Optical frequency comb application in time-delay interferometer

Time-delay interferometer (TDI) is well established as an effective technique to mitigate laser phase noises in laser interferometer gravitational wave detection. Just as important in the TDI scheme is the ability to suppress the rf local oscillator noises in the optical heterodyne measurements. We show that the local oscillator noises can be effectively and elegantly cancelled by employing optical frequency combs in which the rf signal phases are coherent with the optical phases. In addition, the deployment of optical combs eliminates the need for separate ultra-stable oscillators. This is a simpler and more reliable approach than the modulation scheme, and it can be applied to the most generalized TDI combinations.