Shaping Spectra within Optical Fibers

Abstract

A unique fiber‐integrated diffraction grating enables a new kind of ultra miniature high‐resolution spectrometer. Within, all components for optical imaging are encoded directly leading to an outstanding ratio of optical resolution to build size. The entire design comprises only two aligned parts and allows a cost‐effective, customizable production, and robust spectrometers. As an exemplary application we present a compact interrogation system for fiber Bragg grating sensors.

Non-destructive technique for characterization fiber Bragg gratings via diffraction profile

“…We called them positive 𝑚 = 1 and negative 𝑚 = −1 parts of the diffraction order. This phenomenon links to the elongated ellipsoid form of individual grating points, as described in references 32,22,33,[5][6][7]34 . Both maxima are oriented perpendicularly to the long axis of the ellipsoidal.…”

“…Figure 7 shows the laser power used to produce five different gratings as a function of their resulting outcoupling efficiency. The efficiency was calculated according to (5) and showed direct dependence on the laser power. Measuring the outcoupling efficiency gets information about the RIM characteristics of each produced FBG and thus can help control their reproducible production.…”

“…In all these applications, the typical optical responses of the fiber Bragg grating are a reflection and transmission spectrum. However, with the growing diversity in applications of fiber Bragg grating in certain sensing [2][3][4] and spectrometric fields, [5][6][7][8][9] there is an increasing need for and importance of practical techniques involved in the manufacturing process providing the spatial information of the grating.…”

4.3 Fiber Optic Sensing: the challenges of miniaturization, ruggedization and integration to enhance flight test instrumentation capabilities

“…In [7] and [8] FiSens first presented a fiberintegrated spectrometer which overcomes these limitations.…”

Ultracompact Lens‐Less “Spectrometer in Fiber” Based on Chirped Filament‐Array Gratings

“…Alternative geometric forms of refractive index modification are a promising direction for tuning and optimizing the radiative modes of an all‐fiber spectrometer. Waltermann et al [ 19 ] used a femtosecond laser to form ellipsoidal refractive index structures and demonstrate a chirped fiber spectrometer, offering spectral focusing and a short wavelength extension to 810 nm. Higher‐resolution and more efficient gratings are thus required to enable all‐fiber spectrometers with more compact design, less polarization sensitivity, and broader spectral coverage.…”