Dual- and quad-FSF laser optical frequency comb application for time delay variation associated measurements

The frequency-shifted feedback (FSF) laser is an optoelectronic system with an optical feedback loop with a characteristic feature that consists of a broadband optical emission spectrum that does not contain modes. Nevertheless, this system may operate in the so-called mode-locking regime, when the output optical signal is a sequence of short optical pulses with a repetition rate determined by the delay time in the feedback loop. In the frequency domain such a sequence forms the optical frequency comb with line spacing defined by time delay magnitude. It was shown recently that the sequential frequency down-conversion technique allows us to obtain tunable dual- and quad-combs when the FSF laser is seeded only with optical amplifier spontaneous emission. We propose to apply these combs to fulfill measurements associated with time delay variation, such as distance ranging and optical material refraction coefficient measurements.