G. Theophilopoulos

20 Gb/s all-optical XOR with UNI gate

All-optical Boolean XOR is demonstrated on a 20 Gb/s pseudodata pattern using a semiconductor optical amplifier-based ultrafast nonlinear interferometer (UNI) switch. Bit pattern switching with low-pattern dependence and low switching energies is achieved.

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.

Clock recovery circuit for optical packets

We demonstrate an all-optical clock recovery circuit for operation with short data packets of 10-Gb/s rate. The circuit uses a Fabry-Perot etalon and a nonlinear UNI gate and is capable of acquiring the clock signal within a few bits.

All-optical packet address and payload separation

An all-optical address and data separation scheme is presented for short 10-Gb/s packets. The technique uses a novel packet clock recovery circuit that consists of a Fabry-Perot filter and a ultrafast nonlinear interferometer (UNI) gate to generate a local packet clock. A second cascaded UNI gate is used to separate the header and the payload, performing a simple AND operation between the packet and its self-derived clock. The proposed technique requires a small number of bits as guard band and this number is independent of the line rate.

Multiwavelength and power equalized SOA laser sources

Multiwavelength and power-equalized operation is demonstrated in a semiconductor optical amplifier ring laser that uses a fiber Fabry-Perot filter. By using single-pass optical feedback, the power-equalized oscillating spectrum is broadened so that simultaneous oscillation of 52 lines spaced at 50 GHz is achieved. The lines had 500 MHz width were power-equalized to within 0.3 dB and the extinction was better than 32 dB.

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.

Ultrafast time-domain technology and its application in all-optical signal processing

In this paper, we review recent advances in ultrafast optical time-domain technology with emphasis on the use in optical packet switching. In this respect, several key building blocks, including high-rate laser sources applicable to any time-division-multiplexing (TDM) application, optical logic circuits for bitwise processing, and clock-recovery circuits for timing synchronization with both synchronous and asynchronous data traffic, are described in detail. The circuits take advantage of the ultrafast nonlinear transfer function of semiconductor-based devices to operate successfully at rates beyond 10 Gb/s. We also demonstrate two more complex circuits-a header extraction unit and an exchange-bypass switch-operating at 10 Gb/s. These two units are key blocks for any general-purpose packet routing/switching application. Finally, we discuss the system perspective of all these modules and propose their possible incorporation in a packet switch architecture to provide low-level but high-speed functionalities. The goal is to perform as many operations as possible in the optical domain to increase node throughput and to alleviate the network from unwanted and expensive optical-electrical-optical conversions.

Optically addressable 2 x 2 exchange/bypass packet switch

In this letter, we demonstrate an optically addressable 2 /spl times/ 2 exchange-bypass switch operating with 10-Gb/s data packets. Switching is achieved at the bit level using an ultrafast nonlinear interferometer gate with two input data signals and a single control signal. The bit error rate of the switch in a static configuration was estimated to be 10/sup -11/ using synchronous digital hierarchy 64 data frames.

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.

40 GHz all-optical XOR with UNI gate

40 GHz Boolean XOR is demonstrated using an ultrafast nonlinear interferometer (UNI) gate. The gate operates with low switching energy and signals from the same source. It may be used in networking applications without wavelength conversion.