Optical homodyne PSK demonstration of 1.5 photons per bit at 156 Mbps with rate-(1/2) turbo coding.

We report the first demonstration of a near quantum-limited optical homodyne PSK receiver combined with powerful forward-error-correction coding, achieving 1.5 photons/bit sensitivity, within 4.5 dB of the Shannon limit. Phase-locking was achieved at 1.55 microm using an analog dither-based optical phase-locked loop with an external phase modulator. Analysis for this configuration with arbitrary loop damping is given showing a performance advantage for the overdamped case.

High-sensitivity multi-channel single-interferometer DPSK receiver.

A high-sensitivity method of demodulating wavelength-division-multiplexed optical DPSK channels using a single interferometer is described and demonstrated. We show that this technique can operate within existing standards and achieve near-quantum-limited receiver performance. The resulting hardware simplification has potential to reduce the cost of deploying and scaling future wide-band optical-communication networks employing WDM-DPSK.

Characterization of dynamic optical nonlinearities by continuous time-resolved Z-scan.

Dynamic optical nonlinearities are investigated with a dual-beam (pulsed-pump, cw probe) Z-scan technique. Monitoring of probe transmission after strong pump excitation permits determination of time-varying parameters such as nonlinear refraction n(I, t) and absorption alpha(I, t). Continuous time resolution provides an efficient means of measuring and distinguishing fast and slow nonlinear mechanisms such as electronic, free-carrier, and thermal effects observed in semiconductors. We demonstrate this technique in CdTe and measure bound-electronic refraction; two-photon absorption; free-carrier refraction, absorption, and diffusion; thermal refraction and temperature changes; and related time constants.