CN105181112B - A kind of low fineness Fabry Perot optical fibre sound pressure sensor of diaphragm type based on Fiber Bragg Grating FBG - Google Patents

Abstract

An FBG-based diaphragm type low-precision F-P fiber optic sound pressure sensor belongs to the technical field of fiber optic sensors. The invention aims to solve the defects existing in the traditional F-P optical fiber sound pressure sensor. Including the low reflectivity FBG written in the optical fiber, the sleeve, the sensitive diaphragm on the end face of the sleeve, and the optical fiber; the FBG and the sensitive diaphragm constitute a pair of mirrors in the F-P cavity, and the distance between the optical fiber and the end face of the optical fiber to the sensitive diaphragm The air cavity together constitutes the interference cavity of the F-P sensor. The cavity length of the interference cavity has good repeatability, and the parallelism of the two mirrors of the interference cavity is high; by controlling the distance between the exit end face of the optical fiber and the sensitive diaphragm, the diaphragm The effective reflectivity is close to the same as that of FBG; the sensor adopts PGC demodulation technology, which has strong anti-interference ability to slowly changing factors such as temperature and laser wavelength drift.

Description

A low-finesse Fabry-Perot light of diaphragm type based on fiber Bragg grating Fiber Acoustic Pressure Sensor

technical field

The invention relates to a Fabry-Perot pressure sensor, in particular to a diaphragm-type low-precision Fabry-Perot optical fiber sound pressure sensor based on an optical fiber Bragg grating, belonging to the technical field of optical fiber sensors.

Background technique

Optical fiber sensor technology is an emerging technology slowly formed with the development of optical fiber and optical fiber communication. It uses light as the carrier and optical fiber as the transmission medium to realize the sensing of the measured parameters.

The traditional diaphragm-type extrinsic Fabry-Perot sensor is coated with a layer of high-reflection film on the end of the fiber as a high-reflection mirror, and the sensitive diaphragm is used as another reflector. The two reflectors form a Fabry-Perot sensor. -Perot cavity, when external factors act on the sensitive diaphragm, the vibration of the diaphragm will cause the cavity length to change, and the interferometric measurement of the external signal can be realized by demodulating this change. The cavity length of the traditional diaphragm extrinsic Fabry-Perot sensor is short, and the small processing error of the interference cavity has a great influence on the demodulation result, so the processing repeatability of the interference cavity length is relatively difficult; when the environment When the temperature changes, it will cause a slow change in the length of the interference cavity, which will deteriorate the stability and accuracy of the demodulation results; interference factors such as wavelength drift will also affect the performance of the traditional diaphragm extrinsic Fabry-Perot sensor. Demodulation accuracy and stability; the traditional diaphragm type extrinsic Fabry-Perot sensor requires two mirrors to be parallel during assembly, so assembly is difficult.

Contents of the invention

A brief overview of the invention is given below in order to provide a basic understanding of some aspects of the invention. It should be understood that this summary is not an exhaustive overview of the invention. It is not intended to identify key or critical parts of the invention nor to delineate the scope of the invention. Its purpose is merely to present some concepts in a simplified form as a prelude to the more detailed description that is discussed later.

In view of this, according to one aspect of the present invention, a diaphragm type low-precision Fabry-Perot fiber optic acoustic pressure sensor based on a fiber Bragg grating is provided to overcome the above-mentioned traditional diaphragm type extrinsic Fabry Disadvantages of the R-Perot sensor.

The present invention proposes a diaphragm type low-precision Fabry-Perot fiber optic acoustic pressure sensor based on fiber Bragg gratings, including fiber Bragg gratings written in optical fibers, sleeves, sensitive diaphragms, optical fibers, and sleeves. The sensitive diaphragm is fixed in front of the end face of the fiber; the fiber Bragg grating and the sensitive diaphragm are used as two mirrors to form a Fabry-Perot cavity, and the interference cavity of the Fabry-Perot cavity includes the fiber Bragg grating to the sensitive Optical fiber and air cavity of diaphragm.

The sensor of the present invention is insensitive to temperature changes and slow drifts in the wavelength of the laser.

The cavity length processing repeatability of the sensor interference cavity of the invention is good.

The reflection mirror of the sensor interference cavity of the present invention has high parallelism.

For the specific optimization design of the above-mentioned diaphragm type low-precision Fabry-Perot fiber optic sound pressure sensor based on fiber Bragg gratings, the distance between the fiber Bragg grating and the end face of the fiber is 6 meters, and the distance between the sensitive diaphragm and the end face of the fiber is microns order of magnitude.

For the specific optimization design of the above-mentioned diaphragm type low-precision Fabry-Perot fiber optic sound pressure sensor based on fiber Bragg gratings, the end face of the fiber has an inclination angle. Such arrangement avoids self-interference in the air cavity.

For the specific optimal design of the above-mentioned diaphragm type low-precision Fabry-Perot fiber optic sound pressure sensor based on fiber Bragg gratings, the reflectivity of the fiber Bragg gratings is between 2% and 10%.

For the above-mentioned optimized design of a diaphragm-type low-precision Fabry-Perot fiber optic sound pressure sensor based on fiber Bragg gratings, the distance between the end face of the optical fiber and the sensitive diaphragm can be adjusted. By controlling the distance between the end face of the optical fiber and the sensitive diaphragm, the effective reflectivity of the sensitive diaphragm is close to the reflectivity of the fiber Bragg grating, which has the best interference effect.

Specifically optimize the design of the above-mentioned diaphragm type low-precision Fabry-Perot fiber optic acoustic pressure sensor based on fiber Bragg gratings, the thickness of the sensitive diaphragm is 100 nanometers to 10 microns, and the diameter is 150 nanometers to 10 microns. 2.5mm.

The above-mentioned diaphragm type low-precision Fabry-Perot fiber optic acoustic pressure sensor based on fiber Bragg grating is optimized and designed. The output signal of the sensor is demodulated by the PGC phase demodulation system.

The effect achieved by the present invention is:

The invention provides a diaphragm type low-precision Fabry-Perot fiber optic sound pressure sensor based on the fiber Bragg grating, and the output signal is demodulated by a phase method. The sensor uses a sensitive diaphragm to measure the external sound pressure, the cavity length is long, the cavity length of the interference cavity has good repeatability, it is not sensitive to temperature changes and the slow drift of the laser wavelength, and its mirror is easy to assemble and has high parallelism. The demodulation result has better precision and stability.

Description of drawings

Fig. 1 is a kind of sectional schematic diagram of the specific implementation of the membrane type low-fineness Fabry-Perot fiber optic acoustic pressure sensor based on the fiber Bragg grating of the present invention;

Fig. 2 is a kind of demodulation system schematic diagram that adopts the phase demodulation method of the diaphragm type low fineness Fabry-Perot fiber optic acoustic pressure sensor based on the fiber Bragg grating of the present invention;

In the figure: 1 Fiber Bragg Grating, 2 Sleeve, 3 Sensitive Diaphragm, 4 Optical Fiber, 5 Optical Fiber End Face, 6 PGC Phase Demodulation Module, 7 Circulator, 8 A/D Converter, 9 Photoelectric Converter.

detailed description

Exemplary embodiments of the present invention will be described below with reference to the accompanying drawings. In the interest of clarity and conciseness, not all features of an actual implementation are described in this specification. It should be understood, however, that in developing any such practical embodiment, many implementation-specific decisions must be made in order to achieve the developer's specific goals, such as meeting those constraints related to the system and business, and those Restrictions may vary from implementation to implementation. Furthermore, it should be understood that development work, while potentially complex and time-consuming, would be a routine undertaking for those skilled in the art having the benefit of this disclosure.

Here, it should also be noted that, in order to avoid obscuring the present invention due to unnecessary details, only the device structure and/or processing steps closely related to the solution according to the present invention are shown in the drawings, and the Other details not relevant to the present invention are described.

An embodiment of the present invention provides a diaphragm-type low-precision Fabry-Perot fiber optic sound pressure sensor based on a fiber Bragg grating, which uses a PGC phase demodulation system for signal demodulation. The schematic diagram of the sensor structure is shown in Figure 1, and the PGC phase demodulation system is shown in Figure 2. The optical fiber sensor includes a fiber Bragg grating 1 written inside the optical fiber 4 , a sensitive diaphragm 3 located at the end face of the sleeve 2 and facing the end face 5 of the optical fiber, the optical fiber 4 , the end face 5 of the optical fiber, and the sleeve 2 . The fiber Bragg grating 1 is 6 meters away from the fiber end face 5, and the fiber Bragg grating 1 constitutes a reflector of the fiber optic sensor; the sensitive diaphragm 3 is on the order of millimeters away from the fiber end face 5, forming a fiber optic sensor Another reflector, the reflectivity of the sensitive diaphragm 3 can be changed by controlling the length of the air cavity; the optical fiber end face 5 has an inclination angle, and due to the existence of the inclination angle, interference between the optical fiber end face and the sensitive diaphragm can be avoided; The sleeve 2 is used to fix the positions of the sensitive diaphragm 3 and the optical fiber 4 .

The PGC phase demodulation system of the diaphragm fiber sensor based on fiber Bragg gratings in this embodiment is shown in FIG. 2 . Specifically: the light emitted by the light source first enters the optical fiber sensor for interference after passing through the circulator 7, and then the interfering light enters the photoelectric converter 9 through the circulator 7, and the electrical signal is collected by the A/D 8 and then connected to the PGC phase demodulation module 6. PGC phase demodulation has high sensitivity and strong anti-interference ability, and at the same time makes the optical fiber sensor insensitive to slow-changing factors such as temperature change and wavelength drift.

Although the embodiments disclosed in the present invention are as above, the content thereof is only for the convenience of understanding the technical solutions of the present invention, and is not intended to limit the present invention. Anyone skilled in the technical field to which the present invention belongs can make any modifications and changes in the form and details of implementation without departing from the core technical solution disclosed in the present invention, but the scope of protection defined by the present invention remains The scope defined by the appended claims shall prevail.

Claims (1)

1. A kind of 1. diaphragm type Fabry-Perot fiber optic sound pressure sensor based on Fiber Bragg Grating FBG, it is characterised in that：Including The Fiber Bragg Grating FBG (1) write in optical fiber (4), sleeve (2), sensitive diaphragm (3), optical fiber (4), sleeve (2) is used for will be quick Sense diaphragm (3) is fixed on the front of fiber end face (5)；Fiber Bragg Grating FBG (1) and sensitive diaphragm (3) are as two reflections Mirror forms Fabry-Perot-type cavity, and the interference cavity of Fabry-Perot-type cavity includes Fiber Bragg Grating FBG (1) to sensitive diaphragm (3) Optical fiber and air chamber；Described Fiber Bragg Grating FBG (1) is apart from (5) 6 meters of fiber end face, and sensitive diaphragm (3) is apart from optical fiber end Face (5) is micron dimension；Described fiber end face (5) has an inclination angle；The reflectivity of described Fiber Bragg Grating FBG (1) exists Between 2% to 10%；The distance between described fiber end face (5) and sensitive diaphragm (3) are adjustable；Described sensitive diaphragm (3) 100 nanometers to 10 microns of thickness, diameter are 150 nanometers to 2.5 millimeters；The output signal of sensor uses PGC phases Position demodulating system carries out signal demodulation.