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High-power laser delivery with near-diffraction-limited beam quality is typically limited to tens of metres distances by nonlinearity-induced spectral broadening inside the glass core of delivery fibres. Anti-resonant hollow-core fibres offer not only orders-of-magnitude lower nonlinearity but also loss and modal purity comparable to conventional beam-delivery fibres. Using a single-mode hollow-core nested anti-resonant nodeless fibre with 0.74 dB km−1 loss, we demonstrate the delivery of 1 kW of near-diffraction-limited continuous-wave laser light over a 1 km distance, with a total throughput efficiency of ~80%. From simulations, a further improvement in transmitted power or length of more than one order of magnitude should be possible in such air-filled fibres, and considerably more if the core is evacuated. This paves the way to multi-kilometre, kilowatt-scale power delivery that is potentially useful not only for future manufacturing and subsurface drilling but also for new scientific possibilities in sensing, particle acceleration and gravitational wave detection.Microstructured optical fibre is shown to be able transmit high-power laser light over long distances with high throughput efficiency.

We review recent work on all-fiber (long-period fiber grating) devices for optical pulse shaping, particularly flat-top pulse generation, down to the subpicosecond range and their application for nonlinear switching (demultiplexing) of optical time-division multiplexed (OTDM) data signals in fiber-optic telecommunication links operating up to 640 Gbit/s. Experiments are presented demonstrating error-free 640-to-10 Gbit/s demultiplexing of the 64 tributary channels using the generated flat-top pulses for temporal gating in a Kerr-effect-based nonlinear optical loop mirror. The use of flat-top pulses has critical benefits in the demultiplexing process, including a significantly increased timing-jitter tolerance (up to ~500 fs, i.e., 30% of the bit period) and the associated improvement in the bit-error-rate performance (e.g., with a sensitivity increase of up to ~13 dB as compared with the use of Gaussian-like gating pulses). Long-period fiber grating pulse shapers with reduced polarization dependence are fabricated and successfully used for polarization-independent 640-to-10 Gbit/s demultiplexing experiments.

We review recent experimental demonstrations of Tbaud optical signal processing. In particular, we describe a successful 1.28 Tbit/s serial data generation based on single polarization 1.28 Tbaud symbol rate pulses with binary data modulation (OOK) and subsequent all-optical demultiplexing. We also describe the first error-free 5.1 Tbit/s data generation and demodulation based on a single laser, where a 1.28 Tbaud symbol rate is used together with quaternary phase modulation (DQPSK) and polarization multiplexing. The 5.1 Tbit/s data signal is all-optically demultiplexed and demodulated by direct detection in a delay-interferometer-balanced detector-based receiver, yielding a BER less than 10−9. We also present subsystems making serial optical Tbit/s systems compatible with standard Ethernet data for data centre applications and present Tbit/s results using, for instance silicon nanowires.

A 40GHz clock with low jitter is recovered from a 640Gbit/s optical time-division multiplexed (OTDM), single-polarised, return-to-zero PRBS data signal. The clock recovery circuit is an injection-locked loop which contains a 40GHz Gunn oscillator, a 40GHz pulse source, and a semiconductor optical amplifier (SOA) assisted by a filtered chirp as optical phase comparator.

A 40 GHz clock with low jitter is recovered from a 640 Gbit/s optical time-division multiplexed, single-polarised and return-to-zero PRBS data signal. The clock recovery circuit is an injection-locked loop which contains a 40 GHz Gunn oscillator, a 40 GHz pulse source, and a semiconductor optical amplifier assisted by a filtered chirp as optical phase comparator.

A 1.28 Tbaud data signal is demonstrated, which is the highest symbol rate yet reported. The data signal is formed by optical time-division multiplexing of 128 data channels at 10 Gbit/s OOK in a single polarisation. The generated 1.28 Tbit/s data signal is demultiplexed in a nonlinear optical loop mirror, resulting in error-free performance with a BER < 10^sup -9^ for all 128 demultiplexed channels.

In this paper, the pre-scaled clock recovery of a serial 640 Gbit/s data signal is demonstrated, using a quasi-phase-matching periodically poled lithium niobate module as an ultrafast phase comparator in an optoelectronic phase-locked loop.