Ex) Article Title, Author, Keywords
Current Optics
and Photonics
Ex) Article Title, Author, Keywords
Curr. Opt. Photon. 2023; 7(4): 378-386
Published online August 25, 2023 https://doi.org/10.3807/COPP.2023.7.4.378
Copyright © Optical Society of Korea.
Corresponding author: ^{*}zjh_mit@163.com, ORCID 0000-0003-1496-5770
This is an Open Access article distributed under the terms of the Creative Commons Attribution Non-Commercial License (http://creativecommons.org/licenses/by-nc/4.0/) which permits unrestricted non-commercial use, distribution, and reproduction in any medium, provided the original work is properly cited.
A wideband instantaneous frequency measurement (IFM) system is been proposed, designed and analyzed. Phase modulation to intensity modulation conversion is implemented based on the stimulated Brillouin scattering (SBS) effect, and the microwave frequency can be measured by detecting the change in output power. Theoretical analysis shows that the frequency measurement range can be extended to 4f_{b} by adjusting the two sweeping signals of the phase modulators with a difference of 2f_{b}. The IFM system is set up using VPI transmission maker software and the performances are simulated and analyzed. The simulation results show that the measurement range is 0.5−45.96 GHz with a maximum measurement error of less than 9.9 MHz. The proposed IFM system has a wider measurement range than the existing SBS-based IFM system.
Keywords: Instantaneous frequency measurement, Phase modulation, Stimulated Brillouin scattering
OCIS codes: (060.5625) Radio frequency photonics; (070.4340) Nonlinear optical signal processing; (130.4110) Modulators; (290.5900) Scattering, stimulated Brillouin; (350.4010) Microwaves
Instantaneous frequency measurement (IFM) technology can be used to quickly obtain the frequency information of a target for tracking, advance warning and interference purposes, and plays an important role in communications, radar and electronic warfare [1, 2]. With the development of information technology, traditional electronic frequency measurement methods have gradually failed to meet current needs due to the limitation of the electronic bottleneck. The photon-assisted microwave frequency measurement (MFM) method has received attention for its advantages of wider bandwidth, lower loss, anti-electromagnetic interference and larger measurement range [3–5]. The methods of IFM based on the stimulated Brillouin scattering (SBS) effect have been widely researched due to their adjustable frequency measurement range and lower measurement errors [6–10].
A multiple MFM scheme is proposed based on the selective conversion of phase modulation to amplitude modulation (PM-IM), which is realized by SBS. The scheme achieves frequency measurements in the 1–9 GHz range with a maximum measurement error of less than 30 MHz [11]. An approach for IFM is proposed based on a PM in combination with an IM. The measurement errors are within ±90 MHz in the frequency range of 0.5–20 GHz [12]. A chip-based approach has achieved multiple-frequency measurement by using the amplitude comparison function (ACF) with a measurement range of up to 38 GHz and a measurement error of 1 MHz [13]. A technique for the IFM is proposed based on SBS in a single-mode optical fiber to achieve multi-MFMs. The measured frequency errors are within 20 MHz within a broadband of 27 GHz [14]. A photonic multiple IFM system is presented and demonstrated based on a swept frequency silicon microring resonator (MRR). Frequency estimation in a range of 5–30 GHz with a measurement error under ±510 MHz is achieved [15]. By scanning the reference frequency during the SBS, the frequency information of the microwave signal to be measured is detected by a mapping between the total output power of the system and the reference frequency, and multi-MFM is achieved. The scheme achieves frequency measurements in the range of 21.42 GHz with a measurement error of less than 5 MHz [16]. A photonic-assisted multiple IFM approach based on SBS and frequency-to-time mapping with high accuracy and a wide frequency measurement range is proposed. The IFM from 6 to 18 GHz is achieved with a measurement error of less than ±1 MHz [17]. A MFM scheme based on SBS and an apodised fiber Bragg grating (AFBG) is proposed. By sweeping a reference frequency during the SBS process, frequency-to-power mapping between the reference frequency and the monitored output optical power of the IFM system is established. A measurement error of less than ±1 MHz within 10.68 GHz to 20 GHz is achieved [18]. In summary, many IFM methods based on SBS effects have been proposed to achieve larger measurement ranges and smaller measurement errors, but not both at the same time.
In this paper, an IFM system based on dual paths of the SBS effect has been proposed and designed. The frequency measurement range can be extended to 4
A schematic diagram of the proposed IFM system based on the dual paths of the SBS effect is shown in Fig. 1. The optical carrier
In Eq. (1),
The microwave signal
The gain and attenuation spectrums of HNLF1 and HNLF2 are shown in Figs. 2(d) and 2(e) respectively. The gain spectrum
in Eq.(2) and Eq.(3), ∆
When the SBS effect occurs, the PM output optical field can be expressed as
From Eq. (4), ignoring the direct current (DC), the output optical power can be written as
in Eq. (5),
Therefore, the output of electric field at the PD can be expressed approximately as
In Eq. (8), ℜ<
For frequency measurement, the PM output signal
As the SBS effect generates both the gain and attenuation spectrums, the signal power changes at
When the optical wavelength
As can be seen in Fig. 3(a), when
The proposed IFM system is established using VPI transmission maker software. The parameters of the components used are shown in Table 1.
TABLE 1 Parameter settings for instantaneous frequency measurement (IFM) system
Device | Parameter | Device | Parameter | ||
---|---|---|---|---|---|
LD | Power | 10 dBm | SBS | Brillouin Gain Coefficient | 5 |
Wavelength | 1,550 nm | Brillouin Frequency Shift | 11 GHz | ||
Linewidth | 10 MHz | Brillouin Linewidth | 40 | ||
PD | Responsibility | 1 A/W | EDFA | Gain | 5 dB |
DPMZM | Insert Loss | 5 dB | HNLF | Fiber Loss | 0.2 dB/km |
Extinction Ratio | 30 dB | Fiber Length | 15 km |
When the microwave signal to be measured is input to the DPMZM with steps of 1 GHz in the range of 0–45 GHz, the output power of PD1 and PD2 is recorded. Figure 4 shows the relationship between the recorded power and the unknown microwave frequencies under different swept frequencies. As can be seen in Fig. 4, the output power only changes when the input microwave frequency
When the PM swept frequencies
When the PM swept signal frequency
In addition, when the frequencies to be measured change in the range of 0.5–44 GHz, and the swept frequencies
Moreover, according to the above theoretical analysis, it is clear that the Brillouin frequency shift
As can be seen In Figs. 6 and 7, when
Furthermore, according to the theoretical analysis, the peak of the Brillouin gain spectrum from the SBS effect increases when the optical power of the pump light is higher, thus enabling the power changes to be detected more easily and further reducing the measurement error. Figure 8 shows the measurement errors of the IFM system when the wavelength is 1,550 nm while the optical powers are 10 dBm, 12 dBm, 14 dBm, and 16 dBm, respectively.
As can be seen in Fig. 8, when the optical powers are 10 dBm, 12 dBm, 14 dBm, and 16 dBm, the measurement errors are within ±9.83 MHz, ±7.69 MHz, ±6.7 MHz, and ±3.08 MHz, respectively, and the maximum measurement errors are 9.83 MHz, 9.90 MHz, 9.00 MHz, and 9.53 MHz. Therefore, it can be concluded that the measurement error of the IFM system can be reduced by increasing the power of the pump light. However, when the power is 16 dBm, with the increase of input frequency, the measurement error range is small and tends to be stable. This comes from the fact that the minimum error of the measurement system depends on the noise.
In addition, a comparison of the performances of existing IFM systems is shown in Table 2. As can be seen in Table 2, in [13], harnessing the photon and phonon interactions in a photonic chip through SBS results in an accurate estimation of multiple frequency measurement up to 38 GHz with errors lower than 1 MHz. In [15], by scanning filtering, unknown frequency information is mapped into time intervals and unknown frequencies can be derived using the frequency-to-time mapping function, which results in a measurement range from 5 to 30 GHz and an error of ±510 MHz. In [16], a simple and feasible frequency measurement scheme using dual-stage SBS and nonlinear fitting is proposed and experimentally demonstrated. The measurement error is less than 5 MHz with a broadband of 21.42 GHz. In [17], a high-accuracy microwave frequency measurement approach with two-step accuracy improvement based on the SBS effect and frequency-to-time mapping is proposed. A measurement range from 6 to 18 GHz is demonstrated with a measurement error of less than ±1 MHz. In [18], a frequency measurement scheme based on SBS and an AFBG is proposed, resulting in a measurement error of less than ±1 MHz within a range of 10.68 GHz to 20 GHz. In this paper, an IFM system based on dual paths of the SBS effect has been proposed and designed. When the PM signals
TABLE 2 Performances comparison of existing instantaneous frequency measurement (IFM) systems
Time | Technology | Measurement Range (GHz) | Measurement Error (MHz) |
---|---|---|---|
2016 | SBS on chip [13] | 9–38 | 1 |
2018 | MRR [15] | 5–30 | 510 |
2019 | SBS [16] | 0–21.42 | 5 |
2020 | SBS + DPMZM [17] | 6 –18 | 1 |
2022 | SBS + AFBG [18] | 10.68–20 | 1 |
2023 | SBS + PM (this work) | 0.5–45.96 | 9.9 |
Based on these previous results, the use of integrated optoelectronics can be considered in the future to achieve monolithic integration of the proposed dual paths of the SBS effect, thus reducing the noise of the system and improving measurement accuracy.
In conclusion, a broadband IFM system based on the dual paths of the SBS effect has been proposed, designed and simulated. By changing the swept frequencies and simultaneously detecting the two PDs output powers, the microwave frequency can be measured. The IFM system was established using VPI transmission maker Software, and the microwave frequencies from 0.5–45.96 GHz were measured with a maximum measurement error of 9.9 MHz by setting
The authors declare no conflicts of interest.
Data underlying the results presented in this paper are not publicly available at the time of publication, but may be obtained from the authors upon reasonable request.
National Natural Science Foundation of China (NSFC 62162034); Yunnan Fundamental Research Projects (2022 01AT070189).
Curr. Opt. Photon. 2023; 7(4): 378-386
Published online August 25, 2023 https://doi.org/10.3807/COPP.2023.7.4.378
Copyright © Optical Society of Korea.
Faculty of Information Engineering and Automation, Kunming University of Science and Technology, Kunming 650500, China
Correspondence to:^{*}zjh_mit@163.com, ORCID 0000-0003-1496-5770
This is an Open Access article distributed under the terms of the Creative Commons Attribution Non-Commercial License (http://creativecommons.org/licenses/by-nc/4.0/) which permits unrestricted non-commercial use, distribution, and reproduction in any medium, provided the original work is properly cited.
A wideband instantaneous frequency measurement (IFM) system is been proposed, designed and analyzed. Phase modulation to intensity modulation conversion is implemented based on the stimulated Brillouin scattering (SBS) effect, and the microwave frequency can be measured by detecting the change in output power. Theoretical analysis shows that the frequency measurement range can be extended to 4f_{b} by adjusting the two sweeping signals of the phase modulators with a difference of 2f_{b}. The IFM system is set up using VPI transmission maker software and the performances are simulated and analyzed. The simulation results show that the measurement range is 0.5−45.96 GHz with a maximum measurement error of less than 9.9 MHz. The proposed IFM system has a wider measurement range than the existing SBS-based IFM system.
Keywords: Instantaneous frequency measurement, Phase modulation, Stimulated Brillouin scattering
Instantaneous frequency measurement (IFM) technology can be used to quickly obtain the frequency information of a target for tracking, advance warning and interference purposes, and plays an important role in communications, radar and electronic warfare [1, 2]. With the development of information technology, traditional electronic frequency measurement methods have gradually failed to meet current needs due to the limitation of the electronic bottleneck. The photon-assisted microwave frequency measurement (MFM) method has received attention for its advantages of wider bandwidth, lower loss, anti-electromagnetic interference and larger measurement range [3–5]. The methods of IFM based on the stimulated Brillouin scattering (SBS) effect have been widely researched due to their adjustable frequency measurement range and lower measurement errors [6–10].
A multiple MFM scheme is proposed based on the selective conversion of phase modulation to amplitude modulation (PM-IM), which is realized by SBS. The scheme achieves frequency measurements in the 1–9 GHz range with a maximum measurement error of less than 30 MHz [11]. An approach for IFM is proposed based on a PM in combination with an IM. The measurement errors are within ±90 MHz in the frequency range of 0.5–20 GHz [12]. A chip-based approach has achieved multiple-frequency measurement by using the amplitude comparison function (ACF) with a measurement range of up to 38 GHz and a measurement error of 1 MHz [13]. A technique for the IFM is proposed based on SBS in a single-mode optical fiber to achieve multi-MFMs. The measured frequency errors are within 20 MHz within a broadband of 27 GHz [14]. A photonic multiple IFM system is presented and demonstrated based on a swept frequency silicon microring resonator (MRR). Frequency estimation in a range of 5–30 GHz with a measurement error under ±510 MHz is achieved [15]. By scanning the reference frequency during the SBS, the frequency information of the microwave signal to be measured is detected by a mapping between the total output power of the system and the reference frequency, and multi-MFM is achieved. The scheme achieves frequency measurements in the range of 21.42 GHz with a measurement error of less than 5 MHz [16]. A photonic-assisted multiple IFM approach based on SBS and frequency-to-time mapping with high accuracy and a wide frequency measurement range is proposed. The IFM from 6 to 18 GHz is achieved with a measurement error of less than ±1 MHz [17]. A MFM scheme based on SBS and an apodised fiber Bragg grating (AFBG) is proposed. By sweeping a reference frequency during the SBS process, frequency-to-power mapping between the reference frequency and the monitored output optical power of the IFM system is established. A measurement error of less than ±1 MHz within 10.68 GHz to 20 GHz is achieved [18]. In summary, many IFM methods based on SBS effects have been proposed to achieve larger measurement ranges and smaller measurement errors, but not both at the same time.
In this paper, an IFM system based on dual paths of the SBS effect has been proposed and designed. The frequency measurement range can be extended to 4
A schematic diagram of the proposed IFM system based on the dual paths of the SBS effect is shown in Fig. 1. The optical carrier
In Eq. (1),
The microwave signal
The gain and attenuation spectrums of HNLF1 and HNLF2 are shown in Figs. 2(d) and 2(e) respectively. The gain spectrum
in Eq.(2) and Eq.(3), ∆
When the SBS effect occurs, the PM output optical field can be expressed as
From Eq. (4), ignoring the direct current (DC), the output optical power can be written as
in Eq. (5),
Therefore, the output of electric field at the PD can be expressed approximately as
In Eq. (8), ℜ<
For frequency measurement, the PM output signal
As the SBS effect generates both the gain and attenuation spectrums, the signal power changes at
When the optical wavelength
As can be seen in Fig. 3(a), when
The proposed IFM system is established using VPI transmission maker software. The parameters of the components used are shown in Table 1.
TABLE 1. Parameter settings for instantaneous frequency measurement (IFM) system.
Device | Parameter | Device | Parameter | ||
---|---|---|---|---|---|
LD | Power | 10 dBm | SBS | Brillouin Gain Coefficient | 5 |
Wavelength | 1,550 nm | Brillouin Frequency Shift | 11 GHz | ||
Linewidth | 10 MHz | Brillouin Linewidth | 40 | ||
PD | Responsibility | 1 A/W | EDFA | Gain | 5 dB |
DPMZM | Insert Loss | 5 dB | HNLF | Fiber Loss | 0.2 dB/km |
Extinction Ratio | 30 dB | Fiber Length | 15 km |
When the microwave signal to be measured is input to the DPMZM with steps of 1 GHz in the range of 0–45 GHz, the output power of PD1 and PD2 is recorded. Figure 4 shows the relationship between the recorded power and the unknown microwave frequencies under different swept frequencies. As can be seen in Fig. 4, the output power only changes when the input microwave frequency
When the PM swept frequencies
When the PM swept signal frequency
In addition, when the frequencies to be measured change in the range of 0.5–44 GHz, and the swept frequencies
Moreover, according to the above theoretical analysis, it is clear that the Brillouin frequency shift
As can be seen In Figs. 6 and 7, when
Furthermore, according to the theoretical analysis, the peak of the Brillouin gain spectrum from the SBS effect increases when the optical power of the pump light is higher, thus enabling the power changes to be detected more easily and further reducing the measurement error. Figure 8 shows the measurement errors of the IFM system when the wavelength is 1,550 nm while the optical powers are 10 dBm, 12 dBm, 14 dBm, and 16 dBm, respectively.
As can be seen in Fig. 8, when the optical powers are 10 dBm, 12 dBm, 14 dBm, and 16 dBm, the measurement errors are within ±9.83 MHz, ±7.69 MHz, ±6.7 MHz, and ±3.08 MHz, respectively, and the maximum measurement errors are 9.83 MHz, 9.90 MHz, 9.00 MHz, and 9.53 MHz. Therefore, it can be concluded that the measurement error of the IFM system can be reduced by increasing the power of the pump light. However, when the power is 16 dBm, with the increase of input frequency, the measurement error range is small and tends to be stable. This comes from the fact that the minimum error of the measurement system depends on the noise.
In addition, a comparison of the performances of existing IFM systems is shown in Table 2. As can be seen in Table 2, in [13], harnessing the photon and phonon interactions in a photonic chip through SBS results in an accurate estimation of multiple frequency measurement up to 38 GHz with errors lower than 1 MHz. In [15], by scanning filtering, unknown frequency information is mapped into time intervals and unknown frequencies can be derived using the frequency-to-time mapping function, which results in a measurement range from 5 to 30 GHz and an error of ±510 MHz. In [16], a simple and feasible frequency measurement scheme using dual-stage SBS and nonlinear fitting is proposed and experimentally demonstrated. The measurement error is less than 5 MHz with a broadband of 21.42 GHz. In [17], a high-accuracy microwave frequency measurement approach with two-step accuracy improvement based on the SBS effect and frequency-to-time mapping is proposed. A measurement range from 6 to 18 GHz is demonstrated with a measurement error of less than ±1 MHz. In [18], a frequency measurement scheme based on SBS and an AFBG is proposed, resulting in a measurement error of less than ±1 MHz within a range of 10.68 GHz to 20 GHz. In this paper, an IFM system based on dual paths of the SBS effect has been proposed and designed. When the PM signals
TABLE 2. Performances comparison of existing instantaneous frequency measurement (IFM) systems.
Time | Technology | Measurement Range (GHz) | Measurement Error (MHz) |
---|---|---|---|
2016 | SBS on chip [13] | 9–38 | 1 |
2018 | MRR [15] | 5–30 | 510 |
2019 | SBS [16] | 0–21.42 | 5 |
2020 | SBS + DPMZM [17] | 6 –18 | 1 |
2022 | SBS + AFBG [18] | 10.68–20 | 1 |
2023 | SBS + PM (this work) | 0.5–45.96 | 9.9 |
Based on these previous results, the use of integrated optoelectronics can be considered in the future to achieve monolithic integration of the proposed dual paths of the SBS effect, thus reducing the noise of the system and improving measurement accuracy.
In conclusion, a broadband IFM system based on the dual paths of the SBS effect has been proposed, designed and simulated. By changing the swept frequencies and simultaneously detecting the two PDs output powers, the microwave frequency can be measured. The IFM system was established using VPI transmission maker Software, and the microwave frequencies from 0.5–45.96 GHz were measured with a maximum measurement error of 9.9 MHz by setting
The authors declare no conflicts of interest.
Data underlying the results presented in this paper are not publicly available at the time of publication, but may be obtained from the authors upon reasonable request.
National Natural Science Foundation of China (NSFC 62162034); Yunnan Fundamental Research Projects (2022 01AT070189).
TABLE 1 Parameter settings for instantaneous frequency measurement (IFM) system
Device | Parameter | Device | Parameter | ||
---|---|---|---|---|---|
LD | Power | 10 dBm | SBS | Brillouin Gain Coefficient | 5 |
Wavelength | 1,550 nm | Brillouin Frequency Shift | 11 GHz | ||
Linewidth | 10 MHz | Brillouin Linewidth | 40 | ||
PD | Responsibility | 1 A/W | EDFA | Gain | 5 dB |
DPMZM | Insert Loss | 5 dB | HNLF | Fiber Loss | 0.2 dB/km |
Extinction Ratio | 30 dB | Fiber Length | 15 km |
TABLE 2 Performances comparison of existing instantaneous frequency measurement (IFM) systems
Time | Technology | Measurement Range (GHz) | Measurement Error (MHz) |
---|---|---|---|
2016 | SBS on chip [13] | 9–38 | 1 |
2018 | MRR [15] | 5–30 | 510 |
2019 | SBS [16] | 0–21.42 | 5 |
2020 | SBS + DPMZM [17] | 6 –18 | 1 |
2022 | SBS + AFBG [18] | 10.68–20 | 1 |
2023 | SBS + PM (this work) | 0.5–45.96 | 9.9 |