Laser phase encoder for coherent detection and imaging

Abstract

The invention belongs to the technical field of phase delay, and particularly discloses a laser phase encoder for coherent detection and imaging, which comprises a phase delayer, the phase delayer comprises a first reflecting mirror and a second reflecting mirror, the first reflecting mirror and the second reflecting mirror are oppositely arranged to form a phase delay cavity, and the first reflecting mirror and the second reflecting mirror are arranged in parallel. Light input into the phase delayer is propagated in the phase delay cavity, the second reflector is provided with a fused biconical taper, the output end of the phase delayer is connected with a Bragg grating, at least two optical fiber rings are carved in the Bragg grating, the fused biconical taper is coupled with the two optical fiber rings, and the two optical fiber rings correspond to an input port and an output port of the Bragg grating respectively. When the optical paths of the sample light and the reference light are equal, an interference phenomenon can occur; the sample light is long in transmission distance and is in a changing state, and the phase delayer is used for the reference light to form phase coding so as to match all paths of the sample light. Wherein one of the two paths of input light is subjected to phase delay through a phase delayer, so that the optical path difference caused by the irradiation of the detection light to an object is matched, and an interference phase expansion condition is achieved.

Description

Technical Field

[0001] The invention relates to the technical field of phase delay, and in particular to a laser phase encoder for coherent detection and imaging. Background Art

[0002] Based on the transmission form and structure of the optical fiber, there are two types of optical fiber delay lines: incremental and continuously adjustable. At present, there are mainly the following types of incremental optical fiber delay lines: fixed optical fiber type, ring coupling type, multi-tap type and fiber Bragg grating (FBG) type. The delay time of these optical fiber delay lines is incrementally adjustable and non-continuously adjustable. They are composed of multiple optical fibers or optical waveguides, and each optical path has a different length. Through the selection of cascade optical switches, the optical signal passes through optical fibers or waveguides of different lengths, thereby obtaining different delay times. Since the path length changes incrementally, the delay time can only be incremental rather than continuously changing, with an accuracy of tens of picoseconds to hundreds of picoseconds, which basically depends on the cutting accuracy of the optical fiber. Limited by the current cutting process, the accuracy of the incremental optical fiber delay line is also limited, and it is difficult to adjust the delay time again after the optical fiber delay line is completed.

[0003] Therefore, high-precision continuously adjustable fiber optic delay lines came into being. High-precision continuously adjustable fiber optic delay lines use air as the light transmission path, change the path length by moving the reflecting mirror, solve the problem of unadjustable delay time, and use a high-precision CNC stepper motor to control the accuracy of mirror movement to continuously delay time.

[0004] However, relying solely on high-precision continuously adjustable optical fiber delay lines cannot meet the adjustment requirements of the coherent optical path for optical path matching in coherent laser detection. Summary of the invention

[0005] In view of the above-mentioned deficiencies in the prior art, an object of the present invention is to provide a laser phase encoder for coherent detection and imaging, which provides a precisely adjustable long optical path by designing a phase delay device for optical path matching of coherent laser detection.

[0006] In order to achieve the above object, the present invention adopts the following technical scheme:

[0007] A laser phase encoder for coherent detection and imaging comprises a phase retarder, wherein the phase retarder comprises a first reflector and a second reflector, wherein the first reflector and the second reflector are arranged relative to each other to form a phase delay cavity, wherein light input into the phase retarder propagates in the phase delay cavity, wherein a fused taper is arranged on the second reflector, wherein the output end of the phase retarder is connected to a Bragg grating, wherein at least two optical fiber rings are engraved in the Bragg grating, wherein the fused taper couples the two optical fiber rings, and wherein the two optical fiber rings correspond to the input and output ports of the Bragg grating, respectively.

[0008] In a preferred embodiment, the optical path of light in the phase delay cavity is:

[0009] Δ r =L / sinθ

[0010] In the formula, Δ r is the optical path of light in the phase delay cavity, L is the length of the phase delay cavity, and θ is the incident angle.

[0011] In a preferred embodiment, the phase delay device is provided in plurality, and the plurality of phase delay devices are connected in sequence.

[0012] In a preferred embodiment, it also includes a first optical switch and a second optical switch; among the multiple phase delayers connected in sequence, the input end of the first phase delayer is connected to one of the first optical switches, the output end of the last phase delayer is connected to one of the first optical switches, and one of the second optical switches is respectively arranged between the middle phase delayer and the adjacent phase delayer.

[0013] In a preferred embodiment, the first optical switch is a 1*2 optical switch.

[0014] In a preferred embodiment, the second optical switch is a 2*2 optical switch.

[0015] In a preferred embodiment, the lengths of the plurality of phase retarders are different.

[0016] In a preferred embodiment, along the optical path, the lengths of the phase retarders decrease irregularly.

[0017] In a preferred embodiment, the first optical switch is connected to a single-mode optical fiber.

[0018] In a preferred embodiment, the fiber optic rings are arranged in four numbers, namely, a first fiber optic ring, a second fiber optic ring, a third fiber optic ring, and a fourth fiber optic ring, and the fused taper is coupled with the first fiber optic ring and the second fiber optic ring; the light entering the Bragg grating passes through the first fiber optic ring, the second fiber optic ring, the third fiber optic ring, the fourth fiber optic ring, and the first fiber optic ring at least once, and then is reflected from the second fiber optic ring under the control of the fused taper.

[0019] Compared with the prior art, the present invention has the following beneficial effects:

[0020] The core of the encoder is the phase delay device, which can provide an adjustable long optical path for optical path matching of coherent laser detection. When the optical paths of the sample light and the reference light are equal, interference can occur. The sample light has a long transmission distance and is in a changing state. The phase delay device is used to form phase encoding with the reference light to match all paths of the sample light. One of the two input lights is phase-delayed by the phase delay device to match the optical path difference caused by the detection light irradiating the object and achieve the interference phase increase condition. BRIEF DESCRIPTION OF THE DRAWINGS

[0021] In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the drawings required for use in the embodiments or the description of the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on the structures shown in these drawings without paying creative work.

[0022] Figure 1 A simplified structural diagram of a laser phase encoder for coherent detection and imaging provided in an embodiment of the present invention.

[0023] Figure 2 A simplified optical path diagram of a laser phase encoder for coherent detection and imaging provided in an embodiment of the present invention.

[0024] Figure 3 A schematic diagram of splicing multiple phase delay devices provided in an embodiment of the present invention.

[0025] Figure 4 A simplified optical path diagram of a laser phase encoder for coherent detection and imaging provided by an embodiment of the present invention when multiple phase retarders are provided.

[0026] Reference numerals:

[0027] 100, phase retarder; 101, first reflector; 102, second reflector; 103, phase delay cavity plate; 104, fused taper; 105, Bragg grating; A, incident port of Bragg grating; B, first optical fiber ring; D, second optical fiber ring; E, third optical fiber ring; F, fourth optical fiber ring;

[0028] 200. a first optical switch;

[0029] 300. a second optical switch;

[0030] 400, single-mode optical fiber. DETAILED DESCRIPTION

[0031] The following describes the embodiments of the present invention by specific examples, and those skilled in the art can easily understand other advantages and effects of the present invention from the contents disclosed in this specification. The present invention can also be implemented or applied through other different specific embodiments, and the details in this specification can also be modified or changed in various ways based on different viewpoints and applications without departing from the spirit of the present invention. It should be noted that the following embodiments and features in the embodiments can be combined with each other without conflict.

[0032] In the description of the present invention, unless otherwise specified, "plurality" means two or more than two; the orientations or positional relationships indicated by the terms "upper", "lower", "left", "right", "inner", "outer", "front end", "rear end", "head", "tail", etc. are based on the orientations or positional relationships shown in the drawings, and are only for the convenience of describing the present invention and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, be constructed and operate in a specific orientation, and therefore cannot be understood as limiting the present invention. In addition, the terms "first", "second", "third", etc. are only used for descriptive purposes and cannot be understood as indicating or implying their relative importance.

[0033] In the description of the present invention, it should be noted that, unless otherwise clearly specified and limited, the terms "connected" and "connection" should be understood in a broad sense, for example, it can be a fixed connection, a detachable connection, or an integral connection; it can be a mechanical connection or an electrical connection; it can be a direct connection or an indirect connection through an intermediate medium. For ordinary technicians in this field, the specific meanings of the above terms in the present invention can be understood according to specific circumstances.

[0034] The present invention will now be further described with reference to the accompanying drawings.

[0035] Figure 1 A simplified structural diagram of a laser phase encoder for coherent detection and imaging provided in an embodiment of the present invention. Figure 2 A simplified optical path diagram of a laser phase encoder for coherent detection and imaging provided by an embodiment of the present invention. Figure 1 and Figure 2As shown, an embodiment of the present invention provides a laser phase encoder for coherent detection and imaging, the laser phase encoder includes a phase retarder 100, the phase retarder 100 includes a first reflector 101 and a second reflector 102, the first reflector 101 and the second reflector 102 are arranged relative to each other to form a phase delay cavity 103, the light input to the phase retarder 100 propagates in the phase delay cavity 103, a fused taper 104 is arranged on the second reflector 102, the output end of the phase retarder 100 is connected to a Bragg grating 105, at least two optical fiber rings are engraved in the Bragg grating 105, the fused taper 104 couples the two optical fiber rings, and the two optical fiber rings correspond to the input and output ports of the Bragg grating 105 respectively.

[0036] In this embodiment, compared with the traditional high-precision continuously adjustable optical fiber delay line, a Bragg grating 105 is additionally designed, and the input and output ports of the Bragg grating 105 are coupled by a fused taper 104, so as to further add a means of adjusting the optical path on the basis of adjusting the optical path by the first reflector 101 and the second reflector 102, so that the reference light of one of the two input lights is phase delayed by the phase delay device, and the optical path difference is more easily adjusted to the same optical path as the sample light, thereby matching the optical path difference caused by the detection light irradiating the object and achieving the interference phase expansion condition.

[0037] In some embodiments, Figure 2 As shown, there are four optical fiber rings, namely, a first optical fiber ring B, a second optical fiber ring D, a third optical fiber ring E, and a fourth optical fiber ring F. The fused taper 104 is coupled with the first optical fiber ring B and the second optical fiber ring D. The light entering the Bragg grating 105 passes through the first optical fiber ring B, the second optical fiber ring D, the third optical fiber ring E, the fourth optical fiber ring F, and the first optical fiber ring B at least once, and then is reflected from the second optical fiber ring D under the control of the fused taper 104.

[0038] Specifically, BDERB is a fiber ring with Bragg gratings engraved in it. Two input and output ports are coupled at B and E respectively by fused taper. Light incident from port A passes through the Bragg grating and circulates through BDEFB. The Bragg grating applies stress and the light is reflected from port D. In actual implementation, the optical path can be adjusted by adjusting the number of cycles.

[0039] In some embodiments, the optical path of light in the phase delay cavity is:

[0040] Δ r =L / sinθ

[0041] In the formula, Δ r is the optical path of light in the phase delay cavity, L is the length of the phase delay cavity, and θ is the incident angle.

[0042] It should be noted that the optical path can be adjusted by the first reflector 101 and the second reflector 102, because the optical path is very sensitive to the incident angle θ. Among them, the method of adjusting the optical path by the first reflector 101 and the second reflector 102 is a prior art. For example, the incident angle can be adjusted by moving the first reflector 101 and / or the second reflector 102. In this embodiment, the phase delay 100 of different lengths can be set to a fixed incident angle, and the optical path can be further adjusted by the Bragg grating. Exemplarily, the angle corresponding to 5km is 0.0005 degrees, and the corresponding piezoelectric displacement is 4um. The accuracy of piezoelectric ceramics is 0.01nm, so the optical path can be precisely adjusted.

[0043] In some embodiments, the phase delayer 100 is provided in plurality, and the plurality of phase delayers 100 are connected in sequence. The plurality of phase delayers 100 are connected in sequence in a cascade manner, such as the output end of a phase delayer is connected to the input end of another phase delayer.

[0044] In some embodiments, the lengths of the plurality of phase retarders 100 are different, and along the optical path, the lengths of the phase retarders 100 decrease irregularly.

[0045] For example, Figure 3 A schematic diagram of splicing multiple phase delay devices provided by an embodiment of the present invention. Figure 3 As shown, by using 500m, 100m, 20m, and 4m large-step fiber Bragg grating delayers, and cascading them with a high-precision flat-plate phase delay with an adjustment range of 0-4m, 0-5km fast and high-precision phase delay can be achieved.

[0046] Figure 4 A simplified optical path diagram of a laser phase encoder for coherent detection and imaging provided by an embodiment of the present invention when multiple phase delay devices are set, such as Figure 4 As shown, the laser phase encoder for coherent detection and imaging also includes a first optical switch 200 and a second optical switch 300; among the multiple phase delayers 100 connected in sequence, the input end of the first phase delayer 100 is connected to a first optical switch 200, the output end of the last phase delayer 300 is connected to a first optical switch 200, and a second optical switch 300 is respectively arranged between the middle phase delayer 100 and the adjacent phase delayer 100, and the first optical switch 200 is connected to the single-mode optical fiber 400.

[0047] Exemplarily, the first optical switch 100 is a 1*2 optical switch; and the second optical switch 200 is a 2*2 optical switch. Figure 4In the figure, two distances are shown between the two optical switches. The upper distance represents the optical path of the phase retarder (adjusted according to the actual situation), and the lower distance represents the distance between the two optical switches (both 0.5m).

[0048] In one embodiment, a controller may be provided for controlling the delay time, and the controller is connected to the phase delay device to issue a delay time control instruction. The delay time control instruction consists of 4 bytes, the baud rate is 115200, and the format is 0xaa 0x000x000x00. The header byte is fixed to 0xaa, the middle byte is the low position of the control gear, and the last byte is the high position of the control gear. Each gear value represents a step value, i.e., 5 cm.

[0049] The above embodiments are only used to illustrate the technical solutions of the present invention, rather than to limit the same. Although the present invention has been described in detail with reference to the above embodiments, those skilled in the art should understand that the technical solutions described in the above embodiments may still be modified, or some or all of the technical features may be replaced by equivalents. Such modifications or replacements do not deviate the essence of the corresponding technical solutions from the scope of the technical solutions of the embodiments of the present invention, and should all be included in the scope of the claims and specification of the present invention.

Claims

1. A laser phase encoder for coherent detection and imaging, characterized in that: The invention comprises a phase retarder, wherein the phase retarder comprises a first reflector and a second reflector, wherein the first reflector and the second reflector are arranged relative to each other to form a phase delay cavity, wherein light input into the phase retarder propagates in the phase delay cavity, wherein a fused taper is arranged on the second reflector, wherein the output end of the phase retarder is connected to a Bragg grating, wherein at least two optical fiber rings are engraved in the Bragg grating, wherein the fused taper couples the two optical fiber rings, and wherein the two optical fiber rings correspond to the input and output ports of the Bragg grating, respectively.

2. The laser phase encoder for coherent detection and imaging according to claim 1, characterized in that: The optical path of light in the phase delay cavity is: D r =L / sinθ In the formula, Δ r is the optical path of light in the phase delay cavity, L is the length of the phase delay cavity, and θ is the incident angle.

3. The laser phase encoder for coherent detection and imaging according to claim 1, characterized in that: The phase delay device is provided in a plurality, and the plurality of phase delay devices are connected in sequence.

4. The laser phase encoder for coherent detection and imaging according to claim 3, characterized in that: It also includes a first optical switch and a second optical switch; among the multiple phase delayers connected in sequence, the input end of the first phase delayer is connected to the first optical switch, the output end of the last phase delayer is connected to the first optical switch, and the second optical switch is respectively arranged between the middle phase delayer and the adjacent phase delayer.

5. The laser phase encoder for coherent detection and imaging according to claim 4, characterized in that: The first optical switch is a 1*2 optical switch.

6. The laser phase encoder for coherent detection and imaging according to claim 4, characterized in that: The second optical switch is a 2*2 optical switch.

7. The laser phase encoder for coherent detection and imaging according to claim 3, characterized in that: The lengths of the multiple phase retarders are different.

8. The laser phase encoder for coherent detection and imaging according to claim 3, characterized in that: Along the optical path, the lengths of the phase retarders decrease irregularly.

9. The laser phase encoder for coherent detection and imaging according to claim 4, characterized in that: The first optical switch is connected to a single-mode optical fiber.

10. The laser phase encoder for coherent detection and imaging according to claim 1, characterized in that: The optical fiber rings are arranged in four numbers, namely, a first optical fiber ring, a second optical fiber ring, a third optical fiber ring, and a fourth optical fiber ring. The fused taper is coupled with the first optical fiber ring and the second optical fiber ring. The light entering the Bragg grating is reflected from the second optical fiber ring under the control of the fused taper after circulating through the first optical fiber ring, the second optical fiber ring, the third optical fiber ring, the fourth optical fiber ring, and the first optical fiber ring at least once.

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