Intensity noise of semiconductor laser diodes in fiber optic analog video transmission

This paper presents an investigation of the effects of laser diode noise on analog video transmission in the HF and VHF bands, which resulted in the development of several designs of graded-index multimode fiber systems that can ignore reflection induced laser noise. The contents of the investigation include: 1) The evaluation of intrinsic laser noise of various laser structures and the evaluation of modulation effects on laser diode noise characteristics. It was found that the relative intensity noise (RIN) is less than -145 ∼ -150 [dB/Hz] when the modulation factor is less than 0.7 for index-guide mode stabilized lasers; 2) The quantitative evaluation of reflected laser beam effects on laser noise characteristics. The maximum laser-coupled reflected optical power that does not increase laser noise was determined as-65 ∼ -73 dB or less depending on the kind of laser structure; and 3) The evaluation of optical power reflected back into the laser in graded-index multimode fiber systems.