Pauli Kiiveri

Very short Er-doped silica glass fiber for L-band amplifiers

We measured 44 dB gain using 12 m of highly Er-doped L-band silica fiber and 235 mW total pump power. Also QCE of 45% and NF <3.5 dB were demonstrated. The 3 dB bandwidth was 40 nm and average PMD was 1.5 fs/m.

Spectral gain and noise measurement system for fiber amplifiers

We introduce a new technique to measure the amplified spontaneous emission and signal gain of the fiber amplifier. We have constructed a measurement system that consists of a tunable signal source, a fast chopper, detectors, and a microcomputer. This amplifier measurement system can be used to characterize amplifier properties as a function of input signal wavelength and power.

New capillary optical fiber structure for fluorescence sensors

A multilayer capillary fiber was designed for optical sensor applications and its optical properties were evaluated by using a fluorescent layer immobilized on its inner surface. This fiber structure combines a large interaction surface (the inner wall of the capillary fiber) for binding of fluorescent indicators with evanescent wave fluorescence measurement, which may facilitate the design of pseudohomogeneous assays without separation of the bound from nonbound fluorescent indicator. The inner surface of the capillary was derivatized by aminosilanization, followed by biotinylation and addition of streptavidin. This biotin- streptavidin coating facilities subsequent immobilization of any biotinylated species (e.g. antibodies, antigens, etc.) participating in specific molecular recognition. We have evaluated some properties of this capillary fiber design by using fluorescent proteins immobilized on the inner wall of capillary by biotin-avidin-interaction. Fluorescence was excited by a HeNe-laser (fluorescent indicator APC; (lambda) em equals 660 nm) and by a Ar-laser (fluorescent indicator RPE, (lambda) em equals 578 nm), and measured with a spectrum analyzer.

Comparison of gain dependence of different Er-doped fiber structures

The dependence of gain in Erdoped fibre on Vvalue refractive index dip confinement of Er atoms and diffusion at the core cladding interface is presented. The absorption of the pump light and the gain of the signal light are calculated by solving the population density equations as a function of radial and axial position in the fibre. When the pump wavelength is 980 nm the optimum Vvalue at signal wavelength 1530 nm of a step index fibre increases from 1. 16 to 1. 29 with the pump power increasing from 2 mW to 8 mW. When the pump wavelength is 1490 nm the optimum Vvalue is 1. 37 without pump power dependence. With the confinement of the dopant atoms the gain can be improved as much as 68 . The confinement increases the optimum Vvalue to around 1 . 44. The gain is decreased 37 by an index dip which is 75 of the core diameter and 100 of the index difference. The diffusion of the dopants at the interface between the core and the cladding decreases the calculated gain 17 when the core radius increases 40 due to the diffusion measured at 10 index difference level.