Compare and Contrast hollow core fibers for high power delivery and negative curvature hollow core fibers. Essay answers are limited to about 1000 words (3800 characters maximum, including double spaces). Compare and Contrast hollow core fibers for high power delivery and negative curvature hollow core fibers. Essay answers are limited to about 1000 words (3800 characters maximum, including double spaces). Solution NC-HCF:-NEGATIVE curvature hollow core optical fiber (NC-HCF) is a novel hollow core optical fiber (HCF) which has emerged over the last few years. NC-HCF is characterized by the inverted curvature of its core wall, and usually exhibits multiple spectral transmission bands of low attenuation. The simple structure of the fiber cladding allows flexible tailoring of NC-HCFs design and dimension for specific wavelengths and applications. Since their first appearance NC- HCFs have been applied in high power/ultrafast laser delivery and several other applications. This paper comprises eight sections:It consists of a brief history of NC-HCF, while the optics of NC-HCF will be discussed. From the guidance properties of NC-HCFs are collated and summarized including mode attenuation, bending loss, dispersion and nonlinearity. reviews some applications of NC-HCFs and contains conclusions. Hollow core negative curvature fibre (HC-NCF):Hollow core negative curvature fibre (HC-NCF) is another kind of leaky HCF, which features negative curvature of the core boundary The importance of curvature of the core boundary in HCF was firstly discovered in Kagome fibres by Wang et al. in 2010. A Kagome fibre with negative curvature of the core boundary exhibited an unexpected lower attenuation than regular ones. A series of subsequent experiments confirmed the function of the negative curvature core wall in the reduction of attenuation in Kagome fibres. Later in 2010 Gérôme et al. demonstrated that the complex structure of the cladding has a negligible effect on the confinement loss of Kagome fibre. At the same time, Vincetti and Setti numerically studied HC-NCF with a simplified cladding systematically and revealed that the coupling interaction between the core mode and cladding mode decides the high loss transmission spectral regions of HC-NCF. In 2011, Pryamikov et al. fabricated the first silica HC-NCF without lattice structure in the cladding. They demonstrated that light can be transmitted through a 63 cm length of silica fibre at 3 m wavelength even though. The fused silica exhibits very high material absorption in this spectral region. Afterwards, Kosolapov et al. extended the transmission window in a similar structured HC-NCF to 10.6 m for CO2 laser by using chalcogenide glass instead of silica as the fabrication material. In 2012 during the course of this thesis I designed, fabricated and characterised a silica HC-NCF with low loss transmission in the mid-infrared spectral region from 3 µm to 4 µm, with minimum attenuation of 34 dB/km at a wavele.