JPS58158606A - Optical transmission line of far infrared light - Google Patents

Abstract

PURPOSE:To form an optical transmission line for far-infrared light which has less loss by providing a plastic layer which has an index of refraction equal to that of a dielectric on either of the internal and external surfaces of the dielectric as a pipe material, and obtaining a specific relation among the thickness of the plastic layer, thickness of the dielectric, wavelength of far-infrared light, and indexes of refraction of the dielectric and plastic layer corresponding to said wavelength. CONSTITUTION:On either of the external and internal surfaces of the dielectric 2 as the pipe material, the plastic layer 1 having the index of refraction equal to that of the dielectric is provided. Then, the equation holds, where t2 and t1 are the thicknesses of the plastic layer 1 and dielectric, lambda and (n) are the wavelength of far-infrared light and the index of reflection of the dielectric and plastic layer 1 corresponding to the wavelength lambda, and (m) is a constant.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to an optical transmission line, and particularly to a far-infrared optical transmission line.

Currently, the following two systems are mainly used as far-infrared light transmission lines. One is an optical fiber system made of a heavy metal oxide system, a chalcogenide system, or a logenide system, and the other is a hollow waveguide system. .

FIG. 1 is a diagram showing the transmission range of the material used in the optical fiber system. From this figure, the L sea urchin is 8 μm,
In the far-infrared wavelength range of +>10, there are very few materials that allow the light to pass through. For example, CO21/-the light 10,6μm
There are about 6 types of old materials that allow light to pass through. Furthermore, the number of these materials that actually become glassy and become fibers is very small (limited to C). More often than not, it goes around 1-.

For example, the theoretical transmission loss value of Ge53 is 1O-2dB
/, but in the W shape it is about 360 dB/. It's called KH2-5] B r -T
The theoretical transmission loss of polycrystalline optical fiber for IT is 10 to 10 dB/km, but currently it is 3.
There is one at 778 degrees at 0 oaB/. Among these lunar phases, KH2-5 is considered to be the most promising, but it has many problems such as the manufacturing method and the toxicity of the materials.

On the other hand, in the latter hollow waveguide method, far-infrared light is introduced between two metal plates. For example, for a hollow waveguide designed for 10.6 μm light, one made of two aluminum plates has been proposed. When the width of the hollow part that guides this wavelength light is 0.4 x 6, the output is 200 W when it is transmitted for 1.2 m, but the transmittance at this time is 80
%.

However, since the material constituting this waveguide is a metal plate, it has a problem of low surface thermal properties and large transmission loss due to structural non-uniformity.

The present invention aims to eliminate the drawbacks of the prior art described in section 2 and provide a far-infrared optical transmission line with a simple structure that is low loss and durable. A plastic layer having a refractive index equal to that of the dielectric is provided on at least one of the inner and outer surfaces, L7st of the plastic layer, tl the thickness of the dielectric, and λ the wavelength of far-infrared light.
, the refractive index of the dielectric and plastic layers at wavelength 2 is n1, and the constant m is 1, +1. , -s(n2-1)-am holds true.

FIG. 2f:j is a sectional view of a frozen infrared transmission line which is an embodiment of the present invention. 1 is quartz glass, and 2 is silicone resin. That is, a plastic reinforcing layer of resin 2 having the same refractive index is provided on the inner surface of the Ishiya glass tube 1, which is a dielectric material and has a thickness of L2, and the thickness is set to t and tl.

FIG. 3 is a sectional view of an infrared transmission line according to another embodiment of the present invention. This is also an example of a hollow waveguide, and 3 is a tube made of a dielectric material. In this conventional method, the dielectric constant (
Electromagnetic power was transmitted by concentrating it on a dielectric material with a large refractive index, but in this case, the loss due to the dielectric material determines the transmission loss of the transmission path. therefore,
If a dielectric material with high deterioration is used, the transmission loss will be large.

In addition, it is possible to use two dielectric layers to increase the degree of freedom in designing transmission paths, but since most of the transmitted power is in the dielectric layer, the state of the interface between the two layers may be disturbed. It is thought that changes in layer j7 and the like have a large influence on transmission loss. On the other hand, if the thickness t of the dielectric body 3 is set as shown in the following equation, a leaky mode is excited, and the transmission energy is concentrated in the hollow portion of the transmission path.

1±t=-! -(n2-1)2m ・・・・・・ ・・・・・・
...(1) However, n is Ii' of the dielectric! The appeal rate m is a decimal number. That is, equation (1) is a conditional equation that minimizes the radiated energy of the dielectric 3 to the outside of the tube and the energy stored inside the tube.

The transmission loss at this time is expressed as the attenuation constant α by the following equation.

However, k is 2π/λ I] is Jo (u) = OT Mom T EomJ
n (u) = OHE (n+1) mEH (n-1
) m (J. is the following Bessel function) C is C=1. TEom mote C= n
' T Mom mote c -: (n4
Mo1) HEnm F: Hnm mode Also, if the loss amount is L, L = 10 loglOe 2a[dR/unit
l[:ngth] According to this method, a simple direct optical transmission line with low loss can be obtained.

For example, at λ-10.6μm, the thickness t is 77.43μm.
If the inner radius T is 400 μm, the transmission loss is 0.
．． 56 dB/m is possible. However, in this method, the strength of the transmission path is hardly considered. That is, since the quartz glass 1 alone is mechanically extremely weak, covering the surface with a plastic whose refractive index is equal to that of the quartz glass 1 becomes strong. Specifically, quartz glass tube 1
Coat the surface with silicone resin having the same refractive index. If the sum of the glass layer thickness and the recon resin layer thickness is set so as to satisfy the condition of equation (1), a direct external optical transmission line with low loss and high strength can be obtained. That is, the cross-sectional shape is as shown in FIG.

The far-infrared light transmission path of this practical example is constructed by coating at least one surface of a dielectric glass tube with /recon resin, and adjusting the thickness of the quartz glass tube and the /recon resin layer to a predetermined value. By adjusting the thickness of the film, it is possible to efficiently transmit far-infrared light.

In the above example, Coat 1 is made of a single layer of licon resin, but this can be made into multiple layers with the same refractive index (7) and the same thickness.For example, the outermost layer can be used as a colored layer for protection. It is also possible to reduce the intrusion of harmful light. Since the resin layer (1: 'or) has a discardability, it also has the advantage that it does not cause any problem even if it is deformed.

The far-infrared light transmission line of the present invention has the advantages of low loss, simple structure, and flexibility.

[Brief explanation of the drawing]

FIG. 1 is a diagram showing monthly filtering wavelength ranges used in optical fibers, and FIGS. 2 and 3 are cross-sectional views showing far-infrared light transmission lines according to embodiments of the present invention. 1...Plastic, 2...Quartz glass tube, 3.../Rico/Resin.

Claims (1)

[Claims] 1. A plastic layer having a refractive index equal to that of the dielectric is provided on at least one of the inner and outer surfaces of a tubular dielectric, and the thickness of this plastic layer is t2, and the thickness of the dielectric is t2. If the thickness is tl, the wavelength of far-infrared light is λ, and the refractive index of the dielectric and the plastic layer at this wavelength λ is n1, a constant is m, then 1↓ t1+t2-s(n2-1) A far-infrared optical transmission line characterized in that it is configured so that m holds true.