CN204255613U - A kind of Sagnac annular light path is embedded in the optics autocorrelation function analyzer of non-equilibrium Mach-Zehnder type light path scanner - Google Patents

Abstract

The utility model belongs to the field of optical fiber technology, and specifically relates to a light source that can be used in the development and production of an optical fiber gyroscope for testing and analysis, and can also be used to transmit the light source of an optical fiber coupler, an optical fiber, and an optical fiber ring in an optical fiber gyroscope system. An optical autocorrelator embedded in an unbalanced optical path scanner in an annular optical path for testing the influence of the spectrum on the coherent properties of light. The utility model includes a light source, a three-port optical fiber circulator, a 3dB optical fiber coupler, a device to be tested, an unbalanced optical path difference scanner, a beam splitter, a spectrum analyzer, a photoelectric conversion differential amplifier, a scanning control unit, a signal processing unit, The data bus and PC computer of the autocorrelator, the correlator puts each main key optical device in an equivalent ring interferometer system to realize the measurement. Because the measurement environment of the device under test is similar to its working environment, the measurement results are helpful to characterize its actual working conditions and characteristics in the working state of the gyroscope.

Description

An optical autocorrelator with an unbalanced Mach-Zehnder optical path scanner embedded in a Sagnac ring optical path

technical field

The utility model belongs to the field of optical fiber technology, and specifically relates to a light source that can be used in the development and production of an optical fiber gyroscope for testing and analysis, and can also be used to transmit the light source of an optical fiber coupler, an optical fiber, and an optical fiber ring in an optical fiber gyroscope system. The optical autocorrelator embedded in the unbalanced Mach-Zehnder type optical path scanner in the Sagnac annular optical path of the test of the influence of the spectrum on the coherent characteristics of light.

Background technique

Optical fiber white light interference technology and method is a unique measurement method and sensing technology in the field of optical fiber technology. This specialized technology is used in the study of wide-spectrum optical interference characteristics, absolute deformation optical fiber sensing measurement, the structure of optical waveguide devices and the detection of light wave reflection characteristic parameters, and the measurement and evaluation of optical polarization state transverse coupling in fiber optic gyroscope rings, especially in It is widely used in the aspects of optical tomography of tissue structure and morphology in medical clinical diagnosis.

A high-precision fiber optic gyroscope is usually composed of a Sagnac fiber optic interferometer built from the main components such as a light source, a fiber optic coupler, a Y waveguide device, a polarization-maintaining fiber ring, and a detector. In order to realize the high-precision operation of the system, it is necessary to ensure that the performance indicators of the above-mentioned main optical components meet the requirements of high-precision measurement of the gyroscope. For this reason, it is necessary to conduct autocorrelation and autocoherence tests on the performance of the light source to evaluate the stability of the light source interference and the characteristics of the noise spectrum and its influence on the measurement results. In addition, the spectral transmittance of the optical fiber coupler, Y-waveguide device, polarization-maintaining optical fiber, and optical fiber ring to the light source used and its filtering performance on the light source spectrum are of great significance to the performance of the fiber optic gyroscope.

In view of the above-mentioned devices all working in the structure of the Sagnac fiber interferometer, for this reason the utility model is based on the basic structure of the Sagnac fiber interferometer, in the Sagnac annular light path, a can be produced in this reciprocal light path that can be used for scanning measurement At the same time, a low-noise differential detection signal processing system and an interference spectrum synchronous measurement system with noise suppression characteristics are constructed to achieve high-precision measurement and evaluation of the performance of key components of each fiber optic gyroscope.

The optical autocorrelator embedded in the unbalanced Mach-Zehnder type optical path scanner in the Sagnac annular optical path disclosed by the utility model and the traditional retroreflective interferometer (OLCR) constructed based on the Michelson interferometer optical path structure and a single The Mach-Zehnder type transmission polarization correlator (OCDP) is different, and its main difference is that the correlator puts each main key optical device in an equivalent Sagnac ring interferometer system to realize the measurement. Since the measurement environment of the device under test is similar to its working environment, the measurement results obtained in this way are helpful to characterize its actual working conditions and characteristics in the working state of the gyroscope.

In order to realize the characteristic test of optical waveguide device, in 1994, Matthew N.McLandrich, Donald J.Albares, and Stephen A.Pappert of U.S. Naval Laboratory disclosed a kind of retroreflective measurement system based on Michelson interferometer structure (U.S.A. Patent: Patent No. 5341205). In 1995, Wayne V.Sorin and Douglas M.Baney of U.S. H-P Company disclosed a kind of optical path autocorrelator based on Michelson interferometer structure (US Patent: Patent No. 5557400). It is based on the unbalanced Michelson interferometer structure, which is realized by matching the optical path difference formed between the fixed arm and the variable scanning arm of the Michelson interferometer by the optical signal and the optical path difference of the reflected optical signals from the front and rear ends of the fiber sensor. Optical autocorrelation to obtain the white light interference signal of the sensor. The correlator is composed of a 3dB fiber optic coupler. After the incident light wave is injected, the light wave is divided into two paths after passing through the 2×2 fiber optic coupler. After the optical collimator at the fiber end, it is reflected by the movable reflective scanning mirror to form a light wave with adjustable optical path and then reaches the output end. The advantage of the Michelson interferometer fiber optical path correlator is that it is simple in structure and uses few components. But the disadvantage is that the structure of the test light path is quite different from the working state of the Sagnac interferometer, and the test results are difficult to accurately match the requirements to be tested.

The optical path scanner is one of the main components of the correlator. The purpose of this device is to generate an additional optical path difference to enable the unfolded measurement of the relevant characteristic function. In order to construct various quasi-distributed optical fiber white light interference strain gauges, the applicant disclosed a distributed optical fiber white light interference sensor array based on an adjustable Fabry-Perot resonator in 2008 (Notice No. CN101324445A), a double reference length low Coherent optical fiber ring network sensing and demodulation device (notification number CN101325455B), combined measuring instrument of optical fiber Mach-Zehnder and Michelson interferometer array (notification number CN101329184A) and a simplified multiplexing white light interference optical fiber sensing and demodulation device (Notice number CN100588913C), respectively announced the optical path autocorrelator based on F-P cavity and ring cavity structure, the purpose is to simplify the structure of multiplexing interferometer; improve temperature stability; solve the simultaneous measurement of multiple reference sensors And other issues. Because the optical path difference involved in the utility model is a very small amount, therefore, the optical autocorrelator embedded in the unbalanced Mach-Zehnder type optical path scanner in the Sagnac annular optical path proposed by the utility model and its several This tiny optical path difference generation and scanning method is completely different from the system and scanning structure proposed by the US Patent (Patent No. 5341205; 5557400), and it is also completely different from the various optical measurement systems and the generation and scanning of the optical path difference previously applied by the applicant. scan structure. Moreover, the measurement method provided by the utility model can solve the problem of the influence of each key on the transmission spectrum of the light source and the coherence characteristics of the transmission spectrum of the wide-spectrum light source, the ring fiber, the fiber ring, the Y waveguide, the coupler, etc. in the production process of the fiber optic gyroscope. Influence. Its uniqueness cannot be replaced by other optical measurement systems.

Utility model content

The purpose of this utility model is to provide a light source that can be used in the development and production process of the fiber optic gyroscope for testing and analysis, and can also be used for the coherence of the light source transmission spectrum of the fiber optic coupler, optical fiber and fiber optic ring in the fiber optic gyroscope system. The optical autocorrelator embedded in the unbalanced Mach-Zehnder type optical path scanner in the Sagnac annular optical path of the characteristic influence test.

The purpose of this utility model is achieved in that:

An optical autocorrelator with an unbalanced Mach-Zehnder type optical path scanner embedded in the Sagnac ring optical path, including a light source, a three-port fiber optic circulator, a 3dB fiber coupler, a device under test, and an unbalanced Mach-Zehnder type optical path difference scanner , optical splitter, spectrum analyzer, photoelectric conversion differential amplifier, scanning control unit, signal processing unit, data bus of the autocorrelator and PC computer, the light source is connected to the a port of the three-port optical fiber circulator, and the b port of the optical fiber circulator is connected to the The e input end of the 3dB fiber optic coupler is connected; the c port of the fiber optic circulator is directly connected to the first photodetector _D1 ; the f interface of the 3dB fiber optic coupler is connected to the device under test, and the device under test is connected to the unbalanced Mach- The Zehnder optical path scanner is connected, and the other end of the unbalanced Mach-Zehnder optical path scanner is connected to the g port of the 3dB fiber optic coupler, and the interference signals are respectively transmitted from the output port of the 3dB fiber optic coupler to the c port of the three-port circulator. Port output to the first photodetector; the h output port of the 3dB fiber coupler is output to the second photodetector D ₂ through the optical splitter 6, and the first photodetector and the second photodetector are amplified through the differential amplifier, and the amplified The signal is output to the signal processing unit 10, and the interference signal arriving at the spectrum analyzer 7 via the optical splitter 6 outputs a spectral domain signal of coherent light in the form of a spectrum; the unbalanced Mach-Zehnder type optical path scanner 5 is driven by the scanning control unit 9 to form The change of the two paths of optical path difference realizes the scanning of the optical path difference, thereby obtaining the autocorrelation time domain signal, and the PC computer realizes the scanning control of the optical path difference and the collection of time domain data and spectral domain data through the data bus 11 .

The unbalanced Mach-Zehnder optical path difference scanner divides the same optical path into two paths of light, and adjusts one or both paths simultaneously to complete the modulation of the optical path difference and realize the scanning of the optical path difference.

Choose one of LED light source, SLD light source, and ASE light source as the wide-spectrum light source.

The unit under test adopts a section of single-mode polarization-maintaining optical fiber, and the broadband light source becomes the light source under test. The autocorrelation function and autocoherence spectrum of the wide-spectrum light source are measured and evaluated.

The unit under test is connected in series to the Sagnac ring optical path, and the unit under test is tested and evaluated. The unit under test is one of the following devices:

(1) The unit to be tested is a long section of optical fiber connected to the two test ports of the unit to be tested, which can obtain the transmission spectral filtering characteristics and spectral response characteristics of the optical fiber for known light sources;

(2) The unit to be tested is a 2×2 fiber optic coupler. Any two ports of the unit to be tested are connected to the two test ports of the unit to be tested, and the fiber coupler can obtain the transmission spectral filtering characteristics and spectral response characteristics of the known light source;

(3) The unit under test is a wound optical fiber gyro ring connected to two test ports of the unit under test, and the transmission spectral filtering characteristics and spectral response characteristics of the optical fiber gyro ring for a known light source are obtained.

The unbalanced Mach-Zehnder optical path difference scanner is one of the following devices:

(1) After the beam is collimated by the first optical fiber collimator, the beam is divided into two beams by the first light-combining prism, and then the two beams of space light are collimated through the second optical fiber through the fixed reflector and the second light-combining prism The collimator is sent back to the annular Sagnac fiber optical path, in which the formed one spatial optical path is fixed, and the other spatial optical path can be adjusted to move along the direction perpendicular to the axis of the fiber collimator to complete the alignment. poor adjustment and scanning;

(2) After the beam is collimated by the first optical fiber collimator, the beam is divided into two beams by the first light combining prism, and then the two beams of space light are collimated through the second optical fiber through the fixed reflection prism and the second light combining prism The collimator is sent back to the annular Sagnac fiber optical path, in which the formed one spatial optical path is fixed, and the other spatial optical path can be adjusted to move along the direction perpendicular to the axis of the fiber collimator to complete the alignment. poor adjustment and scanning;

(3) After the device adopts the first fiber collimator to collimate the light beam, it is incident into a symmetrical birefringent crystal optical wedge, and the light emitted from the birefringent crystal optical wedge is sent back to the annular Sagnac through the second fiber collimator In the fiber optical path, due to the birefringence effect, the optical wedge will introduce an optical path difference to the light with the orthogonal polarization direction. This optical path difference is proportional to the movement displacement of the optical wedge along the motion scanning perpendicular to the direction of the optical path. By adjusting The movement of the position of the scanning prism completes the adjustment and scanning of the optical path difference;

(4) The device uses a section of single-mode fiber, which is wound on the tubular piezoelectric ceramic PZT, and directly welded in the polarization-maintaining fiber Sagnac fiber loop, when the scanning driving voltage is loaded on the piezoelectric ceramic PZT , by changing the voltage loaded on the piezoelectric ceramic tube, the scanning of the optical path difference is realized;

(5) The device adopts a section of single-mode polarization-maintaining optical fiber, which is wound on the tubular piezoelectric ceramic PZT, and the polarization-maintaining optical fiber is rotated by 45 degrees and welded in the polarization-maintaining optical fiber Sagnac optical fiber loop, The single polarized light in the Sagnac polarization-maintaining fiber ring is divided into two orthogonal paths and injected into this section of fiber. When the scanning driving voltage is loaded on the piezoelectric ceramic PZT, the two orthogonally polarized lights transmitted in the fiber are formed. The optical path difference changes, and the scanning of the optical path difference is realized by changing the voltage loaded on the piezoelectric ceramic tube;

(6) The device adopts a section of eccentric dual-core optical fiber. The eccentric dual-core optical fiber has a central core and an eccentric core. The segment eccentric dual-core optical fiber is directly welded to the Sagnac fiber ring, and the two ends of the dual-core optical fiber are melt-drawn. The cone constitutes a dual-optical Mach-Zehnder interferometer integrated in an optical fiber. When the eccentric dual-core optical fiber is bent along the direction perpendicular to the axis of the optical fiber, an optical path difference is formed. Changing the size of the bending displacement realizes optical Scanning of distance difference;

(7) The device adopts a section of symmetrical dual-core optical fiber, directly welds the symmetrical dual-core optical fiber and the Sagnac fiber ring, and implements fusion tapering at the welding points at both ends of the dual-core optical fiber to form an integrated optical fiber Symmetrical double-optical Mach-Zehnder interferometer, when the double-core optical fiber is bent along the direction perpendicular to the fiber axis, an optical path difference will be formed, and the optical path difference can be scanned by changing the bending displacement;

(8) The device uses two Y-shaped fiber couplers connected with a three-port fiber optic circulator to form a Mach-Zehnder interferometer. The third port of the fiber optic circulator is connected to a fiber collimator, and the fiber collimator , a flat reflector, returns the outgoing light to the fiber optic Mach-Zehnder interferometer according to the original path, when the mirror moves along the direction of the outgoing light, the optical path difference between the two paths in the Mach-Zehnder interferometer changes , realize the scanning of the optical path difference;

(9) The device uses two Y-shaped fiber couplers and two fiber collimators connected to each other to form a Mach-Zehnder interferometer. The two fiber collimators are placed opposite each other, and the spatial position of one of the fiber couplers is along the optical path The transmission direction is adjusted so that the optical paths of the two arms of the Mach-Zehnder interferometer are equal, and the other arm of the Mach-Zehnder interferometer is wound on the tubular piezoelectric ceramic. When the voltage applied to the piezoelectric ceramic changes, The optical path difference between the two paths in the Mach-Zehnder interferometer will be changed to realize the scanning of the optical path difference.

The beneficial effects of the utility model are:

The optical autocorrelator embedded in the unbalanced Mach-Zehnder optical path scanner in the Sagnac annular optical path disclosed by the utility model and the traditional retroreflective interferometer OLCR and a single Mach-Zehnder optical path structure based on Michelson interferometer The Zehnder type transmission polarization correlator OCDP is different, and its main difference is that this correlator puts each main key optical device in an equivalent Sagnac ring interferometer system to realize the measurement. Since the measurement environment of the device under test is similar to its working environment, the measurement results obtained in this way are helpful to characterize its actual working conditions and characteristics in the working state of the gyroscope.

Description of drawings

Fig. 1 is a structural schematic diagram of an optical autocorrelator embedded in an unbalanced Mach-Zehnder type optical path scanner in a Sagnac ring optical path.

Fig. 2 is a schematic diagram of the simultaneous measurement of the autocorrelation function and the autocoherence spectrum of the broadband light source by the optical autocorrelator.

Fig. 3 is a schematic diagram of the measurement principle of the optical autocorrelator for the transmission spectrum characteristics of a long section of polarization-maintaining optical fiber and the filtering characteristics of the optical fiber for a wide-spectrum light source and its influence.

Fig. 4 is a schematic diagram of the measurement principle of the optical autocorrelator for the transmission spectrum characteristics of an optical fiber coupler and the filtering characteristics of the optical fiber for a wide-spectrum light source and its influence.

Fig. 5 is a schematic diagram of the measurement principle of the optical autocorrelator for the transmission spectrum characteristics of a fiber ring wound by a long polarization-maintaining fiber and the filtering characteristics of the fiber for a wide-spectrum light source and its influence.

Fig. 6 is an unbalanced Mach-Zehnder type optical path difference scanning device with adjustable optical path difference embedded in the Sagnac annular light path in the optical autocorrelator.

Fig. 7 is an unbalanced Mach-Zehnder optical path difference scanning device with adjustable optical path difference embedded in the Sagnac annular light path in the optical autocorrelator.

Fig. 8 is an unbalanced Mach-Zehnder optical path difference scanning device with adjustable optical path difference embedded in the Sagnac ring optical path in the optical autocorrelator.

Fig. 9 is an unbalanced Mach-Zehnder optical path difference scanning device with adjustable optical path difference embedded in the Sagnac annular light path in the optical autocorrelator.

Fig. 10 is an unbalanced Mach-Zehnder type optical path difference scanning device with adjustable optical path difference embedded in the Sagnac ring optical path in the optical autocorrelator.

Fig. 11 is an unbalanced Mach-Zehnder optical path difference scanning device with adjustable optical path difference embedded in the Sagnac ring optical path in the optical autocorrelator.

Fig. 12 is an unbalanced Mach-Zehnder optical path difference scanning device with adjustable optical path difference embedded in the Sagnac ring optical path in the optical autocorrelator.

Fig. 13 is an unbalanced Mach-Zehnder optical path difference scanning device with adjustable optical path difference embedded in the Sagnac annular light path in the optical autocorrelator.

Fig. 14 is an unbalanced Mach-Zehnder optical path difference scanning device with adjustable optical path difference embedded in the Sagnac ring optical path in the optical autocorrelator.

Detailed ways

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

The utility model discloses an optical autocorrelator embedded in an unbalanced Mach-Zehnder type optical path scanner in a Sagnac annular optical path, and its main features are: the autocorrelator is composed of a light source 1; Optical fiber coupler 3; device under test 4; unbalanced Mach-Zehnder type optical path difference scanner 5; optical splitter 6; spectrum analyzer 7; photoelectric conversion differential amplifier 8; scanning control unit 9; time domain correlation signal processing unit 10; the data bus 11 of the autocorrelator; and the PC computer 12 and other parts. The autocorrelation instrument provided by the utility model can simultaneously realize the measurement of the time-domain autocorrelation function of the light source and the measurement of the self-coherence spectrum of the spectrum domain; it can measure the influence of the fiber coupler on the autocorrelation function and the self-coherence spectrum, and the influence Evaluate; the effects of the fiber ring before the ring and the fiber ring after the ring on the autocorrelation function and the autocoherence spectrum can be measured respectively, and the effect can be evaluated. It can be used to test and analyze the light source in the development and production of fiber optic gyro, and can also be used to test the influence of the light source transmission spectrum of the fiber coupler, fiber and fiber ring in the fiber optic gyro system on the coherence characteristics of light.

Fig. 1 is a structural schematic diagram of an optical autocorrelator embedded in an unbalanced Mach-Zehnder type optical path scanner in a Sagnac ring optical path. In the figure, the autocorrelator consists of a light source 1; a three-port fiber optic circulator 2; a 3dB fiber optic coupler 3; a device to be tested 4; an unbalanced Mach-Zehnder type optical path difference scanner 5; ; Photoelectric conversion differential amplifier 8; scanning control unit 9; signal processing unit 10; data bus 11 of the autocorrelator;

Fig. 2 is a schematic diagram of the simultaneous measurement of the autocorrelation function and the autocoherence spectrum of the broadband light source by the optical autocorrelator. In the figure, the two ports of the test unit are connected by a polarization-maintaining optical fiber with the same optical path as Sagnac. At this time, light source 1 becomes the light source to be tested, for example: LED wide-spectrum light source 1-1, LSD wide-spectrum light source 1- 2. The ASE wide-spectrum light source 1-3 can be connected to the light source 1, and the autocorrelation function and autocoherence spectrum of the light source to be measured can be obtained through the optical path scanning of the optical path difference scanning device 5 .

Fig. 3 is a schematic diagram of the measurement principle of the optical autocorrelator for the transmission spectrum characteristics of a long section of polarization-maintaining optical fiber and the filtering characteristics of the optical fiber for a wide-spectrum light source and its influence.

Fig. 4 is a schematic diagram of the measurement principle of the optical autocorrelator for the transmission spectrum characteristics of an optical fiber coupler and the filtering characteristics of the optical fiber for a wide-spectrum light source and its influence.

Fig. 5 is a schematic diagram of the measurement principle of the optical autocorrelator for the transmission spectrum characteristics of a fiber ring wound by a long polarization-maintaining fiber and the filtering characteristics of the fiber for a wide-spectrum light source and its influence.

Figure 6 is an unbalanced Mach-Zehnder type optical path difference scanning device embedded in the Sagnac ring light path in the optical autocorrelator, which adopts a fiber collimator to collimate the beam, and then splits The prism divides the light beam into two beams, and then sends the two beams of spatial light back to the annular Sagnac fiber optic path through the second fiber collimator through the fixed reflector and the second light combining prism. One of the spatial optical paths formed is fixed, and the other spatial optical path can be adjusted and scanned by adjusting the scanning prism to move back and forth along the X direction.

Figure 7 is an unbalanced Mach-Zehnder optical path difference scanning device embedded in the Sagnac ring optical path in the optical autocorrelator. The prism divides the light beam into two beams, and then sends the two beams of spatial light back to the annular Sagnac fiber optic path through the second fiber collimator through the fixed reflection prism and the second light combining prism. One of the spatial optical paths formed is fixed, and the other spatial optical path can be adjusted and scanned by adjusting the scanning prism to move back and forth along the X direction.

Fig. 8 is the unbalanced Mach-Zehnder type optical path difference scanning device embedded in the Sagnac annular optical path in the optical autocorrelator, which adopts a fiber collimator to collimate the light beam and then incident on In a symmetrical birefringent crystal optical wedge, the light emitted from the birefringent crystal optical wedge is sent back to the annular Sagnac fiber optical path through a second fiber collimator. Due to the birefringence effect, the optical wedge will introduce an optical path difference to the light with the orthogonal polarization direction. This optical path difference is proportional to the movement displacement of the optical wedge along the X direction of motion scanning. By adjusting the position of the scanning prism before and after The movement completes the adjustment and scanning of the optical path difference.

Figure 9 is an unbalanced Mach-Zehnder type optical path difference scanning device embedded in the Sagnac ring optical path in the optical autocorrelator, which adopts a section of ordinary single-mode fiber, and winds this section of single-mode fiber On the tubular piezoelectric ceramic PZT and directly welded in the polarization-maintaining fiber Sagnac fiber loop, when the scanning driving voltage is loaded on the piezoelectric ceramic PZT, due to the expansion of the tubular piezoelectric ceramic, it will cause The two orthogonal degenerate modes transmitted in the medium are separated into two paths of light, thereby forming an optical path difference, and the scanning of the optical path difference can be realized by changing the voltage loaded on the piezoelectric ceramic tube.

Fig. 10 is an unbalanced Mach-Zehnder type optical path difference scanning device embedded in the Sagnac ring optical path in the optical autocorrelator, which adopts a section of single-mode polarization-maintaining fiber The polarization-maintaining fiber is wound on the tubular piezoelectric ceramic PZT, and the polarization-maintaining fiber is rotated by 45 degrees and welded in the polarization-maintaining fiber Sagnac fiber loop, so that the single polarized light in the Sagnac polarization-maintaining fiber loop is divided into two orthogonal paths Injected into this section of fiber, when the scanning driving voltage is loaded on the piezoelectric ceramic PZT, due to the expansion of the tubular piezoelectric ceramic, the optical path difference formed by the two orthogonally polarized lights transmitted in the fiber will change. . Therefore, by changing the voltage loaded on the piezoelectric ceramic tube, the scanning of the optical path difference can be realized.

Figure 11 is an unbalanced Mach-Zehnder type optical path difference scanning device embedded in the Sagnac ring optical path in the optical autocorrelator, which adopts a section of eccentric dual-core optical fiber, and the eccentric dual-core optical fiber has a A central core and an eccentric core, this eccentric dual-core fiber is directly welded to the Sagnac fiber ring, and the two ends of the dual-core fiber are fused and tapered to form a dual optical path integrated in one fiber When the Mach-Zehnder interferometer bends the section of eccentric double-core fiber along the X direction, an optical path difference will be formed, and the scanning of the optical path difference can be realized by changing the size of the bending displacement.

Figure 12 is an unbalanced Mach-Zehnder type optical path difference scanning device embedded in the Sagnac ring optical path in the optical autocorrelator. The core fiber is directly welded to the Sagnac fiber ring, and the fusion taper is implemented at the two ends of the double-core fiber to form a symmetrical double-optical path Mach-Zehnder interferometer integrated in one fiber. When the optical fiber is bent along the X direction, an optical path difference will be formed, and the scanning of the optical path difference can be realized by changing the size of the bending displacement.

Figure 13 is an unbalanced Mach-Zehnder optical path difference scanning device embedded in the Sagnac ring optical path in the optical autocorrelator, which uses two Y-shaped fiber couplers and a three-port fiber ring connected to form a Mach-Zehnder interferometer. The third port of the fiber optic circulator is connected to a fiber collimator, and there is a plane reflector facing the fiber collimator, which returns the outgoing light to the fiber optic Mach-Zehnder interferometer according to the original path. When the mirror moves back and forth along the X direction, the optical path difference between the two paths in the Mach-Zehnder interferometer will change, thereby realizing the scanning of the optical path difference.

Figure 14 is an unbalanced Mach-Zehnder type optical path difference scanning device with adjustable optical path difference embedded in the Sagnac ring optical path in the optical autocorrelator, which uses two Y-shaped fiber couplers and two optical fiber collimators The devices are connected to each other to form a Mach-Zehnder interferometer. While the two fiber collimators are placed opposite to each other, the spatial position of one of the fiber couplers can be adjusted along the Z direction, so that the optical paths of the two arms of the Mach-Zehnder interferometer are equal. The other arm of the Mach-Zehnder interferometer is wound on the tubular piezoelectric ceramic PZT. When the voltage loaded on the piezoelectric ceramic PZT changes, the two-way optical path difference in the Mach-Zehnder interferometer will change. , so as to realize the scanning of the optical path difference.

The autocorrelator consists of a light source 1; a three-port fiber optic circulator 2; a 3dB fiber optic coupler 3; a device to be tested 4; an unbalanced Mach-Zehnder type optical path difference scanner 5; The conversion differential amplifier 8; the scanning control unit 9; the signal processing unit 10; the data bus 11 of the autocorrelator; and the PC computer 12 and other components. The light source 1 is connected to the port a of the three-port optical fiber circulator 2, the port b of the optical fiber circulator 2 is connected to the input end e of the 3dB fiber optic coupler 3; and the port c of the optical fiber circulator 2 is directly connected to the photodetector _D1 The 3dB fiber optic coupler 3 interface f is connected with the device under test 4, and is further connected with the unbalanced Mach-Zehnder type optical path scanner 5, and the other end of the optical path scanner is connected with the port of the 3dB fiber optic coupler 3 g is connected, and the interference signal is output to the detector D ₁ by the output port of the 3dB fiber coupler 3 via the port c of the three-port circulator 2; the output port h of the 3dB fiber coupler 3 is output to the detector D ₂ through the optical splitter 6 . Finally, the photodetectors D ₁ and D ₂ are amplified by the differential amplifier 8 , and the amplified signals are output to the signal processing unit 10 . At the same time, the interference signal arriving at the spectrum analyzer 7 via the beam splitter 6 outputs a spectral domain signal of coherent light in the form of a spectrum. The autocorrelator drives the unbalanced Mach-Zehnder type optical path scanner 5 through the scanning control unit 9 to form the change of the two-way optical path difference, realizes the scanning of the optical path difference, and obtains the autocorrelation time domain signal. The autocorrelator is controlled by the PC computer 12 through the data bus 11 to realize the scanning control of the optical path difference and the collection of time domain data and spectral domain data.

Since the optical fiber Sagnac interferometer structure is a common optical path structure, in order to realize the measurement of the optical autocorrelation function, it is necessary to introduce a device that can divide one light into two paths, so we embedded in the Sagnac ring light path of the optical autocorrelator An unbalanced Mach-Zehnder type optical path scanner 5 with adjustable optical path difference. This optical path scanner can divide the same optical path into two paths of light, and adjust one or both paths simultaneously to complete the alignment of the optical path Poor modulation to realize scanning of optical path difference.

In order to realize the test and evaluation of the light source, the unit under test in the optical autocorrelator is connected to the two test ports with a section of single-mode polarization-maintaining optical fiber, so that the wide-spectrum light source 1 of the autocorrelator becomes the light source under test , can be connected to any light source to be measured, so as to realize the measurement and evaluation of the autocorrelation function and autocoherence spectrum of the wide-spectrum light source itself.

In order to introduce an adjustable optical path difference device in the Sagnac annular light path of the new optical autocorrelator, nine kinds of unbalanced Mach-Zehnder type optical path difference scanners with adjustable optical path difference were constructed. All path difference scanners can perform optical path difference scanning during autocorrelation function measurement.

In the optical autocorrelator, the optical components to be tested can be connected in series to the Sagnac ring optical path as the unit under test 4, so as to realize the test and evaluation of the device under test.

Embodiment one: in order to test the characteristics of the single-mode polarization-maintaining fiber, we connect the single-mode fiber in series to the position of the device under test 4-2 in the Sagnac ring optical path, as shown in Figure 3, the fiber under test and The two test ports of the unit under test 4 are connected to realize the measurement of the transmission spectral filtering characteristics and spectral response characteristics of the optical fiber for known light sources.

Embodiment two: in order to obtain the impact of the fiber optic coupler on the light source in the fiber optic gyroscope system, it is connected in series to the position of the device under test 4-3 in the Sagnac ring light path, as shown in Figure 4, the 2 × 2 Any two ports of the fiber coupler are connected to two test ports of the unit under test 4, so that the fiber coupler can measure the transmission spectral filtering characteristics and spectral response characteristics of known light sources.

Embodiment three: in order to obtain the impact of the optical fiber ring made by winding on the light source in the fiber optic gyroscope system, it is connected in series to the position of the device under test 4-2 in the Sagnac ring light path, as shown in Figure 5, the wound fiber ring The fiber optic gyro ring is connected to the two test ports of the unit under test 4 to realize the measurement of the fiber optic gyro ring for transmission spectral filtering characteristics and spectral response characteristics of known light sources.

Claims (6)

1. An optical autocorrelator embedded in an unbalanced Mach-Zehnder type optical path scanner in a Sagnac ring optical path, comprising a light source (1), a three-port fiber optic circulator (2), a 3dB fiber optic coupler (3), and a sample to be tested Device (4), unbalanced Mach-Zehnder type optical path difference scanner (5), beam splitter (6), spectrum analyzer (7), photoelectric conversion differential amplifier (8), scanning control unit (9), signal The processing unit (10), the data bus (11) of the autocorrelator and the PC computer (12), the light source is connected with the a port of the three-port fiber optic circulator, and the b port of the fiber optic circulator is connected with the e input end of the 3dB fiber optic coupler and the c port of the optical fiber circulator is directly connected with the first photodetector (D1); the f interface of the 3dB fiber coupler is connected with the device under test, and the device under test is connected with the unbalanced Mach-Zehnder type optical path scanner, The other end of the unbalanced Mach-Zehnder type optical path scanner is connected to the g port of the 3dB fiber optic coupler, and the interference signals are respectively output to the first photodetector by the output port of the 3dB fiber optic coupler via the c port of the three-port circulator; The h output port of the 3dB fiber coupler is output to the second photodetector (D2) through the optical splitter 6, the first photodetector and the second photodetector are amplified through the differential amplifier, and the amplified signal is output to the signal processing unit (10 ), the interference signal arriving at the spectrum analyzer (7) through the beam splitter (6) outputs the spectral domain signal of the coherent light in the form of a spectrum; the unbalanced Mach-Zehnder type optical path scanner (5) is driven by the scanning control unit (9) ) form two-way optical path difference changes, realize the scanning of optical path difference, thereby obtain autocorrelation time domain signal, realize the scanning control and time domain data and spectral domain to optical path difference by PC computer through data bus (11) data collection. 2. the optical autocorrelator of embedding unbalanced Mach-Zehnder type optical path scanner in a kind of Sagnac annular optical path according to claim 1, it is characterized in that: unbalanced Mach-Zehnder type optical path difference scanner will be the same The optical path is divided into two paths of light, and by adjusting one of them or adjusting both paths at the same time, the modulation of the optical path difference is completed, and the scanning of the optical path difference is realized. 3. the optical autocorrelator of embedding unbalanced Mach-Zehnder type optical path scanner in a kind of Sagnac annular optical path according to claim 1, it is characterized in that: described wide-spectrum light source selects LED light source, SLD light source, ASE One of the light sources. 4. the optical autocorrelator of embedding unbalanced Mach-Zehnder type optical path scanner in a kind of Sagnac annular optical path according to claim 1, it is characterized in that: described unit to be measured adopts a section of single-mode polarization-maintaining optical fiber, The wide-spectrum light source becomes the light source to be measured, and the measurement and evaluation of the autocorrelation function and autocoherence spectrum of the wide-spectrum light source itself. 5. the optical autocorrelator of embedding unbalanced Mach-Zehnder type optical path scanner in a kind of Sagnac ring light path according to claim 1, it is characterized in that: described unit to be measured is connected in series in Sagnac ring light path , for the testing and evaluation of the unit under test, the unit under test is one of the following devices: (1) The unit to be tested is a long section of optical fiber connected to the two test ports of the unit to be tested, which can obtain the transmission spectral filtering characteristics and spectral response characteristics of the optical fiber for known light sources; (2) The unit to be tested is a 2×2 fiber optic coupler. Any two ports of the unit to be tested are connected to the two test ports of the unit to be tested, and the fiber coupler can obtain the transmission spectral filtering characteristics and spectral response characteristics of the known light source; (3) The unit under test is a wound optical fiber gyro ring connected to two test ports of the unit under test, and the transmission spectral filtering characteristics and spectral response characteristics of the optical fiber gyro ring for a known light source are obtained. 6. the optical autocorrelator of embedding unbalanced Mach-Zehnder type optical path scanner in a kind of Sagnac annular optical path according to claim 1, it is characterized in that: unbalanced Mach-Zehnder type optical path difference scanner is following One of the devices: (1) After the beam is collimated by the first optical fiber collimator, the beam is divided into two beams by the first light-combining prism, and then the two beams of space light are collimated through the second optical fiber through the fixed reflector and the second light-combining prism The collimator is sent back to the annular Sagnac fiber optical path, in which the formed one spatial optical path is fixed, and the other spatial optical path can be adjusted to move along the direction perpendicular to the axis of the fiber collimator to complete the alignment. poor adjustment and scanning; (2) After the beam is collimated by the first optical fiber collimator, the beam is divided into two beams by the first light combining prism, and then the two beams of space light are collimated through the second optical fiber through the fixed reflection prism and the second light combining prism The collimator is sent back to the annular Sagnac fiber optical path, in which the formed one spatial optical path is fixed, and the other spatial optical path can be adjusted to move along the direction perpendicular to the axis of the fiber collimator to complete the alignment. poor adjustment and scanning; (3) After the device adopts the first fiber collimator to collimate the light beam, it is incident into a symmetrical birefringent crystal optical wedge, and the light emitted from the birefringent crystal optical wedge is sent back to the annular Sagnac through the second fiber collimator In the fiber optical path, due to the birefringence effect, the optical wedge will introduce an optical path difference to the light with the orthogonal polarization direction. This optical path difference is proportional to the movement displacement of the optical wedge along the motion scanning perpendicular to the direction of the optical path. By adjusting The movement of the position of the scanning prism completes the adjustment and scanning of the optical path difference; (4) The device uses a section of single-mode fiber, which is wound on the tubular piezoelectric ceramic PZT, and directly welded in the polarization-maintaining fiber Sagnac fiber loop, when the scanning driving voltage is loaded on the piezoelectric ceramic PZT , by changing the voltage loaded on the piezoelectric ceramic tube, the scanning of the optical path difference is realized; (5) The device adopts a section of single-mode polarization-maintaining optical fiber, which is wound on the tubular piezoelectric ceramic PZT, and the polarization-maintaining optical fiber is rotated by 45 degrees and welded in the polarization-maintaining optical fiber Sagnac optical fiber loop, The single polarized light in the Sagnac polarization-maintaining fiber ring is divided into two orthogonal paths and injected into this section of fiber. When the scanning driving voltage is loaded on the piezoelectric ceramic PZT, the two orthogonally polarized lights transmitted in the fiber are formed. The optical path difference changes, and the scanning of the optical path difference is realized by changing the voltage loaded on the piezoelectric ceramic tube; (6) The device adopts a section of eccentric dual-core optical fiber. The eccentric dual-core optical fiber has a central core and an eccentric core. The segment eccentric dual-core optical fiber is directly welded to the Sagnac fiber ring, and the two ends of the dual-core optical fiber are melt-drawn. The cone constitutes a dual-optical Mach-Zehnder interferometer integrated in an optical fiber. When the eccentric dual-core optical fiber is bent along the direction perpendicular to the axis of the optical fiber, an optical path difference is formed. Changing the size of the bending displacement realizes optical Scanning of distance difference; (7) The device adopts a section of symmetrical dual-core optical fiber, directly welds the symmetrical dual-core optical fiber and the Sagnac fiber ring, and implements fusion tapering at the welding points at both ends of the dual-core optical fiber to form an integrated optical fiber Symmetrical double-optical Mach-Zehnder interferometer, when the double-core optical fiber is bent along the direction perpendicular to the fiber axis, an optical path difference will be formed, and the optical path difference can be scanned by changing the bending displacement; (8) The device uses two Y-shaped fiber couplers connected with a three-port fiber optic circulator to form a Mach-Zehnder interferometer. The third port of the fiber optic circulator is connected to a fiber collimator, and the fiber collimator , a flat reflector, returns the outgoing light to the fiber optic Mach-Zehnder interferometer according to the original path, when the mirror moves along the direction of the outgoing light, the optical path difference between the two paths in the Mach-Zehnder interferometer changes , realize the scanning of the optical path difference; (9) The device uses two Y-shaped fiber couplers and two fiber collimators connected to each other to form a Mach-Zehnder interferometer. The two fiber collimators are placed opposite each other, and the spatial position of one of the fiber couplers is along the optical path The transmission direction is adjusted so that the optical paths of the two arms of the Mach-Zehnder interferometer are equal, and the other arm of the Mach-Zehnder interferometer is wound on the tubular piezoelectric ceramic. When the voltage applied to the piezoelectric ceramic changes, The optical path difference of the two paths in the Mach-Zehnder interferometer will be changed to realize the scanning of the optical path difference.