CN110632714B - Optical fiber coupling system and coupling method - Google Patents
Optical fiber coupling system and coupling method Download PDFInfo
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- CN110632714B CN110632714B CN201910890954.7A CN201910890954A CN110632714B CN 110632714 B CN110632714 B CN 110632714B CN 201910890954 A CN201910890954 A CN 201910890954A CN 110632714 B CN110632714 B CN 110632714B
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- G—PHYSICS
- G02—OPTICS
- G02B—OPTICAL ELEMENTS, SYSTEMS OR APPARATUS
- G02B6/00—Light guides; Structural details of arrangements comprising light guides and other optical elements, e.g. couplings
- G02B6/24—Coupling light guides
- G02B6/42—Coupling light guides with opto-electronic elements
- G02B6/4201—Packages, e.g. shape, construction, internal or external details
- G02B6/4204—Packages, e.g. shape, construction, internal or external details the coupling comprising intermediate optical elements, e.g. lenses, holograms
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- G—PHYSICS
- G02—OPTICS
- G02B—OPTICAL ELEMENTS, SYSTEMS OR APPARATUS
- G02B6/00—Light guides; Structural details of arrangements comprising light guides and other optical elements, e.g. couplings
- G02B6/24—Coupling light guides
- G02B6/42—Coupling light guides with opto-electronic elements
- G02B6/4201—Packages, e.g. shape, construction, internal or external details
- G02B6/4204—Packages, e.g. shape, construction, internal or external details the coupling comprising intermediate optical elements, e.g. lenses, holograms
- G02B6/4214—Packages, e.g. shape, construction, internal or external details the coupling comprising intermediate optical elements, e.g. lenses, holograms the intermediate optical element having redirecting reflective means, e.g. mirrors, prisms for deflecting the radiation from horizontal to down- or upward direction toward a device
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- G—PHYSICS
- G02—OPTICS
- G02B—OPTICAL ELEMENTS, SYSTEMS OR APPARATUS
- G02B6/00—Light guides; Structural details of arrangements comprising light guides and other optical elements, e.g. couplings
- G02B6/24—Coupling light guides
- G02B6/42—Coupling light guides with opto-electronic elements
- G02B6/4201—Packages, e.g. shape, construction, internal or external details
- G02B6/4219—Mechanical fixtures for holding or positioning the elements relative to each other in the couplings; Alignment methods for the elements, e.g. measuring or observing methods especially used therefor
- G02B6/422—Active alignment, i.e. moving the elements in response to the detected degree of coupling or position of the elements
- G02B6/4225—Active alignment, i.e. moving the elements in response to the detected degree of coupling or position of the elements by a direct measurement of the degree of coupling, e.g. the amount of light power coupled to the fibre or the opto-electronic element
Abstract
An optical fiber coupling system and a coupling method relate to the technical field of optical fiber coupling, and solve the problems of small effective working range, low coupling alignment precision and serious interference by atmospheric turbulence, wherein the system comprises an optical fiber coupling system which comprises a light spot tracking fast reflecting mirror, a tracking mirror driver, a beam splitter, an imaging lens group, a light spot position detector, an image processor, a nutation coupling fast reflecting mirror, a coupling mirror driver, a coupling lens group, a coupling optical fiber, a light energy detector and a controller; the light spot position detector is placed on a focal plane of the imaging lens group, the end face of the optical fiber head of the coupling optical fiber is placed on the focal plane of the coupling lens group, and the optical axis of the optical fiber head is coaxial with the optical axis of the coupling lens group. The invention realizes the optical fiber coupling with large effective visual field, strong anti-interference capability and high coupling efficiency. The optical fiber coupling efficiency can be still maintained under the influence of atmospheric turbulence, the overall communication quality of a laser communication link is ensured, and the application range is wide.
Description
Technical Field
The invention relates to the technical field of optical fiber coupling, in particular to an optical fiber coupling system and a coupling method.
Background
The efficient and stable space light-single mode fiber coupling technology is a precondition and guarantee for realizing the high-speed long-distance laser communication technology and is also a key technology in space laser application systems such as laser radar, photoelectric countermeasure and the like. Due to the optical mechanical processing, adjustment, vibration and the like, the coupled light beam has tilt, defocusing or other aberration, so that the coupling efficiency of the space light-single mode fiber is remarkably reduced.
When the optical fiber coupling technology is applied in an atmospheric environment, when a laser beam propagates in the atmosphere, the turbulent effect of the atmosphere generates serious interference on the laser beam, so that the fluctuation effect of the arrival angle of the light beam at a receiving end is serious, the imaging quality of a light spot is reduced, position feedback is inaccurate, the alignment precision of an optical fiber coupling system based on the position feedback of the light spot is reduced (the optimal point of energy cannot be found), the implementation of the space optical-single mode optical fiber coupling technology is seriously influenced, and the optical fiber coupling efficiency is reduced. The system using the optical fiber coupling energy as feedback can accurately find the optimal coupling position, but has the problems of small effective coupling field of view, high requirement on the alignment precision of the coupling light beam and low anti-interference capability.
Swanson et al (Swanson E A, Bondurant R S. Using fiber optics to Simplifyfy free-space laser systems [ C ]. Proceedings of the SPIE,1990,1218:70-82.) use an active fiber coupler as an actuator to improve the coupling efficiency of single mode fibers by fiber nutation, which is simple in structure and wide in bandwidth, but the amount of movement of the end face of the fiber in the scheme is less than 10 μm, and is only suitable for a single mode fiber with a small partial mode field radius.
Hahn et al propose large field-of-view optical signal reception schemes using Fiber array coupling (Hahn D V, Brown D M, Rolander N W, et al, Fiber optical bundle with field-of-visual optical communications [ J ], Optics letters,2010,35(21): 3559-3561). This solution does not compensate for sub-beam errors and the system coupling efficiency depends on the processing and alignment accuracy of the microlens array and bundled fiber bundles.
Takenaka et al detected atmospheric turbulence induced beam tilt errors in the satellite-to-ground link in a 1000km satellite-to-ground link experiment using a four quadrant detector and corrected for tilt errors using a fast tilting mirror (Takenaka H, Toyoshima M, Takayama Y. Experimental version of fiber-coupling efficiency for satellite-to-ground and analog laser downs [ J ]. Optics Express 2012,20(14): 15301-8.). The scheme has the advantages of complex structure, small effective view field and low system bandwidth, and is not suitable for the environment with light spots seriously influenced by atmosphere.
The problem of optical fiber coupling efficiency has become a technical bottleneck restricting the development of laser communication technology in China. Particularly, in links with strong interference of laser signals due to the atmospheric turbulence effect, such as a satellite-ground laser communication link and a horizontal atmospheric laser communication link, an automatic optical fiber technology is urgently needed to further reduce the tilt residual error at the rear end of the adaptive optical system, improve the coupling efficiency and further improve the overall communication quality of the laser communication link.
Disclosure of Invention
The invention provides an optical fiber coupling system and a coupling method, aiming at solving the problems of small effective working range, low coupling alignment precision and serious interference of atmospheric turbulence of the existing optical fiber coupling system.
The technical scheme adopted by the invention for solving the technical problem is as follows:
an optical fiber coupling system comprises a light spot tracking fast reflecting mirror, a tracking mirror driver, a beam splitter, an imaging lens group, a light spot position detector, an image processor, a nutation coupling fast reflecting mirror, a coupling mirror driver, a coupling lens group, a coupling optical fiber, a light energy detector and a controller; the light spot position detector is placed on a focal plane of the imaging lens group, the end face of the optical fiber head of the coupling optical fiber is placed on the focal plane of the coupling lens group, and the optical axis of the optical fiber head is coaxial with the optical axis of the coupling lens group;
the incident beam is incident on the light spot tracking fast reflector and enters the light splitting sheet after being reflected by the light spot tracking fast reflector, the incident beam is divided into a transmission beam and a reflection beam by the light splitting sheet, the transmission beam is incident on the light spot position detector after passing through the imaging lens group, and the reflection beam enters the light energy detector after sequentially passing through the nutation coupling fast reflector, the focusing of the coupling lens group and the coupling into the coupling optical fiber;
when the light beam energy detected by the light energy detector is maximum, the light spot detected by the light spot position detector is superposed with the center of the target surface of the light spot position detector;
focal length f of coupling lens groupnSatisfy the requirement of
Wherein D is the aperture of the light beam incident on the coupling lens group, λ is the wavelength of the incident light beam, and ω is0Is the mode field radius of the coupled fiber.
A method of coupling an optical fiber coupling system, comprising the steps of:
step 1, starting a light spot position detector, an image processor, a coupling mirror driver, a light energy detector and a controller; the image processor sends the light spot position information to the controller, and the tracking mirror driver sends the light spot tracking fast reflection mirror position information to the controller;
step 3, the controller controls the light spot tracking fast reflecting mirror to track the light spot through the tracking mirror driver, the image processor calculates the light spot tracking miss amount and sends the light spot tracking miss amount to the controller, and the controller receives the light spot tracking miss amount and analyzes and judges whether the light spot tracking miss amount is smaller than 2 omega0/3fnObtaining an analysis result, if the analysis result is that the light spot tracking miss distance is less than 2 omega0/3fnThen go to step 4; if the analysis result shows that the light spot tracking miss amount is more than or equal to 2 omega0/3fnRe-executing the step 3;
step 4, the controller controls the nutation coupling fast reflection mirror to move through the coupling mirror driver to carry out nutation coupling;
The invention has the beneficial effects that:
an optical fiber coupling system adopts a light spot tracking fast reflecting mirror and a tracking mirror driver to track light spots and a light spot position detector to detect the position of the light spots; the optimal coupling position is found by a method of carrying out light spot nutation coupling and detecting optical fiber coupling energy through the nutation coupling fast reflection mirror, the coupling mirror driver and the light energy detector. The invention realizes large-range and high-precision light spot tracking, avoids small effective coupling view field in the light spot coupling technology, solves the problems of high requirement on the alignment precision of the coupling light beam and low anti-interference capability, and realizes optical fiber coupling with large effective view field, strong anti-interference capability and high coupling efficiency. The optical fiber coupling efficiency can be still maintained under the influence of atmospheric turbulence, the overall communication quality of a laser communication link is ensured, and the application range is wide.
By adopting a coupling method based on an optical fiber coupling system, coarse alignment is performed before fine alignment is performed, and accurate, efficient and high-interference-resistant optical fiber coupling can be realized through a simple structure and a simple method.
Drawings
Fig. 1 is a schematic diagram of the structure, connection relationship and optical path of an optical fiber coupling system according to the present invention.
Fig. 2 is a flow chart of a coupling method of an optical fiber coupling system according to the present invention.
In the figure: 1. the device comprises a light spot tracking fast reflecting mirror, 2, a tracking mirror driver, 3, a light splitting sheet, 4, an imaging lens group, 5, a light spot position detector, 6, an image processor, 7, a beam shrinking lens group, 8, a nutation coupling fast reflecting mirror, 9, a coupling mirror driver, 10, a coupling lens group, 11, a coupling optical fiber, 12, a light energy detector, 13 and a controller.
Detailed Description
The present invention will be described in further detail with reference to the accompanying drawings and examples.
An optical fiber coupling system comprises a light spot tracking fast reflecting mirror 1, a tracking mirror driver 2, a light splitting sheet 3, an imaging lens group 4, a light spot position detector 5, an image processor 6, a nutation coupling fast reflecting mirror 8, a coupling mirror driver 9, a coupling lens group 10, a coupling optical fiber 11, a light energy detector 12 and a controller 13, as shown in figure 1.
The spot position detector 5 is placed on the focal plane of the imaging lens group 4. The end face of the optical fiber head of the coupling optical fiber 11 is placed on the focal plane of the coupling lens group 10, and the optical axis of the optical fiber head is coaxial with the optical axis of the coupling lens group 10. The tracking mirror driver 2 is connected with and drives the facula tracking fast reflecting mirror 1 to move, and the facula position detector 5 is connected with the image processor 6. The coupling mirror driver 9 is connected with and drives the nutation coupling fast reflecting mirror 8 to move, and the coupling optical fiber 11 is connected with the optical energy detector 12. The controller 13 is respectively connected with the image processor 6, the light energy detector 12, the tracking mirror driver 2 and the coupling mirror driver 9.
After an incident beam (namely a beam to be coupled) enters a system, the incident beam firstly enters a light spot tracking fast reflecting mirror 1, the incident beam enters a light splitting sheet 3 after being reflected by the light spot tracking fast reflecting mirror 1, the light splitting sheet 3 divides the incident beam into a transmission beam and a reflection beam, the transmission beam enters a light spot position detector 5 after passing through an imaging lens group 4, the reflection beam enters a nutation coupling fast reflecting mirror 8, the reflection beam enters a coupling lens group 10 after being reflected by the nutation coupling fast reflecting mirror 8, the reflection beam is focused by the coupling lens group 10 and then is coupled into a coupling optical fiber 11, and the beam coupled into the coupling optical fiber 11 is transmitted by the coupling optical fiber 11 and then enters an.
The light spot tracking fast reflecting mirror 1, the light splitting plate 3, the imaging lens group 4 and the light spot position detector 5 are sequentially arranged along a light path, the light spot tracking fast reflecting mirror 1 and the light splitting plate 3 are sequentially arranged along the transmission direction of incident light beams, the imaging lens group 4 and the light spot position detector 5 are sequentially arranged along the transmission direction of transmitted light beams, and the imaging lens group 4 is positioned between the light splitting plate 3 and the light spot position detector 5. The light spot tracking fast reflecting mirror 1, the light splitting sheet 3, the nutation coupling fast reflecting mirror 8, the coupling lens group 10, the coupling optical fiber 11 and the light energy detector 12 are sequentially arranged along another light path, and the nutation coupling fast reflecting mirror 8, the coupling lens group 10, the coupling optical fiber 11 and the light energy detector 12 are sequentially arranged along the transmission direction of a reflected light beam.
The optical fiber coupling system also comprises a beam reducing mirror group 7 which is positioned between the light splitter 3 and the nutation coupling fast reflecting mirror 8, the light splitter 3 divides an incident beam into a transmission beam and a reflection beam, and the reflection beam is contracted by the beam reducing mirror group 7 and then enters the nutation coupling fast reflecting mirror 8.
The working process of the optical fiber coupling system comprises the following steps: the light spot position detector 5 transmits image information to the image processor 6, the image processor 6 processes the image information to obtain light spot position information and sends the light spot position information to the controller 13, the light spot tracking fast reflecting mirror position information sent by the tracking mirror driver 2 is sent to the controller 13, the controller 13 calculates the coordinates of the next target point of the light spot tracking fast reflecting mirror 1 according to the light spot position information, then a tracking control signal is obtained according to the light spot tracking fast reflecting mirror position information to obtain a tracking mirror position instruction, the tracking control signal is sent to the tracking mirror driver 2, the tracking mirror driver 2 receives the tracking control signal sent by the controller 13 and drives the light spot tracking fast reflecting mirror 1 to move according to the tracking control signal, and therefore closed-loop tracking of the light spots is completed; the light beam coupled into the coupling optical fiber 11 enters the light energy detector 12 through the coupling optical fiber 11, the light energy detector 12 detects light energy of the light beam entering the light energy detector to obtain light energy information and sends the light energy information to the controller 13, the nutation coupling fast-reflection mirror position information sent by the coupling mirror driver 9 is sent to the controller 13, the controller 13 records the light energy information, the controller 13 calculates the next nutation position according to the light energy information, then obtains a coupling control signal according to the nutation coupling fast-reflection mirror position information to obtain a tracking mirror position instruction, and sends the coupling control signal to the coupling mirror driver 9, the coupling mirror driver 9 receives the coupling control signal and drives the nutation coupling fast-reflection mirror 8 to reach the next nutation position according to the coupling control signal, and space light-optical fiber coupling based on energy detection is completed. The closed loop frequency of the spot tracking fast reflecting mirror 1 is 2.5kHz, and the closed loop frequency of the nutation coupling fast reflecting mirror 8 is 10 kHz.
Through the optical path adjustment, when the reflected beam is optimally coupled and aligned with the coupling optical fiber 11, that is, the coupling efficiency is the maximum, or when the beam energy detected by the optical energy detector 12 is the maximum, the light spot detected by the light spot position detector 5 coincides with the center of the target surface of the light spot position detector 5, and the coincidence error is controlled within 1 pixel, that is, the coincidence error is smaller than 1 pixel.
In nutating coupled systems, the focal length (f) of the coupling lens group 10n) The aperture (D) of the incident beam, the wavelength (lambda) of the incident beam and the coupled light to the coupling lens group 10Fiber 11 mode field radius (ω)0) The following relationship is satisfied:
wherein the wavelength of the incident beam, i.e. the wavelength of the light beam entering the coupling fiber 11, is the beam aperture of the coupling lens group 10, i.e. the beam aperture of the reflected light beam when the reflected light beam enters the coupling lens group 10.
The light spot tracking quick reflecting mirror 1 is driven based on piezoelectric ceramics, the light spot tracking quick reflecting mirror 1 is a biaxial orthogonal inclined mirror, the swing angle range is +/-1500 mu rad, the resonant frequency is 3000Hz, and the resolution is 0.05 mu rad.
The nutation coupling fast reflection mirror 8 is driven based on piezoelectric ceramics, the nutation coupling fast reflection mirror 8 is a double-shaft orthogonal inclined mirror, the swing angle range is +/-1000 mu rad, the resonant frequency is 6000Hz, and the resolution is 0.02 mu rad.
The wavelength of the light energy detector 12 is 1550 +/-2 nm, the dynamic range is 70dB, the minimum response light energy is-60 dBm, and the output frequency of the light energy information is 10 KHz.
The light spot position detector 5 adopts a super-high-speed light spot position detector 5 with a large target surface, and the target surface area of the light spot position detector 5 is more than 169mm2The running speed is more than 2000fps, and the resolution is not lower than 1024 x 1024 pixels. In the embodiment, the resolution of the selected light spot position detector 5 is 1024 × 1024 units, the pixel size is 8 × 8 μm, and the running speed is 2500 fps.
The coupling fiber 11 is a single mode fiber.
In the optical fiber coupling system, an incident beam needs to be shaped into parallel light with the diameter of 20mm, the light splitting sheet 3 is a wedge-shaped light splitting sheet 3, and the wedge angle is 5 degrees; the light intensity ratio of the transmitted light beam and the reflected light beam emitted by the light splitting piece 3 is 5%: 95%, the beam-reducing ratio of the beam-reducing mirror group 7 is 0.5, i.e. the light beam is compressed into a circular light beam with a diameter of 10 mm.
Focal length f of imaging lens group 4cam150mm, spot position sensor resolution (M N) 1024X 1024 units, pixel size (a) 8 μ M, effective field of view (CFOV) of the spot position sensor 3.129 DEG X3.129 DEG, diagonal field of view4.425 °, the calculation is as follows:
ideally, the image processor 6 outputs spot position information with a fine scale(s) of 1/80 pixels, an angular resolution (θ) of about 0.67 μ rad, and an output frequency of 2.5 KHz.
The angular resolution (θ) is calculated by:
the fiber field of view (FFOV) is defined as:
the image processor 6 is used for processing the image information to obtain light spot position information and sending the light spot position information to the controller 13; for processing the image information to calculate the spot tracking miss amount and sending the spot tracking miss amount to the controller 13.
The spot tracking fast mirror 1 is used to track the spot.
The tracking mirror driver 2 is used for sending the position information of the spot tracking fast reflecting mirror to the controller 13, and is used for receiving the tracking control signal sent by the controller 13 and driving the spot tracking fast reflecting mirror 1 to move accordingly.
The light spot position detector 5 is used for detecting the light spots to obtain image information and sending the image information to the controller 13.
The nutating coupling fast reflecting mirror 8 coupling mirror is used for nutating coupling.
The driver is used for sending out nutation coupling fast reflecting mirror position information to the controller 13, and is used for receiving a coupling control signal sent by the controller 13 and driving the nutation coupling fast reflecting mirror 8 to move according to the coupling control signal.
The light energy detector 12 is used for detecting the light energy of the light beam entering the light energy detector to obtain light energy information and sending the light energy information to the controller 13.
The controller 13 is configured to receive light spot position information sent by the image processor 6, receive tracking mirror position information sent by the tracking mirror driver 2, receive light energy information sent by the light energy detector 12, receive nutation coupling fast-reflection mirror position information sent by the coupling mirror driver 9, send a tracking control signal to the tracking mirror driver 2, and send a coupling control signal to the coupling mirror driver 9. The controller 13 obtains a tracking mirror control signal according to the received light spot position information and the tracking mirror position information, and the controller 13 obtains a coupling mirror control signal according to the received light energy information and the nutation coupling fast reflection mirror position information.
The controller 13 is further configured to determine whether the light beam is effectively imaged on the light spot position detector 5 according to the light spot position information sent by the image processor 6 to obtain a determination result; the controller 13 is also used for receiving the light spot tracking miss distance sent by the image processor 6 and calculating whether the light spot tracking miss distance is smaller than (optical fiber field/3) or not to obtain an analysis result; the controller 13 is also used for receiving the light energy information and analyzing and judging whether the light energy information reaches a threshold value.
Optical fiber field of view/3 ═ 2 ω0/3fn
A coupling method of an optical fiber coupling system, as shown in fig. 2, includes the following steps:
step 1, starting a light spot position detector 5, an image processor 6, a coupling mirror driver 9, a light energy detector 12 and a controller 13; the image processor 6 sends the spot position information to the controller 13, and the tracking mirror driver 2 sends the spot tracking micromirror position information to the controller 13.
Step 3, the controller 13 controls the light spot tracking fast reflecting mirror 1 to move to track the light spot through the tracking mirror driver 2 (if the primary judgment result in the step 2 is effective imaging, the controller 13 starts to control the light spot tracking fast reflecting mirror 1 to move to track the light spot through the tracking mirror driver 2, otherwise, the controller 13 continues to control the light spot tracking fast reflecting mirror 1 to track the light spot through the tracking mirror driver 2), the image processor 6 calculates the light spot tracking miss amount and sends the light spot tracking miss amount to the controller 13, the controller 13 receives the light spot tracking miss amount and analyzes and judges whether the light spot tracking miss amount is smaller than (optical fiber visual field/3) to obtain an analysis result, and if the analysis result is that the light spot tracking miss amount is smaller than (optical fiber visual field/3), namely Y, the step 4 is carried out; and if the analysis result is that the light spot tracking miss amount is larger than or equal to (optical fiber field of view/3), namely N, re-executing the step 3, namely the controller 13 controls the light spot tracking fast reflecting mirror 1 to continuously track the light spots through the tracking mirror driver 2 and the nutation coupling fast reflecting mirror 8 does not move until the light spot tracking miss amount is smaller than (optical fiber field of view/3), and then executing the step 4.
And 4, the controller 13 continuously controls the light spot tracking fast reflecting mirror 1 to move to track the light spots through the tracking mirror driver 2, and the controller 13 controls the nutation coupling fast reflecting mirror 8 to move through the coupling mirror driver 9 to carry out nutation coupling. Namely, the coupling mirror driver 9 drives the nutation coupling fast reflection mirror 8 to start moving, and the light energy detector 12 detects the light energy of the light beam entering the nutation coupling fast reflection mirror to obtain the light energy information.
After the coupling is finished in the step 5, the step 4 can be returned, the step 4 and the step 5 are repeated until the tracking mirror driver 2 and the coupling mirror driver 9 are stopped artificially, namely the step 6 of stopping the tracking mirror driver 2 artificially indicates that the facula tracking fast-reflecting mirror 1 keeps the current position, the step 6 of stopping the coupling mirror driver artificially indicates that the nutation coupling fast-reflecting mirror 8 keeps the current position, the manual stop corresponds to the stop of the figure 2, the manual stop is carried out when the figure is Y, and the step 4 is returned when the figure is N.
In the coupling process, namely in the steps, the facula tracking fast reflecting mirror 1 needs to continuously move in the whole process, namely, the starting controller 13 is started in the substep 1 to control the facula tracking fast reflecting mirror 1 to search or track facula through the tracking mirror driver 2 all the time, and how to control the movement controller 13 according to the actual situation is concrete; from step 4 to the end of the coupling, the nutating coupling fast reflecting mirror 8 moves all the time, that is, the controller 13 controls the nutating coupling fast reflecting mirror 8 to perform nutating coupling all the time through the coupling mirror driver 9.
An optical fiber coupling system adopts a hybrid optical fiber coupling technology based on facula nutation and position detection, a method of carrying out facula nutation coupling by adopting a high signal-to-noise ratio light energy detector 12 and a method of detecting optical fiber coupling energy on the basis of high-speed facula tracking are adopted to find an optimal coupling position; the light spot position is detected by combining a high-speed light spot position detector 5 with high resolution and large target surface, large-range and high-precision light spot tracking is realized, the small effective coupling view field in a single light spot nutation coupling technology is avoided, and the problems of high requirement on the alignment precision of a coupling light beam and low anti-interference capability are solved; the optical fiber coupling system finally realizes the optical fiber coupling technology with large effective view field, strong anti-interference capability and high coupling efficiency. The optical fiber coupling efficiency can be still maintained under the influence of atmospheric turbulence, the overall communication quality of a laser communication link is ensured, and the application range is wide. By adopting a coupling method based on an optical fiber coupling system, coarse alignment is performed before fine alignment is performed, and accurate, efficient and high-interference-resistant optical fiber coupling can be realized through a simple structure and a simple method.
The foregoing is only a preferred embodiment of the present invention, and it should be noted that, for those skilled in the art, various modifications and decorations can be made without departing from the principle of the present invention, and these modifications and decorations should also be regarded as the protection scope of the present invention.
Claims (10)
1. An optical fiber coupling system is characterized by comprising a light spot tracking fast reflecting mirror (1), a tracking mirror driver (2), a light splitting sheet (3), an imaging lens group (4), a light spot position detector (5), an image processor (6), a nutation coupling fast reflecting mirror (8), a coupling mirror driver (9), a coupling lens group (10), a coupling optical fiber (11), a light energy detector (12) and a controller (13); the light spot position detector (5) is placed on a focal plane of the imaging lens group (4), the end face of the optical fiber head of the coupling optical fiber (11) is placed on the focal plane of the coupling lens group (10), and the optical axis of the optical fiber head is coaxial with the optical axis of the coupling lens group (10);
the incident beam is incident on the light spot tracking fast reflecting mirror (1), and enters the light splitting sheet (3) after being reflected by the light spot tracking fast reflecting mirror (1), the light splitting sheet (3) divides the incident beam into a transmitted beam and a reflected beam, the transmitted beam is incident on the light spot position detector (5) after passing through the imaging lens group (4), and the reflected beam is reflected by the nutation coupling fast reflecting mirror (8), focused by the coupling lens group (10), coupled into the coupling optical fiber (11), and then enters the light energy detector (12);
when the light beam energy detected by the light energy detector (12) is maximum, the light spot detected by the light spot position detector (5) is superposed with the center of the target surface of the light spot position detector (5);
focal length f of coupling lens group (10)nSatisfy the requirement of
Wherein D is the aperture of the light beam incident on the coupling lens group (10), lambda is the wavelength of the incident light beam, and omega0Is the mode field radius of the coupling fiber (11).
2. A fiber coupling system according to claim 1, wherein the coincidence error of the spot with the center of the target surface of the spot position detector (5) is less than 1 pixel.
3. An optical fiber coupling system according to claim 1, wherein the spot tracking fast reflecting mirror (1) and the beam splitter (3) are sequentially arranged along the transmission direction of the incident beam, the imaging lens group (4) and the spot position detector (5) are sequentially arranged along the transmission direction of the transmitted beam, and the nutation coupling fast reflecting mirror (8), the coupling lens group (10), the coupling optical fiber (11) and the light energy detector (12) are sequentially arranged along the transmission direction of the reflected beam.
4. A fiber coupling system according to claim 1, wherein the system further comprises a beam reducing mirror group (7) disposed between the beam splitter (3) and the nutating coupling fast reflecting mirror (8), and the reflected beam reducing mirror group (7) is arranged to reduce the beam and then to be incident on the nutating coupling fast reflecting mirror (8).
5. A fiber coupling system according to claim 1, wherein the ratio of the intensity of the transmitted and reflected beams is 5%: 95 percent, the closed loop frequency of the facula tracking fast reflecting mirror (1) is 2.5kHz, the closed loop frequency of the nutation coupling fast reflecting mirror (8) is 10kHz, and the resolution of the facula position detector (5) is more than or equal to 1024 multiplied by 1024 pixels.
6. A fiber coupling system according to claim 1, wherein the image processor (6) is configured to process the image information to obtain spot position information and send the spot position information to the controller (13); the tracking mirror driver (2) is used for sending light spot tracking fast reflecting mirror position information to the controller (13), receiving a tracking control signal sent by the controller (13) and driving the light spot tracking fast reflecting mirror (1) to move according to the tracking control signal; the light spot position detector (5) is used for detecting light spots to obtain image information and sending the image information to the controller (13); the coupling mirror driver (9) is used for sending nutation coupling fast reflecting mirror position information to the controller (13) and receiving a coupling control signal sent by the controller (13) and driving the nutation coupling fast reflecting mirror (8) to move according to the coupling control signal; the light energy detector (12) is used for detecting light energy of the light beam entering the light energy detector to obtain light energy information and sending the light energy information to the controller (13);
the controller (13) is used for receiving light spot position information sent by the image processor (6), receiving tracking mirror position information sent by the tracking mirror driver (2), receiving light energy information sent by the light energy detector (12), receiving nutation coupling fast-reflection mirror position information sent by the coupling mirror driver (9), obtaining a tracking mirror control signal according to the received light spot position information and the tracking mirror position information, sending a tracking control signal to the tracking mirror driver (2), obtaining a coupling mirror control signal according to the received light energy information and the nutation coupling fast-reflection mirror position information, and sending a coupling control signal to the coupling mirror driver (9).
7. A fiber coupling system according to claim 6, wherein the image processor (6) is configured to process the image information to calculate a spot tracking miss amount and send the spot tracking miss amount to the controller (13); the controller (13) is used for receiving the light spot and tracking the miss distance.
8. An optical fiber coupling system according to claim 7, wherein the controller (13) is configured to determine whether the light beam is effectively imaged on the light spot position detector (5) according to the light spot position information sent by the image processor (6) to obtain a determination result, and to calculate whether the light spot tracking miss distance is less than 2 ω and less than 2 ω0/3fnAnd obtaining an analysis result, receiving the light energy information, and analyzing and judging whether the light energy information reaches a threshold value.
9. A method of coupling a fibre optic coupling system according to any of claims 1 to 8, comprising the steps of:
step 1, starting a light spot position detector (5), an image processor (6), a coupling mirror driver (9), a light energy detector (12) and a controller (13); the image processor (6) sends light spot position information to the controller (13), and the tracking mirror driver (2) sends light spot tracking fast-reflecting mirror position information to the controller (13);
step 2, the controller (13) receives the light spot position information sent by the image processor (6) and judges whether the light beam is effectively imaged on the light spot position detector (5) to obtain a judgment result, and when the judgment result is effective imaging, the step 3 is carried out; otherwise, the controller (13) receives the light spot tracking fast reflecting mirror position information sent by the tracking mirror driver (2), controls the tracking mirror driver (2) to drive the light spot tracking fast reflecting mirror (1) to move according to the light spot tracking fast reflecting mirror position information, searches light spots and executes the step 2 again;
step 3, the controller (13) controls the light spot tracking fast reflecting mirror (1) to move to track the light spots through the tracking mirror driver (2), the image processor (6) calculates the light spot tracking miss amount and sends the light spot tracking miss amount to the controller (13), and the controller (13) receives the light spot tracking miss amount and analyzes and judges whether the light spot tracking miss amount is smaller than 2 omega0/3fnObtaining an analysis result, if the analysis result is that the light spot tracking miss distance is less than 2 omega0/3fnThen go to step 4; if the analysis result shows that the light spot tracking miss amount is more than or equal to 2 omega0/3fnRe-executing the step 3;
step 4, the controller (13) controls the nutation coupling fast reflecting mirror (8) to move through the coupling mirror driver (9) to carry out nutation coupling;
step 5, the light energy detector (12) sends the obtained light energy information to the controller (13), the controller (13) receives the light energy information, and the controller (13) analyzes and judges whether the light energy information reaches a threshold value; if the light energy information reaches the threshold value, the optical fiber coupling system is coupled; otherwise, the controller (13) receives the nutation coupling fast reflecting mirror position information sent by the coupling mirror driver (9), the controller (13) calculates the next nutation position according to the light energy information, obtains a coupling control signal according to the nutation coupling fast reflecting mirror position information, sends the coupling control signal to the coupling mirror driver (9), the coupling mirror driver (9) receives the coupling control signal and drives the nutation coupling fast reflecting mirror (8) to reach the next nutation position according to the coupling control signal, meanwhile, the controller (13) controls the tracking mirror driver (2) to drive the light spot tracking fast reflecting mirror (1) to move, and the step 5 is executed again.
10. A method of coupling in a fiber coupling system according to claim 9, wherein said step 5 is followed by the step of returning to step 4 and repeating steps 4 and 5 until the tracking mirror driver (2) and the coupling mirror driver (9) are manually stopped.
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