Tunable Amplification Properties of Distributed Feedback Laser Diodes

This paper describes the tunable amplification properties of a distributed feedback laser diode (DFB-LD), and determines its performance as an optical filter, its tuning range, amplification gain, crosstalk due to submodes, and signal-to-noise ratio. To achieve maximum amplification with the least noise, the DFB-LD injection current is held at or near the threshold value by feedback from an optical detector. The resonant wavelength is precisely controlled over a range of 2.0 nm (254 GHz) by varying the temperature of the DFB-LD, while at the same time the injection current is kept at the optimum value by the above feedback system. By exploiting the tunable amplification properties of DFB-LD, an optical tunable filter was experimentally confirmed.