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An analysis of optical phase conjugation using four-wave mixing in a dispersion-shifted fibre is presented. Crosstalk that influences the optical phase-conjugated output signal and stems from nonphase conjugated four-wave mixing is identified for the first time. The impact of conversion fibre length, pump power and input signal power on conversion efficiency, frequency chirp, and crosstalk are given. The analysis shows that a good optical phase conjugation in terms of enhancing conversion efficiency, minimising chirp and crosstalk is obtained by the use of a pump power as high as possible, a conversion fibre length of 20 km and an input signal power of below –5 dBm.

A low-cost continuous-wave supercontinuum source is demonstrated with optical spectral coverage from less than 1200 to more than 2000 nm, using low-cost multimode 975 nm pump lasers. The laser consists mainly of highly nonlinear fibre, Yb/Er doped fibre and 975 nm pump lasers.

Single wavelength soliton transmission at 80 Gbit/s has successfully been performed over 172 km installed fiber. Soliton data with pulse widths of 4.5 ps was transmitted with an average power penalty for all eight time-division-multiplexed channels of 1.3 dB.

The potential for an upgrade of 458 km (eight amplifier spans) installed dispersion shifted fibre (DSF) lines in Sweden to a single-wavelength 40 Gbit/s soliton link without in-line control is numerically studied by extensive system simulations. The polarisation mode dispersion (PMD) is found to be the most important capacity limiting factor. The system tolerates an accumulated differential group delay (DGD) of more than 25% of the bit period.

A comparison of two types of modulators: a semiconductor Mach-Zehnder modulator (integrated with a DFB laser) and a conventional LiNbO3 Mach-Zehnder modulator is given for a 2.5 Gbit/s repeaterless system over 329 km of standard fibre. It is found that the two types of modulators can provide almost identical performance.

A 10 GHz regeneratively modelocked, dispersion-managed and polarisation-maintaining erbium fibre ring laser has been constructed with a variable outcoupling; it produced very stable and nearly chirp-free 3.2 – 8.1 ps sech2 pulses at 1560 nm. It is experimentally shown that the stable operation region of the ML-EFRL is extended by increasing the laser output coupling.

Maximum transmission distance for a 10 Gbit/s signal over non-dispersion shifted fibre using mid-span spectral inversion is mainly limited by additional chirp of the output spectral inverted signal introduced by the spectral invertor and by the conversion efficiency of the spectral invertor. By optimising such a system, the maximum transmission distance is limited to

A coherent optical heterodyne CPFSK receiver with a limiter discriminator (LD) detector, which cannot be degraded by the quantum phase noise of lasers when the frequency deviation ratio h is equal to unity is proposed. The receiver can give the same bit error rate as the ideal digital DPSK system. The expression ½ exp (–SNR) can be considered the upper bound of the minimum error rate of CPFSK-LD detector.

An error probability expression is derived for an optical heterodyne MSK communication system with a limiter-discriminator-integrator detector, subject to IF filtering, AWGN and quantum phase noise of lasers. For a 140 Mbit/s system, a performance criterion is that the laser linewidth ≤500 kHz, for an error probability