衣食住行，處處離不開纖維，光導纖維就是其中一類可以傳輸光信號的纖維。如今光纖也不僅僅用于通訊技術，利用纖維狀的特征以及材料選擇的靈活度，光纖在傳感、能量、醫(yī)療等等領域都嶄露頭角。

怎么定義特種光纖？根據(jù)“RP Photonics Encyclopedia”介紹，就是“具有特殊設計或材料的光纖”。

Definition: optical fibers with special designs or materials

定義：具有特殊設計或材料的光纖

More specific terms:fluoride fibers,phosphatefibers,active fibers,polarizationmaintaining fibers,tapered fibers,photonic crystal fibers

更具體的術語：氟化物纖維，磷酸鹽纖維，主動纖維，保偏纖維，錐形纖維，光子晶體纖維

Author（作者）:Dr. Rüdiger Paschotta

Specialty optical fibersare usually understood as optical fibers that have at least one special property, distinguishing them fromstandard fibers. However, there is no universally accepted definition of the termstandard fiber. One may regard a standard fiber as a simplestep-index fiber, made with standardmaterial(in case of glass fibers:silica) and with common values of parameters like thecoresize andnumerical aperture.

特種光纖通常被理解為具有至少一種特殊特性的光纖，將其與標準光纖區(qū)分開。但是，現(xiàn)在也并沒有標準纖維的普遍接受定義。我們一般可以將標準纖維視為簡單的階躍折射率纖維，它是由標準材料（在玻璃纖維的情況下為二氧化硅）制成，并具有諸如纖芯尺寸和數(shù)值孔徑之類的參數(shù)的通用值。

Specialty fibers can then belong to various groups:

特種纖維可以屬于下列分類：

Some fibers use non-standard materials. For example, there arefluoride fibersthat can transmit in longer(infrared) wavelength regions (mid- infrared fibers). Also, there arephosphate glassfibers, which can be morehighly doped with laser-active rare earth ions. Radiation-resistant fibers are made from materials that are less affected by radiation and used for example in space applications. Some fibers are made from monocrystalline material; they are calledsingle - crystal fibers. Single - crystal fibers are suitable for far higher power levels, particularly in the domain ofultrashort pulseamplification. But it istentatively more difficult to obtain a high outputbeam qualitydue to the inherent multimodenature. There are even liquid core fibers, offering widebandinfrared transmission. Special materials may also be used for fiber coatings and jackets.

有些纖維使用非標準材料。例如，有氟化物纖維、硫系玻璃纖維，重金屬氧化物纖維等可以在更長（紅外）波長范圍內傳輸（近、中紅外纖維）。

此外，還有磷酸鹽玻璃纖維，可以易于進行更高程度的活性稀土離子摻雜。耐輻射纖維由受輻射影響較小的材料制成，例如用于太空應用。一些纖維是由單晶材料制成的。它們被稱為單晶纖維。單晶纖維適用于高功率激光器，特別是在超短脈沖放大器應用領域有突出性能。但是由于固有的多模特質，難以獲得較好輸出光束質量。另外，還有液芯光纖，可提供寬帶紅外傳輸。更重要的是，特殊材料也可用于纖維的涂層。

Active fibers, being doped with laser-active ions(generally withrare-earth ions), are often generally regarded as specialty fibers.Double-clad fibers, having an additional larger waveguide structure for pump light, are even more special.

摻有激光活性離子（通常摻有稀土離子）的主動纖維通常被視為特種材料纖維。雙包層光纖具有更大波導結構用于泵浦光。

Some fibers exhibit extreme or specially tailored parameters, such as an unusually largefiber corediameter or a very highnumerical aperture. Also, there arelarge mode area fibers, exhibiting particularly large-fibermodes.Dispersion-shifted fibershave tailoredchromatic dispersionproperties. Indispersion - decreasing fibers, the chromatic dispersion even varies over the length.

有些光纖表現(xiàn)出極端的定制參數(shù)，例如異常大的纖芯直徑、方形纖芯、或很高的數(shù)值孔徑。大模面積的光纖表現(xiàn)出特別大的模式。色散位移光纖具有定制的色散特性。在色散緩變光纖中，色散甚至會隨著長度而變化。

There are fibers where thewaveguidefunction is not obtained simply with a somewhat increasedrefractive indexin the core (step-index fibers), but in some other way. For example, there arephotonic crystal fibers, containing air holes and therefore also being calledholey fibers.

有些光纖不能簡單地通過纖芯中的折射率略有增加而獲得波導功能（階躍折射率光纖），而是通過其他方式獲得。例如，包含空氣孔的光子晶體纖維，也稱為孔狀光纖或微結構光纖。

Polarization - maintaining fibersof different designs can be used to maintain a linear polarization state over arbitrarily long propagation distances.Single - polarization fibersguide only light with a certain polarization direction.

保偏光纖的結構類型靈活，可用于在任意長度傳播距離上保持線性偏振的狀態(tài)。單偏振光纖僅傳導具有特定偏振方向的光。

Tapered fibershave been stretched to obtain reduced fiber diameter, which usually changes along the length. They can be used, for example, for mode field adapters.

錐形纖維被拉伸以獲得較小的纖維直徑，該直徑通常沿長度變化。它們可以用于類似模式適配器等器件。

As there can be so different special properties, it is preferable to use a more specific term thanspecialty fibers, particularly in scientific publications.

這些特種工光纖由于具備種類繁多的特殊性能，因此在專門的應用領域一般會使用比“特種纖維”更具體的術語，尤其是在科學出版物中。

個人覺得 “RP Photonics Encyclopedia”中對特種光纖的定義還是非常準確的。最后一句話很重要，特種光纖在很多應用領域都起到了關鍵作用，領域之間的跨界很大，甚至沒有交集（比如石油、和醫(yī)療），所以涉及到某一個行業(yè)，還是利用該行業(yè)內公允的術語來命名某一種光纖更為方便。

審核編輯：劉清