Basic Concept

Optical fibre amplifiers have revolutionised optical fibre networks. The main reason for the strong impact that they have had and will have on data communication is that they are unique in simultaneous amplification of optical signals with different rates or data formats over a broad spectral region. When using optical amplifiers instead of semiconductor amplifiers, one can remove the barrier of narrow and fixed bandwidth of electrical repeater. Among different types of optical fibre amplifier the EDFA is the most commonly used. The basic principle is the optical pumping of a material with which optical fibres can be doped. Lasers and optical pumping of doped materials reach far back to the roots of the early laser techniques, for example the Nd doped YAG laser and amplifier. This and the fact that a great variety of physical aspects, combined with practical training with lasers and optical fibres, makes this experiment a valuable tool for the education of students as well as teachers.

Experimental Set-up

Within this experimental set-up, an Erbium doped fibre is optically pumped by a laser diode which emits a wavelength of 980 nm. The pump, as well as signal radiation, is coupled via a wavelength division multiplexer (WDM) to the Erbium doped fibre (EDF).
The exit of the EDF is connected to a fibre telescope (FT-01) which generates an almost parallel output beam. Using the RG1000 filter (F1), the pump radiation is blocked in such a way that the subsequent beam consists only of a radiation with a wavelength above 1.2 µm. The so filtered radiation is tranferred back by fibre telescope (FT-02) and can be connected either to the photodetector or optical multichannel analyzer slot-in module.