The helpful answer is, by deduction, the black side of the RX is the back (non-absorbant), with the lens/bump at the front. It follows that the front of the TX has the lens. By elimination and test, the data sheets shows the configuration with the lens facing outward: with the Cathode/Collector on the left and the Anode/Emitter on the right for both the TX and RX.
There's nothing wrong with the circuit, it's working now that the orientation and polarity of the components is correct. The Frontispiece/heading pictures are wrong and misleading.
I hope this not only answers the question but clarifies what seems to be a common query
Date published: 2017-04-28