KEYWORDS: Particle swarm optimization, Temperature control, Field programmable gate arrays, Thermal stability, Particles, Semiconductor lasers, Control systems, Mathematical optimization, Laser stabilization, Control systems design
The output power and wavelength of semiconductor lasers are mainly affected by operating temperature. In order to improve the stability of Laser Diode (LD), a temperature control system is designed in this paper. This system adopts an advanced Particle Swarm Optimization (PSO) algorithm to resolve real-time Proportional-Integral-Derivative (PID) parameters for different input, which is implemented on field-programmable gate arrays (FPGA) with excellent parallel performance. Experimental results show that the LD can stabilize with temperature stability of 0.20% within 1 hour of operation, output optical power stability of 0.05%, and the deviation of optical wavelength 0.03𝑛𝑚.
KEYWORDS: Fiber amplifiers, Control systems, Field programmable gate arrays, Raman spectroscopy, Laser stabilization, Optical amplifiers, Time division multiplexing, Semiconductor lasers, Power supplies, Control systems design
In order to solve the problem that the output power and wavelength of LD (Laser Diode) were easily influenced by driving current and working temperature in TDM (time-division multiplexing)-pumped fiber Raman amplifier (FRA), a stable and highly precise LD driving system based on FPGA (field-programmable gate array) is proposed. Compared with the existing design, mainly based on integrated chips with low output current and instability defects, the circuit design in this paper simplifies the circuit structure, reduces the cost, and improves stability. A constant current source with Darlington tube and temperature control system based on the FPGA is used in the driving system, allowing for a higher output current and more excellent stability. Experimental results show that the system is capable of delivering up to 2000mA current to the LD with a precision of 0.16%. The temperature control precision reaches 0.05‡C with the current driving stability, which reaches 0.02% when the LD achieves 500mW optical power output. It is concluded that the driving system works stably and is suitable for the TDM-pumped fiber Raman amplifier.
KEYWORDS: Fiber amplifiers, Time division multiplexing, Raman spectroscopy, Signal to noise ratio, Interference (communication), Optical amplifiers, Signal processing, Optical engineering, Signal attenuation, Optical fibers
We report the transmission of signal light and the noise accumulation in the fiber Raman amplifier (FRA) under four-wavelength time-division multiplexing (TDM) pumping. A quality factor that is used to describe the performance of the Raman fiber amplifier system in quantitative analysis is proposed. The results indicate that the power variation of signal light has a certain periodicity that is related to the period of pumping with the TDM pumping. The shorter the pumping period is, the weaker the signal fluctuation is. Through the analysis of noise, it is found that amplified spontaneous emission is the main source of the noise of FRA with TDM-pumping. By comparing the TDM pump scheme with the continuous multiwavelength pump scheme, it is found that the gain of the TDM pump scheme is higher than that of the continuous multiwavelength pump scheme.
Traditional fractal coding searches the best mapping domain block in a searching pool, applying 8 symmetry operation to each domain block to satisfy the tolerance condition, thus increasing coding complexity greatly. We here present a new fast fractal image compression method based on block variance and wavelet transform which increase the coding speed up to 25 times and the reconstructed image has no obvious degradation in visual quality.
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