Stable four-wavelength ring resonator with hybrid serial-tree configuration for sensing applications

In this paper, a ring laser configuration for fibre sensing applications based on highly erbium-doped fibres is studied. The proposed configuration uses fibre Bragg grating reflectors in order to select the emission wavelengths. The experimental results have demonstrated that the topology arranged in a hybrid serial-tree configuration offers excellent performances in terms of temporal laser stability and optical signal to noise ratio. This setup presents two branches. The first one presents a serial configuration to generate the reference laser, whereas the second branch presents a tree topology. The laser stability and the high signal to noise ratio offered by this configuration has suggested to test it as optical sensor network exploiting differential power measurements. In fact, optical intensity temperature sensors have been included in the second branch of the proposed setup. A comparison of the performances offered by the optical sensors is shown by varying highly erbium doped fibres.