TWI232967B - Small mode-field fiber lens - Google Patents

Abstract

A fiber lens includes a graded-index lens, a single-mode fiber disposed at a first end of the graded-index lens, and a refractive lens having a hyperbolic or near-hyperbolic shape disposed at a second end of the graded-index lens to focus a beam from the single-mode fiber to a diffraction-limited spot.

Description

1232967 V. Description of the invention (1) 1. The technical field to which the present invention belongs and the present invention generally relate to optical devices for coupling optical signals between optical elements. More specifically, the present invention relates to a fiber lens to couple signals between optical elements. Where, the prior art ^ Various methods have been used in optical communications to couple optical elements such as optical fibers' recording and emitting optical signals between a diode and a semiconductor optical amplifier. One method uses a fiber optic lens, which is a piece of equipment having a lens placed on the tail lobe fiber-end. Light can enter or leave the door through the lens or tail lobe fiber. The fiber lens can focus the light emitted by the tail lobe fiber to; however, the first and last points are 4 points / and the required intensity is selected at the working distance. The distribution is limited to very small spot sizes with Λ to achieve the desired intensity distribution. For η: η distance θ simultaneously control the size and intensity of the point 〇 micro + the same day ^ / μ, people need to get the mode field diameter as small as 2.5 · 3 to light i ί, the above bulk or dielectric waveguide ... ^ its Demand distribution of fiber optic lenses with small mode field straight offenses / sentences that produce focal points. Tight… and the required intensity over a wide working distance. III. Summary of the invention Binomial position = rate lens. It includes-a refractive lens with a steep refractive index or a near hyperbolic shape. % Steepness refractive index lens second end page 5 1232967

= Optical fiber u ray "is a point of limited diffraction. In the aspect of transmission, the present invention relates to a fiber lens, which includes a single-mode fiber at the end of a single-mode optical fiber, where the waist of the beam is emitted from the end of the lens The core nuclei diameter is less than 10 microns and the ratio of the lens end to the beam huge distance to the mode field diameter at the beam waist is greater than 5. In aspects, the present invention relates to a method for manufacturing a fiber optic lens, which includes the + 2 If the optical fiber reaches the steep refractive index fiber, cut the steep refractive index fiber to 7 = required length, and round the end of the steep refractive index fiber to a curved or near hyperbolic shape. The invention relates to a method for manufacturing an optical fiber lens. The method includes splicing a single-mode fiber to a steep-index fiber, cutting the steep-index fiber to a required length, and splicing a coreless fiber to a steep-index fiber. Core fiber to the required length, and round the end of the coreless core fiber into a hyperbola or near hyperbola shape. Other characteristics and advantages of the present invention will be described in more detail in the following detailed description along with the following drawings Fourth, the embodiments The present invention will be described in detail for some embodiments, which are shown in the drawings. In the following description, a number of specific descriptions will provide a complete understanding of the present invention. Those skilled in the art who understand the present invention can These specific instructions are not required for implementation. In other cases, well-known processes and / or characteristics are not described in detail to avoid obscuring the invention. Refer to the drawings and the following detailed description The characteristics and advantages of the present invention will be better understood.

1232967 V. Description of the invention (3) The embodiment of the present invention provides the optical fiber through the focus at the required distance according to the application situation and focus on ^ and combine the light emitted by ^ fiber to create a long-term mirror using a refractive lens and steepness The shape of the index line of the refractive index group will be; = In the beam embodiment, the refractive lens has a retraction = In the example, the refractive lens has a near hyperbolic shape. First, it will be broad, by controlling the multi-mode parameters of the lens, and folding. In the past, it is enough to achieve small mode field diameters, such as in the range of 2 to 5 microns, and the Gaussian intensity distribution is one step further. At 15 one operation wave, it is sufficient to achieve long working distances of up to 25 to 40 microns. Maintain a small MFD and Gaussian intensity distribution. Figure 1A shows the fiber optic lens 100 of the present invention. The fiber optic lens 100 includes a steep refractive index (GRIN) 102, and the refractive lens 104 is located at the 102-end of the GRIN lens. And the single-mode tail lobe fiber 10 is located at the other end of the GRIN-fiber lens 1 02. The GRIN lens 102 has a core 108 with or without a cladding 11o limit. The core of the GR IN lens 1 〇2 1 08 has a refractive index profile preferentially, which The optical central axis of the fiber lens 100 increases radially with a square law or a hyperbolic distribution. In one embodiment, the refractive lens 104 is a hyperbolic lens with a hyperbolic surface 2 and a hyperbolic lens 1. The hyperbolic lens 1 〇 4 has a core 11 4 with or without a cladding 11 6 boundary. In theory the core 11 4 should have a uniform refractive index, but it is easier to become a hyperbolic surface 112 by polishing the end of the GRIN lens 102, which The central core 114 has a refractive index distribution, which increases radially toward the optical center axis of the fiber lens 100. The distribution formula of the hyperbolic lens 104 is:

Page 7 1232967 V. Explanation of the invention (4)-u2 / a2-v2 / b2 = 1 (la), Figure 1B is a graph of the above formula. In the graph, the hyperbolic lens 104 is a branch of the hyperbola on the u-v coordinate system, and the vertex of the hyperbola is located at (a, 0) of the u axis. The focal point of a hyperbola is (c, 0), where c is expressed by the following formula: c = (aHb2) 0 · 5 (lb) A hyperbola is included in two asymptote lines, which is expressed by the following formula: bu Soil av = 〇 (lc) ^

The asymptotic slope is + b / a and -b / a. The asymptote intersects the origin (〇〇) to form a wedge shape, and its apex angle is α, which is expressed by the following formula: 乂 adtairKb / a) (Id) According to Edwards et al., The ideal hyperbolic distribution accurately transforms the incident spherical wave It is a plane wave. In the formulas (la) to (ld), a is expressed by the following formula: a2 = [n2 / (ni + n2)] 2r22 (2a) b2 = [(-n2) / (+ n2)] r22 (2 b) where n! is the refractive index of the lens core of the graph, n2 is the refractive index of the light medium surrounding the hyperbolic lens, and r * 2 is the half of the curvature at the end of the hyperbolic lens

take off clothes. (Edwards, Christopher A., Presby, Herman M., and Dragone Corrado " Ideal Microlenses for Laser to Fiber Coupling, Journal of Lightwave Technology, Vol 11, No. 2, (1993): 352.). With hyperbolic distribution, the mode field radii are equal at planes (1) and (2) shown in Figure 1B, and the curvature radius is infinite at plane (2), that is, the wavefront of the beam at plane (2) Weiping

Page 8 1232967 V. Description of the invention (5) Generality. c〇reference = Α: Λ lobe fiber 106 can be any single-mode fiber, for example, corpse 8 # fiber, or a specific single-mode fiber, for example, to maintain polarization (PM female. Hairloin fiber 106 when viewed from the end) It can be circular symmetrical or octave, and its shape is, for example, square or oval. The GRIN lens 102 is preferentially connected to the tail lobe fiber 1G6. For reliability and long-term stability, the HGrin lens 104 can be directly formed on the GRIN lens丨 〇2 or formed on the centerless spacer rod connected to the GRIN lens 102. As shown in Figure κ, the hyperbolic lens 104 can also be connected to the GRIN lens 102. As shown in Figure lc, the hyperbolic lens 104 can also be connected to the centerless spacer element 12, which is connected to the GRIN lens 102. Since the final dimensions of the refractive lens and spacer element are usually quite small, it is preferred that the GR IN fiber or spacer element be longer The length is connected to the first tail lobe fiber and is cut or cut to the required length before the refractive lens is formed on the end. (The coreless spacer member can also be placed on the GRIN lens 102 and the tail lobe fiber. 〇〇6 Between.) Hyperbola The mirror 104 can be formed by forming a section of a fiber into a conical / wedge shape, which has a vertex angle (α in FIG. 1B). For example, the optical fiber can be shaped into a conical / wedge shape, which uses a tapered cutting process (symmetrical ) Or laser micromachining and polishing. Curvature can be formed at the conical / wedge-shaped end to produce the desired distribution. Although not shown in the drawings, GR IN lens and / or single-mode tail lobe fiber It can be gradually changed. The overall diameter of the tail lobe fiber can be less than or substantially equal to the overall diameter of the GRIN lens. The GRIN lens 102 and the hyperbolic lens 104 produce a small mode field diameter (MFD) focused beam, good wavefront characteristics, and long work Distance

Page 9 1232967 V. Description of the invention (6)

In the embodiment, the following attributes are required ... The mode field diameter (mfd) at the waist of the beam is t at 10 microns, preferably in the range of 2 to 5 microns, with a reasonable Gaussian strength. The cutting cloth 'working distance is greater than 5 microns , Preferably in the range of 20 to ⑼ micrometers, the ratio of the distance from the lens end to the beam waist to the mode field diameter at the beam waist is greater than 5, and the lens-to-lens operating wavelength range is 250 to 2000 nm Consumption efficiency is greater than 65%. Both the hyperbolic lens 104 and the GRIN lens 102 are important to achieve a small mode field diameter and a long working distance. For example, if the GRIN lens 102 is not used, the size of the light spot at the end of the hyperbolic lens 104 is limited to the MFD of the single-mode tail lobe fiber 〇06, which will limit the available working distance to a relatively small value. For example, the mode field diameter of the most practical single-mode fiber at an operating wavelength of 550 nm is in the range of 10-2 microns. For a single-mode fiber with a MFD of 0 μm and a divergence angle of 38 μm, a 3 μm focusing MF is required]). If only a hyperbolic lens is used, the maximum working distance is limited to 4 μm. In order to further show the importance of using hyperbolic lens 104 and GRIN lens 102, refer to FIG. 2A, which shows that the radius of curvature at the end of the hyperbolic lens is a function of the working distance of the fiber lens. Single-mode tail-lobe fibers do not include ⑽ 丨 N lenses at the ends. The attached figure shows that this fiber lens has good wavefront characteristics. Figure 2B shows

The MFD change at the end of the curved lens is a function of the working distance of the example shown in FIG. 2A. The figure shows that the focused MFD is in the range of 2.0-3.5 micrometers, and the MFD must be greater than 10 micrometers at the end of the curvature = lens to achieve a working distance of two to 20 micrometers. Unless the GRIN lens is placed between the hyperbolic lens and the single-mode tail lobe, ordinary single-mode optical fibers will not be able to achieve a working distance much greater than 20 micrometers because the MFD at the end of the hyperbolic lens will not be limited to the index ρ JI And π early-mode taillobe fibers

1232967 V. MFD of invention description (7). Figure 3 shows the light beam 300 propagating through the planes u), (2), (3), and (4). The plane (1) includes the end surface of the optical device 302. The plane (2) coincides with the end of the fiber lens 304. The plane (3) coincides with the interface between the hyperbolic lens 306 and the steep refractive index lens 308. Plane (4) contains the end surface of single-mode taillobe fiber 310. It is assumed that the optical device 30 (iMFI) is equal to 2w0 and is located at a distance d from the end of the fiber lens 300. In this case, it is necessary to design the fiber lens 304 so that the focal point size of the fiber lens 304 at the distance d from the end of the fiber lens 300 at the operating wavelength 8 is as close to 2wG as possible. The beam characteristics at the end of the GRIN lens 308 and the 306 characteristics of the hyperbolic lens determine the beam size characteristics of the focused beam. In one embodiment, the process of designing the fiber lens 304 includes (1) calculating the radius of curvature and the required mode field at the end of the fiber lens 304 to generate the focal spot size, and (2) using the calculated radius of curvature to determine the double The distribution of the curve lens 306, and (3)) use the calculated mode field and the tail lobe fiber 3 10 mode field to determine the GR IN lens parameters. The following describes possible ways to implement this process. For step (1), the mode field radius (w) and the curvature radius (r2) at the plane (2), that is, at the end of the fiber lens 304, can be determined using the known formula for Gaussian beam propagation. For example, Edwards and others proposed the following formulas for w2 and r2: w2 = w〇 [l + (λά) 2 / (ttw0) 2] 0 · 5 (2a) r2 = (π / λ) 2 (w〇w2) 2 / d (2b) For step (2), the radius of curvature (r2) given by formulas (2a) and (2b) and formulas (la)-(id) can be used to determine the hyperbolic lens 306 distribution.

Page 11 1232967

For step (3), the GRIN lens 308 converts a light beam with a mode field radius w, 3 and a curvature radius of 5 at the plane (3) into a light beam with a mode field radius W4 and a curvature radius at the plane (4). As an optimal design,% needs to be as close as possible to the mode field radius% of single mode tail lobe fiber 31. One way to achieve this optimal design is to choose a special single-mode tail-lobe fiber such that it is equal to '308% of the available GRiy lens. Alternatively, the number of wheats of the GRIN lens 308 can be selected so that% is as close to a specific Wp value as possible. In this case, a standard single-mode fiber such as a Corning SMF-28 fiber can be used as the tail lobe fiber. (^ IN lens parameters include core diameter, outer diameter (cladding diameter), refractive index, refractive index difference between core and cladding, and GRIN lens length. In the embodiment described above, the GR IN lens core The diameter is in the range of 500 to 500 microns, and the outer diameter is in the range of 60 to 1000 microns. Spliced to the relative refractive index difference in the high silica component matching the optical fiber used in the optical communication system It is optimally in the range of 0.5 to 3%. Yan, for the case of hyperbolic lenses, where rs = 〇〇, that is, the beam is a plane wavefront at plane (3), and ws = W2, GRIN lens 30 8 is simple in length In this case, the mode field radius% and ^ are related to the ⑶ 丨 N lens parameters, and their relationship is as follows: · w3 · w4 = λ / (redundant ng) (3 a) where g = ( 2 △ YVa (3b) where g is the focus parameter, a is the core radius of the GRIN lens, and △ is the relative refractive index difference between the cladding and the core of the grin lens. L · 4 = (7Γ · a) / [2 · (2 △ ju) (3c) where △ = (< 一 n22) / (2 · Πι2) (3d) where L is between Distance, r is the refractive index of the lens core,% gGRIN lens 1232967

Refractive index of the cladding. For non-quarter-pitch GRIN lenses, Gaussian beam transitions can be calculated by Emkey's expert developed the ABCD matrix processing method (Emkey, wiiiiam L. and Jack, Curtis A., Analysis and Evaluation of

Grades-Index Fiber Lenses " Journal of Lightwave

Technology, Vol. LT-5, No. 9, (1987): 1156-1164). This method uses a complex beam parameter ‘’ q ”, which is defined as follows: l / q (z) = l / r (z)-i λ / (7Γ w1 2 (z) n) (4a)

Where r is the curvature radius of the Gaussian beam, w is the mode field radius, λ is the free-space wavelength, and η is the refractive index. q (z) is changed from the plane (4) containing the end surface of the single-mode tail lobe fiber 31 ° to the plane (1) of the end surface of the single-mode tail lobe fiber 30 1 containing the final beam waist of the fiber lens 30, which It is expressed by the following formula: q1i: :( Aq4 + B) / (Cq4 + D) (4b) where 屮 and 1 are the complex beam parameters at planes (1) and (4), respectively. Items A, B, C, and D are the beam matrix elements related to the light parameters of the plane (4) to plane (1) and are obtained by the following formulas: ^ A Bn ~ C DJ = from M2M3M4 (5a)

Among them, the transformation and expression of the light parameters between the plane (1) and the plane (2) are as follows:

Page 13 1 〇 1 1 (5b) 2 where z is the final beam waist relative to the end of the hyperbolic lens. M2 is the light parameter transition in the hyperbolic lens and is expressed as follows: 1232967 V. Description of the invention (10) r 1 〇 ^ M2 = L- (n2-n!) /! ^ Ni / n2 J (5c)

Mg is the transformation of the light parameters in the GRIN lens and is expressed as follows, cos (gL) sin (gL) / gl M3 = [-gsin (gL) cos (gL) J (5c) where g is the formula for the length of the GRIN lens L (3b) and the refractive index profile are: n '(r) = n (l-g2r2) 0.5 (5d) where r is the radial position from the central axis of the lens.牝 is the transformation of the light parameter from the refractive index medium to the plane (4) ^ and is expressed as follows: Γ 1 0 1 '· Μ4 = I 0 ^ / nj (5e) GR IN lens focus tea number g and length B can It is adjusted so that in plane (4), the mode u field radius W4 is transformed as close as possible to the mode field radius% of the single-mode tail lobe fiber after the beam passes through the grin lens. The hyperbolic lens focuses the collimated beam on the spot of limited diffraction, but it cannot focus the non-collimated beam on the spot of limited diffraction because it cannot make the beam paths of all rays equal at one point. For a GRIN lens with a quarter pitch, the beam at the output surface of the GRIN lens is collimated. Therefore, if a hyperbolic lens is connected to a quarter pitch GRIN lens, the light beam emitted by the tail lobe fiber will be focused to a point of limited diffraction. For GRIN lenses without a quarter pitch, the f at the end of the GRIN lens will diverge or converge, depending on whether the length of the GRIN lens is shorter or longer than a quarter pitch. Therefore, the lens is preferentially designed to be close to: minute 1232967 V. One of the pitches of invention description (11). It is known that there are some applications for GRIN lenses with non-quarter pitch. For these applications, we provide close Hyperbolic lens, which can focus non-collimated light beams to the point of limited diffraction. Table 1 below shows the radius of curvature (R) and MFD of the output beam as a function of the length (z) of the GRIN transmission f. The parameters used are: · the radii of the heart core, the relative refractive index difference of 82, 0.01, the operating wavelength λ = 1 550 ηη, and the mode field radius of the early core tail lobe fiber 丨 0.6 microns. Table 1 ζ (mm) 0.15 16 17 18 19 21 22 23 24 25 26 27 0.2776 MFD (micron) 9. 544436065 9.880469672 1 0. 1 9 672 1 03 10.49111006 10. 76181305 11. 00723608 11.22599466 11.41689802 11.57893731 11.7112765 11.81324573 11.88433631 11. 92419729 11. 9334793 R (mm ) 0.276522 0.302607 0.333614 0.370933 0.416623 0.473827 0.547572 0.646393 0.786001 0.99881 1.364093 2.140502 4.933849 472. 7168

Page 15 1232967 0 · 28 0 · 29 0 · 30 0 · 31 0 · 32 0. 33 0 · 34 0 · 35 0 · 36 0 · 37 0 · 38 0 · 39 〇 · 4 V. Description of the invention (⑵ 11 93233319 -16 3388 11. 90960273 -3. 07433 11.85521866 -1.69397 11. 76974837 -1 · 16665 11. 65361566 -0.88767 11. 50740347 -0.71467 11. 33185804 -0.59666 11.12789463 -0.51087 10. 89660521 -0.44559 10. 63926875- 0.39422 10.3573647 -0.35272 10. 05259072 -0. 31854 9.726885718 -0.28996 (for the design shown in Table 1, the distance between the steep refractive indices is approximately 1 π um 1 or 1.11 mm). Using the formula (3 C), the quarter pitch is approximately 2 7 7 • 6 U meters (or 0.27 7 6 mm). For GR lens lengths close to a quarter of the distance, N is very large. For GRIN lens lengths below a quarter pitch, R is the divergence. For example, for a GRIN lens length of 26 μm, R is approximately 2.14 mm. For GRIN lens lengths greater than a quarter pitch lens, R is convergent. For example, for a GRIN lens length of 29 microns, R is approximately -3.07 mm. The approximate hyperbolic shape of the modified hyperbolic shape where R is a converging or diverging lens length with a correction coefficient is needed to achieve a limited diffractive focused spot, and the correction coefficient will compensate the beam curvature. Near hyperbolic lens distribution can be calculated by optical and physical path length

1232967 V. Description of the invention (13) The degree k is determined to have reasonable accuracy, which needs to change the hyperbolic distribution to compensate for the curvature of the beam of the member. Figure 4 A shows the plane beam wavefront 400 and the divergent beam wavefront 402. If the GRIN lens length is at or near a quarter pitch, the plane beam wavefront will be generated. If the GRIN lens length is shorter than a quarter pitch A divergent beam wavefront will be generated. Compared with the optical path of the plane beam wavefront 400, the optical path of the divergent beam wavefront 402 decreases from the optical center axis. The optical path length difference LQpt (r) is a function of the radial distance from the optical center axis, which can be determined using the following formula: L〇pt t (r) (1-cos φ) (6a)

Where P rsirr1 (r / R) (6b) The difference in physical path length Lp (r) is expressed by the following formula:

Lp (r) = Lopt (r) / (n-l) (6c)

ϊ: 11 is the refractive index of the lens material. In a similar form, the near-hyperbolic shape of the GRIN lens I pitch is the wavefront interception of the focused beam. In the case of Red 5 ', the difference in the optical path length needs to be increased as a function of the medium: t distance. Figure 4β shows that the shape of the hyperbola is bundled. Second, it is close to the hyperbola shape 408, which can focus the divergent wave just to the point of limited diffraction.

The length of the mirror is 2QG microns and the radius of curvature is 473.8. Hyperbolic 唆: η Deviation from the radial position function of the optical center axis Hyperbolic optical path lengths are listed in Table 2. Table 2 Γ (microns) L. # 2 0.004228

1232967 V. Description of the invention (14) 4 6 8 10 12 14 16 18 20 22 0 · 016913 ° · 038054 0.067652 0.105704 ° · 152212 ° · 207173 ° · 270587 0.342453 0.42277 ° · 511536 The difference between the physical shuttle length and the optical path length Divided by (n — 丨), the second refractive index is the refractive index of the lens material. As shown in Table 2, for a large half-curvature, the change in the shape of the hyperbola with a small distance from the optical center axis is quite not equal to = a small radius of curvature, and the deviation from the optical center axis becomes large: the calculations shown above show that Determine the approximate hyperbolic shape :::: r Use approximate lens design simulation to approximate the hyperbolic shape = 洚 5〒 This book shows that each -grin spacing used in fiber optic lenses when needed is different. Thus, N lenses can be used in accordance with the present invention for use in various applications. Since the refractive index of the germ germ does not need to be changed, the process of manufacturing the germ germ treated GRI N lens can be simplified. Therefore, it can be used as an application of different mode transformations. The hair embryos are preferentially drawn from the same hair embryos for different applications, and formed to different diameters.

1232967 --- Eight ^ to meet the specifications of different applications. GR1N parameters such as GR1N lens with four pitches of GR IN lens parameters can use the previously described processing steps. In the present invention, the close hyperbolic lens to remove the GRIN lens must be &: spacing to achieve the limit of limited diffraction light points. . Close to hyperbola = the labor force of combining a hyperbolic lens and a spherical lens to correct the residual curvature 6. In a non-limiting example, the use of Corning SMF-28 fiber is a single-mode taillobe fiber. The tail lobe fiber is spliced to one end of the GRIN lens, and close to the hyperbolic lens is formed on the other end of the GRIN lens. The distance between the end of the hyperbolic lens and the stitching is approximately 275 microns. The GRIN lens has a core diameter of 50 μm and an outer diameter of 25 μm. The difference between the refractive index of the gr I n lens core and the cladding is 1%. Figure 5 shows the far-field intensity profile as a function of the far-field divergence angle of this example. The characteristics are achieved at ^^ μm, and the divergence angle of the half-maximum value (FWHM) of the full field width of the fiber lens is about 20 degrees. The graph shows that the intensity is Gaussian. One application of the optical fiber lens of the present invention is the coupling of signals between optical fibers and semiconductor optical amplifiers (S 0 A) or other waveguides. The general specifications for these applications include: MFD < 3.0 microns, distance to the beam waist greater than 10 microns, foldback loss > 4 5 d B, and strong lens shape to prevent components from cracking during assembly. For S 0 A waveguide applications, fiber optic lenses must transform the tail lobe fiber mode field to match the S 0A waveguide mode field. The number of soa devices under consideration and the waveguide have normal MFD are currently considered. The MFD of SOA at 1550nm is in the range of 2.5-3.8 microns. This value corresponds to a maximum divergence angle of up to 18-22 degrees at half the full width of the far field. Far-field divergence at approximately 13.5% (l / e2) intensity value

Page 19 1232967 V. Description of the invention (16) --- The half angle is expressed by the following formula: Q-乂 1, π ', (7) where is the wavelength of the light and Wg is the beam mode field half chirp. Is 2%. Another attribute that has an effect on the SOA assembly process and the characteristics required for fiber optic lenses is the small facet of SOA with an angle. In order to reduce the reflection from ^ to ^, the angle of formation of the facet of the SOA is approximately 5 degrees. The gap between the small facet with an angle and the edge of the small facet and the end of the lens is reasonable. Otherwise, when the fiber lens is aligned with SOA for optimal lightening, the possibility of the fiber lens contacting the small facet of SpA will be increased and destroyed. At present, most of the available MFDs in the range of 2 · 5-3 · 8 microns at ^ ⑼ · red operating wavelengths have working distances as small as 5-10 microns. Therefore, working distances greater than 20 microns are beneficial to improve their properties and reduce the possibility of damaging SOA during assembly. At the same time, SOA is very sensitive to backward reflection. If the working distance is relatively large, a small part of the back reflection from the end of the fiber lens will reach the outline. This will improve the performance and stability of SOA. … Shooting a SOA should use another characteristic for the intensity distribution and the wavefront characteristics of the two lines focused by the fiber lens. The wavefront characteristics should match the mode f intensity distribution between the SOA and the tail lobe fiber, and their size, intensity distribution, and phase should be as close as possible to each other. This means that the focused light emitted by the tail lobe fiber via the fiber lens is j-sized in the range of 2. 5-3. 8 microns and as Gaussian as possible. The objective is to use fiber optic lenses to achieve this characteristic at larger MF]), but not so good at smaller MFI). This results in higher coupling losses and worsens SOA performance. It is beneficial to improve this performance. Another property is the robustness of fiber optic lenses. For example, if the fiber optic lens is not designed to make JL and die, there are non-hanging small and weak ends, including the preparation

1232967 V. Description of the invention (17) During the various processing steps of assembling the lens into the package of SOA, the fiber end of the lens can actually strengthen the light, which is not fragile. It will be a useful attribute. Another useful property is that the lens design process is stable and has a large error in the process. For example, the curvature radius of the lens end is 10 micrometers, a very small change in the radius of curvature, etc. produces a 10% change and significantly changes the focusing characteristics. The same micron variation in a 25-radius design is not quite performance-intensive. In the present invention, some of these problems will be solved and improved. Another application of the optical fiber lens of the present invention is the coupling between the optical fiber and the laser diode. Laser diodes used as transmission lasers have a pass-field divergence angle of up to 40 degrees, which corresponds to MFDg 0.8 microns at a wavelength of 1550 nm. The aspect ratio of the laser rays in the X and y directions is between 4 and 4. The more matching the lens feet, the higher the coupling efficiency. In the present invention, the optical fiber lens is usually moved to the device by gears 5 so that its aspect ratio approaches 1. The distance to the waist of the beam is greater than 0. Meters are needed because they will prevent damage to the lens during assembly. The preferred characteristics of fiber optic lenses for this application are as follows: MFD <3.0 micron or divergence angle greater than 22 degrees, foldback loss &gt; 45dB, beam waist distance &gt; 10 micron, and lens-to-lens coupling efficiency at 550 ° Is more than 90%. Another application of the optical fiber lens of the present invention is to combine signals through optical fibers and sensing signals. Unlike the above applications, where not only the spot size is also strong, the knife cloth X and the phase wave are differentially related. Sensor applications need to control the spot size and power to a certain specific range. For this application, light sizes smaller than 3-5 and working distances as high as 50-60 microns will benefit low-cost components. 1232967, description of the invention (18) The fiber optic lens of the present invention provides one or more advantages. Fiber Optic &amp; Coupling signals between optical devices. Compared with the graded lens, the hyperbolic lens formed at the end of the fiber lens or near the hyperbolic lens is mechanically solid and less susceptible to damage and performance degradation. The “透” number and the shape of the hyperbolic or near-hyperbolic lens can be changed; = FD and a reasonable Gaussian intensity pattern and a long working distance ^ The mirror will correct the non-collimated light; ί :: diffracted light spot. It is close to the hyperbolic transmission limit diffraction light point. The wave of the beam has a curvature 'which can focus the light beam. Although the present invention has been described for several changes, variations, and equivalent examples of each embodiment, the scope of these actual patent applications includes all These 3 belong to the scope of the present invention. The following are within the spirit and scope of the present invention: text, changes, and equivalents, which belong to 1232967. A brief description of the drawings ~ V. The drawings briefly illustrate the present invention through non-limiting examples. The following The drawings enumerate that the same reference numerals in the drawings indicate the same components, and the first diagram A is a schematic diagram of an embodiment of the optical fiber lens of the present invention. The first diagram B is a geometric diagram of hyperbolic transmission. The first diagram C shows A fiber optic lens with a coreless spacer is placed between the GRIN lens and the refractive index lens. The second graph A is the curve of the curvature radius at the end of the hyperbolic lens as a function of working distance. In this case, the hyperbolic lens is placed at the end of the single-mode tail lobe fiber. The second graph B shows that the change in the mode field diameter at the end of the hyperbolic lens is a function of the working distance of the example shown in Fig. A. 苐 二The figure is a schematic diagram of light propagating through the optical fiber lens of the present invention. The fourth figure A is a geometric representation of the wavefront of a planar beam and the wavefront of a divergent beam. The fourth figure B is a variation of the shape of a hyperbola to form a hyperbolic lens. It is intended that the fifth figure is a graph of the far-field intensity distribution of the optical fiber lens according to the embodiment of the present invention as a function of the far-field divergence angle. 〇4; tail lobe fiber 106; heart core 108; cladding 11 〇; hyperbolic surface 112, core 114; cladding 116; plane 118; light beam 300; optical device 3021 fiber lens 304; Hyperbolic lens 306; steep index of refraction read in 卞 inspection mirror 3 0 8; tail lobe

1232967 Simple illustration of the optical fiber 310; plane wavefront 400; divergent beam wavefront 402; optical axis 404; hyperbolic shape 40 6; near hyperbolic shape 4 08.

Claims (1)

1232967 VI. Patent application scope 1. A fiber optic lens including: a steepness refractive index lens at the first end of the steepness refractive index; and a second end of the refractive index at the steepness 2 quasi ==:; :: Item 2 of the lens, in which the shape will focus on the point of finite diffraction to compensate for the first beam curvature and make the non-collimated beam 4 ^ ^ ttin ^ (^ t fs ^ ^ # ^ ^ lens, where the interval _ put 6 == 2ΪΓ:] The fiber lens of the first item in the range, in which the mode field diameter of the light spot is around the fiber transmission of the sixth item ... The mode field of the light spot is straight = ::; 5: Fan Mi Wai. The fiber transmission of the sixth item is … 19 of the fiber optic lens is used as the optical fiber in item 6 of the patent scope, and the protective distance of the medium fiber optic lens is in the range of 20 to 60 microns. Refractive optical fiber, page 25, 1232967 Six patent applications. The distance between the lens end and the beam waist is greater than 5. 19. The ratio of the mode field diameter at nine beam waists ° 11. According to the patent application scope, the lens core diameter In the range of 50 to 500 microns. Refractive index of medium steepness 1 2. According to the scope of patent application No. 6 lens outer diameter In the range of 60 to 1000 micrometers, the refractive index of '., Brother' &quot; medium steepness &quot; 1 3. According to the fiber optic lens of the patent application scope, the relative refractive index difference of the lens is between (35 to 3 Within the range of%. &Amp; Degree of refractive index 1 4 According to the scope of application patent scope, the optical fiber transmission wavelength is within the range of 250 to 200 nm. T optical sense lens 刼 15 · — a kind of fiber lens, which includes. · Single mode Optical fiber; and the lens is placed at the end of the single-mode fiber, where the light beam emitted by the lens end is 10 microns and the ratio of the lens end to the beam diameter is greater than 5. The mode field diameter at the waist of the beam is less than the waist distance Mode field at the waist of the beam 16 · According to the fiber optic lens according to item 5 of the scope of the patent application, the lens is composed of a chirped or near hyperbolic lens, and the lens is placed at the end of the steep-fold lens. H. The fiber optic lens according to item 16 of the scope of the patent application, wherein the spacer is placed between a hyperbolic or near hyperbolic lens and a steep refractive index lens. 18. A method for manufacturing a fiber optic lens, which includes: splicing a single-mode optical fiber to Steep-index fiber; Cut the steep-index fiber to the required length; Page 26 1232967 Application for patent scope 1 The shape of the steep refractive index duo #H H shape into a hyperbola or close to a hyperbolic hexagon 1 9, according to the patent application scope 丨 8 vertical gradient refractive index fiber end circle Shape method, ^ 甲 更 进 —steps included in the round zirconium quasi-seven spider π * the beauty of the gradient will be steeper refractive index 0 cone or wedge shape, its apex angle is formed from the hyperbolic apriori to 20. The method of fiber optic lens, springs out gradually. Splice single-mode fiber to steep refractive index ^ 2. 3. Cut the steep-index fiber to the required refractive index. Rounded into a hyperbola or near hyperbola shape. Page 27