David Dahan

Tunable all optical delay via slow and fast light propagation in a Raman assisted fiber optical parametric amplifier: a route to all optical buffering

We propose and demonstrate the use of narrow band optical parametric amplification for tunable slow and fast light propagation in optical fibers. The parametric gain is coupled to the Raman process which changes the gain value moderately but modifies the gain spectral shape. Consequently, the delay is enhanced at short wavelengths while it is moderated at long wavelengths. The maximum delay and tuning range can be optimized with respect to each other considering saturation effects in long fibers. The proposed scheme offers tunable delay in the presence of gain and with a bandwidth which is sufficiently wide to process digital data streams at tens of Gbit/s rates as well as picoseconds pulses.

Broad-band wavelength conversion based on cross-gain modulation and four-wave mixing in InAs-InP quantum-dash semiconductor optical amplifiers operating at 1550 nm

Wavelength conversion based on four-wave mixing (FWM) and cross-gain modulation (XGM) is experimentally demonstrated for the first time in a 1550-nm InAs-InP quantum-dash semiconductor optical amplifier. Continuous-wave FWM with a symmetric conversion efficiency dependence on detuning direction and FWM mediated short-pulse wavelength conversion are demonstrated. Using XGM, we have successfully implemented short-pulse wavelength conversion over 10 THz and error-free data conversion of a 2.5-Gb/s data sequence over 7.5 THz. The pulsed XGM experiments suggest that adjacent regions within an inhomogeneously broadened gain spectrum are partially coupled which increases the operational bandwidth, but at the expense of speed.

Large tunable delay with low distortion of 10 Gbit/s data in a slow light system based on narrow band fiber parametric amplification

We describe slow light propagation of a 10 Gbit/s data stream in a narrow band fiber parametric amplifier. A large tunable delay of 10 to 60 ps with very low signal distortion has been demonstrated in a 1 km long dispersion shifted fiber. The longitudinal variation of the fiber propagation parameters was extracted from measured amplified spontaneous emission and these parameters serve to accurately predict the delayed temporal pulse shape. Simulated results suggest that the system exhibits large delays with low distortions in a wide spectral range within the OPA gain spectrum.

On the balance between delay, bandwidth and signal distortion in slow light systems based on stimulated Brillouin scattering in optical fibers

We describe systematic measurements of the gain and delay spectra in a slow light system based on stimulated Brillouin scattering in optical fibers. The measurements yield the system complex transfer function with which delays and signal distortion can be calculated for any input signal. The theoretical predictions are confirmed experimentally for single pulses as well as 50 Mb/s data streams in a system which employs pump modulation to modify the gain and delay spectra of the SBS process.

Numerical comparison between distributed and discrete amplification in a point-to-point 40-Gb/s 40-WDM-Based transmission system with three different modulation formats

We describe a detailed numerical investigation on the relative merits of gain flattened distributed Raman amplification (DRA) and discrete gain flattened amplifiers. We simulate a system with forty 40-Gb/s channels spaced at 100 GHz and compare the performance of three different modulation formats nonreturn-to-zero (NRZ), return-to-zero (RZ) and carrier-suppressed RZ (CS-RZ). Three types of amplifiers, multifrequency backward- and forward-pumped DRAs, and an idealized discrete gain flattened amplifier are examined for various signal powers and transmission distances. For the backward-pumped DRA, we also describe calculated tolerance limits imposed by incomplete dispersion slope compensation and polarization mode dispersion (PMD) level.

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.

Clock recovery at multiple bit rates using direct optical injection locking of a self-oscillating InGaAs-InP heterojunction bipolar phototransistor

In this letter, we describe the use of direct optical injection locking of a self-oscillating InGaAs-InP heterojunction bipolar phototransistor to extract the clock of high-speed optical signals. We demonstrate a single MGM oscillator, which can be locked by 10- to 40-Gb/s return-to-zero signals with high efficiency and low noise.

Self-starting ultralow-jitter pulse source based on coupled optoelectronic oscillators with an intracavity fiber parametric amplifier

A self-starting optical pulse source based on mutually coupled optoelectronic oscillators is described. The system employs a phototransistor-based microwave oscillator that is coupled to a fiber cavity optoelectronic oscillator with an intracavity fiber parametric amplifier. It self-starts and exhibits 3 ps pulses at a rate of 10 GHz with extremely low jitter of 30, 29, and 40 fs (for integration bandwidths of 100 Hz-15 kHz, 500 Hz-1 MHz, and 100 Hz-1 MHz, respectively).

High bit rate clock recovery of NRZ data by all-optical processing in a semiconductor optical amplifier and direct optical injection locking of a self-oscillating phototransistor

In this letter, we describe a novel all-optical processing technique of nonreturn-to-zero signals in a semiconductor optical amplifier, which enables spectral enhancement at the bit rate frequency. The processed optical signal is used for direct optical injection locking of an oscillator based on a heterojunction bipolar phototransistor. Clock extraction at 10 Gb/s and potential operation at 40 Gb/s and beyond are demonstrated.

Noise-reduction capabilities of a Raman-mediated wavelength converter

We describe ultrawideband Raman-mediated wavelength conversion. The nonlinear conversion transfer function is calculated analytically and simulated numerically in the cw regime, and the predicted performance is confirmed experimentally. Data conversion from long- to short-wavelength bands with signal reshaping and significant noise reduction are demonstrated experimentally at 10 Gbits/s and modeled by numerical simulations. Q factors and extinction ratios that are both larger than 10 dB are possible over an effective conversion bandwidth of 35 nm.