Yoshiaki Miyajima

Upconversion pumped thulium-doped fluoride fiber amplifier and laser operating at 1.47 /spl mu/m

A 1.064-/spl mu/m band upconversion pumped Tm/sup 3+/-doped fluoride fiber amplifier and a laser both operating at 1.47 /spl mu/m are investigated in detail. The two devices are based on the /sup 3/F/sub 4//spl rarr//sup 3/H/sub 4/ transition in a trivalent thulium ion, which is a self-terminating system. When pumped at 1.064 /spl mu/m, the amplifier has a gain of over 10 dB from 1.44 to 1.51 /spl mu/m and a low-noise characteristic. Also, the fiber laser generates a high-output power of over 100 mW with a slope efficiency of 59% at around 1.47 /spl mu/m. These levels of performance will be important for optical communication systems. >

A new design for dispersion-shifted fiber with an effective core area larger than 100 /spl mu/m/sup 2/ and good bending characteristics

Summary form only given. We have designed a new dispersion-shifted large effective-area fiber. We have fabricated a sample fiber with an A/sub eff/ of 146 /spl mu/m/sup 2/, which is almost three times as large as that of standard DSF without any deterioration in the bending loss.

An In-Line Optical Bandpass Filter with Fiber Gratings and an Optical Circulator and Its Application to Pulse Compression

In-line optical bandpass filters having sharp spectral edges are demonstrated for the first time by combining an optical circulator and fiber gratings. The maximum transmission including the optical circulator is 65%. A spectral windowing technique using the filter enabled a picosecond pulse from a gain-switched DFB LD to be shortened from 35 ps to 28 ps.

Optical amplification in Er/sup 3+/-doped single-mode fluoride fiber

The amplification characteristics at around 1.5 mu m of a 0.9-m-long, 1000-p.p.m Er/sup 3+/-doped single-mode fluoride fiber are discussed. By using 1.48- mu m laser diodes with 55-mW launched output as a pump source, a gain of 1.75 dB was obtained at 1.530 mu m. A broad bandwidth of 40 nm was obtained, which may be suitable for wavelength-division multiplexing (WDM) system use.<<ETX>>

Wide Band Erbium-Doped Fluoride Fiber Optical Amplifier at 2.7 µm with Fluoride Fiber Wavelength-Division Multiplex Coupler

A 2.7 µm band optical amplifier composed of an erbium doped fluoride fiber and a low loss fluoride fiber wavelength-division multiplex (WDM) coupler is reported. A maximium gain of 35.9 dB was obtained. An optical gain of more than 20 dB was obtained over a 90 nm wavelength range from 2.72 to 2.81 µm with a pump of 200 mW at 0.647 µm. The saturation output signal power was -2 dBm, and was independent of the pump power.

Gain and output-saturation limit evaluation in Pr/sup 3+/-doped fluoride fiber amplifier operating in the 1.3 mu m band

The optical amplification characteristics in a Pr/sup 3+/-doped fluoride fiber have been demonstrated. The amplification band in a Pr/sup 3+/-doped fluoride fiber fully covers the 1.3 mu m telecommunication window, and a practical optical gain value of over 13 dB was obtained. Moreover, a saturation power of +9 dBm was attained. If the problems of pumping efficiency and wavelength are solved, Pr/sup 3+/-doped fluoride fiber will become available for 1.3 mu m booster amplifiers.<<ETX>>

Viscosity-matched P/sub 2/O/sub 5/-SiO/sub 2/ core single-mode fiber

In conclusion, we have reduced the imperfection loss of an optical fiber with a P/sub 2/O/sub 5/-SiO/sub 2/ core and F-SIO/sub 2/ cladding by viscosity-matching the glasses at the interface between the core and cladding. We achieved a Rayleigh scattering coefficient as small as 0.67 dB/km /spl mu/m/sup 4/. The optical loss at 1.55 /spl mu/m is 0.20 dB/km and the optical loss at wavelengths shorter than 1.3 /spl mu/m is to our knowledge the lowest so far reported.

A highly efficient 1.9 µm Tm-doped fluoride fiber laser and amplifier pumped at 1.58 µm

Laser oscillations using Tm-doped fluoride fiber at 0.8,1.47,1.9 and 2.3 pm have been reported[1-4]. In these lasers, Tm ions are excited to the 3F4 level with 0.79 µm[l-3] or 0.676 µm[4] pump light. The branching ratios to the 0.8, 1.47 and 2.3 µm transitions from the 3F4 level are 0.893, 0.083 and 0.024, respectively[5]. Although the branching ratio of the 0.8 µm transition is much larger than the others, 1.9, 1.47 and 2.3 µm laser oscillations are possible by incorporating a dichroic mirror in the laser cavity and suppressing 0.8 µm laser oscillation.

1.47 µm Tm-doped fluoride fiber amplifier and fiber laser using a 1.064 µm upconversion pumping scheme

Optical fiber amplifiers operating at 1.5 µm (Erbium doped fiber) and 1.3 µm(Neodymium or Praseodymium doped fluoride fiber) are now being studied very actively because they play important roles in optical communication systems. Although a 1.4 µm band optical fiber amplifier has yet to be studied, it is of great interest because a 1.4 µm band transmission system would be useful in transmission line monitoring systems. We have successfully demonstrated an upconversion pumped Tm-doped fiber amplifier and laser operating at 1.47 µm[1],[2].

Nd3+-DOPED FLUORO-ZIRCONATE FIBER AMPLIFIER OPERATED AROUND 1.3 µm

Recently, increasing effort has been made to explore the potential of Er-doped optical fiber amplifiers[1] which are very attractive in the field of 1.5 μm optical fiber telecommunication systems. However, there has been no report on fiber amplifiers for the conventional 1.3 μm telecommunications systems even though many 1.3 μm systems have already been installed.