M.C. Brierley

Exposed-core single-mode-fiber channel-dropping filter using a high-index overlay waveguide

Using the coupling between a standard single-mode fiber and single higher-order modes in a high-index overlay waveguide, we demonstrate a wavelength-filtering device with a channel-dropping response. Two types of filter are described. One uses a thin overlay waveguide, giving a single tunable dropped band response in the 1.2-1.6-microm wavelength region with rejection greater than 20 dB and an insertion loss of about 0.5 dB. The other uses a thick overlay waveguide and gives a comb-filter response with a dropped channel spacing of 13 nm with 20-dB rejection and an insertion loss of between 1 and 4 dB.

Transversely coupled fiber Fabry-Perot resonators: performance characteristics

The experimentally determined performance characteristics of the transversely coupled fiber Fabry-Perot (TCFFP) resonator are discussed. The frequency variation for two important input-output configurations agrees well with theory. Both channel passing and channel dropping outputs are demonstrated. We examine the variation of finesse and visibility with the coupling ratio. The visibility, as defined, is a measure of the filtering efficiency on-resonance. We show that with high quality optical components it is possible to obtain good finesse and visibility simultaneously. The TCFFP resonator, therefore, has potential application to demultiplexing and spectral analysis and as a resonant cavity for fiber lasers.

Single transverse mode operation at 1345 nm wavelength of a diode-laser pumped neodymium:ZBLAN multimode fiber laser

A diode-laser pumped multitransverse-mode neodymium-doped fluoride fiber laser is shown to oscillate in the lowest-order transverse mode when the cavity conditions are optimized. The combination of good pump coupling efficiency, laser operating efficiency, and good overlap of the HE/sub 11/ mode to that of a single-mode fiber, allows up to 12 mW of continuous wave (CW) power to be coupled into a standard single-mode fiber at a 1345-nm wavelength. Improved lens design should significantly increase the power injected into the single-mode fiber from the multimode fiber laser.<<ETX>>

Noise characterization of a neodymium-doped fluoride fiber amplifier and its performance in a 2.4 Gb/s system

An analysis of noise in a neodymium-doped single-mode fluoride fiber amplifier for the 1300-nm telecommunications window has been carried out both theoretically and experimentally. The presence of signal-excited state absorptions, particularly at the shorter wavelength end of the gain transition, has been shown to increase the noise figure and, hence, degrade the overall system performance. However, when the amplifier was used as a power amplifier in a 2.4-Gb/s laboratory system experiment, no degradation at a BER of 10/sup -9/ could be observed.<<ETX>>

Progress in fluoride fiber lasers and amplifiers

The initial predictions that fluoride glasses would find important applications as laser host materials are now becoming fulfilled. Their attraction lay in their low non-radiative decay rates, a result of their lower fundamental phonon energies (also making them transparent out to 5.0um). These low non-radiative rates promised higher efficiencies for many lasing transitions, but also the possibility of new transitions not feasible in other glass compositions. In the last three years, since the initial announcement of the first fluoride fibre laser, the field has mushroomed and to date fibrelaser operation has now been demonstrated on 20 differenttransitions ranging from 0.455 um in the blue to 2.9 um in the mid-JR. Moreover fibre optical amplifiers based on monomode fibre have also now been demonstrated and useful gains observed at 1.34, 1.54 and 2.7 um. Clearly fluoride glasses now provide an interesting alternative to silica based systems for rare-earth (lanthanide) doped fibres, and the first commercial devices are not far away.

Rare-earth-doped fluoride fibers for optical amplification (Invited Paper)

Rare earth-doped fluorozirconate fibres show potential as optical amplifiers from the visible to the mid IR. This paper reviews the current status of their application in telecommunications, concentrating on Tm and Er-dopants for the 1st window and Nd and Pr-dopants for the 2nd window. A 1300 nm system operating at 2.5 Gbits/s using a Pr-doped fibre amplifier is described.

Single Longitudinal Mode Output from a Fox-Smith Erbium Fibre Laser

Erbium fibre lasers can demonstrate low-threshold power lasing at around 1.55 μm with a tuning range exceeding 50 nm in the important low loss telecommunications window1.