Effects of ASE noise and total injected power on Optical Injection Locking

Abstract

Optical Injection Locking (OIL) phenomena has substantial importance in commu- nications systems, making stable locking with low injected power a major challenge. Additional considerations involve that nature of oscillations in the lasers is random, provoked by temperature and spontaneous noise. An OIL setup was constructed in order to get stable injection locking with the low- est input power from the master laser. Moreover, with the aim of improving this parameter, a phase locked loop (PLL) was developed. This addition requires the initial setup to include a modulator, that in this case works at 6 GHz. The mod- ulation was verified, ensuring that side bands are distanced enough, preventing the slave laser from locking at unwanted frequency. Previous studies show that there is an optimum input slave power that minimizes the phase noise. We measure the phase noise applying two type of power at the input, ASE noise and master laser power. The experiment aims to discover the pa- rameter that limits the OIL, whether it is the total input power into the slave laser (keeping OSNR constant) or the master power. An appropriate topology was used to differentiate between the different sources of power. The main reason to design this experiment is advance in the understanding of the factors that influence OIL. To achieve this, we prepared two set of measurements tuning different parameters. The first test keeps ASE noise power constant while the master laser power is swept. For the second test, OSNR is fixed and total power is changed. Comparing the resu rovide knowledge on the behaviour of the locking bandwidth.