Two-dimensional optical fiber collimator array capable of easily adjusting light beam direction and optical communication system

Abstract

The invention relates to a two-dimensional optical fiber collimator array capable of easily adjusting light beam direction and an optical communication system. The two-dimensional optical fiber collimator array comprises an optical fiber array, the first micro lens array is fixed on the rear end surface of the optical fiber array; the second micro-lens array is arranged behind the first micro-lens array, and the light emitting side of the second micro-lens array is a spherical surface with a uniform curvature radius; the plurality of plano-concave lenses are arranged behind the second micro-lens array, each plano-concave lens corresponds to one optical channel, the curvature radius of the concave surface of each plano-concave lens is matched with the curvature radius of the spherical surface of the second micro-lens array, and a slidable gluing interface is formed through a curable optical adhesive layer; wherein the plano-concave lens can be adjusted in a sliding mode along the spherical surface, and the deflection angle of the output light beam is controlled by controlling the sliding arc length of the plano-concave lens. Through an innovative optical structure and an adjustment mechanism, the contradiction between the adjustment sensitivity and the precision of a traditional calibration method under a high-density integration background is effectively overcome.

Description

TECHNICAL FIELD

[0001] The present application relates to the field of optical communication technology, in particular to a two-dimensional optical fiber collimator array with adjustable beam pointing and an optical communication system. BACKGROUND

[0002] The two-dimensional optical fiber collimator array is a core basic element for constructing modern large-scale optical communication systems, high-performance optical phased arrays, and data center optical interconnection architectures. Its core function is to efficiently convert the optical signals conducted in densely arranged multiple optical fibers into collimated beam arrays that propagate in free space and are highly parallel to each other, or to realize the reverse optical coupling. The parallelism of the output beams (i.e., "light consistency") is a key indicator of array performance, directly determining the uniformity of insertion loss, inter-channel crosstalk level, and ultimately the signal fidelity of the entire optical system.

[0003] As optical communication technology evolves towards higher capacity and higher integration, the channel density of the two-dimensional optical fiber collimator array is increasing, and the channel pitch is continuously shrinking. This high-density integration trend has dramatically magnified the microscopic tolerance problems in the manufacturing and assembly process. The positioning errors of optical fibers in the microgrooves of the substrate, the deviations of lens optical centers and mechanical centers, the non-uniformity of the glue layer, and many other micron or even nanometer error sources will be coupled and accumulated, ultimately resulting in the dispersion of the pointing angles of the output beams of each channel, severely damaging the parallelism of the beam group.

[0004] In order to correct these inherent errors during the assembly stage and achieve excellent channel consistency, the industry must introduce a precise calibration process before packaging and curing. Currently, a mainstream calibration approach is based on the lateral translation of lenses. This approach usually requires temporarily fixing the lens array on a reference plane through a layer of uncured glue, then applying a lateral pushing force to each lens through a precision mechanism to make it slide in a two-dimensional plane, adjusting the beam angle by changing the lateral relative position of the lens optical center and the optical fiber core, and then curing the glue to lock the position after calibration is completed.

[0005] However, this calibration paradigm based on lateral translation has inherent technical bottlenecks that are difficult to overcome when faced with high-density, short-focal-length micro-lens arrays:

[0006] First, the contradiction between sensitivity and accuracy: according to the principle of geometric optics, the beam deflection angle θ and the lateral displacement amount Δd approximately satisfy the relationship: θ≈Δd / f (where f is the focal length of the lens). In high-density arrays, in order to maintain compactness, the lens focal length f is usually designed to be very short (e.g. 1-2 mm). This means that even if a very small angle (e.g. 0.1°, about 1.75 mrad) needs to be corrected, the required physical displacement amount Δd has entered the micron or even sub-micron level (e.g. when f = 1 mm, Δd≈1.75 μm). The displacement control of this order of magnitude puts almost stringent requirements on the accuracy, stability and environmental anti-interference ability of the driving mechanism, greatly increasing the difficulty, time and cost of the calibration process.

[0007] Second, the limitation of adjustment freedom: lateral translation only provides two degrees of freedom of adjustment capability, which is single and insufficient for the comprehensive problem caused by complex spatial errors, and it is difficult to achieve the optimal calibration state.

[0008] Finally, the risk of long-term stability: relying on the mechanism of overcoming static friction in the plane and then making a small slide and locking, there is a risk of repeatability and long-term stability. Small stress relaxation, colloidal creep or temperature change can cause micro-drift of the calibrated position, resulting in degradation of beam parallelism in subsequent use.

[0009] Therefore, there is an urgent need in the art for a breakthrough calibration architecture and adjustment mechanism. It needs to be able to fundamentally reduce the adjustment sensitivity, increase the physical displacement amount required for calibration from the "micron level" which is difficult to reliably control to the "ten micron level" which is easier to achieve; it needs to provide better adjustment linearity and stability to simplify the calibration process and ensure the long-term reliability of the product; finally, it needs to solve the light consistency problem of high-density fiber collimator array in an efficient and reliable way. SUMMARY

[0010] The purpose of the present application is to overcome the shortcomings of the prior art and provide a two-dimensional fiber collimator array with easy-to-adjust beam pointing and optical communication system, which effectively overcomes the adjustment sensitivity and accuracy contradiction faced by traditional calibration methods under the background of high-density integration through innovative optical structure and adjustment mechanism.

[0011] To achieve the above purpose, the technical scheme adopted by the present application is as follows:

[0012] An easy-to-adjust beam pointing two-dimensional fiber collimator array with easy-to-adjust beam pointing, comprising:

[0013] a fiber array, which is arranged in a two-dimensional matrix form by a plurality of optical fibers and is fixed in a substrate;

[0014] a first microlens array fixed to a rear end surface of the optical fiber array for collimating light beams emitted by each optical fiber channel;

[0015] a second microlens array arranged behind the first microlens array, with a spherical surface having a uniform radius of curvature on a light emitting side thereof;

[0016] a plurality of plano-concave lenses arranged behind the second microlens array, each of the plano-concave lenses corresponding to an optical channel, and having a concave surface with a radius of curvature matched to that of the spherical surface of the second microlens array, and forming a slidable adhesive interface through a curable optical adhesive layer;

[0017] wherein the plano-concave lenses are capable of being adjusted in sliding along the spherical surface, and the deflection angle of the output light beams is controlled by controlling the sliding arc length of the plano-concave lenses.

[0018] Further, the sliding of the plano-concave lenses is realized through manual or high-precision driving mechanisms.

[0019] Further, the optical adhesive layer provides lubrication during adjustment, and is fixed after the adjustment is completed through curing.

[0020] Further, the matching tolerance of the radius of curvature of the plano-concave lenses and the second microlens array is less than 1%.

[0021] Further, the sliding adjustment of the plano-concave lenses does not require additional precise guiding mechanisms, and directly relies on the self-guiding of the spherical surface.

[0022] The present application is a kind of optical communication system, comprising the two-dimensional optical fiber collimator array of the easily adjustable light beam pointing as described above.

[0023] The light beam adjustment principle of the present application is based on precise geometric optical relationship. When the light beam pointing of a specific channel needs to be corrected, a tangential force is applied to the corresponding plano-concave lens through a precise driving method, so that it slides along the matching spherical surface by an arc length Δs. This movement makes the optical axis of the plano-concave lens rotate an angle The mathematical relationship satisfies:

[0024]

[0025] wherein R is the radius of curvature of the spherical surface. Under the paraxial optical approximation condition, the deflection angle θ of the output light beam and the rotation angle of the lens satisfy the following relationship:

[0026]

[0027] Where n is the refractive index of the lens, this simple and accurate mathematical relationship reveals the significant advantage of the present invention over the traditional scheme. Recall that for the traditional lateral translation scheme, the beam deflection angle θ and the lateral displacement amount Δd satisfy the relationship θ ≈ Δd / f, where f is the focal length of the lens. The adjustment sensitivity of the two schemes is in sharp contrast:

[0028] Adjustment sensitivity of the traditional scheme: Δd / θ = f; adjustment sensitivity of the present invention: Δs / θ = R / (n-1).

[0029] By designing a radius of curvature R much larger than the focal length f of the lens (for example, R = 5f to 10f), and choosing a low refractive index material, the adjustment sensitivity is reduced. The present invention increases the physical displacement amount required to produce the same deflection angle θ from the traditional scheme's Δd to This essential improvement liberates the displacement control from the "micron level" field that is difficult to stably achieve to the "ten-micron level" field that is easier to accurately control, greatly reducing the stringent requirements for the driving mechanism, while improving the repeatability and reliability of the calibration process.

[0030] With the technical scheme described above, compared with the prior art, the present invention has the beneficial effects that:

[0031] Firstly, the perfect linear relationship between θ and Δs makes the prediction and control of the calibration amount extremely direct, facilitating the realization of automatic assembly and adjustment, and significantly improving the production efficiency; secondly, due to the increase in the displacement amount, the influence of nonlinear factors such as the return gap and friction in the mechanical structure on the adjustment accuracy is relatively weakened; thirdly, after the adjustment is completed, the optical glue is cured by local irradiation with ultraviolet light, and the plano-concave lens is firmly locked in the optimal position, and the large-area spherical contact structure between the plano-concave lens and the second microlens array provides mechanical stability and stress relaxation resistance far superior to the traditional small-area planar contact.

[0032] In terms of optical performance, the present invention maximally reduces the insertion loss through the optimization design of multiple optical interfaces. The bonding interface between the fiber array and the first microlens array, the interface between the first microlens array and the air, and the matching interface between the second microlens array and the plano-concave lens are all carefully designed for refractive index matching and anti-reflection treatment, ensuring excellent optical transmission efficiency in the entire working wavelength range. In particular, the curvature matching design between the second microlens array and the plano-concave lens not only provides precise adjustment function, but also effectively suppresses interface reflection through continuous transition of the refractive index, further improving the optical performance of the system.

[0033] The present application also considers thermal stability and long-term reliability. The thermal expansion coefficients of all optical component materials are carefully matched, and the structural design takes into account the stress distribution when the temperature changes, ensuring excellent optical performance within the operating temperature range of -40°C to +85°C. The packaging structure uses a metal shell combined with flexible cushioning material, effectively absorbing the energy from mechanical vibration and impact, ensuring long-term stable operation of the product in harsh environments.

[0034] In summary, the present application constructs a complete high-precision optical beam pointing correction system. This adjustment mechanism based on curvature matching and arc displacement not only provides a new calibration method, but also solves the common problem in the field of fine tuning of high-density optoelectronic devices in principle. It gives the two-dimensional fiber collimator array unprecedented ease of adjustment, excellent calibration accuracy and long-term working reliability, while maintaining the compactness of the structure and the feasibility of the process, providing a superior performance core optical engine for the next generation of ultra-high-speed optical communication, precision optical sensing and advanced optical phased array systems. BRIEF DESCRIPTION OF DRAWINGS

[0035] The present application will be further described in detail below in combination with the drawings and specific embodiments:

[0036] Figure 1 Figure 1 is a cross-sectional structure diagram of the two-dimensional fiber collimator array of the present application;

[0037] Figure 2 Figure 2 is a schematic diagram of the overall structure and optical transmission of the present application;

[0038] Figure 3 Figure 3 is a schematic diagram of the principle of beam deflection by sliding a plano-concave lens along the spherical surface;

[0039] Figure 4 Figure 4 is a schematic diagram of the adjustment principle when assembly or machining tolerances occur;

[0040] Wherein: 101-fiber array; 102-first microlens array; 103-second microlens array; 104-plano-concave lens. DETAILED DESCRIPTION

[0041] The present application will be further described in detail below in combination with the drawings and specific embodiments:

[0042] Please refer to Figure 1 and Figure 2The embodiment provides a 9*9 two-dimensional fiber collimator array, which is applied to an optical communication system, and the two-dimensional fiber collimator array comprises four main components: a fiber array 101, a first microlens array 102, a second microlens array 103 and a plano-concave lens 104. The components are arranged in sequence according to the light path transmission direction. The whole array adopts a modular design, and each component can be independently manufactured and quickly and accurately assembled through a precise positioning structure.

[0043] The fiber array 101 is located at the front end, and the fiber array is used as an optical signal input end, a plurality of single-mode or multi-mode optical fibers are arranged in a two-dimensional matrix form, and are fixed in a precise substrate. The substrate material is preferably ceramic or monocrystalline silicon with a thermal expansion coefficient matched with the optical fiber, a regular microgroove structure is formed through a precise microprocessing technology, the positioning accuracy of the optical fiber reaches a submicron level, so that each optical fiber channel can be accurately aligned with subsequent optical elements. All the end faces of the optical fibers are processed through a one-time integral polishing process to form a common optical plane with nanometer smoothness, the flatness is better than 0.1 microns, the surface roughness Ra is less than 3nm, and the optical consistency reference of the whole system is provided.

[0044] The first microlens array 102 is fixed at the rear end of the polished end face of the fiber array 101, and the function of the first microlens array 102 is to realize collimation of a light beam, a plurality of microlenses are arranged in a two-dimensional matrix form corresponding to the fiber array. Each microlens is accurately aligned with the corresponding optical fiber channel to convert the divergent light beam from the optical fiber into a high-quality collimated light beam. The first microlens array 102 and the fiber array 101 are permanently combined through ultraviolet curing optical glue to form an integrated fiber-microlens module, and the integrated design significantly improves the mechanical stability and temperature adaptability of the component. In addition, the lens array is processed by using a precise replication process to ensure that each lens has good consistency.

[0045] The second microlens array 103 is located at the rear of the first microlens array 102, and the second microlens array 103 is unique in that the light-out surface facing the rear is processed into a precise spherical surface with a uniform radius of curvature. The spherical surface is made through an advanced glass molding or computer-controlled polishing process. The second microlens array 103 is selected from optical glass materials with high light transmittance and low thermal expansion coefficient, such as fused quartz or BK7 glass, and a broadband anti-reflection film is coated on the surface to ensure excellent optical performance in the working wavelength range.

[0046] The independently adjustable plano-concave lens 104 is one of the core components of the present application, which, together with the second microlens array 103, constitutes the adjustment mechanism. Each plano-concave lens 104 precisely corresponds to an optical channel and is arranged behind the second microlens array 103. The concave curvature radius of each plano-concave lens 104 is strictly consistent with the spherical curvature radius of the second microlens array 103, achieving perfect geometric matching. The plane side of these plano-concave lenses faces the rear free space, and the selection of the optical material thereof fully considers the matching of the dispersion characteristics with the second microlens array 103. During the assembly calibration phase, the concave surface of each plano-concave lens forms temporary optical contact and mechanical connection with the spherical surface of the second microlens array 103 through a layer of uncured optical adhesive with refractive index matching characteristics, constituting a dynamic adhesive interface that can guarantee the continuity of the optical path and allow precise sliding.

[0047] Please refer to Figure 2 which shows the overall structure of the present application and the complete optical path transmission diagram. After the optical signal is emitted from the fiber array 101, it first propagates to the first microlens array 102 with a certain divergence angle. After collimation by the first microlens array 102, the divergent light beam is converted into a parallel light beam with good collimation characteristics. These collimated light beams continue to transmit to the second microlens array 103 and enter the corresponding plano-concave lens 104 after passing through the spherical surface thereof.

[0048] During the entire optical path transmission process, each optical interface is carefully optimized and designed. In particular, the spherical surface of the second microlens array 103 and the mating surface of the plano-concave lens 104 adopt strict curvature matching design (the curvature radius matching tolerance of the plano-concave lens 104 and the second microlens array 103 is less than 1%), which ensures that the light beam can maintain excellent wavefront quality when passing through each interface. The final output collimated light beam not only has good parallelism, but also can maintain stable spot shape and energy distribution during propagation.

[0049] Please refer to Figure 3This figure illustrates in detail the working principle of adjusting the beam deflection angle by sliding a plano-concave lens along a spherical surface. When it is necessary to adjust the beam direction of a specific channel, a precisely controlled tangential force can be applied to the corresponding plano-concave lens 104 manually or through a high-precision drive mechanism (a dedicated fine-tuning device). This force allows the plano-concave lens 104 to slide smoothly along the spherical surface of the second microlens array 103, with the sliding trajectory strictly following the curvature characteristics of the sphere. During the sliding adjustment process, the adhesive interface between the plano-concave lens 104 and the second microlens array 103 maintains excellent optical contact. The sliding adjustment of the plano-concave lens 104 does not require an additional precision guiding mechanism; it relies directly on the spherical surface for guidance. This special design ensures the continuity of the optical path and provides the necessary mechanical freedom for precise position adjustment. The optical adhesive layer between the plano-concave lens 104 and the second microlens array 103 provides lubrication during the adjustment process and achieves permanent fixation through curing after adjustment. By controlling the sliding arc length of the plano-concave lens, the deflection angle of its optical axis can be precisely controlled, thereby achieving fine control over the direction of the output beam.

[0050] Please refer to Figure 4 As shown, if a deviation occurs between the fiber array 101 and the first microlens array 102 during assembly or processing, the emitted beam will have an angle deviation of θ1. At this time, when the plano-concave lens 104 slides along the matching spherical surface by an arc length Δs, its optical axis will rotate by an angle. The deflection angle θ of the output beam satisfies the following relationship:

[0051]

[0052] Where R is the radius of spherical curvature, and n is the refractive index of the material. By setting R much larger than the focal length f of the first microlens array (R³3f, for example R=5f to 10f), and choosing a low refractive index material, the sliding arc length required to produce a unit deflection angle is much larger than the displacement required in traditional lateral translation schemes. Taking the refractive index n (632.8nm) = 1.515 of N-BK7 glass material and R = 20mm as an example, to correct an angular deviation of 0.1° (about 1.75mrad), the sliding arc length As = R·0 / (n-1) = 20mm x 1.75mrad x 0.515 = 18.025 microns is required. Obviously, the above sliding arc length and the output beam deflection angle form a magnification relationship, so that the macro-scale sliding amount can realize the micro-scale beam angle adjustment. The above sliding arc length is much larger than the displacement required in traditional schemes, and the physical displacement required by the present application to produce the same deflection angle 0 is improved from Ad in the traditional scheme to As = R / ((n-1)·f)·Ad. This essential improvement liberates the displacement control from the "micron level" field which is difficult to stabilize to the "ten micron level" field which is easier to accurately control, reduces the adjustment sensitivity, greatly reduces the harsh requirements on the driving mechanism, and thus greatly reduces the adjustment difficulty. At the same time, the repeatability and reliability of the calibration process are improved. By adjusting the attitude of the plano-concave lens 104, errors caused by assembly or processing can be corrected.

[0053] In the actual assembly process, the optical fiber array 101 and the first microlens array 102 need to be accurately aligned on a precision alignment device first. The alignment process uses a special optical monitoring system to determine the alignment accuracy by observing the quality of the far-field spot. After alignment, a specific wavelength of ultraviolet light is used to irradiate the optical glue to solidify it and form a permanent and firm connection.

[0054] Next, the second microlens array 103 is installed, and special attention is needed to maintain the perpendicular relationship between its spherical surface and the system optical axis. During installation, an interferometer is used for real-time monitoring to ensure that the positioning accuracy of the spherical surface meets the design requirements. Finally, the plano-concave lens 104 group is installed, and preliminary positioning is performed without solidifying the optical glue to leave enough adjustment space for subsequent fine adjustment.

[0055] The calibration stage uses an automated test system to monitor the output beam quality of each channel in real time through a precise beam analysis device. According to the monitoring results, the system automatically calculates the displacement amount required for each plano-concave lens to adjust, and executes the corresponding adjustment operation through a precise driving mechanism. The adjustment process continuously monitors the changes in beam parameters until the output beams of all channels meet the preset quality standards.

[0056] After the adjustment, the optical cement is cured by UV light with specific parameters through a specially designed irradiation window, and the plano-concave lenses are permanently fixed in the optimal working position. Finally, the whole array is installed in a specially designed protective shell, which has a buffer structure and temperature compensation device inside to ensure the stable working performance of the array under various environmental conditions.

[0057] In addition to the basic embodiment described above, the present application can have various alternative embodiments. For example, for different application requirements, different channel number array configurations can be achieved by adjusting the arrangement density of the optical fibers and the size of the lenses. For special working wavebands, corresponding optical materials and coating schemes can be selected to optimize the transmission performance. In addition, according to the requirements of specific application scenarios, additional functions such as temperature control and shock protection can be integrated in the shell design.

[0058] The specific embodiments of the present application are described above, but those skilled in the art should understand that this is only an example, and those skilled in the art can make various changes or modifications to this embodiment without departing from the principles and essence of the present application. However, these changes and modifications all fall within the scope of the present application.

Claims

1. A two-dimensional array of easily adjustable beam pointing fiber collimators for easily adjustable beam pointing, characterized by: Comprising: a fiber array, in which a plurality of optical fibers are arranged in a two-dimensional matrix and fixed in a substrate; a first microlens array, fixed on the rear end surface of the fiber array, for collimating the light beams emitted by each optical fiber channel; a second microlens array, disposed behind the first microlens array, with a spherical surface having a uniform radius of curvature on its light-emitting side; a plurality of plano-concave lenses, arranged behind the second microlens array, each corresponding to an optical channel, and having a concave surface with a radius of curvature matching that of the spherical surface of the second microlens array, and forming a slidable bonding interface through a curable optical adhesive layer; wherein the plano-concave lenses can be adjusted by sliding along the spherical surface, and the deflection angle of the output light beam is controlled by controlling the sliding arc length of the plano-concave lenses.

2. A two-dimensional array of fiber collimators with easy beam pointing adjustment according to claim 1, characterized in that: The arc length Δs of the plano-concave lenses sliding along the spherical surface and the deflection angle θ of the output light beam satisfy: where R is the radius of curvature of the spherical surface, n is the refractive index of the material, and R is selected to be much larger than the focal length of the first microlens array, and a low refractive index material is selected to reduce the adjustment sensitivity.

3. A two-dimensional array of fiber collimators with easy beam pointing adjustment according to claim 2, characterized in that: The radius of curvature R of the spherical surface of the second microlens array and the focal length f of the lenses in the first microlens array satisfy: R ≥ 3f.

4. A two-dimensional fiber collimator array with easy beam pointing adjustment according to claim 1, characterized in that: The sliding of the plano-concave lenses is achieved by manual or high-precision driving mechanism.

5. A two-dimensional fiber collimator array for easy adjustment of beam pointing according to claim 1, characterized in that: The optical adhesive layer provides lubrication during adjustment and is fixed after adjustment is completed through solidification.

6. A two-dimensional fiber collimator array for easy adjustment of beam pointing according to claim 1, characterized in that: The matching tolerance of the radius of curvature of the plano-concave lenses and the second microlens array is less than 1%.

7. A two-dimensional fiber collimator array for easy adjustment of beam pointing according to claim 1, characterized in that: The sliding adjustment of the plano-concave lenses does not require additional precise guiding mechanism, and directly relies on the self-guiding of the spherical surface.

8. An optical communication system comprising a two-dimensional fiber collimator array with adjustable beam pointing according to any one of claims 1 to 7.

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