CN208075789U - A kind of Brillouin light fiber sensor system strain calibrating installation - Google Patents

Abstract

The utility model discloses a strain calibration device for a Brillouin optical fiber sensing system. The utility model comprises a servo motor, a ball screw, an optical fiber holder fixing device, an optical fiber holder, a fixed base, a moving base, a fixture table, a moving slider, a grating ruler, and a grating ruler fixing device. The utility model drives the ball screw to rotate through the servo motor, so that the moving slider fixed on the guide rail produces horizontal movement, and then the single-mode bare optical fiber fixed on the moving slider produces strain displacement, and the grating ruler reads the optical fiber strain displacement, By comparing the read value with the preset value, after reaching the deceleration range, the controller brakes the servo motor to decelerate gradually, and finally reaches the preset displacement value, so that a known fixed strain is applied to the optical fiber. Compared with the prior art, the utility model has the advantages of simple structure, convenient operation, high positioning accuracy, high parallelism and straightness, and low return clearance.

Description

A Strain Calibration Device for Brillouin Optical Fiber Sensing System

technical field

The utility model relates to a calibrating device suitable for a coal mine optical fiber sensing type safety monitoring system, in particular to a strain calibrating device based on a Brillouin optical fiber sensing system.

Background technique

At present, optical fiber sensing technologies mainly include: Rayleigh scattering, Raman scattering and Brillouin scattering; Rayleigh scattering optical fiber sensing technology can only measure the loss and breakpoint of the optical fiber, but cannot measure physical quantities such as temperature and strain. Optical fiber sensing based on the principle of Mann scattering is one of the most mature technologies in distributed optical fiber sensing. The optical signal of Raman scattering is relatively weak, so it is difficult to detect, and it is only sensitive to temperature, so it is difficult to be used in applications that require stress detection. geology, building structures, etc. Brillouin scattering is sensitive to temperature and strain, which will cause the frequency shift of the original optical signal. Therefore, by measuring the frequency shift, the temperature-frequency shift coefficient and strain-frequency shift coefficient of the optical fiber can be calibrated. Yuanyuan fiber optic sensing system is superior to other sensing technologies in terms of measurement accuracy, measurement range and spatial resolution. The Brillouin scattered light signal is sensitive to temperature/strain crossover. The common method of separating temperature/strain is to realize the temperature/strain separation by detecting the frequency shift and power change of the Brillouin scattered light signal, but the power detection is easily disturbed and stable. The sensitivity is not good, and because the sensitivity coefficient of temperature to Brillouin signal frequency shift and power is much larger than the strain sensitivity coefficient, the error of frequency shift and power detection will have a great impact on the strain detection results. Therefore, in order to realize the calibration of the strain-frequency shift coefficient, there is a high requirement for the optical fiber strain calibration device.

The traditional optical fiber strain detection device stretches the optical fiber by hanging weights vertically to give a fixed tension to the optical fiber, and realizes the measurement of the optical fiber strain by detecting the Brillouin scattering frequency shift. The device provides a fixed axial force to the optical fiber through weights, and the optical fiber strain coefficient C _ε is known, by the formula F=C _ε ×Δx (where: F—force; C _ε —optical strain coefficient; Δx—optical fiber strain displacement. ) The theoretical strain displacement Δx of the optical fiber can be obtained. It can be seen from this that the device cannot directly generate a fixed strain on the optical fiber, but can only provide theoretical values, resulting in a systematic error of the device; in addition, the device converts the vertical force of the weight into a horizontal force through the pulley, and it is theoretically considered that the force in the two directions The size of the optical fiber is equal, and the horizontal force decreases due to the friction of the pulley, which causes the system error of the device; in addition, the device provides different pulling forces for the optical fiber by changing the weight, resulting in poor flexibility and small measurement range. Therefore, it is extremely important to develop a strain calibration device for Brillouin fiber optic sensing system.

Contents of the invention

The utility model aims at the inaccurate calculation of the strain-frequency shift coefficient caused by the inability to directly obtain the strain of the optical fiber in the prior art, which further affects the demodulation accuracy of the strain of the Brillouin optical fiber sensing system. The purpose of the utility model is to develop a Set the strain calibration device of the Brillouin optical fiber sensing system, by applying the known standard strain to the optical fiber, combined with the Brillouin optical fiber sensing system to obtain the frequency shift of the Brillouin scattered light signal in the optical fiber, and then obtain the strain-frequency shift coefficient, and then realize the calibration of the strain parameter of the optical fiber sensing device.

Technical scheme of the utility model:

The utility model includes a servo motor, a ball screw, an optical fiber holder fixing device, an optical fiber holder, a fixed base, a moving base, a fixture table, a moving slider, a grating ruler, and a grating ruler fixing device; two optical fiber holders The fixing parts of the fiber holder are respectively fixed on the moving slider and the fixture table to fix the bare fiber; one end of the single-mode bare fiber is fixed by the fiber holder on the moving slider, and the other end is fixed by the fiber on the fixture table. The clamper is fixed, and the bare optical fiber to be tested is in a pre-tensioned state; at this time, the initial length l of the bare optical fiber to be measured is equal to the length between the ends of the optical fiber fixing rods of the two optical fiber holders; the clamp table and The moving slider has the same height and is always fixed. The grating ruler fixing part fixes the grating ruler reading head on the moving slider. The grating ruler reading head is used to read the relative displacement of the moving slider. The servo motor drives the ball screw to rotate, Make the moving slider move axially, and then drive the single-mode bare fiber to produce a certain amount of relative displacement Δl, so as to achieve the effect of applying standard strain ε to the optical fiber. The relationship between the relative displacement Δl and the strain ε is ε=Δl/l .

Further, the optical fiber holder for fixing the optical fiber includes an optical fiber fixing member, an optical fiber fixing rod and a screw, the optical fiber fixing rod fixes the bare optical fiber through a gap, and the optical fiber fixing rod is fixed on the optical fiber fixing member through a screw.

Compared with the background technology, the beneficial effects of the utility model are:

1. Compared with the traditional optical fiber strain calibration device, the optical fiber strain calibration device in this utility model has the characteristics of high positioning accuracy, parallelism and straightness, and low return gap, and can accurately apply any standard within the measuring range to the optical fiber strain.

2. Compared with the traditional optical fiber strain calibration device, this device directly measures the relative displacement of the optical fiber, and calculates the strain through the displacement, which can meet the standard strain applied to the 2-3m optical fiber to be tested, so that the optical fiber produces a displacement of 500-15000μm , the minimum division value is 1μm.

3. In this utility model, the optical fiber holder is used to fix the single-mode bare optical fiber. The traditional way of fixing the single-mode bare optical fiber is to paste the single-mode bare optical fiber on the fixing part with instant adhesive. Compared with this, the device has the flexibility of adjustment , The characteristics of small damage to the optical fiber.

4. For the reading of the displacement and the adjustment of the operating parameters of the servo motor in the utility model, the user can adjust the relevant parameters on the software interface, and use the serial port to realize the acquisition of the displacement data. The detection results are displayed on the software interface, with high real-time performance and high detection efficiency. The detection method is simple and easy to operate, and the relative displacement of single-mode bare optical fiber is monitored in real time, so as to accurately control the size of the applied standard strain.

Description of drawings

Fig. 1 is a schematic diagram of the three-dimensional structure of the strain calibration device of the Brillouin optical fiber sensing system.

Fig. 2 is a structural diagram of the optical fiber holder of the present invention.

Fig. 3 is a design block diagram of the hardware system of the present utility model.

Fig. 4 is the flow chart of the control system of the present utility model.

Fig. 5 is a traceability path diagram of the utility model.

Detailed ways

Below in conjunction with accompanying drawing, the utility model is further described.

As shown in Figures 1 and 2, the fiber holders 8, 13 are respectively placed on the fixture table 10 and the moving slider 12 through the fiber holder fixing parts 9, 14, and are used to fix the bare optical fiber, so that the bare optical fiber to be tested is in the In a certain pre-tension state, the initial length l of the bare optical fiber to be tested is equal to the length between the ends of the fixing rods of the two optical fiber holders. The fixture table 10 is fixed on the movable base 7, and the distance between the fixture table 10 and the fixed base 6 can be changed by moving the base 7 to meet the requirements of measuring the strain of single-mode bare optical fibers with different lengths. The height of the upper surface of the fixture table 10 and the movable slider 12 is consistent And always fixed, the servo motor 1 and the reducer 2 are fixed on the fixed base 6, the ball screw 16 is placed on the fixed base 6 through the screw fixing part 11, the servo motor 1 and the reducer 2 provide axial tension for the bare optical fiber, By driving the ball screw 16 to rotate, the ball screw 16 drives the moving slider 12 to produce axial displacement along the direction of the guide rail 15, and then drives the bare optical fiber to produce a certain amount of standard displacement. The grating ruler includes the grating calibration ruler 3 and the grating ruler The reading head 4 and the grating calibration ruler 3 are fixed on the fixed base 6. The grating ruler reading head 4 is fixed on the moving slider 12 through the grating ruler fixing part 5. The grating ruler reading head 4 is used for real-time reading of the relative position of the moving slider 12. The displacement is uploaded to the host computer for data processing.

As shown in FIG. 2 , the fiber holder in this embodiment includes screws 17 , fiber fixing rods 18 , and fiber fixing pieces 19 . The optical fiber fixing rod 18 fixes the bare optical fiber through the gap, and the size of the gap is determined according to the diameter of different types of bare optical fibers, which can realize the clamping of the bare optical fiber to be tested in the device, which meets the actual needs. The optical fiber fixing rod 18 is fixed on the optical fiber fixing member 19 by the screw 17, and turning the screw 17 gives a certain radial force to the optical fiber fixing rod 18, so that it can fix the optical fiber fixing rod 18 without damaging the bare optical fiber.

As shown in Figure 3, the STM32 single-chip microcomputer controls the servo motor 1 to rotate at a preset speed at a constant speed through the PWM output, driving the ball screw 16 to rotate, and then driving the moving slider 12 and the optical fiber holder 13 to move, so that the bare optical fiber produces a standard Displacement Δl. The grating ruler reading head 4 is fixed on the moving slider 12, and is used to read the relative displacement of the moving slider, and transmit the measurement result to the STM32 single-chip microcomputer through the serial port communication circuit. By comparing the read displacement value with the preset displacement value, after reaching the deceleration range, the controller brakes the servo motor 1 to decelerate gradually, and finally reaches the preset displacement value, according to the relationship between the standard strain ε and the standard displacement l ε = Δl/l to obtain the standard strain ε, that is, to apply a known standard strain ε to the optical fiber, combine the Brillouin optical fiber sensing system to obtain the frequency shift of the Brillouin scattered light signal in the optical fiber, and then obtain the strain-frequency The shift coefficient can also be used to calibrate the strain parameters of the Brillouin fiber optic sensing system.

As shown in Figure 4, the displacement value of the moving slider and the rotational speed value of the servo motor are set on the host computer interface of the control system. The head 4 detects the relative displacement and uploads the detected value to the control system. The control system compares whether the detected value reaches the set displacement value deceleration range, brakes the servo motor to gradually decelerate, compares whether the detected value reaches the set displacement value, and brakes completely. Servo motors, this sequence of steps achieve a known standard strain on the fiber.

As shown in Figure 5, the utility model can realize the calibration of the strain parameters of the Brillouin optical fiber strain sensing system, and the strain parameters can be traced step by step to the national length reference through the device.

Claims (2)

1. A strain calibration device for a Brillouin optical fiber sensing system, including a servo motor, a ball screw, an optical fiber holder fixing device, an optical fiber holder, a fixed base, a moving base, a fixture table, a moving slider, and a grating ruler , The grating ruler fixing device is characterized in that: The two fiber holders are respectively fixed on the moving slider and the fixture table through the fiber holder fixing parts, and are used to fix the bare fiber; one end of the single-mode bare fiber is fixed by the fiber holder on the moving slider, and the other end is It is fixed by the fiber holder on the fixture table, and the bare fiber to be tested is in a pre-tensioned state; at this time, the initial length l of the bare fiber to be tested is equal to the length between the ends of the fiber fixing rods of the two fiber holders; The height of the fixture table is the same as that of the moving slider and is always fixed. The grating ruler fixing part fixes the grating ruler reading head on the moving slider. The grating ruler reading head is used to read the relative displacement of the moving slider. The servo motor passes through Drive the ball screw to rotate, make the moving slider move axially, and then drive the single-mode bare fiber to produce a certain amount of relative displacement Δl, so as to achieve the effect of applying standard strain ε to the optical fiber. The relationship between the relative displacement Δl and the strain ε It is ε=Δl/l. 2. The strain calibration device for Brillouin optical fiber sensing system according to claim 1, characterized in that: said optical fiber holder to fix the optical fiber includes an optical fiber fixing piece, an optical fiber fixing rod and a screw, and the optical fiber fixing rod is fixed through the crack For bare optical fiber, the fiber fixing rod is fixed on the fiber fixing piece by screws.