Two mode-locked Ti:sapphire lasers were synchronized with different kinds of phase-locked loops. Conventional phase-locked loop (EPLL) systems employ an electrical device known as a double balanced mixer for phase comparison. However, a novel phase-locked loop in our system employs an optical up-converted signal (OPLL). When two lasers were synchronized with the EPLL, the up-converted signal of two lasers was measured and the relative timing jitter for 1 ms was estimated to be longer than 430 fs. When two lasers were synchronized with the OPLL, the cross-correlation of two lasers could be measured for the small relative timing jitter. The timing jitter of two lasers for 1.8 s was 28 fs. The holding time of the OPLL was 60 minutes.