Photonic multiple frequency measurement using a frequency shifting recirculating delay line structure

A new photonic frequency measurement structure that can realise multiple-frequency measurement, while simultaneously achieving a high resolution and a wide measurement range is presented. It is based on successively frequency shifting the modulation sideband of an optical signal until it falls close to the reference carrier frequency, and then combining it with an unshifted carrier and detecting it through a narrowband filter. Experimental results demonstrate a multiple-frequency detection capability over a range of 0.1-20 GHz, which can readily be extended to 100 GHz, together with a high measurement resolution of 250 MHz and small measurement error.