I use to work on paper tape readers why back then. The newest I worked on in the 70s used IR light emitters and detectors looking through the 8 data channels and one sprocket channel. They were pretty simple as the data was all parallel. The timing was done by using the small middle sprocket holes as the data ready strobe to tell the receiving device that the other 8 output channels held valid data. As the sprocket hole is smaller in diameter then the other eight data holes that method worked well and made the data integrity independent to tape speed variations.
Lefty