Continuous adjustable optical delay device

Abstract

The invention provides a wide-range device with a continuously adjustable optical path. The device comprises an SLD light source 201, a photoelectric detector 202, a coupler 203, a to-be-detected optical fiber 204, an adjustable continuous optical path multiplication device 210 and a continuous optical path scanning device 220, the continuous optical path scanning device 220 comprises a scanning reflector 223, a program control displacement table 222 and a collimator 221, light is emitted into the coupler 203 from the SLD light source 201 and is divided into two light beams by the coupler 203, one light beam enters the to-be-detected optical fiber 204, the other light beam enters the to-be-detected optical fiber 204, and the other light beam enters the to-be-detected optical fiber 204. One beam of light passes through the optical fiber to be measured and returns through the end face of the optical fiber to be measured, the other beam of light passes through the adjustable continuous optical path multiplication device 210 and the collimator 221 and irradiates on the scanning reflector 223 to return, when the optical paths of the two beams of light are matched, interference occurs, the selectable range of the adjustable continuous optical path multiplication device 210 is L-NL, the distance between the adjustable continuous optical path multiplication device 210 and the collimator 221 is L1, and the distance between the adjustable continuous optical path multiplication device 210 and the collimator 221 is L-NL. The distance between the collimator 221 and the scanning continuous optical path device 220 is L2, and L2gt; and L, continuous adjustment of the optical path in a wide-range range can be realized, and the wide-range optical fiber white light sensing device has the advantages of flexible and changeable structure, wide range and continuous adjustment of the optical path, and can meet the requirements of a long-distance optical fiber white light sensing system.

Description

(I) Technical field

[0001] The invention belongs to the technical field of optical fiber sensing, and in particular relates to a continuously adjustable optical delay device. (II) Background technology

[0002] As a high-precision absolute measurement method, white light interferometry is widely used in various physical quantities such as displacement, temperature, strain, and pressure. In white light interferometry, the fiber delay line can achieve the matching of the reference arm and the optical path by changing the length of the measuring arm, and obtain the waveform of white light interference. Compared with traditional delay technology, the fiber delay line has the advantages of fast transmission speed, large bandwidth, strong anti-interference ability, and precise and controllable time delay.

[0003] The patent document with application number CN103743552A provides a large-range optical delay device, which controls the optical switch to select the change of n different delay optical paths with fixed lengths, thereby changing the length of the optical fiber connected to the delay line, and then realizing the function of the delay line changing the optical path of the measurement arm. However, this method limits the conditions of the optical path arms between different optical switches, and therefore cannot realize the continuously adjustable function.

[0004] The present invention proposes a continuously adjustable optical delay device, which changes the optical fiber access length L, 2L, 3L...NL of the optical switch, wherein the range of the scanning continuous optical path device (220) is 0~L2, the distance between the scanning continuous optical path device (220) and the adjustable continuous optical path multiplication device (210) is L1, and the adjustable range of the method is L+L1~NL+L1+L2. (III) Summary of the invention

[0005] The object of the present invention is to provide a continuously adjustable device which can be used to prepare an optical fiber delay device with continuously adjustable optical path.

[0006] The implementation method of the present invention is as follows: the continuously adjustable device is composed of an adjustable continuous optical path multiplying device (210) and a scanning continuous optical path device (220), wherein the scanning continuous optical path device (220) has a scanning range of 0 to L2, the scanning range of the adjustable continuous optical path multiplying device (210) is L to NL, and the distance between the scanning continuous optical path device (220) and the adjustable continuous optical path multiplying device (210) is L1, so the adjustable range of the device is L+L1 to NL+L1+L2.

[0007] The continuous optical path scanning device (220) based on a continuously adjustable optical delay device proposed in the present invention is characterized in that a delayed optical signal is hit on a moving reflector (223) through a collimator (221), and the reflected light is driven by a displacement stage (222) to realize continuous optical path scanning.

[0008] The invention provides an adjustable continuous optical path multiplication device (210) in a continuously adjustable optical delay device, which realizes the switching of different optical fiber lengths in a delay optical path by switching different access optical fibers L-NL.

[0009] The principle of the present invention is as follows Figure 1 As shown in the figure, light is transmitted from the adjustable continuous optical path multiplying device (210) to the continuous optical path scanning device (220) through the optical fiber. The reflector (223) on the continuous optical path scanning device (220) receives the light signal and reflects it. By changing the length of the optical fiber connected to the adjustable continuous optical path multiplying device (210), the length of the measuring arm is changed, thereby achieving matching of the optical path with the reference arm.

[0010] Compared with the prior art, the present invention has the advantages that the continuously adjustable optical delay device prepared by the method does not limit the conditions of the optical path arms between different optical switches, and can realize the continuously adjustable function. The structure is flexible and changeable. The style of the continuous optical path scanning device (220) is not limited, and the requirements for different optical fiber sensing systems are met.

[0011] Light from an SLD light source (306) passes through a coupler (305) and is divided into two beams. One beam passes through an adjustable optical path multiplication device (301) and a triangular mirror (302) and is detected by a photoelectric detector (309) through a coupler (310). The other beam is directly detected by a photoelectric detector (308) through an optical fiber. The adjustable continuous optical path multiplication device (301) is controlled by a switch matrix to realize switching between different optical paths L, 2L, 3L, ... NL.

[0012] Light is emitted from the adjustable optical path multiplication device (420) to a scanning continuous optical path device (410) composed of an FP cavity, and the cavity length of the FP is changed by moving a programmable displacement stage (407), thereby realizing a continuous scanning function.

[0013] In order to further illustrate the basic working principle of the present invention, a more detailed description is given below in conjunction with the accompanying drawings. (IV) Description of the drawings

[0014] Figure 1 It is a schematic diagram of the principle of a continuously adjustable reflective optical delay device.

[0015] Figure 2 This is a diagram of the working principle of continuous optical path expansion.

[0016] Figure 3 It is a schematic diagram of the principle of a transmission-type continuous optical path scanning device designed using the Mach-Zehnder principle.

[0017] Figure 4 It is a schematic diagram of the principle of connecting an adjustable continuous optical path multiplication device with a continuous optical path scanning device composed of an FP cavity, a translation stage, and a collimator. (V) Specific implementation methods

[0018] The following is a more detailed description of this patent with reference to the accompanying drawings:

[0019] according to Figure 1 As shown, the photodetector (202) and the SLD light source are respectively connected to the two input ports of the coupler (203), and the white light is emitted from the SLD light source (201) to the coupler (203) and then divided into two paths, and the two output ends of the coupler (203) are respectively connected to the optical fiber to be tested (204) and the adjustable continuous optical path multiplication device (210).

[0020] Example: According to Figure 1 As shown, the present invention proposes a continuously adjustable optical delay device, wherein light first enters the adjustable continuous optical path multiplication device (210) to select the optical fiber to be connected, and the optical fiber lengths are L, 2L, 3L...NL respectively, and then the light is hit by the optical fiber to the continuous optical path scanning device (220). After reaching the reflector (223), the light is reflected back to the adjustable continuous optical path multiplication device (210) to achieve light scanning. By changing the length of the optical fiber connected to the adjustable continuous optical path multiplication device (210), continuous light scanning is achieved.

[0021] Combination Figure 1 , the minimum value of the continuous optical path scanning device (220) is 0 and the maximum value is L2, the adjustable continuous optical path multiplying device (210) can adjust the optical fiber length from L to NL, and the distance between the continuous optical path scanning device (220) and the adjustable continuous optical path multiplying device (210) is L1, wherein in order to realize the function of continuous optical path, it is necessary to satisfy L2>L, wherein the adjustable continuous optical path multiplying device (210) can realize the switching of different optical fiber lengths under the control of different optical switches.

[0022] Combination Figure 1 The principle used by the continuous optical path scanning device (220) in the figure is the reflection interference principle. In the interferometer system, the reflection interferometer system generally adopts a Michelson structure. The interference signal generated by the two-way signal in the coupler (203) passes through a reflector (223) and the end face of the optical fiber (204) to be tested and returns to the photodetector (202) for detection.

[0023] Combination Figure 1In the figure, the adjustable continuous optical path multiplying device (210) is connected to different optical switches with different lengths of optical fibers to achieve the adjustment of different optical paths. The minimum usable length is L. If the distance L1 between the scanning continuous optical path device (220) and the adjustable continuous optical path multiplying device (210) and the minimum value 0 of the continuous optical path scanning device (220) are added, the minimum adjustable length is L+L1. ​​If the distance L1 between the scanning continuous optical path device (220) and the adjustable continuous optical path multiplying device (210) and the maximum value L2 of the continuous optical path scanning device (220) are taken, the maximum adjustable length is NL+L1+L2. The continuous optical path scanning device (220) in the figure is composed of a collimator (221), a displacement stage (222), and is used for light scanning.

[0024] Combination Figure 2 When the optical path is switched, it should be ensured that the optical path related scanning arm L2 is slightly larger than the replaceable optical fiber L. This condition can ensure continuous scanning of the optical path. When the optical fiber with a length of L is connected, the range is L+L1~L+L1+L2. When it is changed to 2L, the range is 2L+L1~2L+L1+L2. And so on, a continuous optical path scanning range can be obtained.

[0025] Combination Figure 2 , light is emitted from the collimator (103) to the scanning mirror (104) and reflected. According to the conditions of white light interference, it can be known that interference will occur when the optical paths of the two lights are equal. When the adjustable continuous optical path multiplication device (210) selects to access an optical fiber with a length of L, the starting position of the scanning continuous optical path device (220) is 111 and the end point is 112. When the optical fiber with a length of 2L is selected to access, the starting position of the scanning continuous optical path device (220) is 112 and the end point is 113. When the optical fiber with a length of 3L is selected to access, the starting position of the scanning continuous optical path device (220) is 113 and the end point is 114. By analogy, the starting point of each light scan is the end point of the previous light scan, thereby completing the continuous scanning function of light.

[0026] Combination Figure 2 When the optical switch selects to access the optical fiber with a length of 2L, compared with the optical fiber with a length of L, there is an extra length L, so the starting and ending positions of the interference change. Figure 2 It can be seen that when an optical fiber with a length of L is connected, the end point of the scanning continuous optical path device (220) is at 112, and when an optical fiber with a length of 2L is connected, the starting point of the scanning continuous optical path device (220) is at 112. Therefore, the two interference signals before and after are the peak values ​​generated by the interference signals at the same position, thereby achieving continuous scanning of the optical path and improving accuracy.

[0027] Combination Figure 3In addition to the reflection-type interferometer system mentioned above, the interferometer system composed of the optical fiber delay line is divided into reflection-type interferometer and transmission-type interferometer according to the reflection or transmission of the reflector. The transmission-type interferometer is as follows: Figure 3 As shown, the Mach-Zehnder interference structure is adopted, and the matching of the two optical paths is achieved through two couplers, two photodetectors, and the function of replacing the optical fiber length of the optical switch of the adjustable continuous optical path multiplication device (301).

[0028] Combination Figure 3 The device is composed as follows: an SLD light source (306) and a photodetector (307) are connected to the input end of a coupler (305) through an optical fiber. The output end of the coupler (305) is also divided into two paths, one of which is directly connected to the input end of a coupler (310), and the other path is equipped with an adjustable continuous optical path multiplication device (301) and a triangular mirror (302). Both ends are connected to the input end of the coupler (310). The output end of the coupler is also divided into two paths. The two output ends of the coupler are respectively connected to a photodetector (308) and (309).

[0029] like Figure 3 As shown, the continuously adjustable transmission type optical delay device is different from the continuously adjustable reflection type optical delay device in that the transmission type optical delay device adopts the Mach-Zehnder principle, white light is emitted from the SLD light source (306), passes through the coupler (305), and enters the measuring arm and the interference arm respectively, wherein the measuring arm is connected to an adjustable continuous optical path multiplication device (301) and a programmable displacement stage (302), and the measuring arm is connected to the programmable displacement stage (302), and the continuous scanning of the optical path is realized by the programmable displacement stage (302), and the white light signals output by the two arms are converted into electrical signals by the photoelectric detectors (308) and (309) through the coupler (310), thereby realizing the monitoring of interference.

[0030] Combination Figure 4 The scanning continuous optical path device (410) can also be composed of an FP cavity. The device is composed as follows: an SLD light source (401) and a photodetector (402) are connected to the input end of a coupler (403) through an optical fiber. One end of the output end of the coupler (403) is connected to a reflector (404), and the other end is first connected to an adjustable continuous optical path multiplication device (420), and then connected to a scanning continuous optical path device (410) composed of an FP interference cavity. As the programmable displacement stage (407) continues to move, the output light signal is detected by the photodetector (402), thereby realizing the continuous scanning function of the optical path.

[0031] Embodiment 1: Continuously adjustable reflective optical delay device

[0032] Components and parameters are as follows:

[0033] (1) The central wavelength of the SLD light source 201 is 1550 nm, and the spectrum half width is 100 nm;

[0034] (2) The central wavelength of the coupler 203 is 1550 nm, and the splitting ratio is 50:50;

[0035] (3) The central wavelength of the optical switch 210 is 1550 nm, the repetition frequency is >10 MHZ, and the return loss is 20 dB;

[0036] (4) The working wavelength of the collimator 221 is 1550 nm, the working distance varies between 5 and 100 mm, the insertion loss is 0.3 dB, and the return loss is ≥50 dB.

[0037] (5) The rotation angle of the reflector 223 is 45° or 90°, and the polarization dependent loss PDL is 0.1 dB.

[0038] The relationship between optical fiber length and delay time is as follows:

[0039]

[0040] Where c represents the speed of light, which is 3×10 8 m / s, n represents the refractive index of light, that is, the ratio of the speed of light in a vacuum to the speed of light in the medium. The refractive index n≈1.46.

[0041] Embodiment 2: Continuously adjustable transmission type optical delay device

[0042] Compared with Example 1, most of the parameters of the optoelectronic devices are the same. The difference is that in Example 2, an additional scanning continuous optical path device is provided. Through the cooperation of the two scanning continuous optical path devices, continuous scanning of the optical path is achieved. The measurement process is as follows:

[0043] (1) The optical switch is reset and the programmable translation stage is reset to zero;

[0044] (2) The programmable translation stage selects the optical fiber to be connected;

[0045] (3) The photodetector receives the white light interference signal from the two arms of the interferometer;

[0046] (4) reading the interference signal and finding the distance between the calibration point and the starting position of the scanning continuous optical path device as L1;

[0047] (5) reading the distance L between two adjacent interference peaks of the interference signal;

[0048] (6) Control the optical switch, replace the connected optical fiber, and read the distance L between two adjacent interference peaks of the interference signal 2。

Claims

1. A continuously adjustable optical delay device, comprising: An SLD light source, a photodetector, a coupler, an optical fiber to be tested, an adjustable continuous optical path multiplication device, and a continuous optical path scanning device, wherein the continuous optical path scanning device comprises a scanning reflector, a programmable displacement stage (222), and a collimator (221), wherein the scanning continuous optical path device realizes optical path scanning by changing the position of the programmable displacement stage (222) relative to the collimator (221), and the adjustable continuous optical path multiplication device (210) realizes optical path extension by changing the length of the connected optical fiber, and the two are connected by an optical fiber to obtain the adjustable optical delay device. As the programmable displacement stage (222) moves, continuous scanning of the optical path can be achieved, and the optical path scanning range of the continuous scanning optical path device (220) is 0 to L2; the adjustable optical path multiplying device is composed of n delayed optical paths L, 2L, 3L, ... NL with different fixed lengths, the optical path between the adjustable optical path multiplying device (210) and the continuous scanning optical path device (220) is L1, the optical path range of the continuous scanning optical path device (220) is 0 to L2, and the adjustable continuous optical path multiplying device (220) can switch between different optical paths L, 2L, 3L, ... NL under the control of a switch matrix.

2. A continuously adjustable optical delay device according to claim 1, characterized in that: Light is emitted from an SLD light source (306) to a coupler 1 (305) and is divided into two paths of light. The light is divided from the SLD light source (306) into two beams after passing through the coupler (305). One beam passes through an adjustable optical path multiplication device (301) and a triangular mirror (302) and is detected by a photoelectric detector (309) through a second coupler, and the other beam is directly detected by a photoelectric detector (308) through an optical fiber. The adjustable continuous optical path multiplication device (301) is controlled by a switch matrix to realize switching between different optical paths L, 2L, 3L, ... NL.

3. A continuously adjustable optical delay device according to claim 1, characterized in that: When the delayed optical signal is hit by the scanning continuous optical path device (410) composed of the FP cavity from the adjustable optical path multiplication device (420), the cavity length of the FP is changed by moving the programmable displacement stage (407), thereby realizing a continuous scanning function.

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