Investigation of High Linearity DFB Lasers for Analog Communications

High-linearity, low-noise DFB lasers are necessary for analog optical communications, including subcarrier multiplexed systems, wireless personal communication systems (PCS) service and phased array radar. In this thesis, we examine the dynamic range and distortion for a Fujitsu DFB laser. We extract parameters from the device and use these parameters to simulate the distortion characteristics. We measure the spurious free dynamic range (SFDR) and find that it peaks at a certain current bias; we hypothesize that this maximum is related to a cancellation effect between the gain compression and the spatial hole burning nonlinearities in the laser. We also measure the SFDR versus frequency and find that the dynamic range is relatively insensitive to temperature changes between 300 and 700 MHz. Based on these findings, we make suggestions for ways to improve the laser performance and reduce the packaging cost. Thesis Supervisor: Professor Rajeev Ram Title: Assistant Professor of Electrical Engineering and Computer Science