Effect of laser diode operating parameters on a chaotic signal generated by a filtered optical FLM

In this experimental study, a quantum well edge-emitting laser diode with a 1310 nm emitting wavelength is used as a light source for an optical fiber loop mirror (FLM). The last is constructed from two optical fiber couplers or splitters with a 50:50 splitting ratio. The novelty is introduced by the insertion of narrow filter fiber Bragg grating (FBG) inside the loop. In this situation, the loop mirror output is observable from two positions: the transmission side and the reflection side. An optical isolator is inserted just after the FBG to guarantee a unidirectionally circulated signal. It is established that to achieve the chaotic signal, the laser source voltage is changed from 1.1 to 2 volts within the available operating range. The amplitude of the transmitted spectrum is larger than the amplitude of the reflected spectrum and reaches 40 (mV). Only reflected a specific wavelength which fulfils Bragg condition whilst the remaining wavelengths is transmitted through grating regions without any loss. Several peaks and clear changes with the variation in voltage and current of the laser are due to a result of optical feedback, which generates nonlinearity properties in the circuit, and this effect appears on two output spectra of the loop mirror.