Figure 2 - available via license: CC BY
Content may be subject to copyright.
The heterodyne detection system of the under-test FMCW light wave.
Source publication
Ultrafast linear frequency modulated continuous-wave (FMCW) lasers are a special category of CW lasers. The linear FMCW laser is the light source for many sensing applications, especially for light detection and ranging (LiDAR). However, systems for the generation of high quality linear FMCW light are limited and diverse in terms of technical appro...
Contexts in source publication
Context 1
... frequency of the FMCW light linearly sweeps over an excursion of ( − ) during a period of T from ( + ) to ( + ), where is the optical frequency of the seed DFB laser. To check the frequency sweep linearity of the FMCW light, we use a heterodyne detection system shown in Figure 2 to record a heterodyne signal that generates at an optical coupler (OC) by photonic mixing the linear FMCW light with a stable CW laser which is a tunable external cavity laser diode (TECLD). The optical frequency of the TECLD is tuned to be close to the sweep excursion of the FMCW light in the frequency domain, but fixed at a point on the left side of the sweep excursion in the frequency domain, i.e., < ( + ) (see the spectrum in the inset of Figure 2). ...
Context 2
... check the frequency sweep linearity of the FMCW light, we use a heterodyne detection system shown in Figure 2 to record a heterodyne signal that generates at an optical coupler (OC) by photonic mixing the linear FMCW light with a stable CW laser which is a tunable external cavity laser diode (TECLD). The optical frequency of the TECLD is tuned to be close to the sweep excursion of the FMCW light in the frequency domain, but fixed at a point on the left side of the sweep excursion in the frequency domain, i.e., < ( + ) (see the spectrum in the inset of Figure 2). Then, the time-frequency curve of the FMCW light generated in the system shown in Figure 1 can be obtained by an algorithm of short time Fourier transform (STFT) for example, using a personal computer (PC), based on the data collected by a pair of balanced photodetectors and a real-time OSC in the system shown in Figure 2. The under-test FMCW light could be generated from the system shown in Figure 1. ...
Context 3
... optical frequency of the TECLD is tuned to be close to the sweep excursion of the FMCW light in the frequency domain, but fixed at a point on the left side of the sweep excursion in the frequency domain, i.e., < ( + ) (see the spectrum in the inset of Figure 2). Then, the time-frequency curve of the FMCW light generated in the system shown in Figure 1 can be obtained by an algorithm of short time Fourier transform (STFT) for example, using a personal computer (PC), based on the data collected by a pair of balanced photodetectors and a real-time OSC in the system shown in Figure 2. The under-test FMCW light could be generated from the system shown in Figure 1. ...
Context 4
... where ν c is the optical frequency of the seed DFB laser. To check the frequency sweep linearity of the FMCW light, we use a heterodyne detection system shown in Figure 2 to record a heterodyne signal that generates at an optical coupler (OC) by photonic mixing the linear FMCW light with a stable CW laser which is a tunable external cavity laser diode (TECLD). The optical frequency ν L of the TECLD is tuned to be close to the sweep excursion of the FMCW light in the frequency domain, but fixed at a point on the left side of the sweep excursion in the frequency domain, i.e., ν L < (ν c + f 0 ) (see the spectrum in the inset of Figure 2). ...
Context 5
... check the frequency sweep linearity of the FMCW light, we use a heterodyne detection system shown in Figure 2 to record a heterodyne signal that generates at an optical coupler (OC) by photonic mixing the linear FMCW light with a stable CW laser which is a tunable external cavity laser diode (TECLD). The optical frequency ν L of the TECLD is tuned to be close to the sweep excursion of the FMCW light in the frequency domain, but fixed at a point on the left side of the sweep excursion in the frequency domain, i.e., ν L < (ν c + f 0 ) (see the spectrum in the inset of Figure 2). Then, the time-frequency curve of the FMCW light generated in the system shown in Figure 1 can be obtained by an algorithm of short time Fourier transform (STFT) for example, using a personal computer (PC), based on the data collected by a pair of balanced photodetectors and a real-time OSC in the system shown in Figure 2. Sensors 2020, 20, x 5 of 13 ...
Context 6
... optical frequency ν L of the TECLD is tuned to be close to the sweep excursion of the FMCW light in the frequency domain, but fixed at a point on the left side of the sweep excursion in the frequency domain, i.e., ν L < (ν c + f 0 ) (see the spectrum in the inset of Figure 2). Then, the time-frequency curve of the FMCW light generated in the system shown in Figure 1 can be obtained by an algorithm of short time Fourier transform (STFT) for example, using a personal computer (PC), based on the data collected by a pair of balanced photodetectors and a real-time OSC in the system shown in Figure 2. Sensors 2020, 20, x 5 of 13 ...
Context 7
... devices and equipment we used in our generation system (see Figure 1) and detection system (see Figure 2) are listed as follows: In Figure 1, the seed laser of the under-test FMCW light source is a DFB laser with a linewidth of about 20 MHz at the wavelength of 1550 nm. The electronic linear FMCW signal is generated from the AWG (Keysight, M8195A, sampling rate of 65 GSa/s) with peak-to-peak amplitude = 1V, a sweep excursion from = 5 GHz to = 25 GHz in a period T = 4 μs. ...
Context 8
... the sweep excursion is equal to 20 GHz and the sweep rate is equal to 5000 THz/s. In Figure 2 the CW laser (TECLD, Keysight, 81606A) with a linewidth of less than 100 Hz, output power of 12 dBm, is tuned carefully to let ( − ) be equal to 5.0 GHz. The tunable optical filter (Santec-OTF-350, minimum bandpass of 0.1 nm, 12.5 GHz @1550 nm) is set to be centered at 1550 nm with an appropriate bandwidth. ...
Context 9
... measurement results are shown in Figure 3. The heterodyne signal between the FMCW light generated by the system shown in Figure 1 and a CW laser (TECLD) is recorded by the OSC (see Figure 2), and then plotted in Figure 3a. There are some intensity ripples over the 5 periods. ...
Context 10
... an uncertainty of 50 MHz is the best result we could have at present for an ultrafast FMCW light of 5000 THz/s by using the advanced real-time OSC with an ultrahigh sampling rate of 80 GSa/s. The devices and equipment we used in our generation system (see Figure 1) and detection system (see Figure 2) are listed as follows: In Figure 1, the seed laser of the under-test FMCW light source is a DFB laser with a linewidth of about 20 MHz at the wavelength of 1550 nm. The electronic linear FMCW signal is generated from the AWG (Keysight, M8195A, sampling rate of 65 GSa/s) with peak-to-peak amplitude V PP = 1 V, a sweep excursion from f 0 = 5 GHz to f 1 = 25 GHz in a period T = 4 µs. ...
Context 11
... the sweep excursion ∆ f is equal to 20 GHz and the sweep rate γ is equal to 5000 THz/s. In Figure 2 the CW laser (TECLD, Keysight, 81606A) with a linewidth of less than 100 Hz, output power of 12 dBm, is tuned carefully to let (ν c − ν L ) be equal to 5.0 GHz. The tunable optical filter (Santec-OTF-350, minimum bandpass of 0.1 nm, 12.5 GHz @1550 nm) is set to be centered at 1550 nm with an appropriate bandwidth. ...
Similar publications
![Calculated moments of SSacf,τ\documentclass[12pt]{minimal}...](publication/359275957/figure/fig5/AS:1140231466172417@1648863774832/Calculated-moments-of-SSacf-tdocumentclass12ptminimal-usepackageamsmath_Q320.jpg)
Seismic near-fault ground motions differ from those in the far-field. They could contain large amplitude and long period velocity pulses and cause damage to structures. In the present study, we propose a new stochastic model for the pulse-like near-fault ground motions by considering the earthquake magnitude, site-to-source distance, and soil condi...
Citations
... FMCW laser interferometry technology produces a dynamic beat interference signal, and it is easy to extract the phase subdivision, phase-moving direction resolution, and interference period count in the signal. Since the extracted phase can subdivide the wavelength of a laser, the FMCW laser interferometry technology can achieve high-precision distance measurement [8,9]. ...
As an advanced optical precision ranging method, FMCW (frequency-modulated continuous-wave) laser interferometric ranging technology can achieve a large-scale and high-precision absolute distance measurement, so it has high research and application value in the field of coordinate measurement in large space. How to improve the resolution and stability of laser interferometry is a research difficulty in this technology. Based on FMCW laser interferometry relative distance technology, a method for achieving absolute distance measurement through phase comparison after repeated sampling is proposed. Using the FMCW laser distance measuring system, two interference optical paths of measuring interferometer and auxiliary interferometer are constructed, respectively. Synchronous sampling is performed on two interference signals, and the phase ratio of the two interference signals is obtained through the extracted frequency information. The optical path difference of the unknown measurement interferometer is derived from the known auxiliary interferometer information. This method uses a triangular wave modulation laser to reduce the influence of Doppler frequency shift and eliminate quantization errors. By using the fixed-point repeated sampling, the optical path difference information is quickly extracted, and the nonlinear error of laser interference frequency modulation is effectively reduced.
... Optical frequency shift (OFS) is a key function for the operation of sensing systems based on heterodyne interferometry, including distance metrology, laser Doppler velocimetry and vibrometry, or light detection and ranging (LIDAR) [1][2][3]. Today these systems are mostly large, since they still rely on free-space optical components. Their OFS unit in particular is typically based on bulky acousto-optic modulators that offer high conversion efficiency and low-noise operation, but they exhibit low flexibility in the selection of the frequency shift and require precise beam alignment at their input optical port [4,5]. ...
We demonstrate a compact heterodyne Laser Doppler Vibrometer (LDV) based on the realization of optical frequency shift in the silicon nitride photonic integration platform (TriPleX). We theoretically study, and experimentally evaluate two different photonic integrated optical frequency shifters (OFSs), utilizing serrodyne and single-sideband (SSB) modulation. Both OFSs employ stress-optic modulators (SOMs) based on the non-resonant piezoelectrical actuation of lead zirconate titanate (PZT) thin-films, deposited on top of the silicon nitride waveguides with a wafer-scale process. To improve the modulation bandwidth of the SOMs we investigate a novel configuration of the electrodes used for the actuation, where both electrodes are placed on top of the PZT layer. Using this top-top electrode configuration we report frequency shift of 100 kHz and 2.5 MHz, and suppression ratio of the unwanted sidebands of 22.1 dB and 39 dB, using the serrodyne and the SSB OFS, respectively. The best performing SOM structure induces 0.25π peak-to-peak sinusoidal phase-shift with 156 mW power dissipation at 2.5 MHz. We use the SSB-OFS in our compact LDV system to demonstrate vibration measurements in the kHz regime. The system comprises a dual-polarization coherent detector built in the PolyBoard platform, utilizing hybrid integration of InP photodiodes (PDs). High quality LDV performance with measurement of vibration frequencies up to several hundreds of kHz and displacement resolution of 10 pm are supported with our system.
... When this phenomenon occurs, the total waveform at any point at any time is determined by the superposition principle. The superposition principle states that when two or more waves overlap, the resultant shift at any point and at any moment can be found by adding the instantaneous shifts produced at that point by the individual waves if the waves were present alone (Yang et al. 2020). Thus, in principle, it can be said that the interference of light waves arises due to the superposition of two or more waves which creates new waves. ...
This study aims to develop a valid Virtual Microscopic Simulation (VMS) media used in light wave learning and evaluate the use of VMS media in increasing students’ level of understanding. The research method used in this research is research and development using the ADDIE model. The sample in this study consisted of 35 students at one of the universities in central Jakarta, Indonesia. The results showed that the development of VMS on the light wave material, when implemented, the gain test calculation increased the level of students’ understanding of 0.56 in the medium category. The results of the level of student understanding obtained complete understanding data by 52% of students understanding partly, 42% of students understanding incorrectly, and 3% of students not understanding. This shows that using VMS media on light wave material can enhance student understanding.
... Under the condition of additive white Gaussian noise channel, the codeword received by the decoding receiver is [21] ...
In order to improve the efficiency of communication network path selection, this paper combines the graph convolutional neural network to formulate the communication network path selection strategy and selects the enhanced decoding algorithm as the fixed-point decoding algorithm. For the quantization scheme based on the enhanced decoding algorithm, the selection of the fixed-point integer bit width of each operation variable in the SISO decoder is analyzed and determined by the method of statistical characteristic analysis. Moreover, this paper calculates the normalized threshold value according to the proposed state metric normalization scheme. In addition, this paper constructs an intelligent communication path selection system. Through research, it can be seen that the communication network path selection system based on graph convolutional neural network proposed in this paper can effectively improve the effect of multicommunication path selection.
... The first method is external modulation. That is, an electrical linear frequency-sweep signal is applied to an electrooptical modulator after a laser with fixed frequency [10][11][12][13]. Sometimes injection locking can also be employed [14]. ...
... Sometimes injection locking can also be employed [14]. The linearity of frequency sweep is mainly determined by the electrical frequency-sweep source [10,12]. However, an expensive microwave source and a modulator, e.g., a high-bandwidth arbitrary waveform generator (AWG) and dual-parallel Mach-Zehnder modulator, are required. ...
... In this case, at least we can say that both methods can reach a residual nonlinearity below 10 −4 . In other reported works, the residual nonlinearity of the predistortion algorithms is also in the same order of that of external modulation method [12,13]. ...
We present an iteration algorithm for generating the linear frequency sweep of a distributed feedback laser at 1550 nm both theoretically and experimentally. This iteration algorithm is convergent and can reach a desired frequency-sweep linearity with only a few iterations. Experimentally, the residual nonlinearity ${{1 {\text -}}}{r^2}$ 1 - r 2 reaches ${5.19} \times {{1}}{{{0}}^{- 8}}$ 5.19 × 1 0 − 8 , and the relative frequency error is 0.005% with only six iterations, which has already been comparable to the linearity of the linear chirp signal generated by the external modulation method.
... For fiber-based devices, Rong, J. et al. numerically simulated shaping the supercontinuum (SC) using the fiber cascading method to significantly increase the SC spectral width and flatness in silica photonic crystal fiber (PCF) [5]. To characterize linear frequency-modulated continuous-wave (FMCW) lasers, Yang, J. et al. [6] proposed a scheme for measuring the mapping relationship between instantaneous frequency and time of a FMCW laser based on a modified coherent optical spectrum analyzer (COSA) and digital signal processing (DSP) method. The authors demonstrated precisely measuring an FMCW laser at a large fast sweep rate of 5000 THz/s, while maintaining <100 kHz uncertainty. ...
It is well known that optical fiber communications support the global communication networks nowadays, which originates from Charles K [...]
We report a CMOS-compatible silicon microring enhanced avalanche photodiode based on linear defect state absorption in a p+pn+ junction, with high responsivities exceeding 1 A/W at telecommunication wavelengths.
The large photo-generated currents give rise to giant thermo-optic nonlinearity in the microring resonator, resulting in a linear photocurrent-wavelength response spanning the full free spectral range of the microring. This unique photocurrent spectrum could enable novel applications in wavelength-resolved photodetection, such as compact on-chip spectrometers, linear chirp frequency laser source characterization, and low-cost refractometric sensors without requiring precise wavelength-tunable lasers.
