Product Data 904PM


Low loss and backreflection
High isolation
Small ratio variation with temperature
Compact package
Standard polarization maintaining (PM) fibers
Low ratio taps with PM or SM output

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.

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.


Polarization Isolation

Range from -17 dB to -20 dB depending on wavelength

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

Operating Temperature:

0 to +50 degrees C

Excess Loss:

0.05 dB typical, 0.2 dB maximum

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.



1 m standard length (longer available), sleeved in 900 micron HYTREL or 3 mm cable


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


Ordering Information: Fixed Ratio PM Couplers

To order Fixed Ratio PM Couplers, please use part numbers in this format:
904PM - ( 1 ) - ( 2 ) - ( 3 )
(1) - Wavelength (488;633;780;830;1064;1300 or 1550 nm)
(2) - Splitting Ratio (50:50 to 99:1)
(3) - Connector Style (AF=FCAPC;FC=FCUPC;00=None)

For more information, contact:
Phone: (727) 547-8307
Fax: (727) 547-0687

E-mail: fiberoptics@metrotek.com

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