Two-way optical time transfer using a photonic chip

A method, comprising:

• receiving, at a photonic chip, a first pulse train from an external source, wherein the external source comprises a remote clock, wherein pulses in the first pulse train have a first repetition rate;
• receiving, at the photonic chip, a second pulse train having pulses with a second repetition rate different from the first repetition rate;
• optically combining the first pulse train and the second pulse train into a combined optical signal in the photonic chip;
• and
• outputting the combined optical signal onto a photodetector to generate interference measurements between pulses in the first and second pulse trains for synchronizing a local clock to the remote clock.

A clock system, comprising:

• a first clock;
• a pulsed optical source configured to generate a first pulse train with pulses having a first repetition rate;
• and
• a photonic chip optically coupled to the pulsed optical source, wherein the photonic chip is configured to receive and combine the first pulse train with a second pulse train received from an external clock system in order to synchronize the first clock with a second clock in the external clock system, wherein the second pulse train has pulses with a second repetition rate different from the first repetition rate.