Patent ID: 8781336

Claim:
An optical communication system comprising: an optical transmitter configured to emit a frequency modulated signal having a bit rate frequency and a frequency excursion between 20% and 80% of the bit rate frequency; and an optical discriminator configured to convert the frequency modulated signal to a substantially amplitude modulated signal, wherein the optical discriminator includes: a delay line interferometer (DLI) including an input, an output, a first optical path coupling optical signals from the input to the output, and a second optical path coupling optical signals from the input to the output, the first and second optical paths having different lengths; and a filter positioned in the second optical path, wherein: a combined transmission function of the DLI and the filter is effective to cause at least one of a rise time or fall time of the substantially amplitude modulated signal to be less than a corresponding rise time or fall time of the frequency modulated signal; the combined transmission function has alternating high and low peaks; and the low peaks are between 1.5 and 4 dB lower than the high peaks.