| 1. |
- Chen, Anqi, et al.
(författare)
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Highly Sensitive Graphene Oxide-based Fabry-Perot Low-frequency Acoustic Sensor With Low-coherence Polarized Demodulation Using Three-step Phase-Shifting Arctan Algorithms
- 2024
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Ingår i: Journal of Lightwave Technology. - 0733-8724 .- 1558-2213. ; In Press
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Tidskriftsartikel (refereegranskat)abstract
- Developing low-frequency acoustic senor with high sensitivity is crucial for diverse applications, ranging from seismic monitoring, military operations, to pipeline surveillance. Here, we have proposed a high-sensitivity graphene oxide (GO)-based Fabry-Perot low-frequency sensor, in which a 170 nm thick, large-area and uniformly GO film was prepared by a vacuum filtration method. To enhance the accuracy and stability of the sensor, a low-coherence interference system based on birefringent crystal blocks was designed utilizing a three-step phase-shifting arctangent algorithm. Our sensor exhibited a sensitivity of -93.48 dB re 1 rad/μPa at 6-60 Hz with a fluctuation of 0.6 dB. The minimum detectable pressure of the sensor was measured at 0.37 μPa/Hz1/2 @20 Hz with a signal to noise ratio of 135.41 dB. Overall, this sensor offers simplicity in preparation, high sensitivity, low detectable sound pressure, making it a significant asset for low-frequency acoustic applications.
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| 2. |
- Zhang, Hongxia, et al.
(författare)
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Improved low concentration gas detection system based on intracavity fiber laser
- 2011
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Ingår i: Review of Scientific Instruments. - : AIP Publishing. - 0034-6748 .- 1089-7623. ; 82:2, s. 023104-
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Tidskriftsartikel (refereegranskat)abstract
- The improvement of a low concentration gas detection system based on the intracavity fiber laser is proposed in this paper. The sensitivity of the system is deduced based on Lambert-Beer law. The optimized system was established with the gas cell made elaborately. In order to apply the wavelength sweeping technique, the fiber Bragg grating reflector was substituted by the wavelength independent Faraday rotation reflector. The sensitivity of the system for acetylene detection is reduced to less than 100 ppm by using the average of three absorption spectra. The acetylene detection coefficients of variation with different concentrations are measured. The gas measurement system is validated to detect low concentration gas effectively.
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| 3. |
- Ding, Jiazheng, et al.
(författare)
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Intra-Channel Nonlinearity Mitigation in Optical Fiber Transmission Systems Using Perturbation-Based Neural Network
- 2022
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Ingår i: Journal of Lightwave Technology. - : Institute of Electrical and Electronics Engineers (IEEE). - 0733-8724 .- 1558-2213. ; 40:21, s. 7106-7116
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Tidskriftsartikel (refereegranskat)abstract
- In this work, a perturbation-based neural network (P-NN) scheme with an embedded bidirectional long short-term memory (biLSTM) layer is investigated to compensate for the Kerr fiber nonlinearity in optical fiber communication systems. Numerical simulations have been carried out in a 32-Gbaud dual-polarization 16-ary quadrature amplitude modulation (DP-16QAM) transmission system. It is shown that this P-NN equalizer can achieve signal-to-noise ratio improvements of similar to 1.37 dB and similar to 0.80 dB, compared to the use of a linear equalizer and a single step per span (StPS) digital back propagation (DBP) scheme, respectively. The P-NN equalizer requires lower computational complexity and can effectively compensate for intra-channel nonlinearity. Meanwhile, the performance of P-NN is more robust to the distortion caused by equalization enhanced phase noise (EEPN). Furthermore, it is also found that there exists a tradeoff between the choice of modulation format and the nonlinear equalization schemes for a given transmission distance.
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| 4. |
- Xu, Tianhua, et al.
(författare)
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Analytical Investigations on Carrier Phase Recovery in Dispersion-Unmanaged n-PSK Coherent Optical Communication Systems
- 2016
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Ingår i: Photonics. - : MDPI AG. - 2304-6732. ; 3:4
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Tidskriftsartikel (refereegranskat)abstract
- Using coherent optical detection and digital signal processing, laser phase noise and equalization enhanced phase noise can be effectively mitigated using the feed-forward and feed-back carrier phase recovery approaches. In this paper, theoretical analyses of feed-back and feed-forward carrier phase recovery methods have been carried out in the long-haul high-speed n-level phase shift keying (n-PSK) optical fiber communication systems, involving a one-tap normalized least-mean-square (LMS) algorithm, a block-wise average algorithm, and a Viterbi-Viterbi algorithm. The analytical expressions for evaluating the estimated carrier phase and for predicting the bit-error-rate (BER) performance (such as the BER floors) have been presented and discussed in the n-PSK coherent optical transmission systems by considering both the laser phase noise and the equalization enhanced phase noise. The results indicate that the Viterbi-Viterbi carrier phase recovery algorithm outperforms the one-tap normalized LMS and the block-wise average algorithms for small phase noise variance (or effective phase noise variance), while the one-tap normalized LMS algorithm shows a better performance than the other two algorithms for large phase noise variance (or effective phase noise variance). In addition, the one-tap normalized LMS algorithm is more sensitive to the level of modulation formats.
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| 5. |
- Xu, Tianhua, et al.
(författare)
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Carrier phase estimation in dispersion-unmanaged optical transmission systems
- 2017
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Ingår i: Proceedings of 2017 IEEE 2nd Advanced Information Technology, Electronic and Automation Control Conference, IAEAC 2017. - : Institute of Electrical and Electronics Engineers (IEEE). - 9781467389778 ; , s. 1860-1864
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Konferensbidrag (refereegranskat)abstract
- The study on carrier phase estimation (CPE) approaches, involving a one-tap normalized least-mean-square (NLMS) algorithm, a block-wise average algorithm, and a Viterbi-Viterbi algorithm has been carried out in the long-haul high-capacity dispersion-unmanaged coherent optical systems. The close-form expressions and analytical predictions for bit-error-rate behaviors in these CPE methods have been analyzed by considering both the laser phase noise and the equalization enhanced phase noise. It is found that the Viterbi-Viterbi algorithm outperforms the one-tap NLMS and the block-wise average algorithms for a small phase noise variance (or effective phase noise variance), while the three CPE methods converge to a similar performance for a large phase noise variance (or effective phase noise variance). In addition, the differences between the three CPE approaches become smaller for higher-level modulation formats.
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| 6. |
- Xu, Tianhua, et al.
(författare)
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Close-form expression of one-tap normalized LMS carrier phase recovery in optical communication systems
- 2016
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Ingår i: Proceedings of SPIE. - : SPIE. - 9781510601550
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Konferensbidrag (refereegranskat)abstract
- The performance of long-haul high speed coherent optical fiber communication systems is significantly degraded by the laser phase noise and the equalization enhanced phase noise (EEPN). In this paper, the analysis of the one-tap normalized least-mean-square (LMS) carrier phase recovery (CPR) is carried out and the close-form expression is investigated for quadrature phase shift keying (QPSK) coherent optical fiber communication systems, in compensating both laser phase noise and equalization enhanced phase noise. Numerical simulations have also been implemented to verify the theoretical analysis. It is found that the one-tap normalized least-mean-square algorithm gives the same analytical expression for predicting CPR bit-error-rate (BER) floors as the traditional differential carrier phase recovery, when both the laser phase noise and the equalization enhanced phase noise are taken into account.
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| 7. |
- Xu, Tianhua, et al.
(författare)
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Digital Adaptive Carrier Phase Estimation in Multi-Level Phase Shift Keying Coherent Optical Communication Systems
- 2016
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Ingår i: 2016 3RD INTERNATIONAL CONFERENCE ON INFORMATION SCIENCE AND CONTROL ENGINEERING (ICISCE). - : IEEE conference proceedings. - 9781509025350 ; , s. 1293-1297
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Konferensbidrag (refereegranskat)abstract
- The analysis of adaptive carrier phase estimation is investigated in long-haul high speed n-level phase shift keying (n-PSK) optical fiber communication systems based on the one tap normalized least-mean-square (LMS) algorithm. The close form expressions for the estimated carrier phase and the bit error-rate floor have been derived in the n-PSK coherent optical transmission systems. The results show that the one-tap normalized LMS algorithm performs pretty well in the carrier phase estimation, but will be less effective with the increment of modulation levels, in the compensation of both intrinsic laser phase noise and equalization enhanced phase noise.
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| 8. |
- Xu, Tianhua, et al.
(författare)
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Phase Noise Cancellation in Coherent Communication Systems Using a Radio Frequency Pilot Tone
- 2019
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Ingår i: Applied Sciences. - : MDPI. - 2076-3417. ; 9:21
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Tidskriftsartikel (refereegranskat)abstract
- Long-haul optical fiber communication employing digital signal processing (DSP)-based dispersion compensation can be distorted by the phenomenon of equalization-enhanced phase noise (EEPN), due to the reciprocities between the dispersion compensation unit and the local oscillator (LO) laser phase noise (LPN). The impact of EEPN scales increases with the increase of the fiber dispersion, laser linewidths, symbol rates, signal bandwidths, and the order of modulation formats. In this work, the phase noise cancellation (PNC) employing a radio frequency (RF) pilot tone in coherent optical transmission systems has been investigated. A 28-Gsym/s QPSK optical transmission system with a significant EEPN has been implemented, where the carrier phase recovery (CPR) was realized using the one-tap normalized least-mean-square (NLMS) estimation and the differential phase detection (DPD), respectively. It is shown that the RF pilot tone can entirely eliminate the LPN and efficiently suppress the EEPN when it is applied prior to the CPR.
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