Control of period-one oscillation for all-optical clock division and clock recovery by optical pulse injection driven semiconductor laser

The period-one oscillation produced by an external optical pulse injection driven semiconductor laser is applied to clock recovery and frequency division. By adjusting the repetition rate or injection power of the external injection optical pulses to lock the different harmonic frequencies of the period-one state, the clock recovery and the frequency division （the second and third frequency divisions） are achieved experimentally. In addition, in frequency locking ranges of 2 GHz and 1.9 GHz, the second and third frequency divisions are obtained with the phase noise lower than 100 dBc/Hz, respectively. Our experimental results are consistent well with the numerical simulations.

Period Doubling in a Fabry-Perot Laser Diode Subject to Optical Pulse Injection

Experimental study and numerical simulations of the period doubling of injected optical pulses in Fabry-Perot laser diodes are presented. In our experiments, the period doubling is achieved within a wide input frequency range and the period doubling of the injected optical pulses with 6.32 GHz repetition rate is investigated in detail. The obtained experimental results indicate that period doubling occurs at an appropriate injected optical power level when the bias current of the Fabry-Perot laser diode is located in lower ranges. Moreover, the experimental observed features have been numerically demonstrated by using a coupled rate-equation model. Numerical simulations are consistent with the experimental results.

Design of Traffic Light Based on Field Programmable Gate Array

The use of fixed-time traffic lights for road traffic control has the disadvantage of low traffic efficiency. In order to optimize the vehicle traffic at the intersection, this paper proposes a design scheme of a real-time control system for road intelligent traffic lights based on FPGA. The system adopts the polling control model, the vehicle detector detects the arrival rate of vehicles, and obtains the corresponding traffic light green time length according to the traffic rules and polling model theory. Using Altera’s Cyclone IV series EP4CE15E22C8 chip as the development platform, a specific design plan is given. The circuit mainly includes program-controlled amplifier module, AD acquisition module, cross-correlation calculation module, serial port transmission and Lab-VIEW module. The system can realize the intelligent adjustment of traffic lights. Different vehicle arrival rates are detected at different times, so that the corresponding traffic light configuration time length changes accordingly. This intelligent adjustment controls road traffic and makes the main and branch roads coordinate and cooperate, thereby improving the traffic efficiency of the intersection.