JP5118900B2 - Plastic glass optical fiber - Google Patents

Description

  The present invention relates to a plastic glass optical fiber having a glass core and a plastic cladding.

As an optical fiber mainly used for short-distance optical communication such as home LAN, office LAN, and in-vehicle communication, a plastic optical fiber (hereinafter referred to as POF) whose core and cladding are both made of plastic such as PMMA (polymethylmethacrylate) resin. And a plastic clad fiber (hereinafter referred to as PCF) in which the core is made of quartz glass and the clad is made of polymer resin. In these optical fibers, the refractive index profile of the core is a step type that is constant in the core. As an advantage of the step-type refractive index distribution, when manufacturing the core base material, it can be manufactured without adding an additive such as germanium to quartz glass, so that a base material with a uniform refractive index can be manufactured at low cost. What can be done.
There is Patent Document 1 as a document in which POF is described. Moreover, there are Patent Documents 2 to 4 as documents describing PCF.

  Important parameters of the optical fiber mainly include a core diameter and a numerical aperture (hereinafter referred to as NA), which are indicators of ease of coupling with a light source, and a band indicating transmission capacity. However, in general, in a step-type optical fiber composed of one core and a clad, the NA and the band are in a contradictory relationship. When the NA is increased, the band is narrowed. To widen the band, it is necessary to decrease the NA. When NA is reduced, the coupling efficiency with the light source is deteriorated.

  In general, the bandwidth of a multimode optical fiber is mainly due to multimode dispersion. The multimode dispersion is represented by the group delay time difference between modes, and the difference between the mode with the fastest group delay time and the slowest mode (maximum group delay time difference) is the multimode dispersion with the maximum. In general, in the case of a one-stage core structure having a step type refractive index profile, the number of modes depends only on the NA or relative refractive index difference (hereinafter referred to as Δ), the fastest mode is the fundamental mode, and the slowest mode is the highest order mode. It becomes. Therefore, the only way to improve the bandwidth is to reduce NA (or Δ) as described above. However, since NA (or Δ) does not depend on the core diameter, a desired core diameter can be selected regardless of the setting of NA (or Δ).

ここで、ｎ_１はコアの屈折率、ｎ_２はクラッドの屈折率である。 In general, Δ and NA are expressed by the following equations.

Here, n ₁ is the refractive index of the core, and n ₂ is the refractive index of the cladding.

In order to solve such problems, the refractive index distribution of the core is set to α power distribution (Patent Documents 5 and 6), or a multistage core fiber composed of a plurality of cores having different refractive indexes (Patent Document 7). ) A two-stage core fiber (Patent Document 8) has been proposed.
Japanese Patent Laid-Open No. 08-122542 Japanese Patent No. 2779410 Japanese Patent No. 2836069 Japanese Patent No. 3446208 Japanese Patent Laid-Open No. 08-304638 JP 2000-214342 A JP 2005-321686 A Japanese Patent Laid-Open No. 10-282353

In the case of a one-stage core PCF fiber having a step-type refractive index profile, the core diameter can be increased as long as Δ satisfies the band. However, when the core diameter (that is, the glass diameter) is increased, the fiber is easily bent (flexibility). ) Deteriorates and the probability of fracture against bending increases, and the core diameter is limited from the viewpoint of life.
On the other hand, if the refractive index distribution of the core is made to be an α power distribution or a multistage core fiber, the manufacturing conditions become complicated, the manufacturing cost becomes high, and the original advantage, the point of being inexpensive, is lost. .

As a method for solving the above problems, Patent Document 8 proposes an optical fiber having a two-stage core structure. In general, in the case of a two-stage core, unlike the first-stage core, the refractive index of the second-stage core is lower than that of the first-stage core, so the first-stage core diameter (a ₁ ), the second-stage core diameter (a ₂ ), and The mode that determines (causes) the maximum value of multimode dispersion changes depending on the correlation between the first-stage relative refractive index difference (Δ ₁ ) and the second-stage relative refractive index difference (Δ ₂ ). In the case of structure, it corresponds to the fundamental mode and the highest order mode).

In the said patent document, it is set as the 2 step | paragraph core structure which consists of a quartz glass core, a polymer resin core, and a resin clad, ratio of a 1st core diameter and a 2nd core diameter, and the bending rate of a 1st core and a 2nd core It defines the ratio of differences and their interrelationships. However, even under the conditions described in this document, the band is narrowed in some cases as compared to the case of the single-layer core, or even if effective, the band is only about 20% higher than that of the single-stage core. The bandwidth cannot be wide enough. Moreover, it is not mentioned from a viewpoint of NA, a core diameter, and bending resistance.
What has become a more recent problem is that an optical fiber with a large aperture and a high NA is desired in order to improve the coupling efficiency with the light source even if the bandwidth is the same as that of the one-stage core. Yes.

  The present invention has been made in view of the above circumstances, and is a plastic glass light having a large diameter and a high NA while improving the bending resistance while having a bandwidth equal to or higher than that of a single-stage core fiber. It is an object to provide a fiber.

In order to solve the above problems, the present invention provides a glass core made of glass, a polymer core made of a fluorine-added polymer having a refractive index lower than that of the glass core provided on the outer periphery of the glass core, and the polymer. An optical fiber comprising a polymer clad made of a polymer having a refractive index lower than that of the polymer core provided on the outer periphery of the core;
When the diameter a _{1 of the} glass core is in the range of 110 μm or more and 200 μm or less, the diameter of the glass core is a ₁ , and the diameter of the polymer core is a ₂ , X = a ₂ ² / a ₁ ² The parameter X defined by is in the range of 1.2 ≦ X ≦ 2.9,
When the relative refractive index difference between the glass core and the polymer core is Δ ₁ , and the relative refractive index difference between the polymer core and the polymer cladding is Δ ₂ , it is defined as Y = Δ ₂ / Δ ₁ The parameter Y is within the range of 0.25 ≦ Y ≦ 0.84X−0.68 within the range of 1.2 ≦ X ≦ 2 with respect to the parameter X, and 2 ≦ X ≦ 2.9. Within the range of 0.48X−0.71 ≦ Y ≦ − (2/9) X + 13/9,
When the diameter of the polymer core is a ₂ , the refractive index of the glass core is n ₁ , the refractive index of the polymer core is n ₂ , and the refractive index of the polymer cladding is n ₃ , Z _2core = a ₂ ² π / 4 × ^{_{√ (n 1 2 -n 3 2}} ), Z 1core = a 1 2 π / 4 × √ (n 1 2 -n 2 2) parameter is defined in _{Z 2core,} the ratio of _{Z 1core Z R = Z 2core /} Z _1core is in the range of 1.25 ≦ Z _R ≦ 4 ,
Providing a plastic glass optical fiber to 0.8% ≦ Δ ₁ ≦ 1.2% der wherein Rukoto.

In the optical fiber of the present invention, before Symbol parameter X is preferably 1.8 or more.
The parameter Y is preferably equal to 1.
The thickness of the polymer core defined by (a ₂ −a ₁ ) / 2 is preferably 10 μm or more.

  According to the optical fiber of the present invention, it is possible to provide an optical fiber having a large diameter and a high NA while having a bandwidth equal to or higher than that of a single-stage core fiber and improving bending resistance. Become.

The present invention will be described below with reference to the drawings based on the best mode.
FIG. 1 schematically shows the refractive index distribution of the optical fiber of this embodiment. The optical fiber of the present invention includes a glass core made of glass, a polymer core made of a fluorine-added polymer having a refractive index lower than that of the glass core provided on the outer periphery of the glass core, and an outer periphery of the polymer core. And a polymer cladding made of a polymer having a refractive index lower than that of the polymer core.

In the optical fiber of the present invention, the glass core can be composed of quartz glass, quartz glass obtained by adding an additive such as germanium to quartz glass, and multicomponent glass. In particular, it is preferable to construct a glass core (ie, a quartz core) from quartz glass to which no additive is added, because a core having a uniform refractive index can be constructed at low cost.
The fluorine-added polymer constituting the polymer core can be appropriately selected from fluorine-added polymers conventionally used for PCF.
As the polymer constituting the polymer cladding, it can be appropriately selected from various polymers other than the fluorine-added polymer conventionally used for PCF. It is preferable to use a fluorine-added polymer for the polymer cladding.

In FIG. 1, a ₁ is the diameter of the glass core, a ₂ is the diameter of the polymer core, n ₁ is the refractive index of the glass core, n ₂ is the refractive index of the polymer core, n ₃ is the refractive index of the polymer cladding, and Δ ₁ is relative refractive index difference between the glass core and the polymer core, delta ₂ is a relative refractive index difference between the polymer core and polymer cladding.

これらの式において、ｎ_１はガラスコアの屈折率、ｎ_２はポリマーコアの屈折率、ｎ_３はポリマークラッドの屈折率を示し、これらはｎ_１＞ｎ_２＞ｎ_３の関係を満たす。 Here, the relative refractive index differences Δ ₁ and Δ ₂ are defined by the following equations in the same way as the above-described Δ defining equation.

In these formulas, n ₁ is the refractive index of the glass core, n ₂ is the refractive index of the polymer core, n ₃ is the refractive index of the polymer cladding, and these satisfy the relationship n ₁ > n ₂ > n ₃ .

As a result of intensive studies by the inventors, it is possible to increase the NA while maintaining the transmission band by appropriately adjusting the parameters a ₁ , a ₂ , Δ ₁ , and Δ _2. In terms of conditions, an optimum relationship that can maximize the core diameters a ₁ and a ₂ has been found and will be described in detail below.

Optical fiber of the present invention, the diameter _{a 1} of _the glass core is more than 110 [mu] m, in the range below 200 [mu] m,
And, _{a 1} the diameter of the glass core, when the diameter of the polymer core and _{a 2,} a parameter X is defined by ^{_{X = a 2 2 / a 1}} 2, of 1.15 ≦ X ≦ 2.9 Is in range,
When the relative refractive index difference between the glass core and the polymer core is Δ ₁ , and the relative refractive index difference between the polymer core and the polymer cladding is Δ ₂ , it is defined as Y = Δ ₂ / Δ ₁ The parameter Y with respect to the parameter X is within the range of 0.25 ≦ Y ≦ 0.84X−0.68 within the range of 1.15 ≦ X ≦ 2, and 2 ≦ X ≦ 2.9. Within the range of 0.48X−0.71 ≦ Y ≦ − (2/9) X + 13/9,
When the diameter of the polymer core is a ₂ , the refractive index of the glass core is n ₁ , the refractive index of the polymer core is n ₂ , and the refractive index of the polymer cladding is n ₃ , Z _2core = a ₂ ² π / 4 × ^{_{√ (n 1 2 -n 3 2}} ), Z 1core = a 1 2 π / 4 × √ (n 1 2 -n 2 2) parameter is defined in _{Z 2core,} the ratio of _{Z 1core Z R = Z 2core /} Z _1core satisfies the relationship that 1.25 ≦ Z _R ≦ 4.

The parameters X and Y are defined by the following formula.

In the optical fiber of the present _invention, the parameter X is defined by ^{_{X = a 2 2 / a 1}} 2, is in the range of 1.15 ≦ X ≦ 2.9. When X is outside this range, the band becomes a value equal to or less than that of the case of the single layer core, and the effect of the double layer core does not appear.
More preferably, the parameter X is preferably 1.8 or more. That is, when the value is in the range of 1.8 ≦ X ≦ 2.9, the parameter Z is twice or more that of the single-layer core, so that a sufficiently high coupling effect with the light source can be obtained.
When the coupling efficiency is high, the processing accuracy required for the connector becomes rough, so that the processing cost becomes low, and there is an advantage that the entire system can be constructed at low cost.

Furthermore, in the optical fiber of the present invention, the parameter Y defined by Y = Δ ₂ / Δ ₁ satisfies the following relationships (i) and (ii) with respect to the parameter X.
(I) When 1.15 ≦ X ≦ 2, 0.25 ≦ Y ≦ 0.84X−0.68 (ii) When 2 ≦ X ≦ 2.9, 0.48X−0.71 ≦ Y ≦ − (2/9) X + 13/9

By satisfying the above relationship between the parameters X and Y, the bandwidth, NA, and core diameter are superior in all conditions within this range compared to the case where the optical fiber having the two-layer core structure is a single-layer core. An optical fiber can be obtained.
In order to facilitate understanding of the range where the parameters X and Y satisfy the relationship (i) and (ii), the boundary line of the range is shown by a thin solid line in FIG.

  When X and Y satisfy the above relationships (i) and (ii), the value of Y is in the range of 0.25 ≦ Y ≦ 1. When Y is outside this range, the band becomes a value equal to or less than that in the case of the single layer core, and the effect of the double layer core does not appear.

More preferably, Y = 1 is preferable. If X and Y satisfy the above relationships (i) and (ii), Y = 1 when X = 2. By doing so, since the NA becomes the maximum value (about 1.4 times) while maintaining the band, sufficiently high coupling efficiency with the light source can be obtained.
When the coupling efficiency is high, the processing accuracy required for the connector becomes rough, so that the processing cost becomes low, and there is an advantage that the entire system can be constructed at low cost.

In the optical fiber of the present invention, it is desirable that the relative refractive index difference Δ ₁ between the glass core and the polymer core is 1.2% or less. By delta ₁ is in this range, the bandwidth becomes 20 MHz · miles or more, as short optical fiber may be a sufficiently high bandwidth.

In the optical fiber of the present invention, the diameter a ₁ of the glass core is 110 μm or more and 200 μm or less. When the glass core diameter a ₁ is less than 110 μm, there is no particular problem in the characteristics as a two-layer core fiber, but a one-layer core fiber having a core diameter that is the same Z as the two-layer core fiber is made of glass. Since the design can be made with a core diameter of 200 μm or less, even a single-layer core fiber can sufficiently ensure the life against bending, and the advantages of the two-layer core cannot be utilized. Meanwhile, when the glass core diameter a ₁ is greater than 200 [mu] m, even a two-layer core is not limited to one layer core, since shortening of the life against bending is large, which is not desirable. In a two-layer core fiber, if the glass core diameter a ₁ is 110 μm or more and 200 μm or less, the glass core diameter can be within a desirable range from the viewpoint of the life against bending while maintaining a large Z parameter, which is preferable. .

In the optical fiber of the present invention, the thickness of the polymer core is preferably 10 μm or more. Here, the thickness of the polymer core is defined by (a ₂ −a ₁ ) / 2. When the thickness of the polymer core is less than 10 μm, it is difficult to adjust the amount of eccentricity of the polymer core with respect to the glass core at the time of manufacturing an optical fiber (concentric), which is not practical. However, by setting the thickness of the polymer core to 10 μm or more, it becomes easy to adjust the amount of eccentricity small, and the productivity is improved.

In the optical fiber of the present invention, when the diameter of the polymer core is a ₂ , the refractive index of the glass core is n ₁ , the refractive index of the polymer core is n ₂ , and the refractive index of the polymer cladding is n ₃ , Z _2core = a _{2 ^{2 π / 4 × √ (n}} 1 2 -n 3 2), Z 1core = a 1 2 π / 4 × √ (n 1 2 -n 2 2) the parameter _Z 2Core _defined, the ratio of _{Z 1core Z R = Z} 2core _{/ Z} 1core is within the range of 1.25 ≦ _{Z R} ≦ 4.
If the value of the parameter Z _R is not within the above range, it can be said that there is no advantage of the two-layer core structure, and the value of the parameter Z _R is within the range together with the parameters X and Y. Thus, it is possible to improve the fracture probability, improve the NA, and improve the bandwidth.

Hereinafter, the present invention will be specifically described with reference to examples.
As shown in Table 1, quartz glass having a diameter a ₁ (refractive index n ₁ = 1.457) is used as a glass core, a polymer core having a diameter a ₂ is formed on the outer periphery, and a polymer cladding is formed on the outer periphery. An optical fiber was prototyped. For the polymer core and the polymer cladding, fluorine-added polymers with adjusted refractive indexes (n ₂ , n ₃ ) were prepared, so that optical fibers having desired relative refractive index differences Δ ₁ and Δ ₂ were obtained. There are a total of 19 types of optical fibers prototyped as described in Examples 1 to 12 and Comparative Examples 1 to 7.
In FIG. 2, the range of the X and Y values in the optical fiber of the present invention is indicated by thin solid lines, and the X and Y values in the respective examples and comparative examples are indicated by symbols.

The values of parameters X, Y, and Z were calculated for the optical fibers according to each of the prototypes and comparative examples, and the NA and bandwidth were obtained.
Further, for comparison with an optical fiber having a single-layer core structure having a glass core having a refractive index n ₁ and a polymer cladding having a refractive index n ₂ and having a relative refractive index difference Δ equal to Δ ₁ , the NA ratio, Z _R , The single-layer core design core diameter, band ratio, estimated break probability, and single-layer core estimated break probability were determined, and each optical fiber was evaluated. These results are shown in Tables 1 and 2.
The estimated fracture probability was evaluated as “◯” when the glass core diameter a ₁ was 200 μm or less, and “x” when a ₁ exceeded 200 μm.

Here, the NA ratio, Z _R , and band ratio are the glass core diameter and refractive index equal to the glass core diameter a ₁ and refractive index n _{1 of the} two-layer core fiber, and the refractive index of the polymer cladding is 2 NA, Z, and s determined for a single layer core fiber equal to the refractive index n ₂ of the polymer core of the layer core fiber (the relative refractive index difference Δ of the _single layer core fiber is equal to Δ ₁ of the two layer core fiber) It is a ratio to the band (that is, a ratio represented by [value for two-layer core fiber] / [value for one-layer core fiber]). These ratios indicate that if the value is greater than 1, the two-layer core fiber is superior to the one-layer core fiber.

1-layer core design core diameter is equal to the refractive index n ₁ of the glass core refractive index of the glass core is 2-layer core fiber, and the refractive index n ₂ of the polymer core of the refractive index of the polymer clad two-layer core fiber (the relative refractive index difference delta of the single-layer core fiber is equal to delta ₁ of 2-layer core fiber.) equal 1-layer core fiber in, as the value of the parameter Z is equal to the value of Z of the two-layer core fiber This is the glass core diameter of the single-layer core fiber when the glass core diameter is designed.
The one-layer core estimated breakage probability is an estimated breakage probability obtained for a one-layer core fiber having the above-described one-layer core design core diameter, and “◯” when the one-layer core design core diameter is 200 μm or less. When the core diameter of the single layer core exceeds 200 μm, it was evaluated as “x”.

Details of the results will be described below.
In Examples 1 to 6, the glass core diameter a ₁ is fixed to 200 μm, Δ ₁ is fixed to 1.2%, and the polymer core diameter a _{2 is set} so that the values of X, Y, and Z _R fall within the specified ranges. A _two- layer core fiber with Δ ₂ selected. In these 2-layer core fiber, NA ratio is 1.10-1.39, _{Z R} is from 1.32 to 3.75, the band ratio is also 1 to 1.22, 1-layer core fiber and It turns out that it is excellent in comparison.

On the other hand, Comparative Example 1 is a single-layer core fiber in which the glass core diameter a ₁ is 200 μm and Δ ₁ is 1.2%. In Comparative Examples 2 to 5, the glass core diameter a ₁ is 200 μm and Δ ₁ is 1. This is a two-layer core fiber that is fixed at 2% and the polymer core diameter a ₂ and Δ ₂ are selected so that the values of X and Y do not fall within the specified range. Since Comparative Example 1 is a single-layer core fiber, the NA ratio, Z _R , and band ratio are all 1. Further, in the two-layer core fiber of Comparative Example 2 to 5, NA ratio and Z _R is 1 or more, the band ratio has become less than 1, the bandwidth as compared to the 1-layer core fiber is reduced I understand that.

From the above, the parameters X, Y, the value of Z _R is not in the range specified in the present invention, it is possible to say that the advantages obtained by the two-layer core structure does not occur, and the parameter X, Y, the value of Z _R Is within the range specified by the present invention, it can be seen that the fracture probability is improved, the NA is improved, and the bandwidth is improved.

Next, Examples 5, 7, and 8 in which only Δ is different and the values of X and Y are not changed will be described. Since Y = 1, both Δ ₁ = Δ ₂ are 1.2% in Example 5, 0.8% in Example 7, and 1.4% in Example 8. In any of these three embodiments, the NA ratio, Z _R , and band ratio are all 1 or more. Further, in Examples 5 and 7, the band is 20 MHz · km or more, which is a wide-band optical fiber, whereas in Example 8, the band is less than 20 MHz · km. Recognize. Therefore, if the delta ₁ is equal to or less than 1.2%, the bandwidth is wide, it can be seen that better properties.

Further, when Examples 1 to 6 are compared with respect to the value of Y, in Example 5 where Y = 1, Δ ₁ = Δ ₂ , and therefore, NA is the largest compared to the case where Y <1. It can be seen that the NA ratio is the largest.

Furthermore, a comparison of Examples 9 and 10 for the values of X, but in Example 9 was X = 1.8 _{Z R} is 2 or more, Z ratio Example 10 was X = 1.6 is 2 It turns out that it is less than. From this, X is that the Z _R If 1.8 or more 2 or more, it can be understood that the full play to the advantages of the two-layer core structure.

Furthermore, in Examples 11 and 12 in which the glass core diameter a ₁ is reduced, it is a matter of course that the NA ratio, Z _R , and band ratio become 1 or more by adopting a two-layer core structure. Regarding the core diameter of the single-layer core, according to Example 11, the glass core diameter is 110 μm in the two-layer core structure, whereas the glass core diameter is 216 μm in the single-layer core structure that can obtain an equivalent Z value. It means that. In this case, in the single-layer core structure, the probability of the optical fiber breaking with respect to bending deteriorates. In other words, with a two-layer core structure, sufficient reliability can be obtained even with a small bend diameter, but with a one-layer core structure, if the bend diameter is reduced, the probability of fracture increases, and the bend diameter cannot be used with a smaller bend diameter. This is not desirable. The same is shown for Comparative Examples 6 and 7 and other examples.

As described above, the glass core diameter a ₁ for a two-layer core fiber is more than 110 [mu] m, if 200μm or less, as compared with the single-layer core fiber having the same Z, excellent sufficiently bending resistance, reliability In addition, by setting the parameters X, Y, and Z _R within the ranges specified in the present invention, an optical fiber that has all of NA, Z, and bandwidth superior to those of a single-layer core fiber can be obtained. It can be seen that it can be obtained.
Moreover, by the delta ₁ to 1.2% or less, bandwidth also spread, it can be seen that better characteristics can be obtained.
Furthermore, if the value of X 1.8 or more, Z _R becomes more than doubled, the advantage of the two-layer core structure can be sufficiently exhibited.
Furthermore, by setting Y = 1, the maximum NA is obtained, and the coupling efficiency with the light source can be further improved.

  In particular, the optical fiber of the present invention can be suitably used as an optical fiber used for short-distance optical communication such as home LAN, office LAN, and in-vehicle communication.

It is a figure which shows typically the refractive index distribution of the optical fiber in the example of embodiment of this invention. It is a graph which shows the range of the value of X, Y in the optical fiber of this invention, and the value of X, Y in each Example and a comparative example.

Explanation of symbols

a ₁ ... diameter of glass core, a ₂ ... diameter of polymer core, n ₁ ... refractive index of glass core, n ₂ ... refractive index of polymer core, n ₃ ... refractive index of polymer cladding, Δ ₁ ... glass core and polymer The relative refractive index difference between the core and Δ ₂ ... The relative refractive index difference between the polymer core and the polymer cladding.

Claims (4)

A glass core made of glass, a polymer core made of a fluorine-added polymer having a refractive index lower than that of the glass core provided on the outer periphery of the glass core, and more than the polymer core provided on the outer periphery of the polymer core An optical fiber comprising a polymer clad made of a polymer having a low refractive index.
When the diameter a _{1 of the} glass core is in the range of 110 μm or more and 200 μm or less, the diameter of the glass core is a ₁ , and the diameter of the polymer core is a ₂ , X = a ₂ ² / a ₁ ² The parameter X defined by is in the range of 1.2 ≦ X ≦ 2.9,
When the relative refractive index difference between the glass core and the polymer core is Δ ₁ , and the relative refractive index difference between the polymer core and the polymer cladding is Δ ₂ , it is defined as Y = Δ ₂ / Δ ₁ The parameter Y is within the range of 0.25 ≦ Y ≦ 0.84X−0.68 within the range of 1.2 ≦ X ≦ 2 with respect to the parameter X, and 2 ≦ X ≦ 2.9. Within the range of 0.48X−0.71 ≦ Y ≦ − (2/9) X + 13/9,
When the diameter of the polymer core is a ₂ , the refractive index of the glass core is n ₁ , the refractive index of the polymer core is n ₂ , and the refractive index of the polymer cladding is n ₃ , Z _2core = a ₂ ² π / 4 × ^{_{√ (n 1 2 -n 3 2}} ), Z 1core = a 1 2 π / 4 × √ (n 1 2 -n 2 2) parameter is defined in _{Z 2core,} the ratio of _{Z 1core Z R = Z 2core /} Z _1core is in the range of 1.25 ≦ Z _R ≦ 4 ,
0.8% ≦ Δ ₁ ≦ 1.2% der Rukoto plastic glass optical fiber according to claim. The plastic glass optical fiber according to claim 1, wherein the parameter X is 1.8 or more. The plastic glass optical fiber according to claim 1 or 2 , wherein the parameter Y is equal to one. (A _{2 -a} 1) / 2 the thickness of the polymer core defined by the plastic glass optical fiber according to any one of claims 1 to 3, characterized in that at 10μm or more.

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