Dark fibre networks are considered the key element of future research infrastructures. The ownership of fibre leads to the freedom of development, freedom of choice of technology and freedom of design for research networks, as well as virtually unlimited transmission capacity. This concept has been confirmed by the new design of the GÉANT2  network, where majority of links will be based on dark fibre. At the same time, while the GÉANT2 network has been upgraded to a level of technology that allows multiple10 Gbit/s connections between most of the GÉANT2 partners, many countries of Eastern Europe are still suffering from insufficient connectivity to the Internet. It is expected that a strong role in the development of pan-European research network can be played by so called “Cross Border Fibres” (CBF), owned and operated by NRENs. This paper provides an overview of the PIONIER infrastructure and the Porta Optica initiative, which aims to improve the connectivity of Eastern European NRENs to GÉANT2, using a CBF infrastructure.