Miniaturized Wavelength Division Multiplexer

Abstract

The present invention provides a miniaturized wavelength division multiplexer, which includes a light combining component and an isolation component; the light combining component has a glass sheet and a reflective device, the glass sheet has a first light passing surface and a second light passing surface that are parallel to each other, the reflective device is arranged on one side of the glass sheet, and the reflective surface of the reflective device is parallel to the second light passing surface; the isolation component is located at the output end of the light combining component, and the isolation component includes a first birefringent crystal, a rotating device, and a second birefringent crystal arranged in sequence along the optical path. The first incident surface of the first birefringent crystal is parallel to the second output surface of the second birefringent crystal, and the optical axis of the first birefringent crystal forms an angle of 45° with the optical axis of the second birefringent crystal. The miniaturized wavelength division multiplexer of the present invention has a simple structure, low production cost, and good isolation effect on the backward incident return light.

Description

Technical Field

[0001] The present invention relates to the technical field of optical communication devices, and specifically, to a miniaturized wavelength division multiplexer with an optical isolation function. Background Art

[0002] A wavelength division multiplexer is a common optical device that can combine or split light beams according to wavelengths and is often used in optical fiber communication networks. Common wavelength division multiplexers include grating-based wavelength division multiplexers that split light beams according to wavelengths through the grating diffraction principle, and another type of wavelength division multiplexer splits light beams by setting filter films.

[0003] The Chinese patent application with the publication number CN110441864A discloses an optical wavelength division multiplexer that sets multiple polarization beam combining structures, a polarizer, and multiple half-wave plates to combine multiple incident light beams with different wavelengths and transmits the combined light beam through a common optical fiber.

[0004] However, on the one hand, the existing wavelength division multiplexer has a complex structure. In particular, a large number of polarization beam combining structures need to be set, and a polarizer and multiple half-wave plates also need to be set to adjust the polarization state of the light beam, increasing the volume of the wavelength division multiplexer and resulting in a high production cost of the wavelength division multiplexer. On the other hand, the existing wavelength division multiplexer often does not have an optical isolation function, that is, it cannot avoid the interference of reverse return light on the incident light beam, affecting the performance of the wavelength division multiplexer.

[0005] In addition, the existing wavelength division multiplexer for realizing the light splitting function needs to use a large number of filter films, resulting in a high production cost and a large volume of this wavelength division multiplexer, which does not meet the requirement of miniaturization of the wavelength division multiplexer. Summary of the Invention

[0006] The object of the present invention is to provide a miniaturized wavelength division multiplexer with a simple structure, easy assembly, and an isolation function.

[0007] To achieve the above object, the miniaturized wavelength division multiplexer provided by the present invention is composed of a light combining component and an isolation component; the light combining component is composed of a glass sheet and a reflective device. The glass sheet has a first light passing surface and a second light passing surface that are parallel to each other. The reflective device is arranged on one side of the glass sheet, and the reflective surface of the reflective device is parallel to the second light passing surface. The light beam of the first wavelength is incident from the first light passing surface and exits from the second light passing surface. The light beam of the second wavelength is incident from the reflective device and, after passing through the reflective surface, is incident on the second light passing surface. The light beam of the first wavelength and the light beam of the second wavelength are combined at the second light passing surface; the isolation component is located at the output end of the light combining component and is composed of a first birefringent crystal, a rotating device, and a second birefringent crystal arranged in sequence along the optical path. The first incident surface of the first birefringent crystal is parallel to the second output surface of the second birefringent crystal, and the optical axis of the first birefringent crystal forms an angle of 45° with the optical axis of the second birefringent crystal; the light beam exiting from the second birefringent crystal realizes a lateral offset according to the polarization state.

[0008] As can be seen from the above solution, two light beams of different wavelengths are respectively incident on the glass sheet and the reflective device, and are combined at the second light passing surface of the glass sheet. The combined light beam is split and the polarization state is converted according to different wavelengths and polarization states after passing through the first birefringent crystal, the rotating device, and the second birefringent crystal, thereby realizing the function of optical isolation. The light beam is finally output to the output collimator, realizing the function of wavelength division multiplexing.

[0009] Since the optical axis of the first birefringent crystal forms an angle of 45° with the optical axis of the second birefringent crystal, the backward incident return light cannot be combined after passing through the first birefringent crystal, so it cannot return to the glass sheet or the reflective device along the original path, thereby avoiding the interference of the returned light on the incident light beam and improving the performance of the wavelength division multiplexer.

[0010] Moreover, since the light beam incident on the isolation component contains two different wavelengths, and each wavelength of the light beam will be decomposed into ordinary light and extraordinary light, the present invention utilizes the characteristic that the ordinary light and extraordinary light of different wavelengths have different refractive indices in the birefringent crystal, so that four different light beams can be separated after passing through the isolation component. Therefore, the present invention can combine the light beam with the first wavelength and the light beam with the second wavelength, and realize the lateral offset of the combined light beam according to the wavelength and polarization state through the isolation component, thereby realizing the function of splitting light according to the wavelength and polarization state. Therefore, the present invention is not a simple light combining or light splitting device, but a wavelength division multiplexing device that first combines light and then splits light.

[0011] In addition, since the wavelength division multiplexer only sets a glass sheet, a reflective device, two birefringent crystals, and a rotating device, and does not need to set devices such as a half-wave plate, a polarizer, and a filter, and the devices in the wavelength division multiplexer of the present invention are compactly arranged, the structure of the wavelength division multiplexer is miniaturized and its production cost is reduced.

[0012] A preferred solution is that the reflective device is a rhombic prism, the first inclined surface of the rhombic prism is the reflective surface, and the second inclined surface opposite to the first inclined surface is closely attached to the second light-transmitting surface.

[0013] It can be seen that by setting the rhombic prism and making one inclined surface of the rhombic prism closely attached to the second light-transmitting surface of the glass sheet, the rhombic prism and the glass sheet can be closely attached, thereby reducing the volume of the light combining component.

[0014] An optional solution is that the reflective device is a right-angled prism.

[0015] A further solution is that the shape of the first birefringent crystal is exactly the same as that of the second birefringent crystal. Further, the first birefringent crystal and the second birefringent crystal are symmetrically arranged on both sides of the rotating device with the axis of the miniaturized wavelength division multiplexer as the center.

[0016] Since the first birefringent crystal and the second birefringent crystal are exactly the same and symmetrically arranged, only one type of birefringent crystal needs to be prepared to meet the production of the wavelength division multiplexer. And because the first birefringent crystal and the second birefringent crystal are symmetrically arranged, the assembly process of the wavelength division multiplexer is simple, and the production cost of the wavelength division multiplexer can be reduced.

[0017] A further solution is that the rotating device includes a Faraday rotator, and a magnet is arranged outside the Faraday rotator.

[0018] It can be seen that by applying a sufficient magnetic field from the magnet to the Faraday rotator, the optical path deflects when the light beam passes through the Faraday rotator, thereby realizing the separation of the light beam.

[0019] A further solution is that the light combining component and the isolation component are encapsulated in a sleeve. In this way, the light combining component and the isolation component can be compactly encapsulated, which is beneficial to the miniaturization of the wavelength division multiplexer.

[0020] A further solution is that the first incident surface of the first birefringent crystal is inclined with respect to the axis of the sleeve.

[0021] A further solution is that the first exit surface of the first birefringent crystal is parallel to the second incident surface of the second birefringent crystal, and the rotating device is clamped between the first exit surface of the first birefringent crystal and the second incident surface of the second birefringent crystal.

[0022] A further solution is that the first exit surface of the first birefringent crystal is perpendicular to the axis of the sleeve.

[0023] With the above structure, the first birefringent crystal, the second birefringent crystal and the rotating device can be compactly packaged in the sleeve, and the internal devices of the wavelength division multiplexer are arranged very compactly, which is beneficial to the miniaturization of the wavelength division multiplexer. Description of the Drawings

[0024] Figure 1 It is a structural diagram of the first embodiment of the present invention.

[0025] Figure 2 It is a structural diagram of the first birefringent crystal, the rotating device and the second birefringent crystal in the first embodiment of the present invention.

[0026] Figure 3 It is a forward optical path diagram of the first embodiment of the present invention.

[0027] Figure 4 It is a reverse optical path diagram of the first embodiment of the present invention.

[0028] Figure 5 It is a structural diagram of the second embodiment of the present invention.

[0029] The present invention will be further described below in conjunction with the drawings and embodiments. Detailed Embodiments

[0030] The miniaturized wavelength division multiplexer of the present invention is applied in an optical fiber communication network to combine light beams of different wavelengths. Moreover, all the optical devices of the miniaturized wavelength division multiplexer of the present invention are packaged in a sleeve, making the structure of the wavelength division multiplexer very compact and meeting the requirements of the miniaturization of the wavelength division multiplexer. In addition, the miniaturized wavelength division multiplexer of the present invention also has an optical isolation function, which can avoid the return light from being incident on the light combining component and improve the performance of the wavelength division multiplexer.

[0031] First Embodiment:

[0032] Refer to Figure 1 , the miniaturized wavelength division multiplexer of this embodiment is composed of a light combining component 20 and an isolation component 30. The light combining component 20 and the isolation component 30 are packaged in a sleeve 10. The light combining component 20 is composed of a glass sheet 21 and a reflecting device. The reflecting device in this embodiment is a rhombic prism 25. The glass sheet 21 has a first light passing surface 22 and a second light passing surface 23. The first light passing surface 22 is the surface where the light beam is incident, and the second light passing surface 23 is the surface where the light beam exits. The first light passing surface 22 and the second light passing surface 23 are arranged parallel to each other. As can be seen from Figure 1 , the glass sheet 21 is inclined in the sleeve 10, that is, the first light passing surface 22 of the glass sheet 21 is inclined with respect to the axis of the sleeve 10.

[0033] The rhombic prism 25 is arranged on one side of the glass sheet 21. Specifically, it is located on one side of the second light-transmitting surface 23. The rhombic prism 25 has a first inclined surface 26 and a second inclined surface 27. The first inclined surface 26 and the second inclined surface 27 are arranged in parallel with each other. The first inclined surface 26 is a reflective surface and can reflect the light beam to the second inclined surface 27. From Figure 1 It can be seen that the second inclined surface 27 is closely attached to the second light-transmitting surface 23 of the glass sheet 21.

[0034] Moreover, the light-combining component 20 is encapsulated in the sleeve 10. Preferably, the outer diameter of the light-combining component 20 is equal to the inner diameter of the sleeve 10, and the light-combining component 20 is prevented from moving axially or radially within the sleeve 10.

[0035] The isolation component 30 is arranged on the light-emitting side of the light-combining device 20 and is composed of a first birefringent crystal 31, a rotating device, and a second birefringent crystal 36 in sequence according to the optical path. Among them, the rotating device in this embodiment includes a Faraday rotator 34. See Figure 2 , both the first birefringent crystal 31 and the second birefringent crystal 36 are wedge-shaped. The first birefringent crystal 31 has a first incident surface 32 and a first exit surface 33. The second birefringent crystal 36 has a second incident surface 37 and a second exit surface 38. The Faraday rotator 34 is clamped between the first birefringent crystal 31 and the second birefringent crystal 36.

[0036] The structures of the first birefringent crystal 31 and the second birefringent crystal 36 are exactly the same, and they are symmetrically arranged on both sides of the Faraday rotator 34 with the axis of the miniaturized wavelength division multiplexer as the center. In addition, the optical axes of the first birefringent crystal 31 and the second birefringent crystal 36 form an angle of 45°. Among them Figure 2 The arrows show the optical axes of the first birefringent crystal 31 and the second birefringent crystal 36.

[0037] A magnet 35 is arranged outside the Faraday rotator 34. The magnet 35 is a magnetic ring and is embedded in the inner wall of the sleeve 10. From Figure 1 It can be seen that the first birefringent crystal 31, the Faraday rotator 34, and the second birefringent crystal 36 are all located within the magnet 35. Preferably, the outer peripheries of the first birefringent crystal 31, the Faraday rotator 34, and the second birefringent crystal 36 abut against the inner wall of the magnet 35.

[0038] When assembling the light-combining component 20, two birefringent crystals with exactly the same shape can be prepared and used as the first birefringent crystal 31 and the second birefringent crystal 36 respectively. After fixing the first birefringent crystal 31 on the first side of the Faraday rotator 34, the other birefringent crystal is symmetrically flipped along the axis of the Faraday rotator 34 and placed as shown in Figure 2The state shown is such that another birefringent crystal is fixed as the second birefringent crystal 36 on the second side of the Faraday rotator 34. Optionally, the first birefringent crystal 31 is fixed on the first side of the Faraday rotator 34 by optical cement, and the second birefringent crystal 36 is fixed on the second side of the Faraday rotator 34 by optical cement.

[0039] The first incident surface 32 of the first birefringent crystal 31 is parallel to the second exit surface 38 of the second birefringent crystal 36, and the first exit surface 33 of the first birefringent crystal 31 is also parallel to the second incident surface 37 of the second birefringent crystal 36. Preferably, the first incident surface 32 of the first birefringent crystal 31 forms an angle with the axis of the sleeve 10, while the first exit surface 33 of the first birefringent crystal 31 is perpendicular to the axis of the sleeve 10.

[0040] See Figure 3 , the wavelength of the collimated beam L11 output from the first input collimator is λ1, the wavelength of the collimated beam L12 output from the second input collimator is λ2, the beams L11 and L12 are parallel to each other, the beam L11 is incident on the first light-passing surface 22 of the glass sheet 21, and refraction occurs within the glass sheet 21, and then exits from the second light-passing surface 23 and transmits along the optical path of the beam L14. Since the first light-passing surface 22 and the second light-passing surface 23 are parallel to each other, the beams L11 and L14 are parallel to each other.

[0041] The beam L12 is incident on the first inclined surface 26 of the rhombic prism 25, and reflection occurs on the first inclined surface 26 to form the beam L13. The beam L13 is incident on the second inclined surface 27 and reflects again, and transmits along the optical path of the beam L14. Therefore, by adjusting the incident positions of the beams L11 and L12, it is possible to make the beam after passing through the glass sheet 21 and the beam after reflection by the rhombic prism 25 be combined at the second light-passing surface 23 of the glass sheet 21, that is, the beam L14 is formed by the combination of the beams L11 and L12, so the beam L14 contains the beams with wavelengths λ1 and λ2.

[0042] After the beam L14 is incident on the first incident surface 32 of the first birefringent crystal 31, due to the birefringence effect of the first birefringent crystal 31, it is divided into two linearly polarized light beams with mutually perpendicular polarization states according to different wavelengths, that is, the ordinary light and the extraordinary light. Since the beam L14 contains two different wavelengths, and each wavelength is divided into ordinary light and extraordinary light, a total of four beams are formed, and a beam group L15 is formed within the first birefringent crystal 31.

[0043] The four beams of light passing through the first birefringent crystal 31 form a light beam group L16 when passing through the Faraday rotator 34. The polarization state of each beam of light in the light beam group L16 will be rotated by 45°. Specifically, taking the incident light direction as the observation reference, the polarization state of each beam of light is rotated counterclockwise by 45°. After the four beams of light with the rotated polarization state are transmitted to the second birefringent crystal 37, a light beam group L17 will be formed. Since the polarization states of the two beams of light with the same wavelength have been rotated, therefore, relative to the second birefringent crystal 37, there is no conversion between ordinary light and extraordinary light. And, since the first incident surface 32 of the first birefringent crystal 31 is parallel to the second exit surface 38 of the second birefringent crystal 36, the combination of the first birefringent crystal 31 and the second birefringent crystal 36 is equivalent to a glass plate with two parallel surfaces. The light beam group L18 formed by the multiple beams of light exiting from the second exit surface 38 of the second birefringent crystal 36 is parallel to the light beam L14 incident on the isolation component 30, that is, the light beam group L18 is also parallel to the incident light beams L11 and L12. Finally, the light beam group L18 is incident on multiple output collimators.

[0044] Since the propagation directions of ordinary light and extraordinary light in the birefringent crystal are different, the propagation paths of ordinary light and extraordinary light in the birefringent crystal undergo lateral translation. Coupled with the fact that the first birefringent crystal 31 and the second birefringent crystal 36 are both wedge-shaped crystals, the ordinary light and the extraordinary light are further separated, that is, the lateral distance between the ordinary light and the extraordinary light is increased. Therefore, after passing through the isolation component 30, the originally combined light beam L14 is split into multiple beams of light and exits from multiple output collimators.

[0045] Since the light beam L14 incident on the isolation component 30 contains two different wavelengths, and each wavelength of the light beam will be decomposed into ordinary light and extraordinary light. This embodiment utilizes the characteristic that ordinary light and extraordinary light with different wavelengths have different refractive indices in the birefringent crystal, so that after passing through the isolation component 30, it can be split into four different beams of light, that is, a light beam group L18 is formed, thereby realizing the function of wavelength division multiplexing. It can be seen that this embodiment can combine the light beam with the first wavelength and the light beam with the second wavelength, and through the isolation component 30, the combined light beam is laterally offset according to the wavelength and polarization state, so as to realize the function of splitting light according to the wavelength and polarization state.

[0046] See Figure 4, when the return light L21 returned from the output collimator is incident on the isolation component 30, it first enters the second birefringent crystal 36 and forms two beams of light L22 and L23 with mutually perpendicular polarization states. Subsequently, the two beams of light L22 and L23 are incident on the Faraday rotator 34, causing the polarization states of the two beams of light to deflect, for example, rotate by 45°, and finally enter the first birefringent crystal 31 to form beams of light L24 and L25 respectively. Compared with the beams of light L22 and L23 transmitted in the second birefringent crystal 36, the beams of light L24 and L25 are equivalent to the interchange of ordinary and extraordinary light. Since the optical axes of the first birefringent crystal 31 and the second birefringent crystal 36 form an angle of 45°, the beams of light L24 and L25 transmitted in the reverse direction will deviate from Figure 3 the incident optical path shown, therefore, the function of the isolation component is equivalent to the scattering effect of a Wollaston prism, making the return light L21 incident in the reverse direction unable to be combined, and thus unable to enter the light combining component 20, and even less likely to enter the two incident collimators, thereby realizing the function of reverse isolation. In addition, since the isolation component 30 can achieve a scattering effect similar to a Wollaston prism, the reverse isolation efficiency for the return light is much higher than that of a traditional wavelength division multiplexer.

[0047] Second Embodiment:

[0048] See Figure 5 , the miniaturized wavelength division multiplexer of this embodiment is composed of a light combining component 50 and an isolation component 60, and the light combining component 50 and the isolation component 60 are encapsulated in a sleeve 40. The light combining component 50 is composed of a glass sheet 51 and a reflective device. The reflective device in this embodiment is a right-angled prism 55. The glass sheet 51 has a first light passing surface 52 and a second light passing surface 53, where the first light passing surface 52 is the surface where the light beam is incident, and the second light passing surface 53 is the surface where the light beam exits. The first light passing surface 52 and the second light passing surface 53 are arranged parallel to each other.

[0049] The right-angled prism 55 is arranged on one side of the glass sheet 51, specifically, on one side of the second light passing surface 53. The hypotenuse of the right-angled prism 55 is the reflective surface 56, which can reflect the light beam to the second light passing surface 53.

[0050] Moreover, the light combining component 50 is encapsulated in the sleeve 40. Preferably, the outer diameter of the light combining component 50 is equal to the inner diameter of the sleeve 40, and the light combining component 50 is prevented from moving axially or radially within the sleeve 40.

[0051] The isolation component 60 is arranged on the light-emitting side of the light-combining device 50 and is composed of a first birefringent crystal 61, a rotating device, and a second birefringent crystal 66 in sequence along the optical path. Among them, the rotating device in this embodiment is a Faraday rotator 64. Moreover, both the first birefringent crystal 61 and the second birefringent crystal 66 are wedge-shaped. The first birefringent crystal 61 has a first incident surface 62 and a first exit surface 63, and the second birefringent crystal 66 has a second incident surface 67 and a second exit surface 68. The Faraday rotator 64 is clamped between the first birefringent crystal 61 and the second birefringent crystal 66.

[0052] The structures of the first birefringent crystal 61 and the second birefringent crystal 66 are exactly the same, and they are symmetrically arranged on both sides of the Faraday rotator 64 with the axis of the miniaturized wavelength division multiplexer as the center. In addition, the optical axes of the first birefringent crystal 61 and the second birefringent crystal 66 form an angle of 45°. A magnet 65 is arranged outside the Faraday rotator 64. The magnet 65 is a magnetic ring, and the first birefringent crystal 61, the Faraday rotator 64, and the second birefringent crystal 66 are all located inside the magnet 65.

[0053] The optical path in this embodiment is the same as that in the first embodiment. Two mutually parallel incident light beams are respectively incident on the glass sheet 51 and the right-angle prism 55. The first light beam exits from the second light-passing surface 53 after passing through the glass sheet 51, and the second light beam is reflected by the reflecting surface 56 and then incident on the second light-passing surface 53, and is combined with the first light beam at the second light-passing surface 53. The combined light beam forms multiple mutually parallel light beams after passing through the isolation component 60 and then exits to multiple output collimators.

[0054] If there is retroreflected light from the output collimator, the retroreflected light cannot be incident on the light-combining component due to divergence. Therefore, it can effectively avoid the interference of the retroreflected light on the light beam output from the input collimator.

[0055] It can be seen that the miniaturized wavelength division multiplexer of the present invention is composed of a light-combining assembly and an isolation component, and does not require the setting of complex devices such as reflectors, half-wave plates, and polarizers. Moreover, the light-combining component and the isolation component are closely arranged in the sleeve, and the overall structure of the wavelength division multiplexer is compact, which is conducive to the miniaturization of the wavelength division multiplexer.

[0056] In addition, since the optical axes of the first birefringent crystal and the second birefringent crystal are symmetric with each other, when assembling the wavelength division multiplexer, only two birefringent crystals with exactly the same structure need to be prepared, and the two birefringent crystals are arranged symmetrically with the axis of the wavelength division multiplexer as the center on both sides of the Faraday rotator. The assembly of the isolation component is very simple, and the production cost of the wavelength division multiplexer can also be reduced.

[0057] Finally, it should be emphasized that the above are only the preferred embodiments of the present invention and are not used to limit the present invention. For those skilled in the art, the present invention can have various changes and modifications. Any modifications, equivalent replacements, improvements, etc. made within the spirit and principle of the present invention shall be included within the protection scope of the present invention.

Claims

1. Miniaturized wavelength division multiplexer, comprising a light combining component and an isolation component; Characterized in that ； The light combining component consists of a glass sheet and a reflective device. The glass sheet has a first light passing surface and a second light passing surface that are parallel to each other. The reflective device is disposed on one side of the glass sheet, and the reflective surface of the reflective device is parallel to the second light passing surface. A light beam of a first wavelength is incident from the first light passing surface and exits from the second light passing surface. A light beam of a second wavelength is incident from the reflective device and, after passing through the reflective surface, is incident on the second light passing surface. The light beam of the first wavelength and the light beam of the second wavelength are combined at the second light passing surface; The isolation component is located at the output end of the light combining component. The isolation component consists of a first birefringent crystal, a rotating device, and a second birefringent crystal arranged in sequence along the optical path. The first incident surface of the first birefringent crystal is parallel to the second output surface of the second birefringent crystal, and the optical axis of the first birefringent crystal forms an angle of 45° with the optical axis of the second birefringent crystal; The light beam of the first wavelength is incident on the first birefringent crystal to form an ordinary light and an extraordinary light with perpendicular polarization states. The light beam of the second wavelength is incident on the first birefringent crystal to form an ordinary light and an extraordinary light with perpendicular polarization states. Moreover, the refractive indices of the ordinary light and the extraordinary light formed by the light beam of the first wavelength and the light beam of the second wavelength in the birefringent crystal are different. The light beam of the first wavelength and the light beam of the second wavelength pass through the isolation component to form four light beams; The light beam exiting from the second birefringent crystal realizes lateral offset according to wavelength and polarization state.

2. The miniaturized wavelength division multiplexer according to claim 1, wherein: The reflective device is a rhombic prism, and the first inclined surface of the rhombic prism is the reflective surface, and the second inclined surface opposite to the first inclined surface is closely attached to the second light passing surface.

3. The miniaturized wavelength division multiplexer according to claim 1, wherein: The reflective device is a right-angled prism.

4. The miniaturized wavelength division multiplexer according to any one of claims 1 to 3, wherein: The shape of the first birefringent crystal is exactly the same as the shape of the second birefringent crystal.

5. The miniaturized wavelength division multiplexer according to claim 4, wherein: The first birefringent crystal and the second birefringent crystal are symmetrically arranged on both sides of the rotating device with the axis of the miniaturized wavelength division multiplexer as the center.

6. The miniaturized wavelength division multiplexer according to any one of claims 1 to 3, wherein: The rotating device includes a Faraday rotation sheet, and a magnet is disposed outside the Faraday rotation sheet.

7. The miniaturized wavelength division multiplexer according to any one of claims 1 to 3, wherein: The light combining component and the isolation component are encapsulated in a sleeve.

8. The miniaturized wavelength division multiplexer according to claim 7, wherein: The first incident surface of the first birefringent crystal is inclined with respect to the axis of the sleeve.

9. The miniaturized wavelength division multiplexer according to claim 8, wherein: The first exit surface of the first birefringent crystal is parallel to the second entrance surface of the second birefringent crystal, and the rotation device is clamped between the first exit surface of the first birefringent crystal and the second entrance surface of the second birefringent crystal.

10. The miniaturized wavelength division multiplexer according to claim 9, wherein: The first exit surface of the first birefringent crystal is perpendicularly arranged to the axis of the sleeve.

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