A. Hatziefremidis

30 Gb/s all-optical clock recovery circuit

All-optical clock recovery is demonstrated from pseudo-data patterns at 30 Gb/s. The circuit is based on the optical gain modulation of a semiconductor optical amplifier fiber laser. The recovered clock is a 2.7-ps pulse train, with very low modulation pattern even in the presence of more than 200 consecutive 0s in the data signal.

Optical clock repetition-rate multiplier for high-speed digital optical logic circuits.

Repetition-rate multiplication has been shown by use of a fiber ring oscillator with a semiconductor optical amplifier as the gain medium and by use of fast saturation and recovery of the amplifier from an external optical pulse train. Repetition-frequency multiplication up to 6 times and up to 34.68-GHz frequency have been achieved.

20-GHz broadly tunable and stable mode-locked semiconductor amplifier fiber ring laser

We present an actively mode-locked fiber ring laser that uses a single active semiconductor optical amplifier device to provide both gain and gain modulation from an external optical pulse train. The laser source generated 4.3-ps pulses at 20 GHz over a 16-nm tuning range and is stable against environmental changes and simple to build.

Experimental and theoretical studies of a high repetition rate fiber laser, mode-locked by external optical modulation

An experimental and theoretical study of a high repetition rate laser source operating on a novel mode-locking technique is presented. This technique relies on the fast saturation and recovery of a semiconductor optical amplifier induced by an external optical pulse and has been used to obtain 4.3 ps pulses at 20 GHz. A complete mathematical model of the fiber ring laser is presented describing the mode-locking process in the laser oscillator and providing solutions for the steady-state mode-locked pulse profile. The critical parameters of the system are defined and analyzed and their impact on the formation of the mode-locked pulses is examined. The comparison between the theoretical results and the experimental data reveals very good agreement and has allowed the optimization of the performance of the system in terms of its critical parameters.

Optical power limiter using a saturated SOA-based interferometric switch

We demonstrate an optical power limiter using a semiconductor optical amplifier (SOA)-based interferometric gate powered by a strong continuous-wave input signal. We present a detailed theoretical and experimental investigation of the power limiting characteristics of saturated SOA-based switches, showing good agreement between theory and experiment.

Laser sources for polarized electron beams in cw and pulsed accelerators

We report the characterization of a high power, high repetition rate, mode-locked laser system to be used in continuous wave and pulsed electron accelerators for the generation of polarized electron beams. The system comprises of an external cavity diode laser and a harmonically mode-locked Ti:Sapphire oscillator and it can provide up to 3.4 W average power, with a corresponding pulse energy exceeding 1 nJ at 2856 MHz repetition rate. The system is tunable between 770}785 and 815}835 nm with two sets of diodes for the external cavity diode laser. ( 1999 Elsevier Science B.V. All rights reserved.

Missing pieces in the puzzle of ultra-high speed all-optical logic

We demonstrate Boolean XOR operation at 10 Gbps using an SOA assisted Sagnac interferometer and an optical clock multiplication circuit that may be used for local gate synchronization. The XOR operation of the SOA-assisted Sagnac was verified using two modulated optical control beams A and B that may take a logical O and 1. The logical output is imprinted on a third optical beam (CLK) which is held on input continuously to a logical 1 and is monitored at the transmission port T of the gate.

30 Gbps, broadly tunable, all-optical, clock recovery circuit

Optical clock recovery is demonstrated up to 30 Gbps, with very low modulation pattern even for long series of consecutive 0s. The circuit uses all-optical gain modulation of a SOA in a fiber ring laser.

Numerical Modeling of a High Repetition Rate Fiber Laser, Mode-Locked by External Optical Modulation of a Semiconductor Optical Amplifier

A theoretical study of a high repetition rate laser source based on a novel mode - locking technique is presented. This technique relies on the fast saturation and recovery of a semiconductor optical amplifier induced by an external optical pulse and has been used to obtain 4.3 ps pulses at 20 GHz. A numerical model of the fiber ring laser has been developed describing the mode - locking process in the laser oscillator and providing solutions for the steady - state mode - locked pulse profile. The critical parameters of the system are defined and analyzed and their impact on the formation of the mode - locked pulses is examined. The comparison between the theoretical results and the experimental data reveals very good agreement and has allowed the optimization of the performance of the system in terms of these parameters.

Optical clock repetition rate multiplier

Summary form only given. We report a short pulse, high repetition rate laser source that is capable of producing 15 ps pulse trains, at a repetition frequency of up to 34.68 GHz. The principle of its operation relies on a master-slave oscillator arrangement. In this instance the master oscillator is provided by a 5.78 GHz gain switched DFB, to which a fiber ring laser is synchronised. This arrangement of obtaining the high repetition rate optical clock signal presents two significant advantages. (a) The high repetition frequency optical clock requires a low frequency and therefore less expensive rf signal generator. (b) The low repetition frequency rf and optical signal may be used as the universal reference signal of all the high repetition frequency optical clocks in the optical logic circuit. In this way data may be introduced into the logic circuit at a low rate, so that it is compatible with commercially available modulators.