WDM Coherent Optical Star Network.

This paper reports the results obtained with a fiber optical star network using densely-spaced Wavelength Division Multiplexing (WDM) and heterodyne detection techniques. The system consists of three lasers transmitting at optical frequencies around 234,000 GHz spaced by a frequency interval of 300 MHz. The lasers are Frequency Shift Key (FSK) modulated at 45 Mb/s. A 4 X 4 optical star coupler combines the three optical signals. The WDM signals received from one of the 4 outputs of the star coupler are demultiplexed by a heterodyne receiver consisting of a tunable Local Oscillator (LO) laser and a balanced-mixer receiver followed by a frequency-discriminator centered at an Intermediary Frequency (IF) of 225 MHz.