High-Capacity Directly Modulated Optical Transmitter for 2-μm Spectral Region

The 2-µm wave band is emerging as an attractive region for optical communications because of several major advantages. First of all, the Hollow-Core Photonic Band Gap Fiber (HC-PBGF), which has ultra-low nonlinearity and low latency, has its minimum loss within the 2-µm wavelength band. Secondly, the Thulium-doped fiber amplifier that operates in this spectral region provides significantly more bandwidth than the Erbium-doped fiber amplifier. In this paper we demonstrate a single-channel 2-µm transmitter capable of delivering >52 Gbit/s data signals, two times more capacity than previously-demonstrated. To achieve this we employ Discrete Multi-Tone (DMT) modulation via direct current modulation of a Fabry-Perot semiconductor laser. The 4.4-GHz modulation bandwidth of the laser is enhanced by optical injection locking, providing up to 11 GHz modulation bandwidth. Transmission over 500 m and 3.8 km samples of PBGF is demonstrated.