Bidirectional transmission over 11 km of single-mode optical fibre at 34 Mbit/s using 1.3 μm LEDs and directional couplers

Bidirectional Digital Optical Fiber System with Transmitters Synchronized with Receivers

“…At one end of the system, which is denoted in Fig. 1 as terminal, the clock is recovered from received data and delayed for time interval τ which is approximately (1) where Τ is a bit interval, θ is the transmit optical pulse width and t d is the pulse delay from a source, through transmitter, reflection loop and back to receiver. This way, the transmit pulses reflected at the coupler and connector appear at the receiver approximately in the middle between decision moments.…”

“…Bidirectional transmission is usually achieved by wavelength-division multiplexing (WDM). Some authors propose using the same wavelengths for each direction of transmission with separation of signals going to and from terminal by directional couplers [1][2][3]. Such devices are usually simpler than devices for wavelength separation (e. g. using interference filters [4]) and often introduce less attenuation.…”