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Frequency confinement of FDM optical signals to a comb of equally spaced frequencies has been demonstrated. The result was achieved by locking the frequencies of three optical sources to three different resonances of a fibre Fabry-Perot resonator. The frequency spacing between the frequency-locked signals was adjusted to be 500 MHz, the spacing between adjacent resonances, or a multiple of this value. Implementation of the frequency stabilisation circuit requires only a fibre Fabry-Perot resonator, a photodetector and simple electronics. Such a simple circuit provides the means to frequency-stabilise a large number of FDM optical signals originating from the same location.

We describe the first 1.55 μm InGaAsP optical-fibre composite-cavity laser with an integrated single-mode-fibre output port. Mode-locked pulsewidths of 4.8 ps at a 2 GHz repetition rate, with peak powers of 56 mW, are demonstrated. These are the shortest reported mode-locked pulses from InGaAsP lasers.

The effect of an optical preamplifier on the sensitivity of a heterodyne receiver near the shot noise limit is measured. Without the preamplifier, the sensitivity of the receiver is 76 photons/bit for an FSK modulated signal at 45 Mbit/s received with a BER of 10−9(2.8 dB from the shot noise limit). Optical preamplification degrades this sensitivity by 9.6 dB. The degradation expected from the amplifier spontaneous emission noise is shown to be very close to the measured value.

A problem in frequency-tuning of external-cavity lasers is mode-hopping between neighbouring external-cavity modes. We demonstrate a new interferometric method for monitoring mode-hoping and an automatic control circuit for a 1.3 μm grating external-cavity laser that maintains single-mode operation when the lasing frequency is tuned.

We describe the design and performance of an experimental two-channel optical time-division multiplexed fibre transmission system operating at a wavelength of 1.3 μm and a bit rate of 8 Gbit/s. Transmission over 8 km of single-mode fibre with low crosstalk and transmission error rates as low as 10 -10 is demonstrated.

We describe a travelling-wave optical amplifier operating at a wavelength near 1.3 μm. We demonstrate a fibre-amplifier-fibre gain of 13-1 dB with a gain variation of 13.1 dB. The fibre-amplifier coupling loss is 4.5 dB/interface and the amplifier facet mean reflectivity is 0.04%.

A high-power, high-speed GaInAsP/InP laser operating at a 1.3μm wavelength is described. The laser is obtained with three epitaxial growth steps and has semi-insulating InP blocking layers resulting in low parasitic capacitance. A 3 dB bandwidth of 14.7 GHz together with 38 mW output power has been achieved.

We demonstrate an electro-optic sampling system based on a gain-switched InGaAsP injection laser. The system has a temporal resolution of 18ps and is used for noninvasive probing of waveform internal to a GaAs monolithic integrated circuit operating at 2.4GHz.

We demonstrate a new electro-optic sampling system for the measurements of fast electrical waveforms at gigahertz repetition rates. The system uses a mode-locked InGaAsP injection laser as a source of sampling pulses and employs the electro-optic effect in the GaAs substrate of a microstrip line.

Active mode-locking of a 1.55 μm wavelength InGaAsP laser at repetition rates up to 20 GHz is reported. The pulsewidth is 5 ps at 20 GHz, with a peak pulse power of 18 mW coupled into a single-mode output fibre.

We report the first antireflection coatings for fibre pigtailed Ti:LiNbO3 waveguide devices optimised for the 1.55 ?m wavelength range. The coatings are single-layer, electron-beam-evaporated yttrium oxide films. A reflection of ?35 dB, sufficiently low for operation in conjunction with single-frequency lasers, has been demonstrated.

An InGaAsP 1.3 μm amplifier-modulator integrated with a laser which is mode locked in a fibre resonator is demonstrated. Transform limited pulses with 25 ps duration were gated by the amplifier-modulator at a bit rate of 1.05 Gbit/s with an on/off ratio of 20 dB.

We report transmission over 57 km of single-mode fibre in a two-channel, 8 Gbit/s optical time-division multiplexed system experiment using a transmitter with a single laser and a semiconductor optical power amplifier at the transmitter output. The amplifier operates with a net gain of 11.5 dB, which corresponds to 0.8 dB gain compression, and a fibre coupled output power of +6 dBm. The amplifier facet output power for which the gain is compressed by 3 dB is +13 dBm. The experimental system uses neither an isolator nor an optical filter.

A uniquely designed, mechanically tunable, bulk optical isolator for the 1.2 to 1.7 μm wavelength range is described. The isolator can be tuned for isolation better than 32 dB over the operating wavelength range with a forward loss ranging from -3.6 dB at 1.2 μm to -0.8 dB at 1.6 μm.

Temporal and spectral characteristics of single-longitudinal-mode short-coupled cavity (SCC) InGaAsP injection lasers in the 1.5 ?m wavelength range under high-frequency (1?7.5 GHz) direct modulation are reported. The effects of modulation on the spectral broadening and chirping of the longitudinal modes were studied. Predominantly single-longitudinal-mode operation under direct high-frequency modulation was achieved by compromising the on/off ratio.

The authors report active mode-locking of an extended-cavity silicon chip Bragg reflector laser. Pulses of 27 ps duration at repetition rates up to 7 GHz, have been achieved with a controllable narrow optical spectrum. >

An optical WDM star network consisting of three lasers transmitting at about 234 000 GHz, spaced by 300 MHz, has been used to demonstrate dense packing of WDM signals. The three optical signals, FSK-modulated at 45Mbit/s, are multiplexed by a 4 × 4 star coupler and demultiplexed by a balanced heterodyned receiver. Receiver sensitivity is -61dBm for a BER of 10 -9 , or 113 photons/bit, which is 4.5dB from the shot noise limit and represents the best sensitivity yet reported for FSK modulation. The results indicate that 100 000 users in a 10km radius could be interconnected with such a system.

We describe the fabrication of microlenses on stressed cladding flattened polarisation-maintaining fibres. Coupling efficiencies of 42% and polarisation decoupling greater than 20 dB are demonstrated.

We report time-resolved gain and noise spectra measurements in an electrically pulsed travelling-wave optical amplifier. We demonstrate a modest (60A) blue shift in the gain spectrum and high (25 dB) gain in a 250μmlong amplifier driven by a 1 GHz, 60 ps pulse train.

We describe the structure and performance characteristics of an InGaAs/InP multiple-quantum-well (MQW) electro-absorption buried-mesa optical modulator. The device is fabricated with two metal-organic chemical-vapour-deposition (MOCVD) growth steps, wherein small-area circular (40μm diameter) PIN diodes are buried with Fe-doped semiinsulating (SI) InP regrowth. The modulator has a relatively low insertion loss (4.5 dB) with 25% modulation depth and very high modulation bandwith (5.3 GHz) operating at 1.62μm wavelength.

We have demonstrated an external amplifier-modulator integrated with a cleaved-coupled-cavity injection laser on the same 1.3 μm InGaAsP/InP laser chip. The maximum available gain was 20 at an input power of −19.2 dBm, and it reduced to 10 at an input power of −10.5 dBm. High on/off extinction ratios and side-mode suppression >100:1 were achieved at about 1 Gbit/s (NRZ) modulation rate.

We report the crosstalk degradation caused by an optical amplifier in a densely spaced four-channel heterodyne FSK system. A maximum receiver sensitivity of 250 photons/bit is obtained for an optimum input signal level. This result is 5dB poorer than the sensitivity obtained in the absence of an optical amplifier.

We report high-speed measurements of an InGaAs PIN photodiode in a millimetre-wave coaxial mount. The photodiode has an impulse response (including diode, parasitics and connector) of 9 ps FWHM and a 3 dB bandwidth of 67 GHz. This is the largest bandwidth reported to date for a photodiode in a coaxial mount with a connector.

We demonstrate an eleclro-optic sampling system for the characterisation of very high-speed, long-wavelength photodetectors. The system uses a mode-locked InGaAsP injection laser operating at 1.3 μm as the source of pump and sampling pulses.

An experimental four-channel optical time-division multiplexed transmission system is described, and the first demonstration of fibre transmission at a bit rate of 16Gbit/s is reported. In this experiment, data at 16Gbit/s have been transmitted over 8 km of fibre with a bit error rate below 10-9.

Active mode-locking of a 1.3 μm ridge-waveguide laser in a multimode optical fibre resonator is reported. Transform-limited pulses of 30 ps duration have been generated at repetition rates of up to 10 GHz.

We present high-resolution gain spectra measurements of a 1.5 μm near-travelling-wave amplifier for both TE and TM polarisation. We use 49km of single-mode fibre at the amplifier input to demonstrate a reduction in the effective bandwidth of the amplifier caused by a combination of dichroism in the amplifier and the polarisation dispersion present in long lengths of fibre.