HOLLOW METALLIC + DIELECTRIC WAVEGUIDES FOR LONG DISTANCE OPTICAL TRANSMISSION + LASERS
HOLLOW METALLIC + DIELECTRIC WAVEGUIDES FOR LONG DISTANCE OPTICAL TRANSMISSION + LASERS
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DOI：
10.1002/j.1538-7305.1964.tb04108.x
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发表时间：
1964-01-01
影响因子：
--
通讯作者：
SCHMELTZER, RA
中科院分区：
文献类型：
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作者：
MARCATILI, EAJ;SCHMELTZER, RA
对于由介电材料或金属制成的用作光波导的空心圆形波导，确定了简正模式的场配置和传播常数。还确定了由于轴曲率引起的衰减增加。发现每种模式的衰减与自由空间波长 λ 的平方成正比，与圆柱半径 a 的立方成反比。对于 v = 1.50、λ = 1μ、a = 1 mm 的玻璃制成的中空介质波导，预计最小损耗模式 EH11 的衰减为 1.85 db/km。对于导轴的曲率半径 R ~ 10 km，该损耗会加倍。因此，介电材料似乎不适合用于长距离光传输的空心圆形波导，因为即使导轴的轻微曲率也会引入高损耗。尽管如此，介电材料作为气体放大器和振荡器的引导介质被证明是非常有吸引力的，不仅因为衰减低，而且因为在适当压力下含有氦氖“masing”混合物的介电管的单位长度增益可以通过减小管直径而大大提高。在该应用中，需要小的引导半径，从而使得引导轴线的曲率不重要。当λ = 0.6328μ和最佳半径a = 0.058 mm时，预测最大理论增益为7.6 db/m。结果表明，空心金属圆形波导对波导轴曲率的敏感度要低得多。这是由于金属在光频率下表现出相对较大的复介电常数。对于波长 λ = 1μ 和半径 a = 0.25 mm，铝波导中最小损耗 TE01mode 的衰减仅为 1.8 db/km。对于短至 R ∼ 48 米的曲率半径，这种损耗会加倍。当 λ = 3μ 且 a = 0.6 mm 时，TE01 模式的衰减也为 1.8 db/km。使该损耗加倍的曲率半径约为 75 米。 EH11模式在λ = 1μ和a = 0.25 mm时的直波导损耗为57 db/km，在λ = 3μ和a = 0.6 mm时增加到320 db/km。鉴于TE01模式在金属波导中的低损耗特性、非圆形电模式的高损耗辨别能力以及对轴曲率的相对不敏感性，空心波导损耗 金属圆形波导作为长距离光通信的传输介质似乎非常有吸引力。
The field configurations and propagation constants of the normal modes are determined for a hollow circular waveguide made of dielectric material or metal for application as an optical waveguide. The increase of attenuation due to curvature of the axis is also determined.The attenuation of each mode is found to be proportional to the square of the free‐space wavelength λ and inversely proportional to the cube of the cylinder radius a. For a hollow dielectric waveguide made of glass with v = 1.50, λ = 1μ, and a = 1 mm, an attenuation of 1.85 db/km is predicted for the minimum‐loss mode, EH11. This loss is doubled for a radius of curvature of the guide axis R ∼ 10 km, Hence, dielectric materials do not seem suitable for use in hollow circular waveguides for long distance optical transmission because of the high loss introduced by even mild curvature of the guide axis. Nevertheless, dielectric materials are shown to be very attractive as guiding media for gaseous amplifiers and oscillators, not only because of the low attenuation but also because the gain per unit length of a dielectric tube containing He‐Ne “masing” mixture at the right pressure can be considerably enhanced by reducing the tube diameter. In this application, a small guide radius is desirable, thereby making the curvature of the guide axis not critical. For λ = 0.6328μ and optimum radius a = 0.058 mm, a maximum theoretical gain of 7.6 db/m is predicted.It is shown that the hollow metallic circular waveguide is far less sensitive to curvature of the guide axis. This is due to the comparatively large complex dielectric constant exhibited by metals at optical frequencies. For a wavelength λ = 1μ and a radius a = 0.25 mm, the attenuation for the minimum loss TE01mode in an aluminum waveguide is only 1.8 db/km. This loss is doubled for a radius of curvature as short as R ∼ 48 meters. For λ = 3μ and a = 0.6 mm, the attenuation of the TE01mode is also 1.8 db/km. The radius of curvature which doubles this loss is approximately 75 meters. The straight guide loss for the EH11mode for λ = 1μ and a = 0.25 mm is 57 db/km and is increased to 320 db/km for λ = 3μ and a = 0.6 mm.In view of the low‐loss characteristic of the TE01mode in metallic waveguides, the high‐loss discrimination of noncircular electric modes, and the relative insensitivity to axis curvature, the hollow metallic circular waveguide appears to be very attractive as a transmission medium for long distance optical communication.