A fixed-attenuation optical isolator

Abstract

The utility model discloses a fixed attenuation's optical isolator, including magnetic ring, and the half wave plate of custom light axis angle, 0 degree polaroid, Faraday rotator piece and 45 degree polaroid who set in the magnetic ring inside and set gradually on the positive light path, and the light of input light beam horizontal polarization direction passes through the half wave plate of prearranged light axis angle alpha, and the polarization rotation angle theta of light beam =2*alpha, and after passing through the first polaroid (0 degree), realizes the attenuation to the positive input light according to Malus law, and the light beam passes through Faraday rotator piece in turn, and the second polaroid (45 degree) forms the function of positive attenuation. Simultaneous reverse transmission because Faraday magneto-optic effect realizes the function of complete blocking. In part use scene, this attenuation isolator not only can reduce the superposition of coupling path and cause the problem of large space occupation, but also can realize the function of specified attenuation to the positive transmission light, has prominent substantial characteristics.

Description

Technical Field

[0001] This utility model relates to the field of optical isolators, and in particular to an optical isolator with fixed attenuation. Background Technology

[0002] Optical isolators are primarily used in optical communication systems to suppress back-propagating light, protect lasers from feedback interference, and improve system stability. An optical isolator is an optical device that allows light to pass through in only one direction while blocking backlighting. It is essentially an optical diode or a one-way valve.

[0003] However, the current industry commonly uses the "isolation device + attenuator" series connection method, which results in more optical path interfaces, increased coupling loss, large space occupation, and poor attenuation consistency.

[0004] Therefore, a fixed-attenuation optical isolator is still needed to solve the above problems. Utility Model Content

[0005] This invention provides a fixed attenuation optical isolator to solve the above-mentioned problems.

[0006] The objective of this utility model is achieved through the following technical solution: A fixed-attenuation optical isolator includes a magnetic ring, and an adjustable optical axis half-wave plate, a 0° polarizer, a Faraday rotator, and a 45° polarizer arranged sequentially inside the magnetic ring on the positive optical path. The angle between the polarization direction of the linearly polarized light passing through the adjustable optical axis half-wave plate and the polarization direction of the transmission axis of the 0° polarizer is θ.

[0007] In one embodiment, the substrate of the adjustable optical axis half-wave plate is quartz or lithium niobate.

[0008] In one embodiment, the angle between the adjustable optical axis and the horizontal plane is α, where θ = 2*α.

[0009] In one embodiment, the 0° polarizer uses quartz glass as the substrate.

[0010] In one embodiment, the Faraday rotator is made of garnet crystal magneto-optical material, with a rotation angle accuracy of ±0.5° and an extinction ratio of ≥40dB.

[0011] In one embodiment, the 45° polarizer uses quartz glass as the substrate.

[0012] Compared with the prior art, the beneficial effects of this utility model include at least the following: When a beam of 0° polarized light passes through an adjustable optical axis half-wave plate and rotates to form an angle θ with the 0° polarizer, the power attenuation of the light is based on Malus's law and satisfies the formula: I0 = I * cos 2 (θ), where I is the output light power, I0 is the light power of the linearly polarized light after passing through the 0° polarizer, and θ is the angle between the transmission direction of the 0° polarizer and the polarization direction of the linearly polarized light after passing through the adjustable half-wave plate. θ = 2*α. By setting or changing the angle between the optical axis of the adjustable half-wave plate and the 0° polarizer, the specified attenuation can be precisely controlled. In the reverse optical path, the polarized light first passes through the 45° polarizer and enters the Faraday rotator, and after being rotated 45 degrees, it is perpendicular to the horizontal plane. Finally, it is completely absorbed by the 0° polarizer, achieving the effect of complete reverse blocking. This not only reduces the problem of large space occupation caused by the superposition of coupling paths, but also realizes the function of specified attenuation of forward input light, which has outstanding substantial features. Attached Figure Description

[0013] Figure 1 This is a schematic diagram of the fixed attenuation optical isolator structure according to an embodiment of the present invention; Figure 2 This is a diagram showing the polarization state change of positively polarized light in Embodiment 1 of this utility model; Figure 4 This is a diagram showing the polarization state change of reverse polarized light in Embodiment 1 of this utility model; Figure 3 This is a diagram showing the polarization state change of positively polarized light in Embodiment 2 of this utility model; Figure 5 This is a diagram showing the polarization state change of reverse polarized light in Embodiment 2 of this utility model; Figure 6 This is a graph showing the relationship between the θ angle and the attenuation ratio in an embodiment of this utility model.

[0014] Illustration: 1. Adjustable optical axis half-wave plate; 2. 0° polarizer; 3. Faraday rotator; 4. 45° polarizer; 5. Magnetic ring. Detailed Implementation

[0015] Exemplary embodiments will now be described more fully with reference to the accompanying drawings. However, these exemplary embodiments can be implemented in many forms and should not be construed as limited to the embodiments set forth herein; rather, these embodiments are provided to make the present invention more comprehensive and complete, and to fully convey the concept of the exemplary embodiments to those skilled in the art. The same reference numerals in the drawings denote the same or similar structures, and therefore repeated descriptions of them will be omitted.

[0016] The terms used to describe position and direction in this utility model are illustrated with the accompanying drawings, but changes can be made as needed, and all such changes are included within the scope of protection of this utility model.

[0017] Reference Figure 1 This invention provides a fixed-attenuation optical isolator, comprising a magnetic ring 5, and an adjustable optical axis half-wave plate 1, a 0° polarizer 2, a Faraday rotator 3, and a 45° polarizer 4, which are sequentially arranged inside the magnetic ring 5 and on the positive optical path. The linearly polarized light passing through the half-wave plate 1 with a customized optical axis angle α has an angle θ between its polarization direction and the transmission axis polarization direction of the 0° polarizer 2. When the 0° polarized light passes through the adjustable optical axis half-wave plate 1, it outputs a portion of the polarized light after being rotated and attenuated by the 0° polarizer 2. Then, the attenuated polarized light continues to rotate under the rotation of the Faraday rotator 3 and is finally output through the 45° polarizer 4. The attenuation occurs between the adjustable optical axis half-wave plate 1 and the 0° polarizer 2, with the 0° polarizer 2 absorbing a portion of the light. When 45-degree polarized light is incident in the reverse direction, the 45-degree polarized light enters the Faraday rotator 3, and after being rotated 45 degrees by the Faraday rotator 3, it becomes perpendicular to the horizontal plane and is completely absorbed by the 0° polarizer 2, thus completely blocking the reverse input. By adjusting the optical axis of the adjustable optical axis half-wave plate 1, it is possible to simultaneously achieve stable control of different degrees of power attenuation while satisfying the unidirectional blocking method. Compared with the traditional multi-series method, it effectively reduces the increase in loss caused by coupling and the problem of difficulty in control. In addition, the adjustable optical axis half-wave plate 1 is directly attached to the 0° polarizer 2, which has a high degree of integration and does not occupy additional volume other than the magnetic ring 5, making it compact and small.

[0018] Preferably, the substrate of the optical axis half-wave plate 1 is a quartz crystal or a lithium niobate crystal. Using a quartz crystal as the wave plate substrate has high stability, low insertion loss, and high reliability; using lithium niobate enables its electro-optic tunability and high birefringence, thereby achieving wavelength tuning, dynamic control, or on-chip integration functions.

[0019] Preferably, the angle between the optical axis of the optical axis half-wave plate 1 and the horizontal plane is α, where θ = 2*α. The linearly polarized light after passing through the half-wave plate 1 forms a certain angle θ with the transmission axis of the 0° polarizer 2. Combined with Malus's law, the polarized light can be attenuated. Then, the Faraday rotation plate is rotated by magneto-optical effect to finally output polarized light attenuated by 45°.

[0020] Preferably, the 0° polarizer 2 uses quartz crystal glass as the substrate. This ensures the ultimate and stable polarization core functions (high extinction ratio, low loss).

[0021] Preferably, the Faraday rotator 3 is made of garnet crystal magneto-optical material, with a rotation angle accuracy of ±0.5° and an extinction ratio ≥40dB. The magnetic field strength meets the requirements of Faraday rotation, generally greater than or equal to 700 Oe, wherein the isolator size is less than or equal to 1 mm.

[0022] Preferably, the 45° polarizer 4 uses quartz glass as the substrate.

[0023] Reference Figure 2 Based on Malus's law, the present invention satisfies the formula: I0 = I * cos 2 (θ), where I is the output light power, I0 is the light power of the linearly polarized light after passing through the 0° polarizer 2, and θ is the angle between the transmission direction of the 0° polarizer 2 and the polarization direction of the linearly polarized light after passing through the adjustable half-wave plate. When the incident light is 0°, the relationship between the adjustable optical axis half-wave plate 1 and the attenuation ratio is shown in the graph. The horizontal axis represents the angle θ, the left vertical axis represents the attenuation ratio, and the right vertical axis represents the fixed loss. This achieves a fixed and controllable attenuation relative to the input light power at a wavelength of 1310nm.

[0024] In the following examples, the dashed light is the back polarization state (i.e., before passing through the lens or Faraday rotator), which is realized as the current polarization state (i.e., after passing through the lens or Faraday rotator).

[0025] Example 1 Reference Figure 2 A beam of horizontally polarized light is transmitted in the forward direction and modulated by a custom-designed half-wave plate 1 with an optical axis α of 15°. The output polarized light forms an angle θ of 30° with the transmission axis of the 0° polarizer 2. According to Malus's law, the output light power is attenuated by 25% at this time. The output light from the 0° polarizer is rotated by a Faraday rotator 3 by a polarization angle of 45°, and finally output through the 45° polarizer 4.

[0026] Reference Figure 4 When the light is input in the reverse direction, 45-degree polarized light is selected and then rotated by Faraday rotator 3 to a polarization angle of 45 degrees, forming a 90-degree angle perpendicular to the horizontal plane, and then completely absorbed and blocked by 0° polarizer 2.

[0027] Example 2 Reference Figure 3 A beam of horizontally polarized light is transmitted in the forward direction and modulated by a custom-designed half-wave plate 1 with an optical axis α of 30°. The output polarized light forms an angle θ of 60° with the transmission axis of the 0° polarizer 2. According to Malus's law, the output light power is attenuated by 75% at this time. The output light from the 0° polarizer is rotated by a Faraday rotator 3 by a polarization angle of 45°, and finally output through the 45° polarizer 4.

[0028] Reference Figure 5When the light is input in the reverse direction, 45-degree polarized light is selected and then rotated by Faraday rotator 3 to a polarization angle of 45 degrees, forming a 90-degree angle perpendicular to the horizontal plane, and then completely absorbed and blocked by 0° polarizer 2.

[0029] In summary, the way the half-wave plate 10° polarizer 2, Faraday rotator 3 and 45° polarizer 4 are set and bonded together in this utility model can meet the requirements of high stability and controllable power attenuation, as well as complete blocking of reverse light. It also eliminates the need for multiple couplings in series, which would result in too many optical path interfaces and difficulty in controlling losses. Furthermore, the integrated design has high consistency and is more compact in overall size, without occupying extra space.

[0030] Although embodiments of the present invention have been shown and described above, it is understood that the above embodiments are exemplary and should not be construed as limiting the present invention. Those skilled in the art can make changes, modifications, substitutions and alterations to the above embodiments within the scope of the present invention without departing from the principles and spirit of the present invention, and all such changes should fall within the protection scope of the claims of the present invention.

Claims

1. A fixed attenuation optical isolator, characterized in that, It includes a magnetic ring, and an adjustable optical axis half-wave plate, a 0° polarizer, a Faraday rotator plate and a 45° polarizer arranged sequentially inside the magnetic ring on the positive optical path. The angle between the linearly polarized light passing through the adjustable optical axis half-wave plate and the polarization direction of the transmission axis of the 0° polarizer is θ.

2. The optical isolator according to claim 1, characterized in that, The substrate of the adjustable optical axis half-wave plate is quartz or lithium niobate.

3. The optical isolator according to claim 1, characterized in that, The angle between the optical axis of the adjustable optical axis half-wave plate and the horizontal plane is α, θ=2*α.

4. The optical isolator according to claim 1, characterized in that, The 0° polarizer uses quartz glass as its substrate.

5. The optical isolator according to claim 1, characterized in that, The Faraday rotator is made of garnet crystal magneto-optical material, with a rotation angle accuracy of ±0.5° and an extinction ratio of ≥40dB.

6. The optical isolator according to claim 1, characterized in that, The 45° polarizer uses quartz glass as its substrate.

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