Polarization Extinction Ratio (PER)
In most applications for PM fiber, only one of the two polarization orientations (states) is used - this is sometimes called the ‘wanted’ polarization-state. The extinction ratio simply compares the optical power held on the wanted axis to that which is on the unwanted axis, the orthogonal polarization state, expressed in decibels (dB).
![Polarization Extinction Ratio (PER)](/sites/default/files/styles/viewport/public/2020-07/6364.jpg.webp?itok=adEGTUpk)
So you can see, an Extinction-Ratio of -30dB is 1000:1 and -20dB is 100:1
The value of extinction ratio is dependant upon the length of fiber and the environmental conditions. If you subject the fiber to high mechanical stress and small-diameter bends, then it is possible to disrupt the internal stress (which generates the birefringence) and this reduces the extinction-ratio significantly.
Typical PER under various deployment conditions are indicated below.
Length | Conditions | Extinction Ratio |
1000m | Loose-tube cabled, wound on a 300mm cable reel | -25 to -30dB |
500m | Wound at low tension on a 150mm spool | -30 to -35dB |
100m | Wound at low tension (<5g) on a 60mm spool | -25 to -30dB |
10m | Laid straight | -35dB* |
*limit of measurement resolution; ask about our test set-up
For more information, please request our technical note 'PER and Crosstalk'.
Related Products: PM Coupler Fiber, PM Erbium Doped Fiber, PM Gyro Fiber, Polyimide Coated PM Fiber, Standard PM Fiber, Telecoms PM Fiber, Zing™ Polarizing Fiber
Related Terms: Birefringence, Birefringent Fiber, Bow-Tie Fiber, H-Parameter, Highly Birefringent (HiBi), Macro-Bending loss, Micro-Bending Loss, Polarization Extinction Ratio (PER), Polarization Maintaining (PM) Fiber, Polarization Mode