954P POLARIZATION MAINTAINING FIXED-RATIO EVANESCENT WAVE COUPLERS and TAPS

954P Mini-Coupler Spec. sheet (see Reliability tests)

POLARIZATION MAINTAINING COUPLERS

General Product Data:

Fibers are side polished in glass substrate blocks to remove cladding material on one side of the core without distorting the core region. In the case of PM fibers, one stress member remains. Two polished fibers are placed into optical contact with their polarization axes aligned, and coupling from core to core occurs by the evanescent wave interaction. Precise loading of the substrate blocks ensures the fibers remain in low stress contact over a broad range of temperatures.

Polarization isolation of -30 dB is attainable using this technique.

Cross-section of 904p showing stress members.

Evanescent wave couplers offer inherent performance advantages because there is no deformation or tapering of the waveguiding cores. These devices have low loss and backreflection. Also, short interaction lengths (1-2 mm) allow small device packages to be realized.

The interface essentially vanishes with optical contact between identical silica surfaces. There is no intermediate material which can change its refractive index or thickness with age or environmental effects. The coupler behaves optically as if the fibers were fused and is very stable with temperature variations.

Specifications

Coupler Bandwidth

Polarization Isolation

Standard and High Isolation types:
Available range from -30 dB to -20 dB

Ratio Tolerance at 50/50 (set at room temperature on slow axis)

+/- 3% standard 53/47 to 47/53
+/- 2% 52/48 to 48/52
+/- 1% 51/49 to 49/51

>Available wavelengths:

0.488 to 2.04um

Operating Temperature:

-15 to +55 degrees C

Excess Loss:

<0.1 dB

Return Loss (Backreflection):

-70 dB typical

Power Handling:
These very low loss couplers allow CW power approaching that of the fiber itself.
The only restrictions we have noted is very high peak power, picosecond and femtosecond pulses that cause non-linear changes in the fiber that increases loss due to reduced guidance.

Package:

No sleeving over fiber (coupler unpackaged) dim. 0.59" x 0.1" x 0.1"
Pigtails sleeved in 900 micron HYTREL (coupler in shrink tubing) dim. 0.8" x 0.14" x 0.14"
Pigtails sleeved with 3mm cable (coupler housed in 2" x 2" aluminum package)

Pigtails:

1 m standard length (longer available)

Terminations:

FC/SPC, FC/APC or 5 mm diameter glass capillary tube with ends polished at an 8 degree angle with low stress