Photosensitive Fiber Research Articles

Direct observation of UV induced bleaching of 240 nm absorption band in photosensitive germanosilicate glass fibres

Ultraviolet loss measurements on germanosilicate fibre samples showing an intense absorption, centred at 242 nm, with an associated fluorescence at 413 nm are presented. The first direct observation is reported of the bleaching of this 240 nm band under the action of ultraviolet irradiation, evidence which is consistent with the Kramers-Kronig model for the photosensitive refractive index change in these glasses.

Spectral and spatial study of photosensitive optical fibre preforms by cathodoluminescence

The cathodoluminescence from germanium, aluminium and gallium doped optical fibre preform samples has been measured both spatially and spectrally. The results are compared with photoluminescence and ultraviolet absorption studies. It is shown that cathodoluminescent emission does not necessarily infer photosensitivity.

Ultraviolet absorption studies on photosensitive germanosilicate preforms and fibers

Detailed measurements of the ultraviolet absorption spectra of germanosilicate preforms, multimode and single-mode fibers are presented. Significant differences between the spectra of preforms and fibers are revealed and these differences are thought to be caused by the stresses induced during fiber pulling. Measurements are also presented of the changes in the absorption spectra in single-mode fibers into which reflection gratings have been written using an ultraviolet laser. These results suggest that changes in the absorption between 200 and 600 nm are not responsible for the inferred changes in the refractive index.

Spectral profile and multiplexing of Bragg gratings in photosensitive fiber

We describe a technique of optically writing several gratings in a photosensitive germanosilicate fiber. Each grating is written using the same single-frequency argon-ion laser source, but by varying the strain applied to the fiber during writing the resonant frequency of the gratings can be controlled. Frequency differences between gratings of 182 GHz have been demonstrated. The spectra of the gratings formed in the fiber were measured by periodically stretching the fiber while illuminating it with a single-frequency laser. This permits a frequency-resolved real-time analysis of the passband. The grating properties are also shown to be highly dependent on the polarization of the writing beam.

Efficient, narrowband LP 01 ↔LP 02 mode convertors fabricated in photosensitive fibre: spectral response

LP01 ↔ LP02 mode convertors have been fabricated by photoinducing index gratings within the fibre core by means of internally or externally applied light fields. The mode convertors have conversion efficiencies of over 75% and simple spectral response curves with one or two peaks. The mode conversion linewidths range from 0.2 to 10 nm.

Long wavelength cutoff of photoinduced gratings in photosensitive glass fibers

Get PDF Email Share Share with Facebook Tweet This Post on reddit Share with LinkedIn Add to CiteULike Add to Mendeley Add to BibSonomy Get Citation Copy Citation Text C. P. Kuo, Ulf Osterberg, and George I. Stegeman, "Long wavelength cutoff of photoinduced gratings in photosensitive glass fibers," Appl. Opt. 29, 4430-4431 (1990) Export Citation BibTex Endnote (RIS) HTML Plain Text Citation alert Save article

Ultraviolet light photosensitivity in Ge-doped silica fibers: wavelength dependence of the light-induced index change

A novel technique is reported for detecting permanent and transient light-induced refractive-index changes (photosensitivity) in optical fibers. The index change is detected by irradiating one arm of an unbalanced Mach-Zehnder fiber interferometer with UV light, thereby changing its optical path length. From a measurement of the change in the spectral response of the Mach-Zehnder interferometer, the change in the fiber core index as a function of wavelength can be determined. The equilibrium change in the core index is found to have an almost constant value of approximately 2.3 x 10(-5) over the measured wavelength range of 700 to 1400 nm.

Growth dynamics of photosensitive gratings in optical fibers

We study the growth dynamics of photosensitive fiber gratings assuming a local bleaching model, and demonstrate that sustained grating growth is possible. Good agreement with our experimental results is obtained after including fiber heating effects.

A non-linear high temperature fracture mechanics basis for strain range partitioning. (Report): Kitamura, T. and Halford, G. R.NASA Tech. Memo. NASA TM-4133 1989, 14 pp

In this paper, a strain insensitive high temperature fiber sensor based on the modal interferometer is proposed. It is composed of a piece of small-core photosensitive fiber (SCPSF) which is spliced between two pieces of single mode fiber (SMF). Compared to other high temperature fiber sensor based on the modal interferometer, the sensor owns the highest temperature sensitivity of 106.64 pm/°C from 200 °C to 1000 °C. The temperature to strain cross sensitivity of the sensor is low and only 0.00675 °C/με. The reasons for realizing the high temperature sensitivity is also discussed.

Photosensitive optical fibers used as vibration sensors

We experimentally demonstrate that high-reflectivity photosensitive gratings written in optical fibers can be used to detect vibrations that produce length changes of less than 50 nm. This sensitivity to external perturbations can also explain the high-frequency components often observed during the growth of these gratings.

Rocking filter formation in photosensitive high birefringence optical fibres

Parent et al. observed that the refractive index changes induced in optical fibres by Hill grating formation (at 488 and 514.5 nm) were birefringent. A wavelength filter, formed in a simple and novel way by exposing high birefringence fibre to linearly polarised 488 nm light, is reported. Narrow bandwidth operation and high conversion efficiencies are achieved experimentally between the two orthogonal polarisation states of the fibre.

Photosensitivity in optical fiber waveguides: Application to reflection filter fabrication

The observation of photosensitivity in Ge-doped core optical fibers is reported. The photosensitivity is manifested by light-induced refractive-index changes in the core of the waveguide. Narrowband reflectors in a guide structure have been fabricated using this photosensitivity and the resulting DFB reflectors employed as laser mirrors in a cw gas laser in the visible.