JPS60249110A - Optical fiber core clad with layer of low linear expansion coefficient - Google Patents

Abstract

PURPOSE:To obtain an optical fiber core capable of cladding with high speed and having superior transmission efficiency causing only small loss and high reliability for a long range of the length and being produced with inexpensive cost by cladding secondarily a thermoplastic resin exhibiting crystallinity in the molten state on the external periphery of an optical fiber strand consisting of an optical fiber and a primary clad layer. CONSTITUTION:Any liquid crystal polymer may be used for the thermoplastic resin of the secondary cladding material so far as it has <=1X10<-5>/ deg.C coefft. of linear expansion under the cladding condition. Specific examples are a thermotropic liquid crystal consisting of polyethylene terepthalate (PET) and p-oxybenzoic acid (POB). From the view point of easiness in handling the optical fiber core and alpha and the behavior of contraction at high temp, the preferred range of the POB content in the PET/POB copolymer is 40-80mol%. If such copolymer is used, a slow cooling stage is unnecessary but the cooling may be performed by quenching for a short time. Thus, high speed cladding has become realized.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention' relates to an optical fiber core wire having a low coefficient of linear expansion and a high modulus of elasticity for use in optical communication cables.

[Prior art]

Glass fiber for optical communication (hereinafter abbreviated as fiber)
has a small outer diameter, typically on the order of 10 D pm,
It is an extremely fragile material.

However, if used as is, scratches will occur on the fiber surface during the manufacturing process or cable-making process, which will become a stress concentration source and cause the fiber to break at an extremely low strength compared to its original strength (approximately 7 kg). do. For this reason, a highly reliable i-transmission line cannot be formed.

Conventionally, the following two types of fiber core wires have been proposed from the viewpoint of preventing a decrease in fiber breaking strength, further suppressing an increase in transmission loss, or facilitating handling.

One type is a tight-structured fiber core, in which the surface of the fiber is coated with a material such as modified silicone resin immediately after spinning, and then a buffer layer is formed with silicone resin or the like, and then polyamide is coated on top of that. It is manufactured by applying a secondary coating layer of a material such as resin. The other type is a loose tube type fiber core, which is made by holding a fiber coated with acrylic resin or the like loosely in a protective plastic tube made of a material such as polyester 41 [or polypropylene resin]. .

[Problem that the invention seeks to solve]

The tight structure type fiber core has the advantage that high coating uniformity is not required in the secondary coating process because the buffer layer prevents an increase in fiber microbending loss due to nonuniform coating. However, the linear expansion coefficient of conventional secondary coating materials is on the order of 10-4℃-1, and this value is lower than the linear expansion coefficient of the fiber itself, which is 10-4℃.
Compared to the C-1 order, it is much larger. For this reason, the fiber was bent due to expansion and contraction of the secondary coating layer due to temperature changes, resulting in an increase in microbending loss. In addition, the tight structure type 7 eyeglass core wire requires a relatively long cooling process in its secondary coating process. This is done to remove as much as possible the longitudinal orientation of the fibers during the extrusion coating process of the secondary coating material by slow cooling. If slow cooling is not sufficient,
Due to orientation relaxation or recrystallization, the secondary coating layer shrinks even at room temperature, compressive strain is applied to the fiber, and microbending loss gradually increases. As the speed of the secondary coating process increases, it is practically impossible to install a sufficient slow cooling process to match the speed increase. Therefore, the direction relaxation of the secondary coating layer becomes a problem, making it difficult to increase the speed.

Ruthteny! The type fiber core wire has the advantage that the increase in microbending loss due to expansion and contraction of the protective plastic that is the secondary coating can be alleviated by appropriately setting the fiber length in the loose tube. However, since there is a large difference in linear expansion coefficient between the secondary coating layer and the fiber itself, microbending loss still occurs due to expansion and contraction of the secondary coating layer. In order to prevent an increase in microbending loss due to the difference in linear expansion coefficient between this secondary coating layer and the fiber, in the fiber manufacturing process, the loose tube is stretched and oriented in the longitudinal direction in a solid state below its melting point. is proposed.

The linear expansion coefficient of the secondary coating layer of this fiber core is 10-'℃
-! The increase in microbending is significantly suppressed. However, in order to produce this drawn and oriented loose tube core wire, a relatively long heating furnace is required for drawing and orienting the loose tube.
In order to prevent heat shrinkage of the drawn loose tube at high temperatures, it is necessary to place a heat treatment furnace after the drawing/heating furnace, which lengthens the production line and requires an accurate manufacturing process to control excess fiber length. However, there were drawbacks such as the need for high-speed coating and the difficulty of high-speed coating.

As mentioned above, with current secondary coating materials, both tight type and loose tube type coating structures cause an increase in microbending loss due to the difference in linear expansion coefficient between the coating material and the fiber, and also have high speed coating properties. It had disadvantages such as being inferior to

[Purpose of the invention]

The present invention was made to solve the problems of high linear expansion coefficient and difficulty in high-speed coating found in conventional secondary coatings, and its purpose is to enable high-speed coating, cover a long length, The object of the present invention is to provide a highly reliable, low-cost optical fiber core with excellent transmission loss.

[Structure of the invention]

To summarize the present invention, the present invention relates to a coated optical fiber with a low coefficient of linear expansion. It is characterized by being coated.

When certain crystalline polymers are heated, they may pass through a state that combines the anisotropy of a crystal with the fluidity of a liquid before melting and becoming an optically isotropic liquid. . This state is called liquid crystal, and the liquid crystal produced by heating is called thermotropic liquid crystal.

A polymer in a crystalline state when no external force is applied is generally a collection of domains in a certain arrangement order. It is known that when an external mechanical force is applied to this system, the domains deform and flow, and then collapse, and the polymer chains become oriented in the flow direction. As described above, since the liquid crystal is oriented in the flow direction, the melt viscosity of thermotropic liquid crystal is extremely low, and it is known that in shear flow, the higher the shear rate, the lower the melt viscosity.

As a method to flow and align thermodropink liquid crystal,
There is a method of ejecting liquid crystal from a small nozzle. That is, in extrusion molding, polymer chains can be oriented in the extrusion direction by shear stress when extruding thermodropink liquid crystal from a small die. The liquid crystal oriented in this manner maintains its oriented state even after the temperature is lowered, has a low coefficient of linear expansion in the direction of alignment, and has a high modulus of elasticity.

Another method for fluidizing and orienting thermodropink liquid crystal is to perform flow stretching during extrusion molding so that the cross-sectional area of the final resin molded product in the extrusion direction is smaller than the cross-sectional area at the die exit. That is, this is a method in which molecular chains are oriented in the extrusion direction by drawing down the resin.

The aligned liquid crystal molded at °C in this manner also has a low coefficient of linear expansion and a high modulus of elasticity.

As mentioned above, thermodropink liquid crystals undergo highly molecular orientation due to shear stress or flow stretching. However, the degree of molecular orientation is significantly dependent on the resin temperature during orientation. Generally, when the resin temperature is high, molecular orientation is difficult to occur and the orientation temperature becomes low. On the other hand, when the resin temperature is low, molecular orientation is likely to occur and the degree of orientation is high.As the orientation temperature increases, the coefficient of linear expansion in the orientation direction decreases and the Young's modulus increases. In order to obtain this, it is necessary to accurately control the resin temperature during orientation.

The coefficient of linear expansion of thermotropic liquid crystals decreases with orientation,
Young's modulus increases. At the same time, the elongation at break decreases with increasing orientation. A decrease in elongation at break results in a decrease in bending resistance when the molded product is a rond or tube. That is, it easily bends and breaks. In order to make it difficult to break when bent, it is necessary to control the degree of orientation of the thermodropink liquid crystal as well as the material properties of the liquid crystal itself. It is also possible to blend thermodropink liquid crystals with other flexible polymers to improve bending properties.

In the present invention, thermodropink liquid crystal is used as the secondary coating material. As mentioned above, the physical properties of the thermodropink liquid crystal vary significantly depending on the processing conditions, that is, the alignment conditions, as well as the properties of the liquid crystal itself. Therefore, in order to obtain a coated optical fiber with a low coefficient of linear expansion, it is necessary to clarify the appropriate range of the secondary coating material and its processing conditions.

The thermoplastic resin used in the present invention and its extrusion are as follows:
The coating conditions will be explained in detail.

The thermoplastic resin used in the present invention may be any liquid crystal polymer that exhibits a coefficient of linear expansion of IX'10-5°C or less under the following coating conditions. A thermotropic liquid crystal composed of p-oxybenzoic acid (hereinafter abbreviated as POB) and p-oxybenzoic acid (hereinafter abbreviated as POB) will be described.

The thermodropink liquid crystal made of PET and POB mainly includes the following (→, (B) and (each group represented by 0: CB) -0-CH, -CH,, -0-, and It is a liquid crystal polymer with groups (C) and (B) in equal amounts.The liquid crystallinity of the resistant copolymer changes depending on the composition of the group (C).

In Figure 1, the shear rate (r) is I x 103 sec-'
, shear-oriented PET/POB with a drawdown ratio (λ) of 1
The dependence of the linear expansion coefficient (b) of the copolymer at 20°C on POB molding is shown. That is, FIG. 1 shows PF, TlPOB
The copolymer has a coefficient of linear expansion (101°C (vertical axis)) and F
It is a graph showing the relationship with IOB content (molti) (horizontal axis). From Fig. 1, if the required condition is I x 10-5°C-1 as α of the optical fiber secondary coating layer, then PO
It can be seen that approximately 40 molti or more is required as the B composition ratio.

In Figure 2 > = I X 10"5ec-', λ = 1
Figure 2 shows the P O'B morch dependence a of the thermal shrinkage rate at high temperatures of the above copolymer which was shear oriented at . In other words, Figure 2 shows the relationship between the thermal contraction rate (A) (vertical axis) and the contraction temperature T (6) or 1/
2 is a graph showing the relationship between k x 10"' (k-1) (horizontal axis). As is clear from FIG. 2, as the 1cPOB content increases, the thermal shrinkage start temperature increases and the thermal shrinkage rate also decreases. In addition, the maximum operating temperature of optical fiber core wire is 80
℃, it can be seen that the POB content needs to be 40 molti or more in order to have no thermal shrinkage at 80℃. From the results of Figures 1 and 2 regarding linear expansion coefficient and high temperature contraction coefficient, it can be seen that a POB content of approximately 40 molti or more is required.

FIG. 3 shows the relationship between Young's modulus (g) and POB morch. That is, FIG. 3 is a graph showing the relationship between Young's modulus (GPa) (vertical axis) and POB content (molch) (horizontal axis). As is clear from Figure 6, the POB content is 40
B2 = 4 GPa in Morch. Figure 4 shows α and 1.
(In other words, Figure 4 shows the linear expansion coefficient (10-5
3 is a graph showing the relationship between ℃=I) (vertical axis) and Young's modulus (GPa) (horizontal axis). From Figure 4, E is 4 GP
From a and above, it can be seen that α is I x 10-'°C-1 or less no matter what processing conditions are used. This result shows that the lower limit of E of the secondary coating layer is 4C)Pa.

With the increase in POB mole of PET/POB copolymer,
While the reduction in α and the increase in E progress in the orientation direction, the elongation at break in the orientation direction decreases significantly. That is, it has the disadvantage that it easily breaks when bent. PET/POB (=30/70) on optical fiber (coated outer diameter α4 m)
In the fiber coated with a secondary coating (outer diameter 1 mm), the secondary coating layer was broken at four bending radii. This allowable bending radius varies depending on the orientation conditions, but as long as it is within the range of normal extrusion conditions, it is most dependent on the POB content.

As a result of studying the relationship between the POB content and the allowable bending radius, it was found that the allowable bending radius increases as the POB content increases. Considering the ease of handling of the optical fiber, the allowable bending radius is approximately 4 cm.

Therefore, the upper limit of the POB content of the PET/POB copolymer in the present invention is 80 mol.

Also, from the results regarding α and high temperature shrinkage, POB
There is no need for a large amount of deterioration. From the above points, it is appropriate to set the POB content in the range of 40 to 80 mol.

Blends of PETlPOB copolymers and other polymers can also be used as secondary coating materials. In this case, the expected effect is the improvement of the allowable bending radius mentioned above.

The present inventors attempted to blend the PET/POB copolymer with various polymers, and the results were as follows: polyethylene terephthalate, polybutylene terephthalate, thermoplastic polyether ester (trade name: Hytrel, etc.), polycarbonate, SB, S( Styrene-butadiene-styrene copolymer), polyarylate (trade name: U polymer), polyether sulfone, polysulfone, polyenylene sulfide, polyether, thermoplastic polyolefin elastomer (Sumitomo TPE, etc.) are used as blending polymers. 11 It was found that the elongation at break increased. The elongation at break of the blend gradually increases as the content of the blending polymer increases in the range of 5% by weight or more. On the other hand, when the above-mentioned blending polymers are blended, the linear expansion coefficient and Young's modulus of the blend suddenly change when the content of the blending polymer exceeds 60% by weight, and the linear expansion coefficient increases and the Young's modulus decreases. do. Especially linear swelling
The tensile strength is 60% by weight or more, and if a blending polymer is added, it exceeds the upper limit of I x 10-5°C. Therefore, when blending the PET/POB copolymer with the above polymer, it is necessary to include the blending polymer in a range of 5 to 60% by weight.

In the present invention, the secondary coating material is 220°C to 320°C.
must be melt extrusion coated within an extrusion temperature of . In thermodropink liquid crystal, the transition point from a solid state to a liquid crystal state with fluidity is called the liquid crystal transition temperature, and when the above transition temperature is observed with a true stage microscope under crossed Nicols, it is found that in the case of PET/POB copolymer. , approximately 2
It turned out to be 20°C. Therefore, the lower limit of extrusion temperature is 220°C. When the extrusion temperature is further increased, an optically isotropic layer that does not exhibit liquid crystallinity appears within the optically anisotropic layer that exhibits liquid crystallinity. In the case of PgT/POB copolymers, an optically isotropic layer appears at about 620°C.

In the present invention, since the purpose is to form a secondary coating layer with molecular orientation in the extrusion direction, the upper limit of the extrusion temperature is set to 32
The temperature shall be 0°C. Figure 5 shows Young's modulus @) (GPa) (
The graph shows the relationship between the extrusion temperature (die temperature) (vertical axis) and the extrusion temperature (die temperature) (horizontal axis). As the extrusion temperature increases, E decreases. is in the range of 10 to 30 GPa, and from Figure 4, α is 1X
It can be seen that the temperature is 10-5℃. Also, PET
/POB copolymer undergoes thermal deterioration at high temperatures, resulting in weight loss. Figure 6 shows the thermal deterioration characteristics.

In other words, Figure 6 shows weight loss rate @ (vertical axis) and temperature (b) (
It is a graph showing the relationship with the horizontal axis). As is clear from Figure 6, the weight gradually begins to decrease around 300℃, and
0. Therefore, from the viewpoint of thermal deterioration, it is appropriate to limit the upper limit of the extrusion temperature to about 320°C.

In the present invention, the molecules of the secondary coating material are oriented in the extrusion direction by shear stress between the inner wall of the die or between the inner wall of the die and the outer wall of the nimple.
X 102 sec" or more. Figure 7 shows a graph of the relationship between α and α when a PET/FOB copolymer is extruded at λ-1. In other words, Figure 7 shows the linear expansion coefficient (io = °C-1) (vertical axis) and shear rate (sec-,
') (vertical axis). As is clear from Fig. 7, as γ increases, α decreases, but >
= I X 10"5ec-', α: I X 10
-'℃-1. Therefore, the lower limit of γ is lX102
sec-1. γ increases with increasing coating speed. There is no particular upper limit to the number, but as γ increases, orientation progresses, E increases, and elongation at break decreases. As a result, the allowable bending diameter of the core wire increases. . It is desirable to set the extrusion conditions so that ) is as close to 1×10"5ec-" as possible.

In the present invention, the thermoplastic resin serving as the secondary coating material may be stretched in a molten state after being extruded from a die. Even in this case, the drawing ratio (λ) must be in the range of 1 to 10.

Here, λ is defined as λ=So/S, where So is the cross-sectional area of the resin at the time of dicing, and S
is the cross-sectional area of the coating layer after secondary coating.

Therefore, λ-1 corresponds to the case where there is no withdrawal. In order to perform continuous and stable extrusion, it is necessary to
Must be above. In Figure 8, PET/FOB copolymer was used, extrusion temperature was 240°C, > = I x 10
A graph showing the relationship between E (vertical axis) and drawing ratio (horizontal axis) showing the change in E when the molecules are oriented at ``5ec-'' -1-0g
As is clear from FIG. 8, 1cE increases as λ increases. In the case of resin 1, when λ=10, E is about 30 () Pa. As E increases, the allowable bending radius of the core wire increases.

Therefore, E should be as small as possible within the range of 4 GPa or more, and the upper limit of λ should be thick (both are preferably limited to 10 or less). Compared to conventional cored wires, the main difference is that high-speed coating is theoretically possible.In other words, in the case of conventional tight-structured fiber cores, the fibers are long enough to relax the orientation during the extrusion process as much as possible. A slow cooling step was required. If this cooling step is not sufficient, the orientation relaxation of the holamide resin etc. will occur at normal usage temperatures, resulting in shrinkage of the coating layer and increased fiber microbending loss. As mentioned above, as the speed of the secondary coating process increases, it is practically impossible to install a sufficient slow cooling process to match the speed increase.

Therefore, the relaxation of the orientation of the secondary coating layer becomes a bottleneck, making it impossible to increase the speed. On the other hand, when the liquid crystalline thermoplastic resin according to the present invention is used as a secondary coating, the molecular chains are actively oriented in the coating process to reduce the coefficient of linear expansion. As shown in FIG. 2, this takes advantage of the fact that relaxation of the orientation of the liquid crystalline thermoplastic resin does not occur at normal operating temperatures. Therefore, when manufacturing the optical fiber core wire of the present invention,
There is no need for a slow cooling process, and it is sufficient to perform rapid cooling through a short cooling process. This is a huge advantage in terms of high-speed storage. The present inventors have confirmed that a coating speed of 300 t) L/min can be achieved in a relatively short secondary coating line.

The materials and extrusion conditions regarding the low linear expansion coefficient optical fiber core wire have been described above.

〔Example〕

EXAMPLES The present invention will be explained in more detail below with reference to Examples, but the present invention is not limited thereto.

Example 1 and Comparative Example 1 An experiment was conducted under the conditions shown in Table 1 regarding the lower limit of POB content. The properties of the obtained secondary coating layer are shown in Table 1 below.

Example 2 and Comparative Example 2 An experiment was conducted under the conditions shown in Table 2 regarding the upper limit of POB content. The properties of the obtained secondary coating layer are shown in Table 2 below.

Examples 3 to 5 and Comparative Example 3 Experiments were conducted under the conditions shown in Table 6 regarding the lower limit of shear rate. The properties of the obtained secondary coating layer are shown in Table 3 below.

Example 6.7 and Comparative Example 4.5 An experiment was conducted under the conditions shown in Table 4 regarding the upper limit of the drawing ratio (λ). The properties of the obtained secondary coating layer are shown in Table 4 below.

Examples 8 and 9 Experiments were conducted under the conditions shown in Table 5 regarding the upper limit of extrusion temperature. The properties of the obtained secondary coating layer are shown in Table 5 below.

Examples 10 and 11 An experiment was conducted under the conditions shown in Table 6 regarding the blending effect.

The properties of the obtained secondary coating layer are shown in Table 6 below. In Table 6, H7 is thermoplastic polyether ester,
It is an abbreviation of the product name Hytrel.

〔Effect of the invention〕

As explained above, the optical fiber core of the present invention has a liquid crystal thermoplastic resin secondary coating layer that has a low coefficient of linear expansion and a high modulus of elasticity due to highly oriented molecular orientation in the fiber length direction. It has the advantage that there is no increase in transmission loss due to changes in operating temperature over a long length, and that it is suitable for high-speed coating.

[Brief explanation of the drawing]

Figure 1 is a graph showing the relationship between linear expansion coefficient and POB content in PET/POB copolymer, Figure 2 is a graph showing the relationship between thermal shrinkage rate and shrinkage temperature, and Figure 6 is a graph showing the relationship between Young's modulus and POB content. Graph showing the relationship with POB content, Figure 4 is a graph showing the relationship between coefficient of linear expansion and Young's modulus, Figure 5 is a graph showing the relationship between Young's modulus and extrusion temperature, Figure 6 is weight loss rate. FIG. 7 is a graph showing the relationship between the coefficient of expansion and the shear rate, and FIG. 8 is a graph showing the relationship between the Young's modulus and the drawdown ratio. POS @ Upper (mol%) Figure 1 Temperature, T ('C) 80 100 /20 /llO/60 /80 2nd
Figure POBt abundance (mole 2) Figure 3 Ya〉Reduction (ePcX) Figure 4 Figure 5 Temperature ('C) Figure 6 Drop up... Figure 8 Hand Continuing amendment (voluntary amendment) September 17, 1980 Manabu Shiga, Commissioner of the Patent Office 1, Indication of the case 1981 Patent Application No. 104673 Z
Title of the invention Relationship to the case of a person who corrects low linear expansion coefficient coated optical fibers Patent applicant address 1-1-6 Uchisaiwai-cho, Chiyoda-ku, Tokyo Name
(422) Nippon Telegraph and Telephone Public Corporation Representative Tsune Makoto Address 3-15-8 Nishi-Shinbashi, Minato-ku, Tokyo (and 2 other people) Date of 5. Amendment order Voluntary amendment 6. Subject of amendment (1) Patent in the description Column 2 of Claims: Contents of amendment The amendment shall be made as per Appendix SI of the Claims of the Specification. Z Patent Claim 1, 'yt, A low linear expansion coefficient coating characterized by secondary coating of a thermoplastic resin containing molten liquid crystalline gold on the outer periphery of an original fiber strand consisting of a fiber and a primary coating layer. Optical fiber core. 2 The secondary coating layer is -1X10' to IX10
The low linear expansion coefficient coated optical fiber core according to claim 1, having a linear expansion coefficient of '°C-1 and a Young's Y4 coefficient of 4 to 30 GPa. (5) The secondary coating layer is formed by a melt extrusion method to a thickness of 220 to 32
The low linear expansion coated fiber core according to claim 1, which is formed at an extrusion temperature range of 0°C. 4. During melt extrusion, the secondary coating layer is caused by the shear stress between the die inner wall or the die inner wall and the nipple outer wall to
The optical fiber coated with a low linear expansion coefficient according to claim 1, which is extrusion coated at a shear rate of "θec-" or more. 5. The low linear expansion coefficient coated optical fiber core according to claim 1, wherein the secondary coating layer is extrusion coated at a drawdown ratio of 1 to 10 during melt extrusion. 1, # The thermoplastic resin for the secondary coating layer has at least α
Claim 1, which is a polymer having an intrinsic viscosity of 3 and containing the following groups represented by the following formulas: (B) -0-OR, -0H2-0- The low linear expansion flat wave N-element fiber core described in 1. The thermoplastic resin for secondary coating has an intrinsic viscosity of at least a5, and each of the following (4)% (substrate and (0)) Group: (B)-0-0-OH, -0- all inclusive, and group (5) and group (B) i 37.5~
1 and 7 molts each, group (0) fc 2 s,
40-95% of the polymer containing o-66.6 moles
and 60 to 5% by weight of another thermoplastic resin, the low linear expansion coefficient coated optical fiber core according to claim 1.

Claims (1)

[Claims] 1. The outer periphery of an optical fiber wire consisting of an optical fiber and a primary coating layer is secondarily coated with a thermoplastic resin exhibiting molten liquid crystallinity. 1
1. A coated optical fiber coated with a low linear expansion coefficient. 2. The secondary MN/if is -1X 10m to I X 1
The low linear expansion coated optical fiber core according to claim 1, having a linear expansion coefficient of 0'tl knee' and a Young's modulus of 4 to 50 GPa. (5) The secondary coating layer is formed by a melt extrusion method to a thickness of 220 to 32
A coated optical fiber coated with a low coefficient of linear expansion according to claim 1, which is formed at an extrusion temperature range of 0°C. 4. When the secondary coating layer is melt-extruded, IX
The low linear expansion coefficient coated optical fiber core according to claim 1, which is extrusion coated at a shear rate of 10''5ec-' or more. The low linear expansion coefficient coated optical fiber core according to claim 1, which is extrusion coated with a drawdown ratio of 1G. & The thermoplastic resin for the secondary coating layer has at least α3
Each group represented by the following formulas (g), 03) and (C) has an intrinsic viscosity of and groups) and groups (B) in equal amounts of 10 to 30 mol each,
The coated optical fiber coated with a low coefficient of linear expansion according to claim 1, which is a polymer containing 80 to 40 moles of the group (C). 1. The thermoplastic resin for secondary coating has an intrinsic viscosity of at least 15, and each group represented by the following (A), (B) and C): (E3-0-CM, -CH, - 0-) and the group 03) to 10-! 40 to 9 of polymers containing 80 to 40 moles of group (C)
The low linear expansion coefficient coated optical fiber core according to claim 1, which comprises 5% by weight of M and 60 to 5% by weight of other thermoplastic resin.