Optical amplification at 0.54 /spl mu/m by Er/sup 3+/-doped fluoride fibre

Demonstrated is a 16.5 dB all-fibre optical amplifier at 546 nm using Er³⁺-doped fluoride fibre for a signal power of -30 dBm by forward upconversion pumping of a 974 nm laser diode. Results show Er ³⁺-doped fluoride fibre is a promising candidate for 0.54 mum optical amplifiers     

Temperature insensitive Er/sup 3+/-doped optical fibre amplifiers

Temperature dependence of the gain at 1.536 mu m in Er/sup 3+/-doped fibre are reported for 0.98 and 1.48 mu m pumping. The fibre lengths at which gain is temperature insensitive are found for both pump wavelengths. The temperature insensitive gain characteristics for 0.98 mu m and 1.48 mu m pumping are demonstrated to fibres tuned to their temperature insensitive lengths.<>     

16-channel optical FDM distribution/transmission experiment utilising Er/sup 3+/-doped fibre amplifier

A 16-channel optical FDM distribution/transmission experiment at around 1534 nm wavelength is demonstrated utilising an Er/sup 3+/-doped fibre amplifier. 16 intensity-modulated optical signals at 622 Mbit/s were amplified simultaneously at a gain of 15.2-18.5 dB. One of the amplified signals is selected using the waveguide frequency selection switch and directly detected with a receiver sensitivity of -38 dBm (P/sub e/=10/sup -9/).<>     

Multichannel crosstalk and pump noise characterisation of Er/sup 3+/-doped fibre amplifier pumped at 980 nm

It is shown that as a consequence of the long fluorescence lifetime in an Er/sup 3+/-doped fibre amplifier, interchannel crosstalk and pump-noise breakthrough are minimal for modulation frequencies >100 kHz.<>     

Laser diode pumped Pr/sup 3+/-doped and Pr/sup 3+/-Yb/sup 3+/-codoped fluoride fiber amplifiers operating at 1.3 mu m

Both Pr/sup 3+/-doped and Pr/sup 3+/-Yb/sup 3+/-codoped singlemode fibres with high numerical apertures are pumped by laser diodes with InGaAs/GaAs strained quantum well structures. A net gain of 5.2 dB is obtained from Pr/sup 3+/-doped fluoride fibre pumped by laser diodes operating at 1.1017 mu m and a net gain of 3.2 dB is obtained from Pr/sup 3+/-Yb/sup 3+/-codoped fibre pumped by laser diodes operating at 0.98 mu m. The pumping efficiency difference between Pr/sup 3+/-doped and Pr/sup 3+/-Yb/sup 3+/-codoped fibre is discussed.<>     

980 nm band pumped Er/sup 3+/-doped tellurite-based fibre amplifier with low-noise figure of less than 4.5 dB

The amplification characteristics of an Er/sup 3+/-doped tellurite-based fibre amplifier (EDTFA) with 980 nm band pumping are described. The optimum pump wavelength and length of the newly developed EDTF are investigated in order to obtain both a low noise figure and a high gain simultaneously. We realise a low noise figure of less than 4.5 dB with a pump wavelength of 976.5 nm and a 0.4 m EDTF.     

Ultrahigh-sensitivity low coherence OTDR using Er/sup 3+/-doped high-power superfluorescent fibre source

The first-known demonstration of an Er/sup 3+/-doped superfluorescent fibre source coupled to a high-resolution OTDR based on low coherence interference (low coherence OTDR) is reported. Linearly-polarised light with 14 mW output from the source achieves a -146 dB minimum detectable reflectivity at 3 Hz bandwidth. The spatial resolution determined by spectral FWHM is 28 mu m for silica-based waveguides.<>     

Optical amplification at 0.54 /spl mu/m by Tb/sup 3+/-doped fluoride fibre

0.54 mum band amplification using Tb³⁺-doped fluoride fibre is demonstrated. Spectroscopic properties of Tb³⁺-doped fluoride glass are clarified. A gain of 5.3 dB has been obtained in a 1 wt.% Tb³⁺-doped fluoride fibre for a signal power of -30 dBm by forward pumping at a wavelength of 0.488 mum with power of 100 mW     

Tunable Pr/sup 3+/-doped silica-based fibre laser

The tunability of the Pr/sup 3+/-doped silica-based fibre laser has been investigated. A broad tuning range of 86 nm is obtained for the transition /sup 1/D/sub 2/-/sup 3/F/sub 3,4/ in the band centred at 1048 nm. Factors limiting tunability, and effects of host matrix and broadening mechanisms are discussed.<>     

Tunable Nd/sup 3+/-doped fibre ring laser

A novel tunable all-fibre laser using a Nd/sup 3+/-doped single mode fibre ring resonator is reported. End pumped by an argon laser of 514.5 nm wavelength, the laser threshold was 1.45 mw, and a tuning range of 60 nm is obtained.<>     

85 W Tm/sup 3+/-doped silica fibre laser

An 85 W Tm/sup 3+/-doped silica fibre laser is presented. To the best of the authors' knowledge this is the highest output power achieved by pumping with 793 nm. The slope efficiency was 56%, the threshold 11 W and the output wavelength centred at 2.04 /spl mu/m. The high rate of cross relaxation in this laser provided a quantum efficiency of >130%.     

1.65 /spl mu/m-band optical amplification with Er/sup 3+/-doped fluorozirconate fibre using 0.8 /spl mu/m upconversion pumping

In order to expand the available bandwidth for wavelength division multiplexing transmission systems, a 1.65 /spl mu/m-band optical fibre amplifier with Er/sup 3+/-doped fluorozirconate fibre using 0.8 /spl mu/m upconversion pumping has been demonstrated. The positive gain, 3.8 dB, is the first ever achieved by means of (/sup 2/H/sub 11/2/, /sup 4/S/sub 3/2/) /spl rarr/ /sup 4/I/sub 9/2/ stimulated emission transition.     

Diode laser pumped Er/sup 3+/ fibre laser operation between 2.7-2.8 mu m

CW laser operation in the 2.7-2.8 mu m region has been observed in Er/sup 3+/ doped fluorozircoaluminate glass fibres by diode laser pumping at 0.8 mu m. An absorbed threshold power of 10 mW and an output laser power of 2.1 mW with a slope efficiency of 8% were obtained.<>     

Amplification properties of Er/sup 3+/-doped photonic crystal fibers

The amplification properties of different photonic crystal fibers have been studied by means of a full vector finite-element modal formulation combined with a population and propagation rate equation solver. A honeycomb as well as a cobweb photonic crystal fiber have been considered. The consequences of the defect dimension and the dopant radius on the field intensity distribution as well as the overlap integrals have been analyzed. Results demonstrate that a proper photonic crystal fiber design can be usefully exploited in order to obtain active fibers with superior characteristics compared to standard step index ones. In particular, photonic crystal fibers open up the possibility of a gain medium with highly flexible geometric, dispersion, and amplifying characteristics.     

8-mV threshold Er/sup 3+/-doped planar waveguide amplifier

We report on the gain characteristics of a low threshold (8 mW) Er/sup 3+/-doped planar optical waveguide amplifier. Net fiber to fiber gain of 4.5 dB is achieved at a signal wavelength of 1536 nm with 80 mW of 980-nm pump power. This device represents significant progress toward a planar amplifier module pumped by a single laser diode.     

Controlled amplifier modelocked Er/sup 3+/ fibre ring laser

An erbium-doped fibre ring has been actively modelocked with an InGaAsP semiconductor amplifier employed as a modulator. Pulses having durations <4ps and peak powers of approximately 2 W around 1536 nm have been generated at a repetition frequency of 612 MHz by this new technique of controlled-amplifier modelocking (CAM).<>     

High-power broadly tunable Ho/sup 3+/-doped silica fibre laser

Tuning of the 2.1 /spl mu/m Ho/sup 3+/-doped silica fibre laser is demonstrated for the first time. The /sup 5/I/sub 7//spl rarr//sup 5/I/sub 8/ transition provides tuning over 144 nm, from 2019 to 2163 nm, and a maximum pump-limited output power of 1.58 W at 2100 nm was produced.     

Noise characteristics of Pr/sup 3+/-doped fluoride fibre amplifier

The noise characteristics of a Pr/sup 3+/-doped fluoride fibre amplifier (PDFFA) are reported for the first time. Using an amplifier with a 20 dB gain, a noise figure of 3.2 dB is obtained at a wavelength of 1.31 mu m at an amplified output signal power between -18 and -2 dBm. However, it is observed that the noise figure increases when the signal wavelength is above 1.32 mu m.<>     

Mutual signal gain saturation in Er/sup 3+/-doped fibre amplifier around 1.54 mu m wavelength

Signal gain saturation characteristics of a 1.48 mu m wavelength laser diode pumped Er/sup 3+/-doped fibre amplifier are experimentally investigated for two signal channels amplified around the gain peak wavelengths of 1.535 mu m and 1.551 mu m. The degree of gain saturation is uniquely determined by the total output power when the signal wavelengths are closely positioned. This feature is not suited to two-channel amplification for widely spaced wavelengths.<>     

High-power 0.98 mu m GaInAs strained quantum well lasers for Er/sup 3+/-doped fibre amplifier

High-power GaInAs strained quantum well lasers with an emission wavelength of 0.98 mu m, suitable for Er/sup 3+/-doped fibre amplifier pumping, have been fabricated. A threshold current of 15 mA and a peak output power as high as 85 mW have been obtained for the ridge waveguide structure with AR/HR facet coating. Highly efficient pumping for the 1.536 mu m signals has been confirmed.<>