Abstract

We report the performance of a dense frequency division multiplex (FDM) coherent optical fiber star network. This system uses random digitally tuned optical frequency synthesizers for generating the optical carriers for the transmitters. It also utilizes digitally tuned heterodyne receivers which can randomly select the desired channel from the received FDM signal (Fig. 1). The system consists of six transmitters, FSK modulated at 200 Mbit/s, tunable (by computer command) to the same fifty optical frequencies spaced by 2.5 GHz (Fig. 2). Monolithic multicontact tunable MQWDBR lasers,¹,² operating at 1.5 μm, are used to generate the optical signals. The comb of frequencies is obtained by storing in a personal computer (PC) the tuning current values to set each laser frequency to a resonance of a single fiber Fabry-Perot (FFP) cavity³ (Fig. 1). Each laser is frequency locked to its selected resonance by an independent error signal.⁴ The error signal is obtained by photodetecting the output of the FFP fed by the FDM signal (Fig. 1). The amplified photocurrent is then correlated with the six different modulating FSK signals. The result yields the separate error signals needed for independently locking each transmitter.⁴ This is the first reported network that utilizes digitally tuned transmitters and receivers, to our knowledge.

© 1990 Optical Society of America