CN101509789A - Guidefree optical fiber Fabry-Perot interference sensor - Google Patents

Abstract

The invention discloses a none-guidance fiber Fabry-Perot interferometric sensor, which mainly consists of a white light source, a 2*2 fiber coupler, piezoceramics, a spectrograph and a computer. Two fibers at one side of the 2*2 fiber coupler are respectively connected with the white light source and the spectrograph, and in two fibers at the other side, one is wound into a plurality of circular rings, the end part of the other fiber is cut flat to form a fiber end face and the other fiber is fixed on the piezoceramics at the position near to the fiber end face. The spectrograph and the computer are connected through a USB interface. The fiber end face approaches to the surface of a measured object under the control of the piezoceramics and the fiber end face and the surface of the measured object form a Fabry-Perot cavity resonator in between. Due to no connection between the fiber end face and the surface of the measured object, the two can do horizontal relative motion, thus causing the interferometric sensor to have very wide application.

Description

Guidefree optical fiber Fabry-Perot interference sensor

Technical field

The present invention relates to sensory field of optic fibre, be specifically related to a kind of Guidefree optical fiber Fabry-Perot interference sensor that can be used for various physical quantitys, chemistry amount, biomass measurement.

Background technology

Optical fibre Fabry-perot interference sensor (FFPIS) based on Fabry-Perot interferometer (FPI) principle was obtained significant progress in the past in more than 20 year, and its application spreads all over fields such as physics, chemistry, biology.The type of optical fibre Fabry-perot interference sensor comprises the device of intrinsic Fabry-Perot interference sensor (IFPIS), extrinsic Fabry-Perot interference sensor (EFPIS), coaxial optical fiber etalon, the interference sensor based on MEMS (micro electro mechanical system) (MEMS), film interference sensor, multi-cavity F-P interference sensor and other all kinds FFPIS.These fiber F-P interference sensors all have its characteristics and range of application separately.But they lean on, and to be that the axially-movables of two reflection end faces change Fabry-Perot-type cavity long, is used in temperature, the isoparametric measurement of stress more, is of limited application.And adopt two to reflect the structure that end faces do not have guiding, and can expand the range of application of fibre-optical F-P sensor greatly, still, up to the present yet there are no the report of relevant Guidefree optical fiber Fabry-Perot interference sensor.

Summary of the invention

The objective of the invention is at the deficiencies in the prior art, a kind of Guidefree optical fiber Fabry-Perot interference sensor is provided, the present invention can be used for the measurement of various physical quantitys, chemistry amount and biomass.

The objective of the invention is to be achieved through the following technical solutions: a kind of Guidefree optical fiber Fabry-Perot interference sensor, it mainly is made up of white light source, 2 * 2 fiber couplers, piezoelectric ceramics, spectrometer and computing machine.Two optical fiber of described 2 * 2 fiber couplers, one side connect white light source and spectrometer respectively, and in two optical fiber of opposite side, one twines into some annulus, and the flat fiber end face that forms is cut in the end of another root optical fiber, is fixed on the piezoelectric ceramics near the fiber end face place.Link to each other by USB interface between described spectrometer and the computing machine.Described fiber end face near the surface of testee, forms Fabry-Perot cavity between the surface of fiber end face and testee under the control of piezoelectric ceramics.

The invention has the beneficial effects as follows: the present invention is a kind of no guidance type fiber F-P interference sensor (UFFPIS), be do not have between its two reflectings surface fixedly connected, form Fabry-Perot cavity between fiber end face and the testee surface, the spectral signal of Computer Analysis reflected back optical fiber can obtain the Fabry-Perot-type cavity long value.Because without any connection, the two can do horizontal relative motion between fiber end face and the measured object surface, this just makes the F-P interference sensor of this structure have very widely and uses:

1. can be used for the show pattern and the roughness of some objects are carried out non-cpntact measurement.

2. vibrations that can Measuring Object.

3. fluid to be measured can be coated on the substrate, analyze the content of microorganism in the liquid by Guidefree optical fiber Fabry-Perot interference sensor fiber end face scanning substrate.

4. can be used as locating device, with the optical fiber end and the micro-nano fiber binding of Guidefree optical fiber Fabry-Perot interference sensor, the control micro-nano fiber carries out micro-nano laser capture or micro-nano laser surgey.

Description of drawings

Fig. 1 is the schematic diagram of Guidefree optical fiber Fabry-Perot interference sensor of the present invention;

Fig. 2 is the system architecture synoptic diagram of Guidefree optical fiber Fabry-Perot interference sensor of the present invention.

Embodiment

Describe the present invention below with reference to the accompanying drawings in detail, it is more obvious that purpose of the present invention and effect will become.

As shown in Figure 1, the ultimate principle of Guidefree optical fiber Fabry-Perot interference sensor of the present invention is: fiber end face 1 is cut flat, under the control of electronic control translation stage and piezoelectric ceramics,, form Fabry-Perot cavity between the surface of fiber end face 1 and testee 2 near the surface of testee 2.Because without any connection, the two can do horizontal relative motion between the surface of fiber end face 1 and testee 2, this just makes the F-P interferometer of this structure have very application prospects.

Because the reflectivity on two surfaces of Fabry-Perot cavity differs bigger, and because each object difference of measuring, surface reflectivity is not a fixed value, traditional algorithm is not suitable for being used for the long signal in demodulation chamber, therefore, the signal Processing of Guidefree optical fiber Fabry-Perot interference sensor of the present invention adopts centroid algorithm.

As shown in Figure 2, Guidefree optical fiber Fabry-Perot interference sensor of the present invention mainly is made up of white light source 3,2 * 2 fiber couplers 4, piezoelectric ceramics 5, spectrometer 6 and computing machine 7.Two optical fiber of 2 * 2 fiber couplers, 4 one sides connect white light source 3 and spectrometer 6 respectively, in two optical fiber of opposite side, one twines into the very little annulus of some radiuses to reduce the interference of parasitic light, another root optical fiber is fixed on the piezoelectric ceramics 5 near fiber end face 1 place, and fiber end face 1 is cut flat in advance with optical fiber cleaver.Link to each other by USB interface between spectrometer 6 and the computing machine 7.Fiber end face 1 near the surface of testee 2, forms Fabry-Perot cavity between the surface of fiber end face 1 and testee 2 under the control of piezoelectric ceramics 5.

Light is coupled into optical fiber from white light source 3, through entering the Fabry-Perot cavity that forms between the surface by fiber end face 1 and testee 2 behind 2 * 2 fiber couplers 4, the light signal that Fabry-Perot cavity returns enters spectrometer 6 through fiber coupler 4 once more, after spectrometer 6 is gathered spectral signal, by USB interface spectral signal is sent into computing machine 5, computing machine 5 converts spectral signal to Fabry-Perot-type cavity long L value.

The interference spectrum signal that Guidefree optical fiber Fabry-Perot interference sensor produces is comprising the long signal in chamber of Fabry-Perot cavity, and the value trace method of spectrum striped is the most frequently used long signal demodulation method in chamber.This method is to determine the level time of striped and the optical path difference (OPD) between calculating resonator cavity two reflectings surface by the position that is worth most of identification striped.Though this method has obtained to use widely, its limitation is that it needs high signal to noise ratio (S/N ratio) with correct identification fringe order, also needs high detector resolution to improve measurement sensitivity.Coming restituted signal by the Fourier transform to spectral signal also is one of common method, and key is that it can be to the multiplexed signals demodulation of multichannel Fabry-Perot interference sensor.At first, do Fourier transform then to the spectral signal uniform sampling of spectrometer output.Obtain OPD from signal frequency-domain a variety of algorithms are also arranged.The simplest be the peak value of the OPD harmonic peak in the frequency spectrum as the chamber long value, but this method is subjected to the restriction at interval of frequency domain discrete signal samples, resolution is very low.Have a kind of algorithm based on Frequency Estimation can realize very high-precision measurement, this is a kind of FA algorithm, and very high but this kind algorithm requires signal to noise ratio (S/N ratio), operand is also bigger in addition.The signal processing algorithm that also has need be predicted the precision architecture model of Fabry-Perot interference sensor, so only be suitable for fixedly Fabry-Perot interference sensor of certain structure, be not suitable for the object that Guidefree optical fiber Fabry-Perot interference sensor is measured different reflectivity.A kind of centroid algorithm of the present invention, barycenter by the long signal frequency domain of computing method Fabry-Perot-type cavity harmonic peak determines that the chamber is long, this centroid algorithm is simply quick, do not need spectrum normalization, the structural parameters that do not need sensor, do not need filtering, the system noise influence is little, has high displacement resolution.

The unique distinction of Guidefree optical fiber Fabry-Perot interference sensor of the present invention is, the reflectivity on two surfaces of Fabry-Perot cavity differs bigger, and because each object difference of measuring, surface reflectivity is not a fixed value, this just needs suitable algorithm to come the long signal in demodulation Fabry-Perot cavity chamber, Guidefree optical fiber Fabry-Perot interference sensor of the present invention has comprised the corresponding centroid signal processing algorithm, and its computing formula formula is:

$L=\frac{{\∫}_a^b\mathrm{\Ω}\left|F\left(\mathrm{j\Ω}\right)\right|\mathrm{d\Ω}}{{\∫}_a^b\left|F\left(\mathrm{j\Ω}\right)\right|\mathrm{d\Ω}}$

F (j Ω) is the Fourier transform of interference spectrum, and a and b are respectively the starting point coordinate and the terminal point coordinates of a harmonic peak curve of frequency domain.For the discrete signal of Computer Processing, fortran is:

$L=\frac{\underset{m=a}{\overset{b}{\mathrm{\Σ}}}\left({\mathrm{m\Ω}}_0\right)\×\left|F\left(m\right)\right|\×{\mathrm{\Ω}}_0}{\underset{m=a}{\overset{b}{\mathrm{\Σ}}}\left|F\left(m\right)\right|\×{\mathrm{\Ω}}_0}$

Wherein F (m) is the discrete Fourier transform (DFT) of spectrometer output spectrum signal, Ω ₀Be the sample interval of frequency domain, a is the initial sampling spot of a harmonic peak signal, and b is its termination sampling spot.

Claims (2)

1. a Guidefree optical fiber Fabry-Perot interference sensor is characterized in that, it mainly is made up of white light source, 2 * 2 fiber couplers, piezoelectric ceramics, spectrometer and computing machine.Two optical fiber of described 2 * 2 fiber couplers, one side connect white light source and spectrometer respectively, and in two optical fiber of opposite side, one twines into some annulus, and the flat fiber end face that forms is cut in the end of another root optical fiber, is fixed on the piezoelectric ceramics near the fiber end face place.Link to each other by USB interface between described spectrometer and the computing machine.

2. Guidefree optical fiber Fabry-Perot interference sensor according to claim 1, it is characterized in that, described fiber end face near the surface of testee, forms Fabry-Perot cavity between the surface of fiber end face and testee under the control of piezoelectric ceramics.

Images