POLARIZATION MAINTAINING VARIABLE
RATIO
EVANESCENT WAVE COUPLERS
Product Data 905
 | Precise Ratio Adjustment |
| Low loss |
| Low back reflection |
| Low polarization cross talk |
| Large operating bandwidth |
| Polarization Maintaining (PM) or non-PM types |
Variable ratio couplers are made with optically contacted polished fibers mounted in substrate blocks that have transverse motion in the contact plane to adjust core-to-core separation distance. In the case of PM fiber, the orientation of the fast and slow axes is preserved during the motion. A negligibly thick oil layer is used to lubricate the substrate blocks and ensure smooth motion. Long term ratio stability is better than 1% under laboratory conditions.
Fine transverse motion is accomplished by means of a micrometer and lever system. The 25:1 lever ratio gives approximately one micron of motion at the coupler center per 0.001 inch division on the micrometer.
Available fibers have cutoff wavelengths ranging from 450 nm to 1550 nm. For a particular fiber used in a variable coupler the useful bandwidth extends from the single mode cutoff wavelength to approximately 1.3 times the cutoff wavelength, where losses begin to occur.
Note: Photo shows connection (top right) for prototype of a remote control, pizeo motor control unit (Call for details).905 Specifications
| Polarization Isolation | -24 dB typical, -22 dB guaranteed |
| Coupling Ratio | 0-99% or 0-80% (at room temperature) |
| Excess Loss | 0.1dB typical ; 0.2dB maximum |
| Coupler Bandwidth | Specs |
| Package | 25 mm x 38 mm x 63 mm aluminum case, with micrometer projecting 28 mm (details) |
| Terminations | FCPC, FCAPC, SCPC, SCAPC |
| Pigtails | 1 meter (other lengths available) 250u bare fiber without connectors (Standard) or 1 meter (other lengths available) 900u HYTREL jacket (No Charge) or 1 meter (other lengths available) 3mm jacket (Special Order) |
