High Accuracy Optical Reflectometry and Its Applications in Measurement of Multiple-Path Interference in Optical Fiber Communication Systems

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With the object of providing efficient solutions to the difficult problems in optical fiber communication industry, such as the diagnoses of optical fiber modules like erbium-doped optical amplifiers (EDFA), the measurement of multi-path interference in optical fiber modules, etc., this project is aiming at enhancing the accuracy (reflection resolution) of optical reflectometry, i.e., optical reflection distribution measurement, by merging the technique of "synthesis of optical coherence function" (SOCF), which is originally created by this research group, with the scheme of "wavelength sweeping averaging" developed by the head investigator before.Performance limiting factors, especially the interference among the Rayleigh scatterings and multiple reflections in optical fiber modules, are investigated thoroughly by analysis and numerical simulation, which confirm the effectiveness of employing wavelength sweeping averaging in SOCF in suppressing the interference-induced fluctuations in … More measured reflection distribution. A new scheme with dual optical frequency modulation is proposed, in which a high-fequency sinusoidal wave for synthesizing a coherence peak for distributed reflection measurement and a relatively slow sweeping for wavelength sweeping averaging are applied simultaneously. With this newly invented scheme, a reflection distributed with high accuracy can be obtained optically in short-time, which costs in general thousand of seconds with conventional techniques. In experiment demonstration, a reflection distribution with 0.02-dB accuracy for 50-m optical fiber is obtained within 50 seconds. Moreover, a novel homodyne detection scheme with adaptive carrier is also invented, which enhances the dynamic range of the system in great extent.With this high-accuracy high speed optical reflectometric system, the measurements for the reflection distribution and the multi-path interference in optical fiber modules are demonstrated successfully in experiment. In addition, the application of this high-performance functional optical reflectometry technology in the diagnosis of fiber access network with multiple optical paths is also investigated. The newly proposed and demonstrated techniques also contribute to the development of distributed and multiplexed fiber optic sensors. Less