High-finesse displacement sensor and a theoretical
accelerometer model based on a fiber Fabry-Perot interferometer
Xu ZENG,Yu WU,Chang-lun HOU,Guo-guang YANG
Abstract:A displacement sensor based on the fiber Fabry-Perot(F-P)cavity was proposed in this
paper.Theoretical and experimental analyses were presented.Displacement resolution was
demonstrated by spectrum-domain experiments to obtain the dynamic range of the F-P sensor,and
a piezoelectric crystal unit(PZT)was used as the driver.The output signal was modulated by a
piezoelectric ceramic ring and demodulated by a phase-locked oscillator.The experimental results
show that the displacement resolution of the F-P sensor is less than 5 nm and the dynamic range is
more than 100μm.As acceleration is the second-order differential of displacement,an
accelerometer model was proposed using the finite element method(FEM) and ANSYS software.
Key words:Fiber Fabry-Perot(F-P)sensor,Spectrum demodulation,Micro-displacement
measurement,Accelerometer model
INTRODUCTION
Nano-and micro-scale displacement sensors have been widely used in various
fields,including micro-manipulating,micro-manufacture,precisely positioning,and so on.Several
kinds of displacement sensors have been proposed in the literature,such as the capacitive
displacement sensor,the piezoelectric displacement sensor,and the optical lever displacement
sensor.Of these techniques,a displacement sensor based on fiber optics holds the best promise for
high precision,for measuring in hostile environments,and for its immunity to electromagnetic
interference.
In this paper,a displacement sensor based on the principle of the fiber Fabry-Perot(F-
P)interferometric sensor is presented.Compared with existing fiber-optics-based displacement
sensors,the F-P sensor has the advantages of high sensitivity, small size,easy implementation,and
low cost.On the other hand,microelectromechanical system(MEMS) technology is rapidly
spreading internationally.MEMS technology has advantages over traditional mechanical
technology,especially on account of high sensitivity and compact size.Therefore,the approach of
combining MEMS technology with the interferometer measurement technique may result in a
development in microsensors.Based on this idea,we propose a novel micro-accelerometer model
consisting of a fiber F-P interferometric sensor and MEMS mass.
In Section 2 of this paper,the basic structure of a fiber F-P sensor and the experiment system
are introduced.In Section 3,the demodulation method in the spectrum domain is proposed.As
acceleration is the second-order differential of displacement,by the use of the finite element
method(FEM),a structure for the accelerometer is proposed theoretically in Section 4.In Section
5,the experimental results and error analysis are presented in both the spectrum domain and the
time domain.Finally Section 6 concludes the paper.
BASIC STRUCTURE
A typical fiber F-P sensor consists of a hollow-core tube and two fibers to form a high-
finesse cavity.Each end of the fiber is coated with a high reflective membrane.When the fiber is
used for sensing,one of the fibers is fixed,and the other one is movable.The movable fiber is fixed