EOMs Operating Manual
Ref. Ed. 0
–
08/02/2021
25
Fig. 40
Fig. 39
Notes:
Optical connectors are usually the first root cause of PER degradation because of the misalignment
between the PM fiber axes and the connector key.
In a same way, a bad mechanical tolerance with the mating sleeves can be a cause of PER
instabilities and degradation. Some manufacturers propose mating sleeves with a better
mechanical tolerance, for high PER applications.
3.6
Polarization Dependent Loss (PDL)
The PDL is the optical loss difference (dB) between the two main polarization axes when light is
injected into the modulator. This parameter is particularly relevant to the polarization switch and
the polarization scrambler modulator.
On LiNbO
3
chips, PDL is the optical loss difference between TE & TM polarization states (dB) for the
respective optical input powers P1 & P2 (in dBm):
If P
1
=P
2
,
𝑃𝐷𝐿(𝑑𝐵) = 𝛼
𝑇𝐸
(𝑑𝐵) − 𝛼
𝑇𝑀
(𝑑𝐵)
𝛼
𝑇𝐸
(𝑑𝐵) = 10. 𝑙𝑜𝑔
10
(
𝑃
𝑇𝐸
𝑃
1
)
𝛼
𝑇𝑀
(𝑑𝐵) = 10. 𝑙𝑜𝑔
10
(
𝑃
𝑇𝑀
𝑃
2
)
𝑃𝐷𝐿(𝑑𝐵) = 10. 𝑙𝑜𝑔
10
(
𝑃
𝑇𝐸
𝑃
𝑇𝑀
)
𝑃𝐷𝐿(𝑑𝐵) = 𝑃
𝑇𝐸
(𝑑𝐵𝑚) − 𝑃
𝑇𝑀
(𝑑𝐵𝑚)
