When contact resistance of power cable transition joint is too large

temperature of power cable joint will increase

and even cause accidents such as thermal breakdown and cable fires

which affect normal operation of the cable seriously.A fiber Bragg grating（FBG） temperature sensor with circular copper is developed

which is installed inside power cable joint to monitor temperature increasing.Test results show that the sensitivity of sensor is 18.37 pm/℃

the nonlinearity error is 1.35 %FS and the repeatability is 4.5 %FS.A power cable joint is made with two cable cores

in which one is connected by resistance wire;the other is connected by aluminum core connection tube.When 75

100V and 125V voltage are separately exerted within 120 min

the experiments show that the maximum temperature increase of resistance wire cable core joint is 4.95 ℃ higher than that of aluminum core cable joint.