Design and implementation of a constant current driving circuit for high stability fiber optic device

The stability of the wavelength and output power of the fiber laser is susceptible to fluctuations in the pump drive current, and a high-precision, high-stability constant-current drive system has been designed to cope with this problem. The constant current source part adopts the closed-loop negative feedback principle to control the consistent current output through the Metal-Oxide-Semiconductor Field-Effect Transistor (MOSFET), realizing the precise control of the semiconductor laser (LD) drive current. The current-limiting protection circuit protects the LD from overcurrent shocks by utilizing the diode's limiting effect, and the current slow start uses a software-controlled method to protect LD from inrush current damage. The ADA4530 chip is used in the optical power detection circuit to ensure accurate detection of power output even at deficient light levels. The experimental results show that the circuit can achieve continuous adjustment of the drive current from 0 A to 1.2 A, with short-term (120 min) and long-term (24 h) current stability of 0.001 mA and 0.002 mA, respectively. The wavelength fluctuation of the laser center does not exceed 0.03 nm, and the stability of the output power does not exceed 0.084 3%, with an accuracy of less than ±0.15 mW.