Optical Fiber Transfer Delay Measurement Based on Phase-Derived Ranging

Abstract

High-accuracy optical fiber transfer delay (OFTD) measurement with a broad measurement range is essential for the development of high-speed or parallel optical devices and systems. In this letter, we propose a system for OFTD measurement using the phase-derived ranging. A microwave signal is converted into an optical signal, which is transmitted through a fiber under test. After photodetection, the OFTD is converted into the phase shift of the microwave signal, which can be detected using a microwave phase detector. When calculating the OFTD, the phase error is divided by the highest microwave frequency, which ensures the high measurement accuracy. The integer ambiguity caused by the phase detection can be removed by sweeping the microwave frequency in a range of 1 MHz. An experiment is performed. The measurement of a motorized variable optical delay line and a long fiber shows that a dynamic range of more than 20 km and an accuracy of ±0.1 ps can be achieved with no dead zone.