Michael Nickolaos Zervas

Erbium-doped fiber amplifier with 54 dB gain and 3.1 dB noise figures

It is shown that for practical pump powers (<100 mW) a combination of high gain (>33 dB) and low noise figure (3 dB) cannot simultaneously be achieved with a conventional codirectionally pumped EDFA. However, using a codirectionally pumped composite EDFA incorporating an isolator overcomes the problem, and an amplifier with 51 dB (54 dB) gain and 3.1 dB noise figure (NF) for only 45 mW (93 mW) of pump power is demonstrated.<<ETX>>

40GHz pulse train generation at 1.5µm by using a chirped fiber grating as frequency multiplier

Pulse-train multiplication based on the temporal Talbot effect in a linearly chirped fiber Bragg grating has been experimentally demonstrated. A 40-GHz repetition-rate, nearly transform-limited 10-ps duration optical pulse train at 1.533 mum has been obtained from a 2.5-GHz mode-locked Er- Yb:glass laser by use of a 100-cm-long linearly chirped apodized fiber grating.

Acoustooptic attenuation filters based on tapered optical fibers

This paper studies the acoustooptic interaction induced by an acoustic flexural wave among the optical propagation modes supported by tapered optical fibers. We have investigated the evolution of the acoustooptic resonance condition as the fiber is progressively tapered, showing that the taper radius can be regarded as a new degree of freedom in the design of acoustooptic filters. Finally, we demonstrate a novel acoustooptic filter based on nonuniform tapers for dynamic gain flattening of optical fiber amplifiers.

Rayleigh scattering effect on the gain efficiency and noise of erbium-doped fiber amplifiers

The effect of the internal Rayleigh scattering on the gain efficiency and noise of the erbium-doped fiber amplifier has been considered in detail. It is shown that excess background loss due to Rayleigh scattering at the signal and pump wavelengths dramatically reduces the optimum gain efficiency of either high NA, low-concentration or confined-dopant erbium-doped fibers. Distributed feedback due to Rayleigh backscattering, on the other hand, degrades the noise performance of high gain amplifiers considerably. In applications where high gain and low noise figure are required, increasing the fiber NA and dopant confinement above an optimum value are shown to increase the required pump power dramatically due to the deleterious effects of Rayleigh backscattering. >

Efficient erbium-doped fiber amplifiers incorporating an optical isolator

A composite-EDFA configuration which incorporates an optical isolator has been investigated theoretically and experimentally. The isolator prevents the build-up of the backward-ASE and results in an amplifier with high gain and near-quantum-limited noise figure (NF). The optimum position of the isolator has been calculated as a function of the pump power so that minimum NF and maximum gain are achieved simultaneously. It is shown that under practical pump powers, the optimized composite EDFA exhibits a gain improvement of about 5 dB and a NF reduction in excess of 1.5 dB when compared with an optimized conventional EDFA. It is also shown that with further optimization the composite EDFA can be employed in a practical fiber link as a pre-amplifier without the use of an input isolator. Finally, a high-gain composite EDFA has been experimentally demonstrated which exhibits a gain of 51 dB (54 dB) and NF of 3.1 dB for only 435 mW (93 mW) of pump power. >

Relief gratings on Er/Yb-doped borosilicate glasses and waveguides by excimer laser ablation

Relief gratings have been fabricated on Er/Yb-doped borosilicate glass substrates by laser ablation using a 193 nm excimer laser and a modified Mach-Zehnder interferometer. The grating fabrication process was quantified using diffraction efficiency measurements and related to the incident energy density. Diffraction efficiencies and grating profiles are presented for gratings fabricated using different pulse energy densities and number of pulses, and optimised fabrication conditions are proposed. Finally, relief gratings were applied to ion-exchanged channel waveguides and spectral transmission measurements are presented.

Erbium-doped-fiber optical limiting amplifiers

A novel configuration of an erbium-doped-fiber optical output-limiting amplifier (OLA) is presented which is realized by simply introducing a differential lump-loss between the signal and the pump power at a particular point along the fiber. The OLA exhibits an input-power dynamic range in excess of 40 dB and the capacity to control optically the level of the constant-output signal. >

Design and fabrication of high gain-efficiency erbium-doped fiber amplifiers

The gain efficiency of a fully optimized erbium-doped fiber amplifier (EDFA) is calculated as a function of the fiber numerical aperture and dopant confinement in the core and is shown to agree well with experimental data. A gain efficiency of 8.9 dB/mW is demonstrated. This is the best reported value to date for modified chemical vapor deposition (MCVD) fibers. In addition, the detrimental effect of pump and signal background losses on the optimal gain efficiency is considered in detail.<<ETX>>

Characteristics of chirped fiber gratings for dispersion compensation

Summary form only given. Chirped fiber Bragg gratings have recently received considerable attention due to their immense potential for use as dispersion equalizers in long-haul fiber telecom links. Some of their properties have been studied theoretically and demonstrated in a number of system trials. We have implemented a variable-chirp grating using the temperature gradient technique and systematically measured its reflection and dispersion characteristics for a wide range of applied chirp.

Efficient erbium-doped fibre amplifier with an integral isolator

A composite erbium-doped fibre amplifier configuration is presented which incorporates an isolator within the length to suppress the backward amplified spontaneous emission. The configuration shows increased gain efficiency accompanied by quantum-limited noise performance.