Detector-Free Fiber-Based Bidirectional Symmetric Communication Scheme Based on Compound States of Two Mutually Coupled Discrete-Mode Lasers

Most modern high-data-rate optical communication systems require at each end a light source to transmit the data and a detector to receive the data. In order to realize a communication scheme where the transmitter unites with the receiver, we take advantage of a coupled injection-locked semiconduct. From the theoretical description of two mutually coupled diode lasers using a set of six nonlinear differential-delay equations we outline the stable compound cavity solutions of this system and investigate their dependencies in terms of locking bandwidth, coupling strength and coupling phase. From these modeling results we then design a remarkably simple communication system without any additional detectors that exploits compound laser states of different frequency detunings of the coupled laser system as information carriers with simultaneous upstream information of the first laser and downstream information of the second laser. The data recognition is accomplished by evaluating the compound state utilizing the change in the terminal voltage of both lasers (laser-as-detector principle) with respect to their solitary case (i.e., the terminal voltage of the uncoupled lasers), yielding the message via the agreed decoding scheme. The functionality of the principle had been demonstrated by a table-top experiment with good error-free transmission and potential to improve the transmission speed of this proof-of-principle demonstration. Our concept reduces the complexity compared to conventional transmission systems, thus providing the potential to significantly reduce the costs of the overall transmission setup an,d in particular, transferring the concept to other challenging wavelengths and other semiconductor lasers. Since the optical signal then no longer needs to be detected by an optical detection unit, the amount of optical components required for ordinary data transmission is reduced.