A. Bjarklev

Polarization-insensitive widely tunable wavelength converter based on four-wave mixing in a dispersion-flattened nonlinear photonic Crystal fiber

Polarization-insensitive widely tunable wavelength conversion has been demonstrated using four-wave mixing in a 64-m-long dispersion-flattened nonlinear photonic crystal fiber. A 3-dB conversion range over 40 nm (1535-1575 nm) is obtained with a flat conversion efficiency of -16 dB and a polarization sensitivity of less than 0.3 dB. The measured power penalty is less than 1 dB for a 10-Gb/s converted nonreturn-to-zero signal at 10/sup -9/ bit-error rate.

Widely tunable wavelength conversion with extinction ratio enhancement using PCF-based NOLM

A widely tunable wavelength conversion scheme has been demonstrated using a 64-m-long dispersion-flattened high-nonlinearity photonic crystal fiber in a nonlinear optical loop mirror. Wavelength conversion range of over 60 nm with a 10-Gb/s return-to-zero signal was obtained with the output extinction ratio (ER) maintained above 13 dB. The proposed scheme can also improve the output ER and remove the bit-error-rate floor if a degraded signal is used.

Design of polarization-preserving photonic crystal fibres with elliptical pores

In this paper we discuss a microstructure of air capillaries with an elliptical cross section in a tread of glass, which gives an opportunity for the creation of a polarization-preserving fibre with very small beat length between the fundamental modes of different polarization. It is shown here that the fibre can be designed in such a way that only fundamental modes are guided. However, it is not possible with this process to create a photonic crystal fibre which can guide only one fundamental mode.

Applications and Future Perspectives

In the previous chapters of this book, we have introduced the fundamental properties of photonic crystal fibres ranging from fundamental definition of photonic bandgap structures over numerical modelling to fabrication of these new fibre types. We have also discussed the fundamental differences between index-guiding PCFs and bandgap-guiding PCFs, and some examples of fibre structures and properties have been presented. However, the research field is still very young, and numerous new results and applications appear as the fibres are tested and investigated by more research groups and companies. For this reason, it is a very significant challenge to try to give an up-to-date picture of the most relevant applications of photonic crystal fibres, and just between the time of writing this chapter and to the point, when the book is printed, novel findings will be added to the field. For this reason, our ambition with the present chapter is more modest, since we have chosen to present some of the applications and ideas for the PCF technology, which primarily provides a good impression of the wide range of possibilities provided by these waveguides rather than necessarily covering all of the latest research results.

Flat supercontinuum generation in a dispersion-flattened nonlinear photonic crystal fiber with normal dispersion

We demonstrate a flat supercontinuum generation over 185 nm in a dispersion-flattened nonlinear photonic crystal fiber working in the normal dispersion regime only, with all-fiber configuration and only 10 mW mode-locked pump pulses

Fabrication of Photonic Crystal Fibres

The idea of producing optical fibres from a single low-loss material with microscopic air holes goes back to the early days of optical fibre technology, and already in 1974 Kaiser et al. [4.1] reported the first results on singlematerial silica optical fibres. In the early days — as well as today — the key issues have been to obtain a desired fibre structure for a given application, and maintain this structure for very long fibre lengths. It will, generally, be needed that the fibre attenuation is kept at a rather low level, and the acceptable attenuation level will be given by the specific application. In this chapter, we will address the fundamental issues of fabrication of photonic crystal fibres, by first discussing the most commonly used preform fabrication method. Secondly, we will report details about the fibre drawing and coating procedure. Furthermore, we will discuss how additional doping techniques are needed for providing hybrid fibre types (such as the holeassisted lightguide fibre (HALF) [4.6]) combining the approach of microstructuring with index-raised doped glass or active dopants such as rare-earth ions needed for new amplifiers and lasers. The chapter will also shortly address the issues of photonic crystal fibres in low-melting-point glasses and polymers.

S/C/L-band wavelength conversion by cross-polarization modulation in a dispersion-flattened nonlinear photonic-crystal fiber

We study the conversion bandwidth of cross-polarization-modulation based wavelength conversion scheme. Both numerical and experimental results show that the conversion bandwidth can be extended to cover S-, C- and L-band for 10 Gb/s non-return-to-zero signals

All-optical pulse compression and reshaping by spectral filtering from self-phase modulation in a nonlinear photonic crystal fiber

We demonstrated all-optical pulse compression and reshaping by optical filtering from a self-phase modulation-broadened spectrum in a nonlinear photonic crystal fiber. A recirculating configuration is employed to increase the pulse compression efficiency.

All-optical signal regeneration based on pump-modulated four-wave mixing in a nonlinear photonic crystal fiber

All-optical signal regeneration has been demonstrated based on four-wave mixing in a nonlinear photonic crystal fiber. The output extinction-ratio is improved and a negative power penalty is obtained in a 10 Gb/s BER measurement.

All-optical wavelength multicasting using four-wave mixing in a dispersion-flattened nonlinear photonic crystal fiber

All-optical wavelength multicasting at 4/spl times/10 Gb/s has been demonstrated based on four-wave mixing in a nonlinear photonic crystal fiber. Based on the dispersion-flattened characteristic of our fiber, a broadband operation has been obtained.