pi/2 alternate-phase ON-OFF keyed 40-Gb/s transmission on standard single-mode fiber

We demonstrate a transmission format based on pulse-overlapped ON-OFF keying (OOK) in which the optical phase of neighboring pulses alternates by pi/2 within a return-to-zero (RZ) data stream. We experimentally show a simple means to realize pi/2 alternate phase OOK and that an effective reduction in nonlinear transmission penalty from intrachannel four-wave mixing should. be achieved in systems where strong pulse overlap occurs. Simulations are presented that predict an expected improvement in power tolerance of similar to2 dB over the 33% duty cycle RZ format for a 40-Gb/s transmission in 15 x 80-km spans of standard single-mode fiber.