【考案の詳細な説明】[Detailed explanation of the idea]
〔産業上の利用分野〕
本考案は主として波長0.35μｍ以下の紫外線伝
送損失を改善した紫外線伝送用光フアイバに関す
るものである。
一般に光フアイバは屈折率の大きいコアと該コ
アの外側に形成される屈折率の小さいクラツド層
とからなり、その無誘導性、絶縁性の故に信号伝
達手段として特に約0.2μｍから約1.6μｍの波長域
で有望視されている。
ところが、従来の光フアイバでは、0.35μｍ以
下の紫外線伝送領域において伝送損失が急増し、
紫外線伝送用光フアイバとして今一つ満足な特性
を有するものがなかつた。
本考案者等はコア、クラツド層の組成と紫外線
伝送損失量との関係につき実験研究を行つた結
果、コアに200ppm以上のOH基を含有せしめる
ことによつて紫外線の伝送損失が大幅に改善され
ることを知見した。
本考案はかかる知見に基づきなされたものであ
つて、その目的とするところは石英系コアと該コ
アの外周に形成されるクラツド層とからなる光フ
アイバにおいて少なくとも前記コアに200ppm以
上のOH基を含有せしめることによつて、紫外線
伝送特性の向上を図つた新規な紫外線伝送用光フ
アイバを提供するにある。
以下本考案をその実施例を示す図面に基づいて
具体的に説明する。第１図は本考案に係る紫外線
伝送用光フアイバ（以下本案品という）の横断面
図であり、図中１は光フアイバを構成するコア、
２は同じくクラツド層、３はサポート層を示して
いる。コア１は中心部にあつては高純度の石英ガ
ラスにより形成され、少なくとも200ppm以上の
OH基が含有せしめられ、また屈折率は純石英の
それに近い1.459に設定されている。クラツド層
２は同じく石英ガラスを素材とし、屈折率はコア
１のそれよりも0.002以上低く設定したものを用
いてコア１の外周にこれと同心状に形成されてい
る。コア１に含ませるべきOH基は紫外線伝送損
失の改善を目的としたものであつてコア１中の含
有量は200ppm〜1000ppm程度が望ましい。
200ppmよりも少ないと十分な紫外線伝送特性が
得られず、逆に1000ppm以上になると損失が過大
となる不都合を生じてしまうことによる。
次に本案品と参照例との比較試験結果について
説明する。
試験例 １
試験は供試材Ａ，Ｂとして夫々長さ25ｍの光フ
アイバを作成し、光源としてキセノンランプを用
い種々の紫外線について紫外線伝送損失量を測定
した。供試材Ａ，Ｂの諸元は表１に示すとおりで
ある。
[Industrial Field of Application] The present invention mainly relates to an optical fiber for transmitting ultraviolet rays with improved transmission loss of ultraviolet rays having a wavelength of 0.35 μm or less. In general, optical fibers consist of a core with a high refractive index and a cladding layer with a low refractive index formed outside the core, and because of its non-inductive and insulating properties, it is particularly useful as a signal transmission means with a thickness of about 0.2 μm to about 1.6 μm. It is seen as promising in the wavelength range. However, in conventional optical fibers, transmission loss rapidly increases in the ultraviolet transmission region of 0.35 μm or less.
There was no optical fiber for ultraviolet transmission that had even more satisfactory characteristics. The present inventors conducted experimental research on the relationship between the composition of the core and cladding layers and the amount of ultraviolet transmission loss, and found that the ultraviolet transmission loss was significantly improved by containing 200 ppm or more of OH groups in the core. I found out that. The present invention has been made based on this knowledge, and its purpose is to infiltrate at least 200 ppm or more of OH groups into the core of an optical fiber consisting of a quartz core and a cladding layer formed around the core. It is an object of the present invention to provide a novel optical fiber for ultraviolet transmission, which has improved ultraviolet transmission characteristics by containing the above-mentioned components. The present invention will be specifically described below based on drawings showing embodiments thereof. FIG. 1 is a cross-sectional view of an optical fiber for ultraviolet transmission according to the present invention (hereinafter referred to as the present product), and in the figure, 1 indicates a core constituting the optical fiber;
2 also indicates the cladding layer, and 3 indicates the support layer. Core 1 is made of high-purity quartz glass in the center, and contains at least 200 ppm or more.
It contains OH groups, and its refractive index is set at 1.459, which is close to that of pure quartz. The cladding layer 2 is also made of silica glass and has a refractive index set to be 0.002 or more lower than that of the core 1, and is formed concentrically around the outer periphery of the core 1. The OH group to be included in the core 1 is for the purpose of improving ultraviolet transmission loss, and the content in the core 1 is preferably about 200 ppm to 1000 ppm.
If it is less than 200 ppm, sufficient ultraviolet transmission characteristics cannot be obtained, whereas if it is more than 1000 ppm, the loss will become excessive. Next, the results of a comparative test between the proposed product and a reference example will be explained. Test Example 1 In the test, optical fibers each having a length of 25 m were prepared as test materials A and B, and the amount of ultraviolet transmission loss for various ultraviolet rays was measured using a xenon lamp as a light source. The specifications of sample materials A and B are as shown in Table 1.
【表】
結果は第２図に示す通りである。第２図に示す
グラフは横軸に紫外線の波長（μｍ）を、縦軸に
紫外線伝送損失量（dB／Km）をとつて示してあ
る。グラス中の実線は本案品である供試材Ａの、
また破線は参照例である供試材Ｂの各結果を示し
ている。このグラフから明らかな如く、波長
0.35μｍ以上の領域では供試材Ａ，Ｂともその紫
外線伝送損失量に実質的な差異が見られないが、
波長0.35μｍ以下の紫外領域では波長が短くなる
に従つて比較例である供試材Ｂよりも本案品であ
る供試材Ａの光伝送損失が相対的に低減されてい
ることが解る。
なお上述の実施例はコア１にのみOH基を
200ppm以上含有せしめた構成を示したが、コア
１と共にクラツド層２にも同様に200ppm以上の
OH基を含有せしめることによつて紫外線伝送損
失量の一層の低減を図れることが確認されてい
る。
以上の如く、本案品にあつてはコアに200ppm
以上のOH基を含有せしめたから、波長0.35μｍ以
下の紫外線の伝送損失を大幅に改善し得て紫外領
域での信号送受手段としての確実性を格別に高め
得るなど本考案は優れた効果を奏するものであ
る。[Table] The results are shown in Figure 2. The graph shown in FIG. 2 shows the wavelength of ultraviolet light (μm) on the horizontal axis and the amount of ultraviolet transmission loss (dB/Km) on the vertical axis. The solid line in the glass is of sample material A, which is the proposed product.
Moreover, the broken lines indicate the results for sample material B, which is a reference example. As is clear from this graph, the wavelength
In the region of 0.35 μm or more, there is no substantial difference in the amount of ultraviolet transmission loss between specimens A and B;
It can be seen that in the ultraviolet region with a wavelength of 0.35 μm or less, as the wavelength becomes shorter, the optical transmission loss of sample material A, which is the product of the present invention, is relatively reduced as compared to sample material B, which is a comparative example. In addition, in the above example, the OH group is only in core 1.
Although a structure containing 200ppm or more was shown, cladding layer 2 as well as core 1 also contained 200ppm or more.
It has been confirmed that the amount of ultraviolet transmission loss can be further reduced by containing an OH group. As mentioned above, in the case of this product, 200ppm is applied to the core.
By containing the above OH groups, the present invention has excellent effects, such as greatly improving the transmission loss of ultraviolet rays with a wavelength of 0.35 μm or less and making it extremely reliable as a means of transmitting and receiving signals in the ultraviolet region. It is something.
【図面の簡単な説明】[Brief explanation of drawings]
第１図は本案品を用いた光フアイバケーブルの
模式的断面図、第２図は本案品と参照例との比較
試験結果を示すグラフである。
１……コア、２……クラツド層、３……サポー
ト層。
FIG. 1 is a schematic cross-sectional view of an optical fiber cable using the present product, and FIG. 2 is a graph showing the results of a comparative test between the present product and a reference example. 1... Core, 2... Clad layer, 3... Support layer.