Standard lead color coding for a 1X2 or 2X2 couplers/Splitters
The orange lead designates the primary input, blue designates the primary output. Secondary input and output fibers are natural. For a non 50/50 coupling ratio, the larger percentage coupling ratio will always be on the blue lead. For example, in a 10/90 coupler. 10% will be on the natural lead and 90% will be on the blue lead.