This application note demonstrates transmission of an FSK-modulated RF sub-carrier over standard singlemode fiber.
Subcarrier multiplexing helps carry multiple RF data streams over a single optical carrier, thereby saving on the number of lasers. The RF data can be amplitude modulated (ASK), or frequency modulated (FSK) or phase modulated (PSK). The modulated RF is then used to modulate optical carrier. The detected electrical signal at the receiver is demodulated using the appropriate demodulation technique depending on the type of modulation used at the transmitter. This application note uses frequency modulation of the RF signal.
Figure 1 shows the schematic layout using direct and external modulation of the laser.