Optical fiber with distributed Bragg-type reflector

Enhanced Optical Fiber for Distributed Acoustic Sensing beyond the Limits of Rayleigh Backscattering

“…It is well known that exposure of optical fiber to pulsed radiation may increase elastic scattering well above the native Rayleigh scattering, particularly through the formation of periodic or quasi-periodic fiber Bragg gratings. While typical Bragg gratings are less than 10 cm in length, such processing may be applied over long fiber lengths and has been demonstrated in several fabrication systems using single core fibers, including direct write or point-by-point writing with UV (Asseh et al, 1997;Monet et al, 2019) and IR femtosecond lasers (Lu et al, 2019), reel-to-reel setups (Lefebvre et al, 2006), drum systems (Brennan et al, 2003), draw tower grating fabrication (Askins et al, 1994;Bai et al, 2015;Zaitsev et al, 2016;Guo et al, 2013), as well as direct UV exposure (Westbrook, 2016;Loranger et al, 2015). We have reported on an alternative and flexible method to achieve nearly continuous backscattering over many meters in fibers with any number of cores using reel-to-reel fiber handling and a UV transparent coating (Atkins et al, 2002;Westbrook et al, 2014Westbrook et al, , 2015Westbrook et al, , 2017aWestbrook et al, , 2017b.…”

The Sensitivity Improvement Characterization of Distributed Strain Sensors Due to Weak Fiber Bragg Gratings

“…A sensor based on a fiber with periodically applied WFBG can be used to obtain a higher-intensity signal from the sensor. The technology allows creating such structures directly during the extraction of fiber, which makes it convenient and inexpensive [ 28 , 30 ]. The reflection coefficient of such WFBGs can be fractions of a percent or less, while their relative amplitude spread in the array will be no more than 15% [ 55 ].…”

“…A significant step toward explicitly representing the relationship between external influences and signal changes would be to modify sensors with WFBGs. Patents for such a sensor device first appeared a long time ago [ 27 ], but they have only received practical implementation relatively recently [ 28 , 29 , 30 ]. Before this point, gratings at different wavelengths were mainly surveyed, or wavelength shifts were monitored [ 31 , 32 ].…”

Искусственные Рэлеевские Волокна И Их Применение В Лазерах

“…Это приводит к тому, что резонаторы случайных лазеров строятся с использованием длинных (1-100 км) ОВ. Современные тенденции случайных волоконных лазеров связаны с переходом к лазерам с резонатором [4] на основе коротких искусственных рэлеевских оптических волокон (ОВ, содержащих массив волоконных брэгговских решёток -ВБР) [5].…”

“…Нами разработано ОВ с ВБР, запись которых производится во время процесса вытяжки ОВ [5]. Формирование массива ВБР в таком ОВ выполняется с помощью импульсного излучения эксимерного УФ-лазера, проходящего через фазовую маску.…”