Fiber with strong built-in birefringence, created by stress rods beside the core in PANDA or bow-tie designs or by an elliptical core. Light launched linearly polarized along the slow or fast axis stays there despite bends and temperature changes, with extinction ratios above 20 dB. PM fiber is needed for nonlinear frequency conversion, interferometers and modulators, and its axes must be aligned at every splice and connector.
PER dropped to 14 dB after the new splice, the PM fiber axes are off a few degrees, redo it with the rotation alignment.
Also heard as
- polarization-maintaining fiber
- PMF
Related terms
Waveplate
A birefringent plate that shifts the phase between two polarization components to rotate or convert polarization.
Fiber Bragg grating
A periodic index pattern written into a fiber core that reflects a narrow band of wavelengths and passes the rest.
SHG
Second Harmonic Generation: converting light to exactly double its frequency, half its wavelength, in a nonlinear crystal.
Optical isolator
A one-way valve for light that passes a beam forward and blocks reflections from returning to the laser.