Short cavity DFB fiber laser based vector hydrophone for low frequency signal detection

Photonic Sensors, Sep 2017

A short cavity distributed feedback (DFB) fiber laser is used for low frequency acoustic signal detection. Three DFB fiber lasers with different central wavelengths are chained together to make three-element vector hydrophone with proper sensitivity enhancement design, which has extensive and significant applications to underwater acoustic monitoring for the national defense, oil, gas exploration, and so on. By wavelength-phase demodulation, the lasing wavelength changes under different frequency signals can be interpreted, and the sensitivity is tested about 33 dB re pm/g. The frequency response range is rather flat from 5 Hz to 300 Hz.

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Short cavity DFB fiber laser based vector hydrophone for low frequency signal detection

Short Cavity DFB Fiber Laser Based Vector Hydrophone for Low Frequency Signal Detection Xiaolei ZHANG 0 Faxiang ZHANG 0 Shaodong JIANG 0 Li MIN 0 Ming LI 0 Gangding PENG 0 Jiasheng NI 0 Chang WANG 0 Corresponding author: Chang WANG 0 0 Shandong Key Laboratory of Optical Fiber Sensing & Techonology, Laser Institute of Shandong Academy of Science , China, Jinan, 250014 , China A short cavity distributed feedback (DFB) fiber laser is used for low frequency acoustic signal detection. Three DFB fiber lasers with different central wavelengths are chained together to make three-element vector hydrophone with proper sensitivity enhancement design, which has extensive and significant applications to underwater acoustic monitoring for the national defense, oil, gas exploration, and so on. By wavelength-phase demodulation, the lasing wavelength changes under different frequency signals can be interpreted, and the sensitivity is tested about 33 dB re pm/g. The frequency response range is rather flat from 5 Hz to 300 Hz. Short cavity distributed feedback fiber laser; vector hydrophone; frequency response; phase noise; sensitivity 1. Introduction The underwater seismic wave stimulated by ship noise or marine meteorology environment has significant application prospects to underwater target detection, mine fuze design, ocean dynamic monitoring, etc. The current anti-submarine hydrophone has been challenged by radiation noise decrease of marine [ 1, 2 ]. In oceanography, the low frequency and ultra-low frequency acoustic signal has little attenuation and better space time coherence in propagation. As a result, deep research on low frequency towed line array and seabed fixed line array has become a popular topic [3]. Traditional piezoelectric ceramic hydrophone requires underwater electrical equipment and cable for multiplexing, data transferring, and power supplying, which is expensive and heavy, and has underwater sealing problems. The hydrophone array, used for low frequency signal detection, usually has huge volume, which causes various inconveniences in engineering application and cost increase. All-fiber hydrophone array has no electric equipment underwater, large multiplexing capability, and anti-electromagnetic interference. Fiber vector hydrophone measures the three orthogonal components synchronously and concurrently of the acoustic pressure and particle velocity at a certain point of the sound field. Compared with the pressure hydrophone, the vector hydrophone obtains more information and provides more possibilities for subsequent data processing, which is crucial to low frequency signal acquisition, long-distance target detection, and location [ 4–6 ]. Many researches on fiber-optic flexural disk accelerometers have been reported in recent decades [ 7, 8 ], while fiber laser based accelerometers have become more and more attractive on account of high resolution and small volume [ 9, 10 ]. We use a short cavity distributed feedback (DFB) fiber laser as the sensing element, to construct a vector hydrophone with a diameter of 10 cm. Theoretical and experimental analyses have been carried out to illustrate a flat response from 5 Hz to 300 Hz. 2. Design and theory Three identity DFB fiber laser accelerators are assembled together to construct three-element co-oscillating type vector hydrophone as shown in Fig. 1. To control its attitude in water, the other three non-active accelerators are amounted therein to maintain balance. The diameter of the vector hydrophone is 10 cm, and most importantly the total mass is controlled with the average density of about 1.8 times of water density, to guarantee the globe oscillating in the sound field with the same amplitude and phase [ 1 ]. change. S = ∆aλ ∝ h Km (1) f0 = K m . (2) The lasing wavelength change of DFB fiber laser Δλ is transferred into phase difference change Δϕ: ∆φ = 2π nλd2 ∆λ (3) B where n is the refractive index of fiber, d is the optical path difference, and Δφ can be obtained by the phase demodulation technology. The DFB fiber laser we fabricated has a narrow linewidth of 10 kHz, which realizes the high resolution wavelength detection. 3. Experiment and analysis 3.1 Calibration system The system we applied for calibration is drawn in Fig. 3. A commercial pump source is used. A non-balanced Michelson interferometer is used to transfer wavelength change into phase difference change and detected by a photoelectric detector. Xiaolei ZHANG et al.: Short Cavity DFB Fiber Laser Based Vector Hydrophone for Low Frequency Signal Detection Then a commercial OPD4000 (optical phase demodulation) is applied together with the PGC (phase generation carrier) algorithm to restore the wavelength change [ 12 ]. A vibrostand JZ-5 is used where both the DFB fiber laser hydrophone and a standard piezoelectric accelerator are mounted. 3.2 Experimental results Theoretically, the wavelength resolution partly depends on the linewidth of DFB fiber laser, and the minimized measurable signal depends on the phase noise of the DFB fiber laser. It is indicated besides the sensor packaging design the vector hydrophone performance can be promoted by tailoring the DFB fiber laser design or fabrication parameter, such as lasing cavity length and ultraviolet (UV) exposure. Three DFB fiber lasers with different lasing wavelengths are chained together to realize a vector hydrophone, which are 1535.03 nm, 1539.77 nm, and 1549.37 nm separately. The cavity length of the DBF fiber laser we fabricated is only 27 mm restricted to the diameter of the hydrophone cell, the phase noise is about – 120 dB, the RIN (relative intensity noise) is – 90 dB, the linewidth is about 10 kHz, and the output power balance is less than 3 dB. The DFB fiber laser vector hydrophone we have designed is calibrated by comparison with the data of the standard piezoelectric accelerator using the system described above. The acceleration sensitivity is measured to be about 40 dB re pm/g from 5 Hz to 100 Hz without damping as shown in Fig. 4. To suppress the resonance peal as well as expand the response bandwidth, an appropriate damper should be added into the system. This procedure is accomplished in experiment, because the numerical simulation has major error compared with the practical situation. Fig. 4 Frequency response under different damping factors of the DFB fiber laser hydrophone. Cases 1# and 2# apply silicon oil with the viscosity of 100 cst, 350 cst separately, while Case 3# applies silicon oil mixed of 350 cst and 800 cst. The experimental results in Fig. 4 show that the sensitivity drops about 3 dB after adding silicon oil, and the larger viscosity brings out more flat frequency response with a resonance peak being suppressed more efficiently. However, the sensitivity keeps unchanged under 100 Hz because the silicon oil we used have the viscosity of little difference. In the optimized situation of Case 3#, the flat bandwidth of response is expanded to 300 Hz successfully. The frequency responses of three elements are tested and have good consistency as shown in Fig. 5. Fig. 5 Frequency response of the three-element DFB fiber laser hydrophone. The DFB fiber laser hydrophone we designed is capable of flat response with the sensitivity of about 33 dB re pm/g from 5 Hz to 300 Hz, with the fluctuation within ± 1 dB. 4. Conclusions A three-element vector hydrophone has been manufactured by short cavity DFB fiber lasers with the narrow linewidth with the proper sensitivity enhancement design. The lasing wavelength change under different frequency signals can be interpreted by unbalanced Michelson interferometer, and the sensitivity is tested to be about 33 dB re pm/g. The frequency response range is rather flat from 5 Hz to 300 Hz. The low frequency signal detection capability allows extensive and significant applications in underwater acoustic monitoring in the national defense, oil, and gas exploration and so on. Acknowledgment This work is supported by Shandong Research and 2015GSF115006), Development National Projects Nature Science (No. Foundation (No. 61605102), and Young Science Foundation of Shandong Academy of Sciences (No. 2016QN002). Open Access This article is distributed under the terms of the Creative Commons Attribution 4.0 International License (http://creativecommons.org/ licenses/by/4.0/), which permits unrestricted use, distribution, and reproduction in any medium, provided you give appropriate credit to the original author(s) and the source, provide a link to the Creative Commons license, and indicate if changes were made. [1] Z. G. Chen , “ Marine radiation noise measurement technology based on vector hydrophone,” Master dissertation , Harbin Engineering University, Harbin, China, 2008 . [2] Y. Ma , “ Development tendency of the world ocean and the influence on china ,” International Review, 2012 , 4 : 29 - 34 . [3] R. H. Min and J. X. Xiao , “ The state and development of submarine integrated sonar systems around the world , ” Ship Science and Technology , 2013 , 35 ( 2 ): 134 - 141 . [4] A. Nehorai and E. Paldi, “ Acoustic vector-sensor array processing , ” IEEE Transactions on Signal Processing , 1994 , 42 ( 9 ): 2481 - 2491 . [5] Y. Lv , “ Research on key technologies of ultra-low frequency vector hydrophone system for subsurface buoy detection , ” Ph.D. dissertation , Harbin Engineering University, Harbin, China, 2010 . [6] L. F. Fu , P. X. Dou , Y. Chen , S. Q. Ma , and Z. Meng , “ The directionality of shallow ambient noise using single optical fiber vector hydrophone , ” Technical Acoustics , 2013 , 32 ( 6 ): 105 - 106 . [7] G. A. Cranch and P. J. Nash , “ High-responsivity fiber-optic flexural disk accelerometers , ” Journal of Lightwave Technology , 2000 , 18 ( 9 ): 1233 - 1243 . [8] G. Y. Chen , X. L. Zhang , G. Brambilla, and T. P. Newson , “ Theoretical and experimental demonstrations of a microfiber-based flexural disc accelerometer , ” Optics Letters , 2011 , 36 ( 18 ): 3669 - 3671 . [9] Q. Jiang , Q. M. Sui , Y. C. Xu , H. G. Du , and D. B. Hu , “ Design and experiments on distributed fiber laser hydrophone , ” Acta Photonica Sinica , 2009 , 38 ( 11 ): 2795 - 2799 . [10] L. N. Ma , Y. M. Hu , H. Luo , X. L. Zhang , and Z. Meng , “ Acoustic pressure sensitivity of Yb/ErCo-doped distributed Bragg reflection fiber laser hydrophone ,” Chinese Journal of Lasers , 2009 , 36 ( 6 ): 1473 - 1478 . [11] F. X. Zhang , J. S. Lv , S. D. Jiang , B. X. Hu , X. L. Zhang , Z. Sun , et al., “ High sensitive fiber Bragg grating micro-vibration sensor with shock resistance,” Infrared and Laser Engineering , 2016 , 45 ( 8 ): 0822002 -1- 0822002-6. [12] Q. Lin , L. H. Chen , S. Li , and X. Wu , “A high-resolution fiber optic accelerometer based on intracavity phase-generated carrier (PGC) modulation,” Measurement Science and Technology, 2011 , 22 ( 22 ): 1 - 6 .


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Xiaolei Zhang, Faxiang Zhang, Shaodong Jiang, Li Min, Ming Li, Gangding Peng, Jiasheng Ni, Chang Wang. Short cavity DFB fiber laser based vector hydrophone for low frequency signal detection, Photonic Sensors, 2017, 1-4, DOI: 10.1007/s13320-017-0453-x