Narrow-linewidth fibre laser with integral fibre grating

The fabrication and operation of an Nd3+-doped silica single-mode fibre laser using a distributed fibre grating as the feedback element is reported. The laser had a threshold of less than 2mW, a slope efficiency of 19% and an output bandwidth at the lasing wavelength of 1.084?m of 16 GHz, significantly narrower than the conventional cavity design.     

High-power cascaded Raman fibre laser using phosphosilicate fibre

A 13.2 W second cascade phosphosilicate cascaded Raman fibre using a 450 m phosphosilicate singlemode optical fibre is demonstrated. The lasing wavelength is 1539 nm and the conversion efficiency is 32.5%. This is the highest output power ever reported from a cascaded Raman fibre laser in the 1400-1600 nm range.     

Simplified laser to fibre coupling via optical fibre up-tapers

A new method for coupling single-mode fibre to laser diodes employing a spherical ruby lens and a single-mode optical fibre up-taper is demonstrated. High coupling efficiency and greatly reduced alignment sensitivities are attained     

Wavelength-switching fibre laser based on multimode fibre Bragg gratings

A multimode fibre Bragg grating (MMFBG) based wavelength-switching erbium-doped fibre laser is reported. With a simple singlemode fibre to MMFBG structure, a novel wavelength-selection technique is developed to achieve the wavelength-switching by changing the mode coupling condition in the multimode fibre. 31 discrete lasing wavelengths are obtained over a wide wavelength range.     

Brillouin fibre laser with 20 m-long photonic crystal fibre

Brillouin fibre laser is demonstrated using a very short length of photonic crystal fibre (PCF). A simple ring resonator is used in the experiment which consists of a 20 m long highly nonlinear PCF and 49 cm long Bismuth-based erbium-doped fibre (Bi-EDF). The proposed Brillouin laser is able to generate up to 3 Stokes and 3 anti- Stokes lines in the 1560 nm region at a channel spacing of 0.09 nm.     

Multiwavelength erbium-doped fibre laser based on ahigh-birefringence fibre loop mirror

A novel multiwavelength fibre laser is proposed, which is based on a fibre loop mirror formed by a high-birefringence (HiBi) fibre, a polarisation controller, and a directional coupler. By setting the polarisation controller properly, the HiBi fibre loop mirror acts as a polarisation-independent wavelength filter. With this configuration, the wavelength spacing of the laser can be varied accurately by adjusting the length of the HiBi fibre. Experimentally, by cooling the erbium-doped fibre with liquid nitrogen to reduce its homogeneous linewidth, stable emission at 16 wavelengths with a spacing of 0.8 nm and an amplitude variation of <5 dB was achieved     

Photonic crystal fibre for use in fibre Raman amplifiers

A novel photonic crystal fibre is proposed and designed. For this fibre, the variation of its effective core area Aeff via wavelength can be designed to follow the track of its Raman gain coefficient gR, so that a flat Raman gain efficiency rR=gR/Aeff is resulted. A fluctuation of less than 5.5% is obtained for rR between 1565 and 1625 nm (L-band).     

Characterisation of a fibre Raman oscillator using fibre grating reflectors

We have constructed a completely integrated fibre Raman oscillator using two fibre grating reflectors. This was synchronously mode-locked using a CW mode-locked Nd:YAG laser operating at 1.06?m. Spectral and temporal characteristics of the Raman oscillator are presented.     

Single-mode fibre connectors

A low-loss detachable connector has been fabricated for single-mode optical fibres. It consists of a pair of plugs accommodating fibres to be joined and a sleeve provided with ball-bearing arrays to align the plugs. The average connecting loss is reduced to as low as 0.5 dB, including fibre end reflection.     

Silicone-clad fused-silica-core fibre

We have developed a very-low-loss optical fibre employing silicone resin as the cladding and fused silica as the core. The minimum transmission loss was 3.2 dB/km at 0.84 ?m and the half-pulse width spread was 19 ns/km at 0.80 ?m.     

Dual-wavelength fibre laser

A new external laser cavity design that allows for wavelength tuning and controlled simultaneous two-mode oscillation is demonstrated for a fibre laser. The gain bandwidth and the position of the gain maximum are determined from the tunability and the minimum threshold, respectively. Two-mode oscillation is shown for different mode wavelength spacings     

Baseband-frequency-response measurement of graded-index fibre using step-index fibre as an exciter

For measuring reproducibily the baseband frequency response of a graded-index fibre, a mode exciter utilising an ordinary step-index multimode fibre has been proposed. The input mode power distribution and the frequency response of the fibre with the exciter are altered very little for axis offset. Input mode distribution excited indicates that excitation of nearly all modes takes place.     

Wideband gain flattened erbium fibre amplifier using a photosensitive fibre blazed grating

An erbium fibre amplifier with a highly flattened gain spectrum is demonstrated for the first time using an all fibre photosensitive Bragg grating. An ASE spectrum flattened to within +or-0.5 dB over a bandwidth of 35 nm in the 1550 nm window is achieved with a 3 mm long radiation coupling Bragg fibre grating.<>     

Broadband diode-pumped fibre laser

Reports the observation of a strong dependence of the emission spectrum (centre wavelength and linewidth) of Nd:silica fibre lasers on pump wavelength. In a particular fibre, careful selection of the pump wavelength has led to the operation of a broadband fibre laser at 1060 nm with 19 nm FWHM bandwidth. When pumped with a 30 mW diode laser, it exhibits a 1 mW threshold, a 2.5 mW output, and an intrinsic average wavelength temperature stability of about 10 p.p.m./°C     

Monomode fibre polarisation scrambler

A technique for the pseudodepolarisation of a long-coherence-length source is described, which is based on a simple polarisation modulation scheme. Using a length of high-birefringence fibre wound on to a piezoelectric transducer, a simple all-fibre polarisation scrambler can be constructed.     

Single-mode fibre pressure sensitivity

The pressure-induced retardation in a sample of single-mode fibre cable has been measured. The pressure sensitivity of the uncoated fibre was found to agree with the theoretically expected value. Application of a silicone rubber coating reduced the sensitivity by over 50%. No pressure sensitivity was measured when a loose-fitting tube was extruded around the coated fibre.     

Neodymium-doped fluoro-zirconate fibre laser

We report for the first time lasing in a multimoded neodymium-doped fluoro-zirconate fibre. Close to threshold we observe a single line of less than 1 a?ngstrom width. The threshold is high and efficiency is low, but we believe that significant improvements will be achieved with single-mode geometry.     

High-speed fibre Bragg grating sensor interrogation using dispersion compensation fibre

A novel high-speed fibre Bragg grating (FBG) sensor interrogator using dispersion-compensating fibre is proposed and demonstrated. The wavelength shift measurement of the FBG sensor is converted to time-domain measurement. The high-speed potential of this scheme was investigated experimentally, demonstrating an effective sampling speed of 2.44 megasamples per second.     

Dual wavelength fibre interferometer with wavelength selection via fibre Bragg grating elements

The use of intra-core fibre gratings to provide the selection of two stable, closely spaced wavelength-components at the output of a fibre interferometer is reported. An unambiguous sensing range in the optical path difference of an interferometer of +or-0.49 mm is demonstrated using two gratings spaced by 2.5 nm.<>