Effect Of Electric Field Coupling On SLD Light Source Module

Superluminescent diode(SLD)has become a common light source for fiber optic gyroscope(FOG)because of its high output power,good coherence,wide emission spectrum,small size and light weight.The stability of output optical power and wavelength directly determines the performance of FOG.When the semiconductor cooler(TEC)is driven by a switching power amplifier,the AC interference will be coupled to the constant current loop,which will affect the stability of the output optical power.However,there are few studies on this issue at present.In this paper,the electric field coupling in SLD light source module is analyzed,modeled and validated.Firstly,according to the internal structure and driving mode of SLD light source module,the existence of distributed capacitance and capacitive coupling between conductor groups in the module is analyzed,which indicates that the electric field coupling has a certain influence on the output optical power.Secondly,the electric field coupling in SLD is simulated.The distributed capacitance matrix and equivalent circuit diagram of the conductor group of SLD light source module are obtained by simulation calculation.It is proved theoretically that there exists electric field coupling in SLD.The finite element model of electric field coupling in SLD light source module is established,and the distributed capacitance between TEC refrigeration sheet and SLD tube core conductor is simulated.The results show that there exists distributed capacitance between tube core conductor and TEC refrigeration sheet.When AC interference occurs on TEC refrigeration sheet controlled by switched power amplifier,the interference signal will pass through sub-section.Cloth capacitance is coupled to the SLD core conductor,which interferes with the constant current loop and thus affects the stability of the output optical power.Thirdly,the electric field coupling in SLD is studied experimentally.The effect of electric field coupling on SLD is proved by experiments.Distributed capacitance between conductor banks is measured,and the existence of coupling circuit between SLD core and TEC chiller is verified by design experiment.The experimental results show that there is electric field coupling between SLD core and TEC chiller.Fourthly,the method of restraining the coupling effect of electric field is proposed.The capacitive coupling can be effectively restrained by reducing the distributed capacitance between conductor groups and the interference voltage on TEC chiller.The driving mode of TEC chiller by grounding at one end of TEC chiller or improving the temperature control circuit of SLD light source(from differential output to unilateral output)can be effectively restrained.The theoretical and experimental results show that the electric field coupling in SLD light source module has an effect on the output optical power stability,which has a certain reference value for the research of output optical power stability and the design of driving circuit.