A time-multiplexed spectral domain interferometry gap measurement system and method

Abstract

The application discloses a kind of time division multiplexing spectral domain interference gap measurement system and method belonging to the technical field of gap measurement.The system includes time division multiplexing subsystem, first optical amplifier, circulator, fiber sensor, second optical amplifier, spectrometer, acquisition card;Wherein, the first port of circulator, first optical amplifier, time division multiplexing subsystem are sequentially connected, the second port of circulator is connected fiber sensor, the third port of circulator, second optical amplifier, spectrometer, acquisition card are sequentially connected;Time division multiplexing subsystem includes at least two different wavelength optical paths.The application utilizes the broadband of spectrometer and the time sequence control of pulsed laser, and the measurement frequency can be increased by more than two times, which is beneficial to capture the details and transient response of rotor operation.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of gap measurement, in particular to a time-division multiplexing spectral domain interferometric gap measurement system and method. BACKGROUND

[0002] Rotor-stator gap of aero-engine core components (rotor, blade, etc.) is one of the main factors affecting the performance and safety of equipment. Real-time measurement of rotor-stator gap can assist in monitoring the running state of equipment, improving its working efficiency and safety performance. The main gap measurement methods at present are capacitance method, eddy current method and optical interference method. Among them, capacitance method and eddy current method are indirect measurement methods, and the measurement results are easily affected by the shape and material of the measured object, and the sensor probe size is usually very large, and the corresponding opening on the casing is also large. Compared with the above two methods, optical interference method has large measurement range, high precision and small probe size, and is a new emerging measurement method. When the rotor rotates at high speed, the linear velocity can reach 800 m / s, so the measurement speed requirement is very high. Spectral domain interferometric gap measurement method is a kind of optical interference method, whose principle is to use wide spectrum light on the measured surface and the reference surface respectively, and then use a spectrometer to expand the interference light in the spectral domain to obtain interference fringes, and then obtain the gap value through the interference fringe frequency. However, due to the frame rate limitation of the image sensor of the spectrometer, the measurement frequency of this method is usually only tens of kHz to hundreds of kHz, and when the rotor rotates at high speed, the details may be lost and the high-order harmonics of the gap change cannot be obtained.

[0003] Therefore, there is a need for a time-division multiplexing spectral domain interferometric gap measurement system and method to improve the measurement frequency to capture the details and transient response of the rotor operation. SUMMARY

[0004] The purpose of the present application is to provide a time-division multiplexing spectral domain interferometric gap measurement system and method.

[0005] A time-division multiplexing spectral domain interferometric gap measurement system, comprising:

[0006] A time-division multiplexing subsystem for generating time-division multiplexed optical output to a first optical amplifier;

[0007] A first optical amplifier for amplifying light from the time-division multiplexing subsystem and outputting to a circulator;

[0008] A circulator having a first port, a second port and a third port, wherein the first port is used to receive light from the first optical amplifier; the second port is used to output light from the first optical amplifier, receive part of the light reflected by the end face of the optical fiber sensor probe and part of the light reflected or scattered by the measured surface; and the third port is used to output part of the light reflected by the end face of the optical fiber sensor probe and part of the light reflected or scattered by the measured surface;

[0009] An optical fiber sensor for converting the gap value into a measurable optical signal;

[0010] A second optical amplifier for amplifying the part of light reflected by the end face of the optical fiber sensor probe and the part of light reflected or scattered by the measured surface and outputting to the optical spectrum analyzer;

[0011] An optical spectrum analyzer for interference of the part of light reflected by the end face of the optical fiber sensor probe and the part of light reflected or scattered by the measured surface;

[0012] A collection card for collecting the interference light signal in the optical spectrum analyzer;

[0013] The time division multiplexing subsystem comprises at least two optical paths of different wavelengths, and is used for time division multiplexing the optical signals of different wavelengths to improve the measurement frequency.

[0014] As a preferred technical solution of the present application, the time division multiplexing subsystem comprises a pulse timing generating circuit, a broadband light source, an optical filter, and a beam combiner; each optical path is composed of the broadband light source and the optical filter in series; one end of each optical path is connected to the pulse timing generating circuit through the broadband light source, and the other end is connected to the input end of the beam combiner through the optical filter; the time division multiplexing subsystem is connected to the first optical amplifier through the output end of the beam combiner.

[0015] As another preferred technical solution of the present application, the time division multiplexing subsystem comprises a pulse timing generating circuit, a broadband light source, a wavelength division multiplexer, and an optical switch; one end of the pulse timing generating circuit and the wavelength division multiplexer is connected to the optical switch respectively, the other end of the wavelength division multiplexer is connected to the broadband light source, and the time division multiplexing subsystem is connected to the first optical amplifier through the optical switch; the wavelength division multiplexer and the optical switch directly form optical paths of different wavelengths.

[0016] As another preferred technical solution of the present application, the time division multiplexing subsystem comprises a pulse timing generating circuit, a broadband light source, an optical filter, a beam splitter, and an optical switch; the pulse timing generating circuit is connected to the optical switch, and each optical path passes through the optical filter; one end of the optical filter is connected to the output end of the beam splitter, and the other end is connected to the optical switch; the input end of the beam splitter is connected to the broadband light source; the time division multiplexing subsystem is connected to the first optical amplifier through the optical switch.

[0017] A time division multiplexing spectral domain interference gap measurement method, comprising the following steps:

[0018] The pulse timing circuit generates a driving signal to drive the broadband light source in the integral time of the spectrometer, so that each broadband light source is only turned on for a period of time during the integration; the light emitted by the broadband light source is filtered by the optical filter, and then becomes a beam of light after being combined by the combiner and input into the first optical amplifier for power amplification; the light output by the first optical amplifier is input into the optical fiber sensor through the circulator, and part of the light reflected by the probe end face of the optical fiber sensor is output from the third port of the circulator; the light emitted by the optical fiber sensor hits the measured surface, and part of the light reflected or scattered by the measured surface returns to the optical fiber sensor and is also output from the third port of the circulator; the part of the light reflected by the probe end face of the optical fiber sensor and the part of the light reflected or scattered by the measured surface are both power amplified by the second optical amplifier, and then the two beams of light interfere in the spectrometer, and the interference light signal is collected by the collection card.

[0019] A time-division multiplexed spectral domain interferometric gap measurement method, comprising the following steps:

[0020] The light emitted by the broadband light source is divided into different wavelengths of light by the wavelength division multiplexer, and then input into the first optical amplifier for power amplification after the optical switch, and the pulse timing circuit generates a driving signal to drive the optical switch to switch different wavelengths; the light output by the first optical amplifier is input into the optical fiber sensor through the circulator, and part of the light reflected by the probe end face of the optical fiber sensor is output from the third port of the circulator; the light emitted by the optical fiber sensor hits the measured surface, and part of the light reflected or scattered by the measured surface returns to the optical fiber sensor and is also output from the third port of the circulator; the part of the light reflected by the probe end face of the optical fiber sensor and the part of the light reflected or scattered by the measured surface are both power amplified by the second optical amplifier, and then the two beams of light interfere in the spectrometer, and the interference light signal is collected by the collection card.

[0021] A time-division multiplexed spectral domain interferometric gap measurement method, comprising the following steps:

[0022] The light emitted by the broadband light source is divided into different wavelengths of light by the wavelength division multiplexer, and then input into the first optical amplifier for power amplification after the optical switch, and the pulse timing circuit generates a driving signal to drive the optical switch to switch different wavelengths; the light output by the first optical amplifier is input into the optical fiber sensor through the circulator, and part of the light reflected by the probe end face of the optical fiber sensor is output from the third port of the circulator; the light emitted by the optical fiber sensor hits the measured surface, and part of the light reflected or scattered by the measured surface returns to the optical fiber sensor and is also output from the third port of the circulator; the part of the light reflected by the probe end face of the optical fiber sensor and the part of the light reflected or scattered by the measured surface are both power amplified by the second optical amplifier, and then the two beams of light interfere in the spectrometer, and the interference light signal is collected by the collection card.

[0023] The beneficial effects of the present application are:

[0024] The application sets M (M is an integer and M>=2) optical paths of different wavelengths in a time division multiplexing subsystem, uses the wide bandwidth of a spectrometer and the time sequence control of a pulse laser, and can measure M times of gap values in an integration time, thereby increasing the measurement frequency by M times, and being beneficial to capturing the details and transient response of rotor operation. BRIEF DESCRIPTION OF DRAWINGS

[0025] Figure 1 Structure diagram of the time division multiplexing spectral domain interference gap measurement system of the application.

[0026] Figure 2 Structure diagram of the time division multiplexing spectral domain interference gap measurement system of the application.

[0027] Figure 3 Control timing diagram of the time division multiplexing spectral domain interference gap measurement system of the application.

[0028] Figure 4 Structure diagram of the time division multiplexing spectral domain interference gap measurement system of the application.

[0029] Figure 5 Structure diagram of the time division multiplexing spectral domain interference gap measurement system of the application.

[0030] Figure 6 Control timing diagram of the time division multiplexing spectral domain interference gap measurement system of the application. DETAILED DESCRIPTION

[0031] The application provides a time division multiplexing spectral domain interference gap measurement system and method, which are further described below in combination with the drawings and specific embodiments.

[0032] Figure 1 Structure diagram of the time division multiplexing spectral domain interference gap measurement system of the application. The structure diagram includes a time division multiplexing subsystem, a first optical amplifier, a circulator, an optical fiber sensor, a second optical amplifier, a spectrometer and a collection card. The first port of the circulator, the first optical amplifier and the time division multiplexing subsystem are sequentially connected. The second port of the circulator is connected to the optical fiber sensor. The third port of the circulator, the second optical amplifier, the spectrometer and the collection card are sequentially connected. The time division multiplexing subsystem contains at least two optical paths of different wavelengths.

[0033] Embodiment one Figure 2Figure 1 is a structural schematic diagram of a time-division multiplexing spectral domain interferometric gap measurement system according to an embodiment of the present application. In the figure, a first port of a circulator, a first optical amplifier, and a time-division multiplexing subsystem are connected in sequence, a second port of the circulator is connected to a fiber sensor, a third port of the circulator, a second optical amplifier, a spectrometer, and a data acquisition card are connected in sequence; the time-division multiplexing subsystem includes a pulse timing generation circuit, a broadband light source, an optical filter, and a beam combiner; each optical path is composed of the broadband light source and the optical filter in series; one end of each optical path is connected to the pulse timing generation circuit via the broadband light source, and the other end is connected to an input end of the beam combiner via the optical filter; the time-division multiplexing subsystem is connected to the first optical amplifier via an output end of the beam combiner.

[0034] Figure 3 Figure 2 is a control timing diagram of the time-division multiplexing spectral domain interferometric gap measurement system according to the embodiment of the present application. The pulse timing circuit generates M (M≥2) driving signals sdr int (m=1~M) to drive the M broadband light sources respectively, so that each broadband light source is turned on only for a period of time T m during the integration time T of the spectrometer. The light emitted by the broadband light source m is filtered by the optical filter m and becomes light with a center wavelength of λ hm and a bandwidth of Δλ cm . After being combined by the beam combiner, I m becomes a beam of light I and is input into the first optical amplifier for power amplification. The light output by the first optical amplifier is input into the fiber sensor via the circulator, and a portion of the light is reflected by the fiber sensor probe end face and output from the third port of the circulator. The light emitted by the fiber sensor is incident on the measured surface, and a portion of the light is reflected or scattered by the measured surface and returns to the fiber sensor and is output from the third port of the circulator. The light reflected by the fiber sensor probe end face and the measured surface and returned to the circulator is usually very weak, and the second optical amplifier is used to amplify the power of the light. After amplification, the two beams of light interfere with each other in the spectrometer, and the data acquisition card collects the interference light signal. If the output spectra of the optical filters do not overlap and are all within the detection bandwidth of the spectrometer, the output signal y of the spectrometer can be written as:

[0035]

[0036] In the formula, y m (λ) (m=1~M) is the intensity of the interference signal with a center wavelength of λ 0m , n is the refractive index of the environment in which the measured gap is located, v cm is a constant, v m is the fringe contrast, d m is the measured gap value when the pulse laser of the mth laser is output, and the interference signal in the wavelength range of λ cm ±Δλ m / 2 can be analyzed to solve d mTherefore, by using pulse timing control to switch on and off different broadband light sources, within an integral time T... int The gap value was measured M times internally, increasing the measurement frequency by M times.

[0037] Example 2 Figure 4 This is a schematic diagram of the second embodiment of the time-division multiplexing spectral domain interferometric gap measurement system of the present invention. The first port of the circulator, the first optical amplifier, and the time-division multiplexing subsystem are connected sequentially. The second port of the circulator is connected to an optical fiber sensor. The third port of the circulator, the second optical amplifier, the spectrometer, and the acquisition card are connected sequentially. The time-division multiplexing subsystem includes a pulse timing generation circuit, a broadband light source, a wavelength division multiplexer, and an optical switch. One end of the pulse timing generation circuit and one end of the wavelength division multiplexer are respectively connected to the optical switch. The other end of the wavelength division multiplexer is connected to the broadband light source. The time-division multiplexing subsystem is then connected to the first optical amplifier through the optical switch. Optical paths of different wavelengths are directly formed between the wavelength division multiplexer and the optical switch.

[0038] The control timing diagram of this embodiment is as follows: Figure 6 The light emitted from the broadband light source is split into M (M≥2) different wavelengths by a wavelength division multiplexer. The pulse timing circuit integrates the light at the spectrometer during the integration time T. int The time T for generating M paths within the time limit hm drive signal sdr m (m=1~M). The center wavelength is λ. cm The bandwidth is Δλ m The light is converted into a single beam I by an optical switch, and then input into a first optical amplifier for power amplification. A pulse timing circuit generates a drive signal to drive the optical switch to switch different wavelengths. The light output from the first optical amplifier is input into the fiber optic sensor through a circulator. Part of the light reflected from the probe end face of the fiber optic sensor is output from the third port of the circulator. The light emitted from the fiber optic sensor strikes the surface under test, and part of the light reflected or scattered from the surface under test returns to the fiber optic sensor and is also output from the third port of the circulator. The part of the light reflected from the probe end face of the fiber optic sensor and the part of the light reflected or scattered from the surface under test are both amplified by a second optical amplifier. Then, the two beams interfere at the spectrometer, and the acquisition card collects the interference light signal. The spectrometer output signal y is written as:

[0039]

[0040] In the formula, y 0m (λ) (m=1~M) is the center wavelength λ cm The interference signal intensity, n is the refractive index of the environment where the gap being measured is located, and v is a constant; m For stripe contrast, d m Let λ be the measured gap value when the m-th laser outputs a pulsed laser, and λ be analyzed. cm ±Δλ mThe interference signal in the / 2 wavelength range can be solved to obtain d. m Therefore, by using pulse timing control of the optical switch, within an integration time T int The gap value was measured M times internally, increasing the measurement frequency by M times.

[0041] Example 3 Figure 5 This is a schematic diagram of the structure of a third embodiment of the time-division multiplexing spectral domain interferometric gap measurement system of the present invention. The first port of the circulator, the first optical amplifier, and the time-division multiplexing subsystem are connected sequentially. The second port of the circulator is connected to the fiber optic sensor, and the third port of the circulator, the second optical amplifier, the spectrometer, and the acquisition card are connected sequentially. The time-division multiplexing subsystem includes a pulse timing generation circuit, a broadband light source, an optical filter, a beam splitter, and an optical switch. The pulse timing generation circuit is connected to the optical switch, and each optical path passes through an optical filter. One end of the optical filter is connected to the output of the beam splitter, and the other end is connected to the optical switch. The input of the beam splitter is connected to the broadband light source. The time-division multiplexing subsystem is then connected to the first optical amplifier via the optical switch.

[0042] The control timing diagram of this embodiment is as follows: Figure 6 The light emitted by the broadband light source is split into M (M≥2) different wavelengths by a beam splitter, and then filtered by an optical filter to form a light with a center wavelength of λ. cm The bandwidth is Δλ m The light is converted into a beam I by an optical switch, and then input into the first optical amplifier for power amplification. The pulse timing circuit operates within the integration time T of the spectrometer. int The time T for generating M paths within the time limit hm drive signal sdr m (m=1~M) The driving optical switch switches between different wavelengths; the light output from the first optical amplifier is input into the fiber optic sensor through a circulator, and part of the light reflected from the probe end face of the fiber optic sensor is output from the third port of the circulator; the light emitted from the fiber optic sensor hits the surface under test, and part of the light reflected or scattered by the surface under test returns to the fiber optic sensor and is also output from the third port of the circulator; the part of the light reflected from the probe end face of the fiber optic sensor and the part of the light reflected or scattered by the surface under test are both amplified by the second optical amplifier, and then the two beams interfere at the spectrometer, and the acquisition card acquires the interference light signal. The spectrometer output signal y is written as:

[0043]

[0044] In the formula, y 0m (λ) (m=1~M) is the center wavelength λ cm The interference signal intensity, n is the refractive index of the environment where the gap being measured is located, and v is a constant; m For stripe contrast, d m Let λ be the measured gap value when the m-th laser outputs a pulsed laser, and λ be analyzed.cm ±Δλ m The interference signal in the 1 / 2 wavelength range can be solved for d m Thus, by using the pulse timing control optical switch, the gap value is measured M times within an integration time T int The measurement frequency is improved by M times.

[0045] The present application can improve the measurement frequency by M times (M is an integer and M≥2) by using the wide bandwidth of the spectrometer and the timing control of the pulse laser in the above embodiments, which is beneficial to capture the details and transient response of the rotor operation.

Claims

1. A time-multiplexed spectral domain interferometry gap measurement system, characterized by, The application relates to a time-division multiplexing optical spectrum domain interference gap measurement system. The time-division multiplexing subsystem is used for generating time-division multiplexed light output to a first optical amplifier; The first optical amplifier is used for amplifying light from the time-division multiplexing subsystem and outputting the light to a circulator; The circulator is provided with a first port, a second port and a third port, wherein the first port is used for receiving light from the first optical amplifier; the second port is used for outputting light from the first optical amplifier, receiving part of light reflected by an end surface of a fiber sensor probe and part of light reflected or scattered by a measured surface; and the third port is used for outputting part of light reflected by the end surface of the fiber sensor probe and part of light reflected or scattered by the measured surface; The fiber sensor is used for converting a gap value into a measurable optical signal; The second optical amplifier is used for amplifying part of light reflected by the end surface of the fiber sensor probe and part of light reflected or scattered by the measured surface and outputting the light to a spectrometer; The spectrometer is used for interference between part of light reflected by the end surface of the fiber sensor probe and part of light reflected or scattered by the measured surface; The acquisition card is used for acquiring interference light signals in the spectrometer; The time-division multiplexing subsystem comprises at least two light paths with different wavelengths, which are used for time-division multiplexing light with different wavelengths to improve a measurement frequency; The time division multiplexing subsystem comprises a broadband light source; a pulse timing circuit generates M driving signals sdr int in the integration time T of the spectrometer m , M≥2, m=1~M, respectively driving M broadband light sources, so that each broadband light source is only turned on for a period T hm during the integration of the spectrometer.

2. The time multiplexed spectral domain interferometry gap measurement system of claim 1, wherein, The time-division multiplexing subsystem further comprises a pulse timing generating circuit, an optical filter and a beam combiner; wherein each light path is composed of a broadband light source and the optical filter in series; one end of each light path is connected to the pulse timing generating circuit through the broadband light source, and the other end is connected to an input end of the beam combiner through the optical filter; the time-division multiplexing subsystem is connected to the first optical amplifier through an output end of the beam combiner.

3. The spectral domain interferometry gap measurement system of claim 1, wherein, The time-division multiplexing subsystem further comprises a pulse timing generating circuit, a wavelength division multiplexer and an optical switch; wherein one end of the pulse timing generating circuit and one end of the wavelength division multiplexer are connected to the optical switch respectively, the other end of the wavelength division multiplexer is connected to the broadband light source, and the time-division multiplexing subsystem is connected to the first optical amplifier through the optical switch; different wavelength light paths are directly formed between the wavelength division multiplexer and the optical switch.

4. The spectrographic interferometric gap measurement system of claim 1, wherein, The time-division multiplexing subsystem further comprises a pulse timing generating circuit, an optical filter, a beam splitter and an optical switch; wherein the pulse timing generating circuit is connected to the optical switch, and each light path passes through the optical filter; one end of the optical filter is connected to an output end of the beam splitter, and the other end is connected to the optical switch; an input end of the beam splitter is connected to the broadband light source; and the time-division multiplexing subsystem is connected to the first optical amplifier through the optical switch.

5. A time-multiplexed spectral-domain interferometric gap measurement method, characterized by The application relates to a time-division multiplexing optical spectrum domain interference gap measurement system, and the measurement method comprises the following steps: The pulse timing circuit generates a driving signal to drive the broadband light source in the integral time of the spectrometer, so that each broadband light source is only turned on for a period of time during the integration; the light emitted by the broadband light source is filtered by the optical filter, and then becomes a beam of light after being combined by the combiner and input into the first optical amplifier for power amplification; the light output by the first optical amplifier is input into the optical fiber sensor through the circulator, and part of the light reflected by the probe end face of the optical fiber sensor is output from the third port of the circulator; the light emitted by the optical fiber sensor hits the measured surface, and part of the light reflected or scattered by the measured surface returns to the optical fiber sensor and is also output from the third port of the circulator; the part of the light reflected by the probe end face of the optical fiber sensor and the part of the light reflected or scattered by the measured surface are both power amplified by the second optical amplifier, and then the two beams of light interfere in the spectrometer, and the interference light signal is collected by the collection card.

6. A time-multiplexed spectral-domain interferometric gap measurement method, characterized by The measurement method is applied to the time-division multiplexed spectral domain interference gap measurement system as claimed in claim 3, and comprises the following steps: The light emitted by the broadband light source is divided into different wavelengths by the wavelength division multiplexer, and then input into the first optical amplifier for power amplification after the optical switch, and the pulse timing circuit generates a driving signal to drive the optical switch to switch different wavelengths; the light output by the first optical amplifier is input into the optical fiber sensor through the circulator, and part of the light reflected by the probe end face of the optical fiber sensor is output from the third port of the circulator; the light emitted by the optical fiber sensor hits the measured surface, and part of the light reflected or scattered by the measured surface returns to the optical fiber sensor and is also output from the third port of the circulator; the part of the light reflected by the probe end face of the optical fiber sensor and the part of the light reflected or scattered by the measured surface are both power amplified by the second optical amplifier, and then the two beams of light interfere in the spectrometer, and the interference light signal is collected by the collection card.

7. A time-multiplexed spectral-domain interferometric gap measurement method, characterized by The measurement method is applied to the time-division multiplexed spectral domain interference gap measurement system as claimed in claim 4, and comprises the following steps: The light emitted by the broadband light source is divided into different wavelengths by the beam splitter, and then filtered by the optical filter, and then input into the first optical amplifier for power amplification after the optical switch, and the pulse timing circuit generates a driving signal to drive the optical switch to switch different wavelengths; the light output by the first optical amplifier is input into the optical fiber sensor through the circulator, and part of the light reflected by the probe end face of the optical fiber sensor is output from the third port of the circulator; the light emitted by the optical fiber sensor hits the measured surface, and part of the light reflected or scattered by the measured surface returns to the optical fiber sensor and is also output from the third port of the circulator; the part of the light reflected by the probe end face of the optical fiber sensor and the part of the light reflected or scattered by the measured surface are both power amplified by the second optical amplifier, and then the two beams of light interfere in the spectrometer, and the interference light signal is collected by the collection card.

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