The study of bismuth doped fibres and the development of broadband bismuth doped fibre amplifiers

Abstract

The demand for capacity of optical fibre communication networks has been continuously increasing over the years. One effective approach to meet the growing requirement is to develop efficient amplifiers capable of working in the extended wavelength bands beyond C- and L-bands, i.e. O-, E-, S- and U-bands (covering from 1260-1675 nm), which also lie within the low-loss window of transmission silica fibres. The broadband near-infrared (NIR) luminescence properties of bismuth (Bi)-doped silica fibres which span the O-, E-, S- and U-bands indicate that Bi is a promising dopant to develop optical amplifiers in these wavebands. In this thesis, I fabricated the Bi-doped phospho-silicate fibres (BPSFs) jointly with other fabricators using (MCVD)-solution doping technique and fibre drawing tower. I characterised the basic parameters of the BPSFs, such as the absorption spectrum, unsaturable loss (UL), OH concentration, background loss (BL), fluorescence lifetime, absorption and emission cross sections. The absorption at 1.2-1.3 µm wavelength band of different BPSFs are in the range of 0.2-1.6 dB/m. The UL of the current BPSFs can be reduced below 20%. The fluorescence lifetime at 1267 nm of BPSFs is measured to be 760±20 µs. The absorption and emission cross section spectrum of BPSFs is analysed using saturation power method for the first time, and the results showed a maximum absorption cross section of 1.8 pm² at around 1.29 µm. Using the in-house fabricated BPSFs, I developed optical amplifiers operating in the O-band (1300- 1360 nm) and O+E-band (1345-1460 nm), and analysed the Bi-doped fibre amplifier (BDFA) performance including gain, noise figure (NF) parameters and their temperature dependent characteristics. In the O-band BDFA development, a flat gain of 25±1 dB from 1320-1360 nm and a high gain of 40 dB at around 1360 nm are achieved for a -23 dBm input signal using the single pass and double pass amplifier configurations, respectively. In the O+E-band BDFA development, a wideband gain of >20 dB is obtained for a -23 dBm input signal over a 115 nm bandwidth from 1345- 1460 nm. In addition, I designed and fabricated the W-type BPSFs, to develop BDFAs operating in the short O-band (1270-1320 nm).

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Identifiers

ORCID for Jayanta Sahu: orcid.org/0000-0003-3560-6152

ORCID for David Richardson: orcid.org/0000-0002-7751-1058

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