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

We demonstrate a transmission format based on pulse-over lapped 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 ~2 dB over the 33% duty cycle RZ formal for a 40-Gb/s transmission in 15 * 80-km spans of standard single-mode fiber.