定义：
采用特殊设计或者材料的光纤。

特种光纤通常认为至少存在一个特殊性质，使其能够与普通的标准光纤分别开来。然而并没有一个通用的对于标准光纤的定义。可以简单的认为标准光纤就是阶跃折射率光纤，由标准材料（普通玻璃光纤的话，为石英）制造的，具有普通的参数值（纤芯尺寸和数值孔径）。因此特种光纤包含下面几个种类： 

• 有些光纤采用了非标准的材料。例如，有氟化物光纤，可以透射更长波长范围的光。还有磷酸盐玻璃光纤，可以掺杂很高浓度的激光活性稀土离子。抗辐射光纤是由不受辐射影响的材料制造的，可以应用于太空领域。有一些特殊材料也可以用作光纤涂层和光纤保护套。 
• 掺杂激光活性离子（通常是稀土离子）的活性光纤也被称为特种光纤。双包层光纤具有附加的传导泵浦光的波导结构，因此也是非常特殊的。 
• 有些光纤具有很特殊的参数，例如很大的光纤纤芯直径，或者非常大的数值孔径。另外，还有大模式面积光纤，具有非常大面积的光纤模式。色散位移光纤具有改进的色散特性。色散缓变光纤中，色散随着长度而变化。 
• 有些光纤中，波导功能不能简单的通过提高纤芯的折射率（参阅阶跃折射率光纤）来实现，而是需要通过其它的方法。例如，还有光纤晶体光纤，包含空气孔，因此也称为多孔光纤。 
• 采用不同设计的保偏光纤可以使光在任意长的传输距离内保持线偏振状态。单偏振光纤只能传播某一特定偏振方向的光。 
• 锥形光纤是将光纤拉伸得到的，其光纤直径变小，并且直径随着长度而变化。它可以用于模场适配器中。 

由于这些不同的特殊性质，因此很多时候并不将这些光纤都称为特种光纤，而是更倾向于采用更加具体的表达，尤其是在科学出版物中。

Definition: optical fibers with special designs or materials

More general term: optical fibers

More specific terms: fluoride fibers, phosphate fibers, active fibers, polarization-maintaining fibers, tapered fibers, photonic crystal fibers

Specialty optical fibers are usually understood as optical fibers which have at least one special property, distinguishing them from standard fibers. However, there is no universally accepted definition of the term standard fiber. One may regard a standard fiber as a simple step-index fiber, made with a standard material (in case of glass fibers: silica) and with common values of parameters like the core size and numerical aperture. Specialty fibers can then belong to various groups:

• Some fibers use non-standard materials. For example, there are fluoride fibers which can transmit in longer (infrared) wavelength regions (→ mid-infrared fibers). Also, there are phosphate glass fibers, which can be more highly doped with laser-active rare earth ions. Some fibers are made from monocrystalline material; they are called single-crystal fibers. There are even liquid core fibers, offering wideband infrared transmission. Special materials may also be used for fiber coatings and jackets.
• Polyimide fibers are optical fibers which are coated with polyimide (but usually have a glass core and cladding). Such fibers can withstand much higher temperatures (roughly 300 °C) than fibers with the more common acrylate coatings.
• Solarization-resistant fibers are made from specially processed fused silica which is relatively resistant to ultraviolet light, avoiding excessive solarization.
• Radiation-resistant fibers are made from materials which are less affected by radiation, possibly also treated e.g. with hydrogen loading and pre-irradiation, and used for example in space applications and in nuclear facilities.
• Active fibers, being doped with laser-active ions (generally with rare earth ions), are often generally regarded as specialty fibers. Double-clad fibers, having an additional larger waveguide structure for pump light, and triple-clad fibers with one more cladding, are even more special.
• Some fibers exhibit extreme or specially tailored parameters, such as an unusually large fiber core diameter or a very high numerical aperture. Also, there are large mode area fibers, exhibiting particularly large fiber modes and correspondingly weak nonlinear effects. The opposite holds for highly nonlinear fibers. Dispersion-shifted fibers have tailored chromatic dispersion properties. In dispersion-decreasing fibers, the chromatic dispersion even varies over the length.
• There are spun fibers, where the fiber preform is rotated during the fiber drawing process. They can be used as telecom fibers with much reduced polarization mode dispersion, and also for polarimetric sensors where random birefringence is disturbing.
• Chirally-coupled-core fibers have a core which is surrounded by one or more satellite cores which are chirally wound around it. The satellite cores serve by damping higher-order modes of the central core.
• There are fibers where the waveguide function is not obtained simply with a somewhat increased refractive index in the core (→ step-index fibers), but in some other way. For example, there are photonic crystal fibers, containing air holes and therefore also being called holey fibers.
• Polarization-maintaining fibers of different designs can be used to maintain a linear polarization state over arbitrarily long propagation distances. Single-polarization fibers guide only light with a certain polarization direction.
• Spun fibers are drawn from a fiber preform which is rotated around its axis during the drawing process. They have special polarization-maintaining properties.
• Tapered fibers have been stretched to obtain a reduced fiber diameter, which usually changes along the length. They can be used, for example, for mode field adapters.

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