US Patent 7277645 High-bit-rate long-haul fiber optic communication system techniques and arrangements

A 90 degree Alternate-Phase (AP) on-off keying (OOK) transmission format for high bit rate, long-haul optical transmission systems employing a chirped or a chirp-free pulse stream generated by a pulse generator (e.g., Mach Zehnder modulator) driven by mixing two electrical signals—one for intensity modulation and another for pulse modulation. These electrical signals may be two properly skewed sinusoidal electrical signals at half the desired data rate thereby generating a pulse stream in which the maximum optical phase modulation occurs at the intensity peak of each pulse and is 90 degrees out of phase with its nearest neighbors.