K.J. Blow

All-optical full adder with bit-differential delay

We experimentally demonstrate an all-optical digital processing circuit that can perform the full addition of binary optical words. The circuit comprises two coupled all-optical regenerative memories. One memory performs the modulo-2 addition and the other memory generates the carry bits from the addition. The two memories are configured to differ in capacity by a single bit so that the full adder operates in bit-differential mode.

Multi-user Quantum Cryptography on Optical Networks

Abstract Quantum cryptography has been shown to be an effective technology for the secure distribution of keys on point-to-point optical links. We show how the existing techniques can be extended to allow multi-user secure key distribution on optical networks. We demonstrate that using network configurations typical of those found in passive optical network architectures any of the current quantum key distribution protocols can be adapted to implement secure key distribution from any user to any other user. An important feature of these adapted protocols is that the broadcaster, or service provider on the network, does not have to be trusted by the two users who wish to establish a key.

All-optical pseudorandom number generator

We demonstrate an all-optical pseudorandom binary number generator comprised of two coupled regenerative optical memories and an XOR gate. Both sub-maximal binary sequences and maximal length pseudorandom sequences were successfully demonstrated.

All-optical binary half-adder

We demonstrate an all-optical binary half-adder which simultaneously generates the bit-serial SUM and CARRY bits from two binary modulated input pulse trains. Additionally, the circuit can implement the XOR function of the two input data streams.

All-optical parity checker with bit-differential delay

We demonstrate an all-optical digital processing circuit that can check the parity of a binary optical word. The circuit operates by repetitively inputting the binary word to be checked into an optical memory whose capacity differs from the repeat time of the input word by one bit. The accumulated parity of the input word is generated by applying the XOR logical function to the repeated input word and the time-shifted stored word in the memory.

All-optical regenerative memory for long term data storage

Abstract We describe a novel all-optical regenerative memory comprising two nonlinear optical switching gates coupled by an optical fibre storage loop. Binary pulse patterns were stored in the memory circuit for periods of several hours. This long term storage corresponds to > 10 billion circulations around the fibre storage loop.

All-optical regenerative memory with full write/read capability

We demonstrate an all-optical regenerative memory with the capability to write and read optical pulses at any time slot in an optical fibre delay line. The memory architecture comprises three TOAD optical switching gates.

All-fiber pulse compression at 1.32 μm

We have constructed a pulse compressor using two different optical fibers. By adjusting the waveguide dispersion it has been possible to produce fibers with positive and negative dispersion at 1.32 microm. We have demonstrated the compression of 130-psec pulses down to our photodiode limit of 70 psec. This is supported by our calculations, which give a theoretical pulse width of 50 psec. This is the first reported demonstration of both an all-fiber pulse compressor and optical pulse compression at 1.32 microm.

Measurement of the refractive-index modulation generated by electrostriction-induced acoustic waves in optical fibers

The refractive-index modulation generated in optical fibers by electrostriction-induced acoustic waves is investigated directly by a pump-probe measurement technique in a 1-km-long fiber Sagnac-loop interferometer. Pump pulses propagating unidirectionally around the loop generate transverse acoustic waves that produce a time-dependent relative phase shift for the probe pulses. The consequent interferometer transmission changes are used as a measure of the acoustic interaction. The acoustic impulse response function of the fiber is measured by use of short optical pulses with a 1-MHz repetition rate. The response consists of a series of peaks separated by ~21 ns with a maximum value of refractive-index modulation of -1.1 x 10(-11) generated by the 230-pJ pump pulses. At a higher pulse repetition rate of 100 MHz additional temporal structure is generated in the 0-5-ns period after the pump pulse, leading to a response similar to that observed in longrange soliton interaction.

Nonlinear optical loop mirrors with feedback and a slow nonlinearity

Abstract We derive a simple model of the behaviour of nonlinear optical loop mirrors in the TOAD/SLALOM configuration in the presence of feedback. Recent experimental results, including the transition from ‘block memory’ to clock division, are explained.