideband signal, namely the detection optical signal; the comb tooth frequency intervals of the first optical frequency comb signal and the second optical frequency comb signal are different;
step 2, performing photoelectric conversion on the detection optical signal after passing through the optical device to be detected, and then extracting the frequency spectrum response of the optical device to be detected in each channel in parallel from the converted electric signal; the specific method for extracting the frequency spectrum response of the device to be tested in each channel in parallel is as follows: extracting the frequency spectrum response of each channel from the converted electric signals in parallel, and then respectively removing the frequency spectrum response of the measuring system in the corresponding channel from the frequency spectrum response of each channel to obtain the frequency spectrum response of the optical device to be measured in each channel;
and 3, combining the amplitude-frequency response and the phase-frequency response of the optical device to be tested on each channel into a complete frequency spectrum response of the optical device to be tested.
2. The method of claim 1, wherein the spectral response of the measurement system at each channel is obtained by the following parallel method: and dividing a parallel reference signal from the detection optical signal, directly performing photoelectric conversion on the reference signal, and extracting the frequency spectrum response of each channel in parallel from the converted electric signal, namely the frequency spectrum response of the measurement system in each channel.
3. the method of claim 1, wherein the microwave signal is a microwave swept frequency signal.
4. The method according to any of claims 1 to 3, wherein the first optical-frequency comb signal and the second optical-frequency comb signal satisfy the following condition:
|ωshift|>|(N-1)Δω′|,if ωshift<0,Δω′>0 or ωshift>0,Δω′<0
Wherein, ω isshiftis a frequency difference between a first comb tooth in the first optical frequency comb signal and a first comb tooth in the second optical frequency comb signal, Δ ω' is a frequency difference between a comb tooth frequency interval of the first optical frequency comb signal and a comb tooth frequency interval of the second optical frequency comb signal, ωsampleIs the sampling bandwidth of the spectral response extraction, and N is the comb tooth number of the first optical frequency comb signal.
5. A multi-channel parallel optical device spectral response measuring apparatus, comprising:
A detection light signal generation module for obtaining a detection light signal by: modulating the microwave signal to a first optical frequency comb signal to generate a multi-channel carrier suppression optical double-sideband signal, wherein each comb tooth of the first optical frequency comb signal corresponds to one channel; then, coupling the multichannel carrier suppression optical double-sideband signal with a second optical frequency comb signal to generate a multichannel asymmetric optical double-sideband signal, namely the detection optical signal; the comb tooth frequency intervals of the first optical frequency comb signal and the second optical frequency comb signal are different;
The microwave amplitude-phase detection module is used for performing photoelectric conversion on the detection optical signal passing through the optical device to be detected and extracting the frequency spectrum response of the optical device to be detected in each channel in parallel from the converted electric signal; the microwave amplitude and phase detection module comprises:
the first photoelectric conversion module is used for performing photoelectric conversion on the detection optical signal passing through the optical device to be detected;
The first amplitude and phase extraction module is used for extracting the frequency spectrum response of each channel in parallel from the electric signal converted by the first photoelectric conversion module;
the correction module is used for respectively removing the spectral response of the measurement system in the corresponding channel from the spectral response of each channel extracted by the first amplitude-phase extraction module to obtain the spectral response of the optical device to be measured in each channel;
And the main control unit is used for combining the amplitude-frequency response and the phase-frequency response of the optical device to be tested on each channel into a complete frequency spectrum response of the optical device to be tested.
6. the apparatus of claim 5, wherein the correction module comprises:
The second photoelectric conversion module is used for performing photoelectric conversion on one path of parallel reference signals which are separated from the detection optical signal;
And the second amplitude and phase extraction module is used for extracting the frequency spectrum response of each channel in parallel from the electric signal converted by the second photoelectric conversion module, namely the frequency spectrum response of the measurement system in each channel.
7. The apparatus of claim 5, wherein the microwave signal is a microwave swept frequency signal.
8. The apparatus according to any one of claims 5 to 7, wherein the first optical-frequency comb signal and the second optical-frequency comb signal satisfy the following condition:
|ωshift|>|(N-1)Δω′|,if ωshift<0,Δω′>0 or ωshift>0,Δω′<0
Wherein, ω isshiftis a frequency difference between a first comb tooth in the first optical frequency comb signal and a first comb tooth in the second optical frequency comb signal, Δ ω' is a frequency difference between a comb tooth frequency interval of the first optical frequency comb signal and a comb tooth frequency interval of the second optical frequency comb signal, ωsampleis the sampling bandwidth of the spectral response extraction, and N is the comb tooth number of the first optical frequency comb signal.
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