{"title":"Mode coupling at an imperfect Fresnel surface in a fluorine-trench dual-mode fiber","authors":"Xiaolu Cao , Mingming Luo , Jianfei Liu , Jie Ma","doi":"10.1016/j.yofte.2024.104027","DOIUrl":null,"url":null,"abstract":"<div><div>Mode coupling, often overlooked at an imperfect Fresnel surface, is now examined in a fluorine-trench dual-mode fiber to avoid energy losses and signal degradation. For invisible defects on the reflecting surface, the orthogonal forward LP<sub>01</sub> (LP<sub>11</sub>) mode with group velocity <em>v</em><sub>g</sub><sup>LP<sub>01</sub></sup> (<em>v</em><sub>g</sub><sup>LP<sub>11</sub></sup>) partially converts to the backward LP<sub>11</sub> (LP<sub>01</sub>) mode with <em>v</em><sub>g</sub><sup>LP<sub>11</sub></sup> (<em>v</em><sub>g</sub><sup>LP<sub>01</sub></sup>) through a transfer matrix, respectively. Consequently, this interaction generates a unique hybrid backward mode, which results in an average round-trip time delay and the mean of the velocities, (<em>v</em><sub>g</sub><sup>LP<sub>01</sub></sup> + <em>v</em><sub>g</sub><sup>LP<sub>11</sub></sup>)/2. Upon harvesting and analyzing the backward reflections using a high-resolution coherent optical frequency domain reflectometry, a Fresnel reflection peak corresponding to the hybrid mode is observed with a high signal-to-noise ratio precisely between the LP<sub>01</sub> and LP<sub>11</sub> peaks. Additionally, the frequency difference between the hybrid and LP<sub>01</sub> (or LP<sub>11</sub>) modes is calculated to be 20.625 Hz exactly half of the 41.250 Hz difference between the LP<sub>01</sub> and LP<sub>11</sub> modes. Further testing on five additional fiber segments ranging from 8.812 m to 10.812 m corroborates this theory, as their <em>v</em><sub>g</sub><sup>hybrid</sup> values align closely with (<em>v</em><sub>g</sub><sup>LP<sub>01</sub></sup> + <em>v</em><sub>g</sub><sup>LP<sub>11</sub></sup>)/2. Our analytical insights detail the dynamic mode coupling at an imperfect Fresnel surface, promising a flexible method for dynamic mode observation and regulation for mode division multiplexing optical fiber communications, particularly in enhancing the detection and mitigation of defects at fiber lasing end faces.</div></div>","PeriodicalId":19663,"journal":{"name":"Optical Fiber Technology","volume":null,"pages":null},"PeriodicalIF":2.6000,"publicationDate":"2024-11-04","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":"0","resultStr":null,"platform":"Semanticscholar","paperid":null,"PeriodicalName":"Optical Fiber Technology","FirstCategoryId":"94","ListUrlMain":"https://www.sciencedirect.com/science/article/pii/S1068520024003729","RegionNum":3,"RegionCategory":"计算机科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":null,"EPubDate":"","PubModel":"","JCR":"Q2","JCRName":"ENGINEERING, ELECTRICAL & ELECTRONIC","Score":null,"Total":0}
引用次数: 0
Abstract
Mode coupling, often overlooked at an imperfect Fresnel surface, is now examined in a fluorine-trench dual-mode fiber to avoid energy losses and signal degradation. For invisible defects on the reflecting surface, the orthogonal forward LP01 (LP11) mode with group velocity vgLP01 (vgLP11) partially converts to the backward LP11 (LP01) mode with vgLP11 (vgLP01) through a transfer matrix, respectively. Consequently, this interaction generates a unique hybrid backward mode, which results in an average round-trip time delay and the mean of the velocities, (vgLP01 + vgLP11)/2. Upon harvesting and analyzing the backward reflections using a high-resolution coherent optical frequency domain reflectometry, a Fresnel reflection peak corresponding to the hybrid mode is observed with a high signal-to-noise ratio precisely between the LP01 and LP11 peaks. Additionally, the frequency difference between the hybrid and LP01 (or LP11) modes is calculated to be 20.625 Hz exactly half of the 41.250 Hz difference between the LP01 and LP11 modes. Further testing on five additional fiber segments ranging from 8.812 m to 10.812 m corroborates this theory, as their vghybrid values align closely with (vgLP01 + vgLP11)/2. Our analytical insights detail the dynamic mode coupling at an imperfect Fresnel surface, promising a flexible method for dynamic mode observation and regulation for mode division multiplexing optical fiber communications, particularly in enhancing the detection and mitigation of defects at fiber lasing end faces.
期刊介绍:
Innovations in optical fiber technology are revolutionizing world communications. Newly developed fiber amplifiers allow for direct transmission of high-speed signals over transcontinental distances without the need for electronic regeneration. Optical fibers find new applications in data processing. The impact of fiber materials, devices, and systems on communications in the coming decades will create an abundance of primary literature and the need for up-to-date reviews.
Optical Fiber Technology: Materials, Devices, and Systems is a new cutting-edge journal designed to fill a need in this rapidly evolving field for speedy publication of regular length papers. Both theoretical and experimental papers on fiber materials, devices, and system performance evaluation and measurements are eligible, with emphasis on practical applications.