Kiyoshi Oikawa

Gain characteristics of tellurite-based erbium-doped fiber amplifiers for 1.5-µm broadband amplification

The signal-gain characteristics of tellurite-based erbium-doped fiber amplifiers are clarified based on spectroscopic properties and signal-gain measurements. The potential of tellurite-based erbium-doped fiber for use as a broadband light source is also described.

Fluoride-based erbium-doped fiber amplifier with inherently flat gain spectrum

We successfully developed a fluoride-based Er/sup 3+/-doped fiber amplifier (F-EDFA). An average signal gain of 26 dB was achieved for 8 channel wavelength division multiplexed (WDM) signals in the 1532-1560 nm wavelength region with a gain excursion of less than 1.5 dB at an input signal power of -20 dBm per channel. Furthermore, we studied the amplification characteristics of the F-EDFA for WDM signals. The following experimental results were obtained. (1) For an 8-channel WDM signal in the 1532 to 1560 nm wavelength region, the gain excursion between channels can be suppressed to within 1.5 dB. However, the wavelength region allowing a gain excursion of 1.5 dB, is between 1536-1560 nm for the silica-based Er/sup 3+/-doped fiber amplifier. (2) F-EDFAs have a flat gain region between 1534-1542 nm. The gain excursion of this region is less than 0.2 dB for WDM signals.

1.58-/spl mu/m broad-band erbium-doped tellurite fiber amplifier

This paper describes the development of a 1.58-/spl mu/m broad-band and gain-flattened erbium-doped tellurite fiber amplifier (EDTFA). First, we compare the spectroscopic properties of various glasses including the stimulated emission cross sections of the Er/sup 3+4/ I/sub 13/2/ /sup 4/I/sub 15/2/ transition and the signal excited-state absorption (ESA) cross sections of the Er/sup 3+4/ I/sub 13/2/ - /sup 4/I/sub 9/2/ transition. We detail the amplification characteristics of a 1.58-/spl mu/m-band EDTFA designed for wavelength-division-multiplexing applications by comparing it with a 1.58-/spl mu/m-band erbium-doped silica fiber amplifier. Furthermore, we describe the 1.58-/spl mu/m-band gain-flattened EDTFA we developed using a fiber-Bragg-grating-type gain equalizer. We achieved a gain of 25.3 dB and a noise figure of less than 6 dB with a slight gain excursion of 0.6 dB over a wide wavelength range of 1561-1611 nm. The total output power of the EDTFA module was 20.4 dBm and its power conversion efficiency reached 32.8%.

Low-noise and high-power Pr/sup 3+/-doped fluoride fiber amplifier

We have successfully developed a low-noise and high-power Pr/sup 3+/-doped fluoride amplifier (PDFA) module with a cascade configuration. The maximum signal gain and noise figure were 40.6 dB and 5 dB, respectively. An output power of 20.1 dBm was achieved at an input signal power of 0 dBm. We confirm that this PDFA module performs well from experimental results on its use in a 40 channel AM-VSB video signal transmission and a 10 Gbit/s digital transmission.<<ETX>>

BaF2-CaF2-YF3-AlF3 Glass Systems for Infrared Transmission

Transparent and colorless glass rods have been obtained from the BaF2-CaF2-YF3-AlF3 system, which consists of 15 to 27 mol% BaF2, 13 to 25 mol% CaF2, 6 to 28 mol% YF3 and 37 to 50 mol% AlF3. Certain physical properties for the rods have been measured. Glass transition temperature, crystallization temperature, melting temperature and thermal expansion coefficient for 22BaF2-22CaF2-16YF3-40AlF3 glass are determined as 430°C, 535°C, 710°C and 16.5×10-6/°C for 300–400°C, respectively. The glass is transparent at 0.23–5.2 µm wavelengths, and shows a refractive index (nD) of about 1.44, density of about 4.0 g/cm3, Knoop hardness of about 360 kg/mm2, and water solubility of about 0.005 g per 100 g cold water. These glass rods have been able to be drawn into trial fibers of a few meters in length.

Transmission Loss Characteristics of a Fluoride Optical Fiber in the Near-Ultraviolet to Mid-Infrared Wavelength Region

A fluoride optical fiber with low impurity and defect content has been fabricated using high-purity raw materials and a dry fluorination method. The 160-meter-long fabricated fiber shows a minimum transmission loss of 1.2 dB/km at a 2.30-µm wavelength and transmission losses of less than 10 dB/km in the 0.8–2.7 µm wavelength region. It seems that the transmission loss in the 0.3–0.4 µm wavelength region is dominantly due to Rayleigh scattering, and that a weak absorption tail with lower loss than that in pure silica glasses is the second major loss factor in this region.

Er 3+ -doped fluorophosphate glass fiber with ultra low nonlinearity for suppressing four-wave-mixing in L-band EDFA

We developed Er3+-doped fluorophosphate glass fiber with low nonlinearity. With an L-band EDFA employing the fiber the four-wave-mixing crosstalk was 10 dB less than when employing an Er3+-doped silica fiber with low nonlinearity.