Intensity profile in a distributed feedback fibre laser characterised by a green fluorescence scanning technique

We report on an experimental technique for investigating the intensity profile in distributed feedback fibre lasers. By scanning along the laser length and monitoring the side green fluorescence, the intensity distribution in the laser can be inferred. With this approach, we experimentally verify the sharply peaked intensity distribution predicted for lambda/4 phase-shifted distributed feedback lasers

High power (60mW) single frequency erbium:ytterbium codoped fiber laser

The characteristics of a high power Er3+:Yb3+ single frequency fiber laser pumped at 980nm are reported. The device gives 60mW output power with RIN 10MHz and linewidth 500kHz. At low output powers (< 30mW) the slope efficiency is as high as 25%, falling to 12% at higher powers, the saturation behaviour is related to a bottleneck effect due to the finite Yb-Er transfer rate. Improved performance can be obtained using new fibers with an increased rare-earth concentration which show negligible signs of erbium clustering

Association of newly synthesized pro-opiomelanocortin with secretory granule membranes in pituitary pars intermedia cells

AbstractThe prohormone, pro-opiomelanocortin (POMC) is synthesized on ribosomes, subsequently routed to the Golgi apparatus and finally packaged into secretory granules where it is processed to various biologically active hormones (α-melanotropin, adrenocorticotropin, β-endorphin and β-lipotropin). We report here that in frog and mouse pars intermedia cells, newly synthesized[3H]Arg-labeled POMC is associated with the secretory granule membrane prior to processing. This association with the secretory granule membrane may be related to the intracellular transport and packaging of POMC and/or the facilitation of processing of the prohormone within the organelle

Efficient single frequency fibre lasers using novel photosensitive Er/Yb optical fibres

Boron- and germanium-doped highly photosensitive cladding is used in a novel design to achieve photosensitive Er/Yb-doped fibers, permitting short, strong gratings (length ~1cm, reflectivity >99%) to be written without hydrogenation. The high absorption at 980nm in Er/Yb fibers permits efficient pump absorption over a short device length, which is ideal for achieving highly efficient single-frequency fiber lasers. Both single-frequency Bragg-grating reflector and distributed-feedback lasers with slope efficiencies of 25% with respect to launched pump power have been realized in such fibers

Suppression of self-pulsing behaviour in erbium-doped fiber lasers with resonant pumping

A new approach to improving the stability of erbium-doped fiber lasers is presented. Using a model based on ion pair effects, spiking behaviour is shown to be effectively suppressed by resonant pumping, when the pump wavelength is sufficiently close to the lasing wavelength

Birefringence upper limit analysis of low birefringence fibers employed in the Faraday effect current sensors

The theoretical model of the Faraday rotation in the low birefringence optical fiber is proposed to serve as a convenient tool for the determination of the birefringence upper limit allowed to retain current sensor sensitivity. The measurement technique offers a fast and efficient determination of the ultra-low linear birefringence when other techniques are not sensitive enough or they are difficult to implement. A temperature dependence of the Faraday rotation and its causes are investigated

10Gbit/s transmission over 700km of standard single mode fibre with a 10cm chirped fibre grating compensator and duobinary transmitter

The advent of erbium-doped fibre amplifiers makes optical fibre transmission in the 1.55µm wavelength window very attractive. However, with the large amounts of standard non-dispersion shifted fibres (NDSF) already installed, high bit rate transmission is restricted by the large dispersion of these fibres at 1.55µm, unless compensating techniques are used. A number of approaches have been put forward to address this issue, such as dispersion compensating fibre, mid-point spectral inversion, dispersion-supported transmission, solitons, and chirped fibre Bragg gratings. Of these, fibre gratings are attractive as they are passive, linear devices, highly dispersive yet compact and relatively easy to fabricate in large numbers. In recent years, progress in the use of fibre grating-based compensation for 10 Gbit/s transmission has been rapid, with distances reported from 160km, 220km, 270km, 400km and most recently to 540 km. In this work, we demonstrate that 10 Gbit/s transmission up to 700 km of NDSF is achievable with a single 10 cm long chirped fibre grating in combination with a reduced bandwidth phase-alternating duobinary transmitter

Soliton interaction in the presence of a weak non-soliton component

We study both experimentally and theoretically soliton interaction in the presence of a weak non-soliton component and show that the existence of a frequency shifted cw wave results in a temporal shift of the soliton

A single-mode, high index-contrast, lead silicate glass fibre with high nonlinearity, broadband near-zero dispersion at telecommunication wavelengths

We report on the design, fabrication and characterization of a single-mode W-type lead silicate glass fibre with flattened and near-zero dispersion profile at telecom wavelengths and high nonlinearity of 820 W-1km-1 at 1.55 µm

Self-starting, passively mode-locked Fabry-Perot fibre soliton laser using non-linear polarisation evolution

We demonstrate pure self-starting mode-locked operation in a fibre Fabry-Perot cavity. The laser produces 1.6ps transform-limited soliton pulses by means of non-linear polarisation evolution in conjunction with an intracvity fibre polariser