KR20040026766A - Multiple-Core Plastic Optical Fiber - Google Patents

Abstract

PURPOSE: A multi core plastic optical fiber, a parallel optical communication connection structure using the same and a method for manufacturing the same are provided, in which a manufacturing method is simple and the geometrical numerical value and structure constant are maintained. CONSTITUTION: A multi core plastic optical fiber(1) includes a core(10) for transmitting an optical signal and a cladding(12) for encompassing the core(10). The core(10) and the cladding(12) are made of a high molecular plastic material as a single plastic optical fiber. The multi core plastic optical fiber(1) is characterized in that a plurality of cores is formed in parallel to each other with spacing at a predetermined distance and each of the cores transmits an optical signal in parallel as an independent waveguide.

Description

Multi-core plastic optical fiber, parallel optical communication connection structure using the same and manufacturing method thereof {Multiple-Core Plastic Optical Fiber}

The present invention relates to an optical fiber used as a transmission line of optical communication, and more particularly, to a plastic optical fiber made of a polymer plastic.

The optical fiber is composed of a fiber core that transmits light and a cladding that allows the light to be constrained to the core with a lower refractive index than the core.

Fiber optics are often fabricated by stretching fiber substrates at high temperatures after fabricating a fiber preform.

Usually, the diameter of the base material is more than 50mm and the diameter of the optical fiber is in the range of 100 to 1000 micrometers (µm).

While a conventional optical fiber is made of pure silica glass (SiO ₂ ), the material is expensive and not easy to process, whereas an optical fiber made of plastic is relatively inexpensive and easily processed.

In addition, plastics have an advantage that they can be handled more easily because they are more flexible and have better mechanical properties than silica.

Parallel optical communication, on the other hand, is often spotlighted in areas such as short-range optical communication networks or board-level optical interconnections within a system (Davis H. Hartman, "Use of guided wave optics for board level"). and mainframe level interconnects ", Preceedings of 41st Electronic Components and Technology Conference, p. 463-474, 1991).

In parallel optical communication, 8-bit and 16-bit parallel signals must be transmitted at a transmission rate of several tens of megabits per second (Mbps) or hundreds of Mbps per channel at a distance of several tens of centimeters to several meters.

The parallel optical connection is expected to increase gradually because the crosstalk (signal cross-talk) is smaller than the electrical parallel communication and is not affected by external electromagnetic fields.

In particular, a vertical cavity surface emitting laser (VCSEL) has been developed as a light emitting device, and research into a method of parallel optical connection through a plurality of arrays of lasers has been actively conducted.

Two methods are attracting attention as a transmission medium for this purpose.

One is to bundle several optical fibers together into a bundle, and the other is to use a film engraved with a plastic planar waveguide.

A fiber bundle is a ribbon fiber that arranges optical fibers in one dimension, and an image fiber mainly used in endoscopes by arranging thousands of small fibers in two dimensions. Is being considered.

In the case of optical connection through the optical fiber bundle, the cost is high because the optical fiber must be bundled very precisely, and as the number of optical fibers to be bundled increases, that is, as the number of bits of parallel data increases.

However, because optical attenuation is small, the optical fiber is advantageous in that it can send a signal farther and can be used at distances of several tens of meters or more.

Plastic planar waveguides are cheaper in that the values of each waveguide are determined at design time, and these values are ensured at the time of manufacture, eliminating the need for additional bundling.

In particular, increasing the number of waveguides does not increase the cost, which is advantageous for higher bit number parallel connection.

However, since the length of the planar waveguide is determined at the time of manufacture, it is impossible to manufacture a length of more than 1m. Moreover, since the light attenuation is relatively large, it is disadvantageous for long distance transmission and is usually useful only within a distance of 1m.

On the other hand, multi-core optical fibers have been proposed for use in parallel optical communication (B. Rosinski et al, "Multichannel transmissin of a multicore fiber coupled with vertical-cavity surface-emitting lasers", Journal of Lightwave Technology, Vol. 17, No. 5, 1999).

Such multi-core optical fibers can be said to be very effective for parallel optical communication because each core can independently transmit optical signals and the geometry between cores can be secured at the same time during the manufacturing process.

That is, it has secured both the small optical attenuation, which is the advantage of the optical fiber bundle, and the precision and low cost, which are the advantages of the planar waveguide.

The multi-core optical fiber bundles a plurality of silica optical fiber base materials and draws them to produce a silica optical fiber having a multi-core structure.

The method of tying the base material is not efficient because the numerical value may change during the tensile process and each core must go through the base material manufacturing process separately.

The ideal method is to make multiple cores at once, but it is not practical because of the low processability of silica.

In addition, glass optical fiber is inferior to plastic because of its inferior mechanical property, and is not suitable for short-range parallel optical communication such as optical connection between boards.

As mentioned above, multi-core fiber optics are a very attractive transmission medium for short-range parallel optical communication if they solve the manufacturing difficulties and improve material properties.

The present invention has been made to solve the above problems, an object of the present invention is to propose a multi-core plastic optical fiber of plastic material to solve the problems of the multi-core optical fiber to improve its manufacturing method and use method, through An optical transmission medium to be effectively used in parallel optical communication.

In order to achieve the above object, the present invention provides an optical fiber comprising a core for transmitting an optical signal and a cladding having a lower refractive index than the core and surrounding the core; The core and the cladding are inseparable single plastic optical fibers made of a polymer plastic material, and a plurality of cores spaced apart from each other with the cladding formed therebetween are parallel to each other so that each core is an independent waveguide. To provide a multi-core plastic optical fiber characterized in that the transmission to.

In order to achieve the above object, the present invention also provides an optical communication system for connecting a light source for generating an optical signal and a light receiving element for receiving and converting the optical signal into an electrical signal; Between the light source array in which two or more light sources are arranged and the light receiving element array in which the number of light sources is equal to the number of light sources, the multi-core plastic optical fiber of claim 1 is connected so that an optical signal from one light source is one-to-one. To provide a parallel optical communication connection structure characterized in that the transmission to a single optical receiver.

In order to achieve the above object, the present invention also manufactures a base material comprising a cladding structure surrounding a core and a plurality of cores made of a polymer plastic material, and drawing an optical fiber by drawing from one side while applying heat to the base material. To provide a multi-core plastic optical fiber manufacturing method characterized in that.

1 is a cross-sectional view of a multicore plastic optical fiber according to the present invention.

2 is a block diagram of a parallel optical communication system using a multi-core plastic optical fiber according to the present invention.

3 is a view showing a method for connecting a multi-core plastic optical fiber according to the present invention.

4 is a view showing a rod insertion process of the cylindrical hole-rod insertion method of manufacturing a multi-core plastic optical fiber according to the present invention.

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

1,1a, 1b: Multicore Plastic Optical Fiber

2: light source arrangement 3: light source lens

4: light receiving lens 5: light receiving element array

10,10a, 10b: Core 12: cladding

14, 14a, 14b: connection cavity 16: connection pin

18: ferrule for connection 20: hole for core

22: rod for core

Hereinafter, with reference to the accompanying drawings an embodiment of the present invention will be described the configuration and description.

Figure 1 shows a cross-sectional view of a multi-core plastic optical fiber proposed by the present invention.

The optical signal is transmitted through the core 10, and the core 10 may have an array of 2 × 4 as shown in FIG. 1, or may form various arrangements as desired.

In addition, the refractive index of the core 10 may have a step-index profile having only one refractive index, and may have a graded-index profile having a high center in the cross-sectional axis and a low peripheral portion.

When having the hill-shaped refractive index can be obtained more than five times the bandwidth shape than the stepped.

The cladding 12 has a lower refractive index than the core 10 so that light (a light signal) is transmitted only through the core 10.

A connection hollow hole (14) is a hollow hole made along the optical fiber 1, which is used to orient the optical fiber 1 through the hole to make a connector at the end.

Also, when the optical fiber 1 is viewed from the side, the connecting cavity 14 inside the optical fiber becomes visibly observable due to its low refractive index (the refractive index of the air).

In other words, it is possible to easily estimate the arrangement angle of the multiple core arrangement in the optical fiber.

This can be used to align the connection angles between two multicore optical fibers or multicore optical fibers and light source arrays or arrays of light receiving elements, allowing each core to send and receive light in place.

As described above, in the plastic optical fiber having a plurality of cores according to the present invention, in the plastic optical fiber in which the core 10 and the cladding 12 are made of polymer or plastic, cores for transmitting two or more optical signals are uniform. The plurality of cores are arranged in parallel, and the cores are surrounded by cladding having a lower refractive index than the cores.

Each of the cores 10 transmits optical signals in parallel as independent waveguides.

Therefore, each core should act as a single transmission channel with each other and be sufficiently separated from each other so that there is no optical coupling between them and leave a gap of at least 10 micrometers.

In the present invention, the diameter of each core 10 is 50 to 200 micrometers, and the distance between the cores 10 is 100 to 300 micrometers.

The spacing between the cores is suitable for compatibility with common silica glass optical fibers from 120 to 130 micrometers or from 245 to 255 micrometers.

The difference in refractive index between the core 10 and the cladding 12 is 1 to 3%, so that the core has multimode and the optical coupling between the cores is negligible.

In addition, these cores may be in the form of supporting only a single mode, or may transmit multiple modes, but in a general parallel optical communication, it is advantageous to transmit in multiple modes to increase the size of the core.

2 is a block diagram of a parallel optical communication system using a multi-core plastic optical fiber according to the present invention.

The light source array 2 is a structure in which a plurality of light sources are arranged. Here, the array of 2x4 is taken as an example.

The light source lens 3 efficiently guides the optical signal from the light source to the multi-core plastic optical fiber 1 according to the present invention.

Herein, the optical signals emitted from each light source are incident to each core 10 independently.

The light receiving lens 4 guides the transmitted light to the light receiving element in the multi-core plastic optical fiber 1 according to the present invention.

The light receiving element array 5 independently receives the optical signals transmitted through the respective cores 10 and converts them into electrical signals.

3 is a view showing a method for connecting a multi-core plastic optical fiber according to the present invention.

The multi-core plastic optical fibers 1a and 1b on the right side and the left side are connected to each other to increase the transmission distance.

The connecting pins 16 are inserted into the right and left connecting cavities 14a and 14b so as to accurately grasp the direction and position.

By fitting the connecting pins 16 to the connecting cavities 14a and 14b in this way, the core 10a of the right optical fiber and the core 10b of the left optical fiber are well aligned with each other.

The connecting ferrule 18 holds the two optical fibers 1a and 1b from the outside to prevent them from moving.

On the other hand, for the purpose of improving the transmission bandwidth of the multi-mode optical fiber, a multi-core plastic optical fiber has been previously disclosed (US Patent 4,300,816, "Wide band multicore optical fiber" / US 6,188,824, "Optical signal transmission multicore plastic optical fiber"). .

However, these multi-core plastic optical fibers are not intended to convey independent information to each core, but to attempt to improve transmission bandwidth by simply reducing the size of the core and reducing the number of transmitted modes.

That is, even though there are multiple cores, they all transmit the same signal.

Therefore, it can be seen from the following description that the difference in terms of the effect according to the present invention.

The preform drawing method is used to fabricate the multi-core plastic optical fiber according to the present invention.

The structure of the core and cladding is made to be fully fabricated from the integrated base material before tensioning, and its geometry is maintained by drawing on one side while applying heat to the base material.

And it is controlled to keep the whole diameter of the optical fiber constant during tensioning.

The control of the diameter in tension of the optical fiber is currently a mature (known) technique that can only tolerate an error of less than 1%, as in conventional plastic planar waveguides, the geometry between each waveguide is consistently guaranteed at the time of manufacture.

In addition, the drawing process is the same as the optical fiber manufacturing process up to now, except that the base material is manufactured from the conventional base material manufacturing in that the structure of the core and cladding must be manufactured.

The base material can be produced by one of the following methods.

First, there is a method of manufacturing the cladding part of the base material first and the core part therein, and second, the method of manufacturing the core part first and the cladding part therein.

The first method of manufacturing the cladding of the base metal, which is the former, may be further classified as follows.

Firstly, the first method is to make a cylindrical cladding part and make a hole in it to make a space for the core part, and second, to manufacture a cladding part by forming a mold so that there is a hole for the core. have.

And in making the core in the hole of the cladding cylinder thus created, first, simply insert the cylinder rod for the pre-fabricated core, and second, put the monomer in the hole of the fabricated cladding cylinder and polymerize it. There is this.

That is, in the method of first making the cladding of the base material according to the present invention, a total of four methods exist.

Herein, the present invention is an optimized method, in which a cylinder or body forming a cladding portion of a base material is formed and a hole for forming a core portion is formed therein, wherein a cylindrical rod for a core of a solid state prepared in advance is inserted into the hole. -Bar insertion method ".

The cylindrical hole-rod insertion method is particularly advantageous for the production of multi-core optical fibers having stepped refractive indices because the cladding portion and the core portion are manufactured separately, and thus the productivity is high and the desired index distribution can be easily given to the rod for the core.

4 is a view showing a rod insertion process of the cylindrical hole-rod insertion method of manufacturing a multi-core plastic optical fiber according to the present invention.

The fabricated cylindrical cladding 12 has a 2 × 4 core hole 20 and one connecting cavity 14 in the figure.

The core hole 20 may be made by molding the cladding 12 or may be made by machining a hole in a cylinder.

The core rod 22 is a solid cylindrical rod inserted into the core hole 20 and is made of plastic having a higher refractive index than the cladding 12.

When the rod 22 for the core is inserted into the hole 20 for the core, a slight gap is formed between the core hole 20 and the core rod 22. The void forms a polymer that can be easily cured. It may be inserted and cured, or the base material with pores may be drawn to automatically fill the pores.

This not only reduces the time it takes to polymerize the core 10 but also makes it very easy to give a graded-index profile to increase the bandwidth of the optical fiber.

That is, the core rod 22 may be manufactured in advance so as to form a hill-shaped refractive index where the center has a high refractive index in the cross section orthogonal to the rod axis and gradually decreases the refractive index toward the periphery.

By inserting the core rods 22 into the base cladding portion core holes 20 in the above-described manner, voids are generated. These voids may be refilled, but they may be retracted and filled automatically during the tensioning process even when drawn without filling.

Manufacturing multicore plastic optical fibers with this process is efficient in terms of manufacturing time and cost.

In order to facilitate the connection between the multi-core plastic optical fibers (1) or the optical fiber (1) and the light source array (2) or the light receiving element array (5), etc., formed in parallel to the core 10 in the multi-core plastic optical fiber The connecting cavity 14 is produced by pulling without filling the empty hole in the base material.

In this case, a polymer having a relatively high molecular weight is coated around the hollow hole so that the hole is not easily filled, thereby creating a more precise connection cavity.

Since the multi-core plastic optical fiber 1 cannot be distinguished in directionality when viewed from the outside, a connection cavity 14 is utilized to hold an appropriate position of each core 10, and the connection cavity is a female part of the connection part. ), You can connect more easily.

The connecting cavity 14 is optionally employed as it is independent of the basic function of the multi-core plastic optical fiber 1.

On the other hand, the above-described method of making the core portion first and then cladding, the first manufacturing the rod 22 for the core, the core rods are arranged in a cylindrical container in a state in which the rod constant for the core ( When the monomer is added and polymerized, the cladding 12 is formed outside the core rod.

This method can also improve the transmission bandwidth by allowing the core rod to have a hill-shaped refractive index.

In addition, the multi-core plastic optical fiber may be manufactured by an extrusion method, which is another method of manufacturing the plastic optical fiber, not the base metal-tensile method.

That is, when a plurality of cores are extruded by the nozzle, the cladding is also extruded separately, thereby forming the core and cladding structure of the multi-core optical fiber.

As described above, the multi-core plastic optical fiber according to the present invention is very simple to manufacture, its geometry and structure are ensured very consistently, and the optical waveguide has a constant shape compared to the conventional plastic flat waveguide, so that less optical You have attenuation, and you can have multiple communication channels at once.

In addition, since the conventional plastic planar waveguides must be arranged in a planar waveguide, the total width thereof becomes excessively wider as the number thereof increases, whereas the multicore plastic optical fiber can form cores in two dimensions, thereby forming up to 100 cores or more.

In the case of transparent polymers, the optical attenuation can be within 200dB / Km at 650nm wavelength, allowing parallel data transmission up to 50m at that wavelength.

Since the transmission speed of each channel is 100Mbps or more, when the number of cores is 10x10 and 100, the total transmission capacity will be more than 10Gbps, and it can transmit more than 50m.

In addition, compared with the conventional glass multi-core plastic optical fiber, the light attenuation is larger than the glass, but its manufacturing is very easy and can guarantee a precise value, and because of the nature of the plastic material can be more useful in a short distance.

The multi-core plastic optical fiber according to the present invention described above will be useful for short distance parallel data transmission in the future, especially for transmission medium of parallel bus within 50m or less in electronic system.

Claims (13)

An optical fiber comprising a core for transmitting an optical signal and a cladding having a lower refractive index than the core and surrounding the core; The core and the cladding are inseparable single plastic optical fibers made of a polymer plastic material, and a plurality of cores spaced apart from each other with the cladding interposed therebetween are formed in parallel to each other so that each core is an independent waveguide. Multi-core plastic optical fiber characterized in that the transmission. The method of claim 1, wherein the refractive index distribution of the core, A multi-core plastic optical fiber characterized by a high center of gravity and a sloped refractive index that gradually decreases toward the periphery, extending its transmission bandwidth. The multicore plastic optical fiber of claim 1, wherein the spacing between the cores is between 245 and 255 micrometers, the core diameter is between 50 and 200 micrometers, and the refractive index difference between the core and the cladding is between 1 and 3%. The multicore plastic optical fiber of claim 1, wherein the spacing between the cores is 120 to 130 micrometers, the core diameter is 50 to 200 micrometers, and the refractive index difference between the core and the cladding is between 1 and 3%. The multi-core plastic optical fiber of claim 1, wherein at least one connection cavity is formed in the cladding portion in parallel with the core. An optical communication system for connecting a light source for generating an optical signal and a light receiving element for receiving and converting the optical signal into an electrical signal; Between the light source array in which two or more light sources are arranged and the light receiving element array in which the number of light sources is equal to the number of light sources, the multi-core plastic optical fiber of claim 1 is connected so that an optical signal from one light source is one-to-one. Parallel optical communication connection structure characterized in that the transmission to a single optical receiver. The method of claim 6, wherein when the cladding is formed with at least one connection cavity in a form parallel to the core, to connect two of the same multi-core plastic optical fiber or the multi-core plastic optical fiber and the light source arrangement or array of light receiving elements, And a connection pin is inserted into the connection cavity, so that the multi-core plastic optical fiber accurately noises direction and position. In manufacturing the multi-core plastic optical fiber of claim 1, to prepare a base material consisting of a plurality of cores and a cladding structure surrounding the core, made of a polymer plastic material, by drawing from one side while applying heat to the base material to produce an optical fiber Multi-core plastic optical fiber manufacturing method characterized in that. The method according to claim 8, wherein the core is formed of a cladding formed with a plurality, the core rod having the same diameter or smaller than the core hole is inserted into the core hole to leave a gap between the core hole and the core rod. A method of manufacturing a multi-core plastic optical fiber characterized in that the base material is manufactured by fixing it with one holding. The method of claim 9, wherein a gap is formed between the core hole and the core rod, Method of manufacturing a multi-core plastic optical fiber, characterized in that the filling by inserting a polymer material into the voids, or by curing the base material. The base material of claim 8, wherein a core rod is formed to form the core, and a plurality of core rods are arranged inside the container, whereby a polymer material is polymerized in the container to form a cladding to prepare a base material. Multi-core plastic optical fiber manufacturing method characterized in that. 12. The method according to claim 9 or 11, wherein if the core each has a plurality of optical transmission modes, so that the optical refractive index distribution has a high refractive index at the center of the cross section orthogonal to the rod axis and has a hill-shaped refractive index gradually decreases toward the periphery A method for manufacturing a multi-core plastic optical fiber, comprising manufacturing a core rod and manufacturing a base material of a hill-type refractive index multi-core plastic optical fiber. The method of manufacturing a multi-core plastic optical fiber according to claim 9 or 11, wherein a hollow hole parallel to the core is formed in the cladding of the base material and a tension is formed without filling the empty hole in the base material.