定义：一种可以控制光纤中光的偏振态的器件。

很多光纤器件，例如干涉仪，需要能够实现对光纤中光的偏振态的控制。因此，发展了不同类型的光纤偏振控制器。 

弯曲光纤中的蝙蝠耳控制器 
一种常见的偏振控制器是通过弯曲（或缠绕）光纤得到双折射。总的延迟（双折射大小）与光纤的长度成正比，与弯曲半径成反比。还与光纤类型有关。有些情况下可以将光纤以特定弯曲半径缠绕几圈，这样可以得到λ / 2或 λ / 4 的延迟。 

图1：蝙蝠耳偏振控制器，包含三个可以沿着入射光纤轴旋转的光纤线圈。 
通常，使用三个线圈组成一列，中间线圈作为半波片，两边的分别为四分之一波片。每一个线圈都可以沿着入射和出射光纤轴旋转。通过调整三个线圈的指向，可以将入射的特定波长的偏振态转化成任意输出的偏振态。但是，对偏振的影响也与波长有关。在高峰值功率时（通常发生在超短脉冲中），会发生非线性偏振旋转。 
光纤线圈的直径不能太小，否则弯曲会引入附加的弯曲损耗。 
另一种更紧凑的类型，并且对非线性更加不敏感，是利用了光纤而不是光纤线圈的强双折射（偏振保持）。 

压缩光纤偏振控制器 
有一种装置可以得到可变化的波片，可以在变化的压力下对光纤长度进行一定程度的压缩。通过一点点绕光纤轴旋转压缩的光纤，并且在距离压缩部分一定距离的地方夹紧光纤，那么可以得到任意的输出偏振态。实际上，可以得到与Babinet-Soleil补偿器（一种体光学器件，包含两个双折射楔）相同的性能，尽管二者工作原理是不同的。 
也可以采用多个位置的压缩，其中只有压力而不是旋转角发生变化。压力变化通常是采用压电换能器来实现。这种装置也可以作为扰偏器，其中压电由不同频率或者随机信号驱动。

Definition: devices which allow one to control the state of polarization of light within fibers

More general term: polarization controllers

Various fiber-optic devices such as interferometers require an adjustable state of polarization of light in a fiber. For that purpose, different types of fiber polarization controllers have been developed.

Bat Ear Controllers with Bent Fibers

A popular type of fiber polarization controller exploits the birefringence which is induced by bending (coiling) a fiber. The total retardation (amount of birefringence) is proportional to the length of fiber and inversely proportional to its bending radius. It also depends on the fiber type. Some simple holders allow to arrange for some number of fiber turns with a given bending diameter, so that effectively a λ / 2 or λ / 4 retardation is achieved, for example.

Figure 1: A “bat ear” polarization controller, containing three fiber coils which can be rotated around the input fiber's axis.

Frequently, one uses three such fiber coils (“bat ears”) in a sequence, where the middle coil acts as a half waveplate and the outer ones as quarter waveplates. Each coil can be rotated around an axis in line with the input and output fibers. By adjusting the orientation of all three coils, one can transform a given input state polarization at a fixed wavelength into any output state of polarization. Note, however, that the effect on the polarization has some wavelength dependence. For high peak powers, as often occur with ultrashort pulses, there can also be nonlinear polarization rotations.

The diameters of the fiber coils should not be too small, as otherwise the bending would cause excessive bend losses.

A more compact variant, which is also less sensitive to nonlinear effects, uses strongly birefringent (polarization-maintaining) fibers instead of fiber coils.

Polarization Controllers with Squeezed Fibers

One can realize an effective variable waveplate with a device which allows one to squeeze some length of fiber with a variable amount of pressure. By rotating the squeezed bit of fiber around its axis while keeping the fiber clamped in some distance from the squeezed part, one can obtain an arbitrary output state of polarization. In effect, one achieves the same as with a Babinet–Soleil compensator (a bulk-optical device containing two birefringent wedges), although the operation principle is different.

It is also possible to use several squeezing sections in series, where only the pressure but no rotation angle is varied. This variant may also be equipped with piezo-electric transducers. That kind of device can also serve as a polarization scrambler, when the piezos are driven with different frequencies or random signals.