Development of bi-doped fibre amplifiers and lasers & broadband Er-doped multi-element fibre amplifiers

The demand for fibre optic communication is continuously increasing over the years. This is due to the increased accessibility to the World Wide Web using internet of things. The capacity of current fibre optic communication through the single mode fibre is limited by the amplification bandwidth of Er-doped fibres. To increase the capacity of fibre optic communication research community around the world are proposing different approaches. One of them is to use the low loss window (1260-1625nm) of silica optical fibres by developing efficient fibre amplifiers and lasers. Another one is to use novel fibres such as multi-core fibres, multi-mode fibres and multi-element fibres (MEFs) for space division multiplexing in the C-band (1525-1565nm). In this thesis, we developed amplifiers and lasers within the wavelength band from 1150-1625nm using Bi-doped and multi-element Er-doped fibres. Here, we investigated the fabrication of Bi-doped optical fibres in different glass hosts (aluminosilicate and phosphosilicate) using MCVD-solution doping technique. Bi-doped aluminosilicate fibres are used to develop an amplifier with 12dB gain at 1180nm. Bi-doped phosphosilicate fibres are used to develop amplifiers and lasers in the second telecommunication band from 1300-1360nm. An all-fibre Bi-doped phosphosilicate amplifier with a 25dB at gain in a 40nm bandwidth from 1320-1360nm is reported. Also, a Bi-doped fibre laser operating at 1360nm with an output power of 110mW, and a picosecond pulsed mode-locked fibre laser operating at 1340nm with a peak power of 1.15W, are demonstrated. These amplifiers and lasers have important applications in medicine, astronomy and optical fibre communication. In addition, we also discussed the novel fibres known as MEFs and developed core and cladding pumped broadband amplifiers covering 1500-1620nm using multi-element Er and Er/Yb-doped fires, respectively.