KR100307918B1 - Method for fabricating plastic optical transmission body - Google Patents

Abstract

PURPOSE: A method for fabricating a plastic optical transmission body is provided to perform a data transmission process with a high speed by forming a radial refractive index distribution on a section of a transmission body. CONSTITUTION: A high polymer sol is formed by adding a dopant of 0.01 to 50 weight percents as a non-reactive material, a crosslinking initiator, and a chain transfer agent to a methyl-meta acrylate of 100 weight percents. The high polymer sol is injected into a bar-shaped polymerization container. A polymerization reaction is performed by using an ultraviolet ray source or an infrared ray source. An optical transmission preform(2) having a refractive index concentration gradient is formed by the polymerization reaction. A plastic optical fiber having continuous refractive index distribution is formed by performing a hot-drawing process for the preform(2).

Description

Manufacturing method of plastic light transmission body having refractive index distribution

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a plastic optical transmitter, and more particularly, to a technique for manufacturing a plastic optical fiber capable of ultra-high speed data transmission by having a refractive index distribution radially on a cross section of a transmission body.

Plastic optical fiber is expected to play a role as a near-field optical transmission in recent years due to its superior bending characteristics and ease of contact compared to conventional quartz optical fibers.

Plastic optical fiber is mainly made of polymer materials such as acrylic, polycarbonate, and polystyrene, and of these, acrylic materials such as PMMA have excellent optical characteristics such as transmission loss. .

The manufacturing method can be divided into the method of heating the existing PMMA resin in the extruder and then extracting it through a die and the method of manufacturing the preform, that is, the base material and then hot stretching it in the heating furnace.

The plastic optical transmission body is composed of a core and a clad which enables total reflection to serve as a central optical transmission path. Cores generally use materials with higher refractive index than cladding.

The use of the total reflection phenomenon of the core / clad interface is called a step-index type plastic optical fiber. In addition to the increase of the transmission distance, the path difference of the optical signal occurs, thereby causing the limitation of the transmission speed.

Therefore, in order to improve the problem, it is necessary to manufacture a graded-index plastic optical fiber. In other words, by forming a continuous gradient of refractive index from the core to the cladding, it is possible to manufacture a high-speed transmission GI-POF that can eliminate the path difference of the optical signal.

That is, the optical signal passing through the transmission medium can be transmitted in the form of a sine wave, thereby reducing the distortion rate of the relative optical signal and increasing the transmission band.

The manufacturing requirement of graded index type POF having a refractive index distribution should maximize transmission band by reducing optical signal loss and accurate refractive index distribution.

Until now, the method of preparing graded index POF can be classified into copolymerization method and diffusion method. First, the copolymerization method has a difference in reactive ratio between monomers having two or more different chemical structures. It is a method of forming the refractive index distribution using.

However, as the reactivity difference of the selected monomer increases, polymerization occurs independently of each other, resulting in phase-separation, resulting in increased light scattering in the medium, leading to a decrease in permeability.

Unlike the diffusion method, an arbitrary monomer gel is prepared first, and then a monomer having a different chemical structure is added to induce diffusion on the gel to complete polymerization.

In other words, first, a gel polymer precursor (syncursor) is synthesized, a three-dimensional crosslinked structure is introduced, and monomers having different refractive indices are added and diffused to complete the polymerization by appropriate post-treatment.

However, there is a problem that the preparation of the monomer gel must be preceded and the reaction during the polymerization may be terminated, and it is difficult to control the polymerization reaction accurately and reproducibly.

In addition, the introduction of a three-dimensional crosslinked structure has low thermoplasticity, which leads to processing problems and limitations in monomer selection.

In order to solve this problem, the present invention prepares a solution by mixing a monomer such as MMA with an appropriate amount of a polymerization initiator, a chain transfer agent, and the like.

At this time, it is also possible to make a polymer sol with a certain viscosity by applying energy from the outside.

Then, a non-reactive dopant, which is a substance larger than the refractive index of the monomer, is added to the polymerization container and injected into the polymerization container, and irradiated with an IR (infrared) or UV (ultraviolet) light source from the outside to cause a polymerization reaction, thereby causing a radial refractive index concentration. When manufacturing a preform for optical transmission having a gradient (concentration gradient), and performing a hot drawing from the preform after completing the polymerization reaction, a plastic optical fiber (POF) having a diameter of 0.5-1.0mm is produced. do.

1 is a simplified configuration diagram of a plastic optical fiber manufacturing apparatus according to the thermal stretching apparatus of the present invention.

2 is a cross-sectional view of the preform and the refractive index formed.

<Explanation of symbols for the main parts of the drawings>

1: furnace 2: preform

3: drawing section 4: supply section

The present invention adds a non-reactive dopant material. That is, radical initiation reaction is performed in advance with non-reactive solvents such as CDCB (o-dichloro benzene), BB (bromo benzene), PP (3-phenyl-1-propanol), BEN (benzyl benzoate) and BBP (benzyln-butyl phthalate). It is mixed with MMA solution or MMA sol, which is processed to make it possible, and then it is sealed and injected into a glass tube with a diameter of about 10-20 mm to apply a UV or IR energy from the outside to prepare a preform having a radial refractive index distribution in the cross-sectional direction of the preform. Way.

The preform manufactured in this way has a property of thinning when it is heated above a certain temperature due to the characteristics of the thermoplastic polymer material.The preform is put into a drawing machine and controlled at an appropriate temperature and an appropriate speed so that the transmission speed and bandwidth are increased. Excellent GI-POF (plastic optical fiber) can be produced.

In the existing SI-POF, the transmission speed is only 155Mbps because the optical signal is transmitted by the total reflection method at the core / clad interface.

However, in the present invention, the GI-POF forming the refractive index distribution to produce a characteristic value up to 2.5Gbps transmission rate.

Regarding the method of manufacturing the refractive index-type plastic optical transmitter, that is, GI-POF, is the main content of the present invention.

MMA was used as a reagent grade. A small amount of polymerization inhibitor was washed with NaOH aqueous solution and purified water, dried over MgSO ₄ , and purified by reduced pressure distilation.

BPO used as an initiator was recrystallized with chloroform and Me-OH, and the purity was secured by purifying n-BM and various dopant substances, such as chain transfer agents.

First, a solution is prepared by mixing purified MMA, BPO (benzoyl peroxide) as an initiator and n-BM (normal butyl mercaptan) as a chain transfer agent. By making it into a polymer-sol state having a viscosity by an appropriate method, it is possible to reduce the density difference than to polymerize directly in the monomer mixture, thereby reducing the problem of molding failure or bubble generation due to volume shrinkage.

The dopant material having an appropriate refractive index is added to the monomer mixture or polymer sol thus treated and sealed together in a rod-shaped glass tube, followed by irradiation with UV light having a wavelength of 200-300 nm or polymerization using thermal energy such as IR. In this way, an optical carrier preform having a refractive index distribution is manufactured.

After the preparation of the preform, a POF having a diameter of 0.5-1.0 mm can be manufactured by a method of thermal drawing. As shown in FIG. 1, a drawing tower composed of a heating furnace, a preform supply part and a takeout part was manufactured and used.

The drawing temperature of the hot drawing furnace was 80-120 ° C centered on Tg and the preform feeding speed was about 5-20 mm / min.

The refractive index was measured by Photon kinetics & York Tech. Co., Ltd. PK-2600 was used, and as shown in FIG. 2, the continuous distribution of the refractive index was shown from the central axis of the preform to the outer surface. Transmission loss was measured by the cut-back method. The 650 nm LED lignt source was used.

The transmission rate was measured by the network analyzer by connecting the E / O and O / E converters to the POF terminated by the appropriate method.

Example 1

BB (bromo benzene), a dopant, was mixed in 100 parts by weight of MMA, 0.3 parts by weight of benzoyl peroxide (BPO) was used as an initiator, and 0.15 parts by weight of n-butyl mercaptan (n-BM) was added as a chain transfer agent. A polymer sol having a slight viscosity is prepared by leaving the polymerization reaction at a temperature of 40-60 ° C. for 1-12 hours.

This is placed in a rod-shaped polymer tube of 10-20 mm inner diameter and irradiated with UV or IR for 24 hours to form a preform having a refractive index distribution.

In order to remove the unreacted monomer which did not participate in the polymerization, heat treatment was performed at 105 ° C. for 24 hours in a vacuum oven.

When the preform is softened sufficiently in the heating furnace of a hot-drawing apparatus, the optical fiber flows naturally due to the characteristics of the thermoplastic resin. POF having a diameter of about 0.5-1.0 mm can be obtained by changing the conditions of the apparatus.

As shown in Table 1, it was confirmed that the refractive index distribution had a refractive index deviation of 0.005 to 0.020 from the center of the preform to the edge as shown in Table 1, and the refractive index distribution was maintained even when hot-drawn to produce POF.

The transmission loss of the POF showed the following values, and the transmission rate showed the characteristic value of up to 2.5Gbps.

Table 1

Item BB content Refractive index deviation Transmission loss (dB / km) Baud rate (Gbps) 5 0.005 130 1.0 10 0.008 135 1.8 20 0.015 136 2.5 30 0.020 138 2.1

Example 2

BEN (benzyl benzoate), a dopant, was mixed in 100 parts by weight of MMA, 0.3 parts by weight of benzoyl peroxide (BPO) was used as an initiator, and 0.15 parts of n-butyl mercaptan (n-BM) was added as a chain transfer agent. A polymer sol having a slight viscosity is prepared by leaving the polymerization reaction at a temperature of 40-60 ° C. for 1-12 hours.

This is placed in a rod-shaped polymer tube of 10-20 mm inner diameter and irradiated with UV or IR for 24 hours to form a preform having a refractive index distribution.

In order to remove the unreacted monomer which did not participate in the polymerization, heat treatment was performed at 105 ° C. for 24 hours in a vacuum oven.

When the preform is softened sufficiently in a heating furnace of a hot-drawing apparatus, the optical fiber flows naturally due to the properties of the thermoplastic resin. POF having a diameter of about 0.6-1.0 mm can be obtained by changing the conditions of the apparatus.

As shown in Table 2, the optical property was found to have a refractive index deviation of 0.007 to 0.024 from the center to the edge of the preform as a result of the measurement of the refractive index, and the refractive index distribution was maintained even when hot-drawn to produce POF.

As a result of the measurement, the transmission loss of POF showed the following value, and the transmission rate showed the characteristic value of maximum 2.0Gbps.

Table 2

Item BEN Content Refractive index deviation Transmission loss (dB / km) Baud rate (Gbps) 5 0.007 133 0.8 10 0.010 135 1.6 20 0.018 140 2.0 30 0.024 138 1.5

Example 3

BBP (benyl n-butyl phthalate), a dopant, is mixed with 100 parts by weight of MMA, and 0.3 parts by weight of benzoyl peroxide (BPO) is used as an initiator, and 0.15 parts by weight of n-butyl mercaptan (n-BM) is chained. A polymer sol having a slight viscosity is prepared by leaving it as a transfer agent and leaving it for about 1-12 hours at 40-60 ° C. so as not to complete the polymerization reaction.

This is placed in a rod-shaped polymer tube of 10-20 mm inner diameter and irradiated with UV or IR for 24 hours to form a preform having a refractive index distribution.

In order to remove the unreacted monomer which did not participate in the polymerization, heat treatment was performed at 105 ° C. for 24 hours in a vacuum oven.

The optical fiber flows naturally when the preform is softened sufficiently in the heating furnace of a hot-drawing apparatus, and naturally flows due to the characteristics of the thermoplastic resin. POF having a diameter of about 0.5-1.0 mm can be obtained by changing the conditions of the apparatus.

As shown in Table 3, the optical property was found to have a refractive index deviation of 0.004 to 0.017 from the center to the edge of the preform as a result of the measurement of the refractive index. The refractive index distribution was maintained even when hot-drawn to produce POF.

The transmission loss of the POF showed the following values and the transmission rate showed the characteristic value of maximum 1.5Gbps.

Table 3

Item BBP Content Refractive index deviation Transmission loss (dB / km) Baud rate (Gbps) 5 0.004 136 0.7 10 0.007 140 0.9 20 0.013 150 1.5 30 0.017 170 0.9

Example 4

Dopant PP (3-phenyl-1-propanol) was mixed with 100 parts by weight of MMA at a weight ratio of 5-30, 0.3 parts by weight of benzoyl peroxide (BPO) as an initiator, and 0.15 parts by weight of n-butyl mercaptan (n-BM). It was put as a chain transfer agent and left for about 1-12 hours at 40-60 ℃ so that the polymerization reaction is not completed, a polymer sol having a slight viscosity is prepared.

This is put into a rod-shaped polymer tube of 10-20 mm inner diameter and irradiated with UV or IR for 24 hours to form a preform having a refractive index distribution.

In order to remove unreacted monomers which did not participate in the polymerization, heat treatment was performed at 105 ° C. for 24 hours in a vacuum oven.

When the preform is softened sufficiently in the heating furnace of a hot-drawing apparatus, the optical fiber flows naturally due to the properties of the thermoplastic resin. POF having a diameter of about 0.6-0.8 mm can be obtained by changing the conditions of the apparatus.

As shown in Table 4, as a result of the measurement of the refractive index distribution, the refractive index was found to have a refractive index deviation of 0.003 to 0.014 from the center to the edge of the preform, and the refractive index distribution was maintained even when hot-drawn to produce POF.

The transmission loss of the POF showed the following values, and the transmission rate showed the characteristic value of maximum 1.4Gbps.

Table 4

Item PP Content Refractive index deviation Transmission loss (dB / km) Baud rate (Gbps) 5 0.003 140 0.4 10 0.005 145 0.9 20 0.010 146 1.3 30 0.014 155 1.4

Example 5

ODCB (o-dichloro benzene), a dopant, was mixed in 100 parts by weight of MMA, and 0.3 parts by weight of benzoyl peroxide (BPO) was used as an initiator, and 0.15 parts by weight of n-butyl mercaptan (n-butyl mercaptan) was transferred. A polymer sol having a slight viscosity is prepared when left at 40 -60 ° C for about 1-12 hours so as not to complete the polymerization reaction.

This is placed in a glass polymer rod-shaped polymer tube with an inner diameter of 10 -20 mm and polymerized for about 24 hours by irradiation with UV or IR to form a preform having a refractive index distribution.

In order to remove the unreacted monomer which did not participate in the polymerization, heat treatment was performed by placing the vacuum oven at 105 ° C. for 24 hours.

When the preform is softened sufficiently in the heating furnace of a hot-drawing apparatus, the optical fiber flows naturally due to the properties of the thermoplastic resin. POF having a diameter of about 0.5-0.9 mm can be obtained by changing the conditions of the apparatus.

As shown in Table 5, the optical property was found to have a refractive index deviation of 0.005 to 0.019 from the center to the edge of the preform as a result of the refractive index distribution, and the refractive index distribution was maintained even when hot-drawn to produce POF.

The transmission loss of POF showed the following values, and the transmission rate showed the characteristic value of maximum 2.5Gbps.

Table 5

Item OCDB Content Refractive index deviation Transmission loss (dB / km) Baud rate (Gbps) 5 0.005 130 1.3 10 0.008 134 2.0 20 0.014 138 2.5 30 0.019 142 1.8

As described above, in the present invention, a polymer sol is formed by adding 0.01-50 parts by weight of a dopant which is a non-reactive substance, a crosslinking initiator and a chain transfer agent to 100 parts by weight of methyl methacrylate, and then injected into a rod-type polymerization tube and UV ( After carrying out the polymerization reaction by an ultraviolet (UV) light source or an IR (infrared ray) light source, a preform having a continuous refractive index distribution is produced, thereby providing an effect of enabling high-speed data transmission.

Claims (1)

0.01-50 parts by weight of a dopant which is a non-reactive substance, a crosslinking initiator, and a chain transfer agent are added to 100 parts by weight of methyl methacrylate to form a polymer sol, which is injected into a rod-shaped polymerization tube, and is irradiated with UV (ultraviolet) light or IR (infrared). After the polymerization by the light source to form a light transmission preform having a radial gradient gradient (concentration gradient), the preform is thermally stretched to produce a plastic optical fiber having a continuous refractive index distribution The manufacturing method of the plastic optical transmission body which has a refractive index distribution made into.