Scott A. Hamilton

781 Mbit/s photon-counting optical communications using a superconducting nanowire detector

We demonstrate 1550 nm photon-counting optical communications with a NbN-nanowire superconducting single-photon detector. Source data are encoded with a rate-1/2 forward-error correcting code and transmitted by use of 32-ary pulse-position modulation at 5 and 10 GHz slot rates. Error-free performance is obtained with -0.5 detected photon per source bit at a source data rate of 781 Mbits/s. To the best of our knowledge, this is the highest reported data rate for a photon-counting receiver.

100 Gb/s optical time-division multiplexed networks

We present ultrafast slotted optical time-division multiplexed networks as a viable means of implementing a highly capable next-generation all-optical packet-switched network. Such a network is capable of providing simple network management, the ability to support variable quality-of-service, self-routing of packets, scalability in the number of users, and the use of digital regeneration, buffering, and encryption. We review all-optical switch and Boolean logic gate implementations using an ultrafast nonlinear interferometers (UNIs) that are capable of stable, pattern-independent operation at speeds in excess of 100 Gb/s. We expand the capability provided by the UNI beyond switching and logic demonstrations to include system-level functions such as packet synchronization, address comparison, and rate conversion. We use these advanced all-optical signal processing capabilities to demonstrate a slotted OTDM multiaccess network testbed operating at 112.5 Gb/s line rates with inherent scalability in the number of users and system line rates. We also report on long-haul propagation of short optical pulses in fiber and all-optical 3R regeneration as a viable cost-effective means of extending the long-haul distance of our OTDM network to distances much greater than 100 km.

Photon-number-resolution with sub-30-ps timing using multi-element superconducting nanowire single photon detectors

A photon-number-resolving detector based on a four-element superconducting nanowire single photon detector is demonstrated to have sub-30-ps resolution in measuring the arrival time of individual photons. This detector can be used to characterise the photon statistics of non-pulsed light sources and to mitigate dead-time effects in high-speed photon counting applications. Furthermore, a 25% system detection efficiency at 1550 nm was demonstrated, making the detector useful for both low-flux source characterization and high-speed photon counting and quantum communication applications. The design, fabrication, and testing of this detector are described, and a comparison between the measured and the theoretical performance is presented.

40-Gb/s all-optical packet synchronization and address comparison for OTDM networks

We demonstrate a novel optical time division multiplexing packet-level system-synchronization and address-comparison technique, which relies on cascaded semiconductor-based optical logic gates operating at 50-Gb/s line rates. Synchronous global clock distribution is used to achieve fixed length packet-synchronization that is resistant to channel-induced timing delays, and straightforward to achieve using a single optical logic gate. Four-bit address processing is achieved using a pulse-position modulated header input to a single optical logic gate, which provides Boolean XOR functionality, low latency, and stability over >1 h time periods with low switching energy <100 fJ.

High-order temporal coherences of chaotic and laser light

We demonstrate a new approach to measuring high-order temporal coherences that uses a four-element superconducting nanowire single-photon detector. The four independent, interleaved single-photon-sensitive elements parse a single spatial mode of an optical beam over dimensions smaller than the minimum diffraction-limited spot size. Integrating this device with four-channel time-tagging electronics to generate multi-start, multi-stop histograms enables measurement of temporal coherences up to fourth order for a continuous range of all associated time delays. We observe high-order photon bunching from a chaotic, pseudo-thermal light source, measuring maximum third- and fourth-order coherence values of 5.87 +/- 0.17 and 23.1 +/- 1.8, respectively, in agreement with the theoretically predicted values of 3! = 6 and 4! = 24. Laser light, by contrast, is confirmed to have coherence values of approximately 1 for second, third and fourth orders at all time delays.

Ultra-wide-range multi-rate DPSK laser communications

We propose and demonstrate a scalable high-sensitivity approach for achieving multi-rate DPSK using a single transmitter and fixed-interferometer-receiver design. Near-theoretical real-time performance is demonstrated over static and fading channels at rates from 2.4Mbps to 2.5Gbps.

Demonstration of 40-Gb/s Packet Routing Using All-Optical Header Processing

We show simultaneous forwarding of two optical packets through a 2times2 spatial switch at 40 Gb/s using only two ultrafast nonlinear interferometers. This demonstrates a scalable all-optical header processing architecture applicable for general network topologies and can lead to reduced size, weight, and power requirements as compared with electronic solutions. Clear open eye diagrams were observed and a packet error rate of 10-6, comparable with current electronic router error rates, was measured for the entire system

40 Gbit/s all-optical XOR using a fiber-based folded ultrafast nonlinear interferometer

Summary form only given. We have shown all-optical XOR at data rates as high as 40 Gbit/s using a novel experimental setup which allows bit error-rate testing of the pseudo-random XOR pattern at the output of the switch. To the best of our knowledge, this is the highest demonstrated rate for XOR operation on two fully-loaded pseudo-random binary streams. The folded UNI incorporating a Faraday mirror reduces polarization instabilities and provides stable performance in an all-fiber switch. Because of the high-speed nonlinear refractive index in fiber, we expect that this logic gate will readily scale to higher data rates.

All-optical pulse regeneration in an ultrafast nonlinear interferometer with Faraday mirror polarization stabilization

We demonstrate the folded ultrafast nonlinear interferometer (FUNI) as a 3R all-optical regenerator. Faraday rotation provides inherent polarization stabilization, and the optical fiber nonlinear medium provides ultrafast operation and switching window tunability. We demonstrate 3R regeneration of 10-Gbit/s data with 5-pJ pulse switching energy and 4-ps timing-jitter tolerance.

Demultiplexing of 80-Gb/s pulse-position modulated data with an ultrafast nonlinear interferometer

Pulse-position modulation may be used to reduce patterning effects arising from gain saturation in all-optical switches employing semiconductor optical amplifiers. We present a novel technique for return-to-zero pulse-position modulation of data suitable for use in optical time-division-multiplexed (OTDM) networks. We demonstrate two methods for all-optical demultiplexing of a pulse-position modulated data stream using an ultrafast nonlinear interferometer. Error-free operation is obtained for demultiplexing from OTDM data rates as high as 80 Gb/s with control pulse energies of 25 fJ.