| The relative intensity noise (RIN) is one of the important performance of a laser. At present, the nominal RIN of commercial laser and various measurement results only focus on its high-frequency characteristics, while RIN measurement at the low-frequency gets little attention. Unlike digital optical communication, RIN is an important noise in microwave photonic links. In analog microwave photonic link, the influence of the low-frequency RIN is more serious. In this parper, we researched the RIN measurement of a laser, mainly focusing on how to measure the low-frequency RIN characteristics.We designed a low-noise and low-frequency amplifier module to measure the RIN distribution of the laser. The amplifier module integrates photoelectric detection, signal amplification functions. On one hand, it simplifies the measurement link, on the other hand, it reduces the additional noise in the link. Compared with existing amplifiers, it has better low-frequency and low-noise characteristics. The amplifier module's working bandwidth is 40Hz-4MHz, and it achieves 46dB power gain compared with 50? systems. The significant noise figure of the amplifier is 3dB.Theoretically, the minimum RIN values that the amplifier could measured is as low as -155 dBc / Hz.In this paper, we did several experiments to measure the RIN of the laser,using the existing amplifier and the designed amplifier. Even if the existing amplifier has a minimum frequency of 1kHz, the noise of the amplifier and the photo-detector module have larger values in the low-frequency domain than the high-frequency domain, the distribution of the noise is not stable,these will greatly affect the accuracy of the results. The experiment results show that it has better stable gain in the low-frequency domain and better noise performance, compared with the designed amplifier module. So that designed amplifier module can measure the performace of RIN distribution in the low-frequency domain more accurately. |
PDF Full Text Request