T. Houbavlis

All-optical signal Processing and applications within the esprit project DO/spl I.bar/ALL

This paper reviews the work performed under the European ESPRIT project DO/spl I.bar/ALL (Digital OpticAL Logic modules) spanning from advanced devices (semiconductor optical amplifiers) to all-optical modules (laser sources and gates) and from optical signal processing subsystems (packet clock recovery, optical write/store memory, and linear feedback shift register) to their integration in the application level for the demonstration of nontrivial logic functionality (all-optical bit-error-rate tester and a 2/spl times/2 exchange-bypass switch). The successful accomplishment of the projects goals has opened the road for the implementation of more complex ultra-high-speed all-optical signal processing circuits that are key elements for the realization of all-optical packet switching networks.

10 x 30 GHz pulse train generation from semiconductor amplifier fiber ring laser

A multiwavelength, fiber ring laser source, is demonstrated. It generates 10 wavelength channels, simultaneously mode-locked and synchronized at 30 GHz, each producing 7-ps pulses. The mode-locking technique relies on the gain saturation of the semiconductor amplifier from an external optical pulse train to impose the simultaneous mode-locking of the 10 wavelengths.

10-Gb/s all-optical half-adder with interferometric SOA gates

In this letter, we report an all-optical module that generates simultaneously four Boolean operations at 10 Gb/s. The circuit employs two cascaded ultrafast nonlinear interferometers and requires only two signals as inputs. The first gate is configured as a 2 /spl times/ 2 exchange-bypass switch and provides OR and AND logical operations. The second gate generates XOR (SUM bit) and AND (CARRY bit) Boolean operations and constitutes a binary half-adder. Successful operation of the system is demonstrated with 10-Gb/s return-to-zero pseudorandom data patterns.

Ultrafast pattern-operated all-optical Boolean XOR with semiconductor optical amplifer-assisted Sagnac switch

All-optical Boolean XOR operation is demonstrated on pseudo-data patterns at 20 Gb/s with a three optical input semiconductor optical amplifier-assisted Sagnac switch. Bit pattern switching has been achieved with low energies of the incoming clock and data pulses and low pattern dependence on the switched-out pulses.

All-optical XOR in a semiconductor optical amplifier-assisted fiber Sagnac gate

All-optical Boolean XOR is demonstrated on a high-speed serial bit stream with a three-optical input fiber Sagnac interferometer switch, which uses a semiconductor optical amplifier. Full duty cycle bit switching has been demonstrated up to 5 GHz with contrast ratio as high as 14.6 dB.

Clock and data recovery circuit for 10-Gb/s asynchronous optical packets

We demonstrate an all-optical clock and data recovery circuit for short asynchronous data packets at 10-Gb/s line rate. The technique employs a Fabry-Perot filter and a SOA-based ultrafast nonlinear interferometer (UNI) to generate the local packet clock, followed by a second UNI gate to act as decision element, performing a logical AND operation between the extracted clocks and the incoming data packets. The circuit can handle short packets arriving at time intervals as short as 1.5 ns and arbitrary phase alignment.

Numerical simulation of semiconductor optical amplifier assisted sagnac gate and investigation of its switching characteristics

The switching characteristics of a semiconductor optical amplifier (SOA)-assisted Sagnac gate are analyzed in terms of their critical performance parameters for full duty cycle operation from 10 to 40 GHz. Within this frame, the influence of the control pulse width, as well as of the SOA gain recovery time on the switching energy and the contrast ratio, is examined through numerical simulation. The obtained results show that full switching operation at 40 GHz or higher is feasible either by deploying gain recovery reduction techniques in bulk SOAs, or other alternative technologically advanced optical devices, such as quantum-dot SOAs.

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.

Pulse repetition frequency multiplication with spectral selection in Fabry-Perot filters

We present methods for obtaining high-repetition-rate full duty-cycle RZ optical pulse trains from lower rate laser sources. These methods exploit the memory properties of the Fabry-Perot filter for rate multiplication, while amplitude equalization in the output pulse train is achieved with a semiconductor optical amplifier or with a second transit through the Fabry-Perot filter. We apply these concepts to experimentally demonstrate rate quadruplication from 10 to 40 GHz and discuss the possibility of taking advantage of the proposed methods to achieve repetition rates up to 160 GHz.

Design algorithm of all-optical linear feedback shift registers

Abstract We demonstrate an algorithm for the design and implementation of an all-optical linear feedback shift register (LFSR), based on optically controlled XOR gate and optical shift registers. The algorithm tackles the huge length of optical shift registers to produce controllable pseudorandom binary sequences (PRBS).