A device capable of demultiplexing Tb/s pulse trains that requires less than 1 pJ of switching energy and can be integrated on a chip is presented. The device consists of an optical nonlinear element asymmetrically placed in a short fiber loop. Its switching time is determined by the off-center position of the nonlinear element within the loop, and therefore it can use the strong, slow optical nonlinearities found in semiconductors, which all other fast demultiplexers seek to avoid. The switch's operation at 50 Gb/s is demonstrated, using 600-fJ control pulses. >

A terahertz optical asymmetric demultiplexer (TOAD)

A novel, simple, compact, and integrable scheme of reconfigurable and ultrafast photonic logic gate is demonstrated, based on a single semiconductor optical amplifier (SOA) and able to process ultrafast signals. XNOR function has been optically implemented exploiting four-wave mixing and cross-gain modulation in an SOA. The same scheme can be easily reconfigured to obtain AND, NOR, and NOT logic gates. Performances in terms of bit error rate for 20-ps return-to-zero signals at 10 Gb/s show a power penalty limited to 0.5 dB for all logic gates but the AND, which experiences regeneration (-2-dB power penalty) due to nonlinear SOA noise compression.

Ultrafast integrable and reconfigurable XNOR, AND, NOR, and NOT photonic logic gate

All-optical ultra-fast and reconfigurable logic gates have been implemented exploiting simple and low-cost schemes based on nonlinear optical loop mirrors. Regenerative properties of the realised optical logic gates have been demonstrated.

Regenerative and reconfigurable all-optical logic gates for ultra-fast applications

Most research efforts to date on optical networks have concentrated on wavelength-division multiplexing (WDM) techniques where the information from different channels is routed via separate optical wavelengths. The data corresponding to a particular channel is selected at the destination node by a frequency filter. Optical time-division multiplexing (OTDM) has been considered as an alternative to WDM for future networks operating in excess of 10 Gb/s. Systems based on TDM techniques rely upon a synchronized clock frequency and timing to separate the multiplexed channels. Advances in device technologies have opened new opportunities for implementing OTDM in very high-speed long-haul transmission as well as networking. The multiterahertz bandwidth made available with the advent of optical fibers has spurred investigation and development of transparent all-optical networks that may overcome the bandwidth bottlenecks caused by electro-optic conversion. This paper presents an overview of current OTDM networks and their supporting technologies. A novel network architecture is introduced, aimed at offering both ultra-high speed (up to 100 Gb/s) and maximum parallelism for future terabit data communications. Our network architecture is based on several key state-of-the-art optical technologies that we have demonstrated.

Transparent optical networks with time-division multiplexing

A novel optical switch based on cascading two terahertz optical asymmetric demultiplexers (TOAD) is presented. By utilizing the sharp edge of the asymmetric TOAD switching window profile, two TOAD switching windows are overlapped to produce a narrower aggregate switching window, not limited by the pulse propagation time in the SOA of the TOAD. Simulations of the cascaded TOAD switching window show relatively constant window amplitude for different window sizes. Experimental results on cascading two TOADs, each with a switching window of 8ps, but with the SOA on opposite sides of the fiber loop, show a minimum switching window of 2.7ps.

A novel fast optical switch based on two cascaded Terahertz Optical Asymmetric Demultiplexers (TOAD).

An ultrafast, all-optical, soliton-trapping AND gate that consists of a birefringent optical fiber followed by a frequency filter is demonstrated. The gate is sensitive to the timing of the input pulses and provides an output with a large energy contrast. The performance of the gate is characterized by varying the total input energy, the ratio between the energies of the two input pulses, and the arrival-time difference between the input pulses. It is shown that the gate efficiency (characterized by its ON-OFF contrast ratio) increases with increasing pulse energy up to the limit where Raman effects become dominant in the fiber, and the optimal performance of the gate is obtained with two input solitons having equal energies. The gate efficiency degrades with increasing difference of arrival time of the two input pulses, but a contrast ratio of 5:1 can still be obtained for a full pulse width of timing mismatch. The experimental results are in agreement with numerical simulations using the coupled nonlinear Schrodinger equations. >

B. Hong

Papers

Ultrafast soliton-trapping AND gate