What process must occur before digital modulation in an optical transmitter?

Before digital modulation in an optical transmitter, the data must be encoded. This is a crucial step because encoding prepares the raw data for modulation by transforming it into a format that is suitable for transmission. Encoding involves converting the information into a specific code that can be efficiently modulated onto an optical carrier signal. This process often includes error correction and data compression, which enhance the reliability and efficiency of signal transmission.

Once the data has been encoded, it is then ready to undergo modulation, where the encoded data is combined with the optical carrier signal to generate the final transmission signal. This ensures that the data can be accurately communicated through the optical medium and received correctly by the optical receiver at the other end.