Jacob Lasri

Gain characteristics of a frequency nondegenerate phase-sensitive fiber-optic parametric amplifier with phase self-stabilized input.

We experimentally demonstrate, for the first time to our knowledge, a phase-sensitive amplifier based on frequency nondegenerate parametric amplification in optical fiber, where the input signal-idler pair is prepared all-optically. Using two fiber-optic parametric amplifier sections separated by a fiber-based wavelength-dependent phase shifter, we observe and investigate phase-sensitive gain profile in the 1550 nm region both experimentally and theoretically. The realized scheme automatically generates gain-defining phase that is environmentally stable, making it advantageous for building phase-sensitive transmission links.

Octave-spanning, high-power microstructure-fiber-based optical parametric oscillators

We investigate femtosecond optical parametric oscillators (OPOs) based on short pieces of microstructure fiber that generate sub-picosecond pulses with record average output power (50 mW) and >200 nm of wavelength tunability (yellow to near-IR). Signal and conjugate (idler)fields spanning an octave are also demonstrated. These systems can operate with a wide range of microstructure fibers, pump laser wavelengths and pulse durations, and our analysis shows that in terms of wavelength tunability and output power using short (less than a few cms) optical fibers leads to performance that is superior to that with longer lengths.

Ultralow timing jitter 40-Gb/s clock recovery using a self-starting optoelectronic oscillator

We demonstrate clock recovery with ultralow timing jitter by using a novel self-starting optoelectronic oscillator that is based on an electroabsorption modulator in a fiber extended cavity. The oscillator simultaneously generates a 10-GHz-rate microwave signal and a train of 15-ps optical pulses with /spl sim/40-fs timing jitter in the 100-Hz to 1-MHz range. Under direct optical-injection locking of the oscillator, we demonstrate simultaneous error-free extraction of both the electrical and the optical clocks of 10-GHz rate from either a single-channel 10-Gb/s return-to-zero data stream or a four-channel 40-Gb/s optical time-division-multiplexed data stream.

Self-starting optoelectronic oscillator for generating ultra-low-jitter high-rate (10GHz or higher) optical pulses

We demonstrate a novel, self-starting optoelectronic oscillator based on an electro-absorption modulator in a fiber-extended cavity for generating an optical pulse stream with high-rate and ultra-low jitter capabilities. Optical pulses at 10GHz repetition rate are demonstrated with >90dBc/Hz side-mode suppression and the lowest timing jitter (42fs in the 100Hz-1MHz range) reported to date for a self-starting source. Along with the optical pulse stream, the oscillator also generates a 10GHz electrical signal with ultra-low phase noise.

A microstructure-fiber-based 10-GHz synchronized tunable optical parametric oscillator in the 1550-nm regime

We demonstrate a microstructure-fiber (MF)-based supercontinuum source and a synchronously pumped optical parametric oscillator in the 1550-nm regime. By using a 12.5-m-long MF, we obtained a 10-GHz repetition-rate picosecond-pulse source that is capable of /spl sim/120-nm wavelength tunability due to the wide-gain bandwidth of the combined processes of stimulated Raman scattering and parametric four-wave mixing.

Noise-figure limit of fiber-optical parametric amplifiers and wavelength converters: experimental investigation

Recent theoretical work predicts that the quantum-limited noise figure of a x(3)-based fiber-optical parametric amplifier operating as a phase-insensitive in-line amplifier or as a wavelength converter exceeds the standard 3-dB limit at high gain. The degradation of the noise figure is caused by the excess noise added by the unavoidable Raman gain and loss occurring at the signal and the converted wavelengths. We present detailed experimental evidence in support of this theory through measurements of the gain and noise-figure spectra for phase-insensitive parametric amplification and wavelength conversion in a continuous-wave amplifier made from 4.4 km of dispersion-shifted fiber. The theory is also extended to include the effect of distributed linear loss on the noise figure of such a long-length parametric amplifier and wavelength converter.

SOA-based regenerative amplification of phase-noise-degraded DPSK signals: dynamic analysis and demonstration

A theoretical analysis and an experimental demonstration of semiconductor optical amplifier (SOA)-based regenerative amplification (SORA) of phase noise (PN)-degraded return-to-zero (RZ) differential phase-shift keying (DPSK) signals are presented. The Q-factor improvement is 1.6 dB in single-channel and about 0.8 dB in two non-demultiplexed-channel regimes. The key physical mechanism that enables regeneration by the SORA is the discriminative gain provided by the SOA for the logical 0s versus the logical 1s when two mutually antisymmetric ON-OFF keying (OOK) data trains, created by the DPSK signal, collide in the SOA. The modeling results agree with the experiment.

A self-starting hybrid optoelectronic oscillator generating ultra low jitter 10-GHz optical pulses and low phase noise electrical signals

We describe a self-starting optical pulse source generating ultra low noise 15-ps-wide pulses at 10 GHz. It is based on a hybrid optoelectronic oscillator comprising a fiber extended cavity mode-locked diode laser which injection locks a self-oscillating heterojunction bipolar phototransistor. Average jitter levels of 40-43 fs and an amplitude noise of 0.1-0.15% over a frequency range of 500 Hz-15 kHz or 500 Hz-1 MHz were obtained, respectively. The noise is slightly larger, a 57-fs jitter and 0.2% amplitude noise, for a frequency range of 100 Hz-1 MHz. A 10-GHz electrical signal with a low phase noise (-108 dBc/Hz at 10-kHz offset from the carrier) is also generated.

Optoelectronic mixing, modulation, and injection locking in millimeter-wave self-oscillating InP/InGaAs heterojunction bipolar photo transistors-single and dual transistor configurations

We describe an experimental investigation of two millimeter-wave oscillators one employing a single and the other using two InGaAs/InP heterojunction bipolar photo-transistors (photo-HBTs). The single HBT oscillator can be optically injection locked to improve its spectral purity. Alternatively, it can be modulated by analog or digital data carried by an optical signal. In the two phototransistors case, one HBT oscillates and is optically injection locked while the second serves as a modulator. The two-transistor case proved to be superior in terms of carrier spectral purity, analog modulation efficiency and linearity as well as for digital modulation. Its advantages stem from the better isolation between the local oscillator and modulating signals and from the ability to separate the injection-locking and modulation functions.

An integrated heterojunction bipolar transistor cascode opto-electronic mixer

An integrated electrically pumped opto-electronic mixer consisting of two InP-GaInAs heterojunction bipolar transistors in a cascode configuration is demonstrated. Intrinsic down-conversion gains of 18.2 and 8.9 dB at RF optical modulation frequencies of 3 and 9.5 GHz were obtained. The performance of the cascode mixer and a single heterojunction bipolar transistor (HBT) opto-electronic mixer are compared. The performance of the cascode mixer was superior to the single HBT mixer, mainly at high frequencies. Up and down mixing conversion gains were measured and found comparable. A simulation was carried out by solving the nonlinear differential equations that correspond to the large-signal equivalent circuit. The results of the simulation enabled us to identify the principal nonlinear components in the equivalent circuit.