A novel optical phase-locked loop (OPLL) based on four-wave-mixing in optical fibers and optical voltage-controlled oscillator (OVCO) is proposed and built to perform clock recovery in optical time-division multiplexed systems. The operation principle of the optical phase-locked loop and the configurations and functions of modules in optical phase-locked loop are analyzed theoretically. With the use of highly-nonlinear fibers in all-optical phase detector, the fiber length is shortened sufficiently, which reduces the walk-off between two pulse trains induced by dispersion. The phase detector has an extinction ratio beyond 30 dB. The optical voltage-controlled oscillator based on regenerative mode-locked fiber laser provides high-quality pulses over a repetition frequency range of 380 kHz. In the clock recovery experiment, a transform-limited pulse train is recovered from a 40 Gb/s signal, with pulse width of 7.2 ps, timing jitter (root-mean-square) of 152 fs, and super-mode suppression ratio over 60 dB. The loop is robust against pattern effect and amplitude fluctuation of input signal.