JPS63204234A - Plastic optical fiber - Google Patents

Abstract

PURPOSE:To obtain an effective nonlinear optical element by forming a core part having the refractive index higher than the refractive index of a clad to <=100mum diameter. CONSTITUTION:The core part 1 having the refractive index higher than the refractive index of the clad of a plastic optical fiber having the core 1 consisting of a synthetic high-polymer material and the clad 2 is formed to <=100mum diameter. An org. material having large nonlinear sensitivities beta, gamma is dispersed into the synthetic high-polymer material of the core part or is incorporated into the repeating unit of the synthetic high-polymer in the core part. The org. material having the large nonlinear sensitivities beta, gamma refer to an arom. compd., incorporated with a long chain conjugation system in the molecular structure and a compd. which consists of alkyne, alkene, etc., as skeleton and is added with an electron withdrawing group such as NO2, CN or CHO, and NR2 (R denotes hydrogen or alkyl group), OH or OCH3. A nonlinear optical effect is thereby obtd. with a low input.

Description

[Detailed Description of the Invention] [Industrial Field of Application] The present invention relates to a plastic fiber that can exhibit a nonlinear optical effect and can be used in the field of optical communication or information processing. The plastic original fiber has a large core diameter,
A large relative refractive index difference (typically a core diameter of 500 μm)
The advantageous features of the introduction of the oscillator were emphasized in terms of the relative refractive index difference (around 5% between the front and back). Considering that the original linearity of organic materials is greater than that of silica-based glass materials, it is very effective to use such conventional plastic fibers as a device for producing nonlinear optical effects in place of silica-based fibers. is.

[Problem that the invention seeks to solve]

However, as mentioned above, conventional plastic fibers have large core diameters and relative refractive index differences, and the original power density cannot be large, so they cannot produce effective nonlinear optical effects. It has the disadvantage that it is difficult to use it as a component of a chemical element.

In addition, many similar fiber-type nonlinear optical elements using silica glass have been announced, but since the nonlinearity of silica glass itself is very small, it is difficult to produce an effective nonlinear optical effect without using a high-power source. It had the disadvantage that it needed to be incident on the

An object of the present invention is to provide an effective nonlinear optical element.

[Means for solving problems]

To summarize the present invention, the present invention relates to a plastic optical fiber having a core and a cladding made of a synthetic polymer material, in which the diameter of the core portion having a refractive index p higher than that of the cladding is 100 μm.
m or less.

The efficiency of nonlinear optical effects depends on the power intensity of incident light. It is an effective method to increase the effective power density of incident light by making a nonlinear optical material into a waveguide due to the original confinement effect, and to cause a nonlinear optical effect with a low input. The value of third-order nonlinear susceptibility z(6) of glass is 10” esu
Despite its small size, the input source is only a few W, and the core diameter is 10μ.
An effective third-order nonlinear optical effect has been observed for silica-based glass original fibers with lengths of less than m or several meters [for example, R
, H, Storen (R,H.

5tO1θn) and others, Applied Physics Letters (Appl, Phys, Letts, ) 22nd
Vol. 6, p. 294 (1973)). In plastic optical fibers, an organic material forms the core, and some organic materials have been reported to have z(3) two orders of magnitude larger than that of silica glass (for example, organic nonlinear optical materials Kato and Nakahama). CMC 1985).

From the above, by setting the core diameter of a plastic optical fiber with an organic material as the core to 100 μm or less, effective nonlinear optical effects similar to those observed in silica-based original fibers can be achieved with a power of several watts at a fiber speed of less than m. It can be observed at the input source. The core diameter of this plastic optical fiber is 1
Even if the fiber length exceeds 00 μm, it is possible to produce a nonlinear optical effect by increasing the fiber length to several tens of meters or more or by increasing the input source to several tens of W or more, but the loss due to the length of the plastic optical fiber Considering the increase in power consumption or the use of current semiconductor lasers as input sources, it is difficult to generally use semiconductor lasers with a power of several tens of W or more.
In order to provide a practical nonlinear optical element using a plastic optical fiber, it is necessary that the core diameter be 100 μm or less.

FIG. 1-1 is a cross-sectional view of a plastic optical fiber that has been cleaved according to the present invention, in which reference numeral 1 indicates the core and 2 indicates the cladding. Figures 1-2 are graphs showing an example of the refractive index distribution of the core and cladding diameters of the plastic optical fiber of the present invention.
The relative refractive index difference is shown for the case of [1.2%]. In other words, Figure 1-2 shows the fiber diameter (μm, horizontal axis)
It is a graph showing the relationship between the refractive index n (vertical axis) and the refractive index n (vertical axis).

In the present invention, organic substances with large nonlinear susceptibilities β and γ that are included as repeating units in dispersed or synthesized polymers include aromatic compounds containing long-chain conjugated systems in their molecular structures, alkynes, alkenes, etc. as skeletons; No, CN
, CHO, and other electron-withdrawing groups, and compounds to which electron-donating groups such as NR, (R represents hydrogen or an alkyl group), OH, and 0CHs can be used.

In addition to the example of dispersing organic substances in plastic, for example, as shown in the reaction formula below, organic substances with large nonlinear susceptibilities β and γ are bonded to molecules that have polymerization ability, and then monomers are polymerized to make them into polymers to create plastic optical fibers. It can also be used as a core material.

Alternatively, as shown in the formula below, monomers are first polymerized, and then organic molecules with large nonlinear susceptibilities β and γ are combined,
This polymer material can be used as a core material of a glass original fiber.

O2 In the plastic original fiber of the present invention, the core diameter is 1
Since it is very small, 00 μm or less, the original power density becomes effectively large, and it is possible to exhibit nonlinearity with a lower original power than conventional plastic fibers.

Applications such as light sources using linear optical effects, such as stimulated Raman, and source-to-source switches using the original Kerr effect can be considered, and the effects of the present invention can of course be realized using the materials, manufacturing methods, etc. listed in the examples. It is not limited to. Further, it goes without saying that the plastic fiber in the present invention can be applied as a light guide path exhibiting physical properties other than nonlinear optical effects.

Next, one example of the method for producing the glass original fiber of the present invention will be described. FIG. 2 shows a manufacturing process diagram. In FIG. 2, numeral 3 is a core base material, 4 is a clad base material,
5 means a wire drawing base material, and 6 means a wire drawing furnace. First, a normal plastic core fiber (core diameter of about 500 μm) was fabricated using a method such as that reported in Japanese Patent Application Laid-Open No. 57-81205, and the length was 20 tons. Cut into approximately n pieces [Figure 2 (A)]. Next, as shown in (A), a plastic cylinder having a refractive index p smaller than that of the plastic core fiber is manufactured [Fig. 2 (A)]. Next, a plastic core fiber is inserted into the large part of this cylinder. After injecting a monomer that provides the same plastic material as both spare cylinders [Figure 2 (1)], the cylinder and core fiber are integrated by polymerizing the monomer [Figure 2 (1)] ]. Finally, this integrated plastic solid solution was melt-extruded and drawn while heating to obtain a plastic original fiber according to the present invention.

〔Example〕

The production and operation of the plastic original fiber according to the present invention will be specifically described below, but the present invention is not limited to these examples.

Example 1 First, an ordinary plastic core fiber (core diameter 500 μfn) is produced from methyl methacrylate monomer. Next, a cylindrical rod is produced from a copolymer of polymethyl methacrylate and polyfluoroalkyl methacrylate (mixing ratio 99:.1). The prepared cylindrical rod (
A hole (outer diameter 50 cm, outer diameter 510 μtn) is drilled and wire drawn according to the manufacturing method example shown in FIG. The fiber shape of the glass original fiber thus produced had a core diameter of 5 μm and an outer diameter of 500 μm. A dye laser source (wavelength [154 Am,
Original power: 50. When OmW ) was incident, a self-phase modulation effect could be observed. The change in the waveform of the incident light is measured as shown in Figure 3-1.
The results shown in Figure 2 were obtained. In FIG. 3-1, numeral 7 is the plastic fiber of the present invention, 8 is the spectral width before incidence, 9 is the spectral width after incidence, and 10 is Nd:
means YAG laser. In addition, Figure 5-2 shows the input source intensity (arbitrary unit, horizontal axis) and spectral width (arbitrary unit,
It is a graph showing the relationship with the vertical axis).

Example 2 Approximately 20 m of plastic core fiber with a fiber diameter of 500 μm was prepared from a base material in which α1% by weight of 4-nitro-4'-dimethylaminostilbene was dissolved together with a predetermined amount of a polymerization initiator and a chain transfer agent in a methyl methacrylate monomer solution. do.

Next, the plastic core fiber was inserted into a polymethyl methacrylate cylinder prepared in the same manner as in Example 1. Furthermore, methyl methacrylate monomer and a predetermined amount of additives were all injected into the gap between the cylinder and the fiber, and the glass optical fiber was fixed in the cylinder by leaving it at 130° C. for 6 hours in a nitrogen gas atmosphere. Thereafter, the fiber and tube were completely integrated by being left at 160° C. for 6 hours.

Next, one end of this cylindrical plastic solid solution was heated to 200°C.
The wire is drawn by extrusion under pressure while applying a certain amount of heat. The glass optical fiber of the present invention was obtained by controlling the outer diameter to 500 μm. The core diameter of this original fiber was 5 μm.

The outer diameter was 500 μm, and the relative refraction -a was 2%.

When a laser source (wavelength: α63 μm, peak power 5 mW) was input into 1 m of this fiber from the fiber end, a self-phase modulation effect could be observed.

Example 3 A core base material containing about 2% of 2-methyl-4-nitroaniline was prepared, and a glass optical fiber of the present invention was obtained in the same manner as in Example 1 (core diameter: 5 μm, outer diameter: 4
50/jm, relative refractive index difference 0.2%, length 10 m)
.

A laser source (wavelength: 1.06 μm) is attached to this fiber.

When a peak power of 5 mW) was input from the fiber end, the generation of second harmonics was observed. As for efficiency, α
It was about 5%.

〔Effect of the invention〕

As explained above, the glass optical fiber according to the present invention uses an organic material that has a very large nonlinear optical effect as a core, and furthermore, the difference in refractive index relative to the core diameter can be made small, so that effective power density can be obtained. Therefore, it is an effective nonlinear optical element, and has the advantage of having a shorter effective length and requiring less optical power than conventional nonlinear optical elements using silica fibers.

[Brief explanation of the drawing]

FIG. 1-1 is a cross-sectional view of the plastic optical fiber of the present invention, and FIG. 1-2 is a graph showing the relationship between the diameter of the core and cladding and the refractive index of an example of the plastic optical fiber of the present invention.
FIG. 2 is a process diagram of an example of the method for producing a glass optical fiber of the present invention, FIG. 3-1 is a schematic diagram of a method for observing the self-phase modulation effect using the glass optical fiber of the present invention, FIG. 3-2 is a graph showing the relationship between the input source intensity and the spectral width of an example of the glass optical fiber of the present invention according to FIG. 3-1.

Claims (1)

[Scope of Claims] 1. A plastic optical fiber having a core and a cladding made of a synthetic polymer material, wherein the diameter of the core portion having a higher refractive index than that of the cladding is 100 μm or less. 2. The plastic optical fiber according to claim 1, wherein organic substances with large nonlinear susceptibilities β and γ are dispersed in the synthetic polymer material of the core portion. 3. The plastic optical fiber according to claim 1, wherein the organic substance having large nonlinear susceptibilities β and γ is contained in the repeating unit of the synthetic polymer in the core portion.