A Polarization Controlled Switchable Multiwavelength Erbium-Doped Fibre Laser

A polarization controlled switchable multiwavelength erbium-doped fibre laser with overlapping cavities is proposed. The wavelengths are specified by two Bragg gratings in polarization-maintaining PANDA fibre. The proposed laser can be designed to be operated in stable four-wavelength or wavelength switching modes only by     

Tunable Yb-Doped Double-Clad Fibre Laser Based on Fibre Bragg Grating with Narrow Linewidth

A tunable Yb-doped double-clad fibre (YDCF) laser by tuning the fibre Bragg grating (FBG) is successfully demonstrated. The FBG was fabricated in the YDCF directly, resulting in low splicing loss and compact configuration. A continuous tuning range of 15.6nm from 1046.6nm to 1062.2nm is achieved. The laser linewidth is smaller than 0.1 nm in the whole tuning range. A maximum output power 117mW is achieved when the pump power is332 mW. The laser oscillation is quite stable in the whole operation.     

Phase-Locked Fibre Array for Coherent Combination and Atmosphere Aberration Compensation

We report a fibre amplifier array that not only achieves coherent beam combination by compensation of phase noises of fibre amplifier, but also accomplishes correction of atmosphere aberration. It is of master-oscillatormultiple-amplifier （MOPA） configuration, which can be phase-locked by the multidither principle or heterodyne detection principle. First laboratory experiments of atmosphere aberration compensation of a three-element fibre amplifier array are reported. The atmosphere aberration is created by a phase screen in the experiment. The phase changes of the beam, which are introduced by the fibre amplifier and the phase screen, are both detected by the heterodyne detection method. Phase modulators are controlled to compensate for the phase in the three paths. No matter whether there is a phase screen producing atmosphere aberration or not, the dim dynamic interference fringes in the far field turn to a clear and stable pattern, and the peak intensity is maximized. It is indicated that the fibre amplifier array is phase-locked, and coherent combination of the three beams is achieved. It can be used not only to obtain high power fibre laser array but also in laser space communication.     

A New Method for Filter Design Based on Long-Period Fibre Grating

We present a simple method to induce mechanically a long-period fibre grating in a general sing mode fibre.The transmission spectrum of the new type of grating can be tailored by changing the external applied pressure or by introducing a phase-shift in the grating.The tunability this kind of gratings exhibit will be particularly useful for the filter design.     

Single Mode Er-Doped π-Phase-Shifted Distributed Feedback Fibre Grating Laser

A novel method incorporating the shielded method and the post-processing method has been proposed to fabricate the π-phase-shifted fibre grating. Then an Er-doped π-phase-shifted distributed feedback fibre grating laser has been fabricated using the grating. The laser threshold is 20mW. When pumped with 90mW light at 980nm, the laser gives an output of 1.1mW. Its signal-to-noise ratio is better than 60dB. It is demonstrated that the laser is single mode operation by means of a Fabry--Perot scanning interferometer.     

Chaotic Oscillator in Frequency by Using Tunable Laser with Fibre Bragg Grating

A novel chaotic oscillator in wavelength domain by using a tunable fibre laser is proposed. The generator of chaos in wavelength is composed of fibre Bragg grating （FBG） with hybrid delayed feedback loop which induces wavelength nonlinearity. The dynamical regime of wavelength is ruled by a differential difference equation. We give the numerical simulation of the experimental setup and discuss its application in an optical encryption system.     

An Experimental Study of Ultrashort Pulsed Ytterbium-Doped Fibre Laser and Amplifier

We report the generation of ultrashort pulses in ytterbium-doped fibre oscillator emitting around 1.05μm at a repetition rate of 17.6 MHz. A diode laser with single silica fibre at 976nm pumps the ytterbium fibre laser, the all-fibre picosecond pulsed oscillator has excellent stability and compact size, and freedom from misalignment. After amplifying, pulse energy of 3.4 nJ and an average power of 60 m W are obtained. The compression is obtained with a grating pair out of the cavity. The compressor produces 307fs with the peak power 5.47kW. A practical fibre-based source with good performance is thus demonstrated.     

Photoelectric Hybrid Optical Bistable Device Using Fibre Bragg Gratings with Two Feed Signals

A photoelectric hybrid optical bistable device (OBD) is investigated by using fibre Bragg gratings as a lightintensity modulator. A new operation with two feed signals is proposed, and with this method the output characteristic of the OBD is remarkably improved. The potential application of such a device in optic stabilizer for fibre laser is also briefly discussed.     

Blue Up-Conversion Fibre Laser Pumped by a ll20-nm Raman Fibre Laser

A Tm^3 -doped ZrF4-BaF2-LaF3 AlF3-NaF (ZBLAN) fibre up-conversion laser pumped by a 1120-nm Raman fibre laser is demonstrated with blue output power levels up to 116mW. For the output mirror with 80^ reflectivity, the slope efficiency is about 15%, the optical-to-optical conversion efficiency is 11%, and the maximum un-saturated output power is 116mW. For 60% reflectivity, the slope efficiency is about 18% and the opticalto-optical conversion efficiency is 12%, whilst the maximum saturated output power is about 80roW due to the existence of photo-degradation effect in Tm^3 doped ZBLAN glass fibre.     

Temperature-Insensitive Chemical Sensor with Twin Bragg Gratings in an Optical Fibre

To reduce temperature sensitivity of the fibre Bragg grating （FBG） chemical sensor, a simple method is proposed by measuring the peak wavelength difference between an etched FBG and an un-etched one in an optical fibre. Thermal characteristics and chemical sensitivity of the sensor are experimentally investigated. The experimental results indicate that the etched FBG and the rest one have almost the same thermal response, and concentration changes of the surrounding chemical solutions can be detected by measuring the peak wavelength difference between them. The sensor has been used to measure the concentrations of propylene glycol solutions and sugar solutions, and it could detect 0.7% and 0.45% concentration changes for them with an optical spectrum analyser in resolution of 10pm.