Industrial Fiber Optics offers a wide variety of fiber optic system components, including the IF-D95OC fiber optic receiver. You may spot this device with an additional ‘I’ suffix at the end however, as in IF D95OCI. What does this extra ‘I’ signify?
The ‘I’ in this part number indicates an inverted output as compared to the normal configuration. When the light to the receiver is ON, the output will be LOW, and vice versa. Please see Figure 5 from the supplier’s datasheet, here: