Laser Diode / LED to Fiber Delivery System Questionnaire NOTE 1: Backreflection often causes the laser diode intensity to fluctuate as well as change the laser frequency. It can also cause the monitor current to give higher than normal readings, which will affect your output power if you are running the diode in constant power mode. We recommend pigtail style couplers for low backreflection. For the very best protection from backreflection, consider using an isolator in the ciupler system.
If you have to have receptacle style laser diode to fiber coupler and backreflection is a concern, then we recommend using receptacle style laser diode to fiber couplers with angled-flat polished FC (FC/AFC) connector fibers. Please note that we do not recommend standard angle point contact (APC) connectors. The problem with APC connectors is that the coupling efficiency into the fiber will change if you use the same coupler with a fiber with a different APC connector. This is because the position of the fiber with respect to the lens changes due to tolerances on the angle tip of the connector. For more information on this issue, please read our application note FC/APC Connectors Versus Flat Angled Finish FC Connectors, available on our website: (https://www.ozoptics.com/ALLNEW_PDF/APN0006.pdf)
Receptacle style couplers are generally recommended for systems which are not sensitive to backreflection and where different fibers are often used. They are also recommended for high power applications where fiber ends could be burnt, in which case connectors could easily be repolished or reterminated. To minimize backreflection, both ends of the fiber should be angle polished and/or AR (antireflection) coated.
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