Three-port reflective optical circulator based on birefringent crystal

Abstract

The invention discloses a birefringent crystal-based three-port reflective optical circulator, which belongs to the field of optical communication and comprises a first birefringent crystal, a half-wave plate assembly, a roof prism, a Faraday optical rotation crystal, a second birefringent crystal, a 1 / 4 wave plate and a reflector which are sequentially arranged, the first port, the second port and the third port are located on the side, away from the half-wave plate assembly, of the first birefringent crystal, light splitting is carried out through the birefringent crystals, and a light beam is divided into two sub light beams o polarized light and e polarized light with the polarization directions perpendicular to each other. The polarization direction of the sub-beams is controlled through the half-wave plate, the 1 / 4 wave plate and the Faraday optical rotation crystal, and finally light combination is carried out through the birefringent crystal, so that the functions of first port input, second port output, second port input and third port output of the optical circulator are realized, the three ports are located on the same side of the optical circulator, and the optical circulator has a wide application prospect. Other parts are convenient to place, and the optical circulator can be miniaturized.

Description

Technical Field

[0001] The invention relates to the field of optical communication, in particular to a three-port reflective optical circulator based on a birefringent crystal. Background Art

[0002] Optical circulator is a very important non-reciprocal optical passive device with multi-port input and output in fiber-optic communication systems. Its function is to make the optical signal only be transmitted in a ring along the specified port sequence. It has the characteristics of forward sequential transmission and reverse sequential isolation, and can complete the separation of forward and reverse transmission light. Therefore, it is widely used in single-fiber bidirectional transmission systems, fiber Bragg grating-based dense wavelength division multiplexers, optical amplifiers, optical time domain reflectometers, as well as in traditional fields such as fiber sensing and fiber testing.

[0003] The three ports of a conventional three-port optical circulator based on a birefringent crystal are located on different sides of the circulator. This structure not only leads to structural redundancy, but also requires consideration of the placement of components in the module when designing the optical path, resulting in the inability to miniaturize the optical circulator. Summary of the invention

[0004] In order to overcome the shortcomings of the prior art, one of the objectives of the present invention is to provide a three-port reflective optical circulator based on a birefringent crystal, in which the three ports are located on the same side of the optical circulator.

[0005] One of the purposes of the present invention is achieved by the following technical solution:

[0006] A three-port reflective optical circulator based on a birefringent crystal is provided with a first port, a second port, a third port, a first birefringent crystal, a half-wave plate assembly, a roof prism, a Faraday rotator crystal, a second birefringent crystal, a quarter wave plate and a reflector arranged in sequence, wherein the first port, the second port and the third port are respectively located at a side of the first birefringent crystal away from the half-wave plate assembly,

[0007] When the optical path from the first port to the second port is working, the angled light beam emitted from the first port is decomposed into o light and e light through the first birefringent crystal, the o light is deflected 45° clockwise through the half-wave plate component, the e light is rotated 135° clockwise, and the roof prism collimates the angled o light and e light into parallel light beams; the Faraday rotator crystal rotates the o light and e light by 45° clockwise to form two beams of o light, and the two beams of o light pass through the second birefringent crystal and the 1 / After passing through the 4-wave plate, the two beams of light are reflected by the reflector, and the two beams of light after reflection are transformed into two beams of e light through the 1 / 4 wave plate. The two beams of e light are deflected to the right in the second birefringent crystal, and rotated 45° clockwise through the Faraday rotator crystal. After passing through the roof prism, the sub-beam on the left is rotated 45° counterclockwise through the half-wave plate component to become o light, and the sub-beam on the right is rotated 135° clockwise through the half-wave plate component to become e light. The o light and the e light are combined in the first birefringent crystal and emitted into the second port;

[0008] When the optical path channel from the second port to the third port is working, the parallel light beam emitted from the first port is decomposed into o light and e light through the first birefringent crystal, the o light is deflected 45° clockwise through the half-wave plate assembly, and the e light is rotated 135° clockwise. After passing through the roof prism, the Faraday rotator crystal rotates the o light and the e light by 45° clockwise to form two beams of o light. The two beams of o light pass through the second birefringent crystal and the 1 / 4 wave plate and are reflected by the reflector. The two beams of reflected light pass through the 1 / 4 wave plate and become two beams of e light. The two beams of e light are deflected to the right in the second birefringent crystal, rotated 45° clockwise through the Faraday rotator crystal, deflected to the left when passing through the roof prism, and then pass through the half-wave plate assembly. The sub-beam on the left is rotated 45° counterclockwise and converted into o light, and the sub-beam below is rotated 135° clockwise and is still e light. The o light and the e light are combined in the first birefringent crystal and emitted into the third port.

[0009] Furthermore, the first port, the second port and the third port are located in the same horizontal plane.

[0010] Furthermore, the second port is located between the first port and the third port.

[0011] Furthermore, the half-wave plate assembly includes two half-wave plates, and the two half-wave plates are arranged on the left and right.

[0012] Furthermore, the first birefringent crystal has a tilt angle.

[0013] Furthermore, the cross section of the first birefringent crystal along the optical path is a parallelogram.

[0014] Furthermore, the side surface of the first birefringent crystal facing the first port is tilted to the right.

[0015] Furthermore, the three-port reflective optical circulator based on the birefringent crystal further includes a three-fiber collimator, and the three-fiber collimator is located on a side of the first birefringent crystal away from the half-wave plate assembly.

[0016] Furthermore, the three-fiber collimator forms the first port, the second port and the third port.

[0017] Furthermore, the three-fiber collimator is located between the first port, the second port, the third port and the first birefringent crystal.

[0018] Furthermore, the three-port reflective optical circulator based on birefringent crystal also includes a filter, and the filter is located between the roof prism and the reflector.

[0019] Further, the optical filter is located between the 1 / 4 wave plate and the reflecting mirror or the optical filter is located between the second birefringent crystal and the 1 / 4 wave plate.

[0020] Compared with the prior art, the three-port reflective optical circulator based on birefringent crystal of the present application includes a first birefringent crystal, a half-wave plate assembly, a roof prism, a Faraday rotator crystal, a second birefringent crystal, a quarter-wave plate and a reflector arranged in sequence, the first port, the second port and the third port are respectively located on the side of the first birefringent crystal away from the half-wave plate assembly, the light beam is split by the birefringent crystal, and the light beam is divided into two sub-beams of o-polarized light and e-polarized light with polarization directions perpendicular to each other, and the polarization directions of the sub-beams are controlled by the half-wave plate, the quarter-wave plate and the Faraday rotator crystal, and finally the light is combined by the birefringent crystal, so that the functions of the optical circulator at the first port input and the second port output and the second port input and the third port output are realized, so that the three ports are located on the same side of the optical circulator, so that other components are easy to place, and the optical circulator can be miniaturized. BRIEF DESCRIPTION OF THE DRAWINGS

[0021] Figure 1 It is a schematic structural diagram of a three-port reflective optical circulator based on a birefringent crystal according to the present invention;

[0022] Figure 2 for Figure 1 A side view of the optical path of a three-port reflective optical circulator based on a birefringent crystal, wherein light enters from a first port and exits from a second port;

[0023] Figure 3 for Figure 2A schematic diagram of the polarization direction of light entering from the first port and emitted from the second port observed from the perspective of the incident light;

[0024] Figure 4 A top view of the optical path of the incident light of the three-port reflective optical circulator based on the birefringent crystal of the present invention;

[0025] Figure 5 A top view of the optical path of the outgoing light of the three-port reflective optical circulator based on the birefringent crystal of the present invention;

[0026] Figure 6 for Figure 1 A side view of the optical path of a three-port reflective optical circulator based on a birefringent crystal, wherein light enters from the second port and exits from the third port;

[0027] Figure 7 for Figure 6 Schematic diagram of the polarization direction of light entering from the second port and emitted from the third port observed from the perspective of the incident light.

[0028] In the figure: 101, three-fiber collimator; 102, first birefringent crystal; 103, half-wave plate assembly; 104, roof prism; 105, Faraday rotator crystal; 106, second birefringent crystal; 107, 1 / 4 wave plate; 108, filter; 109, reflector. DETAILED DESCRIPTION

[0029] The following will be combined with the drawings in the embodiments of the present invention to clearly and completely describe the technical solutions in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0030] It should be noted that when a component is referred to as being "fixed to" another component, it may be directly on the other component or there may be another intermediate component through which it is fixed. When a component is considered to be "connected to" another component, it may be directly connected to the other component or there may be another intermediate component at the same time. When a component is considered to be "set on" another component, it may be directly set on the other component or there may be another intermediate component at the same time. The terms "vertical", "horizontal", "left", "right" and similar expressions used herein are for illustrative purposes only.

[0031] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as those commonly understood by those skilled in the art of the present invention. The terms used herein in the specification of the present invention are only for the purpose of describing specific embodiments and are not intended to limit the present invention. The term "and / or" used herein includes any and all combinations of one or more related listed items.

[0032] See also Figure 1 The three-port reflective optical circulator based on the birefringent crystal is provided with a first port P1, a second port P2 and a third port P3, and the first port P1, the second port P2 and the third port P3 are located on the same side of the optical circulator. Specifically, the first port P1, the second port P2 and the third port P3 are located at the same horizontal height, and the second port P2 is located between the first port P1 and the third port P3.

[0033] The three-port reflective optical circulator based on birefringent crystal includes a three-fiber collimator 101, a first birefringent crystal 102, a half-wave plate assembly 103, a roof prism 104, a Faraday rotator crystal 105, a second birefringent crystal 106, a quarter-wave plate 107, a filter 108 and a reflector 109 which are arranged in sequence.

[0034] The first port P1, the second port P2 and the third port P3 are located on the side of the three-fiber collimator 101 away from the first birefringent crystal 102. The first port P1, the second port P2 and the third port P3 are optical fibers. The three-fiber collimator 101 collimates the light emitted from the first port P1 or the second port P2, or collimates the light emitted to the second port P2 or the third port P3.

[0035] In other embodiments, the first port P1 , the second port P2 , and the third port P3 may also be disposed inside the three-fiber collimator 101 .

[0036] The first birefringent crystal 102 has a tilt angle. Specifically, the cross section of the first birefringent crystal 102 along the optical path is a parallelogram. In this embodiment, the side surface of the first birefringent crystal 102 facing the first port is tilted downward.

[0037] The half-wave plate assembly 103 includes two half-wave plates, which are arranged on the left and right.

[0038] The filter 108 filters out light beams of unnecessary wavelengths, so that the incident light is transmitted as a light beam within a specified wavelength range.

[0039] Please continue reading Figures 2 to 5 When the optical circulator is in the first port P1-> second port P2 optical path, the propagation direction of the light beam is as follows: Figure 2 , Figure 4 as well as Figure 5 As shown, Figure 2 The middle is a side view of the beam propagation. Figure 4 is the top view of the incident light, Figure 5 is the top view of the outgoing light, Figure 3 Schematic diagram of the polarization direction of light after passing through each optical element, observed from the perspective of incident light.

[0040] At this time, the divergent light beam emitted from the first port first passes through the three-fiber collimator 101 and is collimated into an angled light beam; the angled light beam passes through the first birefringent crystal 102, and the angled light beam is decomposed into two sub-beams with orthogonal polarization directions, ordinary light o and extraordinary light e. Since the first birefringent crystal 102 has a certain tilt angle, according to the law of refraction, the o light is deflected to the left. According to the separation angle principle of the birefringent crystal, the extraordinary light e will produce a separation angle in the birefringent crystal, so the e light is deflected to the right; after passing through the half-wave plate assembly 103, the o light is transmitted in the left optical path, so after passing through the half-wave plate on the left side of the half-wave plate assembly 103, the polarization direction of the o light is rotated 45° clockwise along the incident light direction. The e-light is transmitted in the optical path on the right side, so after passing through the half-wave plate on the right side of the half-wave plate assembly 103, the polarization direction of the e-light is rotated 135° clockwise along the light transmission direction; after passing through the roof prism 104, the angled o-light and e-light are collimated into parallel light beams after passing through the roof prism 104; after passing through the Faraday rotator crystal 105, the polarization directions of the two sub-light beams are rotated 45° clockwise along the incident light direction, and at this time, the two sub-light beams are both o-light. After passing through the second birefringent crystal 106, since both sub-beams are o-light, neither of the two sub-beams will be deflected; after passing through the 1 / 4 wave plate 107, the filter 108 filters out the light beams of unnecessary wavelengths, so that the incident light is transmitted as a light beam in a specified wavelength range, and the light beam is transmitted to the reflector 109, and after reflection, it passes through the 1 / 4 wave plate 107 again. At this time, the two sub-beams are equivalent to passing through the 1 / 4 wave plate with the same optical axis direction twice, which is equivalent to passing through a half-wave plate. At this time, the polarization directions of the two sub-beams are rotated 90° clockwise along the light transmission direction, that is, the two sub-beams are changed from o-light to e-light; the two After the sub-beams are reflected, they pass through the second birefringent crystal 106. With respect to the second birefringent crystal 106, both sub-beams are e-light, so they are both deflected downward; after the sub-beams are reflected, they pass through the Faraday rotation crystal 105, and the polarization directions of the two sub-beams rotate 45° clockwise along the incident light direction; after the sub-beams are reflected, they pass through the roof prism 104. Since the two sub-beams are incident on the roof prism 104 vertically at this time, they will not be deflected; then they pass through the half-wave plate assembly 103, and the sub-beam on the left passes through the wave plate on the left side of the half-wave plate assembly 103, and the polarization direction rotates 45° counterclockwise along the light propagation direction. At this time, the sub-beam on the left is converted from e-light to o-light. The sub-beam on the right passes through the wave plate on the right side of the half-wave plate assembly 103, and the polarization direction rotates 135° clockwise along the light propagation direction. At this time, the sub-beam on the right still maintains the polarization state of e-light; finally, they pass through the first birefringent crystal 102. Since the first birefringent crystal 102 has a certain tilt angle, according to the law of refraction, the o-light is deflected to the right. According to the separation angle principle of the birefringent crystal, the extraordinary light e-light will produce a deviation angle in the birefringent crystal, so the e-light is deflected to the left. At this time, the o-light and the e-light are combined after passing through the first birefringent crystal 102 and finally transmitted to the second port P2.

[0041] Please continue reading Figures 4 to 7 When the optical circulator is in the first port P2->second port P3 optical path channel operation, the top view of the light beam propagation direction is the same as when the first port P1->second port P2 optical path channel operation, such as Figure 4 as well as Figure 5 The side view of the beam propagation is shown in Figure 6 As shown, the polarization direction of light after passing through each optical element is as follows Figure 7 shown.

[0042] At this time, the divergent light beam outputted by the optical fiber at the P2 end first passes through the three-fiber collimator 101 and is collimated into a parallel light beam; the parallel light beam passes through the first birefringent crystal 102, and the parallel light beam is decomposed into two sub-beams with orthogonal polarization directions, ordinary light o and extraordinary light e. Since the first birefringent crystal 102 has a certain tilt angle, according to the law of refraction, the o light is deflected to the left. According to the separation angle principle of the birefringent crystal, the extraordinary light e will produce a separation angle in the birefringent crystal, so the e light is deflected to the right; after passing through the half-wave plate assembly 103, the o light is transmitted in the left optical path, so after passing through the half-wave plate on the left side of the half-wave plate assembly 103, the polarization direction of the o light is rotated 45° clockwise along the incident light direction. The e-light is transmitted in the optical path on the right side, so after passing through the half-wave plate on the right side of the half-wave plate assembly 103, the polarization direction of the e-light rotates 135 degrees clockwise along the optical transmission direction; after passing through the roof prism 104, since both sub-beams are incident on the roof prism 104 vertically, no deflection occurs; after passing through the Faraday rotator crystal 105, the polarization directions of the two sub-beams rotate 45 degrees clockwise along the optical path transmission direction. At this time, both sub-beams are o-light. After passing through the second birefringent crystal, since both sub-beams are o-light, neither of the two sub-beams will be deflected; after passing through the 1 / 4 wave plate 107, the light beam passes through the filter 108, and the filter 108 selectively passes the light signal of a specific wavelength. The light beam is transmitted to the reflector 109, and after reflection, it passes through the 1 / 4 wave plate 107 again. At this time, the two sub-beams are equivalent to passing through the 1 / 4 wave plate 107 with the same optical axis direction twice, which is equivalent to passing through a half-wave plate. At this time, the polarization directions of the two sub-beams are rotated 90° clockwise along the light transmission direction, that is, the two sub-beams are changed from o-light to e-light; the two sub-beams are reflected After passing through the second birefringent crystal 106, since both sub-beams are e-light, they are both deflected to the right; after reflection, they pass through the Faraday rotation crystal 105, and the polarization directions of the two sub-beams rotate 45° clockwise along the light propagation direction; after reflection, they pass through the roof prism 104, and the two sub-beams form a certain angle with the roof prism 104. After refraction, the sub-beams are deflected toward the third port P3 (deflected to the left); after passing through the half-wave plate assembly 103, the sub-beam on the left passes through the wave plate on the left side of the half-wave plate assembly 103, and the polarization direction rotates 135° clockwise along the light propagation direction. At this time, the sub-beam on the right is converted from e-light to o-light. The sub-beam below passes through the wave plate below the half-wave plate assembly 103, and the polarization direction rotates 45° clockwise along the light propagation direction. At this time, the sub-beam on the right still maintains the polarization state of e-light; finally, it passes through the first birefringent crystal 102. Since the first birefringent crystal 102 has a certain tilt angle, according to the law of refraction, the o-light is deflected to the right. According to the separation angle principle of the birefringent crystal, the extraordinary light e-light will produce a deviation angle in the birefringent crystal, so the e-light is deflected to the left. At this time, the o-light and the e-light are combined after passing through the first birefringent crystal 102 and finally transmitted to the third port P3.

[0043] The three-port reflective optical circulator based on birefringent crystals of the present application performs light splitting through birefringent crystals, and divides the light beam into two sub-beams of o-polarized light and e-polarized light with mutually perpendicular polarization directions, and controls the polarization directions of the sub-beams through half-wave plate assembly 103, 1 / 4 wave plate 104 and Faraday rotator crystal 105, and finally combines the light through birefringent crystals, realizing the functions of the optical circulator input at the first port, output at the second port, and input at the second port, output at the third port, so that the three ports are located on the same side of the optical circulator, so that other components are easy to place, and the optical circulator can be miniaturized. This design not only greatly reduces the spatial size of the equipment and improves the utilization efficiency of materials, but also the compact structure provides greater flexibility and adaptability for the optical circulator in a variety of application scenarios, giving the optical circulator a wider range of practical application potential, so as to better adapt to the stringent requirements of space utilization in modern optical systems.

[0044] The above embodiments only express several implementation methods of the present invention, and the descriptions thereof are relatively specific and detailed, but they cannot be understood as limiting the scope of the invention patent. It should be pointed out that, for ordinary technicians in this field, several modifications and improvements can be made without departing from the concept of the present invention, which are equivalent modifications and improvements made to the above embodiments based on the essential technology of the present invention, and all of them belong to the protection scope of the present invention.

Claims

1. A three-port reflective optical circulator based on a birefringent crystal, having a first port, a second port and a third port, characterized in that: The three-port reflective optical circulator based on the birefringent crystal also includes a first birefringent crystal, a half-wave plate assembly, a roof prism, a Faraday rotator crystal, a second birefringent crystal, a quarter-wave plate and a reflector, which are arranged in sequence. The first port, the second port and the third port are respectively located on a side of the first birefringent crystal away from the half-wave plate assembly. When the optical path from the first port to the second port is working, the angled light beam emitted from the first port is decomposed into o light and e light through the first birefringent crystal, the o light is deflected 45° clockwise through the half-wave plate component, the e light is rotated 135° clockwise, and the roof prism collimates the angled o light and e light into parallel light beams; the Faraday rotator crystal rotates the o light and e light by 45° clockwise to form two beams of o light, and the two beams of o light pass through the second birefringent crystal and the 1 / After passing through the 4-wave plate, the two beams of light are reflected by the reflector, and the two beams of light after reflection are transformed into two beams of e light through the 1 / 4 wave plate. The two beams of e light are deflected to the right in the second birefringent crystal, and rotated 45° clockwise through the Faraday rotator crystal. After passing through the roof prism, the sub-beam on the left is rotated 45° counterclockwise through the half-wave plate component to become o light, and the sub-beam on the right is rotated 135° clockwise through the half-wave plate component to become e light. The o light and the e light are combined in the first birefringent crystal and emitted into the second port; When the optical path channel from the second port to the third port is working, the parallel light beam emitted from the first port is decomposed into o light and e light through the first birefringent crystal, the o light is deflected 45° clockwise through the half-wave plate assembly, and the e light is rotated 135° clockwise. After passing through the roof prism, the Faraday rotator crystal rotates the o light and the e light by 45° clockwise to form two beams of o light. The two beams of o light pass through the second birefringent crystal and the 1 / 4 wave plate and are reflected by the reflector. The two beams of reflected light pass through the 1 / 4 wave plate and become two beams of e light. The two beams of e light are deflected to the right in the second birefringent crystal, rotated 45° clockwise through the Faraday rotator crystal, deflected to the left when passing through the roof prism, and then pass through the half-wave plate assembly. The sub-beam on the left is rotated 45° counterclockwise and converted into o light, and the sub-beam below is rotated 135° clockwise and is still e light. The o light and the e light are combined in the first birefringent crystal and emitted into the third port.

2. The three-port reflective optical circulator based on birefringent crystal according to claim 1, characterized in that: The first port, the second port and the third port are located in the same horizontal plane.

3. The three-port reflective optical circulator based on birefringent crystal according to claim 1, characterized in that: The second port is located between the first port and the third port.

4. The three-port reflective optical circulator based on birefringent crystal according to claim 1, characterized in that: The half-wave plate assembly comprises two half-wave plates, and the two half-wave plates are arranged on the left and right.

5. The three-port reflective optical circulator based on birefringent crystal according to claim 1, characterized in that: The first birefringent crystal has a tilt angle.

6. The three-port reflective optical circulator based on birefringent crystal according to claim 5, characterized in that: The cross section of the first birefringent crystal along the optical path is a parallelogram.

7. The three-port reflective optical circulator based on birefringent crystal according to claim 6, characterized in that: The side surface of the first birefringent crystal facing the first port is tilted rightward.

8. The three-port reflective optical circulator based on birefringent crystal according to claim 1, characterized in that: The three-port reflective optical circulator based on birefringent crystal further comprises a three-fiber collimator, and the three-fiber collimator is located on a side of the first birefringent crystal away from the half-wave plate assembly.

9. The three-port reflective optical circulator based on birefringent crystal according to claim 8, characterized in that: The three-fiber collimator forms the first port, the second port, and the third port.

10. The three-port reflective optical circulator based on birefringent crystal according to claim 8, characterized in that: The three-fiber collimator is located between the first port, the second port, the third port and the first birefringent crystal.

11. The three-port reflective optical circulator based on birefringent crystal according to claim 1, characterized in that: The three-port reflective optical circulator based on birefringent crystal further comprises an optical filter, which is located between the roof prism and the reflector.

12. The three-port reflective optical circulator based on birefringent crystal according to claim 11, characterized in that: The optical filter is located between the 1 / 4 wave plate and the reflecting mirror or the optical filter is located between the second birefringent crystal and the 1 / 4 wave plate.

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