557378 五、發明說明（1) 相關申請案： 本發明依據200 1年6月15月申請之美國第60/298, 841 號專利申請案，該專利名稱為” Thermal ly Formed Lensed Fibers For Imaging And Condenser Application” 以及 2002年1月29日申請之美國第60/35 2, 735號專利申請案，該 專利發明名稱為’’Tapered Lensed Fiber For Focusing And Condenser Application” 主張優先權。 發明背景： 1 ·發明領域： 本發明係關於光學通訊網路中透鏡化光纖以傳輸以及 收集光線。更特別地，本發明係關於漸變透鏡化光纖作為 I焦及聚光應用以及形成漸變透鏡化光纖之方法。 2·發明背景： 本發 鏡化光纖 纖透鏡對 及其能夠 一個溫度 匹配以達 為製造陣 光纖對準 工作距離 以及工作 能夠使用 為有益 準以及 促使組 範圍内 成較佳 列化裝 於平面 月包夠對 距離能 於光學 於單體裝置，其終端具有透鏡之光纖。透 的，因為其容易組裝，即其並不需要主動光 將光纖黏接至透鏡，其具有低插入損耗，以 件精緻化，因為其能夠製造為非常小。在 透鏡熱膨脹係數能夠與光纖熱膨脹係數相 的性能。透鏡化光纖容易地組列以及因而 置所需要，例如在矽光學載台應用作為將 波導等。除此，透鏡化光纖之點尺寸以及 特定應用特別地加以設計。例如，點尺寸 夠特別加以設計以產生較小光束直徑，其 切換器中較小的微-電-機械系統（ME。557378 5. Description of the invention (1) Related applications: The present invention is based on US Patent Application No. 60 / 298,841, filed on June 15, 2001, and the patent name is "Thermally ly Formed Lensed Fibers For Imaging And Condenser" Application "and US Patent Application No. 60/35 2, 735, filed on January 29, 2002, the invention name of the patent is" Tapered Lensed Fiber For Focusing And Condenser Application "Claiming priority. Background of the Invention: 1 · Invention Field: The present invention relates to lensed optical fibers in optical communication networks for transmission and collection of light. More particularly, the present invention relates to progressive lensed optical fibers as I-focus and focusing applications and methods for forming progressive lensed optical fibers. 2. Invention Background: The mirror fiber optic fiber lens pair and its temperature matching can be used to make the array fiber alignment working distance and work can be used as a guideline, and it is better to arrange the range of the group into a flat moon bag. It can be used in optical and single device, and its terminal has optical fiber with lens. It is transparent because it is easy to group. It means that it does not require active light to bond the optical fiber to the lens. It has low insertion loss and is refined because it can be made very small. The performance of the lens thermal expansion coefficient can be matched with that of the optical fiber. Lensization Optical fibers are easily aligned and required, for example, in silicon optical stage applications as waveguides, etc. In addition, the point size of lensed fibers and specific applications are specifically designed. For example, the point size is specifically designed to produce Smaller beam diameter, smaller micro-electro-mechanical system (ME) in its switcher.
557378 五、發明說明（2) 存在三種主要形式之透鏡光纖，其包含準直透鏡化光 纖，聚焦透鏡化光纖，及漸變透鏡化光纖。圖1顯示出先前 技術準直透鏡化光纖20,其具有平凸透鏡22融合拼接至光 纖24之一個端部。光纖24能夠為單模或多模光纖。在圖中 ，光纖24為單模光纖。平凸透鏡22由無心蕊光纖所構成，以 及透鏡22前端表面成形為球面狀。透鏡22之球面通常藉由 使用電弧或雷射光束熔融無心蕊光纖形成。透鏡22之球面 作為準直器，將離開光纖24光線擴展為準直光束。實際上 使用透鏡化光纖20以耦合一條光纖發出光線至另外一條。 /圖2A顯示先前技術聚焦透鏡化光纖26，其具有第一平 方律折射率光纖28融合拼接至單模光纖3〇之一端。第二 平方律折射率光纖32連接至第一平方律光纖28。作為 ^鏡之凸面能夠提供於第二平方律折射率光纖32之遠端 :通常’凸面34之曲率半徑小於準直透鏡化光纖透鏡之 ，率（參閱則透鏡22)。聚线鏡化光纖26將光線聚 =:及使用作為聚焦用，例如將光束聚焦於感測器或接 杰上以及耦合雷射光源發出光線至光纖。 ㈣存Ϊ各種方法以提供凸面34於第二平方律折射率光 、’、。第,：端。一種方法包含熔融遠端36以形成半球形表面 於κι二士 Ϊ包含化學性地蝕刻遠端36以形成凸面34。顯示 析紛东中第三方法包含炼融拼接無心蕊光纖38至第二定理 玫开:：光纖32之遠端36以及再熔融無心蕊光纖38以形成半 球形表面。熔融通常依靠電弧。 乂成丰 圖3顯示出先前技術漸變透鏡化光纖4〇，其具有漸變段557378 V. Description of the invention (2) There are three main types of lens fiber, including collimated lensed fiber, focused lensed fiber, and graded lensed fiber. Fig. 1 shows a prior art collimated lensed optical fiber 20 having a plano-convex lens 22 fused to one end of an optical fiber 24. The optical fiber 24 can be a single-mode or multi-mode fiber. In the figure, the optical fiber 24 is a single-mode optical fiber. The plano-convex lens 22 is composed of a coreless optical fiber, and the front end surface of the lens 22 is formed into a spherical shape. The spherical surface of the lens 22 is typically formed by fusing a coreless fiber using an arc or laser beam. The spherical surface of the lens 22 acts as a collimator, and expands the light leaving the optical fiber 24 into a collimated beam. The lensed optical fiber 20 is actually used to couple light from one fiber to the other. / FIG. 2A shows a prior art focusing lensed optical fiber 26 having a first square-refractive-index optical fiber 28 fused and spliced to one end of a single-mode optical fiber 30. The second square law optical fiber 32 is connected to the first square law optical fiber 28. The convex surface of the mirror can be provided at the far end of the second square law refractive index fiber 32: usually the convex surface 34 has a radius of curvature smaller than that of the collimated lensed fiber lens (see lens 22). The condensing mirrored optical fiber 26 focuses light and uses it for focusing, for example, focusing a light beam on a sensor or a connector and coupling a laser light source to emit light to the optical fiber. Various methods are used to provide the convex surface 34 to the second square law refractive index light, ',. Article: end. One method includes melting the distal end 36 to form a hemispherical surface. The process of chemically etching the distal end 36 to form a convex surface 34. The third method of analysis and analysis involves melting and splicing the coreless fiber 38 to the second theorem. Open :: the distal end 36 of the optical fiber 32 and remelting the coreless fiber 38 to form a hemispherical surface. Melting usually relies on electric arcs. Tong Chengfeng Figure 3 shows the prior art graded lensed optical fiber 40, which has a graded section
557378557378
五、發明說明（3) 42形成於單模光纖44之端部。漸變段42具有作為透鏡之凸 面46。漸變段42能夠藉由研磨及/或拋光單模光纖44之端 部而達成。漸變之透鏡化光纖在短的工作距離範圍内將光 線準直。漸變化透鏡化光纖能夠使用作為將光線輕合於光 纖及雷射光源或光學放大器或平面波導之間。 口' 發明大要： 本發明一項係關於漸變之透鏡化光纖，其包含具有梯 度折射率心蕊之漸變化多模光纖以及光纖連接至漸變化多 模光纖。 本發明另外一項係關於一種形成透鏡化光纖之方法 其包含連接光纖至具有梯度折射率心蕊之多模光纖，施加 熱量至多模光纖之表面，以及拉引多模光纖為漸變段。 、本發明另外一項係關於一種形成漸變保持偏極光纖之 f法，該光纖包含連接保持偏極光纖至具有梯度折射率心 蕊之多模光纖，施加熱量至多模光纖之表面，以及拉引多模 光纖為漸變段。 本發明另外—項係關於一種漸變之保持偏極光纖，該 =^有梯度折射率心蕊之漸變多模光纖以及保持偏極光 纖連接至漸變多模光纖。 翩相ί發明其他特性及優點將由下列說明及申請專利範圍 顯現出。 詳細說明： ^發明實施例提供漸變透鏡化光纖作為聚焦以及聚^ σ 以及種製造漸變透鏡化光纖之方法。通常，漸變V. Description of the Invention (3) 42 is formed at the end of the single-mode optical fiber 44. The gradation section 42 has a convex surface 46 as a lens. The graded section 42 can be achieved by grinding and / or polishing the end of the single-mode optical fiber 44. The graded lensed fiber collimates the light over a short working distance. The graded lensed optical fiber can be used to light-shine light between an optical fiber and a laser light source or an optical amplifier or a planar waveguide. The main points of the invention: One aspect of the present invention relates to a graded lensed optical fiber, which comprises a graded multimode fiber having a gradient index core and an optical fiber connected to the graded multimode fiber. Another aspect of the present invention relates to a method for forming a lensed optical fiber, which includes connecting an optical fiber to a multimode optical fiber having a gradient index core, applying heat to a surface of the multimode optical fiber, and drawing the multimode optical fiber into a graded section. 2. Another aspect of the present invention relates to an f method for forming a gradient-maintaining polarized fiber. The fiber comprises connecting the polarization-maintaining fiber to a multimode fiber with a gradient index core, applying heat to the surface of the multimode fiber, and pulling. Multimode fiber is a graded section. The other aspect of the present invention relates to a graded maintaining polarized fiber, which is a graded multimode fiber with a gradient index core and a poled maintaining fiber connected to the graded multimode fiber. Other features and advantages of the invention will be apparent from the following description and the scope of patent applications. Detailed description: The embodiment of the invention provides a progressive lensed optical fiber for focusing and focusing, and a method for manufacturing a progressive lensed optical fiber. Usually, the gradient
557378 五、發明說明（4) 透鏡化光纖包含多模光纖拼接至任何單模光纖，其保持偏 極（PM)光纖。保持偏極光纖只傳播一個偏極。多模且 有梯度折射率（GRIN)心蕊，即心蕊折射率依據預先決定分、 佈變化。拉引多模光纖以產生漸變段。通常拉引處理過程 藉由加熱多模光纖而達成。漸變光纖之透鏡效應來自於 變段中折射以及梯度折射率。因而，在特定應用中特別設 2透鏡化光纖之發散角度以及模場直徑更具彈性，其最終 ★致_改σ耦口效率。本發明方法能夠使漸變透鏡化光纖形 成，同時維持保持偏極光纖之偏極隔離特性以及應力桿件 。本發明特定實施例針對底下附圖加以說明。 W 示丄依據本發明一項實施例之漸變透鏡化光纖2。 ^ 纖2漸變多模光纖4連接至光纖6。多模光纖 ^ $適#的方式連接至光纖6,例如藉由融合拼 由折射率相匹配之環氧樹脂。漸變多模光纖4具有 圍繞著。心蕊8具有梯度折射率，其中其折 々率J ί先決定分佈變化，其中分佈由目標應用情況決 二二# = f有梯度折射率心蕊之多模光纖為業界所熟知。 isi厗肉又斤射率藉由加入掺雜劑至形成心蕊之玻璃材料不 I 達^成。光纖6亦具有心蕊12,其由包層14圍繞著。 、σ 、、任何單模光纖，包含保持偏極光纖。 =5Α及5Β顯示形成漸變透鏡化光纖（圖4中2)之方法。 =技Γ ί Ϊ，將變為圖4漸變多模光纖之多模光纖5被融合 、'6。融合拼接光纖5, 6處理過程包含放置光纖5， ^ a’ 6a為鄰接位置如圖5A所示，以及再加熱端部5a，557378 V. Description of the invention (4) Lensed fiber contains multi-mode fiber spliced to any single-mode fiber, which maintains polarized (PM) fiber. Keep the polarized fiber to propagate only one polar. Multimode and gradient refractive index (GRIN) cores, that is, the refractive index of the cores varies according to the predetermined distribution. Pull the multimode fiber to produce a graded section. The pulling process is usually achieved by heating the multimode fiber. The lens effect of the graded fiber comes from the refractive index and graded refractive index in the grade. Therefore, the divergence angle and the mode field diameter of the 2-lensed fiber are specially set to be more flexible in specific applications, which ultimately leads to a change in σ coupling efficiency. The method of the present invention enables the formation of progressively lensed optical fibers, while maintaining the polarization isolation characteristics and stress rods of the polarized fibers. Specific embodiments of the invention are described with reference to the following drawings. W shows a graded lensed optical fiber 2 according to an embodiment of the present invention. ^ Fiber 2 graded multimode fiber 4 is connected to fiber 6. Multimode fiber is connected to fiber 6 in a suitable way, for example, an epoxy resin that matches the refractive index by fusion. The graded multimode fiber 4 has a surrounding. The core 8 has a gradient refractive index, in which the refractive index J 先 determines the distribution change first, wherein the distribution is determined by the target application. # 2 = f Multimode fiber with a gradient refractive index is well known in the industry. ISI is not achieved by adding dopants to the glass material that forms the heart core. The optical fiber 6 also has a core 12 surrounded by a cladding 14. , Σ,, and any single-mode fiber, including polarization-maintaining fibers. = 5A and 5B show the method of forming a graded lensed optical fiber (2 in Fig. 4). = 技 Γ ί Ϊ, the multimode optical fiber 5 that will become the gradual multimode optical fiber of FIG. 4 is fused, and '6. The process of fusion splicing the optical fibers 5, 6 includes placing the optical fiber 5, ^ a '6a is an adjacent position as shown in FIG. 5A, and the reheating end 5a,
557378 五 、發明說明（5) —_ “同時將其推在一起如 ^ 一 源例如電阻加熱，電弧二=不。能夠使用任何適當加熱 起。一旦光纖5及6融人二光束將端部58,63融合在一 步驟。 "妍接在一起，多模光纖5施以漸變化 如圖5 Β所示，漸蠻牛跡 同時以相反方向沿著縱=包3,含严動熱源7沿著多模光纖5, 頭所示。當拉引時多模^引；^光纖5以及光纖6,如箭 電阻絲。使用電阻絲二 對稱。適合使用於太I Ϊ ^為較佳地控制漸變角度以及 包含於融合銲；r:vv二電阻广的錢 Ville，NJ 銷售，商標為 FFSj= 〇rP〇ratl〇n 〇f Mor^n-發明並不受限於該特定電阻”電青楚了解本 能夠為電孤或雷射光束 成電阻加熱。例如，加熱源7 多模=變處理過程完成時，多模光纖5看起來類似圖4中 。顯示於圖4中漸變多模光纖4作為透鏡，其十透 …來自在漸變多模光纖4中折射以及梯度折射率。通 吊二Ϊί多模光纖4之長度約為125微米或更長。如圖4所示 ，漸、楚多模光纖4之端部16具有曲率半徑。通常，曲率半秤 :當小例如約為5至30微米。使用於形成漸變化多模光；4 所使用之電阻絲（圖5 Β中7)能夠形成具有對稱模場之球 $端部（或透鏡）16。漸變化多模光纖4端部16之曲率半徑 能^藉由控制供應至電阻絲（圖5Β中7)功率而加以調整二 通常’供應至電阻絲（圖5Β中7)功率越高，曲率半徑越大。 人們了解先前所說明形成漸變的透鏡化光纖之方法能 第9頁 557378 ----- 五、發明說明（6) 夠合併漸變光纖特性及保 極光纖拉引為漸變段 /先義。一般，假如保持偏 壞。假如應力桿件被破極光纖中應力桿件將被破 將不被保持。本發明令：持保偏:偏：光纖之 藉由拼接多模光纖至保持偏極光戴=隔離特性能夠 光纖施以漸變處理。 、歲加以保持以及再將多模 在操作中，透射經由漸變透鏡化 點於離開漸變多模光纖4 ㈣ ^聚焦為- 之曲率半徑越大，點大小為越㈣多挺光纖4端部16 發明了列範例作為只作為列舉用途以及並不會作為限制本 圖6顯示漸變透鏡化光纖沿著x及¥軸之Μ γ $ 圖4)為沿著ζ軸距離之& I Μ总者=軸之換％直徑（參閱 125微乎夕夕措丄關係，該透鏡化光纖具有外徑為 接至9微来二:先ί以及GRIN心蕊直徑為62. 5微米融合耕 由出現^早模光纖。估計z軸上零點（參閱4)能夠 ί模光纖與單模光纖之間所形成拼接處光 1 Γ估计出。光束量測以數值孔徑為0. 1 7使用1 0 物距進仃光束掃描。 變段ΓΛ示Λ度Λ射強ΛΛ在多模光纖端部處所形成漸 料半+ 數。多模光纖具有125微米外徑及62.5 二_\、又折射率心蕊。在遠場中藉由使用Photon Inc•之 二厂測角輻射計LD 89 00量測係藉由+ 72至—72度掃描進行 :j輻射強度而達成。曲線圖含有單模光纖及拼接至多模 、、、、保持偏極光纖之數據。單模為[〇1^丨叫—28光纖， 第10頁 557378 五、發明說明（7) 其具有9微米心蕊以及1〇. 4微米模場直 J = 刚射光源進行量測。曲線圖顯二= 丰仫人毛散角度間相關性。在丨/e2功率 #、 所兩^ Ϊ光纖漸變化長度為300微米以及在加以圓形化為 所^要曲率半徑。補當後痒Κ t 马 、吊，梯度折射率區域長度隨著曲率半 ^曰加而減小。在小曲率半徑下，發散角度隨著曲率半徑 而增加，如一般漸變光纖預期情況。不過在曲率半徑 ς U米’發散角度開始停止增加。在曲率半徑大於^ 6微 二月况下，發散角度再度增加。由於梯度折射率區域隨著 較大曲率半徑變短，發散將增加。 本發明提供一個或多個優點。漸變透鏡化光纖能夠藉 =融合拼接單模光纖至多模光纖形成以及再將多模光纖漸 灸化°，使用該相同方法，維持偏極隔離特性之漸變化保持 偏極光纖能夠形成。本發明漸變透鏡化光纖能夠使用於各 種應用中。例如，能夠使用漸變透鏡化光纖以耦合單模光 ,發出光線進入半導體光學放大器或平面波導或其他光學 名置。同時，能夠使用漸變透鏡化光纖以相反方向耦合光 線即由半導體光學放大器或平面波導或球面雷射光源或其 他光學裝置至單模光纖。 _ 雖然本發明已對有效數目實施例加以說明，熟知此技 術者了解其他實施例能夠設計出，其並不會脫離在此所揭 不明本發明之範圍。因而，本發明範圍只受限於下列申請 557378 五、發明說明（8) 專利範圍。 11111 第12頁 557378 圖式簡單說明 附圖簡單說明： 第一圖（圖1)顯示先前技術之準直透鏡化光纖。 第二圖A及第二圖B(圖2A及2B)顯示先前技術聚焦透鏡 化光纖。 第三圖（圖3 )顯示先前技術漸變之透鏡化光纖。 第四圖（圖4 )顯示依據本發明實施例之漸變透鏡化光 纖。 第五圖A (圖5 A )顯示多模光纖拼接至單模光纖。 第五圖B (圖5 B )顯示圖5 A多模光纖被漸變化。 第六圖（圖6 )顯示依據本發明實施例之漸變透鏡化光 纖的模場直徑為離透鏡表面距離之函數。 第七圖（圖7)顯示依據本發明實施例之漸變透鏡化光 纖的遠場模場發散角度為曲率半徑之函數。 附圖元件數字符號說明： 透鏡化光纖2 ;多模光纖4;光纖5, 6 ;光纖終端5a， 6 a ;熱源7 ;心爲8 ,包層1 0 ;心淡1 2 ;包層1 4 ;光纖端部 16;透鏡化光纖20;平凸透鏡22;光纖24;透鏡化光纖 26;光纖28;单模光纖30;光纖32;凸面34;光纖遠端 3 6 ;無心蕊光纖3 8 ;透鏡化光纖4 0 ;漸變段4 2 ;單模光纖 44;透鏡凸面46。557378 V. Description of the invention (5) —_ "Push them together at the same time such as ^ one source such as resistance heating, arc two = no. Can use any appropriate heating. Once the fibers 5 and 6 are melted, the two beams will end 58 63 are merged in one step. "Ye are connected together, and the multimode fiber 5 is graded as shown in Figure 5B. The multi-mode optical fiber 5 is shown at the head. When pulling, the multi-mode ^ fiber is drawn; ^ the optical fiber 5 and the optical fiber 6, such as arrow resistance wire. Use the resistance wire two symmetrical. It is suitable for too I Ϊ ^ for better control gradient Angle and included in fusion welding; r: vv two resistors with wide resistance Ville, sold by NJ, trademark FFSj = 〇rP〇ratl〇n 〇f Mor ^ n- the invention is not limited to this specific resistance " It is capable of resistively heating electrically isolated or laser beams. For example, when the heating source 7 multimode = variation process is completed, the multimode fiber 5 looks similar to that in FIG. 4. The graded multimode fiber 4 shown in FIG. 4 is used as a lens, which is transparent ... from the refraction and graded refractive index in the graded multimode fiber 4. The length of the multimode optical fiber 4 is about 125 microns or longer. As shown in FIG. 4, the end 16 of the gradually and multi-mode optical fiber 4 has a radius of curvature. Usually, the curvature of a half-scale: when small, for example, about 5 to 30 microns. Used to form progressive multi-mode light; 4 The resistance wire (7 in Figure 5B) can form a ball with a symmetric mode field at the end (or lens) 16. The radius of curvature of the end 16 of the graded multimode fiber 4 can be adjusted by controlling the power supplied to the resistance wire (7 in Figure 5B). 2 Generally, the higher the power supplied to the resistance wire (7 in Figure 5B), the higher the curvature radius. Bigger. People understand that the previously described method of forming a graded lensed optical fiber can be described in page 9 557378 ----- V. Description of the invention (6) It is possible to combine the characteristics of graded optical fibers and to ensure that the optical fiber is drawn as a graded segment / pre-sense. Generally, if it stays bad. If the stress rod is broken, the stress rod in the fiber will be broken and will not be maintained. The invention enables: maintaining polarization: polarization: optical fiber. By splicing multi-mode optical fibers to maintaining polarized light wearing = isolation characteristics, the optical fiber can be subjected to gradual processing. Keep the multi-mode in operation, and leave the multi-mode optical fiber through the gradual lensing point 4 聚焦 ^ Focus is-the larger the radius of curvature, the larger the point size is. The listed examples are for enumeration purposes only and are not a limitation. Figure 6 shows the γ γ $ of the progressive lensed fiber along the x and ¥ axes. Figure 4) is the & I Μ distance along the z axis = total = axis The change in% diameter (refer to the relationship of 125 micrometers, the lensed fiber has an outer diameter of 9 micrometers to two: first, and the GRIN core diameter is 62.5 micrometers. Fusion early appearance fiber .It is estimated that the zero point on the z-axis (see 4) can estimate the light 1 Γ formed at the splice between the single-mode fiber and the single-mode fiber. The beam measurement is performed with a numerical aperture of 0. 1 7 using a 0 object distance to scan the beam. The variable segment ΓΛ shows that the Λ degree Λ emission intensity ΛΛ forms a gradual half number + at the end of the multimode fiber. The multimode fiber has a 125 micron outer diameter and a 62.5 π, and refractive index core. Borrow in the far field Measured by Photon Inc • Second Factory gonioradiometer LD 89 00 with + 72 to -72 degree scanning : j radiation intensity reached. The graph contains data for single-mode fiber and spliced to multimode ,,,, and polarized fiber. The single-mode is [〇1 ^ 丨 叫 -28 fiber, page 557378 V. Description of the invention ( 7) It has a 9-micron core and a 10.4-micron mode field straight J = rigid light source for measurement. The graph shows the second = correlation between the hair dispersion angle of the Fengyan people. ^ ΪThe gradient length of the optical fiber is 300 microns and it is rounded to the desired radius of curvature. After it is applied, the length of the gradient index region decreases as the curvature increases by half. Under the radius of curvature, the divergence angle increases with the radius of curvature, as expected by general graded optical fibers. However, the divergence angle starts to stop increasing when the radius of curvature ς Um '. The divergence angle increases again when the radius of curvature is greater than ^ 6 microsecond As the gradient index area becomes shorter as the radius of curvature becomes shorter, the divergence will increase. The present invention provides one or more advantages. Gradient lensed optical fibers can be formed by fusing spliced single-mode fibers to multi-mode fibers and multi-mode fibers. Gradually moxibustion Using the same method, a gradient-maintaining polarization-maintaining fiber that maintains polarization isolation characteristics can be formed. The gradient-lensed fiber of the present invention can be used in various applications. For example, a gradient-lensed fiber can be used to couple single-mode light and emit light Enter semiconductor optical amplifiers or planar waveguides or other optical devices. At the same time, you can use progressive lensed optical fibers to couple light in the opposite direction, that is, from semiconductor optical amplifiers or planar waveguides or spherical laser sources or other optical devices to single-mode fibers. The present invention has described an effective number of embodiments. Those skilled in the art know that other embodiments can be designed without departing from the scope of the present invention, which is not disclosed herein. Therefore, the scope of the present invention is limited only by the following application 557378 V. Description of the invention (8) Patent scope. 11111 Page 12 557378 Brief description of the drawings Brief description of the drawings: The first figure (Figure 1) shows a collimated lensed optical fiber of the prior art. Figures A and B (Figures 2A and 2B) show prior art focusing lensed optical fibers. The third figure (Figure 3) shows a lensed optical fiber with a gradient of the prior art. The fourth figure (FIG. 4) shows a graded lensed optical fiber according to an embodiment of the present invention. The fifth figure A (Figure 5A) shows the splicing of a multimode fiber to a single mode fiber. The fifth figure B (Figure 5B) shows that the multimode fiber of Figure 5A is graded. The sixth figure (Figure 6) shows the mode field diameter of the graded lensed optical fiber according to the embodiment of the present invention as a function of the distance from the lens surface. The seventh diagram (Fig. 7) shows that the far-field mode field divergence angle of the graded lensed optical fiber according to the embodiment of the present invention is a function of the radius of curvature. Description of the numerical symbols of the drawing elements: lensed optical fiber 2; multimode optical fiber 4; optical fiber 5, 6; optical fiber terminal 5a, 6a; heat source 7; core 8; cladding 10; light heart 12; cladding 1 4 Fiber end 16; lensed fiber 20; plano-convex lens 22; fiber 24; lensed fiber 26; fiber 28; single-mode fiber 30; fiber 32; convex surface 34; fiber distal end 3 6; coreless fiber 3 8; lens Optical fiber 40; graded section 4 2; single-mode fiber 44; lens convex surface 46.
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