JP2004020729A - Collimator module - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a collimator module easy to manufacture with small joint loss. <P>SOLUTION: The collimator module 11 is equipped with two refractive index distributed rod lenses 14, 16 constituting a parallel pair. The length of each rod lens 14, 16 is expressed by Z, and one lens element strip longer than 2Z is cut and used for the rod lenses 14, 16. Since the variance of refractive index distribution constant √A of the rod lenses 14, 16 is small, it is not necessary to highly accurately adjust each of the distance L between the rod lenses 14, 16 and optical fibers 15, 17. Further, since the variance of lens diameter of the rod lenses 14, 16 is small, it is not necessary to adjust the optical axes of the rod lenses 14, 16 so as to be aligned with each other. Thus, production efficiency is improved and joint loss can be made sufficiently small. <P>COPYRIGHT: (C)2004,JPO

Description

また、同一のイオン交換ロットから無作為にとった４０個のロッドレンズの一部（Ｆ，Ｇ，Ｈで示す３個のロッドレンズ）についての、屈折率分布定数√Ａ、ピッチ等の数値例を次の表２に示す。
【００６４】
【表２】

表１から明らかなように、１本のレンズ素線からとった３個のロッドレンズＣ，Ｄ，Ｅの屈折率分布定数√Ａのバラツキは±０．２％で、上記距離Ｌの変動は０．０１３ｍｍ程度であった。これに対して、同一のイオン交換ロットであっても異なるレンズ素線からとったロッドレンズＦ，Ｇ，Ｈでは、屈折率分布定数√Ａのバラツキは±０．７５％程度、距離Ｌの変動は０．０４７ｍｍ程度であった。屈折率分布定数√Ａのバラツキおよび距離Ｌの変動のいずれも、１本のレンズ素線からとった場合に比べてかなり大きい値になることがわかる。
【００６５】
次に、レンズ素線の線径のばらつきの評価について説明する。
この評価のために使用するレンズ素線（レンズ素線８０）としては、上記実施例と同じ仕様のものを使用した。また、レンズ素線の線径の測定は、測定精度が±１μｍのレーザ線径測定器により、同一レンズ素線内の８箇所（測定個所１〜８）の線径をイオン交換後に測定することで行った。同一イオン交換ロットからとった３本のレンズ素線（＃１〜＃３）についての測定データを下記の表３に示す。
【００６６】
【表３】

この表３に示す同一レンズ素線内の線径ばらつき（ばらつき）は、測定個所１〜８で測定して得た８個の測定データの最大値と最小値の差で定義した。表３から明らかなように、３本のレンズ素線（＃１〜＃３）のいずれの線径ばらつきも、測定限界に近い小さな値になっている。また、表３には、３本のレンズ素線（＃１〜＃３）についての、上記８個の測定データの標準偏差σと３σも示してある。各レンズ素線における３σの値でも、２μｍ前後の値である。なお、同一イオン交換ロット内から２８本のレンズ素線（レンズ素線８０）を抜き取って測定したばらつきの平均は、１．４μｍ、３σの平均は１．８μｍであった。
【００６７】
また、図１１は、多数のイオン交換ロットからとったレンズ素線（レンズ素線８０）について測定した平均線径（線径の平均値）の分布を示している。同図の縦軸はレンズ素線の本数を、その横軸は線径（平均線径）をそれぞれ示している。この図１１から明らかなように、その平均線径の分布は、中央値（１．８００ｍｍ）から−１０μｍ〜＋５μｍの範囲に広がっている。これに比べると、表３に示す３本のレンズ素線（＃１〜＃３）の線径ばらつき（ばらつき）は極めて小さいと言える。
【００６８】
［　変形例］
なお、この発明は以下のように変更して具体化することもできる。
・上記各実施形態で使用したロッドレンズは一例であり、本発明はイオン交換法によって製造されるものであれば、他の仕様の屈折率分布型ロッドレンズにも適用可能である。
【００６９】
・上記第２実施形態で４チャンネルのコリメータモジュールを、第３実施形態では２０チャンネルのものについて説明したが、本発明は「４」および「２０」以外の多チャンネルのコリメータモジュールにも適用可能である。
【００７０】
・上記第２および第３実施形態では、平行対となる２個のロッドレンズとして、同一レンズ素線の隣り合う位置からとったレンズを使うようにしているが、同一レンズ素線内の任意の位置からとった２個のロッドレンズを平行対となるレンズに使用してもよい。
【００７１】
・上記各実施形態では、平行対となる２個のロッドレンズを１本のレンズ素線からとったものを使用しているが、屈折率分布定数√Ａおよびレンズ径がほぼ等しい２個のロッドレンズを平行対となるロッドレンズとして使用する場合にも本発明は適用可能である。
【００７２】
・上記第２および第３実施形態では、２つのコリメータアレイを同軸に対向配置した例を示したが、本発明は２つのコリメータアレイを９０度の角度で対向配置した多チャンネルコリメータモジュールにも適用される。このようなコリメータモジュールの場合、両コリメータアレイの各平行光路が交差する個所にそれぞれミラーを配置することで、光スイッチ機能を有する多チャンネルのコリメータモジュールが構成される。
【００７３】
・上記第２および第３実施形態では、２つのコリメータアレイを同軸に対向配置した例を示したが、本発明は３つのコリメータアレイを９０度の角度で対向配置した多チャンネルのコリメータモジュールにも適用される。例えば、単一モード光ファイバに代えて偏波保持光ファイバを用い、レーザダイオードアレイ等の光源からの各出射光の出力を合成して２倍にできるようにした偏波合成モジュールにも本発明は適用可能である。この偏波合成モジュールでは、３つのコリメータアレイは互いに直交配置され、これら３つのコリメータアレイの平行光路中の各チャンネルの交差点に、偏光ビームスプリッタ等を配置する。１つのコリメータアレイの各ロッドレンズから出射する偏光と、もう一つのコリメータアレイの各ロッドレンズから出射する偏光とが各偏光ビームスプリッタで合成され、これら合成された光が残りのコリメータアレイの各ロッドレンズにそれぞれ入射するようになっている。
【００７４】
・上記第２および第３実施形態で示した第１および第２コリメータアレイの各レンズアレイや各光ファイバアレイの構成は一例であり、本発明はそのような構成に限定されるものでない。
【００７５】
【発明の効果】
以上説明したように、請求項１に係る発明によれば、平行対となる２個の屈折率分布型ロッドレンズの屈折率分布定数がほぼ等しいので、２個の屈折率分布型ロッドレンズの一方とこれに結合する光ファイバの間隔と、その他方とこれに結合する光ファイバの間隔とをそれぞれ高精度に調節する必要がない。また、平行対となる２個の屈折率分布型ロッドレンズのレンズ径がほぼ等しいので、両ロッドレンズの光軸が一致するように調節する必要がない。このため、生産効率が向上するとともに、結合損失を十分に小さくすることが可能になる。したがって、製造が容易で、結合損失の小さいコリメータモジュールを実現することができる。
【００７６】
請求項３に係る発明によれば、２Ｎ個の屈折率分布型ロッドレンズの屈折率分布定数およびレンズ径のバラツキが小さいので、平行対となるロッドレンズがＮ組ある多チャンネルのコリメータモジュールを作製する場合でも、作業効率の向上と、性能のバラツキの低減とを図ることができる。したがって、製造が容易で、結合損失の小さい多チャンネルのコリメータモジュールを実現することができる。
【図面の簡単な説明】
【図１】第１実施形態に係るコリメータモジュールの概略構成を示す平面図。
【図２】同モジュールのロッドレンズの作製に用いるレンズ素線を示す平面図。
【図３】第２実施形態に係るコリメータモジュールの概略構成を示す平面図。
【図４】同モジュールのロッドレンズの作製に用いるレンズ素線を示す平面図。
【図５】図４のレンズ素線からとったロッドレンズを示す平面図。
【図６】図３のＸ−Ｘ線に沿った断面図。
【図７】図３のＹ−Ｙ線に沿った断面図。
【図８】第３実施形態に係るコリメータモジュールの概略構成を、片方のコリメータアレイを省略して示した斜視図。
【図９】同モジュールのロッドレンズの作製に用いるレンズ素線を示す平面。
【図１０】図９のレンズ素線からとったロッドレンズを示す平面図。
【図１１】多数のイオン交換ロットからとったレンズ素線について測定した平均線径（線径の平均値）の分布を示すグラフ。
【符号の説明】
１１，２０，７０…コリメータモジュール、１４，１６，Ａ１〜Ａ４，Ｂ１〜Ｂ４，Ａ１〜Ａ２０，Ｂ１〜Ｂ２０…屈折率分布型ロッドレンズ、１８，６０，８０…レンズ素線、２３…第１のレンズアレイ、２５…第２のレンズアレイ。[0001]
TECHNICAL FIELD OF THE INVENTION
The present invention relates to a collimator module provided with at least one pair of two gradient index rod lenses serving as a parallel pair.
[0002]
[Prior art]
In general, a collimator module configured with two collimators facing each other includes a first collimator that converts light emitted from an optical fiber into parallel light using a collimator lens, and condenses the parallel light using a collimator lens to form an optical fiber. And a second collimator to be coupled. As each collimator lens of both collimators, a gradient index rod lens having a refractive index distribution in a radial direction is used. An optical functional element such as an optical filter, an optical isolator, and an optical switch is inserted between both collimators of such a collimator module. Accordingly, the collimator module exerts a predetermined action on the light propagating through the optical fiber of the first collimator, and then couples this light to the optical fiber of the second collimator to propagate the light.
[0003]
The refractive index distribution type rod lens used in such a collimator module is obtained by forming a refractive index distribution in a radial direction of a cylindrical glass by an ion exchange method. It has a certain range of variation in distribution constant and lens diameter.
[0004]
[Problems to be solved by the invention]
Therefore, when manufacturing a collimator module having functions such as an optical isolator and an optical switch using a gradient index rod lens, the refractive index distribution constant and the lens diameter of two parallel index gradient rod lenses forming a parallel pair are determined. If there is a difference, it is necessary to perform complicated and highly accurate alignment to compensate for the difference. That is, in order to compensate for the difference in the refractive index distribution constants, the distance between one of the two refractive index distribution type rod lenses and the optical fiber coupled to it, and the distance between the other and the optical fiber coupled thereto are respectively set. It had to be adjusted with high precision. At the same time, in order to compensate for the difference in lens diameter, it was necessary to make adjustments so that the optical axes of both rod lenses coincided. Further, since such high-precision alignment is required, there is a problem that it is difficult to sufficiently reduce the coupling loss of the collimator module. The term “parallel pair” as used herein refers to a relationship in which two gradient index rod lenses are coaxially or opposed to each other at an angle of 90 ° so that a parallel optical path is formed between the two lenses. Say.
[0005]
Further, with the recent increase in transmission capacity in the optical communication field, the collimator module tends to have more channels. In order to manufacture such a multi-channel collimator module, a first and a second collimator, a first and a second parallel-paired refractive index type rod lenses are arranged so as to form a plurality of pairs. And a second collimator lens array. Here, the term “channel” is used to mean that a “1” channel is constituted by a set of two refractive index distribution type rod lenses forming a parallel pair. However, when manufacturing such a multi-channel collimator module, there are problems that work efficiency is deteriorated and performance variation is likely to increase for the following two reasons. One reason is that each rod lens of the first and second collimator lens arrays and each of the rod lenses coupled thereto are provided for each channel in order to compensate for variations in the refractive index distribution constants of the respective gradient index rod lenses. This is because it is necessary to adjust the intervals between the optical fibers with high precision. Another reason is that in order to compensate for the variation in the lens diameter of each gradient index rod lens, the optical axes of the plurality of gradient index rod lenses in each of the first and second collimator lens arrays are straight. This is because it is necessary to finely adjust the position of each rod lens so as to line up on a line.
[0006]
The present invention has been made in view of such conventional problems, and an object of the present invention is to provide a collimator module which is easy to manufacture and has a small coupling loss.
[0007]
[Means for Solving the Problems]
In order to solve the above problem, the invention according to claim 1 is a collimator module including at least one pair of two gradient index rod lenses that form a parallel pair, wherein the two gradient index rod lenses are used as the two gradient index rod lenses. The point is to use a lens having substantially the same refractive index distribution constant and lens diameter.
[0008]
According to this configuration, since the refractive index distribution constants of the two parallel-paired gradient index rod lenses are substantially equal, one of the two parallel-paired gradient index rod lenses and the light coupled to the two. There is no need to precisely adjust the spacing between the fibers and the spacing between the other end and the optical fiber coupled thereto. Further, since the lens diameters of the two refractive index distribution type rod lenses forming a parallel pair are substantially equal, it is not necessary to adjust the optical axes of the two rod lenses so that they coincide. For example, since the optical axes of both rod lenses coincide only by inserting both rod lenses into one cylindrical tube, there is no need to align the optical axes. As described above, complicated and highly accurate alignment for compensating for the difference between the refractive index distribution constants and the lens diameters of the two gradient index rod lenses as in the prior art is not required, so that the production efficiency is reduced. And the coupling loss can be made sufficiently small. Here, the “gradient refractive index rod lens” refers to a rod lens having a refractive index distribution in a radial direction.
[0009]
According to a second aspect of the present invention, in the collimator module according to the first aspect, assuming that the lens lengths of the two gradient index rod lenses are Z, the two gradient index rod lenses are long. The gist of the invention is that it is manufactured by cutting one lens element wire longer than 2Z.
[0010]
According to this configuration, two parallel-paired gradient index rod lenses are manufactured by cutting one lens element wire, and thus the refractive index distribution constants of the two gradient index rod lenses. In addition, variations in lens diameter can be reduced.
[0011]
According to a third aspect of the present invention, in the collimator module according to the first aspect, a first lens array in which N refractive index distribution type rod lenses are arranged in parallel at predetermined intervals so that their optical axes are parallel to each other. And a second lens in which N gradient index rod lenses, each of which is a parallel pair with each of the gradient index rod lenses of the lens array, are arranged in parallel at predetermined intervals so that the optical axes are parallel to each other. When the lens length of each of the gradient index rod lenses is Z, the 2N gradient index rod lenses used in the first and second lens arrays are cut to 2N × Z. The point is that the lens is manufactured by cutting a single lens element wire having a length to which is added.
[0012]
According to this configuration, since 2N pieces of the gradient index rod lens are manufactured by cutting one lens element wire, variations in the refractive index distribution constants and lens diameters of the 2N pieces of the gradient index rod lenses are reduced. Can be smaller.
[0013]
In addition, since the dispersion of the refractive index distribution constants and the lens diameters of the 2N gradient index rod lenses are small, even if a multi-channel collimator module having N sets of two pairs of rod lenses forming a parallel pair is required, the work can be performed. It is possible to improve efficiency and reduce variations in performance. One of the reasons is that the refractive index distribution constant of each refractive index distribution type rod lens has a small variation, so that each rod lens of the first and second lens arrays and each This is because it is not necessary to adjust the fiber interval with high precision. That is, if each lens array and each optical fiber array provided corresponding thereto are aligned not collectively for each channel but collectively, sufficient performance can be obtained, and each optical fiber corresponding to each rod lens can be individually obtained. This is because there is no need for alignment. Another reason is that since the dispersion of the lens diameters of the gradient index rod lenses is small, the optical axes of the N gradient index rod lenses are aligned on each of the first and second lens arrays. This is because it is not necessary to finely adjust the position of each rod lens. As described above, when a multi-channel collimator module is manufactured, fine adjustment for each channel is not required, so that it is possible to improve work efficiency and reduce performance variations.
[0014]
According to a fourth aspect of the present invention, in the collimator module according to the third aspect, among the 2N gradient index rod lenses, each of the 2N gradient index rod lenses serves as a parallel pair of two gradient index rod lenses. The gist is that two gradient index rod lenses cut from positions adjacent to the line are used.
[0015]
According to this configuration, among the 2N gradient index rod lenses used for both lens arrays, the dispersion of the refractive index distribution constant and the lens diameter of each of the two gradient index rod lenses forming a parallel pair are further reduced. Become smaller. Thus, a multi-channel collimator module with a smaller coupling loss can be realized.
[0016]
The invention according to claim 5 is the collimator module according to claim 3 or 4, wherein the N number of gradient index rod lenses of the first lens array and the N number of gradient index type rod lenses of the second lens array. The gist is that the rod lenses are arranged in the order cut from the lens element wires.
[0017]
According to this configuration, variations in the refractive index distribution constant and the lens diameter of the adjacent refractive index distribution type rod lenses in both lens arrays are further reduced. As a result, the variation in performance between adjacent channels can be further reduced.
[0018]
BEST MODE FOR CARRYING OUT THE INVENTION
Hereinafter, embodiments of a collimator module to which the present invention is applied will be described with reference to the drawings.
[0019]
[First embodiment]
FIG. 1 shows a collimator module 11 according to the first embodiment. The collimator module 11 includes a first collimator 12 and a second collimator 13 arranged to face each other. The first collimator 12 includes a gradient index rod lens 14 as a collimator lens, and a single mode optical fiber 15. The second collimator 13 includes a gradient index rod lens 16 as a collimator lens, and a single mode optical fiber 17.
[0020]
The refractive index distribution type rod lenses (hereinafter, simply referred to as “rod lenses”) 14 and 16 are arranged coaxially with their optical axes aligned and facing each other at a predetermined interval. That is, there are two refractive index distribution type rod lenses in which the rod lenses 14 and 16 form a parallel pair.
[0021]
The distance between the end face of the rod lens 14 on the optical fiber side and the end face of the single mode optical fiber (hereinafter, simply referred to as “optical fiber”) 15 is set to a distance L represented by the following equation. Is adjusted to Similarly, the distance between the end face of the rod lens 16 on the optical fiber side and the end face of the optical fiber 17 is also adjusted to be a distance L represented by the following equation.
[0022]
L = 1 / ｛n₀√A × tan (√A × Z)｝ (1 formula)
Where n₀Is a refractive index on the central axis (central refractive index), ΔA is a refractive index distribution constant, and Z is a lens length. The rod lenses 14 and 16 each have a refractive index distribution approximately expressed by the following two equations in the radial direction from the center axis.
[0023]
n (r)²= N₀ ²(1-A / 2 × r²) ・ ・ ・ (2 formulas)
Here, r is the distance in the radial direction from the central axis.
The focal length f of each of the rod lenses 14 and 16 is represented by the following three equations.
[0024]
f = 1 / ｛n₀√A × sin (√A × Z)｝ (3 equations)
In the collimator module 11 having such a configuration, the light emitted from the optical fiber 15 is made parallel by the rod lens 14, and the parallel light is condensed by the rod lens 16 and coupled to the optical fiber 17. . Further, the collimator module 11 converts the light emitted from the optical fiber 17 into parallel light by the rod lens 16, collects the parallel light by the rod lens 14, and couples the parallel light to the optical fiber 15. An optical functional element such as an optical filter, an optical isolator, and an optical switch is inserted in the parallel optical path between the rod lenses 14 and 16.
[0025]
Assuming that the lens lengths of the rod lenses 14 and 16 are Z, both rod lenses 14 and 16 are manufactured by cutting one lens element wire 18 (see FIG. 2) having a length longer than 2Z. That is, the lens element wire 18 has a length of 2Z + α. Here, α is a cutting margin required to cut the lens element wire 18 once. The lens element wire 18 has a refractive index distribution formed in the radial direction of the cylindrical glass by an ion exchange method.
[0026]
According to the first embodiment configured as described above, the following operation and effect can be obtained.
(A) Since the two rod lenses 14 and 16 forming a parallel pair are formed by cutting one lens element wire 18 having a length longer than 2Z, the refractive index distribution of the rod lenses 14 and 16 is obtained. The variation of the constant √A is small. Therefore, from the above equations (1) and (3), the variation of the focal length f and the variation of the distance L are both small. Accordingly, it is necessary to adjust the distance (the distance L) between the rod lens 14 and the optical fiber 15 coupled thereto and the distance (the distance L) between the rod lens 16 and the optical fiber 17 coupled thereto with high precision. There is no. In addition, since variations in the lens diameters of the rod lenses 14 and 16 are small, it is not necessary to adjust the optical axes of the rod lenses 14 and 16 to coincide. For example, since the optical axes of both rod lenses 14 and 16 are matched only by inserting both rod lenses 14 and 16 into one cylindrical tube, there is no need to align the optical axes. As described above, complicated and highly accurate alignment for compensating for the difference between the refractive index distribution constants and the lens diameters of the two rod lenses 14 and 16 as in the above-described prior art is not required, so that the production efficiency is reduced. As a result, the coupling loss can be sufficiently reduced. Thereby, the collimator module 11 which is easy to manufacture and has small coupling loss can be realized.
[0027]
(B) Since the two rod lenses 14 and 16 forming a parallel pair are manufactured by cutting one lens element wire 18 having a length longer than 2Z, the refractive indices of the two rod lenses 14 and 1 are formed. Variations in the distribution constant and the lens diameter can be reduced.
[0028]
[Second embodiment]
FIG. 3 shows a collimator module 20 according to the second embodiment. The collimator module 20 is a four-channel collimator module including four sets of two rod lenses forming a parallel pair, and includes a first collimator array 21 and a second collimator array 22.
[0029]
The first collimator array 21 includes a first lens array 23 in which four rod lenses A1 to A4 are arranged in parallel at predetermined intervals so that the optical axes are parallel to each other, and four optical fibers 31 to 34. And an optical fiber array 24 arranged in parallel. Similarly, the second collimator array 22 includes a second lens array 25 in which four rod lenses B1 to B4 are arranged in parallel at predetermined intervals so that the optical axes are parallel to each other, and four optical fibers 35 to 38 are provided in parallel with the optical fiber array 26. A filter 27 is arranged in a parallel optical path between the two lens arrays 23 and 25.
[0030]
The rod lenses A1 and B1, the rod lenses A2 and B2, the rod lenses A3 and B3, and the rod lenses A4 and B4 are rod lenses that are coaxially opposed to each other and form a parallel pair. The rod lenses A1 to A4 are held by a lens block 40 shown in FIG. The lens block 40 includes a lower block 41 having four V-grooves a1 to a4, and an upper block 42 having four V-grooves a1 'to a4'. The lens block 40 has a rectangular parallelepiped shape, and its bottom surface 40a serves as a horizontal reference surface that is placed on a surface plate or the like when a module is manufactured. The rod lenses A1 to A4 are positioned by the four V-grooves a1 to a4 of the lower block 41. Further, the lower block 41 is provided with left and right through holes 43 and 44 in which guide pins 46 and 47 (see FIG. 3) are fitted at positions outside the four V-grooves a1 to a4, respectively.
[0031]
Like the lens block 40, the four optical fibers 31 to 34 are held by four V-grooves provided in a fiber block 45 composed of upper and lower blocks. These four V-grooves are formed at the same interval as the four V-grooves a1 to a4 of the lower block 41. The lower block of the fiber block 45 is provided with left and right through holes (not shown) at which the guide pins 46 and 47 are fitted at the same positions as the through holes 43 and 44 of the lower block 41.
[0032]
Guide pins 46 and 47 are fitted into the left and right through holes 43 and 44 of the lens block 40 and the left and right through holes of the fiber block 45, respectively. Thereby, each optical axis of the rod lenses A1 to A4 held in the V-grooves a1 to a4 of the lower block 41 and each core center of the optical fibers 31 to 34 held in the fiber block 45 coincide with each other. Has become.
[0033]
On the other hand, the rod lenses B1 to B4 are held by a lens block 50 shown in FIG. The lens block 50 includes a lower block 51 having four V-grooves b1 to b4 and an upper block 52 having four V-grooves b1 'to b4'. The lens block 50 has a rectangular parallelepiped shape, and the bottom surface 50a is a horizontal reference plane. The rod lenses B1 to B4 are positioned by the four V-grooves b1 to b4 of the lower block 51. Further, in the lower block 51, through holes 53 and 54 are formed at positions outside the four V-grooves b1 to b4, into which guide pins 48 and 49 (see FIG. 3) are fitted, respectively.
[0034]
Like the lens block 50, the four optical fibers 35 to 38 are held by four V-grooves provided in a fiber block 55 composed of upper and lower blocks. These four V-grooves are formed at the same intervals as the four V-grooves b1 to b4 of the lower block 51. The fiber block 55 is provided with left and right through holes (not shown) in which the guide pins 48 and 49 are fitted at the same positions as the through holes 53 and 54 of the lower block 51.
[0035]
Guide pins 48 and 49 are fitted into the left and right through holes 53 and 54 of the lens block 50 and the left and right through holes of the fiber block 55, respectively. Thereby, the respective optical axes of the rod lenses B1 to B4 held in the V-grooves b1 to b4 of the lower block 51 and the centers of the cores of the optical fibers 35 to 38 held in the fiber block 55 respectively match. Has become.
[0036]
Assuming that each lens length of the rod lenses A1 to A4 and B1 to B4 is Z, these eight rod lenses are produced by cutting one lens element wire 60 having a length of 8Z + β (see FIG. 4). It was done. Here, β is a cutting margin required to cut the lens element wire 60 eight times. This lens element wire 60 also has a refractive index distribution formed in the radial direction of the cylindrical glass by an ion exchange method, similarly to the lens element wire 18 shown in FIG. In addition, the broken line in FIG. 4 indicates the trajectory when the light incident on the lens element wire 60 travels in a sinusoidal manner with respect to the optical axis.
[0037]
In order to produce eight rod lenses A1 to A4 and B1 to B4, the lens element wire 60 is cut in order from one end so that the processing center value becomes the value of the lens length Z. Then, two rod lenses cut from positions adjacent to the lens element wire 60 are used as the two rod lenses that form a parallel pair with each other. That is, of the eight cut rod lenses shown in FIG. 5, the rod lenses A1 and B1, the rod lenses A2 and B2, the rod lenses A3 and B3, and the rod lenses A4 and B4 are adjacent to the lens element wire 60, respectively. It is a lens taken from a suitable position.
[0038]
Then, the cut eight rod lenses are arranged in the four V grooves of both lower blocks 41 and 51 in the order cut from the lens element wire 60, respectively. That is, the rod lenses A1, A2, A3, and A4 are placed on the V-grooves a1, 2, a3, and a4 of the lower block 41 shown in FIG. 6, respectively, and the rod lenses B1, B2, B3, and B4 are shown in FIG. It is mounted on the V-grooves b1, b2, b3 and b4 of the lower block 51 respectively.
[0039]
After the rod lens is placed in the V-groove of each of the lower blocks 41 and 51 in this way, the lower block 41 and the upper block 42 and the lower block 51 and the upper block 52 are respectively bonded.
[0040]
Thereafter, guide pins 46 and 47 are fitted into the left and right through holes of the lens block 40 and the fiber block 45 of the first lens array 23 to connect the two blocks 40 and 45 together. Similarly, guide pins 48 and 49 are fitted into left and right through holes of the lens block 50 and the fiber block 55 of the second lens array 25 to connect the two blocks 50 and 55.
[0041]
Thereafter, on the first lens array 23 side, the distance between each optical fiber side end face of the rod lenses A1 to A4 and each end face of the optical fibers 31 to 34 becomes the distance L expressed by the above equation (1). Adjust as follows. Similarly, on the second lens array 25 side, the distance between each end face of each of the optical fibers of the rod lenses B1 to B4 and each end face of each of the optical fibers 35 to 38 is adjusted to be the distance L.
[0042]
According to the second embodiment configured as described above, the following operation and effect can be obtained.
(C) Since the eight rod lenses A1 to A4 and B1 to B4 are manufactured by cutting one lens element wire 60, variations in the refractive index distribution constant √A and the lens diameter of the eight rod lenses are reduced. Can be smaller.
[0043]
(D) Since the dispersion of the refractive index distribution constant √A and the lens diameter of the eight rod lenses A1 to A4 and B1 to B4 is small, a multi-channel collimator module having four sets of two rod lenses forming a parallel pair is used. Even in the case of manufacturing, it is possible to improve work efficiency and reduce variation in performance.
[0044]
One of the reasons is that since the variation in the refractive index distribution constant ΔA of each rod lens is small, each rod lens of the first and second lens arrays 23 and 25 and each This is because it is not necessary to adjust the intervals of the optical fibers with high precision. That is, if the lens arrays 23 and 25 and the optical fiber arrays 24 and 26 provided corresponding to the lens arrays 23 and 25 are aligned collectively instead of for each channel, sufficient performance can be obtained, and each rod array corresponds to each rod lens. This is because it is not necessary to align each optical fiber individually.
[0045]
Another reason is that since the variation in the lens diameter of each rod lens is small, the center (optical axis) of the four rod lenses A1 to A4, B1 to B4 held by the respective V grooves of the lens blocks 40 and 50, respectively. Are arranged in a straight line, and the variation in lens spacing (pitch between lenses) is also reduced. For this reason, in each of the first and second lens arrays 23 and 25, it is not necessary to finely adjust the position of each rod lens so that the optical axes of the four rod lenses are aligned on a straight line.
[0046]
As described above, when a four-channel collimator module is manufactured, fine adjustment for each channel is not required, so that it is possible to improve work efficiency and reduce performance variations. This makes it possible to realize a four-channel collimator module that is easy to manufacture and has small coupling loss.
[0047]
(E) Two rod lenses A1, B1, A2, B2, A3, B3, and A4, B4 cut from adjacent positions of the lens element wire 60 are used as the two rod lenses forming a parallel pair, respectively. . For this reason, among the eight rod lenses used for the two lens arrays 23 and 25, the dispersion of the refractive index distribution constant and the lens diameter of each of the two rod lenses forming a parallel pair is further reduced. As a result, a four-channel collimator module with a smaller coupling loss can be realized.
[0048]
(F) By arranging the eight rod lenses cut from one lens element wire 60 in the cut order in the V-grooves of the blocks 40 and 50, respectively, the refraction of the rod lenses adjacent to each other in both lens arrays 23 and 25 is performed. Variations in the rate distribution constant and the lens diameter are further reduced. As a result, the variation in performance between adjacent channels can be further reduced.
[0049]
[Third Embodiment]
FIG. 8 shows a collimator module 70 according to the third embodiment. The collimator module 70 is a 20-channel collimator module including 20 sets of two parallel paired rod lenses, and includes a first collimator array (not shown) and a second collimator array 72. In FIG. 8, the illustration of the first collimator array corresponding to the first collimator array 21 in the second embodiment shown in FIG. 3 is omitted. The first collimator array has the same configuration as the second collimator array 72.
[0050]
The second collimator array 72 includes a second lens array 73 in which 20 rod lenses B1 to B20 are arranged in parallel at a predetermined interval so that their optical axes are parallel to each other, and 20 optical fibers are arranged in parallel. And an optical fiber array 74. In this example, the rod lenses A1 and B1, the rod lenses A2 and B2, the rod lenses A3 and B3,... is there.
[0051]
The rod lenses B1 to B20 are held by a lens block 75. The lens block 75 includes a lower block 76 having 20 V grooves and an upper block 77 having 20 V grooves. The lens block 75 has a rectangular parallelepiped shape, and the bottom surface 75a is a horizontal reference plane. Further, left and right through holes 78 and 79 into which guide pins (not shown) are fitted are formed in the lower block 76 at positions outside the twenty V-grooves.
[0052]
On the other hand, the twenty rod lenses A1 to A20 provided in the first collimator array are held in a lens block having 20 V grooves, like the lens block 75.
[0053]
Let Z be the lens length of each of the 40 rod lenses A1 to A20 and B1 to B20 provided in the first collimator array and the second collimator array 72. In this example, these 40 rod lenses A1 to A20 and B1 to B20 are produced by cutting one lens element wire 80 (see FIG. 9) having a length of 40Z + γ. Here, γ is a cutting margin required to cut the lens element wire 80 40 times. This lens element wire 80 also has a refractive index distribution formed in the radial direction of the cylindrical glass by the ion exchange method.
[0054]
When the forty rod lenses A1 to A20 and B1 to B20 are manufactured, the lens element wire 80 is moved from one end so that the processing center value becomes the value of the lens length Z, as in the case of the second embodiment. Cut in order. Then, two rod lenses cut from positions adjacent to the lens element wire 80 are used as the two rod lenses which are in parallel with each other. That is, of the forty cut rod lenses shown in FIG. 10, the rod lenses A1, B1, the rod lenses A2, B2, the rod lenses A3, B3,. It is a lens taken from the position adjacent to.
[0055]
Then, the forty cut rod lenses are arranged in the V-grooves of the second lens array 73 and the first lens array in the order cut from the lens element wires 80 in the same manner as in the second embodiment. That is, the twenty rod lenses B1 to B20 are placed in the cut order in the twenty V-grooves of the lower block 76 shown in FIG. Similarly, 20 rod lenses A1 to A20 are placed in the cut order of 20 V grooves of the lower block similar to the lower block 76 in the first lens array.
[0056]
Thereafter, the lower block 76 and the upper block 77 in the second lens array 73 are joined. Similarly, the lower block and the upper block in the first lens array are joined.
[0057]
Thereafter, guide pins are fitted into the left and right through holes of the lens block 75 of the second lens array 73 and the fiber block of the optical fiber array 74 to connect the two blocks. Similarly, the lens block and the fiber block of the first lens array are connected by a guide pin.
[0058]
Thereafter, on the second lens array 73 side, the distance between each optical fiber side end face of the 20 rod lenses B1 to B20 and each end face of the 20 optical fibers is adjusted to be the above distance L. I do. The same adjustment is performed on the first lens array side.
[0059]
According to the third embodiment configured as described above, the following operation and effect can be obtained.
(G) A 20-channel collimator module that is easy to manufacture and has small coupling loss can be realized.
[0060]
[Example]
In the collimator module of the present embodiment, the specifications of the forty rod lenses A1 to A20 and B1 to B20 used in the third embodiment are as follows.
[0061]
Lens diameter: 1.8mm
Refractive index distribution constant ΔA: 0.322 mm^-1(In the case of using wavelength: 1.55 μm)
Central refractive index n₀: 1.591
Lens length Z: 4.488 mm (corresponding to 0.23 pitch)
In addition, since there are 40 rod lenses, a lens element wire having a length of 250 mm including a cutting margin was prepared as the lens element element 80 shown in FIG.
[0062]
Refractive index distribution constant 、 A, pitch, etc. of a part (three rod lenses indicated by C, D, and E) of 40 rod lenses actually cut from one such lens element wire Table 1 below shows an example of the numerical value of.
[0063]
[Table 1]

Numerical examples of refractive index distribution constant √A, pitch, etc. for a part (three rod lenses indicated by F, G, H) of 40 rod lenses randomly taken from the same ion exchange lot Is shown in Table 2 below.
[0064]
[Table 2]

As is clear from Table 1, the dispersion of the refractive index distribution constant ΔA of the three rod lenses C, D, and E taken from one lens element wire is ± 0.2%, and the fluctuation of the distance L is It was about 0.013 mm. On the other hand, in the rod lenses F, G, and H taken from different lens elements even in the same ion exchange lot, the variation in the refractive index distribution constant ΔA is about ± 0.75%, and the variation in the distance L Was about 0.047 mm. It can be seen that both the variation in the refractive index distribution constant ΔA and the variation in the distance L are considerably larger than those obtained from a single lens element wire.
[0065]
Next, the evaluation of the variation in the diameter of the lens element wire will be described.
As a lens wire (lens wire 80) used for this evaluation, a wire having the same specification as that of the above embodiment was used. In addition, the measurement of the wire diameter of the lens element wire must be performed after ion exchange at eight places (measurement points 1 to 8) in the same lens element wire using a laser line diameter measuring instrument having a measurement accuracy of ± 1 μm. I went in. Table 3 below shows measurement data of three lens element wires (# 1 to # 3) taken from the same ion exchange lot.
[0066]
[Table 3]

The line diameter variation (variation) in the same lens element wire shown in Table 3 was defined as the difference between the maximum value and the minimum value of eight measurement data obtained at the measurement points 1 to 8. As is clear from Table 3, the variation in the diameter of any of the three lens element wires (# 1 to # 3) is a small value close to the measurement limit. Table 3 also shows the standard deviations σ and 3σ of the eight measurement data for the three lens wires (# 1 to # 3). The value of 3σ for each lens element wire is also a value around 2 μm. The average of the dispersion measured by extracting 28 lens strands (lens strand 80) from the same ion exchange lot was 1.4 μm, and the average of 3σ was 1.8 μm.
[0067]
FIG. 11 shows a distribution of average wire diameters (average wire diameters) measured for lens wires (lens wires 80) taken from many ion exchange lots. In the figure, the vertical axis indicates the number of lens element wires, and the horizontal axis indicates the wire diameter (average wire diameter). As is clear from FIG. 11, the distribution of the average wire diameter extends from the median (1.800 mm) to the range of -10 μm to +5 μm. Compared to this, it can be said that the line diameter variation (variation) of the three lens element wires (# 1 to # 3) shown in Table 3 is extremely small.
[0068]
[Modification]
The present invention can be embodied with the following modifications.
The rod lens used in each of the above embodiments is an example, and the present invention is applicable to a gradient index rod lens having other specifications as long as it is manufactured by an ion exchange method.
[0069]
The four-channel collimator module is described in the second embodiment and the twenty-channel collimator module is described in the third embodiment. However, the present invention is applicable to a multi-channel collimator module other than “4” and “20”. is there.
[0070]
In the second and third embodiments, as the two rod lenses forming a parallel pair, lenses taken from adjacent positions of the same lens element wire are used. Two rod lenses taken from a position may be used for a lens of a parallel pair.
[0071]
In each of the above embodiments, two rod lenses forming a parallel pair are taken from one lens element wire. However, two rod lenses having approximately equal refractive index distribution constant √A and lens diameter are used. The present invention is also applicable to a case where the lenses are used as rod lenses that form a parallel pair.
[0072]
In the second and third embodiments, the example in which the two collimator arrays are coaxially opposed to each other is shown. However, the present invention is also applied to a multi-channel collimator module in which the two collimator arrays are opposed to each other at an angle of 90 degrees. Is done. In the case of such a collimator module, a multi-channel collimator module having an optical switch function is configured by disposing a mirror at a position where each parallel optical path of both collimator arrays intersects.
[0073]
In the second and third embodiments, the example in which the two collimator arrays are coaxially opposed to each other has been described. However, the present invention is also applicable to a multi-channel collimator module in which three collimator arrays are opposed to each other at an angle of 90 degrees. Applied. For example, the present invention is also applied to a polarization combining module that uses a polarization maintaining optical fiber instead of a single mode optical fiber and combines and doubles the output of each emitted light from a light source such as a laser diode array. Is applicable. In this polarization combining module, the three collimator arrays are arranged orthogonal to each other, and a polarizing beam splitter and the like are arranged at the intersections of the respective channels in the parallel optical paths of the three collimator arrays. Polarized light emitted from each rod lens of one collimator array and polarized light emitted from each rod lens of another collimator array are combined by each polarization beam splitter, and these combined lights are combined into each rod of the remaining collimator array. Each is incident on a lens.
[0074]
The configuration of each lens array and each optical fiber array of the first and second collimator arrays shown in the second and third embodiments are examples, and the present invention is not limited to such a configuration.
[0075]
【The invention's effect】
As described above, according to the first aspect of the present invention, since the refractive index distribution constants of the two gradient index rod lenses forming a parallel pair are substantially equal, one of the two gradient index rod lenses is used. It is not necessary to precisely adjust the distance between the optical fiber and the optical fiber coupled thereto, and the distance between the other and the optical fiber coupled thereto. Further, since the lens diameters of the two refractive index distribution type rod lenses forming a parallel pair are substantially equal, it is not necessary to adjust the optical axes of the two rod lenses so that they coincide. Therefore, the production efficiency is improved, and the coupling loss can be sufficiently reduced. Therefore, a collimator module that is easy to manufacture and has small coupling loss can be realized.
[0076]
According to the third aspect of the present invention, since the dispersion of the refractive index distribution constant and the lens diameter of the 2N refractive index distribution type rod lenses are small, a multi-channel collimator module having N sets of parallel paired rod lenses is manufactured. In this case, it is possible to improve the working efficiency and reduce the variation in performance. Therefore, a multi-channel collimator module that is easy to manufacture and has small coupling loss can be realized.
[Brief description of the drawings]
FIG. 1 is a plan view showing a schematic configuration of a collimator module according to a first embodiment.
FIG. 2 is a plan view showing lens wires used for manufacturing a rod lens of the module.
FIG. 3 is a plan view showing a schematic configuration of a collimator module according to a second embodiment.
FIG. 4 is a plan view showing a lens element wire used for manufacturing a rod lens of the module.
FIG. 5 is a plan view showing a rod lens taken from the element wire of FIG. 4;
FIG. 6 is a sectional view taken along the line XX of FIG. 3;
FIG. 7 is a sectional view taken along the line YY of FIG. 3;
FIG. 8 is a perspective view showing a schematic configuration of a collimator module according to a third embodiment with one collimator array omitted.
FIG. 9 is a plan view showing a lens element wire used for manufacturing a rod lens of the module.
FIG. 10 is a plan view showing a rod lens taken from the lens element wire of FIG. 9;
FIG. 11 is a graph showing a distribution of average wire diameters (average wire diameters) measured for lens element wires obtained from a large number of ion exchange lots.
[Explanation of symbols]
11, 20, 70 ... collimator module, 14, 16, A1 to A4, B1 to B4, A1 to A20, B1 to B20 ... refractive index distribution type rod lens, 18, 60, 80 ... lens element wire, 23 ... first , 25 ... second lens array.

Claims (5)

In a collimator module provided with at least one set of two gradient index rod lenses that form a parallel pair,
A collimator module, wherein the two refractive index distribution type rod lenses have substantially the same refractive index distribution constant and lens diameter. Assuming that each of the two gradient index rod lenses has a lens length of Z, the two gradient index rod lenses are formed by cutting one lens element wire having a length greater than 2Z. The collimator module according to claim 1, wherein A first lens array in which N number of gradient index rod lenses are arranged in parallel at predetermined intervals so that their optical axes are parallel to each other;
A second lens array in which each of the gradient index rod lenses of the lens array and N number of gradient index rod lenses, each of which is a parallel pair, are arranged in parallel at predetermined intervals so that the optical axes are parallel to each other; With
Assuming that the lens length of each of the gradient index rod lenses is Z, the 2N gradient index rod lenses used in the first and second lens arrays have a length obtained by adding a margin to 2N × Z. The collimator module according to claim 1, wherein the collimator module is manufactured by cutting one lens element wire having the following. Of the 2N graded index rod lenses, two graded index rod lenses cut from adjacent positions of the lens element wires are used as two graded index rod lenses that form a parallel pair. The collimator module according to claim 3, wherein each of the collimator modules is used. The N number of gradient index rod lenses of the first lens array and the N number of gradient index rod lenses of the second lens array are arranged in the order cut from the lens element wire. The collimator module according to claim 3 or 4, wherein

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