Based on the evanescent wave couplers 954P (fixed ratio) and 905P (variable ratio), polished fibers are coated with polarization sensitive layers before assembly. The result is a polarization selective coupler which allows up to 99% coupling of the p-polarized mode while restricting the coupling of the s-polarized mode to approximately 1%. It is the analog of the cube beam splitter.
Model 968P is a true 2x2 port device, and can be used as a polarization separator or a combiner for orthogonal polarizations. p coupling is wavelength dependent, but is nominally flat over 100nm band width. Reduction in p coupling ratio at the edge of the band is observed as reduction in s isolation. s coupling is minimal at all wavelengths such that the polarization isolation in the p output port is constant.
Intermediate p coupling ratios can be set for polarizing couplers, 954PZ. There is also a variable ratio unit 968PV which allows optimization of coupling with wavelength or variation of the TM mode coupling at a given wavelength.
These devices are made only in polarization maintaining fibers. P is the slow (coupled) axis and S the fast axis.
All wavelengths >850nm
0 to +50 degrees C
p mode typically 0.8 dB, s mode 0.3dB at wavelengths >1um
p mode typically 1 dB, s mode 0.4dB at wavelengths<1um
No sleeving over fiber (coupler unpackaged) dim. 0.59" x 0.1" x 0.1"
Pigtails sleeved in 900 micron HYTREL (coupler in aluminum tubing) dim. Length 1.125" x Dia. 0.19"
Pigtails sleeved with 3mm cable (coupler housed in 2.5" x 2.5" aluminum package)
968PV: 25 mm x 38 mm x 63 mm aluminum case, with micrometer projecting 28 mm
1 m standard length (longer available)
FC/SPC, FC/APC, LC/APC, SC/APC, SC/PC
Variable p Coupling 0 - 99%, s<1%
25 mm x 38 mm x 63 mm aluminum case, with micrometer projecting 28 mm
Otherwise identical to model 968P
By assembling the coupler with longitudinal asymmetry, one input can be made to show reduced loss at the expense of increased loss in the other input port. The favored input port can be optimized for low loss of about 0.5 dB in p.
These devices are also available as integral parts of custom designed splice-free arrays and interferometric assemblies.