Optical circulator

Abstract

The application relates to the technical field of optical communication, in particular to an optical circulator; the optical circulator comprises a collimating lens, a birefringent crystal, a half-wave plate assembly, a rotatory polarizer, a prism assembly and a PD detector, the half-wave plate assembly comprises a first half-wave plate, a second half-wave plate, a third half-wave plate and a fourth half-wave plate, the prism assembly comprises a first reflecting surface and a second reflecting surface, and the prism assembly is coated with a light splitting film and a polarization beam splitting film; the optical circulator realizes real-time monitoring of the input optical power state by converting the optical path through the prism assembly, coupling part of the incident light beam to the PD detector by using the light splitting film, and greatly simplifying the overall optical path structure without additionally adding an independent light splitting and light taking device; the first half-wave plate, the second half-wave plate, the third half-wave plate, the fourth half-wave plate and the rotatory polarizer are matched to realize accurate regulation and control of the polarization state, and to block the polarization state of the reversely transmitted light beam, effectively improve the isolation degree of the device, and make the overall structure compact and smaller in size, meeting the miniaturization requirement of the optical module.

Description

Technical Field

[0001] This invention relates to the field of optical communication technology, and in particular to an optical circulator. Background Technology

[0002] Optical circulators are core passive non-reciprocal devices in optical communication, widely used in coherent optical modules, fiber optic sensing, and optical path echo monitoring to achieve unidirectional beam transmission and suppress reverse optical path interference. Currently, mainstream three-port optical circulators typically consist of three sets of polarization-shifting crystals and two stages of optical rotators arranged along a straight optical path. Reverse isolation is usually optimized by adjusting the relative angle between the two optical rotators. In applications requiring real-time monitoring of optical power, this straight optical path cannot be used to embed a beam splitting and sampling structure within the device, thus preventing the integration of power detection functionality. It necessitates the use of an external PD beam splitter for discrete series assembly. The stacking of multiple devices results in a large overall size, multi-stage optical path coupling introduces additional insertion loss, and the secondary assembly process is cumbersome and costly, making it difficult to meet the development needs of miniaturized and high-density integrated optical modules.

[0003] Therefore, designing an optical circulator that integrates optical ring transmission and power detection is of great importance to those skilled in the art. Summary of the Invention

[0004] This invention provides an optical circulator that integrates optical ring transmission and power detection, in order to solve the problem that existing straight optical paths cannot embed a beam splitting and sampling structure within the device and cannot simultaneously achieve ring transmission and power detection.

[0005] This invention discloses an optical circulator, which includes: a collimating lens, a birefringent crystal, a half-wave plate assembly, a rotator, a prism assembly, and a PD detector. The half-wave plate assembly includes a first half-wave plate, a second half-wave plate, a third half-wave plate, and a fourth half-wave plate. The prism assembly includes a first reflecting surface and a second reflecting surface. The prism assembly is coated with a beam-splitting film and a polarizing beam-splitting film.

[0006] The light beam incident through the first optical fiber passes sequentially through the collimating lens and the birefringent crystal and is split into o-beams and e-beams. The e-beams are incident on the beam-splitting film of the prism assembly. The o-beams are converted into e-beams by the first half-wave plate and then incident on the beam-splitting film of the prism assembly for beam splitting. Both e-beams transmitted through the beam-splitting film are incident on the PD detector for optical power monitoring. The two reflected e-beams are reflected back to the optical rotator by the polarization beam-splitting film. One e-beam is deflected sequentially by the optical rotator and the second half-wave plate and then incident on the birefringent crystal. The other e-beam is deflected sequentially by the optical rotator and the fourth half-wave plate and then converted into o-beams and incident on the birefringent crystal. The o-beams and e-beams incident on the birefringent crystal are combined by the birefringent crystal and then incident on the collimating lens, and then converged by the collimating lens to output through the second optical fiber. The light incident through the second optical fiber passes sequentially through the collimating lens and the birefringent crystal, splitting into o-beams and e-beams. The o-beam passes through the fourth half-wave plate and the optical rotator before entering the prism assembly. The e-beam is converted back into o-beams by the second half-wave plate and the optical rotator before entering the prism assembly. Both o-beams incident on the prism assembly are transmitted through the polarizing beam splitter to the first reflecting surface. One o-beam is reflected sequentially by the first and second reflecting surfaces before entering the birefringent crystal, and the other o-beam is reflected sequentially by the first and second reflecting surfaces before entering the third half-wave plate. It is then converted back into e-beams by the third half-wave plate before entering the birefringent crystal. The o-beams and e-beams incident on the birefringent crystal are combined by the birefringent crystal and then enter the collimating lens, which converges them to output through the third optical fiber.

[0007] Optionally, the optical axis angles of the first half-wave plate and the third half-wave plate are the same.

[0008] Optionally, the optical axis angles of the second half-wave plate and the fourth half-wave plate are opposites of each other.

[0009] Optionally, the polarization rotation angle of the optical rotator is 45°.

[0010] Optionally, the optical axis angles of both the first half-wave plate and the third half-wave plate are 45°.

[0011] Optionally, the optical axis angle of the second half-wave plate is 22.5°, and the optical axis angle of the fourth half-wave plate is -22.5°.

[0012] Optionally, the prism assembly is an integrated optical prism.

[0013] Optionally, the beam splitter and the polarizing beam splitter are arranged at a 90-degree angle.

[0014] Optionally, the first reflecting surface and the second reflecting surface are two mutually perpendicular inner reflecting end faces in the prism assembly, and the first reflecting surface is perpendicular to the polarization beam splitter film, while the second reflecting surface is parallel to the polarization beam splitter film.

[0015] Optionally, the optical rotator is disposed between the second half-wave plate, the fourth half-wave plate and the prism assembly. The light beams emitted from the second half-wave plate and the fourth half-wave plate are both incident on the prism assembly via the optical rotator, and the light beams emitted from the prism assembly are incident on the second half-wave plate or the fourth half-wave plate via the optical rotator.

[0016] The beneficial effects of the optical circulator provided in this embodiment of the invention are as follows: By integrating a beam splitter, a polarization beam splitter, and a built-in first and second reflecting surface into the prism assembly, while realizing the core function of unidirectional light guiding from the first fiber to the second fiber and from the second fiber to the third fiber, the beam splitter partially splits and couples the incident beam to the PD detector, achieving real-time monitoring of the input optical power state. This eliminates the need for additional independent beam splitting and light-collecting devices, significantly simplifying the overall optical path structure and reducing the number of optical components and assembly tolerances. Furthermore, by setting the first half-wave plate, the second half-wave plate, the third half-wave plate, and the fourth half-wave plate in conjunction with the optical rotator, precise control of the polarization state is ensured, and polarization state blocking of the reverse-propagating beam is achieved, effectively improving the device isolation. The overall structure is compact and smaller in size, meeting the miniaturization requirements of optical modules. Attached Figure Description

[0017] The technical solution of the present invention will be further described in detail below with reference to the accompanying drawings and embodiments. In the accompanying drawings: Figure 1 This is a schematic diagram of the structure of the optical circulator in an embodiment of the present invention; Figure 2 This is a top view of the optical path of the optical circulator in an embodiment of the present invention; Figure 3 This is a side view of the optical path of the optical circulator in an embodiment of the present invention. Figure 1 ; Figure 4 This is a side view of the optical path of the optical circulator in an embodiment of the present invention. Figure 2 ; Figure 5 This is a side view of the optical path of the optical circulator in an embodiment of the present invention. Figure 3 .

[0018] The labels for the attached figures are as follows: 1. Collimating lens; 2. Birefringent crystal; 5. Optical rotator; 6. Prism assembly; 7. PD detector; 31. First half-wave plate; 32. Second half-wave plate; 33. Third half-wave plate; 34. Fourth half-wave plate; 61. First reflecting surface; 62. Second reflecting surface; 63. Beam splitter; 64. Polarizing beam splitter. Detailed Implementation

[0019] It should be noted that, unless otherwise specified, the embodiments and features described in this application can be combined with each other. The preferred embodiments of the present invention will now be described in detail with reference to the accompanying drawings.

[0020] like Figures 1 to 5 As shown, the present invention provides a specific embodiment of an optical circulator.

[0021] An optical circulator, reference Figures 1 to 5 The optical circulator includes a collimating lens 1, a birefringent crystal 2, a half-wave plate assembly, a rotator 5, a prism assembly 6, and a PD detector 7. The half-wave plate assembly includes a first half-wave plate 31, a second half-wave plate 32, a third half-wave plate 33, and a fourth half-wave plate 34. The prism assembly 6 includes a first reflecting surface 61 and a second reflecting surface 62. The prism assembly 6 is coated with a beam splitting film 63 and a polarizing beam splitting film 64.

[0022] Specifically, the optical circulator is a three-port optical circulator with integrated real-time input optical power monitoring function. The three ports are respectively connected to the first optical fiber, the second optical fiber, and the third optical fiber. The first optical fiber, the second optical fiber, and the third optical fiber are all fixed on one side of the collimating lens 1. The first optical fiber is the signal input port of the optical circulator, used to transmit external optical signals into the optical circulator. The second optical fiber is the output port of the first optical fiber signal, used to receive the optical signals transmitted unidirectionally from the first optical fiber, realizing forward conduction from the first port to the second port of the optical circulator. The third optical fiber is the secondary output port, used to receive the optical signals transmitted unidirectionally from the second optical fiber, realizing secondary forward conduction from the second port to the third port of the optical circulator. The first optical fiber, the second optical fiber, and the third optical fiber together constitute the external optical path interface of the optical circulator.

[0023] The collimating lens 1 serves two purposes: firstly, it shapes the diverging beam emitted from the first or second fiber into a collimated parallel beam, ensuring that the parallel beam is incident perpendicularly onto the subsequent birefringent crystal 2. This avoids problems such as polarization splitting failure and film incident angle shift caused by beam divergence, thereby improving the accuracy of polarization control and optical path splitting. Secondly, it can converge and focus the reverse parallel beam after it has been bundled by the birefringent crystal 2, accurately coupling and focusing the parallel beam into the core of the second or third fiber. This reduces the optical power insertion loss during fiber coupling and simultaneously unifies the convergence of multiple discrete polarized beams, ensuring the optical path transmission efficiency and optical performance stability of the entire circulator.

[0024] The birefringent crystal 2 is positioned on the other side of the collimating lens 1. On one hand, it receives the parallel incident beam output from the collimating lens 1 and, utilizing its own birefringence effect, decomposes the incident single-beam parallel light into o-beams and e-beams, which are orthogonally polarized and spatially separated vertically. This provides two independent physical optical paths for the subsequent directional polarization conversion and polarization sorting of the half-wave plate assembly, the optical rotator 5, and the prism assembly 6. On the other hand, during the reverse transmission of the beam, it can re-couple the o-beams and e-beams that have been polarized and adjusted by the downstream optical devices into a single parallel collimated beam, which is then focused and coupled by the collimating lens 1 to the corresponding optical fiber output. Based on the core characteristics of the orthogonal polarization of the o-beams and e-beams being separable and recombineable, the basic optical conditions for the unidirectional transmission of this optical circulator are constructed.

[0025] The half-wave plate assembly is disposed on the side of the birefringent crystal 2 away from the collimating lens 1. The half-wave plate assembly includes a first half-wave plate 31, a second half-wave plate 32, a third half-wave plate 33, and a fourth half-wave plate 34. The first half-wave plate 31 is disposed on the beam propagation path corresponding to the first optical fiber. The second half-wave plate 32 and the fourth half-wave plate 34 are disposed vertically and together on the beam propagation path corresponding to the second optical fiber. The third half-wave plate 33 is disposed on the beam propagation path corresponding to the third optical fiber. The optical axis angle of the first half-wave plate 31 is 45°. The first half-wave plate 31 can flip the polarization state of the o-light split by the birefringent crystal 2 by 90° to convert the o-light into e-light, so that the polarization of the converted e-light is unified with that of the original e-light output by the birefringent crystal 2, and they are both incident on the beam splitting film 63 of the prism assembly 6.

[0026] The second half-wave plate 32 has an optical axis angle of 22.5°, and the fourth half-wave plate 34 has an optical axis angle of -22.5°. Both are located along the beam propagation path corresponding to the second optical fiber and are arranged vertically, forming a symmetrical polarization compensation pairing structure with opposite optical axis angles. In the return reflection optical path from the first fiber to the second fiber, the upper-path e-beam returned by the prism assembly 6 will pass through the second half-wave plate 32, and the lower-path e-beam will pass through the fourth half-wave plate 34. Polarization compensation is completed by cooperating with the 545° polarization rotation angle of the optical rotator. The upper-path e-beam can pass through the second half-wave plate... 32 cancels the optical rotation deflection to restore the polarization state. The lower e-beam is rotated by 45° after being superimposed on the fourth half-wave plate 34 to achieve a 90° polarization reversal, converting the e-beam into the o-beam. The two beams return to the birefringent crystal 2 with orthogonal polarization states to complete the beam combining. In the forward optical path from the second fiber to the third fiber, the e-beam split by the birefringent crystal 2 will pass through the second half-wave plate 32 and the o-beam will pass through the fourth half-wave plate 34 to complete the pre-polarization pre-adjustment. With the 545° polarization rotation angle of the optical rotator, it is ensured that all the beams entering the prism assembly 6 are o-beams.

[0027] The third half-wave plate 33 also has an optical axis angle of 45° and is independently set on the beam propagation path corresponding to the third optical fiber. The lower o-beam output by the prism assembly 6 after two internal reflections will undergo a 90° polarization reversal after passing through the third half-wave plate 33, changing from o-beam to e-beam. It will then form an orthogonal polarization beam pair with the upper o-beam restored by the second half-wave plate 32. Together, they are coupled and bundled inside the birefringent crystal 2, and then focused and coupled into the third optical fiber output through the collimating lens 1. The half-wave plate assembly is precisely arranged based on the optical path partitions corresponding to the three optical fibers, and performs the directional polarization conversion of o-beam and e-beam under different transmission directions at the three ports. Relying on the symmetrical angle compensation structure to reduce polarization loss, it provides a precise and reliable polarization control basis for the entire optical circulator to achieve unidirectional transmission from the first optical fiber to the second optical fiber and from the second optical fiber to the third optical fiber.

[0028] The prism assembly 6 is an integral optical prism formed from a single substrate and featuring an L-shaped right-angle bend. It is positioned on the side of the rotator plate 5 away from the half-wave plate assembly. The prism assembly 6 has a beam-splitting film 63 deposited on the side facing the rotator plate 5 inside. A polarizing beam-splitting film 64 is also obliquely sandwiched inside the cavity of the prism assembly 6. The plane of the beam-splitting film 63 and the plane of the polarizing beam-splitting film 64 are arranged at a 90° angle. The tail of the prism assembly 6 has two mutually perpendicular total internal reflection inner end faces, namely the first reflection surface 61 and the second reflection surface 62. The first reflection surface 61 is perpendicular to the polarizing beam-splitting film 64, and the second reflection surface 62 is parallel to the polarizing beam-splitting film 64.

[0029] The prism assembly 6 integrates multiple optical functions. Through the beam splitter 63, it can split the energy of the two incident e-beams. The transmitted beam of the preset ratio is directly output to the PD detector 7, realizing real-time online monitoring of the input optical power of the first fiber. Power sampling can be completed without the need for additional independent beam splitting devices. The remaining reflected beam is incident on the internal polarization beam splitter 64. Relying on the polarization sorting characteristics of the polarization beam splitter 64, the incident e-beam is totally reflected and refracted back to the direction of the optical rotator 5. The incident o-beam is totally transmitted and enters the first reflecting surface 61, so as to physically isolate the optical path of the two transmission paths from the first fiber to the second fiber and from the second fiber to the third fiber, providing a structural basis for the unidirectional transmission of the device. The o-beam transmitted through the polarization beam splitter 64 can undergo two total reflections in sequence at the first reflecting surface 61 and the second reflecting surface 62 to complete the U-shaped refracting of the optical path, so that the beam is output in reverse to the optical rotator 5 and the half-wave plate assembly for secondary polarization control.

[0030] The use of an integrated, one-piece molded prism structure eliminates the gaps in the assembly of multiple discrete prisms, significantly reduces the refractive interface between the glass and air, lowers insertion loss, and constrains reverse stray light through an internally closed reflective optical path. The stray light can be dissipated through multiple reflections between the first reflective surface 61 and the second reflective surface 62, effectively preventing backflow of optical signals and significantly improving the reverse isolation and optical stability of the optical circulator.

[0031] The photosensitive surface of the PD detector 7 faces the direction of transmitted light emission from the beam splitter 63 of the prism assembly 6, and is used to receive part of the incident beam coupled and split by the beam splitter 63. During the forward transmission from the first fiber to the second fiber, the beam splitter 63 of the prism assembly 6 splits part of the energy of the beam directly into the PD detector 7 according to the preset beam splitting ratio. The PD detector 7 can convert the received optical signal into the corresponding electrical signal in real time, thereby realizing online real-time monitoring and sampling feedback of the input optical power at the port of the first fiber. This structure relies on the beam splitter 63 of the prism assembly 6 to complete the light extraction, without the need to add additional independent beam splitters, couplers and other external devices, simplifying the overall optical path structure, reducing the insertion loss introduced by the redundant optical interface, and the monitoring optical path will not interfere with the main transmission optical path from the first fiber to the second fiber and from the second fiber to the third fiber, ensuring that the unidirectional transmission performance of the optical circulator is not affected by the power monitoring function.

[0032] refer to Figures 1 to 5The transmission optical path from the first optical fiber to the second optical fiber is as follows: The diverging beam output from the first optical fiber first enters the collimating lens 1, and after being shaped into a parallel collimated beam by the collimating lens 1, it enters the birefringent crystal 2 perpendicularly. The birefringent crystal 2 splits the incident single parallel beam into spatially separated and orthogonally polarized e-beams and o-beams. The upper e-beam propagates directly forward, while the lower o-beam passes through the first half-wave plate 31 in the half-wave plate assembly. The first half-wave plate 31 flips the polarization state of the lower o-beam by 90° to convert it into the lower e-beam, so that the polarization state of the converted lower e-beam is consistent with that of the original upper e-beam. Both e-beams enter the beam splitter 63 of the prism assembly 6 together. The beam splitter 63 splits the two incident e-beams according to a preset ratio. The transmitted beam enters the PD detector 7, which converts the optical signal into an electrical signal to realize real-time monitoring of the input optical power of the first optical fiber. The reflected beam enters the prism assembly 6. The polarization beam splitter 64 in the part performs total internal reflection on the two e-beams, causing them to be reflected back in opposite directions. The upper e-beam passes through the optical rotator 5 and the second half-wave plate 32 in sequence. The 45° polarization deflection corresponding to the 22.5° optical axis of the second half-wave plate 32 cancels the 45° polarization rotation of the optical rotator 5, thus maintaining the e-beam output. The lower e-beam passes through the optical rotator 5 and the fourth half-wave plate 34 in sequence. The -45° polarization deflection corresponding to the -22.5° optical axis of the fourth half-wave plate 34, combined with the 45° polarization rotation of the optical rotator 5, forms a 90° polarization reversal, thus converting the e-beam into an o-beam. The upper e-beam with unchanged polarization state and the lower o-beam with converted polarization state are both incident in opposite directions onto the birefringent crystal 2. The birefringent crystal 2 completes the beam combining of the two orthogonally polarized beams. The combined parallel beam is focused and coupled by the collimating lens 1 and accurately guided into the second optical fiber, thus completing the unidirectional light transmission process from the first optical fiber to the second optical fiber.

[0033] refer to Figures 1 to 5The transmission optical path from the second fiber to the third fiber is as follows: The diverging beam output from the second fiber is shaped into a parallel beam by the collimating lens 1 and then incident on the birefringent crystal 2. The birefringent crystal 2 splits the beam into spatially separated and orthogonally polarized e-beams and o-beams. The upper e-beam enters the second half-wave plate 32 in the half-wave plate assembly, and the lower o-beam enters the fourth half-wave plate 34 in the half-wave plate assembly to complete the pre-polarization compensation. The two compensated beams pass through the optical rotator 5 and undergo a 45° polarization rotation. After being normalized into a unified o-beam polarization state, they are incident on the polarization beam splitter 64 of the prism assembly 6. The polarization beam splitter 64 transmits the two o-beams through the prism assembly 6. The light is incident on the first reflecting surface 61. After two total internal reflections by the first reflecting surface 61 and the second reflecting surface 62, the two o-beams are reflected back. The upper o-beam reflected back will be incident on the third half-wave plate 33 in the half-wave plate assembly. The third half-wave plate 33 will flip the polarization of the upper o-beam reflected back by 90° to convert it into an upper e-beam, which will then be incident on the birefringent crystal 2. The lower o-beam reflected back will be directly incident on the birefringent crystal 2. The upper e-beam and the lower o-beam are combined into a parallel beam by the birefringent crystal 2 and then accurately transmitted to the third optical fiber after being focused and coupled by the collimating lens 1, thus completing the unidirectional light transmission process from the second optical fiber to the third optical fiber.

[0034] This optical circulator relies on a polarization adjustment structure composed of a polarizer 5, a first half-wave plate 31, a second half-wave plate 32, a third half-wave plate 33, and a fourth half-wave plate 34 to achieve strictly unidirectional transmission. When the beam attempts to flow back from the second fiber to the first fiber or from the third fiber to the second fiber, the polarization control state of the reverse-transmitted beam cannot match the beam combining condition of the birefringent crystal 2. The two polarized beams are always in a spatially separated state and cannot be effectively combined, and cannot be coupled into the front fiber port by the collimating lens 1. At the same time, the first reflecting surface 61 and the second reflecting surface 62 inside the prism assembly 6 can perform multiple reflections to dissipate the reverse stray light, completely suppressing optical signal crosstalk and reverse flow between ports, effectively ensuring the reverse isolation performance of the device. Combined with the integrated structure of the integrated prism, the optical interface is greatly reduced, the transmission insertion loss is reduced, and stable and efficient unidirectional non-reciprocal optical transmission is achieved.

[0035] It should be understood that the above embodiments are only used to illustrate the technical solutions of the present invention, and are not intended to limit them. Those skilled in the art can modify the technical solutions described in the above embodiments, or make equivalent substitutions for some of the technical features; and all such modifications and substitutions should fall within the protection scope of the appended claims of the present invention.

Claims

1. An optical circulator, characterized in that, include: The collimating lens, birefringent crystal, half-wave plate assembly, optical rotator, prism assembly, and PD detector are provided. The half-wave plate assembly includes a first half-wave plate, a second half-wave plate, a third half-wave plate, and a fourth half-wave plate. The prism assembly includes a first reflecting surface and a second reflecting surface. The prism assembly is coated with a beam-splitting film and a polarizing beam-splitting film. The light beam incident through the first optical fiber passes sequentially through the collimating lens and the birefringent crystal and is split into o-beams and e-beams. The e-beams are incident on the beam-splitting film of the prism assembly. The o-beams are converted into e-beams by the first half-wave plate and then incident on the beam-splitting film of the prism assembly for beam splitting. Both e-beams transmitted through the beam-splitting film are incident on the PD detector for optical power monitoring. The two reflected e-beams are reflected back to the optical rotator by the polarization beam-splitting film. One e-beam is deflected sequentially by the optical rotator and the second half-wave plate and then incident on the birefringent crystal. The other e-beam is deflected sequentially by the optical rotator and the fourth half-wave plate and then converted into o-beams and incident on the birefringent crystal. The o-beams and e-beams incident on the birefringent crystal are combined by the birefringent crystal and then incident on the collimating lens, and then converged by the collimating lens to output through the second optical fiber. The light incident through the second optical fiber passes sequentially through the collimating lens and the birefringent crystal, splitting into o-beams and e-beams. The o-beam passes through the fourth half-wave plate and the optical rotator before entering the prism assembly. The e-beam is converted back into o-beams by the second half-wave plate and the optical rotator before entering the prism assembly. Both o-beams incident on the prism assembly are transmitted through the polarizing beam splitter to the first reflecting surface. One o-beam is reflected sequentially by the first and second reflecting surfaces before entering the birefringent crystal, and the other o-beam is reflected sequentially by the first and second reflecting surfaces before entering the third half-wave plate. It is then converted back into e-beams by the third half-wave plate before entering the birefringent crystal. The o-beams and e-beams incident on the birefringent crystal are combined by the birefringent crystal and then enter the collimating lens, which converges them to output through the third optical fiber.

2. The optical circulator according to claim 1, characterized in that, The optical axis angles of the first half-wave plate and the third half-wave plate are the same.

3. The optical circulator according to claim 1, characterized in that, The optical axis angles of the second half-wave plate and the fourth half-wave plate are opposites of each other.

4. The optical circulator according to claim 1, characterized in that, The polarization rotation angle of the optical rotator is 45°.

5. The optical circulator according to claim 4, characterized in that, The optical axis angles of the first half-wave plate and the third half-wave plate are both 45°.

6. The optical circulator according to claim 4, characterized in that, The optical axis angle of the second half-wave plate is 22.5°, and the optical axis angle of the fourth half-wave plate is -22.5°.

7. The optical circulator according to claim 1, characterized in that, The prism assembly is an integrated optical prism.

8. The optical circulator according to claim 1, characterized in that, The beam splitter and the polarizing beam splitter are set at a 90-degree angle.

9. The optical circulator according to claim 8, characterized in that, The first reflecting surface and the second reflecting surface are two mutually perpendicular internal reflecting end surfaces in the prism assembly, and the first reflecting surface is perpendicular to the polarization beam splitter film, while the second reflecting surface is parallel to the polarization beam splitter film.

10. The optical circulator according to claim 1, characterized in that, The optical rotator is disposed between the second half-wave plate, the fourth half-wave plate and the prism assembly. The light beams emitted from the second half-wave plate and the fourth half-wave plate are both incident on the prism assembly via the optical rotator, and the light beams emitted from the prism assembly are incident on the second half-wave plate or the fourth half-wave plate via the optical rotator.

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