Light-controlled Reconfigurable Fiber Bragg Gratings Written in Attenuation Fiber

Abstract

A novel type of light controlled fiber Bragg gratings written in attenuation fiber is demonstrated. The spectral reconfiguration can be controlled by the pump power, the pumping configuration, the grating position and the fiber attenuation. IntroductionTunable, reconfigurable and actively controlled fiber Bragg gratings (FBG) are one of the key components for the agile optical networks and sensing systems. Most common tuning methods include piezo-electrical [1], mechanical [2] and, thermal actuation [3,4]. Thermal tuning is usually achieved using a thin metallic film, deposited on the fiber around the FBG and heated using externally supplied electrical power. Electrical heating requires deposition of a metallic coating, external electrical power supply and cabling, which altogether limits range of application, decreases device lifetime, and could prevent application in harsh environment. Ideally, spectral shaping and reconfiguration of the properties of optical gratings should be done via optical means. The idea of all-optical control was demonstrated using Er/Yb doped fiber and appropriate pump light. Index changes were induced based on nonlinear effect [5] or non-radiative absorption [6]. Recently, Chen et al. [7] demonstrated an optically tunable FBG where the grating is heated by pump light absorbed in the metallic coating. In addition to applications in telecommunications, actively optically controlled FBG could play an important role in the sensing area [8]. Here, we present a novel all-optically reconfigurable optical fiber grating, without mechanical and electrical components. The idea is based on the concept of writing an FBG in an attenuation fiber. We called this new family of Bragg gratings -attenuation fiber Bragg gratings (AFBG). Using the high power light source (at a wavelength outside the grating resonance), the FBG written inside the attenuation fiber is heated and actively controlled using optical means only. Non-uniform absorption of the pump power along the fiber induces nonuniform temperature distribution. Using optical low-coherence reflectometry we measure the temperature profile along the grating with high spatial distribution. Due to the simple design and heating of the grating with light propagating along the same fiber, this device offers a simple solution for remotely light-controlled FBGs.

Reflective Optical Fiber Refractometer Based on Long-Period Grating Tailored Active Bragg Grating

“…The core of the COF is doped with photoabsorption medium cobalt. Therefore, the COF can nonradiatively absorb the pump laser propagating in its core and transfer the laser power into heat [21]- [23], which induces the temperature increase of the COF, as well as of the AFBG region. The resonant wavelength of the LPG is appropriately designed to overlap the wavelength of the pump laser.…”

Distributed flow sensing using optical hot -wire grid

“…To overcome these problems, we proposed replacing electrical heating with optical on-fiber heating using single-mode high attenuation fiber (HAF). The idea of heating a piece of single-mode fiber internally via the absorption of optical power in HAF was first proposed by Coric et al [17,18], and was employed for a variety of fiber sensing applications including room and cryogenic temperature liquid level sensors [17,[19][20][21], cryogenic hydrogen gas sensors [19,22], and gas flow sensors [8]. As illustrated in Fig.…”

Self-heated fiber Bragg grating sensors for cryogenic environments

“…The core of the HAF is heavily doped with Cobalt and Germanium to allow photon scattering and energy loss to quantified amount during the single mode light propagation. It has been reported that active thermal tuning of FBG was realized with FBGs inscribed into HAF 18 . Figure 2b depicts the design of in-fiber heating sensor using HAFs.…”