基于PPESK聚合物膜的光纤Fabry-Perot声学传感器

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"基于聚合物隔膜的敏感光纤Fabry-Perot声学传感器" 文章介绍了一种用于测量气动声波的新型敏感聚合物隔膜光纤Fabry-Perot（F-P）传感器。该传感器的核心是采用了一种新颖的聚合物材料——聚对苯二氮杂酮醚砜酮（PPESK）制成的隔膜作为声学传感元件。隔膜的有效尺寸为直径4毫米、厚度6微米。由于隔膜的优良机械性能和光学特性，结合干涉计量法和强度解调技术，使得该传感器在0.1至12.7千赫兹的频率范围内实现了31毫伏/帕的系统灵敏度，并在1千赫兹时获得了29分贝的信噪比（SNR）。传感器的线性响应范围从0.35帕到2.82帕，对应于85至103分贝的声压级（SPL，参考20微帕）。这种传感器有望成为一种通用且低成本的光学微型麦克风。关键词: 空气声波，光纤F-P腔，有机膜片，光干涉，强度解调，声学传感器在本文中，作者Qiaoyun Wang和Qingxu Yu详细阐述了他们设计的聚合物隔膜传感器的工作原理和性能特点。使用PPESK材料制作的隔膜作为传感器的核心，这种材料具有良好的机械强度和光学透明性，使其在声波检测中表现优秀。F-P腔由两面反射镜构成，其中一面是隔膜，声波的压力变化导致隔膜的微小位移，从而改变腔内的光程差，通过干涉效应，可以将声波信号转化为可测量的光学信号。利用干涉计量法，即通过分析透射光的干涉图案的变化来监测隔膜的位移，可以实现对声压的精确测量。同时，为了进一步提升信号处理能力，采用了强度解调技术，这是一种常见的信号处理方法，能有效提取出由声波引起的干涉信号变化，从而提高传感器的灵敏度和信噪比。在实际应用中，传感器在宽频范围内保持高灵敏度，特别适合监测低至0.1千赫兹的气动声波。29分贝的信噪比表明传感器能够清晰地识别并分离出噪声背景下的信号，这对于气动声学研究和噪声控制至关重要。此外，其线性响应范围覆盖了常见的声压水平，使得传感器在多种环境中都有广泛的应用潜力。这项工作展示了聚合物隔膜光纤F-P传感器在声学测量领域的先进性和实用性，特别是在低成本和高性能方面，为未来的光学声学传感器设计提供了新的思路。

266 CHINESE OPTICS LETTERS / Vol. 8, No. 3 / March 10, 2010

Polymer diaphragm based sensitive ﬁber optic Fabry-Perot

acoustic sensor

Qiaoyun Wang (|||) and Qingxu Yu (uuuRRR)

∗

School of Physics and Optoelectronic Technology, Dalian University of Technology, Dalian 116023, China

∗

E-mail: yuqx@dlut.edu.cn

Received May 20, 2009

A sensitive polymer diaphragm based ﬁber Fabry-Perot (F-P) sensor for aeroacoustic wave measurement

is presented. A novel polymer material poly (phthalazinone ether sulfone ketone) (PPESK) diaphragm is

used as the acoustic sensing element. The eﬀective dimensions of the diaphragm are 4 mm in diameter and

6 µm in thickness. Owing to the good mechanical and optical features of the diaphragm and application of

the interferometric/intensity demodulation, a system sensitivity of 31 mV/Pa is achieved in the frequency

range of 0.1–12.7 kHz, and a signal-to-noise ratio (SNR) of 29 dB at 1 kHz is obtained. The linear response

of the sensor is from 0.35 to 2.82 Pa, corresponding to 85 – 103 dB sound pressure level (SPL) (re: 20

µPa). The sensor has the potential to be used as a universal and low-cost optical microphone.

OCIS co des: 060.2370, 120.2230, 050.2230.

doi: 10.3788/COL20100803.0266.

Fiber optic acoustic sensors have been researched for

decades because of the advantages over conventional

acoustic sensors, such as electrically passive, immunity

from electromagnetic interference, resistance to corro-

sion, remote sensing operation

[1]

, light weight, and small

size. Diaphragm-based extrinsic Fabry-Perot interfero-

metric (EFPI) ﬁber optic sensor, as a branch of ﬁber

optic acoustic sensors, has become a hot topic in the

acoustic signal detection due to its high sensitivity and

wide frequency response. Various kinds of diaphragm-

based EFPI ﬁb er optic sensors, such as a silica diaphragm

spliced with a silica capillary

[2−5]

, a glass or a silicon

diaphragm bonded to a silicon base

[6−8]

, and a dipped

polymer membrane on a hollow ﬁber tip

[9,10]

have been

developed, and some of these sensors are applied in the

detection of hydroacoustic waves and partial discharge in

power transformer

[8]

. But most of these sensors do not

suit aeroacoustic detection due to the mismatch of the

acoustic impedance with the sensors diaphragm.

In this letter, an ultra-sensitive diaphragm-based ﬁber

optic EFPI aeroacoustic sensor is proposed. A new poly-

mer diaphragm of poly (phthalazinone ether sulfone ke-

tone) (PPESK) is used as the sensing element. Theo-

retical analysis of the diaphragm structure and fabrica-

tion of the sensor are presented. The conﬁguration of

the diaphragm-based ﬁber optic EFPI acoustic sensor is

shown in Fig. 1. A low-ﬁnesse Fabry-Perot (F-P) inter-

ferometer is formed between the end surface of optical

ﬁber and the inner surface of PPESK diaphragm. Light

propagates along the lead-in ﬁber, and then the partial

light is reﬂected by the ﬁber end face and the inner sur-

face of diaphragm. The reﬂection light which contains

the F-P interferometric signal travels back along the same

ﬁber. For a low-ﬁnesse F-P interferometer, the reﬂected

optical intensity can be expressed by

[11,12]

= 2RI

1 − cos(

4πL

)

, (1)

where I

is the incident optical intensity, R is the reﬂec-

tivity of the ﬁb er end face and the inner surface of di-

aphragm whose refractive index is nearly the same as that

of the ﬁber core, λ is the wavelength of the light source,

and L is the length of F-P cavity. When the length of

F-P cavity changes one half of the light wavelength, the

reﬂected intensity will change a period. The relationship

between I

and L with diﬀerent wavelengths is shown

in Fig. 2. For an interferometric/intensity modulated

sensor, the initial static operating point of sensor should

be set at the quadrature point (shown in Fig. 2 as Q

points) of the sinusoidal curve.

When a pressure is applied to the diaphragm, the de-

formation of diaphragm will cause the changes of the

F-P cavity length and the reﬂected optical intensity. In

our experiment, only the diaphragm center deﬂection is

of interest. For a rigidly clamped round diaphragm, the

Fig. 1. Conﬁguration of ﬁber acoustic sensor.

Fig. 2. Relationship between the cavity length and intensity

with diﬀerent wavelengths.

1671-7694/2010/030266-04

° 2010 Chinese Optics Letters

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