In this letter, we describe a self-starting optical pulse source generating ultra low noise 15-ps-wide pulses at 10 GHz. It is based on a hybrid optoelectronic oscillator comprising a fiber extended cavity mode-locked diode laser which injection locks a self-oscillating heterojunction bipolar phototransistor. Average jitter levels of 40-43 fs and an amplitude noise of 0.1-0.15% over a frequency range of 500 Hz-15 kHz or 500 Hz-1 MHz were obtained, respectively. The noise is slightly larger, a 57- fs jitter and 0.2% amplitude noise, for a frequency range of 100 Hz-1 MHz. A 10-GHz electrical signal with a low phase noise (-108 dBc/Hz at 10-kHz offset from the carrier) is also generated.