Directivity Analysis and Test of a Distributed WRFBG Hydrophone Linear Array

doi:10.12382/bgxb.2024.0792

Abstract

Abstract:

A compliant distributed weak reflection fiber Bragg grating (WRFBG) hydrophone linear array with continuous spiral winding and sensitization is devised to improve the target detection performance of fiber optic hydrophone linear array.Based on the theory of elasticity,a hydrophone acoustic pressure phase sensitivity model is developed by continuously and spirally winding the optical fiber around a hollow cylinder made of high density polyethylene.If the length of optical fiber between gratings is 10m,the sensitivity of hydrophone unit is -133.99dB (re 1 rad/μPa).An anechoic water tank experimental facility is constructed for a six-element distributed WRFBG hydrophone linear array.The experimental results reveale that the average acoustic pressure sensitivity of hydrophone is -136.00dB.The overall tendency of unit directivity test curve is consistent with that of the theoretical curve.The test curves of beam response are in perfect agreement with the theoretical curves in terms of azimuth and beam width for the maximums.

Key words: weak reflection fiber Bragg grating hydrophone, beam formation, acoustic pressure sensitivity, unit directivity

CLC Number:

TN248.1

GU Hongcan, WANG Jiabei, WANG Peng, ZHU Miao, YAO Gaofei, HUANG Junbin, LÜ Jiaqing. Directivity Analysis and Test of a Distributed WRFBG Hydrophone Linear Array[J]. Acta Armamentarii, 2025, 46(9): 240792-.

Figures/Tables 16

Fig.1 Local structure of a compliant distributed WRFBG hydrophone

Fig.2 Local and overall structure of a compliant distributed WRFBG hydrophone

Fig.3 Far-field waves acting on WRFBG hydrophone

Table 1 The correspondence between γ and azimuth error in the direction of arrival of wave at 45°

γ	方位误差/(°)	γ	方位误差/(°)
100	0.08	1600	0.90
200	0.10	3200	1.80
400	0.20	6400	3.60
800	0.40	12800	7.10

Fig.4 Schematic diagram of a fiber Bragg grating hydrophone

Fig.5 1.2m-long 6 element distributed WRFBG hydrophone array

Fig.6 Interference detection waveforms of reflection signal matching of six-element distributed WRFBG hydrophone array

Fig.7 An anechoic water tank experimental facility

Fig.8 Interference waveforms of elements in the six-element array sample

Fig.9 Transmit and demodulation signals of Hydrophone 1

Fig.10 Frequency response curves of hydrophone elements in the six-element array sample

Fig.11 Element directivity curves under the effect of sound wave at different frequencies

Fig.12 Azimuth-time curves of different sound wave frequencies with an incident angle of 90°

Fig.13 Beam response curves of array at different sound wave frequencies with an incident angle of 90°

Fig.14 Beam response curves of array at different sound wave frequencies with an incident angle of 55°

Table 2 Beam widths of sound waves in different incident directions at different frequencies (°)

入射方向/(°)	类别	频率/kHz
入射方向/(°)	类别	2.500	3.125	4.000	5.000	6.300	8.000	10.000
40	测试宽度	60.0	55.0	34.0	25.0	22.0	16.0	15.0
	理论计算宽度	55.5	46.7	31.6	23.3	20.1	14.9	11.9
	差值	4.5	8.3	2.4	1.7	1.9	1.1	3.1
55	测试宽度	37.0	33.0	26.0	18.0	15.0	12.0	10.0
	理论计算宽度	40.8	32.5	24.5	17.8	14.9	11.7	9.3
	差值	-3.8	0.5	1.5	0.2	0.1	0.3	0.7
75	测试宽度	26.0	24.0	20.0	16.0	13.0	11.0	9.0
	理论计算宽度	31.8	25.4	19.7	15.8	12.4	9.9	7.9
	差值	-5.8	-1.4	0.3	0.2	0.6	1.1	1.1
90	测试宽度	30.0	24.0	18.0	15.0	12.0	10.0	8.0
	理论计算宽度	30.6	24.4	19.0	15.2	12.0	9.4	7.6
	差值	-0.6	-0.4	-1.0	-0.2	0	0.6	0.4
100	测试宽度	30.0	24.0	18.0	15.0	12.0	10.0	8.0
	理论计算宽度	30.6	24.4	19.0	15.2	12.0	9.4	7.6
	差值	-0.6	-0.4	-1.0	-0.2	0	0.6	0.4
115	测试宽度	31.0	25.0	20.0	16.0	13.0	10.0	80.
	理论计算宽度	33.9	26.9	20.9	16.5	12.9	10.2	8.2
	差值	-2.9	-1.9	-0.9	-0.5	0.1	-0.2	-0.2
135	测试宽度	50.0	33.0	28.0	23.0	20.0	15.0	21.0
	理论计算宽度	46.3	36.0	26.8	22.3	17.6	13.7	11.0
	差值	3.7	-3.0	1.2	0.7	2.4	1.3	10.0
145	测试宽度	56.0	47.0	32.0	28.0	24.0	18.0	23.0
	理论计算宽度	56.2	53.9	38.8	29.7	23.4	17.1	13.8
	差值	-0.2	-6.9	-6.8	-1.7	0.6	0.9	9.2

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